Study On Electronic Dispersion Compensation In Optical Fiber Communication Coherent Detection System

Overcome polarization-mode dispersion (PMD) has became an important skill in 40Gsystem,PMD compensation can be achieved either optically or electronically,but electroniccompensation schemes are attracvive because they have simple structure, leading to compact,lessexpensive and won't introduce light loss, etc. Adaptive linear FFE is effective at compensatinginter-symbol interference(ISI) caused by PMD, but the FFE in compensation channel will alsoamplify the noise of the system,which degrades the overall signal-to-noise ratio (SNR), butnonlinear DFE has feedback part which will not be affected by the noise gain, therefore betterperformance than the FFE.This paper based on 0.18μmCMOS integration process studies the folding cascade TWFstructure with 3 taps in 40Gb/s system.Firstly, in this paper, we described the structures of DFEin the feed forward and feedback filter were discussed, including transverse filter (TF),transverse wave filter structure (TWF) and its two kinds of improvement structures, three analogcontrol voltages control the gain for each of the taps,the main benefit of this architecture is that itallows the level of distribution of the transmission lines to be chosen independently of thenumber of equalizer taps.After that, we carried out a detail study of the implementation approachof the circuit structures of DFE. And two parts simulation were carried out. The first part wastime-domain simulation by using MATLAB; we theoretically verified the equalizer couldcomplete its dispersion compensation in 40 GB/s system; the second part was S parameterssimulation, we verified the power gain and the match of the input and output through thissimulation. We can see that effective compensation of PMD can be achieved using DFE .