The impact of the signal and nonlinearity extinction ratios on the optimum parameters of a reamplification and reshaping (2R) all-optical regenerator is investigated for different nonlinearity characteristic shapes. The bit error ratio (BER) is numerically evaluated along the 2R all-optical regenerator chain using the rigorous distribution and the Gaussian distribution for the optical power. It is shown that, when the extinction ratio of the signal at the transmitter output decreases, the optimum nonlinearity threshold increases. The results also show that, independent of the nonlinearity characteristic shape, the requirements on the extinction ratio of the nonlinearity can be strongly relaxed when the extinction ratio of the nonlinearity is higher than the extinction ratio of the signal at the transmitter output. Numerical results show that, only for nonlinearities with a small degree of nonlinearity and small extinction ratio, the Gaussian distribution correctly estimates the optimum regenerator parameters. For a small extinction ratio of the nonlinearity or a small extinction ratio of the signal at the transmitter output, the Gaussian distribution only provides correct estimates of the minimum BER along the regeneration chain. Furthermore, for high and moderate extinction ratios and degrees of nonlinearity, and for high and moderate extinction ratios of the signal at the transmitter output, the Gaussian distribution fails to correctly estimate the optimum regenerator parameters and minimum BER.
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