Capacity Maximization of OWC Systems via Joint Precoding and Probabilistic Shaping

We propose and experimentally demonstrate a capacity-approaching scheme via joint probabilistic shaping (PS) and precoding in an optical wireless communication (OWC) system. Different from the bit-and-power- and entropy-loading schemes, the proposed scheme only requires one modulation format with one single-PS distribution while offering the ability of maximizing the system's throughput. Moreover, we show that the proposed scheme also exhibits superior spectral efficiency (SE) and generalized mutual information (GMI) performances. As a result, the implementation complexity is significantly reduced without affecting the capacity-approaching capability. We show that for a 36-Gbit/s OWC transmission, ~5 dB improvement in the received optical power (ROP) sensitivity can be achieved by using the proposed scheme. In addition, a maximized 48-Gbit/s transmission over 2-m OWC channel is successfully demonstrated with a BER lower than 3.8 × 10
^-3
, which corresponds to more than 33% capacity enhancement.