Simplified bit-class probabilistic shaping strategy based on PDM systems

This study aims to present a simplified bit-class probabilistic shaping (PS) strategy based on power domain multiplexing (PDM) systems. In this scheme, we employ bit-weighted distribution matching (BWDM) to achieve PS. By ingeniously applying the process of signal superposition, the low-complexity bit-class PS scheme requires encoding of only a small number of bits in the low-power two quadrature phase-shift keying (QPSK) signal, enhancing the quality of the transmitted signal with simple operations. At the receiver, to ensure the transmission performance of the system while minimizing computational complexity and enhancing system operational efficiency, we implemented the region decision method for demodulation. The proposed scheme was experimentally validated on a 2 km 7-core fiber, achieving accurate transmission of signals at a net rate of 103.6 Gb/s. The experimental results indicate that, when compared to the uniform 16-quadrature amplitude modulation (16QAM) signal and the PDM-orthogonal frequency division multiplexing (OFDM) signal without PS, the receiving sensitivity of the PS-16QAM signal in our scheme can gain 0.4 dB and 0.33 dB at a bit error rate (BER) of 3.8 × 10^-3 under the same net rate.