光纤耦合器的理论、设计及进展

系统总结了光纤耦合器的发展历程,归纳提炼出各个阶段的标志性事件;详细阐述了光纤耦合器的耦合类型、制作方法、性能参数;详细评述了光纤耦合器的理论分析方法;全面分析了X型、星型、光栅型、混合型等各种典型光纤耦合器的基本结构、工作原理及耦合特性;指出并展望了光纤耦合器的发展方向和应用前景。作者率先提出并设计了超长周期光纤光栅耦合器,实验上实现了两个超长周期光纤光栅之间的有效耦合。     

光纤耦合器的理论、设计及进展

系统总结了光纤耦合器的发展历程,归纳提炼出各个阶段的标志性事件;详细阐述了光纤耦合器的耦合类型、制作方法、性能参数;详细评述了光纤耦合器的理论分析方法;全面分析了X型、星型、光栅型、混合型等各种典型光纤耦合器的基本结构、工作原理及耦合特性;指出并展望了光纤耦合器的发展方向和应用前景。作者率先提出并设计了超长周期光纤光栅耦合器,实验上实现了两个超长周期光纤光栅之间的有效耦合。     

CO(2) laser writing of long-period fiber gratings in optical fibers under tension

We demonstrate experimentally that the efficiency of writing a long-period fiber grating in a single-mode fiber by CO(2) laser pulses increases significantly with the axial stress applied along the fiber. We attribute the enhancement in writing efficiency to the generation of nonuniform inelastic frozen-in strains across the fiber under tension by CO(2) laser heating. Controlling the axial stress distribution along a fiber during the CO(2) laser writing process thus provides an additional degree of freedom for control of the grating characteristics.     

Fiber optical parametric oscillator based on photonic crystal fiber pumped with all-normal-dispersion mode-locked Yb:fiber laser

We demonstrate a cost effective, linearly tunable fiber optical parametric oscillator based on a home-made photonic crystal fiber pumped with a mode-locked ytterbium-doped fiber laser, providing linely tuning ranges from 1018 nm to 1038 nm for the idler wavelength and from 1097 nm to 1117 nm for the signal wavelength by tuning the pump wavelength and the cavity length. In order to obtain the desired fiber with a zero dispersion wavelength around 1060 rim, eight sam- ples of photonic crystal fibers with gradually changed structural parameters are fabricated for the reason that it is difficult to accurately customize the structural dimensions during fabrication. We verify the usability of the fabricated fiber experimen- tally via optical parametric generation and conclude a successful procedure of design, fabirication, and verification. A seed source of home-made all-normal-dispersion mode-locked ytterbium-doped fiber laser with 38.57 ps pulsewidth around the 1064 nm wavelength is used to pump the fiber optical parametric oscillator. The wide picosecond pulse pump laser enables a larger walk-off tolerance between the pump light and the oscillating light as well as a longer photonic crystal fiber of 20 m superior to the femtosecond pulse lasers, resulting in a larger parametric amplification and a lower threshold pump power of 15.8 dBm of the fiber optical parametric oscillator.     

基于公共环形腔耦合的光纤激光器相干合成技术

为提高光纤激光器无源自调整相干合成阵列的效率、稳定性和可扩展性,提出了基于公共光纤环形腔耦合与单模光纤滤波的光纤激光器相干合成方案。将多个2×2的光纤耦合器分别插入各单元激光器的谐振腔,利用耦合器余下的端口,两两相连构成公共环形耦合腔。采用单模光纤滤波技术,提高了各输出激光束之间相位锁定的稳定性。利用该方案在实验上实现了三路光纤激光器的被动锁相输出,实验测得的远场干涉光斑、输出功率及光谱均表明该方案适于构建性能较好的光纤激光器相干合成阵列。     

Basic Spectroscopy Performance of Nd3+ and Rhodamine B Doped Polymer Fibers

The spectroscopy properties of Nd3+ doped polymer fiber with 532 nm pumping radiation is studied. It is found that the emission peak near 580 nm is attributed the transition from 2G7/2 and 4G5/2 to ground level 4I9/2,and the florescence intensity of Nd3+ doped polymer fiber with 70 ppm concentration and 650 μm cord diameter increases as the fiber is shortened from 89 cm to 15 cm and decreases again for further shortening to 8 cm. Both the advantages and disadvantages of Nd3+ doped polymer fiber compared with Rhodamine B doped polymer fiber are discussed.     

Basic Spectroscopy Performance of Nd~(3 ) and Rhodamine B Doped Polymer Fibers

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基于公共环形腔耦合的光纤激光器相干合成技术

 为提高光纤激光器无源自调整相干合成阵列的效率、稳定性和可扩展性,提出了基于公共光纤环形腔耦合与单模光纤滤波的光纤激光器相干合成方案。将多个2×2的光纤耦合器分别插入各单元激光器的谐振腔,利用耦合器余下的端口,两两相连构成公共环形耦合腔。采用单模光纤滤波技术,提高了各输出激光束之间相位锁定的稳定性。利用该方案在实验上实现了三路光纤激光器的被动锁相输出,实验测得的远场干涉光斑、输出功率及光谱均表明该方案适于构建性能较好的光纤激光器相干合成阵列。     

光谱法研究MC尼龙6/芳纶复合材料的结构

将经甲苯二异氰酸酯(TDI)和己内酰胺改性的Kevlar纤维作为MC尼龙6的增强体,X射线光电子能谱观察到改性后纤维表面C,N和O元素的含量发生了改变,谱峰也相应发生变化。从红外光谱分析发现,Kevlar纤维和MC尼龙6相混所得谱图只是二者红外谱图的简单叠加,而改性Kevlar纤维可作为己内酰胺阴离子开环聚合的活性中心,且接枝链上的酰胺基可以与基体尼龙形成较强的氢键,有利于提高界面结合。XRD测试表明Kevlar纤维的引入并没有明显改变MC尼龙6的晶型,但其晶粒将具有更严格的三维周期性结构。在相同纤维用量时,改性Kevlar纤维增强的MC尼龙6的晶粒较未改性纤维的完善。当纤维含量小于2%时,纤维的加入有利于生成完善的α球晶,纤维含量大于2%时,α球晶结构含量随着纤维用量的增多反而下降。     

2μm泵浦中红外硫化玻璃光纤拉曼激光器的理论分析与优化

根据2μm掺铥光纤激光泵浦中红外硫化玻璃光纤拉曼激光器的模型,采用非线性耦合方程组对激光器的性能进行了研究与分析。同时,对激光器各参数包括光纤长度、输出耦合器反射率、光纤散射损耗对激光器性能的影响进行了分析并给出了优化结果。数值仿真结果表明,在一定条件下,2μm泵浦硫化玻璃光纤产生拉曼激光的斜率效率可以超过85%。另外,光纤长度和输出耦合器反射率不仅对输出激光功率的影响很大,而且是相互影响的,必须同时进行优化。结果也表明,输出激光的功率随光纤散射损耗增加急剧线性下降。以上的结果可以用于硫化玻璃光纤级联拉曼激光器的实验指导和优化设计。     

Porous solgel fiber as a transducer for highly sensitive chemical sensing

A novel solgel process for making porous silica fiber and doping the fiber core with sensing material is described. A CoCl(2) -doped solgel fiber was fabricated and was used to construct an active-core optical fiber moisture sensor. Test results show that the sensitivity of the active-core optical fiber sensor is much higher than that of an evanescent-wave-based optical fiber sensor.     

光纤激光模场及表征技术进展

在光纤通信、光纤激光器和光纤传感等领域的实际应用中,需要重点关注光纤中的模式问题。模分复用是提高光通信信息容量的有效方法,模间干涉是大多数光纤传感的基本方法,高功率光纤激光的光束质量控制的关键技术之一就是模式控制,因此,对光纤模式理论、模式产生及转换、模式表征技术开展研究具有重要的研究意义和实际应用价值。论文讨论了光纤的模式及光束质量,分析了多种模式发生及转换的方法,将模式表征方法归结为非相干、相干和低相干测量法。光纤模式表征是目前的研究热点,在多种表征方法中,空间和频谱成像法（S²）和双重傅里叶变换法（F²）具有显著的优越性,可不需要提前知道光纤的几何参数,就可获得模场分布、模式功率占比、群时延等特性。研究表明F²法更适合于表征高功率光纤激光的模场特性。

     

Highly sensitive fiber refractive index sensor based on side-core holey structure

We propose a side-core holey fiber （SCHF）-based surface plasmon resonance （SPR） sensor to achieve high refractive index （RI） sensitivity. The SCHF structure can facilitate analyte filling and enhance the overlapping area of the core mode and surface plasmon polariton （SPP） mode. The coupling properties of the sensor are analyzed by numerical simulation. The maximum sensitivity of 5000 nm/RIU in an RI range of 1.33-1.44, and the average sensitivity of 9295 nm/RIU in an RI range from 1.44 to 1.54 can be obtained.     

大数值孔径多组分玻璃柔性光纤的制备及影响因素分析

大数值孔径多组分玻璃柔性光纤在医用光纤内窥镜中具有广阔的应用前景.采用La2O3 -Nb2O5 -SiO2-B2O3-RO玻璃系统作纤芯,用自制相匹配的低折射率玻璃材料作包层拉制的柔性光纤的数值孔径为0.8725,光的接受角为122°,扩大了医用光纤内窥镜的观察范围,满足了医疗仪器观察诊断的特殊需要.给出了La2O3 ...     

Hydrogen loading for fiber grating writing with a femtosecond laser and a phase mask

The threshold for the fabrication of fiber Bragg gratings with ultrafast 800-nm radiation and a phase mask was studied in SMF-28 and all-silica core fiber by use of 125-fs pulses. High-pressure molecular hydrogen loading (H2 loading) was observed to significantly lower the grating writing threshold in standard Ge-doped telecommunication fiber. No reduction was observed with all-silica core fiber. The index change appeared to be confined to the Ge-doped core region of the fiber. Gratings in H2-loaded SMF-28 had thermal annealing behavior similar to UV-induced gratings. Unlike UV-induced H2-loaded gratings, no absorption associated with Ge-OH defect formation was observed.     

Externally-modulated high-power fiber grating ring laser for digital transmission

We have constructed a low-cost, double-cavity erbium-doped fiber ring laser with a fiber Bragg grating and a 2×2 coupler. A high output power of 8.7 dBm and a signal-to-noise-floor ratio of 43 dB were demonstrated. This fiber grating ring laser is used as the light source for the 2.488 Gb/s transmission experiment through a 100 km single mode fiber. To our knowledge, this is the first time a fiber grating ring laser is being used as an externally modulated source for digital transmission.     

Submicrometer organic silica gel fiber for oxygen sensing

We introduce the electrospinning method into fabricating oxygen-sensitive submicrometer scale optical fiber. Uniform tris (4,7-diphenyl-1,10-phenathroline) ruthenium(II) dichloride ([Ru(dpp)(3)](2+)Cl(2))-doped fibers with a diameter of 900 nm are obtained by electrospinning the organic silicon sol solution derived from tetraethyl orthosilicate and n-Octyltriethoxysilane (C(14)H(32)O(3)Si). The experimental results show that the single gel fiber exhibits excellent optical and sensing properties. A laser with a wavelength of 452 nm can be efficiently launched into the fiber and guide along the fiber to excite the fluorescence. Then, we find that [Ru(dpp)(3)](2+)-gel fiber has favorable optical and sensing characteristics, and the Stern-Volmer plots are linear in the full concentration range of O(2) (0-100 vol.?%). The ratio of I(0)/I(100), where I(0) and I(100) respectively represent the fluorescence intensities of the fiber exposed to 100% N(2) and 100% O(2), as the sensitivity of the fiber is 3.5. Simultaneously, the fiber can make a quick response within 100 ms. This method provides an effective and convenient way to fabricate highly uniform nanoscale or microscale optical waveguides for photonic devices.     

Optical Measurement Techniques for Optical Fiber and Waveguide Devices

We describe three major optical characterization methods for fiber and fiber devices. A simple servo controlled scanning fiber-optic confocal microscope is proposed for determining the refractive index profile of an optical fiber. To measure the chromatic dispersion of a short length fiber a Mach-Zehnder fiber interferometer with a novel interferometric distance meter is introduced. At the end, a tomographic method is demonstrated for determining the 2-D stress profile of a fiber.     

双端泵浦保偏光纤激光器

 以两台808 nm半导体激光器LD1和LD2为泵浦源,对光纤激光器双端泵浦进行了研究,获得了6.5 W的激光输出。实验分别测出了LD1和LD2半导体激光器单端泵浦和双端泵浦时的输出功率,对双端泵浦输出功率与单端泵浦功率之和进行了比较,利用双端泵浦提高了泵浦效率和输出激光功率。同时测量了输出激光的偏振度,通过计算得到双端泵浦输出激光的偏振度为0.5。     

双端泵浦保偏光纤激光器

以两台808 nm半导体激光器LD1和LD2为泵浦源,对光纤激光器双端泵浦进行了研究,获得了6.5 W的激光输出。实验分别测出了LD1和LD2半导体激光器单端泵浦和双端泵浦时的输出功率,对双端泵浦输出功率与单端泵浦功率之和进行了比较,利用双端泵浦提高了泵浦效率和输出激光功率。同时测量了输出激光的偏振度,通过计算得到双端泵浦输出激光的偏振度为0.5。