Abstract: In order to reduce influence of polarization mode dispersion(PMD) on the quality of transmission signal, an optical circulator was applied in the front-end of the optical amplifier of the optical transmission network. The effect of PMD in optical transmission network was simulated. After PMD suppression, transmission eye diagram opened more obviously. Transmission performance of the system was improved to a certain extent.The PMD in the optical transmission network was suppressed to a certain extent, and the quality of signal was effectively improved. The results show that the bit error rate of PMD decreases about one time with and without the optical circulator. The optical circulator has a significant inhibitory effect on PMD in the optical transport network. The polarization delay at different transmission speeds is compensated equivalently with this scheme so that the PMD is compensated finally.