Performance evaluation of optical cross-connects by improved saddlepoint approximation

Based on the wave theory of light and taken the random polarizations of signal and crosstalk into consideration, bit error rate (BER) and power penalties (PP) of optical cross-connects are calculated using the so-called saddlepoint approximation which is improved. The calculated results agree well with the results of experiment and Gauss approximation, shown highly calculated precision of the improved saddlepoint approximation. We also show that BER and PP for systems with random-polarizations are much smaller than that for systems with matched-polarizations when the number N of crosstalk is large, and the conclusion of near-worst-case operation is true only for N<3, so the impact of random signal and crosstalk polarizations on optical cross-connects must be considered in the design for lightwave networks.