文章把网格编码调制(TCM)引入到光脉冲位置调制(PPM)中，研究其对光PPM系统误码性能的改善。通过理论推导及对8T-PPM、16PPM和16T-PPM、32PPM分别进行MATLAB仿真，得到以下结论：在保持带宽不变的前提下，8T-PPM与16PPM信息速率相同，但前者误码性能优于后者，且最大达到4.8 dB；虽然16T-PPM的信息速率是32PPM的1.2倍，但前者误码性能优于后者,且最大可达到3.4 dB。TCM确实能有效地改善系统的误码性能。

Trellis Coded Modulation(TCM)is introduced into PPM to investigate the error performance improvement in optical Pulse Position Modulation (PPM) systems. Theoretical deduction and MATLAB simulation and comparisons of 8T-PPM with 16 PPM and 16T-PPM with 32 PPM respectively, produce the following results. When the bandwidth is kept constant, 8T-PPM and 16 PPM have the same information rate, but the error performance of the former is better than the latter, up to 4.8 dB at the maximum. On the other hand, the information rate of 16T-PPM is 1.2 times that of 32PPM, but it has better error performance, up to 3.4 dB at the most. These results prove that the introduction of TCM into PPM does effectively improve the error performance of the system.