EFFECT OF POLARIZATION MODE DISPERSION ON A COHERENT OPTICAL-SYSTEM WITH PILOT CARRIER

The effect of fiber polarization mode dispersion (PMD) on a coherent o ptical system with pilot carrier is twofold. First, the PMD causes sta te of polarization (SOP) mismatch between the message signal and pilot carrier. Second, the degrees of polarization (DOP) of the message sig nal and pilot carrier are degraded by PMD. Because coherent reception relies both on the SOP's and DOP's of the waves, system performance is degraded by PMD. The effect of SOP mismatch causes intermediate frequ ency (IF) signal amplitude degradation whereas DOP variation not only results in IF signal amplitude degradation but further induces IF nois es. Here we derive analytical expressions to evaluate the performance degradation. It is shown that there is no performance degradation if o nly one principle state of polarization is excited and maximum degrada tion occurs when both principle states of polarization are equally exc ited. We also find that significant degradation may happen when large differential group delay exists.