《光纖理論與技術(shù)》課件

1、光纖理論與技術(shù)哈爾濱工程大學(xué)理學(xué)院光子科學(xué)與技術(shù)研究中心2007年3月第1頁，共105頁。第十一章：發(fā)展無限的新型光纖 特種光纖光子晶體光纖第2頁，共105頁。特種光纖保偏光纖 摻稀土元素光纖 雙包層光纖 倏逝場光纖 多芯光纖 紅外光纖 納米光纖第3頁，共105頁。保偏光纖幾何形狀引起高雙折射 高雙折射橢圓芯保偏光纖結(jié)構(gòu)剖面示意圖 第4頁，共105頁。保偏光纖應(yīng)力誘導(dǎo)高雙折射 第5頁，共105頁。保偏光纖第6頁，共105頁。摻稀土元素光纖 摻稀土元素光纖是采用某種工藝技術(shù)將釹、鉺和釔等稀土元素離子單獨(dú)或混合摻入光纖芯中而制成的。目前主要是摻雜到光纖纖芯中的，但亦有同時(shí)摻雜到光纖包層中去的。其摻

2、雜濃度可從1 PPm到0.25 w% 的寬廣范圍內(nèi)變化。 第7頁，共105頁。 纖芯中摻雜稀土元素有 Er、Yb、Nd、Tm、Pr、Er/Yb、Ho等 纖芯直徑4mm，NA 0.1 包層直徑125mm，形狀為圓形摻稀土元素光纖 第8頁，共105頁。摻稀土元素光纖用這種摻雜光纖可以獲得四方面的應(yīng)用： (1) 激光光纖與光纖放大器； (2) 基于吸收、熒光的分布溫度傳感； (3) 增大菲爾德常數(shù)； (4) 提高克爾效應(yīng)及非線性光學(xué)系數(shù)。 第9頁，共105頁。雙包層光纖 雙包層光纖及其工作原理 第10頁，共105頁。 纖芯中摻雜稀土元素有： Er、Yb、Nd、Tm、Pr、Er/Yb、Ho等 單模光纖

3、 ：纖芯小4mm，NA 0.1 纖芯結(jié)構(gòu)分類 大芯多模光纖：纖芯大（30mm），NA大 大模面積（LMA）：纖芯大（30mm ）， NA?。?.1）內(nèi)包層光纖芯外包層保護(hù)層激光輸出泵浦光雙包層光纖 第11頁，共105頁。 內(nèi)包層形狀 圓形（同心、偏心） 方形、矩形、六邊形、星形 和 D 形 圓形偏心內(nèi)包層圓形同芯內(nèi)包層雙包層光纖 第12頁，共105頁。 矩形內(nèi)包層星形內(nèi)包層方形內(nèi)包層D形內(nèi)包層六邊形內(nèi)包層雙包層光纖 第13頁，共105頁。雙包層光纖用包層泵浦的光纖激光特種光纖 第14頁，共105頁。倏逝場光纖 主要用途：倏逝場光纖生化傳感器 電光克爾效應(yīng)調(diào)制器 第15頁，共105頁。多芯光纖

4、主要用途：密集型光纜光子器件用于圖像傳遞的傳像光纖 第16頁，共105頁。紅外光纖方形中空光纖芯紅外光纖 第17頁，共105頁。納米光纖第18頁，共105頁。第19頁，共105頁。第20頁，共105頁。第十一章：發(fā)展無限的新型光纖 特種光纖光子晶體光纖第21頁，共105頁。ContentsIntroductionWhat is photonic crystal fiber ? Working principle of PCFStructures of photonic crystal fiberCharacteristics of crystal fiberFabrication of cry

5、stal fiberApplications What we have done ?Conclusions第22頁，共105頁。Introduction Photonic crystal fibers (PCFs) was first demonstrated in 1996 and has generated much attention since then. PCFs are optical fibers that employ a microstructured arrangement of low-index material in a background material of

6、higher refractive index. The background material is often undoped silica and the low index region is typically provided by air voids running along the length of the fiber. 第23頁，共105頁。Growth trend of publicationsPublication papers cited by SCI from 19962003330+?第24頁，共105頁。What is photonic crystal fib

7、er ? Photonic crystal fibers, also known as microstructured fibers are a brand new range of optical fibers offering significant new possibilities and functionality within telecommunications and optical components in general. 第25頁，共105頁。Two categories photonic crystal fiber PCFs may be divided into t

8、wo categories, high index guiding fibers and low index guiding fibers. Similar to conventional fibers, high index guiding fibers are guiding light in a solid core by the Modified Total Internal Reflection (M-TIR) principle. The total internal reflection is caused by the lower effective index in the

9、microstructured air-filled region. 第26頁，共105頁。Working principle of crystal fiber Low index guiding fibers guide light by the photonic bandgap (PBG) effect. The light is confined to the low index core as the PBG effect makes propagation in the macrostructured cladding region impossible. The strong wa

10、velength dependency of the effective refractive index and the inherently large design flexibility of the PCFs allows for a hole new range of novel properties. Such properties include endlessly single-moded fibers, extremely nonlinear fibers and fibers with anomalous dispersion in the visible wavelen

11、gth region. 第27頁，共105頁。Working principle of crystal fiberM-TIR is analogous to total internal reflection known from standard optical fibers. It relies on a high index core region, typically pure silica, surrounded by a lower effective index provided by the microstructured region. The effective index

12、 of such a fiber can, in the simple case, be approximated by standard a step index fiber, with a high index core and a low index cladding. However, the refractive index of the microstructured cladding in PCFs exhibits a wavelength dependency very different from pure silica - an effect which allows P

13、CFs to be designed with a complete new set of properties not possible with standard technology. Step index fiber 第28頁，共105頁。Working principle of crystal fiberPhotonic crystal fiber As an example, the strong wavelength dependence of the refractive index allow design of endlessly single-moded fibers,

14、where only a single mode is supported regardless of optical wavelength. Furthermore, it is possible to alter the dispersion properties of the fibers, thereby making it possible to design fibers with an anomalous dispersion at visible wavelengths.More complex index structures can also be constructed

15、by utilizing arrangements of holes of different size in various periodic or unperiodic structures. In addition, highly asymmetric core fibers can be fabricated thereby creating fibers with very high level of birefringence. 第29頁，共105頁。Working principle of crystal fiberPhotonic bandgap fibers are base

16、d on physical mechanisms fundamentally different from the M-TIR guiding fibers. The bandgap effect can be found in nature, where the beautiful and bright colors that are seen in butterfly wings are the result of naturally occurring periodic microstructures. The SEM picture at the lower left shows th

17、e microstructure on a butterfly wing. The structure size is in the order of a few microns. In a PBG fiber, the core is created by introducing a defect in the PBG structure (e.g. an extra air hole), thereby creating an area where the light can propagate. 第30頁，共105頁。Working principle of crystal fiberA

18、s the light can only propagate at the defect region, a low index guiding core has been created. This is not possible in standard fibers, and the low index guiding of PBG fibers therefore opens a whole new set of possibilities. In this way, it is possible to guide light in air, vacuum or any gas comp

19、atible with the fiber material. Especially the possibility for guiding in air or vacuum has attracted much attention, as it might hold the key to transmission fibers with extremely low losses. 第31頁，共105頁。Working principle of crystal fiber The different guiding mechanisms. (A) Conventional total inte

20、rnal reflection (TIR); this occurs when the wave vector component in the direction of propagation lies in the range kn2 kn1. (B) PBG guidance when the light is evanescent in the air regions; this can only occur when lies in the same range as in (A); the process is one of frustrated tunneling, that i

21、s, the cladding resonators are out of resonance with the core waveguide and hence tunneling is prevented. 第32頁，共105頁。Working principle of crystal fiber (C) PBG guidance when the light is propagating in all subregions of the fiber; this can only occur when lies in the range kn2, the underlying mechan

22、ism being a Bragg PBG.第33頁，共105頁。PBG PCF第34頁，共105頁。Basic explanation 第35頁，共105頁。Vector analysis of PCF fiber第36頁，共105頁。Structures of crystal fiberTypical honeycomb based PCF structure 第37頁，共105頁。Air-guiding PCFLow bend loss: unnoticeable 3mm radiusLow Fresnel reflection: 10-4Reduced nonlinearitiesPo

23、tential ultra-low loss transmission第38頁，共105頁。Structures of crystal fiber第39頁，共105頁。Structures of crystal fiber第40頁，共105頁。1.7 m Core Highly Nonlinear FiberFEATURES:- Small mode field area- Zero dispersion in the visible wavelength range- Bending insensitive APPLICATIONS:- Continuum generation- Four-

24、wave mixing- Raman amplification第41頁，共105頁。15 m Core Large Mode Area Fiber FEATURES: - Handles very high power levels without nonlinearities- Low fiber loss APPLICATIONS: -High power delivery 第42頁，共105頁。High Numerical Aperture PCFHigh numerical aperture (NA): up to 0.7Large core areaLow nonliearitie

25、s第43頁，共105頁。Double Cladding PCF Extremely high NA for the pump core/inner cladding.Large mode area for signal mode signal: high power delivery, low nonlinearity, and a good overlap between pumping and signal area (high pump efficiency)第44頁，共105頁。Highly Nonlinear Polarization Maintaining Fiber FEATUR

26、ES: - Polarization Maintaining- Small mode field area- Zero dispersion in the visible wavelength range- Bending insensitive APPLICATIONS: - Continuum generation- Four-wave mixing- Raman amplification 第45頁，共105頁。Endlessly Single-Mode FiberEndlessly single-mode large mode area PCF can handle up to 20

27、times more power than conventional fiber and is made entirely from un-doped silica glass.第46頁，共105頁。Endlessly Single-Mode FiberActual unit cell in the photonic crystal with Its circular approximation Variation of Veff with /for various relative hole diameters d/. The dashed line marks Veff = 2.405,

28、the cutoff V value for a step-ndex fiber第47頁，共105頁。Chromatic Dispersion 第48頁，共105頁。Anomalous dispersion第49頁，共105頁。Supercontinuum GenerationSuper continuum generation in a 75cm length of PCF. The fiber is pumped with 100fs, 680nm pulse. The pulse energy is 1nJ.第50頁，共105頁。Loss properties3.2 dB/km at 1

29、550 nm7.1 dB/km at 850 nm 2 km length fiber第51頁，共105頁。Macro-bending loss properties第52頁，共105頁。Highly birefringent propertiesBeat length = 0.4 mmAt wavelength 1540 nm第53頁，共105頁。Fabrication of crystal fiberFabrication of PCF, like in conventional fiber fabrication, starts with a fiber preform. PCF pre

30、forms are formed by stacking a number of capillary silica tubes and rods to form the desired air/silica structure. 第54頁，共105頁。Fabrication of crystal fiberThis way of creating the preform allows a high level of design flexibility as both the core size and shape as well as the index profile throughout

31、 the cladding region can be controlled. This is very useful for fabrication of e.g. polarization maintaining fibers with highly asymmetric core regions, where multiple of the capillary tubes is replaced with solid silica rods. 第55頁，共105頁。Fabrication of crystal fiberWhen the desired preform is constr

32、ucted, it is drawn to a fiber in a conventional high-temperature drawing tower and hair-thin photonic crystal fibers are readily produced in kilometer lengths. Through careful process control, the air holes retain their arrangement all through the drawing process and even fibers with very complex de

33、signs and high air filling fraction can be produced. 第56頁，共105頁。Fabrication of PCF第57頁，共105頁。Fabrication of crystal fiberFinally, the fibers are coated to provide a protective standard jacket that allows robust handling of the fibers. The final fibers are comparable to standard fiber in both robustn

34、ess and size and can be both striped and cleaved using standard tools. 第58頁，共105頁。Applications of PCF Fiber delivery of very high-power light, single- mode from UV to infrared;2. Dispersion compensation ;3. White light (supercontinuum) sources ;4. Wavelength converters ;5. Hollow transmission fibers

35、 ;6. Multi-core fiber couplers ;7. Pulse shapers ;第59頁，共105頁。Applications of PCF Chemical sensors with long interaction lengths ;9. Temperature-insensitive PM pigtails ; Gyroscope fibers-athermal, and highly birefringent 11. Pressure and temperature sensors ; High Aeff and PM fibers for single-mode

36、interconnects ;13. Mode converters 第60頁，共105頁。High-power light delivery 第61頁，共105頁。White-light supercontinuum generation experiment第62頁，共105頁。White-light supercontinuum generationPropagation lengths 40 cm, 1.3 m, and 2.6 m第63頁，共105頁。Wavelength converter 第64頁，共105頁。Wavelength converterOutput spectra

37、for different values of incident peak power第65頁，共105頁。This fiber guided pink light (core 14 microns in diameter) Using air core as the medium almost entirely eliminates optical nonlinearities so the nonlinear power threshold can be more than 1000 times higher than that of a conventional fiber. Hollo

38、w Core Bandgap Fiber第66頁，共105頁。Multicore PCF and Multicore couplerApplications:1.Strain sensor;2.Temperature sensor3.Pressure sensor第67頁，共105頁。Dispersion compensation第68頁，共105頁。PCF using as gas sensor第69頁，共105頁。Testing result of acetylene gas第70頁，共105頁。Acoustic wavelength-shift modulator第71頁，共105頁。T

39、win core PCF fiber as temperature sensor 第72頁，共105頁?！癐 tried to think of something different, something nobody else had thought of ” -Philip St. John Russell 第73頁，共105頁。The idea of Photonic crystal fiber 第74頁，共105頁。Microstructured fiber used as an atom waveguide第75頁，共105頁。Coaxial periodic optical fi

40、ber第76頁，共105頁。Segmented cladding fiber第77頁，共105頁。Air suspended core fiber for producing efficient evanescent field devices 第78頁，共105頁。What we have done ?Invention patents about plastic photonic crystal fiber designResearch on mode field distribution and dispersion characteristics of photonic crystal

41、 fiberSimulation of highly birefringent PCF Splice loss estimation of PCF/SMFAnalysis for tapered photonic crystal fiberAnalysis of combination structured photonic crystal fibers第79頁，共105頁。Hollowly plastic photonic crystal fiber design and fabrication technique第80頁，共105頁。Basic equations第81頁，共105頁。Cr

42、oss section of the PCF with a pitch of 2.3 第82頁，共105頁。Contour maps of the energy distribution of fundamental mode第83頁，共105頁。Three dimensional mode field distributions 第84頁，共105頁。Energy distribution of central axis 第85頁，共105頁。V parameter of a PCF versus the normalized frequency 第86頁，共105頁。Effective i

43、ndex of a PCF versus the normalized frequency 第87頁，共105頁。Effective index of a PCF versus wavelength 第88頁，共105頁。Dispersion as a function of wavelength 第89頁，共105頁。Dispersion as a function of wavelength 第90頁，共105頁。Propagation constant vs the wavelength 第91頁，共105頁。Modeling of Highly Birefringent PCF The

44、 cross-section of the PCF and electric field vectors of the y-polarized fundamental mode. Dependence of modal birefringence on the size of holes.第92頁，共105頁。The mode field diameter and half divergence angle as a function of wavelength for various d2/. The dashed and solid lines corresponds to x and y directi