利用将任意非圆性等效为椭圆的方法分析和计算了单模光纤中包层和芯层折射率分布不同心导致的偏振模色散 ,得到了两个偏振模式的传输常数差Δβ和偏振模色散Δτ与偏心比、入射光的波长、芯层半径、相对折射率差的关系曲线 ,为实践中尽量减小单模光纤的偏振模色散提供理论上的指导。与椭圆度引起的偏振模色散相比 ,不同心引起的偏振模色散具有相同的数量级。 The polarization mode dispersion caused by the different refractive index distribution of the cladding and the core in the single mode fiber was analyzed and calculated by using any noncircular equivalent elliptical method. The difference of the transmission constants Δβ and Pm of the two polarization modes was obtained. The relationship between dispersion Δτ and eccentricity ratio, incident light wavelength, core radius and relative refractive index difference provides theoretical guidance for minimizing the PMD of single-mode fiber in practice. Polarization mode dispersion caused by different centers is of the same order of magnitude as polarization mode dispersion caused by ovality.