In Polarization-Mode Dispersion, various polarization states of the optical signal propagate at different velocities. PMD affects the transmission quality by spreading the signal pulses and, therefore raising the BER of the system. Its effects prevent many present day optical systems from using high bandwidth transmission. PMD can be a serious limitation to the system performance and particularly when the system is upgraded.The AutoCorrelation Function of the PMD vector, gives the exact knowledge of the bandwidth over which first-order PMD is applicable. PMD compensators offer benefits by reducing PMD induced pulse broadening.