THE EFFECT OF CROSSTALK AND PHASE NOISE IN MULTICHANNEL COHERENT OPTICAL DPSK SYSTEMS WITH TIGHT IF FILTERING

We extend the analytical model of Foschini and Vannucci [1] for the effect of IF filtering of phase and receiver noise to a two-channel system and to a general class of IF filters and we generalize earlier work by Blachman and Nicholson [2], [3] in order to evaluate DPSK system bit-error-rates. We carry out a comprehensive study of the sensitivity of an optical receiver in a two-channel DPSK system. This is the first time, to our knowledge, that this important problem has been addressed with any predictive accuracy. We compare our results with previous work in the limit of no phase noise and show that the agreement is good. We compute the penalty due to crosstalk for different linewidths and filter shapes and show that the minimum channel spacing is a few bit rates for an ideal integrator IF filter and is larger for an IF filter with a raised cosine impulse response. The penalty is increased somewhat by phase noise.