基于光纤布拉格光栅的温度应变复合测量系统

本文基于光纤布拉格光栅(fiber Bragg grating,FBG)传感原理和可调谐滤波器解调技术设计了一套可用于工程中温度和应变监测的复合测量系统.对系统进行模块化设计,可根据应用实际情况配置各个模块,能够实现14通道同步并行测量,每通道最多可负载16支FBG传感器,即最多能实现224个待测点的实时同步测量.针对可调谐滤波器输出波长的非线性漂移问题,提出了可调谐滤波器的自适应驱动算法,波长拟合残差小于1 pm,确保系统的测量精度.系统的温度测量精度小于±0.5℃,稳定性良好.将本文系统应用于混凝土监测领域,测量结果验证了其可行性,可以满足实际工程应用的需要.     

基于FBG的输电线路温度解调系统

温度监测是输电线路覆冰监测中的重要组成部分。本文研制出基于单片机的低成本高分辨率高精度光纤Bragg光栅(FBG)温度解调系统。该系统利用可调谐F-P滤波器法对温度传感器反射光谱进行波长解调。为降低F-P腔腔长漂移和压电陶瓷非线性的影响,采用3根FBG作为参考光纤光栅,对波长-温度曲线进行二次拟合求解。试验结果表明,该解调系统分辨率达1.4pm,精度达1.2℃,具有广泛实用性。     

Agilent VEE光纤布拉格光栅波长测试系统

为准确测量光纤布拉格光栅的中心波长,基于Agilent VEE开发环境研制一套自动测试系统,利用可调谐激光器输出光波长精度和信噪比高的特点,通过在光功率计的不同量程档上分别进行波长扫描,并对扫描数据进行融合,系统的测量准确度达到了皮米量级,动态范围达到70 d B以上。在得到光纤布拉格光栅反射光谱曲线的基础上,应用三次样条插值和四次多项式拟合的方法来计算中心波长。测试结果表明:系统的测量重复性优于0.5 pm,测量不确定度为6 pm(k=2),能够满足传感用光纤布拉格光栅的测试需求。     

用于光纤光栅解调仪表的SGDBR光源研究

取样光栅分布布拉格反射型(Sampled Grating Distributed Bragg Reflector,SGDBR)光源是一种电流驱动的波长可调谐激光光源。本文介绍了该光源的原理特性,通过搭建自动标定系统确立该光源驱动电流组合和输出光波长的对应关系,再将此对应关系用于电路设计中,并对该光源输出的光谱参数进行了实验验证,得到一种可用于光纤光栅解调仪表中的低成本波长扫描光源。     

基于可调光纤F—P滤波器解调的分布式光纤光栅传感系统

提出并实现了一种可满足工程实用要求的波分复用光纤光栅传感网络解决方案，系统通过可调谐光纤F-P滤波器的连续扫描实现波长信号的解调，该传感系统扫描带宽50nm，单点工作带宽5nm，对一般应用系统每根单纤可设20-30个点，系统最高扫描频率200Hz，分辨率5pm(约5με或0．5℃)。     

边带峰值反射率拟合的光栅特征提取技术

针对高精度测量的要求,探索性地提出了一种多峰值反射率拟合的解调新方法。讨论了Levenberg-Marquardt算法在边波带峰值反射率拟合中的应用。根据光纤布拉格光栅对多波长光源的反射作用,研究光栅反射中心波长与各阶光边波带峰值反射率之间的关系模型,利用Lebenberg-Marquardt算法对光栅反射光谱进行特征提取得到特征参量表征传感信息。初步实验证明了该高精度解调方案的有效性和可行性,并分别获得了0.1℃的温度分辨率和0.5的应变分辨率,对高精度光栅传感系统的研制具有一定的供参考价值。     

光纤布拉格光栅型色散补偿模块的校准方法研究

基于相移法和微分相移法的传统色散校准方法无法满足梳状谱条件下的光纤布拉格光栅(FBG)型色散补偿模块的校准需求,提出了针对FBG型色散补偿模块的校准方法,将色散校准系统中的宽带光源用高波长分辨力、高输出功率的可调谐光源替代,通过波长的连续扫描实现窄波长范围的色散测试与量值溯源,并且借助可调谐光源的高功率和信噪比性能显著提高了色散测试的动态范围。     

天津大学光纤传感技术研究部分最新进展

本文介绍了天津大学在光纤传感技术研究领域的最新进展.主要为:基于白光干涉实现了非本征光纤法珀和FBG并行解调,法珀腔长测量误差0.81 μm,FBG波长测量误差14 pm;基于光纤有源内腔结构夹现了乙炔气体传感,灵敏度优于100ppm;基于保偏光纤实现了分布式传感,灵敏度可达6 cm;基于边缘滤波器开发了光纤光栅解调仪,波长分辨力可达1.2pm,扫描速率超过200kHz;采用全光纤OCT技术实现了牙齿模型的二维、三维扫描;实现了光纤陀螺光纤环的温度、振动等动态特性检测.     

光纤光栅应用于梳状滤波器和光分插复用器(OADM)的研究

研究了光纤光栅在梳状滤波器和光分插复用器(OADM)中的应用特性。基于传输矩阵法对Sinc取样光栅反射谱进行分析,分析了取样光栅长度、折射率调制深度和取样周期等光栅参数对Sinc取样光栅反射谱的影响规律。根据各参数对Sinc取样光栅反射谱的影响规律构造了4种反射率高、反射峰间隔均匀及谱宽稳定的Sinc取样光栅梳状滤波器,为梳状滤波器的设计与制作提供了新思路、新技术。用OptiSystem软件对光纤Bragg光栅型光分插复用器进行了仿真研究。研究表明,经过光纤光栅光分插复用器后,下载和除了下载的光谱峰值基本为-4dBm,下载的功率也基本是均衡的。     

基于长信号谱自相关的光纤光栅传感解调方法

针对光纤光栅传感领域波长高精度探测和传感复用光栅数量增多的需要,提出一种基于长信号相关谱的新型光纤光栅数字解调技术.该技术在可调谐滤波法的基础上,通过传感光栅与调制光栅反射谱卷积后的信号,即光电探测器的光强时间信号,进行自相关分析以实现对波长漂移的测量以及对传感光栅反射谱形状的识别,增强系统的复用能力,提高了性价比.模拟仿真表明,光纤光栅长信号相关数字解调方法可以准确测量光纤光栅波长的漂移,能更好实现传感复用.等强度悬臂梁实验验证该解调方法能实现光栅应变的高精度测量,优于传统的应变片测试.     

光栅投影轮廓术的精度分析及应用

介绍了彩色面结构光栅投影轮廓术的基本原理,该原理在投影光栅方面采用正弦编码的投影光栅,这样可以采用快速的直接光栅条纹解调的方法,实现了对被测物体单视角数据的测量,并对标准台阶进行了测量.分析了测量过程中存在的误差及其产生的原因;并针对各种误差提出了相应的改进或克服方法;最后,使用该方法对具有复杂自由曲面的脚型进行了测量,实验结果表明:该方法能够快速,准确地获取被测物体的三维数据.     

Electromagnetic forces in the vacuum region of laser-driven layered grating structures

Symmetric multilayer grating structures that have an embedded vacuum channel and that are powered by external laser beams are analyzed for their ability to manipulate charged particle beams. It is shown that acceleration, deflection and focusing forces can all be generated in a controlled fashion from the same grating architecture and by adjustment of phase of the incoming laser beams     

Demonstration of chirped-pulse compression with an object-image-grating self-tiling grating compressor

The capability of chirped-pulse compression and beam focusing of an object-image-grating self-tiling grating compressor is demonstrated in an optical parametric chirped-pulse amplification laser for the first time. Probe lasers for tiling error adjustments, which are generally required by the traditional tiled-grating compressor, are not needed in our demonstration any more. With the aid of the double-sized effective optical aperture of the second grating in the compressor, a 490?fs near-transform-limit pulse duration and a 90?μm near-diffraction-limit focal spot are obtained, synchronously, which are very close to the ones achieved by a non-tiled grating compressor with equal-sized individual gratings.     

Fabrication of holographic blazed grating with Fourier synthesis exposure

A simple, direct, and universal fabrication method for holographic blazed gratings is proposed and a 79 lines/mm holographic echelle grating with 4 μm depth quasi-triangular grooves experimentally demonstrated as an example of a blazed grating fabricated directly by Fourier synthesis exposure. With the method, we converted a periodic grating groove profile into the exposure energy spatial distribution on the surface of a photoresist with the response characteristics of the particular photoresist. Then the exposure energy could be decomposed into a series of sinusoidal functions using Fourier series, and realized by superposing a series of two-beam interference patterns. In contrast with mechanically ruled gratings, the fabrication process of holographic gratings is quite quick and low cost, and especially no Rowland ghosts appear in their dispersion spectrum. The reported work will offer a new approach for blazed grating fabrication with a holographic process.     

线性啁啾相位掩模的设计

啁啾相位掩模法是啁啾光纤光栅的一种非常重要的制作方法。本文研究讨论了用全息干涉方法制作线性啁啾位相掩模的设计方法,提出用两球面波干涉产生条纹密度随空间距离线性变化的干涉条纹记录啁啾位相光栅,按设定光栅端点空频和端点空频差两种优化设计方法设计了长度100mm、啁啾量1nm/mm的线性啁啾光栅,理论和实验结果给出两种设计方案的非线性系数分别为2.5%和1.6%,理论设计和实验结果相符。     

光刻法制备聚合物/液晶光栅

将明胶涂覆在表面经过取向处理的带有ITO电极的玻璃基板上，以紫外灯为光源，通过光掩模法，使明胶在光场的引发下发生光化学反应，样品显影刻蚀处理后呈栅状，将液晶注入光栅盒中，形成聚合物／液晶光栅。该光栅衍射效率可利用电场调控。采用He—Ne激光器对所制样品进行测试，结果表明，所制样品的栅结构较好。避免了液晶与聚合物相分离的不完全性和栅条边缘不整齐的现象。制得的光栅其第一衍射级次的开关比为87：1，显示了较好的开关能力。     

Design and characteristics of polarization-insensitive resonant gratings for color filtering

A method of designing polarization-insensitive color filters with guided-mode resonance grating is presented. The influence of incident conditions on exciting waveguide mode is investigated, and we find that polarization insensitivity may occur at the full conical incidence. Using rigorous coupled-wave analysis, we mainly analyze the effects of waveguide thickness and fill factor on the diffracted efficiency of the grating filter. The final structural parameters of the devices for three primary colors are collected after optimization, and the calculated results show that the spectral reflectance of each color filter is basically identical for different polarization states of incident light. Moreover, field analysis by the finite-difference time-domain technique indicates that two symmetric modes are excited between the waveguide layer and substrate under full conical incidence, which is coincident with the previous theoretical study. The reported work will eliminate the restriction of polarization-dependence of color filters and greatly expand their application range.     

基于网点透射机理的印刷网线尺评价研究

印刷行业目前还主要依靠经验进行印刷品加网线数和加网角度的识别。 根据莫尔条纹原理,通过设置合理的印刷加网线数、加网角度、激光照排机输出点数,设计了评价图像质量的印刷网线尺。 主要对前期设计的网线尺进行数学公式的推导,对印刷品加网线数和加网角度测试提供充分理论依据。     

Effects of fibre grating parameters on the spectral characteristics of cascaded long- and short-period gratings

Using coupled-mode theory combined with the transfer matrix method, this paper presents the impact of fibre grating parameters(grating period, grating length and average index modulation) and the separation between long-period fibre grating and fibre Bragg grating (FBG) on the reflection spectra of cascaded long-and short-period grating (CLBG). Two grating periods and two grating lengths have only impact on the two reflection peaks. The two resonance wavelengths shift towards the longer wavelength when the period of FBG decreases. Further, we study the sensing characteristics of coated CLBG. By analysing the relationship between the refractive index sensitivity and the thin film parameters (film refractive index and film thickness), the optimized parameters for the coated CLBG used as film sensor were obtained. Data simulation shows that the resolution of the refractive index of this coated CLBG film sensor is predicted to be 10^?6. This implies that the coated CLBG has an important application value in sensing and measurement field.     

新型金属编码器的三个关键问题

金属光栅编码器可以在恶劣环境条件下有效而稳定地工作.本文介绍了一种新的基于不同反射层反射率差形成莫尔条纹的原理的反射式金属光栅.反射式金属光栅光栅盘基材与光栅盘加工及光栅信号的提取,与传统玻璃光栅盘有很大区别.因此,反射式金属光栅编码器的制作有较高的难度.我们通过采用新的工艺方法来制作金属栅编码器,主要解决了光栅制作、信号提取和光电信号处理这三个关键问题.