THE EFFECT OF CROSSTALK AND PHASE NOISE IN MULTICHANNEL COHERENT OPTICAL ASK SYSTEMS

We extend the analysis of Foschini et al. [1] to a two-channel system and to a wider class of IF filters. We carry out a comprehensive study of the sensitivity of an optical receiver in a two-channel ASK system, taking into account phase noise and crosstalk, including crosstalk arising from phase noise in the second channel. 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. We show that the minimum channel spacing is a few bit rates more than the IF filter bandwidth, and is therefore increased significantly by significant phase noise. For a linewidth in each channel of 0.57 times the bit rate and a finite integrator IF filter the required channel separation to have less than 1-dB penalty due to crosstalk is 8.3 times the bit rate compared to 3 times the bit rate with no phase noise. The detailed IF filter shape appears to have only a weak effect.