Abstract: In order to study the performance deterioration induced by polarization mode dispersion(PMD)in a fiber link, the effect of 1st order and 2nd order PMD on the non-return-to-zero(NRZ),return-to-zero(RZ)and chirped return-to-zero(CRZ)codes was analyzed by means of the split-step Fourier method based on the coupled nonlinear Schrodinger equation. The analytical results show that the performance of the optical fiber link is severely deteriorated by PMD,one of the main factors limiting the property of the link. And with the increase of the working speed,the influence of higher-order PMD becomes worse. The effect of PMD can be partially reduced for a right code pattern,i. e.,CRZ code is a little better than RZ code and RZ code is better than NRZ code.