Performance degradation induced by polarization-dependent loss in optical fiber transmission systems with and without polarization-mode dispersion

The performance degradation caused by polarization-dependent loss (PDL) in optical fiber transmission systems in both the absence and presence of polarization-mode dispersion (PMD) is studied. First a simple theory is given to show how PDL affects the system performance and then extensive simulation results are presented. We show that PDL causes a much larger fluctuation of optical-signal-to-orthogonal-noise ratio (OSNR_ort) than that of optical-signal-to-parallel-noise ratio (OSNR_par), but OSNR_par has a much larger impact on the system performance than OSNR_ort. We find that when there is no PMD, the system performance degradation induced by PDL can be effectively reduced by suppressing OSNR_par fluctuation. However, the presence of PMD in the system could significantly reduce the efficiency of the PDL mitigation technique, especially the mitigation technique that suppresses the OSNR_par fluctuation.