When attenuation and chromatic dispersion are compensated for

polarization mode dispersion （PMD） in optical fibers is regarded as one of the dominant obstacles in optical communication systems having bit rates of 40 Gbit/s and beyond and transmission distance of several thousand kilometers. From the simulation of second order PMD in 40 Gbit/s NRZ optical communication system

we found that high order PMD in optical fibers can degrade the 1st order compensation effect severely. In this paper

we also introduce two high order PMD compensators on the basis of PMD vector and Jones matrix respectively and the two staged higher order PMD compensator using a fixed differential group delay （DGD） section followed by a variable section is preferred.