In-Band OSNR System Margin and Overall Link Impairment Level Monitoring Techniques Using an Optical Coherent Receiver

We propose a novel and in-service method for in-band OSNR system margin and overall link impairment level monitoring based on the use of an optical coherent receiver. This technique relies on the estimation of the ESNR margin of the received optical coherent channel, scaled by a correction factor which depends on the modulation format and the overall link impairment level. This method is demonstrated experimentally for a 120 Gb/s DP-QPSK channel in both dispersion and nondispersion managed links with different impairment scenarios.