A Joint OSNR and Nonlinear Distortions Estimation Method for Optical Fiber Transmission System

In this paper, we propose and demonstrate a joint optical signal-to-noise ratio (OSNR) and a nonlinear distortions estimation method. The OSNR is calculated by considering either the link parameters or the correlation operations of the training symbols. The nonlinear distortions estimation in this calculation comes from different nonlinear sensitivities of these two methods. The indicator of NL penalty is defined as the ratio of nonlinear distortion power to the signal power. As the estimation method, based on link parameters, has low computational complexity, and the training symbol used for the OSNR estimation is inherently indispensable for frame synchronization, this nonlinear distortion estimation method introduces a few complexities and no extra overhead. Experimental results obtained by using a 200 Gb/s 16 QAM DWDM system establish the accuracy of the proposed OSNR estimations method, with errors less than 1 dB. The nonlinear distortions were also measured under different simulation conditions, using a coherent optical OFDM system, and the results are in accordance with the expectations.