The effect of crosstalk and phase noise in multichannel coherent optical ASK systems

The authors extend the analysis of G.J. Foschini et al. (1988) to a two-channel system and to a wider class of IF filters. The authors 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. They compare the results with previous work in the limit of no phase noise and show how the agreement is good. They compute the penalty due to crosstalk for different linewidths and filter shapes. It is shown 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. The detailed IF filter shape appears to have only a weak effect