Fast-adaptive weighted constellation designs based on hybrid constellation shaping for long-haul optical fiber communication systems

A novel fast-adaptive weighted hybrid-shaped M-ary quadrature amplitude modulation (HS-MQAM) format is proposed in this paper. By introducing a fast-adaptive weighting factor array related to geometric shaping and probabilistic shaping, the non-linear impairment is mitigated and the bit error rate (BER) and mutual information (MI) performances are further improved. The simulation results show that the proposed HS-61QAM outperforms both geometric-shaped 61 quadrature amplitude modulation (GS-61QAM) and regular 64QAM, and has more obvious advantages in the long-haul optical transmission system. For a 120-Gb/s optical communication system over 10 × 75 km fiber transmission link, compared with GS-61QAM and regular 64QAM, the proposed approach can achieve about 4.2 and 8 dB OSNR gain at the BER of 10⁻², and 0.21 and 0.55 bits/symbol MI gain at the OSNR of 22 dB.