光通信中的光器件

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1、孙军强Email：jqsun@mail.hust.edu.cnMobile:1365721602812012/12/20©HUST2012主要内容主要内容ò光耦合器、光隔离器ò光纤光栅、阵列波导光栅ò光开关与波长转换器件22012/12/20©HUST2012光纤耦合器1α1-αα：couplingratio3dBcoupleα=1/2α=0.95(formonitoring)32012/12/20©HUST2012PrincipleofOperationPrincipleofOperationa→1→b1→ba→2

2、2⎛E01(f)⎞−iβl⎛cos(kl)isin(kl)⎞⎛Ei1(f)⎞E:electricalfield⎜⎟=e⎜⎟⎜⎟⎜E()f⎟⎜isin()klcos()kl⎟⎜E()f⎟S-parameters⎝02⎠⎝⎠⎝i2⎠Forlosslesscouplers⎛b1⎞⎛s11s12⎞⎛a1⎞⎜⎟=⎜⎟⎜⎟⎜⎟⎜⎟⎜⎟bssa⎝2⎠⎝2122⎠⎝2⎠l:thecouplinglengthk:couplingcoefficientdependingonwidth,shapeofwaveguides,refracti

3、veindex,distance…42012/12/20©HUST2012Thepowertransferfunction2Ei:input;j:output()0jTf=ij2Eii()2⎛T11f⎞⎛cos(kl)⎞⎜⎟=⎜⎟⎜T()f⎟⎜sin2()kl⎟⎝12⎠⎝⎠Fora3dBcoupler1T()f=T()f=111221πcos2()kl=sin2()kl=kl=()2n+1;n=0,1,2L2452012/12/20©HUST2012ConservationofEnergy(S-parameter)⎛

4、E01⎞⎛s11s12⎞⎛Ei1⎞⎜⎟=⎜⎟⎜⎟⎜⎟⎜⎟⎜⎟EssE⎝02⎠⎝2122⎠⎝i2⎠Thescatteringmatrixis:⎛s11s12⎞⎜⎟s:complex⎜⎟ijss⎝2122⎠Denote()TE=EE00102()TE=EEii1i2E=SE0iThesumofinputpowerisproportionaltoT*22EE=E+E(*complexconjugate)00i1i262012/12/20©HUST2012Similarlythesumofoutputpowerispropo

5、rtionaltoT*22EE=E+E000102IfitislosslessT*()T()*T()T**T*EE=SESE=ESSE=EE00iiiiiiThisrelationholdsforarbitraryEi⇒STS*=I(I:identitymatrix)Theaboveexpressioncanbeextendedtoanynumberofports72012/12/20©HUST2012Fora2Fora2××2symmetricalcoupler2symmetricalcouplers=s=as=s

6、=b21122211T*SS=I22a=cos(x)b=sin(x)a+b=1**ab+ba=0LetLeta=cos()xeiϕa,b=sin(x)eiϕb**cos(x)sin(x)[ei(ϕa−ϕb)+ei(ϕb−ϕa)]=0ab+ba=0()⎛2k+1⎞cosϕa−ϕb=0ϕa=ϕb±⎜⎟π⎝2⎠Losslesscombinationisimpossible!Losslesscombinationisimpossible!82012/12/20©HUST2012Y型光纤耦合器0.5:0.51.0:0.00.0

7、:1.02cos(Kz)2R11'sin(Kz)δ=0π2πKz2'92012/12/20©HUST2012RS+=1R+S=1RS+=1Y型光纤耦合器2cos(Kz)2sin(Kz)δ=0π2πKzR11'()1RS+max=RS+≠2对相同波长、相同光功率的耦合会S2产生3dB损耗。102012/12/20©HUST2012不同波长、相同光纤间的耦合：R2(z)=cos2(K(λ)z)δ≠0S2(z)=sin2(K(λ)z)光纤复用耦合器λ1λ+λ12λ21'11'2λ12cos(())Kzλ2sin(())Kλ

8、zR11'λ2Kz()λS2112012/12/20©HUST2012光纤解复用耦合器λ1λ+λ122cos(())Kzλ11'λ1λ2R11'λ2Kz()λ2'122012/12/20©HUST2012132012/12/20©HUST2012NonlinearOpticalLoopMirror(NOLM)A0AAfrAbAt[(22)]A'