CD and PMD Monitoring Based on RF Spectrum Analysis with Optical Filtering

Abstract

Chromatic dispersion (CD) and polarization-mode dispersion (PMD) monitoring methods based on radio-frequency (RF) spectrum analysis and optical filtering are demonstrated. By using a narrow band fiber Bragg grating (FBG) notch filter, which is centered at 10GHz away from carrier, 10GHz RF power can be used as a CD-insensitive PMD monitoring signal. By taking the 10GHz RF power ratio of non-filtered and filtered signal, PMD-insensitive CD monitoring can be achieved. If the FBG notch filter is placed at optical carrier, the RF clock power ratio between non-filtered and filtered signal is also a PMD-insensitive CD monitoring parameter, which has larger RF power dynamic range and better measurement resolution. Both simulation and experiment results show that the proposed methods are efficient on measuring CD and PMD values in 38-Gbit/s DQPSK and 57-Gbit/s D8PSK systems.