Equalizer Architectures for 40-Gb/s Optical Systems Limited by Polarization-Mode Dispersion

An analysis of first-order polarization-mode dispersion (PMD) effects in a 40-Gb/s optical system is used to compare different electronic equalizer architectures as potential PMD compensators. Both linear and nonlinear equalizers are considered employing symbol-spaced and fractionally-spaced taps. It is found that a decision feedback equalizer consisting of a 3-tap symbol-spaced feedforward equalizer and a 1-tap feedback equalizer effectively eliminates PMD as the dominant length-limiting factor in most 40-Gb/s optical systems. Such an equalizer would entail less complexity than several previously reported electronic PMD compensators.