LDPC-coded DFT-Spread DMT signal transmission employing probabilistic shaping 16/32QAM for optical interconnection

The generation and transmission of a 150-Gb/s discrete-Fourier-transform spread (DFT-spread) probabilistic shaping (PS) 16QAM discrete multi-tone (DMT) signal with low-density parity-check (LDPC)-coded modulation for optical interconnection are proposed and experimentally demonstrated for the first time. The PS-16QAM symbols are reshaped from 32-QAM symbols based on the near-Gaussian distribution. The maximal shaping gain of around 0.5 dB is obtained for the PS-16QAM compared with the traditional unshaped one. Compared with the standard 16QAM, the proposed PS-16QAM DMT signal shows superior receiver sensitivity to provide abundant system loss budget for leveraging the legacy. Jointly iterative decoding algorithms based LDPC is utilized for PS de-mapping and inherent overlapped symbols identification in PS. In addition, the joint applications of DFT-spread and PS techniques can significantly improve received power sensitivity (RPS).