碳涂覆光纤表面碳膜形成机理研究

通过分析碳涂覆光纤的测试结果，研究碳涂覆光纤碳膜的形成机理，并应用该机理解释涂覆光纤的高可靠性问题和影响光纤初始强度大小的因素。     

一种碳涂覆光纤碳膜厚度在线控制技术

为了控制长长度碳涂覆光纤和对光纤碳膜厚度进行了在线监控,开发了一种碳涂覆光纤碳膜厚度在线监控技术。试验结果表明,这种技术是行之有效的。     

碳涂覆光纤的最新进展

本文首先介绍了气密性光纤的发展过程，接着重点分析了碳涂覆光纤的两个重要参数：长期可靠性和抗氢渗透性。引入了新的衡量碳涂覆光纤抗氢渗参量－缺氢渗因子，最后介绍了西安应用光学研究所碳涂覆光纤“八．五”末的进展情况，以及国内外现状比较。     

双涂层光纤应变传感器的理论与实验研究

对带有聚合物涂敷层和缓冲层的光纤应变传感器的力学特性进行了研究，建立了双涂层光纤与基体材料相互作用的线弹性理论模型.理论研究表明：在小半径近似条件下，双涂层光纤的力学传递特性决定于涂覆层和缓冲层的弹性模量的相对值；当缓冲层的弹性模量远大于涂覆层时，其作用可忽略.实验中，将光纤传感器埋入基体材料内部，利用白光干涉应变测量方法，对平均应变传递系数进行了实验研究.实验结果与理论仿真具有较好的一致性.     

一种特殊截止单模光纤的传输性能研究

为了提高特殊截止单模光纤的弯曲可靠性,采用气相沉积工艺制作了包层直径80μm碳涂覆的特殊截止单模光纤,测试了光纤的截止波长、模场、衰减谱、宏弯、色散等传输性能和应力腐蚀敏感性参数。测试结果表明光纤截止波长小于915nm,能够实现915nm以上波长单模工作,在常用的几个波段具有较低的传输损耗,光纤的零色散波长红移到1 670nm。采用碳涂覆工艺提高光纤的应力腐蚀敏感性参数达到35,结合小包层直径预期可以提高光纤的使用寿命。     

制导光纤强度的依赖关系

分析研究制导高强度光纤强度8个方面的依赖关系，指出光纤强度降低的关键原因是光纤中存在着缺陷即表面微裂纹。因此，必须从制造工艺、制造环境入手，严格控制减少微裂纹方能制造出过2％筛选应变的高强度光纤。     

一种简易的光纤光栅涂覆装置

阐述了对裸光纤光栅进行涂覆的原理和必要性。设计了一种简易可行的光纤光栅涂覆装置。该装置简单灵活,成本较低,尤其适合于长度较长的光纤光栅的一次性涂覆,涂层厚度灵活可调。以啁啾光纤光栅为例进行了涂覆实验,涂层光滑均匀,涂覆后的光栅强度得到了增强,抵抗机械应力的能力得到了提高,使用起来更方便。对光栅在涂覆前后分别作了特性参数测试。结果表明,光栅特性基本上不发生变化,性能未劣化,光纤光栅的涂覆简单易行。     

光纤型热光可调光衰减器的设计及其衰减分析

提出了一种基于热光调节的可调光衰减器结构。该衰减器通过腐蚀光纤包层到一定厚度和长度后,在表面涂覆较大热光系数的聚合物材料得到。从模场变化角度分析了传输光束的衰减与涂覆材料折射率的关系,并从实验上测试了使用不同涂覆材料时的衰减。理论分析与实验结果均表明在涂覆材料折射率略大于原光纤包层材料折射率时,涂覆材料折射率微小的变化将引起传播光束衰减的大幅度变化,并且光纤被腐蚀的长度越长或包层材料剩余厚度越小,衰减越大。因此,由热光系数大、折射率略大于光纤包层的聚合物材料所组成的可调光纤衰减器,具有衰减调节范围大且功耗小、插入损耗小、成本低、低偏振特性、易于与其它光纤器件耦合或集成等特点。     

纤维光学 其他

TN25 2005042865 光纤-混凝土复合体三维非线性有限元分析=3-D nonlin- ear finite element analysis of fiber-concrete complex[刊, 中]／丁睿(四川大学水电学院,四川,成都(610065)),刘浩吾…／／光电子·激光,-2004,15(12),-1467-1471 对光纤-混凝土间的微观力学行为进行了分析。考虑了双接触面摩擦接触,通过试验确定了接触面力学参数; 对光纤-混凝土复合体进行了三维非线性数值分析,得出光纤-混凝土复合体不同受载状况下微观应力应变分布状态及其接触面滑移状态,从理论上验证了光纤涂覆层对其传感灵敏度的影响及光纤布置方式的选择。图7表1参 10(严寒)     

聚酰亚胺涂覆的光纤宏弯温度传感器

为了提高光纤宏弯温度传感器的性能,提出了一种基于聚酰亚胺(PI)涂覆的新颖光纤宏弯温度传感器。利用基于纤芯-包层-无限涂覆层结构的光纤弯曲损耗-温度测量方法确定了传感器的光纤弯曲半径,将PI薄膜涂覆在1060-XP光纤包层外获得了新型的光纤宏弯温度传感器。该传感器的温度传感实验结果表明,PI涂覆不仅能提升光纤的机械性能和耐热性,还可实现温度灵敏度和温度测量分辨能力的显著提高。该新颖的光纤宏弯温度传感器可实现-20～100℃的宽温测量范围,温度灵敏度为0.072 dB/℃,分辨能力为0.14℃。与其他光纤宏弯温度传感器相比,所设计的传感器的温度传感性能显著提高。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.