Keisuke Matsuda

A wavelength monitor using unequally spaced back-emitting light for tunable LD array

A novel wavelength monitor scheme using unequally spaced back-emitting light for a tunable LD array is proposed. The measured variations in the monitor wavelength are less than +0.15 GHz at the ITU-T grids.

A Study of Laser White and Brownian FM Noise in Coherent QPSK Signals

We studied laser noise numerically and experimentally in terms of frequency variance within frequency estimation response time, and showed that a normalized variance below 1×10-6 is required to limit the penalty to 0.5 dB.

Nonlinearity-tolerant time domain hybrid modulation for 4–8 bits/symbol based on 2A8PSK

We propose time domain hybrid modulation to cover 4–8 bits/symbol range, based on 5, 6, and 7 bits/symbol 4D-2A8PSK. Simulation results indicate that they have up to 1.6 dB higher span loss budget than the hybrid modulation based on conventional modulation formats in nonlinear channels.

Comparison of Nonlinearity Tolerance of Modulation Formats for Subcarrier Modulation

We investigate the use of 4D constant modulus modulation format combined with subcarrier modulation. Compared to the star-8QAM format, the proposed format has an improved performance gain from reducing the baud rate down to 1 GBd.

Carrier phase estimation for 53.6 Gbaud QPSK signal encoded by low-rate FEC

A CPE aiming at the low SNR region and targeting PSK formats encoded with a low-rate FEC is evaluated for the first time. Via numerical simulation of a 53.6 Gbaud DP-QSPK signal with a coding rate of 0.48, we confirm that pilot-aided CPE achieves a 0.3 dB SNR improvement over a typical blind CPE at a low-rate FEC Q-limit of 1.2 dB.

Experimental study of the nonlinearity tolerance of a 100 Gbps dual-carrier DP-BPSK signal on a 3,080 km in-line dispersion compensated fiber link

We investigated experimentally the transmission performance of 100 Gbps dual-carrier DP-BPSK signals transmitted on a 3,080 km in-line chromatic dispersion compensated fiber link with real-time digital signal processing. Its doubled phase margin and nonlinear noise squeezing achieved 2 dB greater robustness to fiber nonlinearity effects compared to single-carrier DP-QPSK signal.