Monitoring of OSNR using statistical moments of equalized signal in 16-QAM coherent optical receivers

Among the wide spectrum of optical performance monitoring (OPM), optical signal-to-noise ratio (OSNR) monitoring is very important as it signify a direct measure of signal quality. In this paper, we propose a novel method of OSNR monitoring from the second- and fourth-order statistical moments of equalized signal in 16-QAM coherent optical receivers. The distinct statistical nature of carrier signal and noise enables such estimation. The proposed scheme is verified using computer simulation of 10-Gsymbols/s 16-QAM optical transmission systems. It is found that our scheme can estimate the OSNR with less that 0.5-dB error over a wide monitoring range.