Influence of local oscillator-to-signal power ratio on the gaussianity of CP-QPSK signal statistics
; Fonseca, D.
Influence of local oscillator-to-signal power ratio on the gaussianity of CP-QPSK signal statistics, Proc International Conf. on Transparent Networks – ICTON , Stockholm, Sweden, Vol. Tu.C1.6, pp. -1 - -4, June, 2011.
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The statistics of quadrature phase-shift keying with coherent-detection and polarization multiplexing (CP-QPSK) signal at the decision circuit input is assessed by numerical simulation for different local oscillator-to-signal (LO/S) power ratios. It is shown that the signal statistics at the decision circuit input is approximately Gaussian distributed for high LO/S power ratios. However, the mean and variance of the Gaussian distribution that approximates the statistics of each symbol depend on the transmitted symbol sequence, especially for low LO/S power ratios, demonstrating the impact of the waveform on the statistics of the detected signal. Moreover, the signal statistics starts to deviate from Gaussian for LO/S power ratios below 17 dB.
A semi-analytical simulation method (SASM) based on the Gaussian approximation for the signal statistics at the decision circuit input is used for performance evaluation of CP-QPSK system. The accuracy of the SASM is assessed for different LO/S power ratios by comparison with Monte-Carlo (MC) simulation results. The SASM shows good agreement with MC simulation results for LO/S power ratios between 6 and 30 dB.