Polarisation-mode dispersion impairments in direct-detection differential phase-shift-keying systems

Evaluation of the system performance degraded by first-order polarisation-mode dispersion (PMD) for non-return-to-zero (NRZ) or return-to-zero (RZ) differential phase-shift-keying (DPSK) signals is presented. The PMD-induced power penalties were measured with a PMD emulator for an optically preamplified receiver. The results show that the PMD sensitivities of DPSK signals are comparable with on-off keying signals.