Performance of an OSNR monitor based on the polarization-nullingtechnique

Feature Issue on Optical Performance Monitoring (OPM). We report on the performance of an optical signal-to-noise ratio (OSNR) monitor with the polarization-nulling technique. The results show that this monitor was robust to polarization-mode dispersion and in-band cross talk. For a demonstration, we monitored the OSNR of the optical signal transmitted through a 2×60 km long aerial fiber link for one week and confirmed that the OSNR could be measured with accuracy better than ±0.3 dB (when the OSNR is lower than 26 dB).