A Method of Fast M-type Approximation on Probabilistic Shaping for Optical Communication

Probabilistic shaping is widely used in optical communication to increase the data rate. Because the number of symbols is an integer, when modulating the input signals into the predefined symbol sequence, the modulated probabilistic distribution is a discrete M-type distribution. In this paper, a fast method of M-type approximation based on information divergence is proposed. Compared with traditional algorithm, the proposed fast M-type approximation can greatly reduce the computation complexity while achieving the same results. This paper also proves mathematically that the information divergence increment has boundaries for M-type approximation near the ideal distribution. Based on the bounds of information divergence increment, the M-type approximation distribution boundary related to ideal distribution can be obtained.