一种与标准单模光纤高适配的低弯曲损耗光子晶体光纤

设计并研制出一种与普通单模光纤高适配的低弯曲损耗光子晶体光纤. 结构采用光纤预制棒制作工艺上易于实现的掺锗芯六孔结构. 应用间接测量方法, 对其模式、弯曲及色散特性进行了系统的评估. 在波长1550 nm处研制光纤的模场面积为79.26 μm², 色散为21.7 ps·km^-1·nm^-1, 模场面积和色散特性与标准单模光纤具有高的适配性. 在光纤弯曲半径为5 mm时, 在波长1550 nm处的弯曲损耗为0.0365 dB/圈, 小于G.657B的弯曲损耗0.5 dB/圈. 研究成果为光纤到户用低弯曲损耗光纤的实用化奠定了良好的基础. 关键词： 光子晶体光纤 低弯曲损耗 光纤到户 高适配性     

光器件用选择截止特种单模光纤的开发

对器件用特种单模光纤的弯曲损耗进行了理论分析,并采用Matlab对弯曲损耗进行了仿真数值分析,研究了单模光纤宏弯损耗和微弯损耗随光纤波导结构及波长的变化规律,并优化了光纤波导结构,开发出抗弯性能优良的单模光纤,同时具有较低的熔接损耗。     

新型抗弯曲大模场面积光子晶体光纤

研制出一种新型抗弯曲大模场面积石英光子晶体光纤. 利用光子晶体光纤结构设计的灵活性, 通过规划缺陷的位置及空气孔的尺寸, 实现了大模场面积单模及低弯曲损耗特性.应用建立的实际光子晶体光纤特性分析模型, 研究了研制光纤的模式特性和弯曲特性, 在波长1064 nm处, 平直状态下光纤的模场面积可以达到2812 μm², 基模限制损耗为0.00024 dB/m, 高阶模限制损耗高于1.248 dB/m. 基模和高阶模之间的高传输损耗差, 保证了在获得大模场面积的同时实现单模传输. 弯曲半径和弯曲方向角所带来弯曲损耗变化的研究结果显示, 即使在弯曲半径小到5 cm时, 弯曲损耗也在10^-3 dB/m量级以下, 而且在弯曲半径为30 cm时光纤可承受的弯曲方向角范围扩展至-60°–60°. 研制的光纤具有良好的低弯曲损耗特性, 可有效解决非对称结构所带来的光纤弯曲特性对弯曲方向角敏感的问题. 该光纤在高功率光纤激光器、放大器及高功率传输等技术领域具有重要的应用价值. 关键词： 光子晶体光纤 大模场面积 低弯曲损耗 弯曲方向角     

用于液压传感的双芯光子晶体光纤

采用全矢量有限元方法进行光纤设计优化,得到横截面上失去两层空气洞的双芯光子晶体光纤,可用于液压传感.优化的双芯光子晶体光纤的模场半径和数值孔径与单模光纤基本一致,在优化的双芯光子晶体光纤和单模光纤之间有一个相对较低的熔接损耗.计算结果表明由模场半径和数值孔径导致的不匹配造成的总共损耗可低至0.026 dB,低于传统光子晶体光纤和单模光纤0.1 dB的直接熔接损耗.对基于20 cm双芯光子晶体光纤的液压传感器的性能进行研究,结果表明在0～500 MPa量程内的灵敏度为-1.6 pm/MPa.     

基于薄芯光纤模态干涉技术的折射率 传感特性实验研究

报道了一种具有微结构缺陷的折射率传感器,并对其折射率特性进行了实验研究.将一部分薄芯光纤熔接于标准单模光纤中,由于插入的薄芯光纤和单模光纤纤芯失配,导致包层的高次模被激发并与纤芯模在单模光纤内形成干涉仪.通过减小薄芯光纤的包层直径,以增强包层中的传输模在环境中的倏逝场,从而提高对环境折射率测量的灵敏度.实验表明,该折射率传感器具有损耗低、成本低、灵敏度高和线性度好等特点.     

全固态双层芯结构色散补偿微结构光纤

提出了一种全固态双层芯结构色散补偿微结构光纤。该光纤以纯石英材料为基底,通过引入一种掺锗高折射率石英柱和两种掺氟/硼的低折射率石英柱,对端面折射率分布进行调节,以形成双芯结构。在对此光纤模式演化及耦合特性理论分析的基础上,利用多极法对其模式耦合位置与强度随光纤结构参数变化的关系进行了分析,对色散特性与光纤结构参数之间的变化关系进行了研究。通过优化光纤结构参数,设计出两种光纤:光纤1在1550nm处色散值达-8465ps/(nm·km),与SMF-28单模光纤熔接损耗仅为1.89dB,可对长度为其500倍的SMF-28单模光纤的色散值进行补偿;光纤2与SMF-28单模光纤的熔接损耗仅为1.41dB,可对长度为其15.5倍的SMF-28单模光纤在C波段的色散值进行补偿,最大残余色散绝对值仅为1.38ps/nm。与石英-空气孔微结构光纤相比,所提出的全固态色散补偿微结构光纤易制备且易与传统通信光纤熔接。     

新型全固态准晶体结构大模场光纤特性研究

大模场单模光纤在高功率激光器、高功率光传输和高灵敏度传感器等领域具有重要意义.设计了一种新型超低损耗大模场单模光纤,包层空气孔由掺氟硅玻璃棒代替,掺氟硅玻璃棒排列呈六重准晶体结构.基于有限元法对光纤的传输特性进行了数值模拟.研究了光纤结构参量变化对模式特性和有效模场面积的影响.结果表明:波长在1064 nm处,有效模场面积高达5197μm2,基模的限制性损耗低于10-5dB/km,解决了大模场与低损耗之间的冲突;在1064—2000 nm波段内,基模与二阶模的限制性损耗相差7个量级,实现单模传输;半径为10 cm时,弯曲损耗小于0.01 dB/m,具有良好的低弯曲损耗特性.此光纤能够提高光纤热损伤阈值,减少接续损耗,全固态结构有效避免了空气孔塌陷,简化制备工艺,对高功率激光传输、光纤激光器和光纤放大器的发展具有重要意义.     

空芯反谐振光纤与单模光纤的低损耗熔接研究

光子晶体光纤因具有设计自由、导光机制新颖等优势而被人们广泛关注。相比于带隙型光子晶体光纤和Kagome光纤,空芯反谐振光纤(HC-ARF)由于具有结构简单、单模导光、传输谱宽且损耗低的特点,在紫外/中红外光传输、高功率激光产生、非线性光学及传感等领域都具有很好的应用。但是HC-ARF要真正得到广泛应用,其与普通单模光纤的熔接必须简便且损耗低,然而,HC-ARF包层特殊的毛细管孔结构在熔接过程中容易坍塌,且其模场直径不同于普通单模光纤,故直接熔接时损耗很大。为此,引入一段纤芯直径为20μm的实芯大模场光纤作为模场过渡,实现了HC-ARF和普通单模光纤之间的熔接,熔接损耗由直接熔接的3dB降至0.844dB。     

光纤弯曲损耗特性的理论与实验研究

为了减小在长距离光纤通信中存在的弯曲损耗和利用光纤激光器中的弯曲损耗获得单模输出，利用速度法解释了光纤弯曲损耗机制，采用Marcuse理论研究了弯曲损耗随弯曲半径、波长和纤芯半径变化的关系。通过计算机仿真和实验得出弯曲损耗随弯曲半径的减小而增大，随波长的增大而增大，随纤芯半径的增大而增大，高阶模式的损耗大于低阶模式。利用这一结论就可以通过控制弯曲半径在临界半径以内来减小通信中的弯曲损耗，通过增大模场半径来实现光纤激光器中的单模输出。     

全固双层芯色散补偿光子晶体光纤的研究与设计

为了补偿光纤色散对高速信号传输的限制,提出一种全固双层芯色散补偿光子晶体光纤.首先对该光纤模式耦合特性进行理论分析,然后利用多极法进行模拟计算,得到该光纤包层结构参数与色散值以及相位匹配波长之间的关系,并对其规律进行研究.通过优化光纤结构参数,得到在1 550nm处,色散值达到-32 620ps/(nm·km)、损耗为0.29dB/km、与标准单模光纤的熔接损耗为4.77dB的色散补偿光纤.该光纤可补偿1 910多倍长度的SMF-28单模光纤的色散,补偿能力远大于常规色散补偿光纤.与空气孔-石英结构色散补偿光子晶体光纤相比,全固色散补偿光子晶体光纤具有易制备、易与传统通信光纤熔接等优点.     

Design and analysis of multi-ring microstructured-core optical fibers

A novel design of single-mode large-mode-area optical fiber is presented. The core is composed of alternate high and low-index regions to form an effectively low-index contrast between the core and the cladding. The proposed fiber is investigated by the finite-element method with anisotropic perfect matched layer boundary conditions. In addition, the bending losses of the fibers are calculated and compared with those of the step-index optical fibers. In particular, numerical simulations demonstrate that single-mode operation can be achieved in one such fiber with mode area larger than 600 μm² at the wavelength of 1.55 μm and bending loss lower than 0.02 dB/m for bending radius greater than 20 cm.     

Fabrication of low OH loss holey fibers with varying air hole sizes and their optical properties

We experimentally investigate a flexible fabrication technique for low OH and transmission losses holey fibers with a Ge-doped core and air holes in a silica cladding region. Versatile holey fibers of different size, pitch, and shape of air holes were achieved by controlling the temperature and heating time of the holey fiber preform. In addition, we suppress the OH loss of less than ∼0.323 dB/km at 1383 nm. After fabricating holey fibers, we measure their optical properties including cut-off wavelength, mode field diameter, splicing loss, dispersion, bending loss, and polarization dependent loss based on the size of air holes. The total transmission loss was measured to be ∼0.226 dB/km at 1550 nm by improving the fabrication process. After fabricating optical patch cord based on holey fibers, we measured the long-term stability of the fabricated holey fiber by using the temperature cycling technique for 24 and obtained low power fluctuation of 0.2 dB. We achieve the high quality holey fiber with a low bending loss of ∼0.04 dB/turn under a bending radius of 2.5 mm at 1550 nm. We also obtain a tunable band rejection filter with a number of bending turns.     

Single-mode microstructured optical fiber for the middle infrared

Microstructured crystalline optical fiber from silver halides is described. Both experimental and theoretical evidences are presented to establish that the fiber is effectively single mode at wavelength 10.6 micro m with numerical aperture NA=0.16 and optical losses of approximately 2 dB/m. Crystalline microstructured optical fibers offer key advantages over step-index optical fibers from silver halide crystals. The wide transmission range of wavelengths 2-20 micro m provides great potential for applications in spectroscopy and for the development of a range of new crystalline-based nonlinear optical fibers.     

Bending insensitivity of fiber Bragg gratings in suspended-core optical fibers

This Letter presents simulation and experimental results that explore bending insensitivity of fiber Bragg gratings in suspended-core optical fibers. The implementation of thin silica bridge in the fibers enhances index contrast of the fiber core and reduces bending-induced strain transfer to the fiber core. This fiber design lead to a reduction of over 7 times in strain-induced fiber Bragg grating resonant peak shifts in the suspended-core fiber compared with that in standard telecommunication fiber, and an 0.14 dB bending loss at a bending radius of 6.35 mm.     

Fiber devices using polarization- maintaining fibers

Fiber devices using polarization-maintaining fibers called PANDA fibers are presented. They are polarization-maintaining couplers and polarization-splitting couplers, optical isolators and optical circulators, and multi/demultiplexers designed for 1.3 μm wavelength. Crosstalk of-32 dB and excess loss of 0.03 dB for the polarization-maintaining coupler, and polarization-splitting ratio of 17 dB and excess loss of 0.5 dB for the polarization-splitting coupler have been fabricated by a fusion-elongation method. A fiber polarizer with the extinction ratio of more than 40 dB has been presented by using the difference of bending loss between the orthogonal modes in the PANDA fibers. Multi/demultiplexer with narrow band-pass of 1.4 nm utilizing combination of PANDA fiber polarization dispersion and the polarization-splitting coupler has been realized. An optical isolator consisting of fiber polarizers and a spherical YIG with a lens function and an optical circulator consisting of polarizing-splitting couplers and spherical YIGs have been achieved.     

Fiber devices using polarization- maintaining fibers

Fiber devices using polarization-maintaining fibers called PANDA fibers are presented. They are polarization-maintaining couplers and polarization-splitting couplers, optical isolators and optical circulators, and multi/demultiplexers designed for 1.3 μm wavelength. Crosstalk of-32 dB and excess loss of 0.03 dB for the polarization-maintaining coupler, and polarization-splitting ratio of 17 dB and excess loss of 0.5 dB for the polarization-splitting coupler have been fabricated by a fusion-elongation method. A fiber polarizer with the extinction ratio of more than 40 dB has been presented by using the difference of bending loss between the orthogonal modes in the PANDA fibers. Multi/demultiplexer with narrow band-pass of 1.4 nm utilizing combination of PANDA fiber polarization dispersion and the polarization-splitting coupler has been realized. An optical isolator consisting of fiber polarizers and a spherical YIG with a lens function and an optical circulator consisting of polarizing-splitting couplers and spherical YIGs have been achieved.     

Bending loss measurement using a fiber cavity ringdown scheme

A novel sensitive technique for the determination of losses in fiber cavities is presented. The method is based on the cavity ringdown scheme implemented in silica-based single-mode fibers. Bending losses of fiber cavities of different lengths have been measured showing all an oscillating behavior with respect to the curvature radius of the fiber as predicted by a theoretical model. The best minimum detectable absorbance per cavity pass achieved by this new method is 1.72×10⁻³ dB within a 10 m-long cavity. This limit suffices well for an accurate determination of optical bending losses even in bend-insensitive fibers. Furthermore, the comparison of the measured bending losses with a theoretical model allows the extraction of different fiber parameters. Good agreement has been found between the experimentally derived parameters and literature data.     

低损耗Ge-As-Se-Te硫系玻璃远红外光纤的性能分析

中、远红外光学领域的发展,离不开低损耗光波导材料的发展,因此近年来远红外低损耗光纤一直是光学领域的热点之一.本论文在国内首次报道了一种基于挤压法的低损耗远红外光纤制备技术,获得了具有完整结构的远红外光纤,其损耗为:0.46 d B/m@8.7μm,1.31 d B/m@10.6μm,整体低于1 dB/m@7.2—10.3μm.在实验过程中,首先采用传统的熔融淬冷法和蒸馏纯化工艺制备了Ge-As-Se-Te玻璃样品.利用X射线衍射仪和热膨胀仪等测试了玻璃的结构和物理性质,分析了Ge对玻璃热学性质的影响;利用分光光度计、红外光谱仪等研究了玻璃的光谱性质;综合比较了还原剂铝、镁的除氧效果.最后采用挤压法制备了芯包结构光纤.实验结果表明:镁的除氧效果佳,新型挤压制备工艺和有效提纯技术共同推进了硫系光纤损耗的降低,所获得的Ge-As-Se-Te光纤具有远红外广谱应用的潜能(其透光波长接近12μm).     

基于无芯光纤强度调制型液位传感器的设计与性能

利用强度调制型光纤传感器容易解调的优势,提出了一种强度调制型光纤液位传感器.传感器由三根无芯光纤组成,其中,无芯光纤1与无芯光纤2串联构成测量臂,无芯光纤3构成参考臂.仿真分析得出,无芯光纤长度每缩短1mm,透射峰波长增加25.46nm.在0~50mm小液位范围内,实验测得传感器在水、5%NaCl、10%NaCl和15%NaCl水溶液四种液体环境中的液位灵敏度分别为0.069 5dB/mm、0.074 73dB/mm、0.077 49dB/mm及0.082 71dB/mm,线性度分别为0.998 25、0.998 49、0.988 11及0.995 13,线性度较高.该传感器可较好地消除光源光功率波动与环境温度变化带来的影响,重复性较好,在石油化工领域有一定的应用潜力.     

Spliced-fiber mode filter for 1060-nm single-mode transmission

We present a novel mode filter operating for the 1060-nm band, which selectively removes the power of the high-order mode (HOM) from a conventional single-mode fiber (C-SMF) that supports two modes at the short-wavelength band. Our mode filter is fabricated very easily by fusion-splicing a short section of short-wavelength single-mode fiber in the middle of the C-SMF link. By using our spliced-fiber mode filter (SF-MF), a high HOM suppression performance of > 18 dB has been achieved with a low insertion loss of < 0.3 dB over the full band of optical communications from 1050 nm to 1650 nm. We have also developed a new mode power measurement scheme that takes advantage of the bending sensitivity of the HOM guidance. This measurement scheme enabled us to evaluate accurately the performance factors of the fabricated mode filter.