Analysis of SNR penalty in coherent WDM receiver system for detection of QPSK signal with component crosstalk

Abstract

We propose analytical modelling of component crosstalk on the performance of wavelength division multiplexed (WDM) receiver with generalized quadrature phase shift keying (QPSK) signal and coherent detection. A comprehensive study on the signal-to-noise ratio (SNR) penalty is conducted, which can be used to balance SNR values and the system's power budget in the presence of finite crosstalk sources. Results express that, in the presence of five crosstalk interferers, the crosstalk level leading to 1-dB of SNR penalty must be less than -23.8 to -26.5 dB for bit error rate (BER) from 10^–7 to 10^–13. For the BER of 10^–9, the QPSK signal has a component crosstalk tolerance of -21.7 dB for a 1 dB SNR penalty with a single interferer. Furthermore, the study of spectral efficiency reveals that crosstalk level, SNR, and the number of active interferers perform a vital role in determining the bandwidth efficiency of the system. The analysis exploits the characteristic function method and Maclaurin series expansion to compute a closed form expression of BER over additive white Gaussian noise (AWGN) channel. Following the analysis, the SNR and bandwidth expenses of the system are examined numerically through the estimated BER and binary entropy function. The estimated values of the BER using the proposed model are in close agreement with a similar theoretical investigation for a single interferer.