Application of the saddle point method for the evaluation of crosstalk implications in an arrayed-waveguide grating interconnection

The effect of in-band crosstalk can pose severe limitations in an optical network. In this paper, the implications of in-band crosstalk induced by an arrayed-waveguide grating (AWG) router in a passive N x N optical interconnection are analyzed with non-Gaussian statistics using a numerical model. The model is based on the saddle point approximation and takes into account fluctuations of the transfer function's sidelobes induced by the phase errors in the grating arms, phase noise, polarization variations, bit misalignment, and shot and thermal noise. The influence of these effects on the interconnection's bit error rate (BER) is analyzed. The validity of the Gaussian assumption for the crosstalk noise statistics is discussed. Finally, the model is used to examine the mean crosstalk requirements for various numbers of network nodes.