在研究偏振模色散的数值模型中，分段数N和分段长度L是基本的参数，这两个参数影响到偏振模色散的随机特性。在分段级联模型理论的基础上，采用琼斯矩阵的分析方法，对偏振模色散的特征矩阵进行了理论分析和数值模拟，研究表明，N和L的选取对偏振模色散的分析有直接的影响，N在适当大的情况下，使得L在某一均值附近微小变化，这样的参数选取是合理的。如果各分段长度保持不变，会使得二阶偏振模色散丧失随机性的特点。

In numerical model for research on polarization mode dispersion(PMD), the number of the whole segments N and the length of each segment L are basic parameters, which affect the randomicity of PMD. Based on the theory of concatenated model, theoretical analysis and numerical simulation are made on randomicity of PMD with the method of Jones transfer matrix. Research results show that the selection of N and L has direct affection on the analysis on PMD. It is more reasonable while N is big appropriately and L vibrates around certain mean length. If equal length of each segment is chosen for analysis on PMD, the second-order PMD will lose the character of randomicity.