针对100 Gbit/s及以上PM QPSK(偏振复用正交相移键控)相干光通信系统，提出了一种改进的基于统计矩的带内OSNR(光信噪比)监测方案，并在搭建的100 Gbit/s PMQPSK相干接收系统中对该方案进行了数值仿真。结果表明,在5～25 dB的OSNR范围内,该改进方案对不同占空比的RZ(归零)码调制信号的监测误差均小于0.5 dB;根据商用相干接收机对接收端OSNR的要求，取其参考值为14 dB，则在0.5 dB的监测范围内，对CD(色散)的容忍度为2 400 ps/nm，对一阶PMD(偏振模色散)即DGD(差分群时延)的容忍度为62 ps。

For 100 Gbit/s (or above) Polarization MultiplexedQuadrature Phase Shift Keying (PMQPSK) optical coherent transmission systems, we propose an improved statistical momentbased intraband OpticalSignalNoiseRatio (OSNR) monitoring method and carry out its numerical simulation in such an established system. The results show that when this method is used, all the monitoring errors of RZ code modulated signals with different duty cycles are smaller than 0.5 dB in the OSNR range of 5～25 dB and in line with the requirement of the commercially available coherent receivers for the OSNR at the receiver end, taking the reference value of 14 dB, the system Chromatic Dispersion (CD) tolerance is 2 400 ps/nm and that for the 1storder Polarization Mode Dispersion (PMD), i.e. Differential Group Delay (DGD), is 62 ps/nm in the monitoring range of 0.5 dB.