中文摘要：

首先给出了受一阶偏振模色散（PMD）影响的40Gbit／s高斯脉冲信号功率谱的数学表达式，并分析了脉冲波形、分光比、监测频率以及差分群延时（DGD）对接收信号功率谱的影响。实验测量了在分光比为0．5时的40Gbit／s归零（RZ）码伪随机信号在接收频率为12GHz处的电功率谱密度随DGD变化的关系，实验结果与理论计算一致。这表明，对于40Gb／s的光纤通信系统，可以通过简单地检测某一特定频率的电信号功率，动态跟踪系统中PMD的变化情况，从而为补偿一阶PMD提供了重要依据。

英文摘要：

The mathematical expression of the signal power spectrum for 40 Gb/s Gauss pulse signal with the effect of firstorder PMD is given, and the effects of pulse waveform, splitting ratio, monitor frequency, and differential group delay （DGD） on the receiver signal power spectrum are analyzed. The rdationship between signal power spectrum and DGD is measured by the experiment under the splitting ratio of 0.5, and the experiments well demonstrate the theoretical analysis. The result shows that first-order PMD in the 40 Gb/s optical communication system can be dynamically monitored by a certain frequency electrical signal power,which is an important basis of first order PMD compensation.