Performance limits of first-order PMD compensators using fixed and variable DGD elements

In this letter, we analyze optical polarization-mode dispersion compensators using a single differential-group-delay (DGD) element that is either fixed or variable. We evaluate the upper-bound performance limits, and quantify the compensator performance under dynamic operations. We show that the variable-delay compensator can reduce the risk of feedback loops trapping a locally optimized state. Moreover, the variable-delay approach provides superior performance as compared to a fixed-delay compensator by increasing the optimal system tolerance for a 10-Gb/s nonretum-to-zero signal from 28 to 33 ps of average link DGD.