Probabilistic shaping 16 quadrature amplitude modulation scheme based on trellis-coded modulation for short-reach optical communication

A probabilistic shaping 16 quadrature amplitude modulation (PS-16QAM) scheme based on trellis-coded modulation (TCM) is proposed to provide an approach for improving TCM performance. With nonuniform probabilistic mapping of a subset of TCM-16QAM, the effective and favorable overall 16QAM constellation probability distribution is achieved. A 25-km standard single-mode fiber data transmission employing the proposed TCM-based PS-16QAM (TCM-PS-16QAM) is successfully demonstrated. Experimental results show that the proposed TCM-PS-16QAM-4 state (H = 2.9 bits/symbol) outperforms the traditional TCM-16QAM-n state (n = 4, 8, and 16) by 0.9, 0.5, and 0.1 dB in terms of optical signal-to-noise ratio (OSNR). TCM-PS-16QAM-4 state (H = 2.7 bits/symbol) exceeds TCM-PS-16QAM-4 state (H = 2.8 and 2.9 bits/symbol) by 0.6 and 0.9 dB OSNR enhancement, respectively, at the bit error rate of 1 × 10-3 and the data rate of 60 Gb/s.