PMD has been the major limiting factor for long haul high bitrate optical fiber transmission. The relationship between 1st order PMD and optical signal DOP (degree of polarization) of PRBS NRZ/RZ is discussed in theory, and the impacts of different input states of polarization and higher-order PMD on signal DOP of NRZ/RZ are analyzed by numerical simulations. Then, Monte-Carlo simulations are performed with all order PMD model on the statistics of PMD compensator, which uses signal DOP as the feedback control signal in the 10 Gbit/s NRZ optical transmission system. The statistical simulation results indicate that the compensation probability for the signal eye-diagrams can reach 99.99% when the average DGD of the link is below 43 ps.