Study Of Filter In3U Optical Network

With the rapid increase of capacity of backbone network, the optical communicationsystem is gradually evolving into ultra high speed, ultra large capacity and ultra long haul(3U) network. In the3U optical communication system, the filer can be used to compressspectrum, process high speed signal and so on. By theoretical and numerical investigation,the filters in3U optical network are studied in this paper, including the followings:By theoretical study of finite impulse response(FIR) digital filter, based on theWiner-Hopf equation instructed by least square error(LSE) criterion, a time domain equalizeris designed to process the inter symbol interference(ISI). The effect of ISI processing of thetime domain equalizer is tested by Matlab and OptiSystem. The result indicates that athree-level equalizer can erase most of the ISI caused by fiber dispersion.Pre-filtering is an important technology to compress spectrum in optical communicationsystem. By theoretical analysis pre-filter detuning, we reveal the cause of detuning brings ISIimprovement is that detuning brings reduction of base band flatness for the first time.Further numerical study shows that: the base band flatness plays a decisive roll on systemperformance in small detuning situation; the detuning of ratio of high frequency and lowfrequency result in a rapid degradation of system performance with the increase of detuning.Optical lattice form filter can realize arbitrary frequency characteristic FIR filter inoptical domain and it dose not has speed and tunnel limitation. In this thesis, by theoreticalanalysis of optical lattice form filter, we construct multi-level parameters designingalgorithm of optical lattice form filter base on matrix, and verify the algorithm by anexample of Chebyshev filter. The numerical analysis indicates that optical lattice form filterof more than twenty level can realize high precision signal process in frequency domain.