第三章光有源器件

1、光調(diào)制器（光調(diào)制器（ ） 光的調(diào)制光的調(diào)制：光子（或光波）載體載入信息的物理過程。光子（或光波）載體載入信息的物理過程。 光調(diào)制器光調(diào)制器: :實(shí)現(xiàn)從電信號(hào)到光信號(hào)的轉(zhuǎn)換實(shí)現(xiàn)從電信號(hào)到光信號(hào)的轉(zhuǎn)換 光調(diào)制的分類光調(diào)制的分類： 從光源調(diào)制角度從光源調(diào)制角度分分：內(nèi)調(diào)制或直接調(diào)制內(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）；（簡(jiǎn)單、經(jīng)濟(jì)、引入較大的啁啾）；外調(diào)制外調(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)將調(diào)制信號(hào)控制激光器后接的外

2、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)而變信號(hào)而變-（調(diào)制信號(hào)啁啾?。＃ㄕ{(diào)制信號(hào)啁啾?。?從從被調(diào)制光波的參數(shù)分被調(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：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)制直接調(diào)制和外調(diào)制光源的外調(diào)制技術(shù)光源的外調(diào)制技術(shù) 調(diào)制信號(hào)不直接施加在調(diào)制信號(hào)不直接施加在LD上，而是施加在光調(diào)上，而是施加在光調(diào)制器上。制器上。 外調(diào)制技術(shù)分類：外調(diào)制技術(shù)分類： 電光調(diào)制電光調(diào)制 Electrooptic Effects 電致吸收電致吸收 Electro-Absorption Effect

3、s 磁光調(diào)制磁光調(diào)制 Magnetooptic Effects 聲光調(diào)制聲光調(diào)制 Acoustic Modulators 其中其中電光調(diào)制和電致吸收電光調(diào)制和電致吸收最為常用。最為常用。電光效應(yīng)光調(diào)制器電光效應(yīng)光調(diào)制器 電光效應(yīng)：電光效應(yīng)：電壓施加于某些電光晶體電壓施加于某些電光晶體(如如LiNbO3 ) ，導(dǎo)致晶體折射率發(fā)生變化，引起通過該晶體的光波導(dǎo)致晶體折射率發(fā)生變化，引起通過該晶體的光波特性發(fā)生變化。特性發(fā)生變化。 折射率變化折射率變化 n與外加電場(chǎng)與外加電場(chǎng)E有著復(fù)雜的關(guān)系，可近似有著復(fù)雜的關(guān)系，可近似地認(rèn)為地認(rèn)為 n與與(r E +R E 2)成正比。成正比。線性電光效應(yīng)應(yīng)用線性電

4、光效應(yīng)應(yīng)用1:相位調(diào)制器相位調(diào)制器ExEx和和EyEy的相位差為：的相位差為：450線偏振入射光圓偏振出射光VzdLxEyExEyEaEzxy晶體xy當(dāng)線偏振光沿當(dāng)線偏振光沿z z軸傳輸距離軸傳輸距離L L后，后， 變化，于是變化，于是 變化。變化。y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，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。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控制晶體厚度可以分別控制晶體厚度 d d 和長(zhǎng)度和長(zhǎng)度 L L。線性電光效應(yīng)應(yīng)用線性電光效應(yīng)應(yīng)用1:相位調(diào)制器相位調(diào)制器LiNbO3 tVL波導(dǎo)共平面條

5、形電極偏振光輸入xyz調(diào)制信號(hào)3LiNbO-TiaEdLiNbO3緩沖層波導(dǎo) tV調(diào)制信號(hào)yx電極3LiNbO-Ti1 調(diào)制器鈮酸鋰調(diào)制器調(diào)制器鈮酸鋰調(diào)制器線性電光效應(yīng)應(yīng)用線性電光效應(yīng)應(yīng)用2:強(qiáng)度調(diào)制器強(qiáng)度調(diào)制器1 調(diào)制器鈮酸鋰調(diào)制器調(diào)制器鈮酸鋰調(diào)制器鈮酸鋰強(qiáng)度調(diào)制器的原理鈮酸鋰強(qiáng)度調(diào)制器的原理鈮酸鋰調(diào)制器的主要指標(biāo)鈮酸鋰調(diào)制器的主要指標(biāo)消光比消光比插入損耗插入損耗外加電壓外加電壓偏振相關(guān)性偏振相關(guān)性10lgoffonPER dBP 1 調(diào)制器鈮酸鋰調(diào)制器調(diào)制器鈮酸鋰調(diào)制器鈮酸鋰調(diào)制器實(shí)物圖鈮酸鋰調(diào)制器實(shí)物圖1 調(diào)制器調(diào)制器EAgEhc 陡峭介質(zhì)邊吸收帶陡峭介質(zhì)邊吸收帶電吸收調(diào)制器與電吸收調(diào)制

6、器與LD集成集成 使用材料：使用材料：III-V族半導(dǎo)體材料族半導(dǎo)體材料 特點(diǎn)：特點(diǎn)：易與激光器集成易與激光器集成、體積小、驅(qū)動(dòng)電壓低（、體積小、驅(qū)動(dòng)電壓低（2V）、）、啁啾大于啁啾大于LN調(diào)制器、消光比低于調(diào)制器、消光比低于LN調(diào)制器（調(diào)制器（10dB）聲光效應(yīng)光調(diào)制器聲光效應(yīng)光調(diào)制器聲光效應(yīng)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，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。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（特點(diǎn)：消光比高（30dB）、驅(qū)動(dòng)功率較低、調(diào)制）、驅(qū)動(dòng)功率較低、調(diào)制速率低、帶寬窄速率低、帶寬窄1 調(diào)制器聲光調(diào)制器聲光

7、當(dāng)外加信號(hào)通過驅(qū)動(dòng)電源作用到聲光器件時(shí)，超聲強(qiáng)度隨此信當(dāng)外加信號(hào)通過驅(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)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。度調(diào)制。磁光效應(yīng)磁光效應(yīng)又稱為法拉第效應(yīng)。當(dāng)光通過介質(zhì)傳播時(shí)，若在垂又稱為法拉第效應(yīng)。當(dāng)光通過介質(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。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)調(diào)制原理：經(jīng)起偏器的光信號(hào)通過磁光晶體，其偏轉(zhuǎn)角與調(diào)通

8、過磁光晶體，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)偏器的透光軸相互平行，當(dāng)調(diào)制電流為零時(shí)，透過檢偏器的制電流為零時(shí)，透過檢偏器的光強(qiáng)最大；隨著電流逐漸增大，光強(qiáng)最大；隨著電流逐漸增大，旋轉(zhuǎn)角加大，透過檢偏器的光旋轉(zhuǎn)角加大，透過檢偏器的光強(qiáng)逐漸下降。強(qiáng)逐漸下降。磁光效應(yīng)光調(diào)制器磁光效應(yīng)光調(diào)制器1 調(diào)制器磁光調(diào)制器磁光OEO Regenerator1R, 2R and 3R Regeneration什么是光放大什么是光放大受激吸收受激吸收受激輻射受激輻射自發(fā)輻射自發(fā)輻射2 光放大器光放大器Regenerators vs O-Amplifiers

9、Regenerators specific to bit rate and modulation format used; O-Amps are insensitive (I.e. transparent) A system with optical amplifiers can be more easily upgraded to higher bit rate without replacing the amplifiers Optical amplifiers have large gain bandwidths Issues: Amplifiers introduce addition

10、al noise that accumulates Spectral shape of gain (flatness), output power, transient behavior need to be carefully designed2 光放大器應(yīng)用光放大器應(yīng)用2 光放大器應(yīng)用光放大器應(yīng)用 Ideal optical amplifier High power gain Broad band Flat gain-wavelength responsibility Low noise High SNR High saturation powerOptical Amplifier Typ

11、esSemiconductor optical amplifier (SOA)Fiber AmplifiersErbium doped fiber amplifier (EDFA)Praseodymium doped fiber amplifier (PDFA)Thulium doped fiber amplifier (TDFA)Stiumlated Raman fiber amplifer （SRFA）The introduction of SOA The improvement of semiconductor laser lead to FP (Fabry-Perot) semicon

12、ductor amplifier, and also to the study of traveling wave semiconductor amplifier. SOA is made of 3-5 group compound semiconductor, such as GaAs, GaP, InP Central wavelength:800nm, 1300nm,1550 nm Frequency band larger than 40 nm Gain is higher than 30 dBThe advantages of SOA Small size, and easy to

13、be integrated with semiconductor circuits. Fabrication is simple and with low power consumption, long life-span and low cost. Gain response is very quick and well suited for switching and signal processing in optical networks application. Can amplify optical signal and process signal in the same tim

14、e such as switch, so can be used in wavelength converting and optical switch.The disadvantages of SOA The coupling loss with optical fiber is too large Sensitive to polarization Noise figure is high(8 dB) Crosstalk Easy to be affected by temperature, low stability The classification of SOAThere are

15、two kinds of SOA：(1) Fabry-Perot Amplifier, FPA use the FP cavity as the optical amplifier.(2) Travelling-Wave Amplifier, TWA to coat the two end of the Fabry-Perot with anti-reflection pellicle, so acquire broadband and high power output and low noise optical amplification.The classification of SOA

16、Output amplified lightMirrorinjected currentIncidence lightMirrorFabry-Perot AmplifierThe classification of SOAanti-reflection pellicle ARinjected currentIncidence lightOutput amplified lightTraveling-Wave Amplifier, TWAanti-reflection pellicle ARFPA與與TWA的帶寬比較的帶寬比較不同反射率時(shí)不同反射率時(shí)FPSOA的的增益譜增益譜SOA的集成優(yōu)勢(shì)的集

17、成優(yōu)勢(shì)全光型波長(zhǎng)轉(zhuǎn)換器全光型波長(zhǎng)轉(zhuǎn)換器指不經(jīng)過電域處理，直接把信息從一指不經(jīng)過電域處理，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)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)換可以克服光換可以克服光-電電-光波長(zhǎng)轉(zhuǎn)換器中電器件的速度瓶頸、透光波長(zhǎng)轉(zhuǎn)換器中電器件的速度瓶頸、透明性低等不足。明性低等不足。SOA用于全光波長(zhǎng)變換用于全光波長(zhǎng)變換全光波長(zhǎng)變換器全光波長(zhǎng)變換器基于光調(diào)制原理基于光調(diào)制原理基于光混頻原理基于光混頻原理交叉增益調(diào)制（交叉增益調(diào)制（XGM）交叉相位調(diào)制（交叉相位調(diào)制（XPM）四波混頻（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，

18、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)光通常是連續(xù)光)的的放大倍數(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關(guān)。測(cè)光的轉(zhuǎn)換。它實(shí)際上可以看作是特殊的光控光開關(guān)?；诨赬GM的的SOA全光波長(zhǎng)變換全光波長(zhǎng)變換原理：原理：當(dāng)信號(hào)脈沖處于上升當(dāng)信號(hào)脈沖處于上升沿時(shí)沿時(shí),載流子密度迅速增大載流子密度迅速增大,放放大器的增益很快飽和大器的增益很快飽和,因此轉(zhuǎn)因此轉(zhuǎn)化到連續(xù)探測(cè)波上的信號(hào)為化到連續(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)

19、當(dāng)信號(hào)脈沖處于下降沿時(shí),載載流子密度迅速減小流子密度迅速減小,放大器的放大器的增益恢復(fù)增益恢復(fù),因此轉(zhuǎn)化到連續(xù)探因此轉(zhuǎn)化到連續(xù)探測(cè)波上的信號(hào)為測(cè)波上的信號(hào)為1。這樣信號(hào)。這樣信號(hào)光上的光脈沖被反轉(zhuǎn)轉(zhuǎn)化到光上的光脈沖被反轉(zhuǎn)轉(zhuǎn)化到波長(zhǎng)上。波長(zhǎng)上?；诨赬GM的的SOA全光波長(zhǎng)變換全光波長(zhǎng)變換優(yōu)點(diǎn)：優(yōu)點(diǎn)： 結(jié)構(gòu)簡(jiǎn)單結(jié)構(gòu)簡(jiǎn)單 轉(zhuǎn)換效率高轉(zhuǎn)換效率高 波長(zhǎng)轉(zhuǎn)換范圍寬波長(zhǎng)轉(zhuǎn)換范圍寬1.對(duì)偏振不敏感對(duì)偏振不敏感缺點(diǎn)：缺點(diǎn)： 輸入輸出信號(hào)反相輸入輸出信號(hào)反相 輸出消光比退化輸出消光比退化 比特率透明有限比特率透明有限 噪聲指數(shù)高噪聲指數(shù)高 啁啾大啁啾大基于基于XPM的的SOA全光波長(zhǎng)變換全光波長(zhǎng)變換XPM：當(dāng)

20、信號(hào)光和探測(cè)光共同傳播時(shí)，信號(hào)光強(qiáng)度信當(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)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，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（涉儀（MZI）、邁克爾遜干涉儀（）、邁克爾遜干涉儀（MI

21、）等。）等。優(yōu)點(diǎn)：優(yōu)點(diǎn)： 輸入信號(hào)功率小輸入信號(hào)功率小 頻率啁啾小或負(fù)啁啾頻率啁啾小或負(fù)啁啾 消光比大大提高消光比大大提高缺點(diǎn)：缺點(diǎn)：輸入功率的動(dòng)態(tài)范圍比較輸入功率的動(dòng)態(tài)范圍比較窄，所以必須對(duì)輸入信號(hào)窄，所以必須對(duì)輸入信號(hào)的功率進(jìn)行嚴(yán)格控制。的功率進(jìn)行嚴(yán)格控制?；诨赬PM的的SOA全光波長(zhǎng)變換全光波長(zhǎng)變換基于基于FWM的的SOA全光波長(zhǎng)變換全光波長(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)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，且在此參量過程中，凈能量和動(dòng)量是不同頻率的新光子，且在此參量過程中，凈能量和動(dòng)量是守恒的。由于守恒的。由于FWM能夠頗為有效地產(chǎn)生新

22、的光波，可被能夠頗為有效地產(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。利用實(shí)現(xiàn)完全透明的全光波長(zhǎng)變換。0022sppssp信號(hào)頻率信號(hào)頻率泵浦頻率泵浦頻率優(yōu)點(diǎn)優(yōu)點(diǎn)： 調(diào)制格式透明，任何信息（幅度，相位和頻率）都能保留調(diào)制格式透明，任何信息（幅度，相位和頻率）都能保留下來下來 能同時(shí)轉(zhuǎn)換多個(gè)波長(zhǎng)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)：缺點(diǎn)： 轉(zhuǎn)換效率低，轉(zhuǎn)換后信噪比惡化轉(zhuǎn)換效率低，轉(zhuǎn)換后信噪比惡化 上轉(zhuǎn)換效率比下轉(zhuǎn)換低上轉(zhuǎn)換效率比下轉(zhuǎn)換低 轉(zhuǎn)換范圍小轉(zhuǎn)換范圍小 偏振相

23、關(guān)偏振相關(guān)基于基于FWM的的SOA全光波長(zhǎng)變換全光波長(zhǎng)變換Optical Amplifier Varieties Introduction of OFA Use doped fiber as amplifying medium, such as EDF erbium doped fiber; PDF praseodymium doped fiber; TDF thulium doped fiber. In 1985, the first EDF was developed by the University of Southampton, UK In 1987, the EDFA which

24、can directly amplifying 1.5 m optical signal was developed by Bell Labs & University of Southampton at the same time. In 1994, the EDFA is available, now is a mature technology and is a key component in optical system, esp in DWDMEDFA success factors Availability of compact and reliable high-pow

25、er semiconductor pump lasers EDFA is an all-fiber device = polarization-independent & easy to couple light in/out Simplicity of device No crosstalk introduced while amplifying! EDF: Erbium ion is doped in the center of the coreHighly doped area1002000ppm erbium36um Core 125um Silica cladding250u

26、m coating Radial distanceOptical modeThe area where the energies of the pump laser and input signal exchangeThe components of EDFA摻鉺光纖中的鉺離子能級(jí)示意圖摻鉺光纖中的鉺離子能級(jí)示意圖Experimentally measured absorption spectrum of an Er3+-doped germano-alumino-silica fiber.摻鉺光纖放大器的基本結(jié)構(gòu)示意圖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)同向泵浦結(jié)構(gòu)The pump l

27、aser of EDFAPump laser source980nm1480nmpump model3 energy level2 energy levelExchange efficiency lowhighnoiselowhighcosthighlowThere two kinds of pump laser for EDFA:980nm &1480nm Compare of 980nm &1480nm pump laser sourceThe components of EDFAThe components of EDFAOptical isolatorOne way p

28、ass for optical signal. Should be low inserting loss and high separation.The input port isolator prevents backward transmission of optical signal and ASE that would decrease the stability of input port laser.The output port isolator prevents backward light enter EDF otherwise it will greatly reduce

29、the degree of population inverse, lower the gain and increase noise figure, what is more result unexpected laser resonance. Optical multiplexer To couple optical signal and pump laser into EDF. Should be low inserting loss and high bandwidth so as to promote the amplifying bandwidth of EDFA信號(hào)光輸入信號(hào)光輸

30、入信號(hào)光輸出信號(hào)光輸出WDMISOISOEDFPumpLD摻鉺光纖放大器的基本結(jié)構(gòu)示意圖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)反向泵浦結(jié)構(gòu)2 光放大器光放大器EDFA摻鉺光纖放大器的基本結(jié)構(gòu)示意圖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)雙向泵浦結(jié)構(gòu)2 光放大器光放大器EDFAThe characteristics of C-band EDFAThe relation of gain and input of EDFAsaturationGain008020406020406080泵浦功率輸出信號(hào)功率轉(zhuǎn)換效率92.6%(mW)(mW)00401020305101520泵浦功率小信號(hào)增益增益

31、系數(shù)(dB)(mW)6.3dB/mWThe characteristics of EDFAGain 增益頻譜增益頻譜.1 4801 520 1 540 1 5600246810吸收或增益波長(zhǎng)1 500/nm/(dB/m)10-25m2吸收增益截面2461E980 nm泵浦光放大后的信號(hào)光信號(hào)光1 550 nm1 550 nm0能級(jí)3rE1 530 nm980 nm2E3E0.80eV1.27eV 增益帶寬（增益帶寬（FWHM）大于大于10nm纖芯中摻入纖芯中摻入鋁離子鋁離子，帶寬還可增大且增益頻譜相當(dāng)平坦。，帶寬還可增大且增益頻譜相當(dāng)平坦。1.52025101520(dB)1.541.56波長(zhǎng)

32、( )m1.58大信號(hào)增益1.52040102030小信號(hào)增益1.541.56波長(zhǎng)( )m1.58(dB)小信號(hào)增益小信號(hào)增益EDFA的增益的增益 與鉺離子濃度、芯徑、摻雜光纖長(zhǎng)度和泵浦功率有關(guān)。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)度對(duì)于給定的放大器長(zhǎng)度（EDFEDF長(zhǎng)度），增益隨長(zhǎng)度），增益隨泵泵浦功率浦功率在開始時(shí)按指數(shù)增在開始時(shí)按指數(shù)增加，當(dāng)泵浦功率超過一定加，當(dāng)泵浦功率超過一定值時(shí)，增益增加變緩，并值時(shí)，增益增加變緩，并趨于一恒定值。趨于一恒定值。0-1010302040增益02468102015105mL=(mW)泵浦功率(dB)增益01030200-1

33、010 20 30 40 5040(m)(dB)3mWPP=24561789鉺光纖長(zhǎng)度小信號(hào)增益小信號(hào)增益0-1010302040增益02468102015105mL=(mW)泵浦功率(dB)增益01030200-1010 20 30 40 5040(m)(dB)3mWPP=24561789鉺光纖長(zhǎng)度當(dāng)泵浦功率一定時(shí)，放大當(dāng)泵浦功率一定時(shí)，放大器在某器在某一最佳長(zhǎng)度一最佳長(zhǎng)度時(shí)獲得時(shí)獲得最大增益，如果放大器長(zhǎng)最大增益，如果放大器長(zhǎng)度超過此值，由于泵浦的度超過此值，由于泵浦的消耗，最佳點(diǎn)后的摻鉺光消耗，最佳點(diǎn)后的摻鉺光纖不能受到足夠泵浦，而纖不能受到足夠泵浦，而且要吸收已放大的信號(hào)能且要吸收已放

34、大的信號(hào)能量，導(dǎo)致增益很快下降。量，導(dǎo)致增益很快下降。增益飽和（或壓縮）特性增益飽和（或壓縮）特性增益/dBm輸入功率/dB0102015-355-30 -20 -15 -10 -5 0 5-25工作點(diǎn)增益(dB)01020155-40-10-5253035/dBm輸入功率-35 -30 -20 -15 -10 -5 0-25輸出功率(dB)(dBm)噪聲指數(shù)13m9m長(zhǎng)增益線性區(qū) 增益壓縮區(qū)AB長(zhǎng)在在EDFAEDFA泵浦功率一定的情況下，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。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

35、定值后，增當(dāng)輸入信號(hào)增大到一定值后，增益開始隨信號(hào)功率的增加而下降，益開始隨信號(hào)功率的增加而下降，這是入射信號(hào)導(dǎo)致這是入射信號(hào)導(dǎo)致EDFAEDFA出現(xiàn)增益出現(xiàn)增益飽和的緣故。飽和的緣故。The characteristics of EDFAinputamplifiedamplifiedNoise Figure, NFThe characteristics of EDFAamplifiedoriginalSource Spontaneous Emission , SSEASE+ (Gain x SSE)Noise FigureGainInput signal and amplified sign

36、alThe characteristics of EDFAinputASEoutputPPPGainlog10GGsvhPSNRSNRFASEoutin1ReFdBNFlog10)(ASEP0.6nmASEPASEPCenterPsRe: resolution of spectral analyzerJ3410626. 6: Plankconstanthv: light speedG: gain of amplifierASEP: power of ASE摻鉺光纖放大器級(jí)聯(lián)后的增益響應(yīng)摻鉺光纖放大器級(jí)聯(lián)后的增益響應(yīng)2 光放大器光放大器EDFA動(dòng)態(tài)增益均衡光纖放大器的技術(shù)要求動(dòng)態(tài)增益均衡光纖放大

37、器的技術(shù)要求動(dòng)態(tài)增益均衡動(dòng)態(tài)增益均衡放大器的概念包括：放大器的概念包括： （1）增益譜平坦：）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；信道增益相同；（2）增益鎖定（自動(dòng)增益控制）：）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 其它信道增益沒有影響。其它信道增益沒有影響。要求同時(shí)實(shí)現(xiàn)平坦鎖定要求同時(shí)實(shí)現(xiàn)平坦鎖定2 光放大器光放大器EDFA 工作在工作在 77oK. 引入另外一種摻雜，如鉺鐿共摻引入另外一種摻雜，如鉺鐿共摻. EDF長(zhǎng)度、泵浦功率的優(yōu)化長(zhǎng)度、泵浦功

38、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 光纖光柵濾波光纖光柵濾波2 光放大器光放大器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 光放大器光放大器EDFA2 光放大器光放大器EDFAEDFA實(shí)物圖實(shí)物圖光纖拉曼放大器光纖拉曼放大器FRA光纖中的非線性效應(yīng)光纖中的非線性效應(yīng)SRS受激拉曼散射受激拉曼散射實(shí)現(xiàn)光信號(hào)的放大實(shí)現(xiàn)光信號(hào)的放大增益介質(zhì)：增益介質(zhì)：系統(tǒng)傳輸光纖系統(tǒng)傳輸光纖振動(dòng)態(tài)基態(tài)ps傳輸光纖信號(hào)光泵浦光濾波器信號(hào)光pss耦合器WDMFRA(a)(a)無泵激光的無泵激光的1550nm1550nm傳

39、輸傳輸(b)(b)有泵激光的有泵激光的1550nm1550nm傳輸傳輸經(jīng)光纖傳經(jīng)光纖傳輸衰減輸衰減如果一個(gè)弱信號(hào)和一個(gè)強(qiáng)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，泵浦光同時(shí)在光纖中傳輸，并使弱信號(hào)波長(zhǎng)置于泵浦并使弱信號(hào)波長(zhǎng)置于泵浦光的拉曼增益帶寬內(nèi)，則光的拉曼增益帶寬內(nèi)，則弱信號(hào)即可被放大。這種弱信號(hào)即可被放大。這種基于基于SRSSRS機(jī)制的光放大器機(jī)制的光放大器稱為光纖拉曼放大器稱為光纖拉曼放大器FRAFRA。喇曼增益波長(zhǎng)0510 15 20 2501234561443 1470 1500 1530 1560 1590 162078200mW泵浦功率泵浦光和信號(hào)光的頻率差泵浦C(THz)

40、（nm）0.00.20.40.60.81.0頻率差0 6 1218243036(THz)喇曼增益系數(shù)m/W10131mp=spRRg13.2THzgv泵浦功率100mW(dB)波段窗口硅光纖拉曼增益系數(shù)頻譜曲線硅光纖拉曼增益系數(shù)頻譜曲線增益帶寬（增益帶寬（FWHM）可以達(dá)到約可以達(dá)到約8THz喇喇曼曼增增益益波波長(zhǎng)長(zhǎng)051015202501234561443 1470 1500 1530 1560 1590 162078200mW泵泵浦浦功功率率泵泵浦浦光光和和信信號(hào)號(hào)光光的的頻頻率率差差泵泵浦浦C(THz)（nm）泵泵浦浦功功率率100mW(dB)波波段段窗窗口口 泵浦功率為泵浦功率為200

41、mW200mW時(shí)，時(shí)，最大增益值為最大增益值為7.78 7.78 dBdB 泵浦功率為泵浦功率為100 mW100 mW時(shí)，最大增益值為時(shí)，最大增益值為3.6 dB3.6 dB。 在增益峰值附近的在增益峰值附近的增益帶寬約為增益帶寬約為7 78THz8THz。小信號(hào)光在長(zhǎng)光纖內(nèi)的拉曼增益小信號(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)系放大增益和泵浦功率的關(guān)系放大器增益或放大倍數(shù)0.00.51.0泵浦功率100102101GA1.52.0103104輸入信號(hào)功率/WmW0.910.360.18mWmWL= 1.3 km1017 nm1064 nmp=s=理論計(jì)算增益飽和增益飽和FRA的

42、優(yōu)缺點(diǎn)的優(yōu)缺點(diǎn) 優(yōu)點(diǎn)優(yōu)點(diǎn)1.增益波長(zhǎng)由泵浦光波長(zhǎng)決定。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。增益介質(zhì)可以為傳輸光纖本身。3.噪聲系數(shù)低。噪聲系數(shù)低。FRA的的NF小于小于4.5dB，好于，好于SOA（約（約8dB）和）和EDFA（約（約6dB）。）。 缺點(diǎn)缺點(diǎn) 需要特大功率的泵浦激光器需要特大功率的泵浦激光器幾種光放大器的比較幾種光放大器的比較放大器放大器類型類型原理原理激勵(lì)激勵(lì)方式方式工作長(zhǎng)工作長(zhǎng)度度噪聲噪聲特性特性與光與光纖耦纖耦合合與光與光偏振偏振關(guān)系關(guān)系穩(wěn)穩(wěn)定定性性摻稀土光摻稀土光纖放大器纖放大器粒子數(shù)反粒子數(shù)反轉(zhuǎn)轉(zhuǎn)光光數(shù)米到數(shù)米到數(shù)十米數(shù)十米好好容易容易無無好好半

43、導(dǎo)體光半導(dǎo)體光放大器放大器粒子數(shù)反粒子數(shù)反轉(zhuǎn)轉(zhuǎn)電電100 m1mm差差很難很難大大差差光纖拉曼光纖拉曼放大器放大器光學(xué)非線光學(xué)非線性性(拉曼拉曼)效應(yīng)效應(yīng)光光數(shù)千米數(shù)千米好好容易容易大大好好EDFA和和FRA的混合放大應(yīng)用的混合放大應(yīng)用EDFAEDFA信號(hào)光泵浦光光接收光發(fā)射泵浦0204060800 101020功率傳輸距離10012032個(gè)波長(zhǎng)的信號(hào)光泵浦光1泵浦光2/km/dBmWDM信號(hào)-光功率在分布式拉曼放大傳輸光纖中的分布光功率在分布式拉曼放大傳輸光纖中的分布Contents (). What is the FIBER Laser ?LASER (Light Amplificatio

44、n by Stimulated Emission of Radiation) Whats the LASER ?PUMP SOURCEREAR MIRRORFRONT MIRRORROD (MEDIUM)Stimulated EmissionLaser OutputSpontaneous EmissionContents () Requisites for LASER1) MEDIUM 2) CAVITY 3) PUMP SOURCE Nd:YAG, Nd:YVO4, Nd:YLP,FIBERMirror, Fiber Bragg Gratings,coupler Flash Lamp,Las

45、er Diode YAG RODLAMP MOUNTTRIGGER WIREXENON LAMPEx) Nd:YAG, XENON LAMP PUMP TYPE LASER YAG CrystalContents () DPSS LaserNd:YAG CrystalStimulatedEmissionXenon Lamp PumpPower Supply ConnectionPartial Reflector(Mirror)Total Reflector (Mirror)Pumping DirectionLaser OutputDPSS (Diode Pumped Solid State)C

46、ontents () FIBER LASERCladding-Pumped ACTIVE FIBERFBG (Fiber Bragg Gratings)Multimode CouplerSplice to Multimode Diode PumpPump CombinerLDLDLDLDLDLDLDLDCollimated Laser OutputOptical Power MeterLensContents () Advantages of FIBER Laser, Maintenance Efficiency- No Consumable Parts- Maintenance Free-

47、Air Cooling Type (No DI Water Cooling System,去離子水冷卻系統(tǒng)去離子水冷卻系統(tǒng))Contents () Advantages of FIBER Laser, Space Efficiency- Smaller SizeCO2 LaserNd:YAG LaserDPSSFIBER1,372x495x331286x215x95Laser Outer Dimension (mm)HANMI FIBER LaserFIBER Laser is 40 times smaller than existing CO2 & DPSS Laser with e

48、xception of Laser ControllerContents (). Advantages of FIBER Laser Advantages of FIBER Laser, DurabilityElapsed Time (hr)Output Power (m W)Laser Diode Test by IPG PhotonicsLife Time : Over 100k Hrs - Laser Diodes with Longer Life-Time10 times longer than usual DPSS LaserContents () Advantages of FIB

49、ER Laser, Performance- Excellent Laser Beam QualityBest Laser Beam Quality in Semiconductor Package Marking (M2=3)- Best Solution for High Performance Advantages of FIBER Laser, Economical & Cost Saving- Lower Power Consumption- No Using DI Water Cooling System- Lower Laser Unit Price- No Consum

50、able & Free Maintenance for LaserFiber Lasersl Fiber lasers occur in a great variety of forms, serving very different applications, e.g.:Lasers generating outputs at special wavelengthsLasers for very high output power (many watts or even kilowatts) with good beam qualityQ-switched and mode-lock

51、ed lasers for short or ultrashort pulsesl Fiber technology creates a huge amount of attractive technical options, but also comes with a bunch of technical difficulties.In an optical resonator, light is confined and stored at certain resonance frequencies Light circulates or is repeatedly reflected w

52、ithin the cavity Wavelength selectivity is due to optical feedbackFabry-Perot cavityMirrorOptical fibre ring cavityFiberCouplerIsolator腔體腔體線形腔線形腔環(huán)形腔環(huán)形腔“8”字形腔字形腔pumpOptical fiber FP cavityOutput 1Output 2Active FiberpumpIsolatorOptical fiber ring cavityFiberoutputActive FiberpumpoutputFigure 8 cavity fiber la