第三章光纤通信器件

1、用户网传输网交换网接入网光 有 源 器 件光 无 源 器 件关键技术：SDH ATMTDMWDMTDMWDM支撑基础：定义：定义：需要外加能源驱动工作的光电子器件需要外加能源驱动工作的光电子器件半导体光源半导体光源(LD,LED,DFB,QW,SQW,VCSEL)(LD,LED,DFB,QW,SQW,VCSEL)半导体光探测器半导体光探测器(PD,PIN,APD(PD,PIN,APD）光纤激光器（光纤激光器（OFL:OFL:单波长、多波长）单波长、多波长）光放大器光放大器(SOA,EDFA)(SOA,EDFA)光波长转换器光波长转换器(XGM,XPM,FWM)(XGM,XPM,FWM)光调制器

2、（光调制器（EAEA）光开关光开关/ /路由器路由器定义：定义：不需要外加能源驱动工作的光电子器件不需要外加能源驱动工作的光电子器件光纤连接器（固定、活动光纤连接器（固定、活动,FC/PC,FC/APC,FC/PC,FC/APC）光纤定向耦合器光纤定向耦合器/ /分支器分支器光分插复用器（光分插复用器（OADM)OADM)光波分光波分/ /密集波分复用器（密集波分复用器（WDM/DWDM)WDM/DWDM)光衰减器（固定、连续）光衰减器（固定、连续）光滤波器（带通、带阻）光滤波器（带通、带阻）光纤隔离器与环行器（偏振有关、无关）光纤隔离器与环行器（偏振有关、无关）光偏振态控制器、光纤延迟线、光

3、纤光栅光偏振态控制器、光纤延迟线、光纤光栅电线 光纤 调制器 光调制器 电阻 光衰减器 三通（多通） 光耦合器 二极管 光隔离器 混频器 光波分复用器 放大器 光放大器 频率转换器 光波长转换器 滤波器 光滤波器 电载波 光载波 电接插件 光连接器 探头 光探测器 开关 光开关 集成电路 集成光路 多波长光源多波长光源DWDM光调制器光调制器光隔离器光隔离器光耦合器光耦合器光波长转换光波长转换光放大光放大DWDM光色散补偿光色散补偿光隔离器光隔离器光环行器光环行器光波长转换光波长转换OADMDWDM光隔离器光隔离器光环行器光环行器光开关光开关可调谐滤波可调谐滤波DWDMOXC光耦合器光耦合器光

4、调制解调光调制解调 光电变换器件 光开关与调制器件 光放大器件 光色散补偿器件 光网络器件 F-P腔激光二极管(LD) 分布反馈布拉格激光器(DFB) 分布布拉格反射激光器(DBR) 外腔激光器与Q开关激光器 发光二极管(LED) 光纤激光器(OFL) 垂直腔表面发射激光器(VCSEL) 多波长光源与波长可调谐激光器多波长光源与波长可调谐激光器 光电探测器(PD、PIN、APD) 幅度调制 机械调制 电光调制 直接调制 电吸收光调制(EA) 相位调制 偏振调制 光电集成芯片(OEIC) 光子集成芯片(PIC) 掺铒光纤放大(EDFA) 掺镨光纤放大(PDFA) 掺钕光纤放大(NDFA) 分布式

5、光纤放大 喇曼光纤放大(SRFA) 布里渊光纤放大(SBFA) 半导体光放大(SOA) 色散控制 色散位移单模光纤 非零色散位移单模光纤 大有效截面单模光纤 色散平坦单模光纤 色散补偿 色散补偿光纤模块 SOA色散补偿 光纤光栅色散补偿 色散管理色散补偿说明： Different wavelengths travel at slightly different speeds(this effect is called “Chromatic Dispersion”) Chromatic dispersion causes pulse broadening(problem at high bit

6、rates over long distances) Standard single-mode fiber: 1300 nm window has lowest CD1550 nm lowest loss 光耦合透镜（自聚焦透镜、玻璃球透镜） 光连接器与光耦合器 光隔离器与光环行器 光滤波与光波分复用器件 光起偏器与偏振控制器 光波长转换与光波长路由器件 光调制解调器（Optical Modem） 光衰减器与光延时器件 光开关与光交叉连接器件 微光电机械芯片光器件技术光器件技术 光纤技术 微光学（Microoptics) technology 平面波导（Planar waveguide）技术

7、微光电机械(Micro-Optic-Electronic-Mechanic）技术 Fibre is not only a transmission medium. （光纤不仅仅是传输媒体） Many devices such as amplifiers and filters can be made from fibre. （许多器件是由光纤制成，如光纤放大器、滤波器等） Components usually end up connected to a fibre for transmission. （器件与光纤相连便于传输） 器件由传统的光学元件，如透镜、棱镜、衍射光栅等，装配而成 尺寸小，

8、精度高 装配难度高，机械程度低 较昂贵 采用半导体芯片制造技术，由硅或其它半导体材料在平板上所形成的器件（Devices are constructed on the surface of a flat piece of material such as silica or semiconductor crystal using the techniques of semiconductor chip manufacturing)光源和光接收器/Light-emitting Diode (LED) 原理：半导体PN结发光（自发辐射光） 光谱：宽带光谱 应用：短距离、小容量数据通信（通过空间/多

9、模光纤传输） Key characteristics Most common for 780, 850, 1300 nm Total power up to a few W Spectral width 30 to 100 nm Coherence length 0.01 to 0.1 mm Little or not polarized Large NA ( poor coupling into fiber)P -3 dBP peakBW光源和光接收器/ FP( Fabry-Perot ) Laser 原理：半导体PN结发光 平行平面反射腔 激光 光谱：多纵模光谱 （Multiple lon

10、gitudinal mode ，MLM) 应用： “Classic” semiconductor laserFirst fiberoptic links (850 or 1300 nm)Today: short & medium range linksP peakIPThreshold光源和光接收器/ FP( Fabry-Perot ) Laser Key characteristics Most common for 850 or 1310 nm Total power up to a few mw Spectral width 3 to 20 nm Mode spacing 0.7

11、 to 2 nm Highly polarized Coherence length 1 to 100 mm Small NA ( good coupling into fiber)光源和光接收器/ FP( Fabry-Perot ) LaseryxzSOP: linearhorizontalSOP: linearvertical偏振（Polarization）说明： Most lasers are highly polarized Degree of polarization (DOP):DOP = P polarized / P total State of polarization (S

12、OP):describes the orientationand rotation of thepolarized light光源和光接收器/分布反馈 (DFB) Laser 原理：半导体PN结发光 分布反馈反射腔 激光 光谱：单纵模光谱 (Single longitudinal mode， SLM) 应用： High performance telecommunication laser Most expensive (difficult to manufacture)Long-haul links & DWDM systemsP peakSMSR光源和光接收器/分布反馈 (DFB)

13、 Laser Key characteristics Mostly around 1310/1550 nm Total power 3 to 50 mw Spectral width 10 to 100 MHz (0.08 to 0.8 pm) Sidemode suppression ratio (SMSR): 50 dB Coherence length 1 to 100 m Small NA ( good coupling into fiber)光源和光接收器/ 垂直腔面发光激光器 Vertical Cavity Surface Emitting Lasers (VCSEL) Distr

14、ibuted Bragg Reflector (DBR) Mirrors Alternating layers of semiconductor material 40 to 60 layers, each l / 4 thick Beam matches optical acceptance needs of fibers more closely Key properties Wavelength range 780 to 980 nm (gigabit ethernet) Spectral width: -10 dBm Coherence length:10 cm to10 m Nume

15、rical aperture: 0.2 to 0.3activen-DBRp-DBROther Light Sources White light source Specialized tungsten light bulb Wavelength range 900 to 1700 nm, Power density 0.1 to 0.4 nw/nm (SM), 10 to 25 nw/nm (MM) Amplified spontaneous emission (ASE) source “Noise” of an optical amplifier without input signal

16、Wavelength range 1525 to 1570 nm Power density 10 to 100 w/nm External cavity laser Most common for 1550 nm band (some for 1310 nm) Tunable over more than 100 nm, power up to 10 mw Spectrum similar to DFB laser, bandwidth 10 kHz to 1 MHzPhotodiodes(光电管） PIN (p-layer, intrinsic layer, n-layer) Highly

17、 linear, low dark current Avalanche photo diode (APD) Gain up to x100 lifts detected optical signal above electrical noise of receiver Best for high speed and highly sensitive receivers Strong temperature dependence Main characteristics Quantum efficiency (electrons/photon) Dark current Responsivity

18、 (current vs. L L)n+Bias VoltageAPD GainMaterial Aspects Silicon (Si) Least expensive Germanium (Ge) “Classic” detector Indium gallium arsenide (InGaAs) Highest speedWavelength nm50010001500SiliconGermaniumInGaAsQuantum Efficiency = 10.10.51.0Responsivity (A/W) 类型 *T型耦合器 *星型耦合器 *定向耦合器 * 波分复用/解复用器 结构

19、 *光纤型 *微光学器件型 主要技术指标 *耦合比(CR) * 插入损耗(IL) * 附加损耗(EL) *方向性（DL) * 隔离度（Is) *一致性（U) 常用耦合器类型 IL(Insertion Loss) IL=-10lg Reflect the power to each port. CR(Coupling Ratio) CR= EL(Excess Loss) EL=-10lg The total loss on coupler PoutPinPout1Pout1+Pout2Pout1+Pout2Pin DL DL = 10Log(Pj / Pi) 方向性对传输系统的影响 *同路异向双

20、信道对传系统 M X N器件i1jM1N发射1接收2发射2接收1 *同路同向双信道传输系统 * 树形网传输系统 发射1发射2接收2接收1发射1XN * 光纤耦合器 光纤定向耦合 星型 光纤分波/合波 原理单模光纤传播 Equations：dR/dz- jdR = -jKS; dS/dz+ jdS = -jKR A=R exp(-jdz); An= S exp(jdz) Detuning coefficient：d=(bn-b)/2 Coupling coefficient: K 方程解 )sin()sin()cos(2222222222zKKjKSzKKjzKRdddddd-= 波分复用/解复

21、用原理 微器件型耦合器 波导型耦合器 An isolator is a device that allows light to pass along a fibre in one direction but not in the opposite direction.Isolators/应用 Main application: To protect lasers and optical amplifiers from light coming back (which otherwise can cause instabilities) Insertion loss: Low loss (0.2

22、 to 2 dB) in forward direction High loss in reverse direction:20 to 40 dB single stage, 40 to 80 dB dual stage) Return loss: More than 60 dB without connectorsIsolators/工作原理 隔离器工作原理 Light entering at any particular port (say port 1) travels around the circulator and exits at the next port (say port

23、2). Light entering at port 2 leaves at port 3 and so on.Circulators/应用Circulator & chirped FGB configured to compensate CD Optical crystal technology similar to isolators Insertion loss 0.3 to 1.5 dB, isolation 20 to 40 dBTypical configuration: 3 port device Port 1 -Port 2 Port 2 -Port 3 Port 3

24、-Port 1Fast l lSlow l l环形器应用：Add / Drop NodesFilter reflects l l iAdd l l iAdd / DropDielectric thin-film filter designCirculator with FBG designCommonPassbandDrop l l iFilter Characteristicsl l i-1l l il l i+1PassbandCrosstalkCrosstalk Passband Insertion loss Ripple Wavelengths(peak, center, edges)

25、 Bandwidths (0.5 dB, 3 dB, .) Polarization dependence Stopband Crosstalk rejection Bandwidths (20 dB, 40 dB, .)Dielectric Filters Thin-film cavities Alternating dielectric thin-film layers with different refractive index Multiple reflections cause constructive & destructive interference Variety of filter shapes and bandwidths (0.1 to 10 nm) Insertion loss 0.2 to 2 dB, stopband rejection 30 to 50 dBLayersSubstrateIncoming SpectrumReflected SpectrumTransmitted Spectrum1535 nm1555 nm0 dB30 dBTunable Fabry-Perot Filters Filter shape Re