针对传统Gray映射在中高信噪比区域内对迭代译码的比特交织编码调制(BICMID)光通信系统改善信道容量性能有限的问题,基于互信息准则和比特的不等保护度提出了一种新颖的16QAM星座映射方案。仿真分析表明:在中高信噪比下,所提出的新映射方案比传统Gray映射方案的信道容量最大改善值可达1.18bit/channel。结合低密度奇偶校验(LDPC)码并借助外部信息传递(EXIT)图,该方案在光通信系统中具有很好的性能优势与应用前景。 Aiming at the limited capacity of optical communication system to improve the capacity of channel in iterative decoding for the traditional Gray mapping in the area of ​​high signal-to-noise ratio, a new novel method based on mutual information criterion and bit unequal degree of protection 16QAM constellation mapping scheme. The simulation results show that under the condition of medium to high signal-to-noise ratio, the proposed new mapping scheme can achieve a maximum improvement of channel capacity of 1.18bit / channel compared with the traditional Gray mapping scheme. Combining low density parity check (LDPC) code and external information transfer (EXIT) graph, the scheme has good performance advantages and application prospects in optical communication system.