天津大學光纖講義

1、IsolatorLD5 光隔離器光隔離器5 光隔離器光隔離器光隔離器的組成光隔離器的組成起起偏偏器器法法拉拉第第旋旋轉(zhuǎn)轉(zhuǎn)器器檢檢偏偏器器準準直直器器準準直直器器光隔離器光隔離器5 光隔離器光隔離器法拉第旋轉(zhuǎn)器的原理法拉第旋轉(zhuǎn)器的原理B磁環(huán)磁環(huán)磁光材料磁光材料光傳輸方向光傳輸方向5 光隔離器光隔離器法拉第旋轉(zhuǎn)器的原理法拉第旋轉(zhuǎn)器的原理B磁環(huán)磁環(huán)磁光材料磁光材料光傳輸方向光傳輸方向5 光隔離器光隔離器法拉第旋轉(zhuǎn)器的原理法拉第旋轉(zhuǎn)器的原理線柵起偏器的典型結(jié)構(gòu)線柵起偏器的典型結(jié)構(gòu)5 光隔離器光隔離器楔形雙折射晶體偏振分束器楔形雙折射晶體偏振分束器空間分離偏振器（空間分離偏振器（SWP）的典型結(jié)構(gòu)）的典

2、型結(jié)構(gòu)5 光隔離器光隔離器PolarizerAnalyzerFaradayRotatorPolarizerAnalyzerFaradayRotatorForward transmissionBackward transmission偏振相關(guān)隔離器原理偏振相關(guān)隔離器原理5 光隔離器光隔離器偏振無關(guān)隔離器偏振無關(guān)隔離器5 光隔離器光隔離器偏振無關(guān)隔離器偏振無關(guān)隔離器CollimatorCollimatorCore5 光隔離器光隔離器帶尾纖的偏振無關(guān)隔離器結(jié)構(gòu)帶尾纖的偏振無關(guān)隔離器結(jié)構(gòu)5 光隔離器光隔離器帶尾纖的偏振無關(guān)隔離器結(jié)構(gòu)帶尾纖的偏振無關(guān)隔離器結(jié)構(gòu)Solder ring磁光材料磁光材料鍍金環(huán)

3、鍍金環(huán)法拉第旋轉(zhuǎn)器的封裝法拉第旋轉(zhuǎn)器的封裝5 光隔離器光隔離器隔離器核心部分的封裝隔離器核心部分的封裝環(huán)氧膠環(huán)氧膠紫外紫外起偏器和檢偏器的封裝起偏器和檢偏器的封裝5 光隔離器光隔離器環(huán)氧膠環(huán)氧膠隔離器核心部分的封裝隔離器核心部分的封裝EpoxyMagnet ring核心部分的最后封裝核心部分的最后封裝5 光隔離器光隔離器隔離器核心部分的封裝隔離器核心部分的封裝4 自聚焦透鏡自聚焦透鏡0.29周期透鏡：光斑尺寸壓縮周期透鏡：光斑尺寸壓縮4 自聚焦透鏡自聚焦透鏡4 自聚焦透鏡自聚焦透鏡1/4周期透鏡：光線準直周期透鏡：光線準直 在準直器中一般采用在準直器中一般采用1/4個周期長的自聚焦透鏡，個周期

4、長的自聚焦透鏡，實現(xiàn)光束放大和準直。實現(xiàn)光束放大和準直。 自聚焦透鏡中的光束周期性地聚焦自聚焦透鏡中的光束周期性地聚焦4 自聚焦透鏡自聚焦透鏡自聚焦透鏡作準直器自聚焦透鏡作準直器準直器準直器Collimated beamFiber endReal image of the fiber endGrin Lenses(1/4 pitch)4 自聚焦透鏡自聚焦透鏡準直器尾纖的組裝準直器尾纖的組裝4 自聚焦透鏡自聚焦透鏡Cut off pointAngle polishingAR Coating4 自聚焦透鏡自聚焦透鏡準直器尾纖的組裝準直器尾纖的組裝UV AdhesiveEpoxy4 自聚焦透鏡自聚焦

5、透鏡準直器的組裝準直器的組裝Align facesMark4 自聚焦透鏡自聚焦透鏡準直器的組裝準直器的組裝P/MUV AdhesivePositioner #2 (Reference)Positioner #1 (to be assembled)準直器的組裝準直器的組裝4 自聚焦透鏡自聚焦透鏡 Tube (lens holder)準直器的組裝準直器的組裝4 自聚焦透鏡自聚焦透鏡FibX CorporationS/N: 0000 00015 光隔離器光隔離器帶尾纖的偏振無關(guān)隔離器結(jié)構(gòu)帶尾纖的偏振無關(guān)隔離器結(jié)構(gòu)光隔離器的主要參數(shù)指標光隔離器的主要參數(shù)指標 反向隔離度反向隔離度表征隔離器對反向傳輸光

6、的衰表征隔離器對反向傳輸光的衰減能力減能力,一般應(yīng)該一般應(yīng)該40dB。插入損耗插入損耗 回波損耗（回波損耗（RL）一般應(yīng)該在一般應(yīng)該在60dB以上以上 30dB隔離度帶寬隔離度帶寬一般一般20nm 5 光隔離器光隔離器偏振無關(guān)隔離器的實物圖偏振無關(guān)隔離器的實物圖5 光隔離器光隔離器隔離器用于半導體激光器中隔離器用于半導體激光器中6 光濾波器光濾波器/復用器復用器Filter TypesDiffraction gratingsFiber gratingsFabry-Perot interferometerThin-Film filterMach-Zehnder typeArrayed waveg

7、uide gratingAcousto-optic tunable filteri1d2d2112GratingplaneImagingplaneTransmissiongrating6 光濾波器光濾波器光纖光柵光纖光柵i1d2d2112GratingplaneImagingplaneReflectiongrating6 光濾波器光濾波器光纖光柵光纖光柵6 光濾波器光濾波器光纖光柵光纖光柵 resonant wavelengths are reflected back toward the source non-resonant wavelengths are transmitted thro

8、ugh the device without loss. The centre wavelength is given by:effn26 光濾波器光濾波器光纖光柵光纖光柵 500 nm (Bragg grating) 200 m (Long-period grating)125 m8 m1 mm to 1500 mmSinglemode fibreCoreCladdingRegions with higher refractive index than that of cores6 光濾波器光濾波器光纖光柵光纖光柵 1 cm FBG ，折射率變化量相對較低，反射峰值高，折射率變化量相對較低，

9、反射峰值高 其它條件相同，折射率變化量增加，反射帶寬增加其它條件相同，折射率變化量增加，反射帶寬增加(c) 切趾后的結(jié)果，旁瓣減少，反射峰值降低。切趾后的結(jié)果，旁瓣減少，反射峰值降低。6 光濾波器光濾波器光纖光柵光纖光柵Add - Drop Multiplexers Circulator with FBGAdd iDrop i 1, 2, 3, . i 1, 2, 3, . iFBGC1C2 Dielectric thin-film filter designFilter reflects iAdd / DropCommonPassbandwavelengthFor a given grati

10、ng period a particular wavelength (frequency) of light is reflected. In this case yellow light will be reflectedIf the grating spacing is changed (e.g. reduced due to compression of the fibre or a drop in temperature the wavelength of the reflected light changes. In this case it becomes higher and r

11、eflects blue lightIn practice the colour shifts will be much finer than those illustatedOptical fibreGrating pattern etched into body of fibreDetectorFiber Bragg Gratings (FBG)6 光濾波器光濾波器光纖光柵光纖光柵Fiber Brag Gratings (FBG) Increasing intervals: “chirped” FBG compensation for chromatic dispersion Regula

12、r interval pattern: reflective at one wavelength Notch filter, add / drop multiplexerOptical FibreBragg GratingsD DzD Dz 1 2 3 NDispersion Compensation using Chirped FBG FBG is linearly chirped, I.e. the period of the grating varies linearly with position. This makes the grating to reflect different wavelengths at different points along its length. Therefore, introducing different delay. In a standard fibre. Chromatic dispersion introduces larger delay for lower frequency (high waveleng