均衡效果好，这是基于最大似然估计的均衡器-With the development of high-speed optical fiber communication systems, polarization

mode dispersion (PMD) has become a vital limiting factor. However, the traditional

compensation methods which in optical domain have the disadvantages of complexity and cost.

In recent years, the compensation methods which in electronic domain are given more attention

because of their outstanding price advantage and their strong adaptability.

The maximum-likehihood sequence estimation (MLSE) equalizer based on the Viterbi

algorithm was designed in this paper.The MLSE equalizer can effectively compensate the

intersymbol interference caused by polarization mode dispersion (PMD). First, the background

and the spectrum of the text were introduced　also the principles of PMD and the FFE/DFE

equalizer were analysed. Second, the principles of Viterbi and the structure of MLSE were

researched　also the MLSE equalizer was simulated with the Matlab program in the optical fiber

communication systems. T