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Summary: A MAP EQUALIZER FOR THE OPTICAL COMMUNICATIONS CHANNEL
Wenze Xi, Tšulay Adali, and John Zweck
Department of Computer Science and Electrical Engineering
University of Maryland Baltimore County, Baltimore, MD 21250
ABSTRACT
A maximum a posteriori equalizer is presented for optical
communication systems. Assuming that the span of the
inter-symbol interference (ISI) does not extend beyond the
neighboring bits as is typically the case for the distor-
tion introduced by polarization mode dispersion (PMD)
we derive the conditional probability distribution function
in the electrical domain in the presence of PMD and am-
plifier spontaneous emission dominated noise. Simulation
results with an accurate receiver model and all-order PMD
show the success of the MAP equalizer in reducing the ISI
due to PMD, and that the analytical conditional pdf we de-
rive provides a good match to the actual distribution.
1. INTRODUCTION
In optical fiber communications systems, physical impair-
ments in optical fibers, in particular, chromatic dispersion,
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