Polarization-Mode-Dispersion Monitoring for Phase-Modulated Signals Using DGD-Generated Interferometric Filter

We propose and experimentally demonstrate a chromatic-dispersion (CD)-insensitive polarization-mode-dispersion (PMD) monitoring technique for phase-modulated signals utilizing the destructive response of a differential-group-delay (DGD)-generated interferometric filter. The detected radio-frequency (RF) power through this filter has a defined relationship to the accumulated DGD (i.e., first-order PMD), and thus the variations in power level of the low RF frequency are measured for monitoring. The experimental results show that this technique can monitor 0 ~ 100 ps of DGD with ~ 20-dB RF power variation, in 10-Gb/s nonreturn-to-zero (NRZ) differential phase-shift-keying and 20-Gb/s NRZ differential quadrature phase-shift-keying systems, which is insensitive to 0 ~ 640 ps/nm CD. The applicability of this monitoring technique to higher bit-rate phase-modulated signals is also investigated via simulation.