光纤Bragg光栅应变测量中啁啾特性的研究

用光纤Bragg光栅进行应变（静态、动态）测量时，由于光栅轴向各部分受到的应变不同，因而产生布喇格中心波长漂移量发生变化.实际测量中往往忽略此扰动对光纤光栅反射谱中心波长的影响，则必然带来测量误差.采用耦合模理论，分析并研究了Bragg光栅受轴向线性应变、高次应变和非线性周期应变波等情况下的啁啾特性.根据各自啁啾特性的不同，给出了对光纤光栅反射谱中心的影响，以及测量各种应变时的测量条件和范围.     

光纤光栅横向效应在平面应变测量中的应用

对光纤光栅的横向效应进行了理论分析，并通过实验对其进行了测量。分析表明其产生的原因是光纤纤芯的直径变化及光纤有效折射率随纤芯直径的变化率。通过平面应变模型，分析了在平面应变状态下光纤光栅的应变测量方法。针对光纤光栅横向效应带来的测量误差，以及单个光栅无法测量二维平面应变的不足，提出了一种采用铝合金材料对两根FBG进行十字型封装的新型结构，从理论上消除了光纤光栅横向效应带来的测量误差。     

光纤光栅传感器交叉敏感问题研究

交叉敏感问题是光纤光栅传感器在实际应用中需面对的一个关键问题。从光纤Bragg光栅的传感理论出发，分析了光纤光栅在同时测量应变和温度时引起交叉敏感的物理机理，建立了带有温度-应变交叉灵敏度系数的光纤Bragg光栅反射波长方程。利用双波长矩阵算法针对上述建立的光纤光栅方程进行了误差分析，获取了在交叉敏感情况下温度和应变的相对误差曲线图。结合相对误差表达式和曲线图分析讨论了交叉敏感对测量带来的影响。结果表明在温度和应力测量中随着测量温度或者应变变化量的增大，忽略交叉敏感项而带来的测量误差越来越明显。     

基于模场自积增强检测的光纤声光旋转传感器

介绍了一种应变不敏感的基于模场自积增强检测的光纤声光旋转传感器.通过调节加载到光纤声致光栅上的微波频率能使双模光纤输出高纯度LP_(11)模式.采用自积增强算法显著提高传感分辨比例,改善探测速度,实现对环境旋转角度变化的动态监测.传感器在0°—180°的测量范围内,角度最大测量误差范围小于11%;在轴向应变为100—1500με之间对应变不敏感.     

纤维光学 光纤参数测试

TN252006054333光纤Bragg光栅应变测量中啁啾特性的研究=Study onchirp characteristic in strain measurement by fiber Bragggrating[刊,中]/童凯(燕山大学电气工程学院.河北,秦皇岛(066004)),李志全…//光子学报.—2006,35(6).—877-880用光纤Bragg光栅进行应变(静态、动态)测量时,由于光栅轴向各部分受到的应变不同,因而产生布喇格中心波长漂移量发生变化。实际测量中往往忽略此扰动对光纤光栅反射谱中心波长的影响,因此必然带来测量误差。采用耦合模理论,分析并研究了Bragg光栅受轴向线性应变、高次应变和非线性周期应变波等情况下…     

一种新型双参量光纤布喇格光栅传感器的研制

介绍了一种新型的具有双参量测量功能的光纤布喇格光栅传感器.该传感器采用了特殊的结构,安装了两个不同中心波长的光纤布喇格光栅,可以实现两曲面之间狭小间隙的微小位移和温度的同时测量.实验表明,该传感器结构紧凑、体积小,具有良好的重复性和稳定性,位移测量误差不超过±10 μm,温度测量误差不超过±2℃.     

基于监测波峰绝对积分的双折射光子晶体光纤环镜轴向应变传感器研究

理论推导了双折射光纤环镜波长变化与轴向应变的公式,研究表明：双折射光子晶体光纤环镜轴向应变灵敏度比传统双折射光纤环镜大为减小。通过监测双折射光子晶体光纤环镜波长的变化,来实现轴向应变的测量就变得较为困难;且输出干涉光谱局部呈凹凸不平,波长监测容易导致数据测量误差。实验监测双折射光子晶体光纤环镜应变光谱,对应变光谱分析发现：随着应变增加,监测波峰下的绝对积分呈现减小的趋势。进一步精确计算分析发现：监测波峰下的绝对积分与应变成线性关系。基于此,提出了通过监测波峰下的绝对积分的变化,来实现轴向应变的测量。波峰下的绝对积分是表征各波长光强的综合性能指标,通过监测波峰下的绝对积分的变化,来实现轴向应变的测量,不仅可以克服双折射光子晶体光纤环镜监测波长变化的困难,而且还可以克服波长监测局部寻优导致的测量误差。     

光源镰 对光纤法布里—珀罗应变传感系统的影响

从多光束干涉的基本原理出发，分析了光源光谱对光纤光布里－珀罗应变传感系统的影响。通过分析发现光源光谱的高斯分布会使光纤法布里－珀罗应变传感系统产生测量误差，并从理论上推导出了这种误差的计算公式；通过计算机仿真发现光源的影响使应变测量结果出现了连续周期性和跳变，并通过实验验证了这种变化规律。     

线性滤波法高速解调技术中的测量有效性研究

光纤光栅在不均匀应变场中会由于其反射谱的展宽而带来测量误差.线性滤波法是一种适合于高频瞬变信号的解调方法, 在光纤光栅参数取典型值时, 使用传输矩阵法对线性滤波法解调光纤光栅在不均匀应变场中反射谱的过程进行了数值模拟.模拟结果表明, 固定应变峰值为3000 με, 应变波波长大于0.0025 m时, 测量相对误差不超过3 %;固定应变波长0.05 m, 应变波幅值小于10000 με时, 应变误差不超过0.25 %.使用Hopkinson压杆装置对数值模拟结果进行了验证, 结果与数值分析结论较为吻合.     

非轴向力下埋入式光纤传感器应变传递分析

利用剪滞法建立了当光纤光栅传感器的轴线和基体主应力的方向成一定角度时,光纤光栅传感器的测量应变与基体结构实际应变之间的关系,进而得出了光纤光栅传感器的平均应变传递率的一般公式。采用裸光纤光栅传感器进行实验,在倾斜角度α为30.72°时,实验所得的波长变化之比分别为:0.727,0.738,0.746;理论计算所得的波长变化之比为0.739,相对误差都在2%以内。同时分析了埋设角度偏差对测量结果的影响。研究结果表明,非轴向力作用下光纤光栅传感器的应变与结构基体应变之间的传递关系与其在轴向力作用下存在明显的区别,埋设角度的偏差会给测量结果造成一定的误差。     

直升机旋翼桨叶气动力学参数飞行测试系统

根据某型号直升机定型试飞的需要,研制出了动态测量旋翼桨叶气动力学参数的光电测试系统。其中运动参数(挥舞角、摆振角和变距角)由二维位置敏感传感器响应桨叶表贴发光点的位置变化测得,挥舞应变由光纤光栅传感器测得。利用自主搭建的桨叶运动姿态仿真平台开展了相关测试实验。结果表明:各角度值与对应输出电压间有很好的线性关系,测量范围内的角度测量误差小于1%;光纤光栅与电阻应变片对比测试的一致性较好,线性相关系数达到了0.999;光纤光栅应变测量的复现性很好,两次应变测量的相对偏差仅为1.22%。系统具有较高的测试精度。     

D形光纤Bragg光栅弯曲灵敏度的理论和实验研究

用材料力学理论分析了D形光纤Bragg光栅（D-shaped fiber Bragg grating,D-FBG）以及常规光纤Bragg光栅由弯曲引起的轴向应变,得到了光栅Bragg波长漂移的弯曲敏感特性.实验结果和理论计算结果基本相符.与常规FBG相比,该D-FBG的弯曲灵敏度要高近80倍.因此D-FBG可以直接应用于弯曲形变的测量,以及间接应用于压力、加速度等物理量的测量.理论分析和实验结果对采用该类型光纤光栅的器件和传感系统的设计具有参考意义.     

Determination of engineering strain distribution in a rotor blade with fibre Bragg grating array and a rotary optic coupler

Structural damage occurs in materials subjected to repeated or fluctuating stresses that must be minimized by design to increase fatigue life, and strains distributed in a blade need to be experimentally determined for evaluating stress levels. In order to measure local strains in a rotating blade, efficient signal transmission between a sensor installed on a blade and a stationary interrogator is significantly important. In this paper a strain-independent fibre Bragg grating (FBG) sensor and a rotary optic coupler were used as means of compensating light intensity loss change arising from blade rotation. Working principles of a FBG sensor and a rotary optic coupler were detailed, and procedures for measuring local strains were also described. Eventually, strain distributions were obtained in terms of mean strain and strain amplitude. Measured strains were then directly compared with analytical ones. Experimental procedures and results offer an improved insight into a strain measurement technique for a rotating mechanical system.     

基于光栅应变传感器的纳米测量机探针设计

为了提高纳米坐标测量机探针的测量精度,且能满足对复杂曲面或微结构进行精确测量的要求,提出了一种新颖的基于微探针系统的光纤布拉格光栅(FBG)探针。该探针具有较高灵敏度和可重复性。提出该新型FBG探针,即探针里有一个熔融的球形顶端,FBG作为应变传感器内置在测杆上。介绍了光纤探针的基本原理,并利用有限元软件ANSYS 11对探针的应变分布在轴向和横向载荷两种典型配置分别进行了仿真分析,结果表明仿真分析和理论计算相吻合。通过实验对光纤探针的灵敏度和分辨率分别进行测试。实验结果表明,在轴向载荷条件下,用位移分辨率为1.5 nm的压电换能器对探针进行性能测试,得到光纤探针的测量分辨率为60 nm。即光纤探针具有较高的灵敏度和分辨率,其性能满足实际测量需要。     

基于光纤光栅技术的船体横扭角测量方法研究

简要介绍了常见的船体横扭角测量方法,与传统的船体横扭角测量方法相比,光栅技术具有精度高、体积小、测量通道多等优势。建立了从应变量到横扭角的转换模型,设计并完成了与测量船现有变形测量系统的对比测量试验。试验结果表明:在较短测量时段内光栅测量数据与现有船载变形测量系统的测量数据吻合度高,误差在5″范围内,满足船体变形测量的要求;在长时间测量过程中,外界振动干扰对测量结果影响显著。     

Single-mode fibre optic Bragg grating sensing on the base of birefringence in surface-mounting and embedding applications

Birefringence effects in the two typical installation techniques of fibre Bragg grating(FBG) sensor are investigated: surface-mounting and embedding configurations. When the FBG is bonded on a host material, the sensitivity loss in ultrasonic measurement caused by glue-induced low-birefringence is first reported. Next, the transverse stress-induced high birefringence when the FBG is embedded into a fabric composite laminate is measured as 3.6×10⁻⁴. Such induced-birefringence effects are experimentally analysed in mechanical applications. Simple and effective solutions with respect to the respective installation configurations for removing the birefringence effect are proposed and the obtained zero-birefringence cases are compared with the birefringent cases.     

光纤光栅传感器的波长检测系统及其理论分析

理论分析并实验研究了基于光纤光栅滤波调谐技术的光纤光栅传感系统。分析了由于光源光强度波动及光纤扰动而引起的波长测量误差，并给出了减小测量误差的方法。该系统采用应变仪作为读出设备，使测量结果的线性拟合度达0．9995，测量光纤光栅布拉格波长移动的最小分辨率为1．3pm。     

Characteristics of strain transfer and the reflected spectrum of a metal-coated fiber Bragg grating sensor

Previous researchers have simulated strain transfer and spectrum of normal fiber Bragg grating (FBG) sensors with a polymer coating bonded on the structure. They only considered the shear stress in a polymer coating for the simulation. However, for metal-coated FBG sensors, not only shear stress but also axial stress in the metal coating should be reflected into the calculation because its axial stiffness is no longer negligible. Thus, the author investigated the strain transfer and reflected spectra of metal-coated FBG sensors by considering both shear stress and axial stress. The strain transfer analysis involved evaluating the strain profiles along the sensor by plotting an analytical solution, and validating the evaluated profiles with the results obtained by a finite element analysis (FEA). The solution was also verified by the experiments that used aluminum-coated FBG sensors bonded on a carbon fiber reinforced polymer (CFRP) composite specimen. A transfer-matrix (T-matrix) formulation and coupled mode theory were used to simulate the reflected spectra of metal-coated FBG sensors for the evaluated strain profile. In addition, the effect of mechanical and geometric parameters of the sensor was examined. The findings revealed that the strain transfer characteristics and reflected spectra deteriorated with increases in the thickness and Young's modulus of the metal coating due to the consideration of axial stress. It is the opposite results for the normal FBG sensor with a polymer coating. Furthermore, the results also indicated that the decrease in bonding thickness resulted in improved strain transfer and signal characteristics. Moreover, a bonding length of 14 mm was suitable in suppressing an asymmetric shape of the reflected spectrum and in achieving an accurate measurement. The results of the parametric study are expected to contribute to improve the measurement accuracy of metal-coated FBG sensors in actual applications. The analytical methodology can be usefully employed in the design of a metal-coated FBG sensor system.