Yohei Koganei

Soft decision forward error correction over nonlinear transmission of 1-Tb/s superchannel

We confirm backward-propagation nonlinear compensation makes noise statistics after nonlinear transmission closer to Gaussian and recovers the performance of low-density parity-check (LDPC) code with superchannel signal that consists of densely packed 5 × 34-GBd Nyquist dual-polarization 16QAM.

SC-LDPC Code With Nonuniform Degree Distribution Optimized by Using Genetic Algorithm

We propose a class of spatially-coupled low-density parity-check (SC-LDPC) codes consisting of a finite-length chain of component LDPC matrices which are assigned with different degree distributions, i.e., the strength of spatial coupling is nonuniform within an SC-LDPC code. For this class of codes, we use a modified density evolution algorithm to calculate the belief-propagation (BP) threshold on the binary erasure channel (BEC). We then optimize the degree distributions by a genetic algorithm where the BP-threshold is considered as the fitness value. The resultant codes were confirmed to exhibit improved decoding performance compared with SC-LDPC codes having uniform degree distributions.

Transmission performance of 3-bit/symbol modulation formats in dispersion-unmanaged link

We numerically investigate the transmission performance of 3-bit/symbol modulation formats in dispersion-unmanaged transmission systems. We find that probabilistic-shaped 64QAM has higher achievable rate than the other formats in back-to-back condition as well as after transmission.