Geometric Constellation Shaped Non-Linearity Tolerant Optical Communication System

In any communication system, constellation shaping may be employed to increase the overall capacity of the system. In this paper, constellation shaping is investigated as a potential non-linearity tolerant method in coherent optical communication system. Geometric constellation shaping of 16-Quadrature Amplitude Modulation (16-QAM) back-to-back coherent system is implemented, and improvement in nonlinearity tolerance of the system with respect to regular 16-QAM coherent system is investigated. BER performance and non-linear interference analysis is carried out to present the insight of the levels of error rate and non-linearity tolerance in different geometric constellation shaped QAM systems over a non-linear channel. The values obtained for non-linearity interference noise (NLIN) variance for different geometric shapes like square, circular and star are −26.21 dBm, −27.39 dBm and −28.48 dBm respectively which is attributed to decrease in the values of standardized moments of input over the various constellation shapes.