Open AccessEqualization of nonlinear transmission impairments by maximum-likelihood-sequence estimation in digital coherent receivers
Author(s) -
Md. Khairuzzaman,
Chao Zhang,
Koji Igarashi,
Kazuhiro Katoh,
K. Kikuchi
Publication year - 2010
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.18.004776
Subject(s) - maximum likelihood sequence estimation , adaptive equalizer , computer science , phase shift keying , bit error rate , viterbi algorithm , keying , finite impulse response , equalization (audio) , intersymbol interference , electronic engineering , algorithm , estimation theory , telecommunications , decoding methods , engineering
We describe a successful introduction of maximum-likelihood-sequence estimation (MLSE) into digital coherent receivers together with finite-impulse response (FIR) filters in order to equalize both linear and nonlinear fiber impairments. The MLSE equalizer based on the Viterbi algorithm is implemented in the offline digital signal processing (DSP) core. We transmit 20-Gbit/s quadrature phase-shift keying (QPSK) signals through a 200-km-long standard single-mode fiber. The bit-error rate performance shows that the MLSE equalizer outperforms the conventional adaptive FIR filter, especially when nonlinear impairments are predominant.