第三章光有源器件

光調(diào)制器（Modulator

）光的調(diào)制：光子（或光波）載體載入信息的物理過(guò)程。光調(diào)制器:實(shí)現(xiàn)從電信號(hào)到光信號(hào)的轉(zhuǎn)換光調(diào)制的分類(lèi)：從光源調(diào)制角度分：內(nèi)調(diào)制或直接調(diào)制：將調(diào)制信號(hào)直接注入激光器（調(diào)制激光器驅(qū)動(dòng)電流），實(shí)現(xiàn)激光輸出光強(qiáng)度等參數(shù)的調(diào)制--（簡(jiǎn)單、經(jīng)濟(jì)、引入較大的啁啾）；外調(diào)制：將調(diào)制信號(hào)控制激光器后接的外調(diào)制器，利用調(diào)制器的電光、聲光等物理效應(yīng)使其輸出光的強(qiáng)度等參數(shù)隨信號(hào)而變--（調(diào)制信號(hào)啁啾小）。從被調(diào)制光波的參數(shù)分：強(qiáng)度調(diào)制、相位調(diào)制、偏振調(diào)制直接調(diào)制和外調(diào)制Laser

DirectModulationofLaserDiodeBias+DATAIssues--ComplexDynamicsYield

ExternalModulationofLaserDiodeLaserModulatorBiasBias+DATAIssues--AdditionalComponent光源的外調(diào)制技術(shù)調(diào)制信號(hào)不直接施加在LD上，而是施加在光調(diào)制器上。外調(diào)制技術(shù)分類(lèi)：電光調(diào)制

ElectroopticEffects電致吸收

Electro-AbsorptionEffects磁光調(diào)制MagnetoopticEffects聲光調(diào)制AcousticModulators其中電光調(diào)制和電致吸收最為常用。電光效應(yīng)光調(diào)制器電光效應(yīng)：電壓施加于某些電光晶體(如LiNbO3)

，導(dǎo)致晶體折射率發(fā)生變化，引起通過(guò)該晶體的光波特性發(fā)生變化。折射率變化n與外加電場(chǎng)E有著復(fù)雜的關(guān)系，可近似地認(rèn)為n與(rE+RE2)成正比。電光調(diào)制器主要利用普科爾(Pocket)效應(yīng).普科爾(Pocket)效應(yīng)：晶體折射率與外加電場(chǎng)幅度成線性變化克爾(Kerr)效應(yīng)：晶體折射率與外加電場(chǎng)幅度的平方成比例變化線性電光效應(yīng)應(yīng)用1:相位調(diào)制器Ex和Ey的相位差為：當(dāng)線偏振光沿z軸傳輸距離L后，變化，于是變化。施加的外電壓在兩個(gè)電場(chǎng)分量間產(chǎn)生一個(gè)可調(diào)整的相位差，因此出射光波的偏振態(tài)可被施加的外電壓控制?？梢苑謩e控制晶體厚度d和長(zhǎng)度L。線性電光效應(yīng)應(yīng)用1:相位調(diào)制器§1調(diào)制器－鈮酸鋰調(diào)制器線性電光效應(yīng)應(yīng)用2:強(qiáng)度調(diào)制器§1調(diào)制器－鈮酸鋰調(diào)制器鈮酸鋰強(qiáng)度調(diào)制器的原理鈮酸鋰調(diào)制器的主要指標(biāo)消光比插入損耗外加電壓偏振相關(guān)性晶體折射率隨外加電場(chǎng)而變化。具有非常好的消啁啾特性，適合于高速系統(tǒng)的超長(zhǎng)距離傳輸。但調(diào)制器的插入損耗大，需要較高的驅(qū)動(dòng)電壓(典型值為4V)，難以與光源集成，而且對(duì)偏振敏感?！?調(diào)制器－鈮酸鋰調(diào)制器鈮酸鋰調(diào)制器實(shí)物圖電致吸收光調(diào)制器§1調(diào)制器－EA是一種損耗器件，利用Franz-Keldysh效應(yīng)和量子限制Stark效應(yīng)，工作在調(diào)制器材料吸收邊界波長(zhǎng)處。半導(dǎo)體材料發(fā)生本征吸收的波長(zhǎng)：陡峭介質(zhì)邊吸收帶電致吸收光調(diào)制器Franz-Keldysh效應(yīng)：1958年提出，是指在電場(chǎng)作用下半導(dǎo)體材料的吸收邊紅移的理論。原理：改變調(diào)制器上的偏壓，使多量子阱(MQW)的吸收邊界波長(zhǎng)發(fā)生變化，進(jìn)而改變光束的通斷，實(shí)現(xiàn)調(diào)制。當(dāng)調(diào)制器無(wú)偏壓時(shí)，光束處于通狀態(tài)，輸出功率最大；隨著調(diào)制器上偏壓的增加，MQW的吸收邊移向長(zhǎng)波長(zhǎng)，原光束波長(zhǎng)處吸收系數(shù)增大，調(diào)制器為斷狀態(tài)，輸出功率最小。電吸收調(diào)制器與LD集成使用材料：III-V族半導(dǎo)體材料特點(diǎn)：易與激光器集成、體積小、驅(qū)動(dòng)電壓低（~2V）、啁啾大于LN調(diào)制器、消光比低于LN調(diào)制器（~10dB）聲光效應(yīng)光調(diào)制器聲光效應(yīng)是指聲波作用于某晶體時(shí)，產(chǎn)生光彈性作用，使折射率發(fā)生變化，從而達(dá)到光調(diào)制的目的。特點(diǎn)：消光比高（～30dB）、驅(qū)動(dòng)功率較低、調(diào)制速率低、帶寬窄§1調(diào)制器－聲光當(dāng)外加信號(hào)通過(guò)驅(qū)動(dòng)電源作用到聲光器件時(shí)，超聲強(qiáng)度隨此信號(hào)變化，衍射光強(qiáng)也隨之變化，從而實(shí)現(xiàn)了對(duì)激光的振幅或強(qiáng)度調(diào)制。磁光效應(yīng)又稱(chēng)為法拉第效應(yīng)。當(dāng)光通過(guò)介質(zhì)傳播時(shí)，若在垂直光的傳播方向上加一強(qiáng)磁場(chǎng)，則光的偏振面產(chǎn)生偏轉(zhuǎn)，其旋轉(zhuǎn)角度與介質(zhì)長(zhǎng)度、外加磁場(chǎng)強(qiáng)度成正比。調(diào)制原理：經(jīng)起偏器的光信號(hào)通過(guò)磁光晶體，其偏轉(zhuǎn)角與調(diào)制電流有關(guān)。由于起偏器與檢偏器的透光軸相互平行，當(dāng)調(diào)制電流為零時(shí)，透過(guò)檢偏器的光強(qiáng)最大；隨著電流逐漸增大，旋轉(zhuǎn)角加大，透過(guò)檢偏器的光強(qiáng)逐漸下降。磁光效應(yīng)光調(diào)制器§1調(diào)制器－磁光OEORegenerator1R,2Rand3RRegeneration什么是光放大受激吸收受激輻射自發(fā)輻射§2光放大器RegeneratorsvsO-AmplifiersRegeneratorsspecifictobitrateandmodulationformatused;O-Ampsareinsensitive(I.e.transparent)Asystemwithopticalamplifierscanbemore

easily

upgradedtohigherbitratewithoutreplacingtheamplifiersOpticalamplifiershavelargegainbandwidthsIssues:AmplifiersintroduceadditionalnoisethataccumulatesSpectralshapeofgain(flatness),outputpower,transientbehaviorneedtobecarefullydesigned§2光放大器－應(yīng)用§2光放大器－應(yīng)用

IdealopticalamplifierHighpowergainBroadbandFlatgain-wavelengthresponsibilityLow

noiseHighSNRHighsaturationpowerOpticalAmplifierTypesSemiconductoropticalamplifier(SOA)FiberAmplifiersErbiumdopedfiberamplifier(EDFA)Praseodymiumdopedfiberamplifier(PDFA)Thuliumdopedfiberamplifier

(TDFA)StiumlatedRamanfiberamplifer

（SRFA）

TheintroductionofSOATheimprovementofsemiconductorlaserleadtoFP(Fabry-Perot)

semiconductoramplifier,andalsotothestudyoftravelingwavesemiconductoramplifier.SOAismadeof 3-5groupcompoundsemiconductor,suchasGaAs,GaP,InPCentralwavelength:~800nm,~1300nm,~1550nmFrequencybandlargerthan40nmGainishigherthan30dBTheadvantagesofSOASmallsize,andeasytobeintegratedwithsemiconductorcircuits.Fabricationissimpleandwithlowpowerconsumption,longlife-spanandlowcost.Gainresponseisveryquickandwellsuitedforswitchingandsignalprocessinginopticalnetworksapplication.Canamplifyopticalsignalandprocesssignalinthesametimesuchasswitch,socanbeusedinwavelengthconvertingandopticalswitch.ThedisadvantagesofSOAThecouplinglosswithopticalfiberistoolarge

SensitivetopolarizationNoisefigureishigh(~8dB)CrosstalkEasytobeaffectedbytemperature,lowstability

TheclassificationofSOATherearetwokindsofSOA：(1)Fabry-PerotAmplifier,FPA

usetheFPcavityastheopticalamplifier.(2)Travelling-WaveAmplifier,TWA

tocoatthetwoendoftheFabry-Perotwithanti-reflectionpellicle,soacquirebroadbandandhighpoweroutputandlownoiseopticalamplification.TheclassificationofSOAOutputamplifiedlightMirrorinjectedcurrentIncidencelightMirrorFabry-PerotAmplifierTheclassificationofSOAanti-reflectionpellicle

ARinjectedcurrentIncidencelightOutputamplifiedlightTraveling-WaveAmplifier,TWAanti-reflectionpellicle

ARFPA與TWA的帶寬比較不同反射率時(shí)FP－SOA的增益譜SOA的集成優(yōu)勢(shì)全光型波長(zhǎng)轉(zhuǎn)換器指不經(jīng)過(guò)電域處理，直接把信息從一個(gè)光波長(zhǎng)轉(zhuǎn)換到另一個(gè)光波長(zhǎng)。在光域中直接實(shí)現(xiàn)波長(zhǎng)轉(zhuǎn)換可以克服光-電-光波長(zhǎng)轉(zhuǎn)換器中電器件的速度瓶頸、透明性低等不足。SOA用于全光波長(zhǎng)變換全光波長(zhǎng)變換器基于光調(diào)制原理基于光混頻原理交叉增益調(diào)制（XGM）交叉相位調(diào)制（XPM）——四波混頻（FWM）XGM：利用信號(hào)光攜帶的信息調(diào)制有源介質(zhì)的增益，從而調(diào)制在同一介質(zhì)中傳播的探測(cè)光(通常是連續(xù)光)的放大倍數(shù)，使其強(qiáng)度產(chǎn)生調(diào)制，實(shí)現(xiàn)信息從信號(hào)光到探測(cè)光的轉(zhuǎn)換。它實(shí)際上可以看作是特殊的光控光開(kāi)關(guān)。基于XGM的SOA全光波長(zhǎng)變換原理：當(dāng)信號(hào)脈沖處于上升沿時(shí),載流子密度迅速增大,放大器的增益很快飽和,因此轉(zhuǎn)化到連續(xù)探測(cè)波上的信號(hào)為0。當(dāng)信號(hào)脈沖處于下降沿時(shí),載流子密度迅速減小,放大器的增益恢復(fù),因此轉(zhuǎn)化到連續(xù)探測(cè)波上的信號(hào)為1。這樣信號(hào)光上的光脈沖被反轉(zhuǎn)轉(zhuǎn)化到波長(zhǎng)上?；赬GM的SOA全光波長(zhǎng)變換優(yōu)點(diǎn)：結(jié)構(gòu)簡(jiǎn)單轉(zhuǎn)換效率高波長(zhǎng)轉(zhuǎn)換范圍寬對(duì)偏振不敏感缺點(diǎn)：輸入輸出信號(hào)反相輸出消光比退化比特率透明有限噪聲指數(shù)高啁啾大基于XPM的SOA全光波長(zhǎng)變換XPM：當(dāng)信號(hào)光和探測(cè)光共同傳播時(shí)，信號(hào)光強(qiáng)度信號(hào)能夠調(diào)制非線性介質(zhì)的有效折射率，從而改變探測(cè)光的傳播相位。如果利用干涉儀將探測(cè)光分成兩路，并利用信號(hào)光改變兩路光之間的相差，在輸出端發(fā)生相長(zhǎng)或相消干涉，就可使得信號(hào)光的信息同相或反相地轉(zhuǎn)換到了探測(cè)光上。常用的干涉儀有馬赫一曾德干涉儀（MZI）、邁克爾遜干涉儀（MI）等。優(yōu)點(diǎn)：輸入信號(hào)功率小頻率啁啾小或負(fù)啁啾消光比大大提高缺點(diǎn)：輸入功率的動(dòng)態(tài)范圍比較窄，所以必須對(duì)輸入信號(hào)的功率進(jìn)行嚴(yán)格控制?；赬PM的SOA全光波長(zhǎng)變換基于FWM的SOA全光波長(zhǎng)變換FWM：一個(gè)或幾個(gè)光波的光子被湮滅，同時(shí)產(chǎn)生了幾個(gè)不同頻率的新光子，且在此參量過(guò)程中，凈能量和動(dòng)量是守恒的。由于FWM能夠頗為有效地產(chǎn)生新的光波，可被利用實(shí)現(xiàn)完全透明的全光波長(zhǎng)變換。——信號(hào)頻率——泵浦頻率優(yōu)點(diǎn)：調(diào)制格式透明，任何信息（幅度，相位和頻率）都能保留下來(lái)能同時(shí)轉(zhuǎn)換多個(gè)波長(zhǎng)作用距離短，對(duì)相位匹配不敏感轉(zhuǎn)換后信號(hào)光譜反轉(zhuǎn)，因此可以用于色散補(bǔ)償缺點(diǎn)：轉(zhuǎn)換效率低，轉(zhuǎn)換后信噪比惡化上轉(zhuǎn)換效率比下轉(zhuǎn)換低轉(zhuǎn)換范圍小偏振相關(guān)基于FWM的SOA全光波長(zhǎng)變換OpticalAmplifierVarieties

IntroductionofOFAUsedopedfiberasamplifyingmedium,

suchasEDFerbiumdopedfiber;PDFpraseodymiumdopedfiber;TDFthuliumdopedfiber.In1985,

thefirstEDFwasdevelopedbytheUniversityofSouthampton,UKIn1987,theEDFAwhichcandirectlyamplifying1.5mopticalsignalwasdevelopedbyBellLabs

&

UniversityofSouthamptonatthesametime.In1994,theEDFAisavailable,nowisamaturetechnologyandisakeycomponentinopticalsystem,

espinDWDMEDFAsuccessfactorsAvailabilityofcompactandreliablehigh-powersemiconductorpumplasersEDFAisanall-fiberdevice=>polarization-independent&easytocouplelightin/outSimplicityofdeviceNocrosstalkintroducedwhileamplifying!EDF:ErbiumionisdopedinthecenterofthecoreHighlydopedarea100~2000ppmerbium3~6um

Core

125umSilicacladding250umcoatingRadialdistanceOpticalmodeTheareawheretheenergiesofthepumplaserandinputsignalexchangeThecomponentsofEDFA摻鉺光纖中的鉺離子能級(jí)示意圖ExperimentallymeasuredabsorptionspectrumofanEr3+-dopedgermano-alumino-silicafiber.摻鉺光纖放大器的基本結(jié)構(gòu)示意圖同向泵浦結(jié)構(gòu)ThepumplaserofEDFAPumplasersource980nm1480nmpumpmodel3energylevel2energylevelExchangeefficiency

lowhighnoiselowhighcosthighlowTheretwokindsofpumplaserforEDFA:980nm&1480nm

Compareof980nm&1480nmpumplasersourceThecomponentsofEDFAThecomponentsofEDFAOpticalisolatorOnewaypassforopticalsignal.Shouldbelowinsertinglossandhighseparation.TheinputportisolatorpreventsbackwardtransmissionofopticalsignalandASEthatwoulddecreasethestabilityofinputportlaser.TheoutputportisolatorpreventsbackwardlightenterEDFotherwiseitwillgreatlyreducethedegreeofpopulationinverse,lowerthegainandincreasenoisefigure,whatismoreresultunexpectedlaserresonance.OpticalmultiplexerTocoupleopticalsignalandpumplaserintoEDF.ShouldbelowinsertinglossandhighbandwidthsoastopromotetheamplifyingbandwidthofEDFA摻鉺光纖放大器的基本結(jié)構(gòu)示意圖反向泵浦結(jié)構(gòu)§2光放大器－EDFA摻鉺光纖放大器的基本結(jié)構(gòu)示意圖雙向泵浦結(jié)構(gòu)§2光放大器－EDFAThecharacteristicsofC-bandEDFATherelationofgainandinputofEDFAsaturationGainThecharacteristicsofEDFAGain增益頻譜增益帶寬（FWHM）大于10nm纖芯中摻入鋁離子，帶寬還可增大且增益頻譜相當(dāng)平坦。小信號(hào)增益EDFA的增益與鉺離子濃度、芯徑、摻雜光纖長(zhǎng)度和泵浦功率有關(guān)。對(duì)于給定的放大器長(zhǎng)度（EDF長(zhǎng)度），增益隨泵浦功率在開(kāi)始時(shí)按指數(shù)增加，當(dāng)泵浦功率超過(guò)一定值時(shí)，增益增加變緩，并趨于一恒定值。小信號(hào)增益當(dāng)泵浦功率一定時(shí)，放大器在某一最佳長(zhǎng)度時(shí)獲得最大增益，如果放大器長(zhǎng)度超過(guò)此值，由于泵浦的消耗，最佳點(diǎn)后的摻鉺光纖不能受到足夠泵浦，而且要吸收已放大的信號(hào)能量，導(dǎo)致增益很快下降。增益飽和（或壓縮）特性

在EDFA泵浦功率一定的情況下，輸入信號(hào)功率較小時(shí)，放大器的增益不隨入射信號(hào)的增加而變化。當(dāng)輸入信號(hào)增大到一定值后，增益開(kāi)始隨信號(hào)功率的增加而下降，這是入射信號(hào)導(dǎo)致EDFA出現(xiàn)增益飽和的緣故。ThecharacteristicsofEDFAinputamplifiedamplifiedNoiseFigure,NFThecharacteristicsofEDFAamplifiedoriginalSourceSpontaneousEmission,SSEASE+(GainxSSE)NoiseFigureGainInputsignalandamplifiedsignalThecharacteristicsofEDFA0.6nm:resolutionofspectralanalyzer:Plank’constant:lightspeed:gainofamplifier:powerofASE摻鉺光纖放大器級(jí)聯(lián)后的增益響應(yīng)§2光放大器－EDFA動(dòng)態(tài)增益均衡光纖放大器的技術(shù)要求動(dòng)態(tài)增益均衡放大器的概念包括：

（1）增益譜平坦：

在一定帶寬范圍內(nèi)的多路信號(hào)同時(shí)放大時(shí)，各

信道增益相同；（2）增益鎖定（自動(dòng)增益控制）：

信道增、減或某信道功率改變時(shí)，對(duì)本信道或

其它信道增益沒(méi)有影響。要求同時(shí)實(shí)現(xiàn)平坦鎖定§2光放大器－EDFA增益譜的平坦化方法工作在77oK.引入另外一種摻雜，如鉺鐿共摻.EDF長(zhǎng)度、泵浦功率的優(yōu)化制作特種結(jié)構(gòu)的光纖波導(dǎo)結(jié)構(gòu)，如雙芯光纖光纖光柵濾波§2光放大器－EDFA利用長(zhǎng)周期光柵平坦摻鉺光纖放大器的增益譜§2光放大器－EDFA§2光放大器－EDFAEDFA實(shí)物圖光纖拉曼放大器FRA光纖中的非線性效應(yīng)SRS受激拉曼散射實(shí)現(xiàn)光信號(hào)的放大增益介質(zhì)：系統(tǒng)傳輸光纖FRA光纖(a)無(wú)泵激光的1550nm傳輸光功率(dB)波長(zhǎng)1550nm波長(zhǎng)光功率(dB)1550nm1450nm光纖(b)有泵激光的1550nm傳輸1550nm經(jīng)光纖傳輸衰減1450nm1550nm如果一個(gè)弱信號(hào)和一個(gè)強(qiáng)泵浦光同時(shí)在光纖中傳輸，并使弱信號(hào)波長(zhǎng)置于泵浦光的拉曼增益帶寬內(nèi)，則弱信號(hào)即可被放大。這種基于SRS機(jī)制的光放大器稱(chēng)為光纖拉曼放大器FRA。硅光纖拉曼增益系數(shù)頻譜曲線增益帶寬（FWHM）可以達(dá)到約8THz泵浦功率為200mW時(shí)，最大增益值為7.78dB泵浦功率為100mW時(shí)，最大增益值為3.6dB。在增益峰值附近的增益帶寬約為7~8THz。小信號(hào)光在長(zhǎng)光纖內(nèi)的拉曼增益FRA放大增益和泵浦功率的關(guān)系增益飽和FRA的優(yōu)缺點(diǎn)優(yōu)點(diǎn)1.增益波長(zhǎng)由泵浦光波長(zhǎng)決定。2.增益介質(zhì)可以為傳輸光纖本身。3.噪聲系數(shù)低。FRA的NF小于4.5dB，好于SOA（約8dB）和EDFA（約6dB）。缺點(diǎn)

需要特大功率的泵浦激光器幾種光放大器的比較放大器類(lèi)型原理激勵(lì)方式工作長(zhǎng)度噪聲特性與光纖耦合與光偏振關(guān)系穩(wěn)定性摻稀土光纖放大器粒子數(shù)反轉(zhuǎn)光數(shù)米到數(shù)十米好容易無(wú)好半導(dǎo)體光放大器粒子數(shù)反轉(zhuǎn)電100m~1mm差很難大差光纖拉曼放大器光學(xué)非線性(拉曼)效應(yīng)光數(shù)千米好容易大好EDFA和FRA的混合放大應(yīng)用光功率在分布式拉曼放大傳輸光纖中的分布Contents(??)Ⅰ.WhatistheFIBERLaser?LASER(LightAmplificationbyStimulatedEmissionofRadiation)?What’stheLASER?PUMPSOURCEREARMIRRORFRONTMIRRORROD(MEDIUM)StimulatedEmissionLaserOutputSpontaneousEmissionContents(??)?RequisitesforLASER1)MEDIUM2)CAVITY3)PUMPSOURCENd:YAG,Nd:YVO4,Nd:YLP,FIBERMirror,FiberBraggGratings,coupler

FlashLamp,LaserDiodeYAGRODLAMPMOUNTTRIGGERWIREXENONLAMPEx)Nd:YAG,XENONLAMPPUMPTYPELASERYAGCrystalContents(??)?DPSSLaserNd:YAGCrystalStimulatedEmissionXenonLampPumpPowerSupplyConnectionPartialReflector(Mirror)TotalReflector(Mirror)PumpingDirectionLaserOutputDPSS(DiodePumpedSolidState)Contents(??)?FIBERLASERCladding-PumpedACTIVEFIBERFBG(FiberBraggGratings)MultimodeCouplerSplicetoMultimodeDiodePumpPumpCombinerLDLDLDLDLDLDLDLDCollimatedLaserOutputOpticalPowerMeterLensContents(??)?AdvantagesofFIBERLaser,MaintenanceEfficiency-NoConsumableParts-MaintenanceFree-AirCoolingType(NoDIWaterCoolingSystem,去離子水冷卻系統(tǒng))Contents(??)?AdvantagesofFIBERLaser,SpaceEfficiency-SmallerSizeCO2LaserNd:YAGLaserDPSSFIBER1,372x495x331286x215x95LaserOuterDimension(mm)HANMIFIBERLaserFIBERLaseris40timessmallerthanexistingCO2&DPSSLaserwithexceptionofLaserControllerContents(??)Ⅲ.AdvantagesofFIBERLaser?AdvantagesofFIBERLaser,DurabilityElapsedTime(hr)OutputPower(mW)LaserDiodeTestbyIPGPhotonicsLifeTime:Over100kHrs-LaserDiodeswithLongerLife-Time10timeslongerthanusualDPSSLaserContents(??)?AdvantagesofFIBERLaser,Performance-ExcellentLaserBeamQualityBestLaserBeamQualityinSemiconductorPackageMarking(M2=3)-BestSolutionforHighPerformance?AdvantagesofFIBERLaser,Economical&CostSaving-LowerPowerConsumption-NoUsingDIWaterCoolingSystem-LowerLaserUnitPrice-NoConsumable&FreeMaintenanceforLaserFiberLasersFiberlasersoccurinagreatvarietyofforms,servingverydifferentapplications,e.g.:LasersgeneratingoutputsatspecialwavelengthsLasersforveryhighoutputpower(manywattsorevenkilowatts)withgoodbeamqualityQ-switchedandmode-lockedlasersforshortorultrashortpulsesFibertechnologycreatesahugeamountofattractivetechnicaloptions,butalsocomeswithabunchoftechnicaldifficulties.Inanopticalresonator,lightisconfinedandstoredatcertainresonancefrequencies

Lightcirculatesoris

repeatedly

reflected

withinthecavity

Wavelength

selectivity

isduetoopticalfeedbackFabry-PerotcavityMirrorOpticalfibreringcavityFiberCouplerIsolator腔體線形腔環(huán)形腔“8”字形腔pumpOpticalfiberFPcavityOutput1Output2ActiveFiberpumpIsolatorOpticalfiberringcavityFiberoutputActiveFiberpumpoutputFigure8cavityfiberlaserActiveFiber50:50Alotofstructureshavebeenused分布布拉格反射光纖激光器：使用兩個(gè)較高反射率的光纖光柵作為反射鏡置于摻雜光纖的兩端，構(gòu)成線形諧