Date Added: Jun 2010
Spectrally-efficient optical communications systems employ Polarization Division Multiplexing (PDM) as a practical solution, in order to double the capacity of a fiber link. Polarization de-multiplexing can be performed electronically, using polarization-diversity coherent optical receivers. The primary goal of this paper is the optimal design, using the maximum-likelihood criterion, of polarization-diversity coherent optical receivers for polarization-multiplexed optical signals, in the absence of Polarization Mode Dispersion (PMD). It is shown that simultaneous joint estimation of the symbols, over the two received states of polarization, yields optimal performance, in the absence of phase noise and intermediate frequency offset.