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Chapter11OpticalAmplifier12/15/20221TheSch.OfInformationEngineering,WHUTChapter11OpticalAmplifier1Usedroutinelyforlosscompensationsince1995AmplifytheinputsignalbutalsoaddsomenoiseSeveralkindsofamplifiershavebeendeveloped

semiconductoropticalamplifier

raman-basedfiberamplifiererbium-dopedfiberamplifierEDFAsareusedmostcommonlyforlightwavesystemRamanamplifiersworkbetterforlong-haulsystem12/15/20222TheSch.OfInformationEngineering,WHUT12/11/20222TheSch.OfInformaOUTLINEBasicconceptsSemiconductoropticalamplifier(SOA)RamanamplifierErbiumdopedfiberamplifierSystemapplicationofopticalamplifier12/15/20223TheSch.OfInformationEngineering,WHUTOUTLINEBasicconcepts12/11/20211.1Basicconcepts11.1.1Gainspectrumandbandwidth11.1.2

Gainsaturation

11.1.3Amplifiernoise11.1.4Amplifierapplications12/15/20224TheSch.OfInformationEngineering,WHUT11.1Basicconcepts11.1.1Gain11.1.1GainspectrumandbandwidthAmplifierpumpedopticallyorelectricallytorealizeopticalgain.Opticalgainhasthegeneralform:

isthepeakvalueofthegain

istheopticalfrequencyoftheincidentsignal

istheatomictransitionfrequency

istheopticalpowerofthesignalbeingamplified

isthesaturationpower12/15/20225TheSch.OfInformationEngineering,WHUT11.1.1GainspectrumandbandwIntheunsaturatedregimeLorentzianspectrumwithbandwidthTypically(40nmorso)12/15/20226TheSch.OfInformationEngineering,WHUTIntheunsaturatedregime12/1112/15/20227TheSch.OfInformationEngineering,WHUT12/11/20227TheSch.OfInformaUsewithinitialconditionsignalpowergrowsasAmplificationfactoralsodependsonfrequencyasAmplifierbandwidthisdefinedastheFWHMofItisrelatedtogainbandwidthasItiseasytoshowthat12/15/20228TheSch.OfInformationEngineering,WHUTUsewithinit11.1.2GainsaturationIfG=G0/212/15/20229TheSch.OfInformationEngineering,WHUT11.1.2GainsaturationIfG=G0/11.1.3AmplifiernoiseOpticalamplifiersintroducenoiseanddegradeSNR.Sourceofnoise:SpontaneousemissionNoisespectraldensityPopulationinversionfactorAmplifiernoisefigureisdefinedas12/15/202210TheSch.OfInformationEngineering,WHUT11.1.3AmplifiernoiseOptical11.1.4Amplifierapplications12/15/202211TheSch.OfInformationEngineering,WHUT11.1.4Amplifierapplications111.2SemiconductorOpticalAmplifier11.2.1Amplifierdesign11.2.2

Amplifiercharacteristics

11.2.3

ProblemsofSOAs

12/15/202212TheSch.OfInformationEngineering,WHUT11.2SemiconductorOpticalAmp11.2.1AmplifierdesignAlaserbiasedbelowthresholdactsasaFPamplifier.FeedbackatfacetsprovidesmostgainnearFPresonances.Amplificationfactorobtainedconsideringmultiplereflections:1.FPA12/15/202213TheSch.OfInformationEngineering,WHUT11.2.1AmplifierdesignAlaseristhesinglepassamplificationfactor.reducestoGwhenAmplifierbandwidthsetbysharpnessofcavityresonances.12/15/202214TheSch.OfInformationEngineering,WHUTisthesinglepassampl2.TravelingwaveamplifiersFPamplifiersnotsuitablebecauseoftheirnarrowbandwidth.Feedbackatthecleavedfacetsmustbesuppressed.Commontocoatfacetswithanantireflectioncoating.ARcoatingshouldbegoodenoughtosuppressFPresonances.12/15/202215TheSch.OfInformationEngineering,WHUT2.TravelingwaveamplifiersFP12/15/202216TheSch.OfInformationEngineering,WHUT12/11/202216TheSch.OfInform11.2.2Amplifiercharacteristics12/15/202217TheSch.OfInformationEngineering,WHUT11.2.2AmplifiercharacteristiWidegainspectrumwithnegligibleripples.Highgain(>25dB)atlowcurrents.Outputsaturationpowerintherange5-10mW.Noisefigureintherange5-7dB.12/15/202218TheSch.OfInformationEngineering,WHUTWidegainspectrumwithneglig11.2.3ProblemswithSOAs12/15/202219TheSch.OfInformationEngineering,WHUT11.2.3ProblemswithSOAs12/11SOAprovidePolarizationdependentgain:severalschemescansolvethisproblempartially.Largecouplinglosses(6-8dBormore).Relativelylargenoisefigure.12/15/202220TheSch.OfInformationEngineering,WHUTSOAprovidePolarizationdepen11.3Ramanamplifier11.3.1Ramangainandbandwidth11.3.2Ramangainsaturation11.3.2Ramanamplifierdesign12/15/202221TheSch.OfInformationEngineering,WHUT11.3Ramanamplifier11.3.1RamPumpedopticallyintheforwardorbackwarddirection.Usestimulatedramanscatteringforsignalamplification.Canworkatanywavelengthwithsuitablepumping.Fiberusedfordatatransmissioncanitselfbeused.Gaincanbemadepolarizationindependentusingorthogonallypolarizedpumpsateachwavelength.12/15/202222TheSch.OfInformationEngineering,WHUTPumpedopticallyintheforwar11.3.1Ramangainandbandwidth12/15/202223TheSch.OfInformationEngineering,WHUT11.3.1RamangainandbandwidtMaingainpeakshiftedby13.2THz(about100nm)frompumpwavelength.Ramangainspectrumextendsover>20THz.Gaincoefficientdependsonmodeareaofthepump.Candifferbyafactorof5ormoreforSMF,DSFandDCF.12/15/202224TheSch.OfInformationEngineering,WHUTMaingainpeakshiftedbyRamangainsaturation30dBgainatapumppower-1WforL-1Km.Nogainsaturationupto0.5W12/15/202225TheSch.OfInformationEngineering,WHUT11.3.2Ramangainsaturation3011.3.3Ramanamplifierdesign12/15/202226TheSch.OfInformationEngineering,WHUT11.3.3Ramanamplifierdesign1Multiplepumpscanprovidewideandflatgainspectrum.NoiseissmallerforRamanamplifier.SufferfromdoubleRayleighscatteringandpumpnoisetransfer.Backwardpumpingprovidesabetterdesign.12/15/202227TheSch.OfInformationEngineering,WHUTMultiplepumpscanprovidewid11.4Erbiumdopedopticalamplifier11.11.1pumpingcharacteristics11.11.2gainspectrum11.11.3amplifiercharacteristics11.11.4amplifiernoise11.11.4amplifierdesign12/15/202228TheSch.OfInformationEngineering,WHUT11.4ErbiumdopedopticalamplDevelopedafter1987andcommercializedduringthe1990s.Fibercoredopedwitherbium(length20-200m).Pumpedusingdiodelasersoperatingat980or1480nm.Provide20-30dBgainatpumppowersbelow50mW.Gainbandwidthupto40nmpossible.Noisefigureintherange4-5dB.Providepolarizationindependentgain.Gainpatternindependent(responsetime-10ms).CanbedesignedtoworkinboththeCandLbands.12/15/202229TheSch.OfInformationEngineering,WHUTDevelopedafter1987andcomme11.11.1pumpingcharacteristics12/15/202230TheSch.OfInformationEngineering,WHUT11.11.1pumpingcharacteristicAmorphousnatureofsilicabroadensenergylevelsintobands.Semiconductorlasersat980and1480nmusedmostcommonly.30dBgainobtainedwithonly10-15mWofabsorbedpumppower.Pumpingefficiencyupto11dB/mWpossibleat980nm.Pumpingat1480nmrequireslongerfibersandhigherpowers.12/15/202231TheSch.OfInformationEngineering,WHUTAmorphousnatureofsilicabro12/15/202232TheSch.OfInformationEngineering,WHUT12/11/202232TheSch.OfInform11.11.2Gainspectrum12/15/202233TheSch.OfInformationEngineering,WHUT11.11.2Gainspectrum12/11/202Shapeofgainspectrumaffectedbyothercodopantssuchasgermaniaandalumina.Structuraldisordersofsilicaleadtoinhomogeneousbroadening.Starksplittingleadstohomogeneousbroadening.Effectivegainspectrum:isthedistributionfunctionwhoseformalsodependsonthepresenceofotherdopantswithinthefibercore.12/15/202234TheSch.OfInformationEngineering,WHUTShapeofgainspectrumaffecteNonuniformgainover1525-1565range.Again-flatteningfilterusedinpractice.Thegainspectrumofaluminosilicateglasseshasroughlyequalcontributionsfromhomogeneousandinhomogeneousbroadeningmechanisms.ThegainbandwidthofsuchEDFAstypicallyexceeds35nm.12/15/202235TheSch.OfInformationEngineering,WHUTNonuniformgainover1525-156511.11.3Amplifiercharacteristics12/15/202236TheSch.OfInformationEngineering,WHUT11.11.3AmplifiercharacteristL=10-15menoughtoprovide20-30dBgain.Foragivenpumppower,GbecomesmaximumatanoptimumvalueofLanddropssharplywhenLexceedsthisoptimumvalue.ItisnecessarytochoosebothLandappropriately.12/15/202237TheSch.OfInformationEngineering,WHUTL=10-15menoughtoprovide20-11.11.4Amplifiernoise12/15/202238TheSch.OfInformationEngineering,WHUT11.11.4Amplifiernoise12/11/2butForathree-levelpumpingscheme,andBothandvaryalongfiberlength,andshouldbeaveragedoverlength.NoisefiguredependsbothonlengthLandpumppower.12/15/202239TheSch.OfInformationEngineering,WHUTbut12/11/20223911.11.5AmplifierdesignC-BandEDFAs12/15/202240TheSch.OfInformationEngineering,WHUT11.11.5AmplifierdesignC-BandL-BandEDFAs12/15/202241TheSch.OfInformationEngineering,WHUTL-BandEDFAs12/11/202241TheSc11.5SystemapplicationofOA12/15/202242TheSch.OfInformationEngineering,WHUT11.5SystemapplicationofOA1Chapter11OpticalAmplifier12/15/202243TheSch.OfInformationEngineering,WHUTChapter11OpticalAmplifier1Usedroutinelyforlosscompensationsince1995AmplifytheinputsignalbutalsoaddsomenoiseSeveralkindsofamplifiershavebeendeveloped

semiconductoropticalamplifier

raman-basedfiberamplifiererbium-dopedfiberamplifierEDFAsareusedmostcommonlyforlightwavesystemRamanamplifiersworkbetterforlong-haulsystem12/15/202244TheSch.OfInformationEngineering,WHUT12/11/20222TheSch.OfInformaOUTLINEBasicconceptsSemiconductoropticalamplifier(SOA)RamanamplifierErbiumdopedfiberamplifierSystemapplicationofopticalamplifier12/15/202245TheSch.OfInformationEngineering,WHUTOUTLINEBasicconcepts12/11/20211.1Basicconcepts11.1.1Gainspectrumandbandwidth11.1.2

Gainsaturation

11.1.3Amplifiernoise11.1.4Amplifierapplications12/15/202246TheSch.OfInformationEngineering,WHUT11.1Basicconcepts11.1.1Gain11.1.1GainspectrumandbandwidthAmplifierpumpedopticallyorelectricallytorealizeopticalgain.Opticalgainhasthegeneralform:

isthepeakvalueofthegain

istheopticalfrequencyoftheincidentsignal

istheatomictransitionfrequency

istheopticalpowerofthesignalbeingamplified

isthesaturationpower12/15/202247TheSch.OfInformationEngineering,WHUT11.1.1GainspectrumandbandwIntheunsaturatedregimeLorentzianspectrumwithbandwidthTypically(40nmorso)12/15/202248TheSch.OfInformationEngineering,WHUTIntheunsaturatedregime12/1112/15/202249TheSch.OfInformationEngineering,WHUT12/11/20227TheSch.OfInformaUsewithinitialconditionsignalpowergrowsasAmplificationfactoralsodependsonfrequencyasAmplifierbandwidthisdefinedastheFWHMofItisrelatedtogainbandwidthasItiseasytoshowthat12/15/202250TheSch.OfInformationEngineering,WHUTUsewithinit11.1.2GainsaturationIfG=G0/212/15/202251TheSch.OfInformationEngineering,WHUT11.1.2GainsaturationIfG=G0/11.1.3AmplifiernoiseOpticalamplifiersintroducenoiseanddegradeSNR.Sourceofnoise:SpontaneousemissionNoisespectraldensityPopulationinversionfactorAmplifiernoisefigureisdefinedas12/15/202252TheSch.OfInformationEngineering,WHUT11.1.3AmplifiernoiseOptical11.1.4Amplifierapplications12/15/202253TheSch.OfInformationEngineering,WHUT11.1.4Amplifierapplications111.2SemiconductorOpticalAmplifier11.2.1Amplifierdesign11.2.2

Amplifiercharacteristics

11.2.3

ProblemsofSOAs

12/15/202254TheSch.OfInformationEngineering,WHUT11.2SemiconductorOpticalAmp11.2.1AmplifierdesignAlaserbiasedbelowthresholdactsasaFPamplifier.FeedbackatfacetsprovidesmostgainnearFPresonances.Amplificationfactorobtainedconsideringmultiplereflections:1.FPA12/15/202255TheSch.OfInformationEngineering,WHUT11.2.1AmplifierdesignAlaseristhesinglepassamplificationfactor.reducestoGwhenAmplifierbandwidthsetbysharpnessofcavityresonances.12/15/202256TheSch.OfInformationEngineering,WHUTisthesinglepassampl2.TravelingwaveamplifiersFPamplifiersnotsuitablebecauseoftheirnarrowbandwidth.Feedbackatthecleavedfacetsmustbesuppressed.Commontocoatfacetswithanantireflectioncoating.ARcoatingshouldbegoodenoughtosuppressFPresonances.12/15/202257TheSch.OfInformationEngineering,WHUT2.TravelingwaveamplifiersFP12/15/202258TheSch.OfInformationEngineering,WHUT12/11/202216TheSch.OfInform11.2.2Amplifiercharacteristics12/15/202259TheSch.OfInformationEngineering,WHUT11.2.2AmplifiercharacteristiWidegainspectrumwithnegligibleripples.Highgain(>25dB)atlowcurrents.Outputsaturationpowerintherange5-10mW.Noisefigureintherange5-7dB.12/15/202260TheSch.OfInformationEngineering,WHUTWidegainspectrumwithneglig11.2.3ProblemswithSOAs12/15/202261TheSch.OfInformationEngineering,WHUT11.2.3ProblemswithSOAs12/11SOAprovidePolarizationdependentgain:severalschemescansolvethisproblempartially.Largecouplinglosses(6-8dBormore).Relativelylargenoisefigure.12/15/202262TheSch.OfInformationEngineering,WHUTSOAprovidePolarizationdepen11.3Ramanamplifier11.3.1Ramangainandbandwidth11.3.2Ramangainsaturation11.3.2Ramanamplifierdesign12/15/202263TheSch.OfInformationEngineering,WHUT11.3Ramanamplifier11.3.1RamPumpedopticallyintheforwardorbackwarddirection.Usestimulatedramanscatteringforsignalamplification.Canworkatanywavelengthwithsuitablepumping.Fiberusedfordatatransmissioncanitselfbeused.Gaincanbemadepolarizationindependentusingorthogonallypolarizedpumpsateachwavelength.12/15/202264TheSch.OfInformationEngineering,WHUTPumpedopticallyintheforwar11.3.1Ramangainandbandwidth12/15/202265TheSch.OfInformationEngineering,WHUT11.3.1RamangainandbandwidtMaingainpeakshiftedby13.2THz(about100nm)frompumpwavelength.Ramangainspectrumextendsover>20THz.Gaincoefficientdependsonmodeareaofthepump.Candifferbyafactorof5ormoreforSMF,DSFandDCF.12/15/202266TheSch.OfInformationEngineering,WHUTMaingainpeakshiftedbyRamangainsaturation30dBgainatapumppower-1WforL-1Km.Nogainsaturationupto0.5W12/15/202267TheSch.OfInformationEngineering,WHUT11.3.2Ramangainsaturation3011.3.3Ramanamplifierdesign12/15/202268TheSch.OfInformationEngineering,WHUT11.3.3Ramanamplifierdesign1Multiplepumpscanprovidewideandflatgainspectrum.NoiseissmallerforRamanamplifier.SufferfromdoubleRayleighscatteringandpumpnoisetransfer.Backwardpumpingprovidesabetterdesign.12/15/202269TheSch.OfInformationEngineering,WHUTMultiplepumpscanprovidewid11.4Erbiumdopedopticalamplifier11.11.1pumpingcharacteristics11.11.2gainspectrum11.11.3amplifiercharacteristics11.11.4amplifiernoise11.11.4amplifierdesign12/15/202270TheSch.OfInformationEngineering,WHUT11.4ErbiumdopedopticalamplDevelopedafter1987andcommercializedduringthe1990s.Fibercoredopedwitherbium(length20-200m).Pumpedusingdiodelasersoperatingat980or1480nm.Provide20-30dBgainatpumppowersbelow50mW.Gainbandwidthupto40nmpossible.Noisefigureintherange4-5dB.Providepolarizationindependentgain.Gainpatternindependent(responsetime-10ms).CanbedesignedtoworkinboththeCandLbands.12/15/202271TheSch.OfInformationEngineering,WHUTDevelopedafter1987andcomme11.11.1pumpingcharacteristics12/15/202272TheSch.OfInformationEngineering,WHUT11.11.1pumpingcharacteristicAmorphousnatureofsilicabroadensenergylevelsintobands.Semiconductorlasersat980and1480nmusedmostcommonly.30dBgainobtainedwithonly10-15mWofabsorbedpumppower.Pumpingefficiencyupto11dB/mWpossibleat980nm.Pumpingat1480nmrequireslongerfibersandhigherpowers.12/15/202273TheSch.OfInformationEngineering,WHUTAmorphousnatureofsilicabro12/15/202274TheSch.OfInformationEngineering,WHUT12/11/202232TheSch.OfInform11.11.2Gainspectrum12/15/202275TheSch.OfInformationEngineering,WHUT11.11.2Gainspectrum12/11/202Shapeofgainspectrumaffectedbyothercodopantss

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