Using multiple importance sampling technique, the power penalty and outage probability of 10Gbit/s lightwave transmission system impaired by polarization-mode dispersion (PMD) and polarization-dependent loss (PDL) were investigated. The simulation results show that optical filter has significant influence on the power penalty, and the system with Fabry-Perot filter always performs better than that with four-order Gaussian filter. It is also found that the power penalty generally increases with the increasing of chirp factor, but the system performs best when chirp factor is about 0.5. It also demonstrated that DPSK is still more robust to PMD and PDL than OOK even though PMD and PDL coexist.