The co-effects of the polarization mode dispersion (PMD), group velocily dispersion (GVD) and self-phase modulation (SPM) in high bit-rate transmission systems are studied. Both in time domain and frequency domain, the pulse evolutions are analyzed. It is proposed that chirp, GVD and SPM can be used to compensate PMD in certain conditions, for example, in the positive dispersion fiber (β 2<0), if selecting the pulse with initial positive chirp (C>0) or adjusting the input power, both can compensate PMD. The simulation results demonstrate that there exists the optimized input power to minimize the system penalty (in our simulation model that is 10 dBm). The optimization strategy would be helpful to the design of the 40 Gbit/s optical transmission system.