Details of the Researcher

PHOTO

Keisuke Kasai
Section
Research Institute of Electrical Communication
Job title
Associate Professor
Degree

  • 博士（工学）（東北大学）

  • 修士（工学）（東北大学）

Research History 6

  • 2019/08 - Present
    Tohoku University　Research Institute of Electrical Communication　Associate Professor

  • 2012/11 - 2019/07
    東北大学電気通信研究所　助教

  • 2012/04 - 2012/10
    東北大学電気通信研究所　教育研究支援者

  • 2009/04 - 2012/03
    東北大学電気通信研究所　日本学術振興会 特別研究員(PD)

  • 2008/04 - 2009/03
    東北大学大学院工学研究科　COEフェロー

  • 1999/04 - 2002/03
    日立電線株式会社

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Education 2

  • Tohoku University　Graduate School, Division of Engineering　電気・通信工学

    - 2008/03

  • Tohoku University　Faculty of Engineering

    - 1999/03/25

Committee Memberships 15

  • 電子情報通信学会　東北支部 支部委員

    2024/06 - Present

  • The European Conference on Optical Communications (ECOC)　Technical Programme Committee (TPC)

    2024/01 - Present

  • International Conference on Emerging Technologies for Communications　Technical Programme Committee (TPC)

    2023/05 - Present

  • 電子情報通信学会　Communications Express編集委員会 編集委員

    2022/06 - Present

  • 電子情報通信学会　光通信システム研究専門委員会 委員

    2020/06 - Present

  • レーザー学会, ファイバーレーザー技術専門委員会　専門委員

    2012/04 - Present

  • 電子情報通信学会　エレクトロニクスソサイエティ 技術渉外幹事

    2022/06 - 2024/06

  • 電子情報通信学会　東北支部 会計幹事

    2022/06 - 2024/06

  • 電子情報通信学会　レーザ・量子エレクトロニクス研究専門委員会 委員

    2018/06 - 2024/06

  • 電子情報通信学会　代議員会 代議員

    2023/04 - 2024/03

  • 応用物理学会　東北支部庶務幹事

    2020/04 - 2022/03

  • 電子情報通信学会　会誌編集委員会 委員

    2018/06 - 2020/06

  • レーザー学会　第40回年次大会プログラム委員

    2019/06 - 2020/01

  • 電子情報通信学会　ソサイエティ大会 企画シンポジウムオーガナイザ

    2019/01 - 2019/09

  • 電子情報通信学会　ソサイエティ大会 エレクトロニクスソサイエティ プログラム編成委員

    2018/07 - 2018/09

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Professional Memberships 4

  • IEEE

  • レーザー学会

  • 応用物理学会

  • 電子情報通信学会

Research Interests 3

  • 光・無線通信

  • コヒーレント光通信

  • レーザの周波数・位相制御

Research Areas 1

  • Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Communication and network engineering / レーザ工学, 光通信工学

Awards 9

  1. 研究奨励特別賞（石田實賞）

    2022/12　一般財団法人石田實記念財団　レーザの高精度周波数・位相制御 技術とそのコヒーレント多値光伝送への応用に関する研究

  2. International Conference on Emerging Technologies for Communications (ICETC) 2021, Best Paper Award

    2021/12　The Institute of Electronics, Information and Communication Engineers (IEICE)　Performance comparison between injection-locked carrier frequency conversion and self-heterodyne detection methods in coherently-linked optical and wireless transmission for 6G

  3. 第36回電気通信普及財団賞（テレコムシステム技術賞）

    2021/03　公益財団法人電気通信普及財団　10.16-Peta-B/s Dense SDM/WDM Transmission Over 6-Mode 19-Core Fiber Across the C+L Band

  4. Best Paper Award

    2018/07　Opto-Electronics and Communications Conference　Reverse Phase Modulation Technique for GAWBS Noise Error Floor Elimination in 1024 QAM 160 km Digital Coherent Transmission

  5. 平成23年度電子情報通信学会論文賞

    2012/05　電子情報通信学会

  6. 電子情報通信学会2008年Electronics Express Best Paper Award

    2008/09　電子情報通信学会 エレクトロニクスソサイエティ

  7. 平成19年度東北大学大学院工学研究科長賞

    2008/03　東北大学

  8. IEEE Sendai Section Student Award 2007

    2007/12　IEEE Sendai Section

  9. 2007 Asia-Pacific Microwave Photonics Conference, Best Student Paper Award

    2007/04　Asia-Pacific Microwave Photonics Conference

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Papers 197

  1. Three-Dimensional Quantum Noise Stream Cipher with Time Domain Masking Peer-reviewed

    Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    European Conference on Optical Communication (ECOC) 2024　1-3　2024/09

  2. Fully Coherent Mobile Fronthaul Transmission with a Very Large Loss Budget by Using Injection-Locked Heterodyne Detection Peer-reviewed

    Keisuke Kasai, Koichi Shirahata, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa, Toshiyuki Kobayashi

    European Conference on Optical Communication (ECOC) 2024　1-3　2024/09

  3. New GAWBS Noise Interacting with Longitudinally Propagating Acoustic Waves in Few-mode Fibers Peer-reviewed

    Masato Yoshida, Takaaki Hirai, Shohei Beppu, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    Optical Fiber Communications Conference and Exhibition (OFC) 2024　1-3　2024/03

  4. Demodulation Performance Comparison of High-Speed Coherent Nyquist Pulse Signal with Analog and Digital Demultiplexing Schemes Peer-reviewed

    Masato YOSHIDA, Kosuke KIMURA, Toshihiko HIROOKA, Keisuke KASAI, Masataka NAKAZAWA

    IEICE Transactions on Communications　E106.B　(11)　1059-1064　2023/11/01

    Publisher: Institute of Electrical and Electronics Engineers (IEEE)

    DOI： 10.1587/transcom.2022obp0001 　

    ISSN： 0916-8516

    eISSN： 1745-1345

  5. Efficient Optical-to-sub-THz Carrier Frequency Down-Conversion by UTC-PD-Integrated HEMT Peer-reviewed

    Tsung-Tse Lin, Mitsuki Watanabe, Dai Nagajima, Keisuke Kasai, Masato Yoshida, Tetsuya Suemitsu, Taiichi Otsuj, iAkira Satou

    International Topical Meeting on Microwave Photonics (MWP) 2023　1-4　2023/10

    DOI： 10.1109/MWP58203.2023.10416637 　

  6. Utilizing High-Intensity Optical Subcarrier Signal for Conversion Gain Enhancement of a UTC-PD-Integrated HEMT Photonic Double-Mixer Peer-reviewed

    T.-T. Lin, D. Nakajima, K. Nishimura, M. Watanabe, K. Kasai, M. Yoshida, T. Suemitsu, T. Otsuji, A. Satou

    2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)　2023/09/17

    Publisher: IEEE

    DOI： 10.1109/irmmw-thz57677.2023.10299383 　

  7. Conversion Gain Enhancement of a UTC-PD-Integrated HEMT Photonic Double-Mixer by High-Intensity Optical Subcarrier Signal Peer-reviewed

    D. Nakajima, K. Nishimura, M. Watanabe, T. T. Lin, K. Kasai, M. Yoshida, T. Suemitsu, T. Otsuji, A. Satou

    Optical Fiber Communication Conference (OFC) 2023　2023

    Publisher: Optica Publishing Group

    DOI： 10.1364/ofc.2023.m3d.7 　

    More details Close

    We experimentally investigate the effect of high-intensity subcarrier signal input to the UTC-PD-integrated HEMT working for optical-to-wireless carrier frequency down-conversion on enhancement of its double-mixing conversion gain. The fabricated UTC-PD-integrated HEMT demonstrated the linear increase in the conversion gain by up to +7 dB with increasing the subcarrier signal intensity without saturation, and the conversion gain enhancement of +6.8 dB from -51.0 dB to -44.2 dB was achieved.

  8. 次世代RANの実現に向けたフルコヒーレントアクセスシステム Invited Peer-reviewed

    中沢正隆, 葛西恵介, 吉田真人, 廣岡俊彦

    電子情報通信学会論文誌 C　J105-C　(11)　315-328　2022/11

  9. 48 Gbit/s 256 QAM coherently-linked optical and wireless transmission at 61 GHz band using a small planar antenna for 6G Peer-reviewed

    Koichi Shirahata, Taisei Sato, Keisuke Kasai, Toshihiko Hirooka, Masato Yoshida, Masataka Nakazawa

    nternational Conference on Emerging Technologies for Communications (ICETC) 2022　1-3　2022/11

  10. Experimental and Numerical Analysis of Ultrahigh-Speed Coherent Nyquist Pulse Transmission with Low-Nonlinearity Dispersion Compensator Peer-reviewed

    Kosuke KIMURA, Masato YOSHIDA, Keisuke KASAI, Toshihiko HIROOKA, Masataka NAKAZAWA

    IEICE Transactions on Communications　E105.B　(9)　1014-1022　2022/09/01

    Publisher: Institute of Electronics, Information and Communications Engineers (IEICE)

    DOI： 10.1587/transcom.2021ebp3178 　

    ISSN： 0916-8516

    eISSN： 1745-1345

  11. UTC-PD-Integrated HEMT for Optical-to-MMW/THz Carrier Frequency Down-Conversion: Scaling Rule of Conversion Gain on UTC-PD Mesa Size Peer-reviewed

    D. Nakajima, K. Nishimura, T. Hosotani, K. Kasai, M. Yoshida, T. Suemitsu, T. Otsuji, A. Satou

    2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)　2022/08/28

    Publisher: IEEE

    DOI： 10.1109/irmmw-thz50927.2022.9895988 　

  12. Demodulation Performance Comparison of 160 Gbaud Coherent Nyquist Pulse Signal with Analog and Digital DEMUX Schemes Peer-reviewed

    Masato Yoshida, Kosuke Kimura, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2022 27th OptoElectronics and Communications Conference (OECC) and 2022 International Conference on Photonics in Switching and Computing (PSC)　2022/07/03

    Publisher: IEEE

    DOI： 10.23919/oecc/psc53152.2022.9849876 　

  13. Broadband injection-locked homodyne receiver for digital coherent transmission using a low Q Fabry-Perot LD Peer-reviewed

    Keisuke Kasai, Takashi Kan, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　30　(8)　13345-13355　2022/04

    DOI： 10.1364/OE.456327 　

    ISSN： 1094-4087

  14. Precise Measurements and their Analysis of GAWBS-Induced Depolarization Noise in Multi-Core Fiber for Digital Coherent Transmission Peer-reviewed

    Masato Yoshida, Kozo Sato, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    IEICE TRANSACTIONS ON COMMUNICATIONS　E105B　(2)　151-158　2022/02

    DOI： 10.1587/transcom.2021CEP0006 　

    ISSN： 0916-8516

    eISSN： 1745-1345

  15. GAWBS noise correlation between cores in multi-core fibers Peer-reviewed

    Kozo Sato, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　29　(26)　42523-42537　2021/12

    DOI： 10.1364/OE.442261 　

    ISSN： 1094-4087

  16. Performance comparison between injection-locked carrier frequency conversion and self-heterodyne detection methods in coherently-linked optical and wireless transmission for 6G Peer-reviewed

    Keisuke Kasai, Taisei Sato, Koichi Shirahata, Toshihiko Hirooka, Masato Yoshida, Masataka Nakazawa

    International Conference on Emerging Technologies for Communications (ICETC) 2021　1-3　2021/11

  17. Broadband Dynamic Injection-Locking Performance of Fabry-Perot LD and Its Application to Coherent Homodyne Receiver Peer-reviewed

    Takashi Kan, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    2021 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXPOSITION (OFC)　2021/03

  18. Chromatic dispersion dependence of GAWBS phase noise compensation with pilot tone Peer-reviewed

    Kozo Sato, Takashi Kan, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　29　(7)　10676-10687　2021/03

    DOI： 10.1364/OE.418891 　

    ISSN： 1094-4087

  19. 10 Channel WDM 80 Gbit/s/ch, 256 QAM Bi-Directional Coherent Transmission for a High Capacity Next-Generation Mobile Fronthaul Peer-reviewed

    Masato Yoshida, Takashi Kan, Keisuke Kasai, Toshihiko Hirooka, Katsumi Iwatsuki, Masataka Nakazawa

    JOURNAL OF LIGHTWAVE TECHNOLOGY　39　(5)　1289-1295　2021/03

    DOI： 10.1109/JLT.2020.3034417 　

    ISSN： 0733-8724

    eISSN： 1558-2213

  20. 10 Tbit/s QAM Quantum Noise Stream Cipher Coherent Transmission Over 160 Km Peer-reviewed

    Masato Yoshida, Takashi Kan, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    JOURNAL OF LIGHTWAVE TECHNOLOGY　39　(4)　1056-1063　2021/02

    DOI： 10.1109/JLT.2020.3016693 　

    ISSN： 0733-8724

    eISSN： 1558-2213

  21. 64 Gbit/s, 256 QAM Transmission Through Coherent Optical-Wireless Link at 61 GHz Using Simple and High OSNR Carrier Frequency Converter Peer-reviewed

    Keisuke Kasai, Taisei Sato, Toshihiko Hirooka, Masato Yoshida, Masataka Nakazawa

    2021 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXPOSITION (OFC)　2021

  22. GAWBS Noise Correlation Between Cores in Four-Core Fiber Peer-reviewed

    Kozo Sato, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2021 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXPOSITION (OFC)　2021

  23. Spectrally efficient pilot tone-based compensation of inter-channel cross-phase modulation noise in a WDM coherent transmission using injection locking Peer-reviewed

    Takashi Kan, Kozo Sato, Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    OPTICS EXPRESS　29　(2)　1454-1469　2021/01

    DOI： 10.1364/OE.414381 　

    ISSN： 1094-4087

  24. Injection-locked 256 QAM WDM coherent transmissions in the C- and L-bands Peer-reviewed

    Takashi Kan, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　28　(23)　34665-34676　2020/11

    DOI： 10.1364/OE.404786 　

    ISSN： 1094-4087

  25. Precise measurements and their analysis of GAWBS-induced depolarization noise in various optical fibers for digital coherent transmission Peer-reviewed

    Masato Yoshida, Naoya Takefushi, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　28　(23)　34422-34433　2020/11

    DOI： 10.1364/OE.409326 　

    ISSN： 1094-4087

  26. Digital Coherent Optical Access Technologies for beyond 5G Network Invited Peer-reviewed

    Keisuke Kasai, Masataka Nakazawa, Masato Yoshida, Katsumi Iwatsuki, Toshihiko Hirooka

    2020 IEEE International Symposium on Radio-Frequency Integration Technology, RFIT 2020　145-147　2020/09/01

    Publisher: Institute of Electrical and Electronics Engineers Inc.

    DOI： 10.1109/RFIT49453.2020.9226206 　

  27. 64 Gbit/s, 256 QAM Coherently-Linked Optical and Wireless Transmission in 61 GHz Band Using Novel Injection-Locked Carrier Frequency Converter. Peer-reviewed

    Keisuke Kasai, Toshihiko Hirooka, Masato Yoshida, Masataka Nakazawa

    European Conference on Optical Communications(ECOC)　1-3　2020/09

    Publisher: IEEE

    DOI： 10.1109/ECOC48923.2020.9333340 　

  28. GAWBS phase noise characteristics in multi-core fibers for digital coherent transmission Peer-reviewed

    Naoya Takefushi, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　28　(15)　23012-23022　2020/07

    DOI： 10.1364/OE.399202 　

    ISSN： 1094-4087

  29. Evaluation of Systematic Errors in the Compact Absolute Gravimeter TAG-1 for Network Monitoring of Volcanic Activities Peer-reviewed

    Akito Araya, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa, Tsuneya Tsubokawa

    International Association of Geodesy Symposia　2020/04/29

    Publisher: Springer Berlin Heidelberg

    DOI： 10.1007/1345_2020_107 　

    ISSN： 0939-9585

    eISSN： 2197-9359

    More details Close

    Abstract Volcanic activities sometimes involve gravity changes, and this research is intended to establish an observation network surrounding an active volcano using compact absolute gravimeters. To simplify the configuration of absolute gravimeters, they are preferably operated with a light source distributed from a telecom band (wavelength of 1.5 μm) laser through optical fibers. To evaluate the accuracy of the absolute gravimeter with the telecom band laser, we conducted observations using a prototype gravimeter (TAG-1) with frequency-stabilized lasers at both 1.5 μm and 633 nm, and compared these results with the expected gravity at the site. Initially, both results showed offsets −187 μGal and −9.6 μGal for the 1.5-μm laser and the 633-nm laser, respectively (1 Gal = 10−8 m/s2). By correcting the systematic errors of the photo detectors measured by the synthetic chirp signal, the obtained absolute gravity was consistent with the expected value for both wavelengths; offsets from the expected gravity were reduced to 6.6 μGal and 5.4 μGal for 1.5 μm and 633 nm, respectively. We also evaluated the errors associated with long-distance transmission of the 1.5-μm laser using a reeled optical fiber (26 km) and an optical amplifier and found no degradation in the gravity data from the case of short transmission (10 m). These results allow networking of compact absolute gravimeters connected by telecom optical fibers that are operated using a common laser and expansion to volcanic areas to monitor the gravity change associated with volcanic activities.

  30. 10 GHz, 6.2 ps Transform-Limited Coherent Optical Pulse Generation from a 1.55 μm, Self-Injection Gain-Switched DFB-LD. Peer-reviewed

    Keisuke Kasai, Masataka Nakazawa

    Optical Fiber Communications Conference and Exhibition(OFC)　1-3　2020/03

    Publisher: IEEE

  31. Theoretical and experimental analyses of GAWBS phase noise in various optical fibers for digital coherent transmission Peer-reviewed

    Naoya Takefushi, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　28　(3)　2873-2883　2020/02

    DOI： 10.1364/OE.384505 　

    ISSN： 1094-4087

  32. Low-Nonlinearity, Dispersion-Compensated Transmission Line with a Chirped Fiber Bragg Grating and Its Application to Ultrahigh-Speed Coherent Nyquist Pulse Transmission Peer-reviewed

    Taro Iwaya, Kosuke Kimura, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2020 OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC 2020)　2020

    ISSN： 2166-8884

    eISSN： 2166-8892

  33. Precise and Wideband Compensation of Inter-Channel Cross-Phase Modulation Noise in WDM Coherent Transmission Using Injection Locking Peer-reviewed

    Takashi Kan, Kozo Sato, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2020 OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC 2020)　2020

    ISSN： 2166-8884

    eISSN： 2166-8892

  34. Research Project to Realize Various High-reliability Communications in Advanced 5G Network Peer-reviewed

    Takahide Murakami, Yoji Kishi, Koji Ishibashi, Keisuke Kasai, Hiroyuki Shinbo, Morihiko Tamai, Kensuke Tsuda, Masataka Nakazawa, Yu Tsukamoto, Hiroyuki Yokoyama, Yoshimi Fujii, Yuta Seki, Shinobu Nanba, Takanori Hara, Fumiyuki Adachi, Takayuki Sotoyama

    2020 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC)　2020

    ISSN： 1525-3511

  35. Chromatic Dispersion Dependence of GAWBS Noise Peer-reviewed

    Kozo Sato, Takashi Kan, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2020 OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC 2020)　2020

    ISSN： 2166-8884

    eISSN： 2166-8892

  36. Suppression of large error floor in 1024 QAM digital coherent transmission by compensating for GAWBS phase noise Peer-reviewed

    Masato Yoshida, Naoya Takefushi, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　27　(25)　36691-36698　2019/12

    DOI： 10.1364/OE.27.036691 　

    ISSN： 1094-4087

  37. Single-channel 15.3 Tbit/s, 64 QAM coherent Nyquist pulse transmission over 150 km with a spectral efficiency of 8.3 bit/s/Hz Peer-reviewed

    Masato Yoshida, Kosuke Kimura, Taro Iwaya, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　27　(20)　28952-28967　2019/09

    DOI： 10.1364/OE.27.028952 　

    ISSN： 1094-4087

  38. Real-Time 256 QAM Bi-directional Coherent Transmission in Next Generation Mobile Fronthaul. Peer-reviewed

    Masato Yoshida, Takashi Kan, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC)(OECC/PSC)　1-3　2019/07

    Publisher: IEEE

    DOI： 10.23919/PS.2019.8817867 　

  39. Experimental and theoretical analyses of GAWBS depolarization noise in digital coherent transmission Peer-reviewed

    Naoya Takefushi, Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    IET Conference Publications　2019　(765)　2019

    Publisher: Institution of Engineering and Technology

  40. Demonstration of on-line bi-directional 10-rrhs with an 80 Gbit/s/RRH capacity using 256 QAM WDM coherent transmission for next generation mobile fronthaul Peer-reviewed

    Takashi Kan, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Katsumi Iwatsuki, Masataka Nakazawa

    European Conference on Optical Communications (ECOC) 2019　2019　(765)　2019

    Publisher: Institution of Engineering and Technology

  41. Dual-Polarization On-Line 256 and 512 QAM Digital Coherent Transmission Peer-reviewed

    Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2019 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　2019

  42. Backward-Rayleigh-Scattering Suppressed 160 Gbit/s 256 QAM Injection-Locked Bidirectional Coherent Transmission for Next Generation Mobile Fronthaul. Peer-reviewed

    Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, Katsumi Iwatsuki, Masataka Nakazawa

    European Conference on Optical Communication(ECOC)　1-3　2018/09

    Publisher: IEEE

    DOI： 10.1109/ECOC.2018.8535196 　

  43. Single-channel 7.68 Tbit/s, 64 QAM coherent Nyquist pulse transmission over 150 km with a spectral efficiency of 9.7 bit/s/Hz Peer-reviewed

    Kosuke Kimura, Junpei Nitta, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　26　(13)　17418-17428　2018/06

    DOI： 10.1364/OE.26.017418 　

    ISSN： 1094-4087

  44. Single-channel 200 Gbit/s, 10 Gsymbol/s-1024 QAM injection-locked coherent transmission over 160 km with a pilot-assisted adaptive equalizer Peer-reviewed

    Yixin Wang, Seiji Okamoto, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    OPTICS EXPRESS　26　(13)　17015-17024　2018/06

    DOI： 10.1364/OE.26.017015 　

    ISSN： 1094-4087

  45. Observation of guided acoustic-wave Brillouin scattering noise and its compensation in digital coherent optical fiber transmission Peer-reviewed

    Masataka Nakazawa, Masato Yoshida, Masaki Terayama, Seiji Okamoto, Keisuke Kasai, Toshihiko Hirooka

    OPTICS EXPRESS　26　(7)　9165-9181　2018/04

    DOI： 10.1364/OE.26.009165 　

    ISSN： 1094-4087

  46. 10.16-Peta-B/s Dense SDM/WDM Transmission Over 6-Mode 19-Core Fiber Across the C plus L Band Peer-reviewed

    Daiki Soma, Yuta Wakayama, Shohei Beppu, Seiya Sumita, Takehiro Tsuritani, Tetsuya Hayashi, Takuji Nagashima, Masato Suzuki, Masato Yoshida, Keisuke Kasai, Masataka Nakazawa, Hidenori Takahashi, Koji Igarashi, Itsuro Morita, Masatoshi Suzuki

    JOURNAL OF LIGHTWAVE TECHNOLOGY　36　(6)　1362-1368　2018/03

    DOI： 10.1109/JLT.2018.2799380 　

    ISSN： 0733-8724

    eISSN： 1558-2213

  47. 8 kHz linewidth, 50 mW output, full C-band wavelength tunable DFB LD array with self-optical feedback Peer-reviewed

    Keisuke Kasai, Masataka Nakazawa, Mitsuteru Ishikawa, Hiroyuki Ishii

    OPTICS EXPRESS　26　(5)　5675-5685　2018/03

    DOI： 10.1364/OE.26.005675 　

    ISSN： 1094-4087

  48. Experimental and numerical comparison of probabilistically shaped 4096 QAM and a uniformly shaped 1024 QAM in all-Raman amplified 160 km transmission Peer-reviewed

    Seiji Okamoto, Masaki Terayama, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　26　(3)　3535-3543　2018/02

    DOI： 10.1364/OE.26.003535 　

    ISSN： 1094-4087

  49. 50.4 Tbit/s, 128 QAM L-band WDM Injection-locked Coherent Transmission over 160 km with Spectral Efficiency of 10.5 bit/s/Hz Peer-reviewed

    Takashi Kan, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    23RD OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC2018)　2018

    ISSN： 2166-8884

    eISSN： 2166-8892

  50. 200 Gbit/s, 10 Gsymbol/s-1024 QAM Injection Locked Coherent Transmission over 160 km with a Pilot-assisted Adaptive Equalizer Peer-reviewed

    Keisuke Kasai, Yixing Wang, Seiji Okamoto, Masato Yoshida, Masataka Nakazawa

    23RD OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC2018)　2018

    ISSN： 2166-8884

    eISSN： 2166-8892

  51. Single-Channel 7.68 Tbit/s, 64 QAM Coherent Nyquist Pulse Transmission over 150 km with a Spectral Efficiency of 9.7 bit/s/Hz Peer-reviewed

    Kosuke Kimura, Junpei Nitta, Masato Yoshida, Keisuke Kasai, Toshihiro Hirooka, Masataka Nakazawa

    23RD OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC2018)　2018

    ISSN： 2166-8884

    eISSN： 2166-8892

  52. Reverse Phase Modulation Technique for GAWBS Noise Error Floor Elimination in 1024 QAM-160 km Digital Coherent Transmission

    Masato Yoshida, Naoya Takefushi, Masaki Terayama, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    23RD OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC2018)　2018

    ISSN： 2166-8884

    eISSN： 2166-8892

  53. Observation of Guided Acoustic-Wave Brillouin Scattering and its Digital Compensation in Coherent QAM Transmission Peer-reviewed

    Masataka Nakazawa, Masaki Terayama, Seiji Okamoto, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka

    2018 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXPOSITION (OFC)　2018　2018

    DOI： 10.1364/OFC.2018.M4B.2 　

  54. 4096 QAM (72 Gbit/s) Single-Carrier Coherent Optical Transmission with a Potential SE of 15.8 bit/s/Hz in All-Raman Amplified 160 km Fiber Link Peer-reviewed

    Masaki Terayama, Seiji Okamoto, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2018 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXPOSITION (OFC)　2018　2018

    DOI： 10.1364/OFC.2018.Th1F.2 　

  55. Experimental and Numerical Comparison of Probabilistically-Shaped 4096 QAM and Uniformly-Shaped 1024 QAM in All-Raman Amplified 160 km Transmission Peer-reviewed

    Seiji Okamoto, Masaki Terayama, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2018 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXPOSITION (OFC)　26　(3)　3535-3543　2018

    DOI： 10.1364/OE.26.003535 　

    ISSN： 1094-4087

  56. Narrow Linewidth Tunable DFB Laser Array Integrated With Optical Feedback Planar Lightwave Circuit (PLC) Peer-reviewed

    Hiroyuki Ishii, Naoki Fujiwara, Kei Watanabe, Shigeru Kanazawa, Mikitaka Itoh, Hirokazu Takenouchi, Yutaka Miyamoto, Keisuke Kasai, Masataka Nakazawa

    IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS　23　(6)　1501007　2017/11

    DOI： 10.1109/JSTQE.2017.2693021 　

    ISSN： 1077-260X

    eISSN： 1558-4542

  57. 1.5 mu m, mode-hop-free full C-band wavelength tunable laser diode with a linewidth of 8 kHz and a RIN of-130 dB/Hz and its extension to the L- band Peer-reviewed

    Keisuke Kasai, Masataka Nakazawa, Yasunori Tomomatsu, Takashmi Endo

    OPTICS EXPRESS　25　(18)　22113-22124　2017/09

    DOI： 10.1364/OE.25.022113 　

    ISSN： 1094-4087

  58. 42.3 Tbit/s, 18 Gbaud 64 QAM WDM coherent transmission over 160 km in the C-band using an injection-locked homodyne receiver with a spectral efficiency of 9 bit/s/Hz Peer-reviewed

    Takashi Kan, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    OPTICS EXPRESS　25　(19)　22726-22737　2017/09

    DOI： 10.1364/OE.25.022726 　

    ISSN： 1094-4087

  59. QAM Quantum Noise Stream Cipher Transmission Over 100 km With Continuous Variable Quantum Key Distribution Peer-reviewed

    Masataka Nakazawa, Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Takuya Hirano, Tsubasa Ichikawa, Ryo Namiki

    IEEE JOURNAL OF QUANTUM ELECTRONICS　53　(4)　8000316　2017/08

    DOI： 10.1109/JQE.2017.2708523 　

    ISSN： 0018-9197

    eISSN： 1558-1713

  60. 1024 QAM Coherent Optical Transmission In 31 Km-long, 19-core Fiber With Low Crosstalk And Large Effective Area Peer-reviewed

    M. Yoshida, K. Kasai, T. Hirooka, M. Nakazawa, K. Imamura, R. Sugizaki

    Opto-Electronics and Communications Conference (OECC 2017)　3-1K-2　2017/08

  61. Single-channel 3.84 Tbit/s, 64 QAM coherent Nyquist pulse transmission over 150 km with a spectral efficiency of 10.6 bit/s/Hz Peer-reviewed

    Junpei Nitta, Masato Yoshida, Kosuke Kimura, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　25　(13)　15199-15207　2017/06

    DOI： 10.1364/OE.25.015199 　

    ISSN： 1094-4087

  62. New Optical Phase-Locking System Based on Mode-Locked Fiber Laser for 640 Gbaud Coherent Nyquist QAM Transmission

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2017　22-22　2017

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2017.0_22 　

  63. Single-channel 3.84 Tbit/s, 64 QAM coherent Nyquist pulse transmission over 150 km with frequency-stabilized and mode-locked laser Peer-reviewed

    Masato Yoshida, Junpei Nitta, Kosuke Kimura, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    Optics InfoBase Conference Papers　2017　2017

    Publisher: OSA - The Optical Society

    DOI： 10.1364/OFC.2017.Th2A.52 　

  64. Single-Carrier 216 Gbit/s, 12 Gsymbol/s 512 QAM Coherent Transmission over 160 km with Injection-locked Homodyne Detection Peer-reviewed

    Yixin Wang, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　Tu2E.1　2017

  65. Single-Channel 3.84 Tbit/s, 64 QAM Coherent Nyquist Pulse Transmission over 150km with Frequency-Stabilized and Mode-Locked Laser Peer-reviewed

    Masato Yoshida, Junpei Nitta, Kosuke Kimura, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　Th2A.52　2017

  66. 42.3-Tbits/s, 18-Gbaud 64QAM WDM Coherent Transmission of 160 km over Full C-based using an Injection Locking Technique with a Spectral Efficiency of 9 bit/s/Hz Peer-reviewed

    Takashi Kan, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　2017　Th3F.5　2017

    DOI： 10.1364/OFC.2017.Th3F.5 　

  67. Full C-band, Mode-Hop-Free Wavelength-Tunable Laser Diode with a Linewidth of 8 kHz and a RIN of-130 dB/Hz Peer-reviewed

    Keisuke Kasai, Masataka Nakazawa, Yasunori Tomomatsu, Takashi Endo

    2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　W1E.2　2017

  68. Single-Carrier 216 Gbit/s, 12 Gsymbol/s 512 QAM Coherent Transmission over 160 km with Injection-locked Homodyne Detection Peer-reviewed

    Yixin Wang, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　2017　2017

    DOI： 10.1364/OFC.2017.Tu2E.1 　

  69. 42.3-Tbits/s, 18-Gbaud 64QAM WDM Coherent Transmission of 160 km over Full C-based using an Injection Locking Technique with a Spectral Efficiency of 9 bit/s/Hz Peer-reviewed

    Takashi Kan, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　2017

  70. Subpicosecond Coherent Nyquist Pulse Generation for 1-Tbaud Transmission Using a C2H2 Frequency-Stabilized CW Laser and a 40 GHz Optical Comb Generator Peer-reviewed

    Daiki Suzuki, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)　2017　SM2L.5　2017

    DOI： 10.1364/CLEO_SI.2017.SM2L.5 　

    ISSN： 2160-9020

  71. A New Optical Phase-Locked System Between Ultrashort Pulses for 640 Gbaud Nyquist OTDM Coherent QAM Transmission Peer-reviewed

    Kosuke Kimura, Junpei Nitta, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    43RD EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC 2017)　2017-　1-3　2017

    DOI： 10.1109/ECOC.2017.8345851 　

  72. 80 Gbit/s/ch, 256 QAM Digital Coherent Optical Transmission System with Injection-Locking for Next Generation Mobile Fronthaul Network Peer-reviewed

    Keisuke Kasai, Yixin Wang, Masato Yoshida, Toshihiko Hirooka, Katsumi Iwatsuki, Masataka Nakazawa

    43RD EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC 2017)　2017-　1-3　2017

    DOI： 10.1109/ECOC.2017.8346036 　

  73. Single-carrier 552 Gbit/s, 46 Gbaud 64 QAM Coherent Transmission over 100 km with Co-propagating 10 Gbit/s-OOK Signals Through a Deployed ROADM Network Peer-reviewed

    Keisuke Kasai, Toshihiko Hirooka, Masato Yoshida, Masataka Nakazawa, Masaki Shiraiwa, Yoshinari Awaji, Naoya Wada

    43RD EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC 2017)　2017-　1-3　2017

    DOI： 10.1109/ECOC.2017.8345944 　

  74. 1.55 mu m hydrogen cyanide optical frequency-stabilized and 10 GHz repetition-rate-stabilized mode-locked fiber laser Peer-reviewed

    Masato Yoshida, Kazuki Yoshida, Keisuke Kasai, Masataka Nakazawa

    OPTICS EXPRESS　24　(21)　24287-24296　2016/10

    DOI： 10.1364/OE.24.024287 　

    ISSN： 1094-4087

  75. 320 Gbit/s, 20 Gsymbol/s 256 QAM coherent transmission over 160 km by using injection-locked local oscillator Peer-reviewed

    Yixin Wang, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    OPTICS EXPRESS　24　(19)　22088-22096　2016/09

    DOI： 10.1364/OE.24.022088 　

    ISSN： 1094-4087

  76. Injection-locked Homodyne Detection System for Higher-order QAM Digital Coherent Transmission Invited Peer-reviewed

    K. Kasai, M. Yoshida, T. Hirooka, M. Nakazawa

    European Conference on Optical Communication (ECOC 2016)　2018　M1.C.3　2016/09

    DOI： 10.1364/OFC.2018.M4G.1 　

  77. 552 Gbit/s, 46 Gbaud, 64 QAM Coherent Transmission over 160 km with Simple LD-based Injection-locked Homodyne Detection Peer-reviewed

    K. Kasai, M. Yoshida, M. Nakazawa

    European Conference on Optical Communication (ECOC 2016)　W.4.P1.SC5.51　2016/09

  78. Real-time 70 Gbit/s, 128 QAM Quantum Noise Stream Cipher Transmission over 100 km with Secret Keys Delivered by Continuous Variable Quantum Key Distribution System Peer-reviewed

    M. Nakazawa, M. Yoshida, T. Hirooka, K. Kasai, T Hirano

    European Conference on Optical Communication (ECOC 2016)　W.4.P1.SC5.59　2016/09

  79. A 295 mW output, HCN frequency-stabilized CW erbium silica fiber laser with a linewidth of 5 kHz and a RIN of -120 dB/Hz Peer-reviewed

    K. Kasai, M. Yoshida, M. Nakazawa

    Optical Fiber Communication Conference (OFC)　W3E.1.　W3E.1　2016/03

  80. 295 mW output, frequency-stabilized erbium silica fiber laser with a linewidth of 5 kHz and a RIN of-120 dB/Hz Peer-reviewed

    Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    OPTICS EXPRESS　24　(3)　2737-2748　2016/02

    DOI： 10.1364/OE.24.002737 　

    ISSN： 1094-4087

  81. Single-channel 40 Gbit/s digital coherent QAM quantum noise stream cipher transmission over 480 km Peer-reviewed

    Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    Optics Express　24　(1)　652-661　2016/01/11

    Publisher: OSA - The Optical Society

    DOI： 10.1364/OE.24.000652 　

    ISSN： 1094-4087

  82. 45.12 Tbit/s, 235 ch-WDM 64 QAM Coherent Transmission over 160 km with an Injection Locked Homodyne Receiver

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2016　6-6　2016

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2016.0_6 　

  83. Single-channel 40 Gbit/s digital coherent QAM quantum noise stream cipher transmission over 480 km Peer-reviewed

    Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    OPTICS EXPRESS　24　(1)　652-661　2016/01

    DOI： 10.1364/OE.24.000652 　

    ISSN： 1094-4087

  84. Single-Channel 1.92 Tbit/s, 64 QAM Coherent Nyquist Orthogonal TDM Transmission With a Spectral Efficiency of 10.6 Bit/s/Hz Peer-reviewed

    David Odeke Otuya, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    JOURNAL OF LIGHTWAVE TECHNOLOGY　34　(2)　768-775　2016/01

    DOI： 10.1109/JLT.2015.2468580 　

    ISSN： 0733-8724

    eISSN： 1558-2213

  85. Optical and wireless-integrated next-generation access network based on coherent technologies Invited Peer-reviewed

    Toshihiko Hirooka, Masato Yoshida, Keisuke Kasai, Masataka Nakazawa

    BROADBAND ACCESS COMMUNICATION TECHNOLOGIES X　9772　9772-2　2016

    DOI： 10.1117/12.2211860 　

    ISSN： 0277-786X

  86. A 0.95 ps, 10 GHz, 60 mW HCN Frequency-Stabilized and Mode-Locked Fiber Laser at 1.55 mu m Peer-reviewed

    Masato Yoshida, Kazuki Yoshida, Keisuke Kasai, Masataka Nakazawa

    2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)　STu1P.3.　2016

    ISSN： 2160-9020

  87. A 0.95 ps, 10 GHz, 60 mW HCN Frequency-Stabilized and Mode-Locked Fiber Laser at 1.55 mu m Peer-reviewed

    Masato Yoshida, Kazuki Yoshida, Keisuke Kasai, Masataka Nakazawa

    2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)　STu1P.3　2016

    ISSN： 2160-9020

  88. 1024 QAM, 7-core Fiber/Multi-core EDFA Transmission over 100 km with an Aggregated Spectral Efficiency of 109 bit/s/Hz Peer-reviewed

    Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2016 21ST OPTOELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC) HELD JOINTLY WITH 2016 INTERNATIONAL CONFERENCE ON PHOTONICS IN SWITCHING (PS)　MB2-5　2016

  89. 320 Gbit/s, 256 QAM LD-based Coherent Transmission over 160 km with an Injection-locked Homodyne Detection Technique Peer-reviewed

    Yixin Wang, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2016 21ST OPTOELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC) HELD JOINTLY WITH 2016 INTERNATIONAL CONFERENCE ON PHOTONICS IN SWITCHING (PS)　ThB3-3　2016

  90. First demonstration of digital coherent transmission in a deployed ROADM network with a 120 Gbit/s polarization-multiplexed 64 QAM signal Peer-reviewed

    Toshihiko Hirookaa, Keisuke Kasai, Yixin Wang, Masataka Nakazawa, Masaki Shiraiwa, Yoshinari Awaji, Naoya Wada

    IEICE ELECTRONICS EXPRESS　12　(23)　20150884　2015/12

    DOI： 10.1587/elex.12.20150884 　

    ISSN： 1349-2543

  91. 448 Gbit/s, 32 Gbaud 128 QAM coherent transmission over 150 km with a potential spectral efficiency of 10.7 bit/s/Hz Peer-reviewed

    Keisuke Kasai, Yixin Wang, David Odeke Otuya, Masato Yoshida, Masataka Nakazawa

    OPTICS EXPRESS　23　(22)　28423-28429　2015/11

    DOI： 10.1364/OE.23.028423 　

    ISSN： 1094-4087

  92. 80 Gbit/s, 256 QAM coherent transmission over 150 km with an injection-locked homodyne receiver Peer-reviewed

    Keisuke Kasai, Yixin Wang, Shohei Beppu, Masato Yoshida, Masataka Nakazawa

    OPTICS EXPRESS　23　(22)　29174-29183　2015/11

    DOI： 10.1364/OE.23.029174 　

    ISSN： 1094-4087

  93. High-speed, high spectrally efficient 64 QAM orthogonal TDM coherent Nyquist pulse transmission Invited Peer-reviewed

    Keisuke Kasai, David Odeke Otuya, Koudai Harako, Toshihiko Hirooka, Masataka Nakazawa

    2015 IEEE Summer Topicals Meeting Series, SUM 2015　MF1.3　76-77　2015/09/09

    Publisher: Institute of Electrical and Electronics Engineers Inc.

    DOI： 10.1109/PHOSST.2015.7248201 　

  94. 1024 QAM, 7-core (60 Gbit/s X 7) fiber transmission over 55 km with an aggregate potential spectral efficiency of 109 bit/s/Hz Peer-reviewed

    Masato Yoshida, Shohei Beppu, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    Optics Express　23　(16)　20760-20766　2015/08/10

    Publisher: OSA - The Optical Society

    DOI： 10.1364/OE.23.020760 　

    ISSN： 1094-4087

  95. 1024 QAM, 7-core (60 Gbit/s x 7) fiber transmission over 55 km with an aggregate potential spectral efficiency of 109 bit/s/Hz Peer-reviewed

    Masato Yoshida, Shohei Beppu, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　23　(16)　20760-20766　2015/08

    DOI： 10.1364/OE.23.020760 　

    ISSN： 1094-4087

  96. HCN frequency-stabilized 10 GHz mode-locked fiber laser Peer-reviewed

    K. Yoshida, K. Kasai, M. Yoshida, M. Nakazawa

    International Symposium on Ultra-fast Photonics Technologies　p-34　2015/07

  97. HCN frequency-stabilized 10 GHz mode-locked fiber laser Peer-reviewed

    K. Yoshida, K. Kasai, M. Yoshida, M. Nakazawa

    International Symposium on Ultrafast Photonic Technologies/Extremely Advanced Transmission Technology (ISUPT/EXAT 2015)　P-34　2015/07

  98. Multi-core Fibers and Systems for Space-division Multiplexing Invited Peer-reviewed

    T. Hirooka, M. Yoshida, K. Kasai, M. Nakazawa

    Photonics North 2015　7.60　2015/06

  99. Real-time 10vGbit/s-16 QAM quantum stream cipher transmission over 320 km with FPGA-based transmitter and receiver Peer-reviewed

    M. Yoshida, T. Hirooka, K. Kasai, M. Nakazawa

    Optical Fiber Communication Conference (OFC)　W4F.4.　2015/03

  100. 2048 QAM (66 Gbit/s) single-carrier coherent optical transmission over 150 km with a potential SE of 15.3 bit/s/Hz Peer-reviewed

    Shohei Beppu, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    OPTICS EXPRESS　23　(4)　4960-4969　2015/02

    DOI： 10.1364/OE.23.004960 　

    ISSN： 1094-4087

  101. 10 GHz, 0.95 ps coherent optical pulse source based on 1.55 μm HCN frequency-stabilized mode-locked fiber laser

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2015　2-2　2015

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2015.0_2 　

  102. An 11.6 W output, 6 kHz linewidth, single-polarization EDFA-MOPA system with a (C2H2)-C-13 frequency stabilized fiber laser Peer-reviewed

    Akira Fujisaki, Shunichi Matsushita, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　23　(2)　1081-1087　2015/01

    DOI： 10.1364/OE.23.001081 　

    ISSN： 1094-4087

  103. Single-Channel 1.92 Tbit/s, 64 QAM Coherent Orthogonal TDM Transmission of 160 Gbaud Optical Nyquist Pulses with 10.6 bit/s/Hz Spectral Efficiency Peer-reviewed

    David Odeke Otuya, Koudai Harako, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2015 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　M3G.2.　2015

  104. 256 QAM (Polarization-multiplexed, 5 Gsymbol/s) Coherent Transmission with an Injection-locked Homodyne Detection Technique Peer-reviewed

    Keisuke Kasai, Shohei Beppu, Yixin Wang, Masataka Nakazawa

    2015 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　W1E.4.　W1E.4　2015

  105. Single-Channel 1.92 Tbit/s, 64 QAM Coherent Orthogonal TDM Transmission of 160 Gbaud Optical Nyquist Pulses with 10.6 bit/s/Hz Spectral Efficiency Peer-reviewed

    David Odeke Otuya, Koudai Harako, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2015 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　M3G.2　2015

  106. Real-time 10 Gbit/s-16 QAM Quantum Stream Cipher Transmission over 320 km with FPGA-based Transmitter and Receiver Peer-reviewed

    Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    2015 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　W4F.4　2015

  107. Real-time Adaptive 4-64 QAM, 20-60 Gbit/s Quantum Noise Stream Cipher Transmission over 320 km with FPGA-based Transmitter and Receiver Peer-reviewed

    Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    ECOC 2015 41ST EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION　P.5.13.　2015

    DOI： 10.1109/ECOC.2015.7341787 　

  108. Real-time Adaptive 4-64 QAM, 20-60 Gbit/s Quantum Noise Stream Cipher Transmission over 320 km with FPGA-based Transmitter and Receiver Peer-reviewed

    Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    ECOC 2015 41ST EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION　P.5.13　2015

    DOI： 10.1109/ECOC.2015.7341787 　

  109. QAM Quantum Noise Stream Cipher Using Digital Coherent Optical Transmission Invited Peer-reviewed

    M. Yoshida, T. Hirooka, K. Kasai, M. Nakazawa

    2015 49TH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS AND COMPUTERS　TP1-9　1007-1011　2015

    DOI： 10.1109/ACSSC.2015.7421290 　

  110. High-performance TDM demultiplexing of coherent Nyquist pulses using time-domain orthogonality Peer-reviewed

    Koudai Harako, David Odeke Otuya, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　22　(24)　29456-29464　2014/12

    DOI： 10.1364/OE.22.029456 　

    ISSN： 1094-4087

  111. 120 Gbit/s injection-locked homodyne coherent transmission of polarization-multiplexed 64 QAM signals over 150 km Peer-reviewed

    Yixin Wang, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    OPTICS EXPRESS　22　(25)　31310-31316　2014/12

    DOI： 10.1364/OE.22.031310 　

    ISSN： 1094-4087

  112. A single-channel 40 Gbit/s digital coherent QAM quantum stream cipher transmission over 480 km

    Masataka Nakazawa, Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai

    Asia Communications and Photonics Conference, ACP　2014-　2014/11/01

    Publisher: OSA - The Optical Society

    ISSN： 2162-108X

  113. 140 Gbit/s, 128 QAM LD-based Coherent Transmission over 150 km with an Injection-locked Homodyne Detection Technique Peer-reviewed

    Y. Wang, S. Beppu, K. Kasai, M. Yoshida, M. Nakazawa

    Asia Communications and Photonics Conference (ACP)　ATh1E.3　2014/11

  114. 140 Gbit/s, 128 QAM LD-based Coherent Transmission over 150 km with an Injection-locked Homodyne Detection Technique Peer-reviewed

    Y. Wang, S. Beppu, K. Kasai, M. Yoshida, M. Nakazawa

    Asia Communications and Photonics Conference (ACP2014)　ATh1E.3　2014/11

  115. Single-channel 1.92 Tbit/s, Pol-Mux-64 QAM coherent Nyquist pulse transmission over 150 km with a spectral efficiency of 7.5 bit/s/Hz Peer-reviewed

    David Odeke Otuya, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　22　(20)　23776-23785　2014/10

    DOI： 10.1364/OE.22.023776 　

    ISSN： 1094-4087

  116. Adaptive 4 similar to 64 QAM real-time coherent optical transmission over 320 km with FPGA-based transmitter and receiver Peer-reviewed

    Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    OPTICS EXPRESS　22　(13)　16520-16527　2014/06

    DOI： 10.1364/OE.22.016520 　

    ISSN： 1094-4087

  117. QAM quantum stream cipher using digital coherent optical transmission Peer-reviewed

    Masataka Nakazawa, Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai

    OPTICS EXPRESS　22　(4)　4098-4107　2014/02

    DOI： 10.1364/OE.22.004098 　

    ISSN： 1094-4087

  118. A 160 mW output, 5 kHz linewidth frequency-stabilized erbium silica fiber laser with a short cavity configuration

    Keisuke Kasai, Akira Fujisaki, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa, Shin Masuda

    Optics InfoBase Conference Papers　2014

    Publisher: Optical Society of America (OSA)

    DOI： 10.1364/cleo_si.2014.sw1n.4 　

    ISSN： 2162-2701

  119. 2048 QAM coherent optical transmission over 150 km

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2014　(0)　13-13　2014

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2014.0_13 　

  120. 1.92 Tbit/s, 64 QAM Coherent Nyquist Pulse Transmission over 150 km with a Spectral Efficiency of 7.5 bit/s/Hz Peer-reviewed

    David Odeke Otuya, Keisuke Kasai, Toshihiko Hirooka, Masato Yoshida, Masataka Nakazawa

    2014 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　2014

  121. 2048 QAM (66 Gbit/s) Single-Carrier Coherent Optical Transmission over 150 km with a Potential SE of 15.3 bit/s/Hz Peer-reviewed

    Shohei Beppu, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2014 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　2014

  122. Real-Time Adaptive 4-64 QAM Coherent Optical Transmission over 320 km with FPGA-Based Transmitter and Receiver Peer-reviewed

    Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    2014 EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　22　(13)　16520-16527　2014

    DOI： 10.1364/OE.22.016520 　

  123. A 160 mW Output, 5 kHz Linewidth Frequency-Stabilized Erbium Silica Fiber Laser with a Short Cavity Configuration Peer-reviewed

    Keisuke Kasai, Akira Fujisaki, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa, Shin Masuda

    2014 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)　SW1N.4　2014

    ISSN： 2160-9020

  124. A 6 kHz Linewidth, Injection-Locked LD Using a Master Erbium Fiber Laser Peer-reviewed

    Yixin Wang, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2014 OPTOELECTRONICS AND COMMUNICATIONS CONFERENCE AND AUSTRALIAN CONFERENCE ON OPTICAL FIBRE TECHNOLOGY (OECC/ACOFT 2014)　TU6F-5　417-418　2014

  125. 60 Gbit/s, 64 QAM LD-based injection-locked coherent heterodyne transmission over 160 km with a spectral efficiency of 9 bit/s/Hz Peer-reviewed

    Yixin Wang, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    IEICE ELECTRONICS EXPRESS　11　(18)　20140601　2014

    DOI： 10.1587/elex.11.20140641 　

    ISSN： 1349-2543

  126. Real-Time Adaptive 4-64 QAM Coherent Optical Transmission over 320 km with FPGA-Based Transmitter and Receiver Peer-reviewed

    Masato Yoshida, Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    2014 EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　Th.2.5.2.　2014

    DOI： 10.1109/ECOC.2014.6963904 　

  127. Novel Ultrafast TDM Demultiplexing Scheme Using Orthogonality in Coherent Nyquist Pulses Peer-reviewed

    Koudai Harako, David Odeke Otuya, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2014 EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　Tu4.6.5.　2014

    DOI： 10.1109/ECOC.2014.6963952 　

  128. A Single-Channel 960 Gbit/s 64 QAM Orthogonal TDM Transmission with a Spectral Efficiency of 10.0 bit/s/Hz Using Coherent Nyquist Pulses Peer-reviewed

    David Odeke Otuya, Koudai Harako, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2014 EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　We.2.3.4.　2014

    DOI： 10.1109/ECOC.2014.6964004 　

  129. Novel Ultrafast TDM Demultiplexing Scheme Using Orthogonality in Coherent Nyquist Pulses Peer-reviewed

    Koudai Harako, David Odeke Otuya, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2014 EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　Tu4.6.5　2014

    DOI： 10.1109/ECOC.2014.6963952 　

  130. A Single-Channel 960 Gbit/s 64 QAM Orthogonal TDM Transmission with a Spectral Efficiency of 10.0 bit/s/Hz Using Coherent Nyquist Pulses Peer-reviewed

    David Odeke Otuya, Koudai Harako, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    2014 EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　We.2.3.4　2014

    DOI： 10.1109/ECOC.2014.6964004 　

  131. 2048 QAM (66 Gbit/s) Single-Carrier Coherent Optical Transmission over 150 km with a Potential SE of 15.3 bit/s/Hz Peer-reviewed

    Shohei Beppu, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2014 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC)　23　(4)　4960-4969　2014

    DOI： 10.1109/OFC.2014.6886985 　

  132. 120 Gbit/s, polarization-multiplexed 10 Gsymbol/s, 64 QAM coherent transmission over 150 km using an optical voltage controlled oscillator Peer-reviewed

    Yixin Wang, Keisuke Kasai, Tatsunori Omiya, Masataka Nakazawa

    OPTICS EXPRESS　21　(23)　28290-28296　2013/11

    DOI： 10.1364/OE.21.028290 　

    ISSN： 1094-4087

  133. A single-channel 1.92 Tbit/s, 64 QAM coherent optical pulse transmission over 150 km using frequency-domain equalization Peer-reviewed

    David Odeke Otuya, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    OPTICS EXPRESS　21　(19)　22808-22816　2013/09

    DOI： 10.1364/OE.21.022808 　

    ISSN： 1094-4087

  134. A Single-Channel 1.92 Tbit/s, 64 QAM Coherent Pulse OTDM Transmission over 150 km Peer-reviewed

    David O. Otuya, Keisuke Kasai, Toshihiko Hirooka, Masato Yoshida, Masataka Nakazawa, Tokutaka Hara, Satoshi Oikawa

    Opto Electronics and Communications Conference (OECC)　WR2-2　2013/07

  135. Extremely Higher-Order Modulation Formats Peer-reviewed

    Masataka Nakazawa, Toshihiko Hirooka, Masato Yoshida, Keisuke Kasai

    Optical Fiber Telecommunications VIB: Systems and Networks: Sixth Edition　297-336　2013/05/13

    Publisher: Elsevier Inc.

    DOI： 10.1016/B978-0-12-396960-6.00007-9 　

  136. Generation of 9 W, 4 kHz linewidth (C2H2)-C-13 frequency-stabilized fiber laser output with core pumped erbium-doped amplifier Peer-reviewed

    Akira Fujisaki, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, Andmasataka Nakazawa

    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)　2013

    ISSN： 2160-9020

  137. An LD-Based Ultra-Low Phase Noise OPLL Circuit Using an Optical Voltage Controlled Oscillator Peer-reviewed

    Keisuke Kasai, Yixin Wang, Masataka Nakazawa

    2013 OPTICAL FIBER COMMUNICATION CONFERENCE AND EXPOSITION AND THE NATIONAL FIBER OPTIC ENGINEERS CONFERENCE (OFC/NFOEC)　OW3D.2　2013

  138. A Single-Channel, 1.6 Tbit/s 32 QAM Coherent Pulse Transmission Over 150 km With RZ-CW Conversion and FDE Techniques Peer-reviewed

    David Odeke Otuya, Keisuke Kasai, Toshihiko Hirooka, Masato Yoshida, Masataka Nakazawa, Tokutaka Hara, Satoshi Oikawa

    2013 OPTICAL FIBER COMMUNICATION CONFERENCE AND EXPOSITION AND THE NATIONAL FIBER OPTIC ENGINEERS CONFERENCE (OFC/NFOEC)　OTh4E.4　2013

  139. 120 Gbit/s, 64 QAM coherent transmission employing an optical voltage controlled oscillator Peer-reviewed

    Yixin Wang, Keisuke Kasai, Tatsunori Omiya, Masataka Nakazawa

    IET Conference Publications　2013　(622)　110-112　2013

    DOI： 10.1049/cp.2013.1309 　

  140. Single-Carrier 800-Gb/s 32 RZ/QAM Coherent Transmission Over 225 km Employing a Novel RZ-CW Conversion Technique Peer-reviewed

    Keisuke Kasai, David Odeke Otuya, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    IEEE PHOTONICS TECHNOLOGY LETTERS　24　(5)　416-418　2012/03

    DOI： 10.1109/LPT.2011.2180373 　

    ISSN： 1041-1135

    eISSN： 1941-0174

  141. FPGAを用いた64 QAMリアルタイムコヒーレント光伝送 Peer-reviewed

    吉田真人, 大宮達則, 葛西恵介, 中沢正隆

    電子情報通信学会論文誌　J95-B　(3)　405-413　2012/03

    ISSN： 1344-4697

  142. 1.6 Tbit/s, Single-carrier 32 RZ/QAM Coherent Transmission Over 150 km Utilizing an RZ-CW Conversion Scheme

    Otuya David Odeke

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2012　12-12　2012

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2012.0_12 　

  143. Ultrafast Coherent Optical Transmission Peer-reviewed

    Masataka Nakazawa, Toshihiko Hirooka, Masato Yoshida, Keisuke Kasai

    IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS　18　(1)　363-376　2012/01

    DOI： 10.1109/JSTQE.2011.2125781 　

    ISSN： 1077-260X

    eISSN： 1558-4542

  144. Novel RZ-CW conversion scheme for ultra multi-level, high-speed coherent OTDM transmission Peer-reviewed

    Masataka Nakazawa, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka

    OPTICS EXPRESS　19　(26)　574-580　2011/12

    DOI： 10.1364/OE.19.00B574 　

    ISSN： 1094-4087

  145. Absolute frequency stabilization of a laser diode based on triple ring resonators to an C2H2 absorption line Peer-reviewed

    Keisuke Kasai, Masataka Nakazawa, Hiroyuki Yamazaki

    Microoptics Conference (MOC)　G-4　2011/10

  146. Polarization-multiplexed, 10 Gsymbol/s, 64 QAM coherent transmission over 150 km with OPLL-based homodyne detection employing narrow linewidth LDs Peer-reviewed

    Yixin Wang, Keisuke Kasai, Masataka Nakazawa

    IEICE ELECTRONICS EXPRESS　8　(17)　1444-1449　2011/09

    DOI： 10.1587/elex.8.1444 　

    ISSN： 1349-2543

  147. 1.5-mu m Frequency-Stabilized lambda/4-Shifted DFB LD Employing an External Fiber Ring Cavity With a Linewidth of 2.6 kHz and an RIN of-135 dB/Hz Peer-reviewed

    Keisuke Kasai, Anne Mori, Masataka Nakazawa

    IEEE PHOTONICS TECHNOLOGY LETTERS　23　(15)　1046-1048　2011/08

    DOI： 10.1109/LPT.2011.2150211 　

    ISSN： 1041-1135

  148. Recent progress on ultra-high speed and multi level coherent transmission Invited Peer-reviewed

    Toshihiko Hirooka, Keisuke Kasai, Masataka Nakazawa

    Korea-Japan Workshop on Beyond 100G　2011/06

  149. 256 QAM Digital Coherent Optical Transmission Using Raman Amplifiers Peer-reviewed

    Masato Yoshida, Seiji Okamoto, Tatsunori Omiya, Keisuke Kasai, Masataka Nakazawa

    IEICE TRANSACTIONS ON COMMUNICATIONS　E94B　(2)　417-424　2011/02

    DOI： 10.1587/transcom.E94.B.417 　

    ISSN： 0916-8516

    eISSN： 1745-1345

  150. A 13C2H2 frequency-stabilized λ/4-shifted dfb laser diode with an external fiber ring cavity having a linewidth of 2.6 kHz and a RIN of-135 dB/Hz

    Keisuke Kasai, Anne Mori, Masataka Nakazawa

    Optics InfoBase Conference Papers　2011

    ISSN： 2162-2701

  151. A precise OPLL circuit employing narrow linewidth LDs and its application to coherent optical QAM transmission

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2011　22-22　2011

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2011.0_22 　

  152. Real-time FPGA-based Coherent Optical Receiver for 1 Gsymbol/s, 64 QAM Transmission Peer-reviewed

    Masato Yoshida, Tatsunori Omiya, Keisuke Kasai, Masataka Nakazawa

    2011 OPTICAL FIBER COMMUNICATION CONFERENCE AND EXPOSITION (OFC/NFOEC) AND THE NATIONAL FIBER OPTIC ENGINEERS CONFERENCE　OTuN3　2011

  153. A (C2H2)-C-13 Frequency-Stabilized lambda/4-shifted DFB Laser Diode with an External Fiber Ring Cavity Having a Linewidth of 2.6 kHz and a RIN of-135 dB/Hz Peer-reviewed

    Keisuke Kasai, Anne Mori, Masataka Nakazawa

    2011 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)　CTuV4　2011

    ISSN： 2160-9020

  154. Novel RZ-CW Conversion Scheme for Ultra Multi-Level, High-Speed Coherent OTDM Transmission Peer-reviewed

    Masataka Nakazawa, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka

    2011 37TH EUROPEAN CONFERENCE AND EXHIBITION ON OPTICAL COMMUNICATIONS (ECOC 2011)　19　(26)　B574-B580　2011

  155. High Time-Resolution 640-Gb/s Clock Recovery Using Time-Domain Optical Fourier Transformation and Narrowband Optical Filter Peer-reviewed

    Pengyu Guan, Hans Christian Hansen Mulvad, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa

    IEEE PHOTONICS TECHNOLOGY LETTERS　22　(23)　1735-1737　2010/12

    DOI： 10.1109/LPT.2010.2083644 　

    ISSN： 1041-1135

  156. 60Gbit/s 64 QAM-OFDM coherent optical transmission with a 5.3GHz bandwidth Peer-reviewed

    Tatsunori Omiya, Seiji Okamoto, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    IEICE ELECTRONICS EXPRESS　7　(15)　1163-1168　2010/08

    DOI： 10.1587/elex.7.1163 　

    ISSN： 1349-2543

  157. Single-Channel 400-Gb/s OTDM-32 RZ/QAM Coherent Transmission Over 225 km Using an Optical Phase-Locked Loop Technique Peer-reviewed

    Keisuke Kasai, Tatsunori Omiya, Pengyu Guan, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    IEEE PHOTONICS TECHNOLOGY LETTERS　22　(8)　562-564　2010/04

    DOI： 10.1109/LPT.2010.2042708 　

    ISSN： 1041-1135

  158. 256-QAM (64 Gb/s) Coherent Optical Transmission Over 160 km With an Optical Bandwidth of 5.4 GHz Peer-reviewed

    Masataka Nakazawa, Seiji Okamoto, Tatsunori Omiya, Keisuke Kasai, Masato Yoshida

    IEEE PHOTONICS TECHNOLOGY LETTERS　22　(3)　185-187　2010/02

    DOI： 10.1109/LPT.2009.2037238 　

    ISSN： 1041-1135

  159. Recent progress on OTDM terabit/s transmission and their future

    Toshihiko Hirooka, M. Nakazawa, M. Yoshida, K. Kasai, P. Guan, T. Hirano

    2010 Conference on Optical Fiber Communication, Collocated National Fiber Optic Engineers Conference, OFC/NFOEC 2010　2010

  160. 256 QAM (64 Gbit/s) Coherent Optical Transmission over 160 km with an Optical Bandwidth of 5.4 GHz Peer-reviewed

    Masataka Nakazawa, Seiji Okamoto, Tatsunori Omiya, Keisuke Kasai, Masato Yoshida

    2010 CONFERENCE ON OPTICAL FIBER COMMUNICATION OFC COLLOCATED NATIONAL FIBER OPTIC ENGINEERS CONFERENCE OFC-NFOEC　OMJ5　2010

  161. 140 Gbit/s Coherent Optical Transmission over 150 km with a 10 Gsymbol/s Polarization-Multiplexed 128 QAM Signal Peer-reviewed

    Seiji Okamoto, Tatsunori Omiya, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2010 CONFERENCE ON OPTICAL FIBER COMMUNICATION OFC COLLOCATED NATIONAL FIBER OPTIC ENGINEERS CONFERENCE OFC-NFOEC　OThD5　2010

  162. Single-Channel 400 Gbit/s, OTDM-32 RZ/QAM Coherent Transmission Over 225 km Using an Optical Phase-Locked Loop Technique Peer-reviewed

    Keisuke Kasai, Tatsunori Omiya, Pengyu Guan, Masato Yoshida, Toshihiko Hirooka, Masataka Nakazawa

    2010 CONFERENCE ON OPTICAL FIBER COMMUNICATION OFC COLLOCATED NATIONAL FIBER OPTIC ENGINEERS CONFERENCE OFC-NFOEC　OThD6　2010

  163. A C(2)H(2) Frequency-Stabilized Laser Diode with a Linewidth of 4 kHz and Its Application to an Optical Phase-Locked Loop Peer-reviewed

    Keisuke Kasai, Masataka Nakazawa

    2010 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS)　CTuKK7　2010

  164. High-Resolution 640 Gbit/s Clock Recovery using Time-Domain Optical Fourier Transformation and Narrowband Optical Filter Peer-reviewed

    H. C. Hansen Mulvad, P. Guan, K. Kasai, T. Hirooka, M. Nakazawa

    2010 36TH EUROPEAN CONFERENCE AND EXHIBITION ON OPTICAL COMMUNICATION (ECOC), VOLS 1 AND 2　Mo.1.A.6　2010

    DOI： 10.1109/ECOC.2010.5621124 　

  165. 512 QAM (54 Gbit/s) Coherent Optical Transmission over 150 km with an Optical Bandwidth of 4.1 GHz Peer-reviewed

    Seiji Okamoto, Kazushi Toyoda, Tatsunori Omiya, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2010 36TH EUROPEAN CONFERENCE AND EXHIBITION ON OPTICAL COMMUNICATION (ECOC), VOLS 1 AND 2　PD2.3　2010

    DOI： 10.1109/ECOC.2010.5621378 　

  166. FM-eliminated C2H2 frequency-stabilized laser diode with an RIN of-135 dB/Hz and a linewidth of 4 kHz Peer-reviewed

    Keisuke Kasai, Masataka Nakazawa

    OPTICS LETTERS　34　(14)　2225-2227　2009/07

    DOI： 10.1364/OL.34.002225 　

    ISSN： 0146-9592

  167. C(2)H(2) absolutely optical frequency-stabilized and 40 GHz repetition-rate-stabilized, regeneratively mode-locked picosecond erbium fiber laser at 1.53 mu m Peer-reviewed

    Masataka Nakazawa, Masato Yoshida, Keisuke Kasai

    2009 CONFERENCE ON LASERS AND ELECTRO-OPTICS AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (CLEO/QELS 2009), VOLS 1-5　CMY4　771-772　2009

  168. 24 Gbit/s, 64 QAM-OFDM Coherent Transmission with a Bandwidth of 2.5 GHz Peer-reviewed

    Tatsunori Omiya, Hiroki Goto, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2009 35TH EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　1.3.2　2009

  169. C2H2 absolutely optical frequency-stabilized and 40 GHz repetition-rate-stabilized, regeneratively mode-locked picosecond erbium fiber laser at 1.53 mu m Peer-reviewed

    Masataka Nakazawa, Keisuke Kasai, Masato Yoshida

    OPTICS LETTERS　33　(22)　2641-2643　2008/11

    DOI： 10.1364/OL.33.002641 　

    ISSN： 0146-9592

  170. Polarization and frequency division multiplexed 1Gsymbol/s, 64 QAM coherent optical transmission with 8.6bit/s/Hz spectral efficiency over 160km Peer-reviewed

    Hiroki Goto, Masato Yoshida, Tatsunori Omiya, Keisuke Kasai, Masataka Nakazawa

    IEICE ELECTRONICS EXPRESS　5　(18)　776-781　2008/09

    DOI： 10.1587/elex.5.776 　

    ISSN： 1349-2543

  171. Polarization-multiplexed 1 Gsymbol/s,128 QAM (14 Gbit/s) coherent optical transmission over 160 km with a 1.4 GHz bandwidth

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2008　(0)　45-45　2008

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2008.0_45 　

  172. 1.3 GHz ultranarrow FBG optical filter with 20-dB side lobe suppression

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2008　(0)　46-46　2008

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2008.0_46 　

  173. Frequency Division Multiplexed 1 Gsymbol/s, 64 QAM Coherent Optical Transmission with a Spectral Efficiency of 8.6 bit/s/Hz

    Masato Yoshida, Hiroki Goto, Tatsunori Omiya, Keisuke Kasai, Masataka Nakazawa

    2008 34TH EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　2008

  174. The use of a Nyquist filter for reducing an optical signal bandwidth in a coherent QAM optical transmission Peer-reviewed

    Keisuke Kasai, Jumpei Hongo, Hiroki Goto, Masato Yoshida, Masataka Nakazawa

    IEICE ELECTRONICS EXPRESS　5　(1)　6-10　2008/01

    DOI： 10.1587/elex.5.6 　

    ISSN： 1349-2543

  175. 64 and 128 coherent QAM optical transmission over 150 km using frequency-stabilized laser and heterodyne PLL detection Peer-reviewed

    Masato Yoshida, Hiroki Goto, Keisuke Kasai, Masataka Nakazawa

    OPTICS EXPRESS　16　(2)　829-840　2008/01

    DOI： 10.1364/OE.16.000829 　

    ISSN： 1094-4087

  176. Polarization-multiplexed 1 Gsymbol/s, 128 QAM (14 Gbit/s) coherent optical transmission over 160 km using a 1.4 GHz Nyquist filter Peer-reviewed

    Hiroki Goto, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2008 CONFERENCE ON OPTICAL FIBER COMMUNICATION/NATIONAL FIBER OPTIC ENGINEERS CONFERENCE, VOLS 1-8　JThA45　133-135　2008

    DOI： 10.1109/OFC.2008.4528075 　

  177. Frequency Division Multiplexed 1 Gsymbol/s, 64 QAM Coherent Optical Transmission with a Spectral Efficiency of 8.6 bit/s/Hz Invited Peer-reviewed

    Masato Yoshida, Hiroki Goto, Tatsunori Omiya, Keisuke Kasai, Masataka Nakazawa

    2008 34TH EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　Mo.4.D.5　2008

    DOI： 10.1109/ECOC.2008.4729160 　

  178. 1 Gsymbol/s, 64 QAM coherent optical transmission with a spectral efficiency of 8 bit/s/Hz using a Nyquist filter Peer-reviewed

    Keisuke Kasai, Jumpei Hongo, Hiroki Goto, Masato Yoshida, Masataka Nakazawa

    Opto-Electronics and Communications Conference (OECC)　PD1-1　2007/07

  179. Mode-hop-free, optical frequency tunable 40-GHz mode-locked fiber laser Peer-reviewed

    Masato Yoshida, Keisuke Kasai, Masataka Nakazawa

    IEEE JOURNAL OF QUANTUM ELECTRONICS　43　(7-8)　704-708　2007/07

    DOI： 10.1109/JQE.2007.901289 　

    ISSN： 0018-9197

    eISSN： 1558-1713

  180. 1-Gsymbol/s 64-QAM coherent optical transmission over 150 km Peer-reviewed

    Jumpei Hongo, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    IEEE PHOTONICS TECHNOLOGY LETTERS　19　(9-12)　638-640　2007/05

    DOI： 10.1109/LPT.2007.894944 　

    ISSN： 1041-1135

    eISSN： 1941-0174

  181. Highly spectral-efficient QAM coherent transmission using an optical phase-locked loop over long distances Peer-reviewed

    Keisuke Kasai, Jumpei Hongo, Masato Yoshida, Masataka Nakazawa

    Asia-Pacific Microwave Photonics Conference (AP-MWP)　2007/04

  182. Optical phase-locked loop for coherent transmission over 500 km Peer-reviewed

    Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    Optical Fiber Communication Conference (OFC)　JWA49　2007/03

  183. Polarization-Multiplexed 1 Gsymbol/s, 64 QAM (12 Gbit/s) coherent optical transmission over 150 km with an optical bandwidth of 2 GHz Peer-reviewed

    Masataka Nakazawa, Jumpei Hongo, Keisuke Kasai, Masato Yoshida

    Optical Fiber Communication Conference (OFC)　PDP26　2007/03

  184. Optical phase-locked loop for coherent transmission over 500km using heterodyne detection with fiber lasers Peer-reviewed

    Keisuke Kasai, Jumpei Hongo, Masato Yoshida, Masataka Nakazawa

    IEICE ELECTRONICS EXPRESS　4　(3)　77-81　2007/02

    DOI： 10.1587/elex.4.77 　

    ISSN： 1349-2543

  185. 1.5 μm 13C2H2 frequency-stabilized fiber laser and its application to QAM coherent transmission with high spectral efficiency

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2007　(0)　29-29　2007

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2007.0_29 　

  186. A C2H2 frequency-stabilized erbium-doped fiber laser and its application to coherent communication Invited Peer-reviewed

    Masato Yoshida, Keisuke Kasai, Jumpei Hongo, Masataka Nakazawa

    FIBER LASERS IV: TECHNOLOGY, SYSTEMS, AND APPLICATIONS　6453　(6453-85)　2007

    DOI： 10.1117/12.714489 　

    ISSN： 0277-786X

  187. 1 Gsymbol/s, 64 QAM coherent optical transmission over 150 km with a spectral efficiency of 3 bit/s/Hz Peer-reviewed

    Jumpei Hongou, Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    OFC/NFOEC 2007 - Optical Fiber Communication and the National Fiber Optic Engineers Conference 2007　OMP3　2007

    DOI： 10.1109/OFC.2007.4348615 　

  188. A mode-hop-free, frequency-tunable 40 GHz mode-locked fiber laser Peer-reviewed

    Masato Yshida, Keisuke Kasai, Masataka Nakazawa

    OFC/NFOEC 2007 - Optical Fiber Communication and the National Fiber Optic Engineers Conference 2007　OTuF3　2007

    DOI： 10.1109/OFC.2007.4348785 　

  189. Performance improvement of an acetylene (C2H2) frequency-stabilized fiber laser Peer-reviewed

    Keisuke Kasai, Akihito Suzuki, Masato Yoshida, Masataka Nakazawa

    IEICE ELECTRONICS EXPRESS　3　(22)　487-492　2006/11

    DOI： 10.1587/elex.3.487 　

    ISSN： 1349-2543

  190. A 1.54 um 13C2H2 frequency-stabilized, single-polarization fiber ring laser Peer-reviewed

    Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    European Optical Society annual meeting (EOSAM), Topical meeting on extreme optics　035　2006/10

  191. 20 Msymbol/s, 64 and 128 QAM coherent optical transmission over 525 km using heterodyne detection with frequency-stabilised laser Peer-reviewed

    M. Nakazawa, M. Yoshida, K. Kasai, J. Hongou

    ELECTRONICS LETTERS　42　(12)　710-712　2006/06

    DOI： 10.1049/el:20060646 　

    ISSN： 0013-5194

  192. An acetylene ((C2H2)-C-13) stabilized single-polarization fiber laser Peer-reviewed

    Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS　89　(10)　9-17　2006

    DOI： 10.1002/ecjb.20235 　

    ISSN： 8756-663X

  193. A (C2H2)-C-13 frequency-stabilized, polarization-maintained 1.54 mu m erbium fiber ring laser with a new feedback system Peer-reviewed

    Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    2006 OPTICAL FIBER COMMUNICATION CONFERENCE/NATIONAL FIBER OPTIC ENGINEERS CONFERENCE, VOLS 1-6　OWM4　866-868　2006

  194. 20 Msymbol/s, 128 QAM coherent Optical transmission over 500 km using heterodyne detection with frequency-stabilized laser Peer-reviewed

    Masataka Nakazawa, Masato Yoshida, Keisuke Kasai, Jumpei Hongou

    2006 European Conference on Optical Communications Proceedings, ECOC 2006　Mo4. 2. 2　2006

    DOI： 10.1109/ECOC.2006.4800895 　

  195. アセチレン(13C2H2)分子の吸収線を用いた偏波保持周波数安定化ファイバレーザ Peer-reviewed

    葛西恵介, 吉田真人, 中沢正隆

    電子情報通信学会論文誌　J-88-C　(9)　708-715　2005/09

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 1345-2827

  196. A C2H2 frequency-stabilized, single-polarization fiber laser Peer-reviewed

    Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    National Metrology Institute of Japan-Bureau International des Pois et Mesures (NMIJ-BIPM) Workshop　P-13　2005/05

  197. A C2H2 frequency-stabilized, polarization-maintained erbium fiber ring laser with no frequency modulation Peer-reviewed

    Keisuke Kasai, Masato Yoshida, Masataka Nakazawa

    European Conference on Optical Communication (ECOC)　Th1.3.5　295-296　2004/09

    DOI： 10.1109/CLEOPR.2005.1569492 　

Show all ︎Show first 5

Misc. 140

  1. 100 Gbit/s-class fully coherent mobile fronthaul transmission for 6G Invited

    Keisuke Kasai

    IRIDeS-TU –ICL/ITRI Workshop on Resilient Energy-Information & Communication Technology　2025/03

  2. オールデジタル方式による16 QAM-4,000 kmコヒーレントナイキストパルス伝送

    芹川 武貴, 吉田 真人, 廣岡 俊彦, 葛西 恵介, 中沢 正隆

    電子情報通信学会大会講演論文集 2025　2025/03

  3. IF 125 GHzにおける108 Gbit/s-64 QAM信号のSMF 10 km、無線10 mフルコヒーレント伝送

    城市知輝, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集 2025　2025/03

  4. 次世代大容量Radio Access Networkの実現に向けたフルコヒーレントモバイルフロントホール伝送技術 Invited

    葛西恵介

    光ネットワーク産業・技術研究会 第5回公開討論会　2025/03

  5. 次世代無線アクセスネットワークの実現に向けた100 Gbit/s級フルコヒーレントモバイルフロントホール伝送 Invited

    葛西恵介, 城市知輝, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会信学技報 2024　124　(331)　5-8　2025/01

  6. 小型絶対重力計TAG-1の野外観測へ向けた改良と系統誤差評価II

    新谷昌人, 風間卓仁, 西島潤, 奥野淳一, 青山雄一, 葛西恵介, 吉田真人, 坪川恒也

    日本測地学会第142回講演会 2024　2024/10

  7. 時間領域マスキングを用いた3次元量子雑音ストリーム暗号

    吉田真人、葛西恵介、廣岡俊彦、中沢正隆

    電子情報通信学会大会講演論文集 2024　2024/09

  8. IF 30 GHz における 108 Gbit/s-64 QAM 信号の SMF 10 km、無線 10 m フルコヒーレント伝送

    渡部新, 城市知輝, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集 2024　2024/09

  9. 6つのLPモードを有するフューモードファイバ中のGAWBS雑音特性

    吉田哲也, 別府翔平, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集 2024　2024/09

  10. R&D for adaptive RAN (Radio Access Network) toward 5G-advanced: Highly efficient, large capacity optical mobile fronthaul Invited

    Keisuke Kasai

    ITRI-Tohoku University-YRP R&D Workshop　2024/03

  11. 28 GHz帯光モバイルフロントホール用フルコヒーレント伝送における注入同期型ヘテロダイン方式とセルフヘテロダイン方式の性能比較

    白幡晃一, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆, 東 右一郎, 小林敏幸

    電子情報通信学会大会講演論文集 2024　2024/03

  12. 光注入同期型キャリヤ周波数変換回路を用いたIF 28 GHz帯光・無線融合フルコヒーレント伝送

    白幡晃一, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆, 東 右一郎, 小林敏幸

    電子情報通信学会 信学技報　123　(330)　31-36　2024/01

  13. 小型絶対重力計TAG-1の野外観測へ向けた改良と系統誤差評価

    新谷昌人, 風間卓仁, 西島潤, 奥野淳一, 青山雄一, 土井浩一郎, 葛西恵介, 吉田真人, 坪川恒也

    日本測地学会第140回講演会　2023/10

  14. フューモードファイバ中のGAWBS雑音特性

    吉田真人, 平井孝明, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集 2023　2023/09

  15. 28GHz帯マイクロストリップアレイアンテナを用いた16Gbits-256QAM信号のSMF10km、無線10mフルコヒーレント伝送

    白幡晃一, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆, 東 右一郎, 小林敏幸

    電子情報通信学会大会講演論文集 2023　2023/09

  16. デジタルコヒーレント光伝送技術のBeyond 5Gモバイルフロントホールへの応用 Invited

    葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会誌　196　(6)　463-469　2023/06

  17. 無線IQ直接デジタルコヒーレント伝送方式における無線・光一括FECの評価

    松尾英範, 高橋 領, 牟田竜二, 松川潤也, 小杉正憲, 外山隆行, 葛西恵介, 中沢正隆

    電子情報通信学会大会講演論文集 2023　2023/03

  18. MFHにおける無線IQ直接デジタルコヒーレント伝送方式の提案

    葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆, 松尾英範, 高橋領

    電子情報通信学会大会講演論文集 2023　2023/03

  19. 28 GHz帯フェーズドアレイマイクロストリップアンテナを用いた光・無線融合フルコヒーレント伝送

    佐藤大晟, 葛西恵介, 白幡晃一, 吉田真人, 廣岡俊彦, 中沢正隆, 東右一郎, 小林 敏幸

    電子情報通信学会大会講演論文集 2023　2023/03

  20. 28 GHz帯マイクロストリップアンテナを用いた光・無線融合フルコヒーレント伝送

    葛西恵介, 佐藤大晟, 白幡晃一, 吉田真人, 廣岡俊彦, 中沢正隆, 東右一郎, 小林 敏幸

    電子情報通信学会アンテナ・伝搬研究会, 信学技法, 2023　AP2022　(229)　178-183　2023/01

  21. 小型絶対重力計TAG-1を用いた低温野外環境における連続重力観測

    新谷昌人, 岡 大輔, 風間卓仁, 西島 潤, 服部晃久, 福田洋一, 奥野淳一, 青山雄一, 土井浩一郎, 葛西恵介, 坪川恒也

    日本測地学会第138回講演会, 2022　2022/10

  22. Low power consumption, large capacity optical access technology toward realization of a green society

    Keisuke Kasai

    18th International Conference on IP/IoT_&_Processing + Optical Network (iPOP2022)　2022/06

  23. Performance comparison of injection-locked carrier frequency conversion and self-heterodyne detection methods in cohelently-linked optical and wireless transmission

    佐藤大晟, 佐藤大晟, 白幡晃一, 白幡晃一, 葛西恵介, 廣岡俊彦, 吉田真人, 中沢正隆

    電子情報通信学会技術研究報告(Web)　121　(320(OCS2021 33-40))　2022

    ISSN： 2432-6380

  24. Digital Coherent Optical Access Technology

    Keisuke Kasai

    17th International Conference on IP/IoT & Processing + Optical Network (iPOP2021)　2021/09

  25. 自己光帰還法を用いた高出力・狭線幅フルC帯波長可変LD Invited

    葛西恵介, 中沢正隆

    電子情報通信学会大会講演論文集 2021　2021/09

  26. Performance comparison between Fabry-Perot LD based- and ECLD based-injection-locking circuits

    葛西恵介, 管貴志, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集　2021　2021

    ISSN： 1349-144X

  27. Recent Progress in Carrier Down-Conversion Devices Between Optical Communication and Beyond 5G Wireless Communication

    佐藤昭, 佐藤昭, 中嶋大, 中嶋大, 西村和樹, 西村和樹, 細谷友崇, 細谷友崇, 細谷友崇, 岩月勝美, 末光哲也, 末光哲也, 葛西恵介, 葛西恵介, 吉田真人, 吉田真人, 尾辻泰一, 尾辻泰一

    電子情報通信学会技術研究報告(Web)　121　(309(ED2021 48-61))　2021

    ISSN： 2432-6380

  28. Study on Chromatic Dispersion Dependence of GAWBS Noise

    佐藤耕造, 管貴志, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2021　2021

    ISSN： 1349-144X

  29. BER performance improvement of ultrahigh-speed coherent Nyquist pulse transmission using low-nonlinearity, dispersion-compensated transmission line with chirped FBG and LCoS

    木村光佑, 木村光佑, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会技術研究報告(Web)　121　(18(OFT2021 1-11))　2021

    ISSN： 2432-6380

  30. Precise and Wideband Compensation of WDM Inter-Channel Cross-Phase Modulation Noise Using Injection Locking

    管貴志, 佐藤耕造, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2021　2021

    ISSN： 1349-144X

  31. Low-Nonlinearity, Dispersion-Compensated Transmission Line with a Chirped Fiber Bragg Grating and LCoS and Its Application to Ultrahigh-Speed Coherent Nyquist Pulse Transmission

    岩屋太郎, 木村光佑, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2021　2021

    ISSN： 1349-144X

  32. Toward optical and wireless convergence with coherently-linked access network

    廣岡俊彦, 葛西恵介, 吉田真人, 中沢正隆

    電子情報通信学会技術研究報告(Web)　120　(341(SR2020 47-59))　2021

    ISSN： 2432-6380

  33. Study on chromatic dispersion dependence of GAWBS noise

    佐藤耕造, 管貴志, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会技術研究報告(Web)　120　(309(OCS2020 27-39))　2021

    ISSN： 2432-6380

  34. 10 GHz, 6.2 ps transform-limited coherent optical pulse generation from a 1.5 μm, self-injection gain-switched DFB-LD

    葛西恵介, 中沢正隆

    電子情報通信学会大会講演論文集　2020　2020/09

    ISSN： 1349-144X

  35. Next Generation C-RAN Mobile Fronthaul Using On-line Bi-directional 256 QAM WDM Coherent Transmission

    管貴志, 吉田真人, 葛西恵介, 廣岡俊彦, 岩月勝美, 中沢正隆

    電子情報通信学会技術研究報告　119　(366(OCS2019 65-77)(Web))　2020

    ISSN： 0913-5685

  36. R&D of Technology for High Reliability Management of Advanced 5G Network to Various Requirements of Communication Services

    村上隆秀, 新保宏之, 塚本優, 難波忍, 岸洋司, 玉井森彦, 横山浩之, 原郁紀, 石橋功至, 津田顕祐, 藤井義巳, 安達文幸, 葛西惠介, 中沢正隆, 関裕太, 外山隆行

    電子情報通信学会技術研究報告　119　(448(RCS2019 320-408)(Web))　2020

    ISSN： 0913-5685

  37. Effect of GAWBS Depolarization Noise on Digital Coherent Optical Transmission

    竹節直也, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2020　2020

    ISSN： 1349-144X

  38. A proposal on optical-wireless mobile fronthaul for advanced 5G

    中沢正隆, 葛西恵介, 吉田真人, 廣岡俊彦, 岩月勝美

    電子情報通信学会大会講演論文集(CD-ROM)　2020　2020

    ISSN： 1349-144X

  39. Single-channel 15.3 Tbit/s, 64 QAM coherent Nyquist pulse transmission over 150 km

    木村光佑, 吉田真人, 岩屋太郎, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2020　2020

    ISSN： 1349-144X

  40. 10 Tbit/s QAM quantum noise stream cipher coherent transmission over 160 km

    吉田真人, 管貴志, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2020　2020

    ISSN： 1349-144X

  41. Experimental and theoretical analyses of GAWBS phase noise in multi-core fibers for digital coherent transmission

    吉田真人, 竹節直也, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会技術研究報告(Web)　120　(140(OCS2020 4-7))　2020

    ISSN： 2432-6380

  42. 160 Gbit/s, 256 QAM bidirectional coherent transmission for mobile fronthaul without backward Rayleigh scattering interference

    葛西恵介, 吉田真人, 廣岡俊彦, 岩月勝美, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2020　2020

    ISSN： 1349-144X

  43. Experimental and theoretical analyses of GAWBS noise in multi-core fiber

    吉田真人, 竹節直也, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2020　2020

    ISSN： 1349-144X

  44. GAWBS noise characteristics in digital coherent transmission in various optical fibers

    竹節直也, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会技術研究報告　119　(93(OCS2019 10-19)](Web))　2019

    ISSN： 0913-5685

  45. 50.4 Tbit/s, L-band 480 ch-WDM, 128 QAM-160 km Digital Coherent Optical Transmission Using an Injection-locked Homodyne Receiver

    管貴志, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会技術研究報告　119　(93(OCS2019 10-19)](Web))　2019

    ISSN： 0913-5685

  46. 通信波長帯光源を用いた小型絶対重力計TAG-1の運用と系統誤差評価

    新谷昌人, 葛西恵介, 吉田真人, 中沢正隆, 田村良明, 坪川恒也

    日本測地学会講演会要旨　132nd　2019

  47. 次世代モバイルフロントホール用256QAMオンライン双方向コヒーレント伝送

    吉田真人, 管貴志, 葛西恵介, 廣岡俊彦, 岩月勝美, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2019　2019

    ISSN： 1349-144X

  48. リアルタイム偏波多重256~512QAMデジタルコヒーレント光伝送

    吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2019　2019

    ISSN： 1349-144X

  49. 256QAM WDMオンライン双方向コヒーレント伝送を用いた次世代C-RANモバイルフロントホール

    管貴志, 吉田真人, 葛西恵介, 廣岡俊彦, 岩月勝美, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2019　2019

    ISSN： 1349-144X

  50. デジタルコヒーレント光伝送における各種ファイバのGAWBS雑音特性

    竹節直也, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2019　2019

    ISSN： 1349-144X

  51. 注入同期法を用いた200Gbit/s,10Gsymbol/s-1024QAM160kmデジタルコヒーレント光伝送

    葛西恵介, 岡本聖司, 吉田真人, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2019　2019

    ISSN： 1349-144X

  52. 高精度光位相制御技術を用いた超多値QAMコヒーレント光伝送

    吉田真人, 葛西恵介, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2019　2019

    ISSN： 1349-144X

  53. 50.4Tbit/s,L-band WDM128QAM-160kmコヒーレント光伝送

    管貴志, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2019　2019

    ISSN： 1349-144X

  54. 線幅8kHz,C+Lバンド波長可変LDの波長可変特性

    葛西恵介, 中沢正隆, 友松泰則, 遠藤尚

    電子情報通信学会大会講演論文集(CD-ROM)　2019　2019

    ISSN： 1349-144X

  55. 10ペタビット級光伝送実験の成功 (特集 空間分割多重光通信技術の進展)

    相馬 大樹, 若山 雄太, 別府 翔平, 角田 聖也, 釣谷 剛宏, 林 哲也, 永島 拓志, 鈴木 雅人, 吉田 真人, 葛西 恵介, 中沢 正隆, 高橋 英憲, 五十嵐 浩司, 森田 逸郎, 鈴木 正敏

    O plus E : Optics + electronics　40　(6)　724-728　2018/09

    Publisher: アドコム・メディア

    ISSN： 0911-5943

  56. 80 Gbit/s, 256 QAM Digital Coherent Optical Transmission with Injection-Locking for Next Generation Mobile Fronthaul

    117　(423)　19-24　2018/01/29

    Publisher: 電子情報通信学会

    ISSN： 0913-5685

  57. 単一チャンネル7.68Tbit/s-150km,64QAMコヒーレントナイキストパルス伝送

    新田純平, 木村光佑, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2018　2018

    ISSN： 1349-144X

  58. 4096QAM(72Gbit/s)-160kmディジタルコヒーレント光伝送

    寺山雅樹, 岡本聖司, 葛西恵介, 吉田真人, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2018　2018

    ISSN： 1349-144X

  59. 光注入同期法を用いた次世代モバイルフロントホール用160Gbit/s,256QAMデジタルコヒーレント伝送

    葛西恵介, WANG Yixin, 吉田真人, 廣岡俊彦, 岩月勝美, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2018　2018

    ISSN： 1349-144X

  60. 注入同期法を用いた12bit/s/Hz,58.2Tbit/s,256QAM-160km CバンドWDM伝送

    管貴志, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2018　2018

    ISSN： 1349-144X

  61. GAWBS位相雑音補償による1024QAMコヒーレント光伝送におけるエラーフロアの抑制

    吉田真人, 竹節直也, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2018　2018

    ISSN： 1349-144X

  62. 自己光帰還法を用いた線幅8kHz,出力50mW,C帯波長可変DFB LD

    葛西恵介, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2018　2018

    ISSN： 1349-144X

  63. Oscillation characteristics of a narrow linewidth DFB LD array with an optical feedback method

    葛西恵介, 中沢正隆

    電子情報通信学会技術研究報告　118　(186(EMD2018 20-36))　2018

    ISSN： 0913-5685

  64. PS-4096QAM信号と1024QAM信号の160km伝送特性比較

    岡本聖司, 岡本聖司, 寺山雅樹, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2018　2018

    ISSN： 1349-144X

  65. 空間分割多重光通信技術の進展 10ペタビット級光伝送実験の成功

    相馬大樹, 若山雄太, 別府翔平, 角田聖也, 釣谷剛宏, 林哲也, 永島拓志, 鈴木雅人, 吉田真人, 葛西恵介, 中沢正隆, 高橋英憲, 五十嵐浩司, 五十嵐浩司, 森田逸郎, 鈴木正敏

    O plus E　(463)　2018

    ISSN： 0911-5943

  66. 12 bit/s/Hz, 58.2 Tbit/s, 256 QAM-160 km C-band WDM Transmission Using an Injection Locking Technique

    管貴志, 葛西恵介, 吉田真人, 廣岡俊彦, 中沢正隆

    電子情報通信学会技術研究報告　118　(238(OFT2018 13-51)(Web))　2018

    ISSN： 0913-5685

  67. Observation of GAWBS Noise and Development of its Compensation Technique in Digital Coherent Optical Transmission

    竹節直也, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会技術研究報告　118　(238(OFT2018 13-51)(Web))　2018

    ISSN： 0913-5685

  68. Single-channel 7.68 Tbit/s, 64 QAM coherent Nyquist pulse transmission over 150 km with a spectral efficiency of 9.7 bit/s/Hz

    木村光佑, 新田純平, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会技術研究報告　118　(238(OFT2018 13-51)(Web))　2018

    ISSN： 0913-5685

  69. A full C-band wavelength tunable laser diode with narrow linewidth and low intensity noise characteristics

    葛西恵介, 中沢正隆, 友松泰則, 遠藤尚

    電子情報通信学会技術研究報告　117　(194(OPE2017 48-67))　2017

    ISSN： 0913-5685

  70. 単一チャネル3.84Tbit/s,64QAMコヒーレントナイキストパルス信号の150km伝送

    新田純平, 木村光佑, 吉田真人, 葛西恵介, 廣岡俊彦, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2017　2017

    ISSN： 1349-144X

  71. 光注入同期を用いた42.3Tbit/s,C-band WDM64QAM-160kmコヒーレント伝送

    管貴志, 葛西恵介, 吉田真人, 中沢正隆

    電子情報通信学会大会講演論文集(CD-ROM)　2017　2017

    ISSN： 1349-144X

  72. 光ファイバーネットワークを利用した地殻変動

    中沢 正隆, 吉田 真人, 葛西 恵介

    光技術コンタクト　54　(12)　22-31　2016/12/20

    Publisher: 一般社団法人日本オプトメカトロニクス協会

    ISSN： 0913-7289

  73. High Spectral Efficient Transmission with Digital Coherent Ultra-multilevel QAM Format

    45　(12)　466-471　2016/12

    Publisher: 日本光学会

    ISSN： 0389-6625

  74. C-4-12 295 mW output, HCN frequency-stabilized CW erbium fiber ring laser

    Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2016　(1)　216-216　2016/03/01

    Publisher: The Institute of Electronics, Information and Communication Engineers

  75. B-10-52 320 Gbit/s, 256 QAM Coherent Optical Transmission over 160 km with an LD-based Injection-locked Homodyne Receiver

    Wang Yixin, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2016　(2)　345-345　2016/03/01

    Publisher: The Institute of Electronics, Information and Communication Engineers

  76. B-10-38 Real-time adaptive 4-64 QAM, 20-60 Gbit/s quantum noise stream cipher transmission

    Nakazawa Masataka, Yoshida Masato, Hirooka Toshihiko, Kasai Keisuke

    Proceedings of the IEICE General Conference　2016　(2)　331-331　2016/03/01

    Publisher: The Institute of Electronics, Information and Communication Engineers

  77. 狭線幅レーザーとOPLL(Optical Phase-Locked Loop)及び光注入同期を用いた超多値ディジタルコヒーレント伝送

    葛西恵介, 中沢正隆

    レーザー研究　44　(2)　106-110　2016/02

    Publisher: レーザー学会

    ISSN： 0387-0200

  78. B-10-43 80 Gbit/s, 256 QAM Coherent Optical Transmission over 150 km with an LD-based Injection-locked Homodyne Receiver

    Wang Yixin, Kasai Keisuke, Beppu Shohei, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2015　(2)　207-207　2015/08/25

    Publisher: The Institute of Electronics, Information and Communication Engineers

  79. B-10-45 448 Gbit/s, 32 Gbaud 128 QAM coherent transmission over 150 km with a potential spectral efficiency of 10.7 bit/s/Hz

    Kasai Keisuke, Wang Yixin, Otuya David Odeke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2015　(2)　209-209　2015/08/25

    Publisher: The Institute of Electronics, Information and Communication Engineers

  80. B-10-44 120 Gbil/s polarization-multiplexed 64 QAM digital coherent transmission in a deployed ROADM network

    Hirooka Toshihiko, Kasai Keisuke, Wang Yixin, Nakazawa Masataka, Shiraiwa Masaki, Awaji Yoshinari, Wada Naoya

    Proceedings of the Society Conference of IEICE　2015　(2)　208-208　2015/08/25

    Publisher: The Institute of Electronics, Information and Communication Engineers

  81. B-10-50 1024 QAM, 7-core (60 Gbit/s x 7) fiber transmission over 55 km with an aggregate spectral efficiency of 109 bit/s/Hz

    Yoshida Masato, Beppu Shohei, Kasai Keisuke, Hirooka Toshihiko, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2015　(2)　214-214　2015/08/25

    Publisher: The Institute of Electronics, Information and Communication Engineers

  82. B-10-57 QAM quantum noise stream cipher using digital coherent optical transmission

    Nakazawa Masataka, Yoshida Masato, Hirooka Toshihiko, Kasai Keisuke

    Proceedings of the Society Conference of IEICE　2015　(2)　221-221　2015/08/25

    Publisher: The Institute of Electronics, Information and Communication Engineers

  83. 1.92 Tbit/s/ch, 64 QAM coherent Nyquist orthogonal TDM transmission with a spectral efficiency of 10.6 bit/s/Hz (光通信システム)

    OTUYA David Odeke, 原子 広大, 葛西 恵介

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報　115　(165)　7-12　2015/07/30

    Publisher: 電子情報通信学会

    ISSN： 0913-5685

  84. B-10-26 1.92 Tbit/s/ch, 64 QAM coherent Nyquist pulse transmission with a spectral efficiency of 10.6 bit/s/Hz

    Otuya David Odeke, Harako Koudai, Kasai Keisuke, Hirooka Toshihiko, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2015　(2)　362-362　2015/02/24

    Publisher: The Institute of Electronics, Information and Communication Engineers

  85. Recent development of ultra-multilevel digital coherent QAM transmission

    33　(12)　40-44　2014/12

    Publisher: オプトロニクス社

    ISSN： 0286-9659

  86. High-performance TDM demultiplexing of coherent Nyquist pulses using time-domain orthogonality

    HARAKO Koudai, OTUYA David Odeke, KASAI Keisuke, HIROOKA Toshihiko, NAKAZAWA Masataka

    Technical report of IEICE. OCS　114　(281)　97-100　2014/10/30

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

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    We propose a simple and high-performance scheme for demultiplexing coherent Nyquist TDM signals by photo-mixing on a photo-detector with Nyquist LO pulses. This scheme takes advantage of the time-domain orthogonality of Nyquist pulses, which enables high-SNR demultiplexing and homodyne detection simultaneously in spite of a strong overlap with adjacent pulses in the time domain. The feasibility of this scheme is demonstrated through a demultiplexing experiment employing 80 Gbaud, 64 QAM Nyquist pulse OTDM signals. This scheme exhibits excellent demultiplexing performance with a much simpler configuration than a conventional ultrafast all-optical sampling scheme.

  87. B-10-43 2048 QAM (66 Gbit/s) Digital Coherent Optical Transmission over 150 km

    Beppu Shohei, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2014　(2)　411-411　2014/03/04

    Publisher: The Institute of Electronics, Information and Communication Engineers

  88. A report on demodulation characteristics of a 20Gb/s-QPSK signal with a digital-based optical phase-locked loop

    Fujii Akihiro, Shirazawa Futoshi, Kasai Keisuke, Kanda Yoshihiro, Murai Hitoshi, Yun Set Sze

    Proceedings of the Society Conference of IEICE　2013　(2)　350-350　2013/09/03

    Publisher: The Institute of Electronics, Information and Communication Engineers

  89. A 120 Gbit/s, 64 QAM coherent transmission over 150 km employing an optical voltage controlled oscillator

    Wang Yixin, Kasai Keisuke, Omiya Tatsunori, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2013　(2)　243-243　2013/09/03

    Publisher: The Institute of Electronics, Information and Communication Engineers

  90. 光多値化技術とさらなる周波数利用効率の向上にむけて

    中沢正隆, 廣岡俊彦, 吉田真人, 葛西恵介

    O pulse E　35　(8)　836-841　2013

    Publisher: アドコムメディア

    ISSN： 0911-5943

  91. B-10-90 An LD-based optical phase-locked loop circuit by using an optical voltage controlled oscillator

    Kasai Keisuke, Wang Yixin, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2012　(2)　272-272　2012/08/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

  92. 32 RZ/QAM coherent optical transmission employing an RZ-CW conversion technique

    KASAI Keisuke, OTUYA David Odeke, YOSHIDA Masato, HIROOKA Toshihiko, NAKAZAWA Masataka

    Technical report of IEICE. OCS　112　(152)　13-18　2012/07/19

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

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    Coherent optical time division multiplexing (OTDM) transmission with a multi-level modulation format has attracted a lot of attention as a ultra-high speed and highly spectral-efficient optical transmission system. However, in the conventional coherent OTDM, it is difficult to demodulate an ultra-high speed, multi-level RZ data signal with a high signal to noise ratio due to input optical power limitation of coherent detection circuits. Recently, we proposed a demodulation scheme by using an RZ-CW conversion scheme in a coherent receiver, in which the transmitted coherent RZ data are OTDM demultiplexed and converted into a data signal on a CW carrier. In this paper, we demonstrate an advantage of the scheme with 10 Gsymbol/s, 4- and 8-OTDM 32 RZ/QAM demodulation experiments. Furthermore, we have successfully transmitted a polarization multiplexed, 10 Gsymbol/s, 32 RZ/QAM (800 Git/s) data signal over 225 km by using this conversion scheme.

  93. B-10-54 Single-channel 800 Gbit/s, 32 RZ/QAM coherent transmission employing an RZ-CW conversion technique

    Kasai Keisuke, Odeke Otuya David, Yoshida Masato, Hirooka Toshihiko, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2012　(2)　377-377　2012/03/06

    Publisher: The Institute of Electronics, Information and Communication Engineers

  94. B-10-50 120 Gbit/s, 64 QAM Coherent Transmission over 150 km with OPLL Employing Narrow Linewidth LDs

    Wang Yixin, Kasai Keisuke, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2011　(2)　263-263　2011/08/30

    Publisher: The Institute of Electronics, Information and Communication Engineers

  95. BCI-1-1 A precision optical phase-locked loop technique for ultra multi-level coherent transmission

    Kasai Keisuke

    Proceedings of the Society Conference of IEICE　2011　(1)　"SS-27"-"SS-28"　2011/08/30

    Publisher: The Institute of Electronics, Information and Communication Engineers

  96. Oscillation characteristics of an ^<13>C_2H_2 frequency-stabilized λ/4-shifted DFB LD with an external fiber ring cavity

    KASAI Keisuke, NAKAZAWA Masataka

    IEICE technical report　111　(185)　49-52　2011/08/18

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

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    We demonstrate frequency stabilization of a λ/4-shifted distributed feedback laser diode (DFB LD) with an external fiber ring cavity to an ^<13>C_2H_2 (acetylene) linear absorption line. By employing a feedback control of the λ/4-shifted DFB passband to track one Fabry-Perot mode associated with the fiber ring cavity, we have successfully tuned an oscillation frequency over 1.2 GHz without mode-hopping. The optical frequency was stabilized to a ^<13>C_2H_2 absorption line with an external frequency modulation scheme, which realizes an FM-eliminated output beam. The frequency stabilities reached as high as 1.4×10^<-10> for τ=1 s and 1.3×10^<-11> for τ=100 s. Furthermore, a linewidth of 2.6 kHz and a relative intensity noise of less than -135 dB/Hz were simultaneously achieved.

  97. Development of FPGA-based real-time receiver for 64 QAM coherent signals

    YOSHIDA Masato, OMIYA Tatsunori, KASAI Keisuke, NAKAZAWA Masataka

    IEICE technical report　111　(122)　7-12　2011/07/04

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

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    We demonstrate the first real-time coherent optical transmission of a 1 Gsymbol/s, 64 QAM data signal. The real-time coherent receiver consists of four 1 GS/s analog-to-digital converters (ADC) and a field-programmable gate array (FPGA) implementation. The bit error rate (BER) performance obtained with the real-time receiver is the same as that obtained with an off-line digital signal processor (DSP). This result indicates that the phase of the IF signal and the data clock timing are precisely controlled without any DSP compensations in our real-time coherent transmission system. As a result, an error free performance (BER < 1 x 10<-12>) has been achieved under a back-to-back condition.

  98. Frequency Division Multiplexing 64 QAM-OFDM (420 Gb/s) transmission over 160 km

    OMIYA Tatsunori, TOYODA Kazushi, KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    IEICE technical report　111　(122)　93-98　2011/07/04

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

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    We have demonstrated 64QAM-OFDM coherent optical transmission with a C_2H_2 frequency-stabilized fiber laser and an optical phase-locked loop (OPLL) circuit. In this report, we describe experimental result of 7ch-frequency-division-multiplexed and polarization-multiplexed 5 Gsymbol/s 64 QAM-OFDM (420 Gb/s) transmission. After 160 km transmission, we applied compensation for impairments due to fiber nonlinearity by using back propagation method and improved the bit error rate (BER) performance. As a result, a BER below the forward error correction (FEC) limit and a spectral efficiency as high as 10.4 b/s/Hz were successfully demonstrated.

  99. B-10-82 640 Gbit/s Clock Recovery Using Time-Domain Optical Fourier Transformation and Narrow-Band Optical Filter

    Guan Pengyu, Mulvad Hans Christian Hansen, Kasai Keisuke, Hirooka Toshihiko, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2011　(2)　391-391　2011/02/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

  100. B-10-39 512 QAM (54 Gbit/s) coherent optical transmission over 150 km

    Okamoto Seiji, Toyoda Kazushi, Omiya Tatsunori, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2011　(2)　348-348　2011/02/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

  101. BCI-1-1 Ultra-Multilevel Coherent QAM Transmission Toward Peta・Exa-bit Era

    Kasai Keisuke

    Proceedings of the Society Conference of IEICE　2010　(1)　"SS-1"-"SS-2"　2010/08/31

    Publisher: The Institute of Electronics, Information and Communication Engineers

  102. Single-channel 400Gbit/s, OTDM-32 RZ/QAM coherent transmission over 225km

    KASAI Keisuke, OMIYA Tatsunori, GUAN Pengyu, YOSHIDA Masato, HIROOKA Toshihiko, NAKAZAWA Masataka

    IEICE technical report　110　(94)　1-6　2010/06/17

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    Coherent optical time division multiplexing (OTDM) transmission with a multi-level modulation format based on digital signal processing (DSP) has attracted a lot of attention with a view to expanding the capacity per channel of wavelength division multiplexing (WDM) transmission systems. This transmission system can overcome the speed and bandwidth limitations of electrical components such as A/D and D/A converters and realize ultrahigh-speed coherent transmission by using a multi-level amplitude and phase-modulated coherent RZ pulse and the OTDM. However, in a conventional coherent OTDM system, the optical phase between an RZ data pulse and a local oscillator are not phase-locked. Therefore, it is difficult to realize a coherent OTDM transmission with high multiplicity. In this work, we demonstrated a multi-level coherent OTDM transmission with a high-precision optical phase-locked loop (OPLL) technique by using optical comb generation circuits. 400 Gbit/s data (polarization-multiplexed, 10 Gsymbol/s, 4-OTDM 32 RZ/QAM) were successfully transmitted over 225 km with a bit error rate performance below the forward error correction (FEC) limit. We also realized a 320 Gbit/s-450 km transmission with an OTDM 16 RZ/QAM scheme.

  103. CS-6-3 Frequency-stabilized lasers and an optical phase-lock technique for ultra-multilevel coherent transmission

    Kasai Keisuke, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2010　(2)　"S-33"-"S-34"　2010/03/02

    Publisher: The Institute of Electronics, Information and Communication Engineers

  104. B-10-62 Optical phase-locked loop for coherent OTDM transmission with an optical comb technique

    Yoshida Masato, Kasai Keisuke, Omiya Tatsunori, Guan Pengyu, Hirooka Toshihiko, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2010　(2)　400-400　2010/03/02

    Publisher: The Institute of Electronics, Information and Communication Engineers

  105. B-10-82 Single-channel 400Gbit/s, OTDM-32 RZ/QAM coherent transmission over 225 km

    Kasai Keisuke, Omiya Tatsunori, Guan Pengyu, Yoshida Masato, Hirooka Toshihiko, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2010　(2)　420-420　2010/03/02

    Publisher: The Institute of Electronics, Information and Communication Engineers

  106. B-10-83 10 Gsymbol/s, 128 QAM (140 Gbit/s) coherent optical transmission over 150km

    Okamoto Seiji, Omiya Tatsunori, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2010　(2)　421-421　2010/03/02

    Publisher: The Institute of Electronics, Information and Communication Engineers

  107. B-10-84 256 QAM (64 Gbit/s) coherent optical transmission over 160km

    Nakazawa Masataka, Okamoto Seiji, Omiya Tatsunori, Kasai Keisuke, Yoshida Masato

    Proceedings of the IEICE General Conference　2010　(2)　422-422　2010/03/02

    Publisher: The Institute of Electronics, Information and Communication Engineers

  108. B-10-40 Polarization and frequency division multiplexed 1 Gsymbol/s, 64 QAM coherent optical transmission with 8.6 bit/s/Hz spectral efficiency over 160 km

    Goto Hiroki, Omiya Tatsunori, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2009　(2)　220-220　2009/09/01

    Publisher: The Institute of Electronics, Information and Communication Engineers

  109. B-10-41 5 Gsymbol/s, 64 QAM-OFDM(30 Gbit/s) coherent optical transmission

    Omiya Tatsunori, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2009　(2)　221-221　2009/09/01

    Publisher: The Institute of Electronics, Information and Communication Engineers

  110. A 0.4GHz ultranarrow FBG optical filter with 30-dB side lobe suppression

    MORI Anne, KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    IEICE technical report　109　(179)　63-68　2009/08/20

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

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    A fiber Bragg grating (FBG) is an attractive optical filter device because of its narrow wavelength selectivity, low loss, compactness, and low cost. Therefore, it is useful for applications such as coherent optical communication systems, optical sensing and optical metrological standard. These applications require both a narrow bandwidth and a high side lobe suppression ratio. We have already demonstrated a 1.3GHz ultranarrow FBG filter with a side lobe suppression ratio of 13dB. In this paper, we report a 0.4GHz FBG filter with a side lobe suppression ratio as high as 30dB by combining a uniform FBG and a λ/4 shifted FBG.

  111. Oscillation characteristics of a 1.5μm FM-eliminated ^<13>C_2H_2 frequency-stabilized laser diode

    KASAI Keisuke, NAKAZAWA Masataka

    IEICE technical report　109　(174)　73-76　2009/08/13

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

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    We demonstrate the frequency stabilization of a 1.5μm laser diode (LD) with a low intensity noise and a narrow linewidth to a ^<13>C_2H_2 linear absorption line. The LD consists of an InP gain chip and an external Bragg reflector made of a PLC waveguide. By employing an external frequency modulator in a frequency stabilization circuit, an FM-eliminated optical output beam was obtained. The frequency stabilities reached as high as 2.3×10^<-11> for τ=1s and 9.1×10^<-12> for τ=100s. Furthermore, a RIN of less than -135dB/Hz, and a linewidth of 4kHz were simultaneously achieved.

  112. Optical frequency-stabilized and 40GHz repetition-rate-stabilized, regeneratively mode-locked pulse laser

    YOSHIDA Masato, KASAI Keisuke, NAKAZAWA Masataka

    IEICE technical report　109　(174)　97-102　2009/08/13

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    Ultrastable mode-locked pulse lasers operating in the GHz region have been receiving a lot of attention with respect to their application to both ultrahigh-speed optical transmission, micro-photonics and optical metrology. In particular, control of the laser frequency is very important for optical coherent communication and optical metrology applications. In this paper, we have succeeded in the simultaneous stabilization of the optical frequency and repetition rate of a 40GHz regeneratively mode-locked picosecond erbium-doped fiber ring laser. The optical frequency was locked to the molecular absorption of C_2H_2 in the 1.5μm band and the repetition rate was stabilized to a 40GHz synthesizer by using a microwave phase-locked loop.

  113. Optical frequency-stabilized and 40GHz repetition-rate-stabilized, regeneratively mode-locked pulse laser

    YOSHIDA Masato, KASAI Keisuke, NAKAZAWA Masataka

    IEICE technical report　109　(173)　97-102　2009/08/13

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    Ultrastable mode-locked pulse lasers operating in the GHz region have been receiving a lot of attention with respect to their application to both ultrahigh-speed optical transmission, micro-photonics and optical metrology. In particular, control of the laser frequency is very important for optical coherent communication and optical metrology applications. In this paper, we have succeeded in the simultaneous stabilization of the optical frequency and repetition rate of a 40GHz regeneratively mode-locked picosecond erbium-doped fiber ring laser. The optical frequency was locked to the molecular absorption of C_2H_2 in the 1.5μm band and the repetition rate was stabilized to a 40GHz synthesizer by using a microwave phase-locked loop.

  114. Optical frequency-stabilized and 40GHz repetition-rate-stabilized, regeneratively mode-locked pulse laser

    YOSHIDA Masato, KASAI Keisuke, NAKAZAWA Masataka

    IEICE technical report　109　(175)　97-102　2009/08/13

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    Ultrastable mode-locked pulse lasers operating in the GHz region have been receiving a lot of attention with respect to their application to both ultrahigh-speed optical transmission, micro-photonics and optical metrology. In particular, control of the laser frequency is very important for optical coherent communication and optical metrology applications. In this paper, we have succeeded in the simultaneous stabilization of the optical frequency and repetition rate of a 40GHz regeneratively mode-locked picosecond erbium-doped fiber ring laser. The optical frequency was locked to the molecular absorption of C_2H_2 in the 1.5μm band and the repetition rate was stabilized to a 40GHz synthesizer by using a microwave phase-locked loop.

  115. Optical frequency-stabilized and 40GHz repetition-rate-stabilized, regeneratively mode-locked pulse laser

    YOSHIDA Masato, KASAI Keisuke, NAKAZAWA Masataka

    IEICE technical report　109　(176)　97-102　2009/08/13

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    Ultrastable mode-locked pulse lasers operating in the GHz region have been receiving a lot of attention with respect to their application to both ultrahigh-speed optical transmission, micro-photonics and optical metrology. In particular, control of the laser frequency is very important for optical coherent communication and optical metrology applications. In this paper, we have succeeded in the simultaneous stabilization of the optical frequency and repetition rate of a 40GHz regeneratively mode-locked picosecond erbium-doped fiber ring laser. The optical frequency was locked to the molecular absorption of C_2H_2 in the 1.5μm band and the repetition rate was stabilized to a 40GHz synthesizer by using a microwave phase-locked loop.

  116. 64 QAM-OFDM coherent optical transmission

    OMIYA Tatsunori, GOTO Hiroki, KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    IEICE technical report　109　(31)　1-6　2009/05/08

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    Recently, Orthogonal Frequency Division Multiplexing (OFDM) system, that was originally developed in wireless communication, has been intensively studied in optical communication. The multi-carrier transmission of low-speed orthogonal subcarriers enables us to improve both spectral efficiency and dispersion tolerance by adopting high-level subcarrier modulation formats and employing coherent detection in OFDM. So far, 1 Tb/s per channel OFDM transmission and OFDM optical coherent transmission with 32 QAM subcarrier modulation have been reported. In this report, we realize, for the first time, QAM subcarrier modulation up to 64 levels using 128 subcarriers and demonstrate OFDM transmission over a 160km.

  117. C-3-3 A 0.4 GHz ultranarrow FBG optical filter with 30-dB side lobe suppression

    Mori Anne, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2009　(1)　154-154　2009/03/04

    Publisher: The Institute of Electronics, Information and Communication Engineers

  118. B-10-50 1 Gsymbol/s, 6-channel frequency division multiplexed 64 QAM coherent optical transmission

    Goto Hiroki, Okamoto Seiji, Omiya Tatsunori, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2009　(2)　369-369　2009/03/04

    Publisher: The Institute of Electronics, Information and Communication Engineers

  119. B-10-49 12 Gbit/s, 64 QAM-OFDM coherent optical transmission

    Omiya Tatsunori, Goto Hiroki, Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2009　(2)　368-368　2009/03/04

    Publisher: The Institute of Electronics, Information and Communication Engineers

  120. A 1.3GHz ultranarrow FBG optical filter with 20-dB side lobe suppression

    MORI Anne, KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    IEICE technical report　108　(192)　103-108　2008/08/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    A fiber Bragg grating (FBG) is an attractive optical filter device because of its narrow wavelength selectivity, low loss, compactness, and low cost. Therefore, it is useful for applications such as dense wavelength division multiplexing and coherent optical communication systems. These applications require both a narrow bandwidth and a high side lobe suppression ratio. We have already demonstrated a 1.3GHz ultranarrow FBG filter with a side lobe suppression ratio of 13dB. In this paper, we report a 1.3GHz FBG filter with a side lobe suppression ratio as high as 20dB by combining a uniform FBG and a λ/4 shifted FBG.

  121. A 1.3GHz ultranarrow FBG optical filter with 20-dB side lobe suppression

    MORI Anne, KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    IEICE technical report　108　(193)　103-108　2008/08/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    A fiber Bragg grating (FBG) is an attractive optical filter device because of its narrow wavelength selectivity, low loss, compactness, and low cost. Therefore, it is useful for applications such as dense wavelength division multiplexing and coherent optical communication systems. These applications require both a narrow bandwidth and a high side lobe suppression ratio. We have already demonstrated a 1.3GHz ultranarrow FBG filter with a side lobe suppression ratio of 13dB. In this paper, we report a 1.3GHz FBG filter with a side lobe suppression ratio as high as 20dB by combining a uniform FBG and a λ/4 shifted FBG.

  122. A 1.3GHz ultranarrow FBG optical filter with 20-dB side lobe suppression

    MORI Anne, KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    IEICE technical report　108　(194)　103-108　2008/08/21

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    A fiber Bragg grating (FBG) is an attractive optical filter device because of its narrow wavelength selectivity, low loss, compactness, and low cost. Therefore, it is useful for applications such as dense wavelength division multiplexing and coherent optical communication systems. These applications require both a narrow bandwidth and a high side lobe suppression ratio. We have already demonstrated a 1.3GHz ultranarrow FBG filter with a side lobe suppression ratio of 13dB. In this paper, we report a 1.3GHz FBG filter with a side lobe suppression ratio as high as 20dB by combining a uniform FBG and a λ/4 shifted FBG.

  123. A 1.3GHz ultranarrow FBG optical filter with 20-dB side lobe suppression

    MORI Anne, KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    IEICE technical report　108　(191)　103-108　2008/08/21

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    A fiber Bragg grating (FBG) is an attractive optical filter device because of its narrow wavelength selectivity, low loss, compactness, and low cost. Therefore, it is useful for applications such as dense wavelength division multiplexing and coherent optical communication systems. These applications require both a narrow bandwidth and a high side lobe suppression ratio. We have already demonstrated a 1.3GHz ultranarrow FBG filter with a side lobe suppression ratio of 13dB. In this paper, we report a 1.3GHz FBG filter with a side lobe suppression ratio as high as 20dB by combining a uniform FBG and a λ/4 shifted FBG.

  124. B-10-97 Polarization multiplexed 1 Gsymbol/s, 128 QAM coherent optical transmission

    Goto Hiroki, Kasai Keisuke, Yoshida Masato, Nakasawa Masataka

    Proceedings of the IEICE General Conference　2008　(2)　380-380　2008/03/05

    Publisher: The Institute of Electronics, Information and Communication Engineers

  125. B-10-54 1Gsymbol/s, 64QAM coherent optical transmission with a high spectral efficiency using a Nyquist filter

    Kasai Keisuke, Hongo Jumpei, Goto Hiroki, Yoshida Masato, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2007　(2)　248-248　2007/08/29

    Publisher: The Institute of Electronics, Information and Communication Engineers

  126. C-4-25 Improvement of output characteristics of an optical frequency tunable 40GHz, picosecond mode-locked fiber laser

    Yoshida Masato, Kasai Keisuke, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2007　(1)　287-287　2007/03/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  127. B-10-68 Performance of optical phase-locked loop over 500 km for coherent transmission using heterodyne detection

    Kasai Keisuke, Hongo Jumpei, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2007　(2)　407-407　2007/03/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  128. BS-7-1 Coherent QAM transmission using a frequency-stabilized laser and an optical phase-locked-loop

    Yoshida Masato, Kasai Keisuke, Hongou Jumpei, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2007　(2)　"S-47"-"S-48"　2007/03/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  129. C-4-7 Performance improvement of an acetylene(C_2H_2) frequency-stabilized fiber laser using a highly-doped EDFA

    Kasai Keisuke, Suzuki Akihito, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2006　(1)　221-221　2006/09/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  130. B-10-54 64 and 128 coherent QAM preliminary transmission experiments using a frequency-stabilized laser and a local oscillator

    Nakazawa Masataka, Hongou Jumpei, Kasai Keisuke, Yoshida Masato

    Proceedings of the Society Conference of IEICE　2006　(2)　248-248　2006/09/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  131. C-4-16 An optical frequency tunable 40GHz, picosecond mode-locked fiber laser

    Yoshida Masato, Kasai Keisuke, Nakazawa Masataka

    Proceedings of the Society Conference of IEICE　2006　(1)　230-230　2006/09/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  132. Performance improvement of an acetylene (C_2H_2) frequency-stabilized fiber laser

    KASAI Keisuke, SUZUKI Akihito, YOSHIDA Masato, NAKAZAWA Masataka

    IEICE technical report　106　(211)　57-62　2006/08/17

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    An erbium-doped fiber with high Er-ion concentration generally causes output power fluctuation and self-pulsing operation in an erbium fiber laser due to relaxation oscillation. In this report, we employed a new EDF with high Er- and Al-ion concentrations in order to suppress relaxation oscillation and increase output power of the laser. As a result, the output power was more than doubled and the power fluctuation halved. Furthermore the frequency stability of the ^<13>C_2H_2 frequency-stabilized erbium fiber laser reached as high as 1.3×10^<-11> for τ=1s and 2.0×10^<-11> for τ=10^2s. The short term stability of τ=1s was also improved.

  133. C-4-4 Characteristics of a ^<13>C_2H_2 frequency-stabilized, polarization-maintained fiber laser at 1.54μm : Measurement of frequency stability with beat note signal

    Kasai Keisuke, Yoshida Masato, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2006　(1)　248-248　2006/03/08

    Publisher: The Institute of Electronics, Information and Communication Engineers

  134. C-4-13 A C_2H_2 frequency-stabilized fiber laser with a LiNbO_3 optical frequency modulator and a PLL circuit

    Kasai Keisuke, Yoshida Masato, Nakazawa Masataka, Shiota Kazunori, Masuda Shin

    Proceedings of the Society Conference of IEICE　2005　(1)　294-294　2005/09/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  135. C-4-26 Measurement and investigation of longitudinal mode-hopping of GHz mode-locked fiber laser

    Harada Shinji, Kasai Keisuke, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2005　(1)　333-333　2005/03/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  136. C-4-28 Construction of a ^<13>C_2H_2 (acetylene) frequency-stabilized, single-polarization fiber ring laser

    Kasai Keisuke, Yoshida Masato, Nakazawa Masataka, Shiota Kazunori, Masuda Shin

    Proceedings of the IEICE General Conference　2005　(1)　335-335　2005/03/07

    Publisher: The Institute of Electronics, Information and Communication Engineers

  137. Development of a C_2H_2 (acetylene) frequency-stabilized and single-polarization fiber laser

    KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    326　111-116　2004/08/26

  138. Development of a C_2H_2 (acetylene) frequency-stabilized and single-polarization fiber laser

    KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    Technical report of IEICE. OFT　104　(262)　31-36　2004/08/20

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    A frequency-stabilized fiber ring laser using linear absorption line of acetylene molecules is described. The output beam has no frequency modulation. A Fiber Brrag Grating (FBG) with a 3.7GHz bandwidth enabled single-frequency operation by selecting only one longitudinal-mode. The laser frequency was continuously tuned over 2GHz with a longitudinal-mode tracking technique using FBG and was locked to C_2H_2 molecules. The frequency stability (Allan variance) estimated from error signals reached as high as 1.7×10^<-10> for τ=1s and 1.7×10^<-11> for τ=1×10^2s.

  139. Development of a C_2H_2 (acetylene) frequency-stabilized and single-polarization fiber laser

    KASAI Keisuke, YOSHIDA Masato, NAKAZAWA Masataka

    Technical report of IEICE. OCS　104　(260)　31-36　2004/08/20

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN： 0913-5685

    More details Close

    A frequency-stabilized fiber ring laser using linear absorption line of acetylene molecules is described. The output beam has no frequency modulation. A Fiber Brrag Grating (FBG) with a 3.7GHz bandwidth enabled single-frequency operation by selecting only one longitudinal-mode. The laser frequency was continuously tuned over 2GHz with a longitudinal-mode tracking technique using FBG and was locked to C_2H_2 molecules. The frequency stability (Allan variance) estimated from error signals reached as high as 1.7×10^<-10> for τ=1s and 1.7×10^<-11> for τ=1×10^2s.

  140. C-3-26 Optical filter characteristics of an ultra-narrow band polarization-maintaining fiber Bragg grating and its application to laser frequency tuning

    Yoshida Masato, Kasai Keisuke, Nakazawa Masataka

    Proceedings of the IEICE General Conference　2004　(1)　199-199　2004/03/08

    Publisher: The Institute of Electronics, Information and Communication Engineers

Show all ︎Show first 5

Industrial Property Rights 13

  1. 光ナイキストパルス伝送

    Property Type: Patent

  2. コヒーレント光時分割多重信号の復調方式

    Property Type: Patent

  3. コヒーレント光時分割多重伝送方式

    Property Type: Patent

  4. 半導体レーザ装置

    石井啓之, 藤原直樹, 渡辺啓, 井藤幹隆, 葛西恵介, 中沢正隆

    特許第6443955号

    Property Type: Patent

  5. 狭線幅波長可変半導体レーザ

    石川光映, 石井啓之, 中沢正隆, 葛西恵介

    特許第6369946号

    Property Type: Patent

  6. 半導体レーザ素子

    石井啓之, 藤原直樹, 井藤幹隆, 葛西恵介, 中沢正隆

    特許第6245656号

    Property Type: Patent

  7. 広帯域波長可変レーザ

    石川光映, 石井啓之, 中沢正隆, 葛西恵介

    特許第6128655号

    Property Type: Patent

  8. 光伝送方法および光伝送装置

    中沢正隆, 岩月勝美, 廣岡俊彦, 吉田真人, 葛西恵介

    Property Type: Patent

  9. レーザ圧力・ひずみ計

    中沢正隆, 吉田真人, 葛西恵介

    Property Type: Patent

  10. 周波数安定化レーザ

    石井啓之, 藤原直樹, 中沢正隆, 葛西恵介

    Property Type: Patent

  11. 光位相同期光源

    石井啓之, 藤原直樹, 中沢正隆, 葛西恵介

    Property Type: Patent

  12. 多波長半導体レーザ

    石川光映, 石井啓之, 中沢正隆, 葛西恵介

    Property Type: Patent

  13. 光周波数コム発生装置

    石川光映, 石井啓之, 中沢正隆, 葛西恵介

    Property Type: Patent

Show all Show first 5

Research Projects 14

  1. Development of multi-scale observation techniques for monitoring slow-to-fast earthquakes

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Transformative Research Areas (A)

    Institution: The University of Tokyo

    2021/09/10 - 2026/03/31

  2. 大容量・高多重光アクセス網伝送技術 イ）高多重光アクセス網基盤技術

    葛西恵介, 吉田真人, 廣岡俊彦

    Offer Organization: 総務省

    System: ICT重点技術の研究開発

    Institution: 沖電気, 東北大学, 近畿大学, 慶應義塾大学, エピフォトニクス, 古河電工

    2022/04 - 2026/03

  3. 振幅・位相および時間情報を用いた３次元光秘匿通信技術の研究開発

    吉田 真人, 廣岡 俊彦, 葛西 恵介

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 基盤研究(A)

    Institution: 東北大学

    2021/04/05 - 2025/03/31

    More details Close

    初年度は、これまでに開発してきた光の位相と振幅を用いた2次元物理暗号へ、新たに時間軸におけるデータの拡散動作を導入した3次元光秘匿通信の動作原理を実証した。具体的には、送信機として任意波形生成装置を使用し、受信器としてデジタルオシロスコープを用いた単一チャネルのオフライン伝送実験の結果をもとに、時間軸のデータ拡散動作を追加することによる安全性の向上効果を検証した。その結果、8ビット以上の乱数を用いた時間拡散を利用することにより、盗聴者が1シンボル分の正しい情報を得るために必要な信号の受信回数を1桁以上高められることを明らかにした。これは暗号化に用いる信号の多値度を4倍（2ビット）高めることに相当する。言い換えると、一定の安全性を確保することを考えた場合に、時間領域の拡散効果を利用することにより暗号化信号の多値度を2ビットだけ下げることができ、より汎用性の高い電子部品（D/A、A/D変換器）を送受信装置に利用することが可能となる。このように提案する光秘匿通信方式の実用性を高められることを明らかにした。 また本年度は、上述したオフライン伝送実験の成果をもとに、リアルタイム動作を実現するためのFPGA（Field Programmable Gate Array）回路の作製に着手した。具体的には8ビットの乱数列生成器を追加し、それを用いて申請書で提案した2種類の時間拡散動作（方式１：ダミー信号を利用する方式、方式２：ダミー信号は用いず、暗号化データの順序を時間軸上で入れ替える）を実現するためのFPGA回路を設計した。

  4. Beyond 5Gのレジリエンスを実現するネットワーク制御技術の研究開発

    Offer Organization: 国立研究開発法人 情報通信研究機構

    System: Beyond 5G研究開発促進事業

    Institution: 東北大学, 広島大学, 日本電業工作

    2021/04 - 2024/03

  5. 第５世代移動通信システムの更なる高度化に向けた研究開発

    Offer Organization: 総務省

    System: 電波資源拡大のための研究開発

    Institution: KDDI総合研究所, 電気通信大学, 構造計画研究所, 株式会社国際電気通信基礎技術研究所, 東北大学, パナソニック

    2019/06 - 2023/03

  6. 新たな社会インフラを担う革新的光ネットワーク技術の研究開発 Ⅲ. 高効率光アクセスメトロ技術

    葛西恵介, 吉田真人, 廣岡俊彦

    Offer Organization: 総務省

    System: ICT重点技術の研究開発

    Institution: 沖電気, 東北大学, 慶應義塾大学, NEC, KDDI総合研究所, エピフォトニクス

    2018/04 - 2022/03

  7. 光信号の低コスト受信・モニタリングのための小型光位相同期回路の研究開発

    Offer Organization: 国立研究開発法人 情報通信研究機構

    System: 高度通信・放送研究開発委託研究

    2015/04 - 2020/03

  8. 多機能なコヒーレントナイキストパルスの提案とそれを用いた超高速・高効率光伝送技術

    中沢 正隆, 廣岡 俊彦, 吉田 真人, 葛西 恵介

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業 特別推進研究

    Category: 特別推進研究

    Institution: 東北大学

    2014 - 2018

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    本年度はナイキストパルス伝送における高速化ならびに周波数利用効率拡大への取り組みとして、(a)ピコ秒パルス光源の光位相同期技術の開発とそれを用いた単一チャネル7.68 Tbit/s, 周波数利用効率9.7 bit/s/Hzの超高速・高効率コヒーレントナイキストパルス伝送、および(b)ノンコヒーレントナイキストパルス伝送を用いた単一チャネル10 Tbit/s伝送、の2つを中心に取り組んだ。 (a)に関しては、コヒーレントナイキストパルスを用いて単一チャネル3.84 Tbit/sの超高速伝送を10 bit/s/Hzを上回る高い周波数利用効率で実現した。具体的には、送信用光源だけでなく新たに受信用のLO光源としてもモード同期ファイバレーザ(MLFL)を用いることでナイキストパルスの高OSNR化を図った。さらに、送受信用MLFL間の光位相同期回路を新たに開発した。これらの要素技術により、9.7 bit/s/Hzの極めて周波数利用効率を有する単一チャンネル7.68 Tbit/s-150km超高速コヒーレントナイキストパルス伝送に初めて成功した。10 Tbit/s近い伝送速度で10 bit/s/Hzに迫る高い周波数利用効率を実現した前例はなく、これらの結果はナイキストパルスが極めて優れた伝送性能を有するパルスであることを示している。 一方(b)に関しては、ノンコヒーレントナイキストパルスのシンボルレートを1.28 Tsymbol/sから2.56 Tsymbol/sへ高速化することにより、単一チャネルで10.2 Tbit/sの超高速伝送を世界で初めて実現した。具体的には、超短ナイキストパルス(パルス幅 : 340 fs)の生成、ファイバ伝送路の4次分散まで考慮した高次分散の高精度な補償、信号光と制御光の間のドリフトを抑制した超高速光多重分離回路(ゲート幅 : 230 fs)、RZ-CW変換法による受信信号のS/N比の向上、等の開発に取り組んだ。その結果、単一チャネル10.2 Tbit/s信号の300km伝送に世界で初めて成功した。このときの周波数利用効率は2.5 bit/s/Hzであった。本実験ではデジタルコヒーレント伝送に見られるオフライン処理ではなく誤り率をオンラインで測定しており、超高速伝送を簡便な構成で実現できる方式として有用である。

  9. Study on precise optical phase control technique by employing a wideband optical voltage controlled oscillator for coherent optical communication

    KASAI KEISUKE

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

    Category: Grant-in-Aid for Challenging Exploratory Research

    Institution: Tohoku University

    2014/04/01 - 2016/03/31

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    With the aim of applying to ultra-multilevel coherent optical communication, I have developed a wideband, narrow linewidth optical voltage controller (OVCO) by using an acousto-optic modulator (AOM) and a narrow linewidth laser. By employing a InP-based AOM, I have realized a wideband OVCO with a 0.1 dB-frequency response bandwidth of ±2.5 MHz. With an optical phase-locked loop (PLL) circuit consisting of the present OVCO and a 1.5 um narrow linewidth fiber laser, which enables us to realize carrier phase synchronization between the transmitted data and the LO signal, I have successfully transmitted a 120 Gbit/s 64 QAM data over 150 km. This is the first time coherent transmission with an AOM-based OVCO-PLL system.

  10. Study on a narrow linewidth frequency-stabilized laser for coherent optical communication

    KASAI KEISUKE

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)

    Category: Grant-in-Aid for Young Scientists (A)

    Institution: Tohoku University

    2014/04/01 - 2016/03/31

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    With the aim of applying to next generation ultra-multilevel coherent optical communication, I have developed a 1.5 um frequency-stabilized laser with a high optical signal-to-noise ratio, a narrow linewidth, and low intensity noise characteristics. As an optical frequency standard, I have developed a compact and stable Fabry-Perot etalon with a linewidth as narrow as 60 MHz, which was made of a low expansion complex material based on crystal. As a coherent laser for frequency stabilization, I have constructed a 295 mW output, single frequency fiber laser with a linewidth of 5 kHz, relative intensity noise (RIN) of less than -120 dB/Hz. Furthermore, a laser diode with a linewidth of 8 kHz and a RIN of -130 dB/Hz has been developed. By stabilizing their frequency to the peak of etalon, I have successfully realized a low noise coherent laser with a frequency stability of 1E-12. In addition, I have applied these lasers to coherent optical transmission and demonstrated their usefulness.

  11. 超多値QAM信号のマルチコア光ファイバ伝送に関する研究 Competitive

    2012/11 - 2015/10

  12. デジタル位相光制御による低消費電力高速コヒーレント伝送技術の研究開発

    Offer Organization: 国立研究開発法人 情報通信研究機構

    System: 高度通信・放送研究開発委託研究

    2011/04 - 2014/03

  13. 高い周波数利用効率を有する大容量QAMコヒーレント光伝送に関する研究

    葛西 恵介

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業 特別研究員奨励費

    Category: 特別研究員奨励費

    Institution: 東北大学

    2009 - 2011

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    本研究は高密度に多重化された光キャリヤの一本一本を256以上の多値QAM変調することにより、10bit/s/Hz以上の高い周波数利用効率を有する大容量コヒーレント伝送の実現を目的としている。本年度(平成23年度)はまず初年度からの継続課題として、低強度雑音・低位相雑音特性を有するコヒーレント伝送用周波数安定化光源の開発に取り組んだ。また、従来の多値コヒーレント伝送システムにOFDM方式を適用し、マルチキャリヤコヒーレント伝送実験を行った。さらに発展課題として、今後の伝送容量のさらなる増大を念頭に、RZ-CW変換法を用いたコヒーレントOTDM(Optical Time Division Multiplexing)-RZ/QAM伝送に取り組んだ。以下にその具体的な研究成果示す。 光源開発においては、高出力(50mW)、狭線幅、低RIN特性を有する導波路リング共振器型LDの発振周波数をアセチレン分子吸収線へ安定化し、無変調出力型周波数安定化LDの開発に成功した。本成果は、従来は出力10mW程度であった周波数安定化光源を50mWという高出力型のレーザで実現した点である。多値度の大きな変調信号を正確に復調するためには信号S/Nを大きく保つ必要があるため、このような高出力型のコヒーレント光源は将来の超多値コヒーレント伝送では大変重要である。マルチキャリヤ伝送においては、光変調器によって生成した10本の光キャリヤを2.5Gsymbol/s,256QAM-OFDM変調し、トータル400Gbit/sのデータ信号を400kmコヒーレント伝送することに成功した。本伝送においては周波数利用効率14bit/s/Hzを達成している。これまでこのような高い周波数利用効率伝送を実現した例はなく、本伝送技術が世界的に見ても非常に優れていることを示す成果である。発展的課題として行ったコヒーレントOTDM-RZ/QAM伝送では、受信部でS/Nの高い状態でデータ復調を実現するRZ-CW変換法を新たに提案し、これを用いた単一チャネル800Gbit/sデータの(偏波多重、10Gsymbol/s,8-OTDM,32QAM)225km伝送に成功した。本成果は近い将来の100Gbit/sを越える大容量伝送を実現するための有望な伝送方式の一つとして提案するものである。

  14. 周波数安定化レーザ及びコヒーレント光通信に関する研究 Competitive

    System: SCF System for Establishment and Support of Center's of Excellence

    2008/04 - 2009/03

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  1. デジタル位相光制御による低消費電力高速コヒーレント伝送技術に関する研究開発

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    本研究では低速なディジタル光PLLを搭載した復調システムを使用して20GbpsのQPSK信号を、3時間の間誤りなく80kmコヒーレント伝送することに成功した。本研究で実現したデジタル光PLL回路は通常の伝送システムでは必須となる高速DSPを必要とせず、位相推定にともなうDSPでの計算量を大幅に削減でき、伝送システムの全体の低消費電力化を実現できる。また将来的により高いビットレートへの互換性と拡張性と持っており、将来の大容量、超多値光伝送を実現するための一つの方向性を示すうえで意義の大きい成果ある。