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信息传输材料与技术---传输非线性信息传输材料与技术---传输非线性ThreefundamentallimitingfactorsinU-DWDMSystemsinclude: 1)variousrandomnoiseterms; 2)fiberchromaticdispersion-inducedintersymbolinterference(ISI); 3)optical-nonlinearity-induceddistortionandinterference.MLMLaserSpectralOutputDispersionwithaNormalDFBLaserPolarizationModeDispersion(PMD)(a)GeneralU-DWDMsystemmodel.(b)PeriodicallyamplifiedU-DWDMsystemmodelwithpostdispersioncompensationineveryamplifierstage.thenonlineareffectshavebecomeevenmoreimportantsincethedevelopmentofEDFAandWDMsystems.Thenonlineareffectscanbedividedintotwocategories. duetheinteractionoflightwaveswithphonons.ItcontainstwoimportantnonlinearscatteringeffectsSRSandSBS. TheeffectsthatarerelatedtotheKerreffect,theintensitydependenceonthenonlinearrefractiveindexoftheopticalfiber. Themaineffectsare:SPM,XPMandFWM. alsocontainseffectscalledmodulationinstabilityandsolitonformation.Thesenonlineareffectsarecharacterizedandinfluencedbyseveralparameters, Including: dispersion, effectiveareaoftheopticalfiber, overallunregeneratedsystemlength, channelspacinginmulti-channelsystems, thedegreeoflongitudinaluniformityofthefibercharacteristics, sourcelinewidthandintensityofthesignal.Effectivelength,Leff,hasproventobequitesufficientinestimatingtheeffectofnonlinearities.Mostofthenonlineareffectsoccurinthebeginningofthefiber.Therelationbetweentherefractiveindexn, intensityIandpowerPis:Self-PhaseModulation(SPM) Self-phasemodulation(SPM)inducesphaseshiftthatis proportionaltotheopticalpower.Itcanbeunderstoodas amodulation,wheretheintensityofthesignalmodulates itsownphase. IntheSPMdifferentpartsofthepulseundergooptical powerdependentphaseshifts,leadingtobroadeningof thepulsespectrum.Misthetotalnumberofchannelsandpjisthechannelpower(j=1toM)Nonlinearscatteringcontainstwoimportantphenomenacausedbyinteractionoflightwithphonons.SBSandSRS SBSoccurswhenanintenselightbeamscattersfromanacousticphonon.SRStakesplacewhenopticalphononisinvolved. SBSoccursmainlyinthebackwarddirectionwhileSRScanoccurinboth