Performance improvement of an acetylene (C2H2) frequency-stabilized fiber laser. - Keisuke Kasai; Akihito Suzuki; Masato Yoshida; Masataka Nakazawa (IEICE Electron. Express, 2006)

Optical phase-locked loop for coherent transmission over 500km using heterodyne detection with fiber lasers. - Keisuke Kasai; Jumpei Hongo; Masato Yoshida; Masataka Nakazawa (IEICE Electron. Express, 2007)

Polarization and frequency division multiplexed 1Gsymbol/s, 64 QAM coherent optical transmission with 8.6bit/s/Hz spectral efficiency over 160km. - Hiroki Goto; Masato Yoshida; Tatsunori Omiya; Keisuke Kasai; Masataka Nakazawa (IEICE Electron. Express, 2008)

The use of a Nyquist filter for reducing an optical signal bandwidth in a coherent QAM optical transmission. - Keisuke Kasai; Jumpei Hongo; Hiroki Goto; Masato Yoshida; Masataka Nakazawa (IEICE Electron. Express, 2008)

STRAC: Personal Information Access Control for Emergency Systems. - Kyoji Kawagoe; Keisuke Kasai (SERVICES, 2010)

60Gbit/s 64 QAM-OFDM coherent optical transmission with a 5.3GHz bandwidth. - Tatsunori Omiya; Seiji Okamoto; Keisuke Kasai; Masato Yoshida; Masataka Nakazawa (IEICE Electron. Express, 2010)

Polarization-multiplexed, 10Gsymbol/s, 64QAM coherent transmission over 150km with OPLL-based homodyne detection employing narrow linewidth LDs. - Yixin Wang; Keisuke Kasai; Masataka Nakazawa (IEICE Electron. Express, 2011)

256 QAM Digital Coherent Optical Transmission Using Raman Amplifiers. - Masato Yoshida; Seiji Okamoto; Tatsunori Omiya; Keisuke Kasai; Masataka Nakazawa (IEICE Trans. Commun., 2011)

An LD-based ultra-low phase noise opll circuit using an optical voltage controlled oscillator. - Keisuke Kasai; Yixin Wang; Masataka Nakazawa (OFC/NFOEC, 2013)

A single-channel, 1.6 Tbit/s 32 QAM coherent pulse transmission over 150 km with RZ-CW conversion and FDE techniques. - David Odeke Otuya; Keisuke Kasai; Toshihiko Hirooka; Masato Yoshida; Masataka Nakazawa; Tokutaka Hara; Satoshi Oikawa (OFC/NFOEC, 2013)

Novel ultrafast TDM demultiplexing scheme using orthogonality in coherent Nyquist pulses. - Koudai Harako; David Odeke Otuya; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (ECOC, 2014)

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. - David Odeke Otuya; Koudai Harako; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (ECOC, 2014)

Real-time adaptive 4-64 QAM coherent optical transmission over 320 km with FPGA-based transmitter and receiver. - Masato Yoshida; Toshihiko Hirooka; Keisuke Kasai; Masataka Nakazawa (ECOC, 2014)

2048 QAM (66 Gbit/s) single-carrier coherent optical transmission over 150 km with a potential SE of 15.3 bit/s/Hz. - Shohei Beppu; Keisuke Kasai; Masato Yoshida; Masataka Nakazawa (OFC, 2014)

1.92 Tbit/s, 64 QAM coherent Nyquist pulse transmission over 150 km with a spectral efficiency of 7.5 bit/s/Hz. - David Odeke Otuya; Keisuke Kasai; Toshihiko Hirooka; Masato Yoshida; Masataka Nakazawa (OFC, 2014)

60 Gbit/s, 64 QAM LD-based injection-locked coherent heterodyne transmission over 160 km with a spectral efficiency of 9 bit/s/Hz. - Yixin Wang; Keisuke Kasai; Masato Yoshida; Masataka Nakazawa (IEICE Electron. Express, 2014)

QAM quantum noise stream cipher using digital coherent optical transmission. - Masato Yoshida; Toshihiko Hirooka; Keisuke Kasai; Masataka Nakazawa (ACSSC, 2015)

Real-time adaptive 4-64 QAM, 20-60 Gbit/s quantum noise stream cipher transmission over 320 km with FPGA-based transmitter and receiver. - Masato Yoshida; Toshihiko Hirooka; Keisuke Kasai; Masataka Nakazawa (ECOC, 2015)

256 QAM (polarization-multiplexed, 5 Gsymbol/s) coherent transmission with an injection-locked homodyne detection technique. - Keisuke Kasai; Shohei Beppu; Yixin Wang; Masataka Nakazawa (OFC, 2015)

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. - David Odeke Otuya; Koudai Harako; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2015)

Real-time 10 Gbit/s-16 QAM quantum stream cipher transmission over 320 km with FPGA-based transmitter and receiver. - Masato Yoshida; Toshihiko Hirooka; Keisuke Kasai; Masataka Nakazawa (OFC, 2015)

First demonstration of digital coherent transmission in a deployed ROADM network with a 120 Gbit/s polarization-multiplexed 64 QAM signal. - Toshihiko Hirooka; Keisuke Kasai; Yixin Wang; Masataka Nakazawa; Masaki Shiraiwa; Yoshinari Awaji; Naoya Wada (IEICE Electron. Express, 2015)

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. - Keisuke Kasai; Masato Yoshida; Masataka Nakazawa (OFC, 2016)

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. - Keisuke Kasai; Toshihiko Hirooka; Masato Yoshida; Masataka Nakazawa; Masaki Shiraiwa; Yoshinari Awaji; Naoya Wada (ECOC, 2017)

80 Gbit/s/ch, 256 QAM Digital Coherent Optical Transmission System with Injection-Locking for Next Generation Mobile Fronthaul Network. - Keisuke Kasai; Yixin Wang; Masato Yoshida; Toshihiko Hirooka; Katsumi Iwatsuki; Masataka Nakazawa (ECOC, 2017)

A New Optical Phase-Locked System Between Ultrashort Pulses for 640 Gbaud Nyquist OTDM Coherent QAM Transmission. - Kosuke Kimura; Junpei Nitta; Masato Yoshida; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (ECOC, 2017)

42.3-Tbit/s, 18-Gbaud 64QAM WDM coherent transmission of 160 km over full C-band using an injection locking technique with a spectral efficiency of 9 bit/s/Hz. - Takashi Kan; Keisuke Kasai; Masato Yoshida; Masataka Nakazawa (OFC, 2017)

Full C-band, mode-hop-free wavelength-tunable laser diode with a linewidth of 8 kHz and a RIN of -130 dB/Hz. - Keisuke Kasai; Masataka Nakazawa; Yasunori Tomomatsu; Takashi Endo (OFC, 2017)

Single-carrier 216 Gbit/s, 12 Gsymbol/s 512 QAM coherent transmission over 160 km with injection-locked homodyne detection. - Yixin Wang; Keisuke Kasai; Masato Yoshida; Masataka Nakazawa (OFC, 2017)

Single-channel 3.84 Tbit/s, 64 QAM coherent Nyquist pulse transmission over 150 km with frequency-stabilized and mode-locked laser. - Masato Yoshida; Junpei Nitta; Kosuke Kimura; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2017)

Backward-Rayleigh-Scattering Suppressed 160 Gbit/s 256 QAM Injection-Locked Bidirectional Coherent Transmission for Next Generation Mobile Fronthaul. - Keisuke Kasai; Masato Yoshida; Toshihiko Hirooka; Katsumi Iwatsuki; Masataka Nakazawa (ECOC, 2018)

Injection-locked Homodyne Detection for Higher-order QAM Transmission. - Keisuke Kasai; Yixin Wang; Masato Yoshida; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2018)

Observation of Guided Acoustic-Wave Brillouin Scattering and its Digital Compensation in Coherent QAM Transmission. - Masataka Nakazawa; Masaki Terayama; Seiji Okamoto; Masato Yoshida; Keisuke Kasai; Toshihiko Hirooka (OFC, 2018)

Experimental and Numerical Comparison of Probabilistically-Shaped 4096 QAM and Uniformly-Shaped 1024 QAM in All-Raman Amplified 160 km Transmission. - Seiji Okamoto; Masaki Terayama; Masato Yoshida; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2018)

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. - Masaki Terayama; Seiji Okamoto; Keisuke Kasai; Masato Yoshida; Masataka Nakazawa (OFC, 2018)

Dual-Polarization On-Line 256 and 512 QAM Digital Coherent Transmission. - Masato Yoshida; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2019)

GAWBS Noise Characteristics in Digital Coherent Transmission in Various Optical Fibers. - Naoya Takefushi; Masato Yoshida; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OECC/PSC, 2019)

Real-Time 256 QAM Bi-directional Coherent Transmission in Next Generation Mobile Fronthaul. - Masato Yoshida; Takashi Kan; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OECC/PSC, 2019)

64 Gbit/s, 256 QAM Coherently-Linked Optical and Wireless Transmission in 61 GHz Band Using Novel Injection-Locked Carrier Frequency Converter. - Keisuke Kasai; Toshihiko Hirooka; Masato Yoshida; Masataka Nakazawa (ECOC, 2020)

10 GHz, 6.2 ps Transform-Limited Coherent Optical Pulse Generation from a 1.55 μm, Self-Injection Gain-Switched DFB-LD. - Keisuke Kasai; Masataka Nakazawa (OFC, 2020)

Experimental and Theoretical Analyses of GAWBS Phase Noise in Multi-Core Fiber for Digital Coherent Transmission. - Naoya Takefushi; Masato Yoshida; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2020)

10 Tbit/s QAM Quantum Noise Stream Cipher Coherent Transmission over 160 km. - Masato Yoshida; Takashi Kan; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2020)

Research Project to Realize Various High-reliability Communications in Advanced 5G Network. - Takahide Murakami; Yoji Kishi; Koji Ishibashi; Keisuke Kasai; Hiroyuki Shinbo; Morihiko Tamai; Kensuke Tsuda; Masataka Nakazawa; Yu Tsukamoto; Hiroyuki Yokoyama; Yoshimi Fujii; Yuta Seki; et al. (WCNC, 2020)

Broadband Dynamic Injection-Locking Performance of Fabry-Perot LD and Its Application to Coherent Homodyne Receiver. - Takashi Kan; Keisuke Kasai; Masato Yoshida; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2021)

64 Gbit/s, 256 QAM Transmission Through Coherent Optical-Wireless Link at 61 GHz Using Simple and High OSNR Carrier Frequency Converter. - Keisuke Kasai; Taisei Sato; Toshihiko Hirooka; Masato Yoshida; Masataka Nakazawa (OFC, 2021)

GAWBS Noise Correlation Between Cores in Four-Core Fiber. - Kozo Sato; Masato Yoshida; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OFC, 2021)

Demodulation Performance Comparison of 160 Gbaud Coherent Nyquist Pulse Signal with Analog and Digital DEMUX Schemes. - Masato Yoshida; Kosuke Kimura; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (OECC/PSC, 2022)

Precise Measurements and their Analysis of GAWBS-Induced Depolarization Noise in Multi-Core Fiber for Digital Coherent Transmission. - Masato Yoshida; Kozo Sato; Toshihiko Hirooka; Keisuke Kasai; Masataka Nakazawa (IEICE Trans. Commun., 2022)

Experimental and Numerical Analysis of Ultrahigh-Speed Coherent Nyquist Pulse Transmission with Low-Nonlinearity Dispersion Compensator. - Kosuke Kimura; Masato Yoshida; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa (IEICE Trans. Commun., 2022)

Conversion Gain Enhancement of a UTC-PD-Integrated HEMT Photonic Double-Mixer by High-Intensity Optical Subcarrier Signal. - Dai Nakajima; Kazuki Nishimura; Mitsuki Watanabe; Tsung-Tse Lin; Keisuke Kasai; Masato Yoshida; Tetsuya Suemitsu; Taiichi Otsuji; Akira Satou (OFC, 2023)

Demodulation Performance Comparison of High-Speed Coherent Nyquist Pulse Signal with Analog and Digital Demultiplexing Schemes. - Masato Yoshida; Kosuke Kimura; Toshihiko Hirooka; Keisuke Kasai; Masataka Nakazawa (IEICE Trans. Commun., 2023)

New GAWBS Noise Interacting with Longitudinally Propagating Acoustic Waves in Few-mode Fibers. - Masato Yoshida; Takaaki Hirai; Shohei Beppu; Keisuke Kasai; Toshihiko Hirooka; Masataka Nakazawa; Yuta Wakayama; Noboru Yoshikane (OFC, 2024)