Influence of channel misalignment of time-interleaved DAC on sensitivity degradation in coherent optical receivers. - Changyo Han; Koji Igarashi; Kazuro Kikuchi (OFC/NFOEC, 2013)

Frequency stabilization of multiple semiconductor lasers for Nyquist-WDM transmission systems. - Koji Igarashi; Takehiro Tsuritani; Itsuro Morita; Kazuhiro Katoh; Kazuro Kikuchi (OFC/NFOEC, 2013)

Comparison of network cost and power consumption between a single-line-rate network and a flexible-bitrate network in the beyond-100-Gb/s networks era. - Noboru Yoshikane; Koji Igarashi; Takehiro Tsuritani (OFC/NFOEC, 2013)

Selective mode conversion using phase plates for 10-mode fiber. - Koji Igarashi; Daiki Soma; Takehiro Tsuritani (ECOC, 2014)

1-Exabit/s×km super-Nyquist-WDM multi-core-fiber transmission. - Koji Igarashi; Takehiro Tsuntani; Itsuro Morita (ECOC, 2014)

Degenerate modes multiplexer/demultiplexer using Mach-Zehnder interferometer with image inversion. - Daiki Soma; Koki Takeshima; Koji Igarashi; Takehiro Tsuritani (ECOC, 2014)

Bit-error rate performance of super-Nyquist-WDM DP-QPSK signals with duobinary-pulse shaping. - Koji Igarashi; Takehiro Tsuritani; Itsuro Morita (OFC, 2014)

Long-haul transmission using multicore fibers. - Hidenori Takahashi; Koji Igarashi; Takehiro Tsuritani (OFC, 2014)

Experimental study on polybinary-pulse-shaped QAM signals for highly-spectral-efficient Super-Nyquist-WDM systems. - Koji Igarashi; Takehiro Tsuritani; Itsuro Morita (ECOC, 2015)

2.05 Peta-bit/s super-nyquist-WDM SDM transmission using 9.8-km 6-mode 19-core fiber in full C band. - Daiki Soma; Koji Igarashi; Yuta Wakayama; Koki Takeshima; Yu Kawaguchi; Noboru Yoshikane; Takehiro Tsuritani; Itsuro Morita; Masatoshi Suzuki (ECOC, 2015)

DMD measurement of 114-SDM transmission fibre using low-coherence interferometry with digital holographic processing. - Yuta Wakayama; Hidenori Taga; Koji Igarashi; Takehiro Tsuritani (ECOC, 2015)

114 space-division-multiplexed transmission over 9.8-km weakly-coupled-6-mode uncoupled-19-core fibers. - Koji Igarashi; Daiki Soma; Yuta Wakayama; Koki Takeshima; Yu Kawaguchi; Takehiro Tsuritani; Itsuro Morita; Masatoshi Suzuki (OFC, 2015)

51.1-Tbit/s MCF transmission over 2, 520 km using cladding pumped 7-core EDFAs. - Koki Takeshima; Takehiro Tsuritani; Yukihiro Tsuchida; Koichi Maeda; Tsunetoshi Saito; Kengo Watanabe; Toru Sasa; Katsunori Imamura; Ryuichi Sugizaki; Koji Igarashi; Itsuro Morita; Masatoshi Suzuki (OFC, 2015)

Ultra-dense space division multiplexing technologies towards multi-Peta bit/s optical transmission. - Masatoshi Suzuki; Daiki Soma; Koji Igarashi; Yuta Wakayama; Koki Takeshima; Yu Kawaguchi; Noboru Yoshikane; Takehiro Tsuritani; Itsuro Morita (ICTON, 2016)

A new VSJ mechanism for multi-directional passivity and quick response. - Shinya Kajikawa; Takuya Akasaka; Koji Igarashi (IROS, 2016)

6-Mode 19-core fiber for weakly-coupled mode-multiplexed transmission over uncoupled cores. - Tetsuya Hayashi; Takuji Nagashima; Kazuhiro Yonezawa; Yuta Wakayama; Daiki Soma; Koji Igarashi; Takehiro Tsuritani; Takashi Sasaki (OFC, 2016)

All-fiber-based selective mode multiplexer and demultiplexer for six-mode multiplexed signals. - Koji Igarashi; Kyung Jun Park; Daiki Soma; Yuta Wakayama; Takehiro Tsuritani; Byoung Yoon Kim (OFC, 2016)

Intermediate mode interchange for reduction of differential mode-group delay in weakly-coupled 6-mode fiber transmission line. - Yuta Wakayama; Daiki Soma; Koji Igarashi; Hidenori Taga; Takehiro Tsuritani (OFC, 2016)

257-Tbit/s Partial MIMO-based 10-Mode C+L-band WDM Transmission over 48-km FMF. - Daiki Soma; Shohei Beppu; Yuta Wakayama; Yu Kawaguchi; Koji Igarashi; Takehiro Tsuritani (ECOC, 2017)

10.16 Peta-bit/s Dense SDM/WDM transmission over Low-DMD 6-Mode 19-Core Fibre Across C+L Band. - Daiki Soma; Yuta Wakayama; Shohei Beppu; Seiya Sumita; Takehiro Tsuritani; Tetsuya Hayashi; Takuji Nagashima; Masato Suzuki; Hidenori Takahashi; Koji Igarashi; Itsuro Morita; Masatoshi Suzuki (ECOC, 2017)

Dual C+L-Band Six-Mode Optical Amplifier with Widely Erbium-Doped Fibre. - Yuta Wakayama; Daiki Soma; Koji Igarashi; Hidenori Taga; Takehiro Tsuritani (ECOC, 2017)

Partial MIMO-based 10-mode-multiplexed transmission over 81km weakly-coupled few-mode fiber. - Daiki Soma; Yuta Wakayama; Koji Igarashi; Takehiro Tsuritani (OFC, 2017)

Low-loss and Low-crosstalk All-fiber-based Six-mode Multiplexer and Demultiplexer for Mode-Multiplexed QAM Signals in C-band. - Koji Igarashi; Yuta Wakayama; Daiki Soma; Takehiro Tsuritani; Itsuro Morita; Kyung Jun Park; Jaekwon Ko; Byoung Yoon Kim (OFC, 2018)

An Iterative Soft Interference Cancellation for Pilot-Assisted Optical-OFDM with LDPC Code Optimized by EXIT Chart. - Noboru Osawa; Shinsuke Ibi; Koji Igarashi; Seiichi Sampei (OFC, 2018)

266.1-Tbit/s Repeatered Transmission over 90.4-km 6-Mode Fiber Using Dual C+L-Band 6-Mode EDFA. - Yuta Wakayama; Daiki Soma; Shohei Beppu; Seiya Sumita; Koji Igarashi; Takehiro Tsuritani (OFC, 2018)

Mode-Dependent Probabilistic Shaping for Highly-Efficient Weakly Coupled 10-Mode Fiber Transmission. - Shohei Beppu; Daiki Soma; Yuta Wakayama; Seiya Sumita; Koji Igarashi; Hidenori Takahashi; Takehiro Tsuritani (OFC, 2019)

Constellation Monitor of QPSK Optical Signals Based on Spectrally-sliced Coherent Optical Spectrum Analyzers. - Koji Igarashi; Naoki Urakawa (OECC/PSC, 2019)

Numerical Evaluation of Modal Crosstalk Statistics in Multiple Connectors of Weakly-coupled 10-mode Fibers. - Gen Kawabata; Koji Igarashi (OECC/PSC, 2019)

Real-Time DSP for Adaptive FIR Filters Based on LMS Algorithm. - Masahiro Kikuta; Shohei Beppu; Tomoyuki Nagai; Yasuo Saito; Takehiro Tsuritani; Koji Igarashi (OECC/PSC, 2019)

Generation Efficiency of Fiber Four-Wave Mixing for Phase-Shift Keying Signal Light. - Kyo Inoue; Koji Igarashi (IEICE Trans. Commun., 2019)

Reduction of Crosstalk Influence in a 7-Core Multicore Fiber by Frequency Interleave. - Shun Orii; Kyo Inoue; Koji Igarashi (IEICE Trans. Commun., 2019)

EXIT Chart-Aided Design of LDPC Codes for Self-Coherent Detection with Turbo Equalizer for Optical Fiber Short-Reach Transmissions. - Noboru Osawa; Shinsuke Ibi; Koji Igarashi; Seiichi Sampei (IEICE Trans. Commun., 2019)

Bit-Error-Rate Degradation Due to Inter-Channel Crosstalk of Different Signal Format. - Naruki Shinohara; Koji Igarashi; Kyo Inoue (IEICE Trans. Commun., 2019)

Simplified Iterative Decoder for Polybinary-Shaped Optical Signals in Super-Nyquist Wavelength Division Multiplexed Systems. - Shuai Yuan; Koji Igarashi (IEICE Trans. Commun., 2019)

Ultra-long-time (0.8 s) characterization of laser phase noise with high temporal resolution (800 ps) based on heterodyne reception with FPGA data acquisition. - Hayato Kiwata; Masahiro Kikuta; Masahiro Shigihara; Koji Igarashi (ECOC, 2020)

Sparse-Dense MLC for Peak Power Constrained Channels. - Tsuyoshi Yoshida; Koji Igarashi; Magnus Karlsson 001; Erik Agrell (ECOC, 2020)

Required and Received SNRs in Coded Modulation. - Tsuyoshi Yoshida; Koji Igarashi; Masashi Binkai; Shun Chikamori; Mikael Mazur; Jochen Schröder; Keisuke Matsuda; Shota Koshikawa; Naoki Suzuki; Magnus Karlsson 001; Erik Agrell (ECOC, 2020)

Real-Time Strongly-Coupled 4-Core Fiber Transmission. - Shohei Beppu; Koji Igarashi; Hiroshi Mukai; Masahiro Kikuta; Masahiro Shigihara; Daiki Soma; Takehiro Tsuritani; Itsuro Morita (OFC, 2020)

Spectrally Slicing Coherent Optical Spectrum Analyzer for Measuring Complex Field Waveforms of Optical QAM Signals. - Yasuhiro Kawabata; Naoki Urakawa; K. Kinoshita; Koji Igarashi (OFC, 2020)

Mode-multiplexed 16QAM transmission over 60-km coupled four-core fibres using real-time MIMO-DSP with high-accuracy frequency offset estimation. - Shohei Beppu; Masahiro Kikuta; Koji Igarashi; Hiroshi Mukai; Masahiro Shigihara; Yasuo Saito; Daiki Soma; Hidenori Takahashi; Noboru Yoshikane; Takehiro Tsuritani (ECOC, 2021)

Real-time MIMO-DSP Technologies for SDM Systems. - Shohei Beppu; Koji Igarashi; Masahiro Kikuta; Hiroshi Mukai; Masahiro Shigihara; Yasuo Saito; Daiki Soma; Hidenori Takahashi; Noboru Yoshikane; Itsuro Morita; Takehiro Tsuritani (OFC, 2021)

Real-time Transoceanic Coupled 4-core Fiber Transmission. - Shohei Beppu; Masahiro Kikuta; Koji Igarashi; Hiroshi Mukai; Masahiro Shigihara; Yasuo Saito; Daiki Soma; Hidenori Takahashi; Noboru Yoshikane; Itsuro Morita; Masatoshi Suzuki; Takehiro Tsuritani (OFC, 2021)

FPGA Implementation of Hierarchical Subcarrier Rate and Distribution Matching for up to 1.032 Tb/s or 262144-QAM. - Tsuyoshi Yoshida; Koji Igarashi; Yoshiaki Konishi; Magnus Karlsson 001; Erik Agrell (OFC, 2021)

Compressed Shaping: Concept and FPGA Demonstration. - Tsuyoshi Yoshida; Koji Igarashi; Magnus Karlsson 001; Erik Agrell (CoRR, 2021)

Analysis of Signal Distribution in ASE-Limited Optical On-Off Keying Direct-Detection Systems. - Hiroki Kawahara; Kyo Inoue; Koji Igarashi (IEICE Trans. Commun., 2021)

Soft-decision FEc Designed for Optically Preamplified PAM4 Direct Detection. - Koji Igarashi; Takumi Takahashi; Seiichi Sampei; Kyo Inoue (OECC/PSC, 2022)

Complex Field Measurement of Optical Frequency Combs over 100-GHz Bandwidth Using a Spectrally-Slicing-and-Synthesizing Method. - Yusuke Shimizu; Koji Igarashi (OECC/PSC, 2022)

Few-Mode Fiber Technology, Deployments, and Systems. - Pierre Sillard; Kaoutar Benyahya; Daiki Soma; Guillaume Labroille; Pu Jian; Koji Igarashi; Roland Ryf; Nicolas K. Fontaine; Georg Rademacher; Kohki Shibahara (Proc. IEEE, 2022)

AoA Estimation-Aided Bayesian Receiver Design via Bilinear Inference for mmWave Massive MIMO. - Kenta Ito; Takumi Takahashi; Koji Igarashi; Shinsuke Ibi; Seiichi Sampei (ICC, 2023)

Real-time 6-Mode 19-Core Fiber Transmission. - Shohei Beppu; Masahiro Kikuta; Daiki Soma; Yoichi Yaegashi; Koji Igarashi; Masahiro Shigihara; Kazuhiko Aizawa; Noboru Yoshikane; Takehiro Tsuritani (OFC, 2023)

Real-time MIMO Adaptive Equalization with Carrier-phase Recovery for Mode-division Multiplexed Optical Coherent System. - Koji Igarashi (OFC, 2023)

Level Allocation of Four-Level Pulse-Amplitude Modulation Signal in Optically Pre-Amplified Receiver Systems. - Hiroki Kawahara; Koji Igarashi; Kyo Inoue (IEICE Trans. Commun., 2023)

Reduction of Fiber Four-Wave Mixing Generated from Modulated Lights by Inserting Dispersive Elements. - Ayano Inoue; Koji Igarashi; Shigehiro Takasaka; Kyo Inoue (IEICE Trans. Commun., 2025)

Physics-Aware Sparse Signal Recovery Through PDE-Governed Measurement Systems. - Tadashi Wadayama; Koji Igarashi; Takumi Takahashi (CoRR, 2025)

Physics-Aware Decoding for Communication Channels Governed by Partial Differential Equations. - Tadashi Wadayama; Koji Igarashi; Takumi Takahashi (CoRR, 2025)

Joint Channel, CFO, and Data Estimation via Bayesian Inference for Multi-User MIMO-OFDM Systems. - Kenta Ito; Takumi Takahashi; Koji Ishibashi; Koji Igarashi; Shinsuke Ibi (IEEE Trans. Wirel. Commun., 2025)