光纤通信课程设计课件Class4-03.pptx
Class 3Class 3FWM:definition&origin FWM in fiber,effect on WDMHow to reduce it&simulationSolutionsPolarization allocationUnequal channel spacingDispersion managementDefinition:Nonlinear effect that occurs in nonlinear optical materials such as photonic switch,optical fiber cable,etc.This interaction between waves leads to interaction between channels generatesoneormorenewchannels(orharmonics).Forinstance,whenthreewavesatfrequenciesfi,fj,andfktraverseafibertheygenerateanothersignallocatedatTheeffectsofFWMFiberExample:Theinputistwosignalslocatedat 1and 2traverseafiberoflength(L)andtheoutputisfourdifferentsignalslocatedat 1,2,2 1-2,and2 2-1.Ingeneralthenumberofnewlygeneratedsignalsisgivenby Where Pi,Pj,Pk are the input power of the channels D is the degeneracy factor 3 and 6 for two-tone and 6 for three-tone product Where Aeff is the effective cross-sectional area and Leff is the effective length of the fiber given byThe power of of newly generated signals is given by And is given byThenonlinearsusceptibility 1111TheefficiencyisgivenbyWhere fmn=fm-fn,(m,n=1,2,3)ThefollowingfiguredemonestratestheeffectofFWMwhenFoursignalswithequallypower3mwtraversesafiberwiththefollowingspecificationsDescriptionValuesAttenuationfactor()0.2dB/kmEffectivefibercross-sectionalarea(Aeff)6.4x10-11m2Thirdordernonlinearsusceptibility(1111)6x10-15cm3/ergChromaticdispersion(Dc)1ps/nm.kmDispersionslope().07ps/km.nm2Refractive-index(n)1.48LengthL75kmWavelength()1550nmTheOriginalinputsignalsThe newly generated signals and their corresponding power in dBm The newly generated signals and their corresponding power in dBm after filtration The original and the newly generated signals after filtration as well as their corresponding power in dBm Origin of FWMEffect on WDM systems SolutionsPolarization AllocationUnequal Channel SpacingDispersion Management Origin of FWM 1Third order nonlinearityEnergy ConservationMomentum Conservationphase matchingOrigin of FWMPhase Matching 2 Effects on WDM Systems 2When Channelspacing and fiberdispersion are small enoughPhase Match ConditionsThe efficiency curve versus the channel separation in(GHz)&dispersion slopesEffects on WDM Systems 3Nonlinear Crosstalkequally spacing,product terms fallat channel frequencyCoherent interferenceEffects on WDM Systems 4Bit patternPower DepletionEffects on WDM SystemsSolutionsPolarization AllocationUnequal spacingDispersion managementPolarization Allocation 5Polarization Allocation 5Polarization Allocation 5Add polarization filter at the receiver endUnequal Channel Spacing 6Unequal Channel Spacing 6Dispersion-Management 4No dispersion-zero pointTotal accumulated dispersion near zero Dispersion Management 7Dispersion map for dispersion-compensating fiber(DCF)Small core areaNew Type of FibersLarge effective area fiberNonzero dispersion shifted fiber(NZ-DSF)Large-effective-area fiber(red)suppressed four-wave mixing crosstalk to-22.5 dB,compared to-19.0 dB for NZ-DSF fiber(blue).References1 G.Agrawal“Nonlinear Fiber Optics”,3rd edition2 G Agrawal“Fiber-Optics Communication Systems”3rd edition3 Nori Sibata,Ralf Braun and Robert Waarts,IEEE J.Quantum Electron.QE23,1205,19874 Ivan Kaminow and Thomas Koch,OFT IIIA5 C.Mahon,L.Olofsson,E.Bodtker,G.Jacobsen,IEEE Photon.Tech.Lett.8,575,19966 F.Forghieri,R.Tkach,A.Chroplyvy,J.Lightwave Tech,13,889 19957 R.Tkach,R.Derosier and et.al,IEEE Photon.Tech.Lett.7,1369,1995Noise Contributions in Optical Systems and detection I.ThermalNoise:kisBoltzmannconstant,TistheabsolutetemperatureinKelven,BisthereceiverelectricalbandwidthandRistheloadresistancevalue.II.ShotNoiseWhereqistheelectroniccharge,IisthemeanopticallygeneratedcurrentandIdisthephotodetectordarkcurrentIII.RelativeIntensityNoise(RIN):TheOpticalSignal-to-NoiseRatio(OSNR)isgivenbyWhere isgivenbyThenoiseduetoFWMphenomenonisgivenbyReferenceThebiterrorrate(Pe)versusthequalityfactorQNow,thequestion:howtoincludetheeffectofFWMinthefibermetricsI.Based on the system design target,which is mainly the BER,Q(or OSNR)can be evaluated from the BER curve.II.The noise in the system can also be calculated(mainly Nth,Nsh,and NFWM).III.From step I and II,the required received power(Prec)thus can be calculated.IV.Using the Power budget equation,the maximum fiber length(Lmax in km)can be calculated as follow
