Performance Comparison of Electronic PMD Equalizers for Coherent PDM QPSK Systems
Polarization Division Multiplexed (PDM) Quadrature Phase-Shift Keying (QPSK) coherent optical systems employ blind adaptive linear electronic equalizers for Polarization-Mode Dispersion (PMD) compensation. In this paper, the authors compute the performance of various adaptive, fractionally spaced, feed-forward electronic equalizers, using the outage probability as a criterion. A parallel programming implementation of the multi-canonical Monte Carlo method is developed, which automatically performs concurrent loop computation on multi-core processors, for the estimation of the tails of the outage probability distribution. The Constant Modulus Algorithm (CMA), the Decision-Directed Least Mean Squares (DD-LMS), and their combination are applied for the adaptation of electronic equalizer filter coefficients.