The transmission of information through optical fiber is affected by various types of dispersions which reduce the efficiency and hence data carrying capacity of a fiber .But the most important kind of dispersion which affects a lot on the performance of the fiber is Polarization Mode Dispersion, PMD. PMD can cause the optical receiver to be unable to interpret the signal correctly, and results in high bit error rates. This paper demonstrates the broadening of pulse caused by polarization mode dispersion (PMD).