Highly sensitive twist sensor based on tilted fiber Bragg grating of polarization-dependent properties

The transmission intensity of the tilted fiber Bragg grating (TFBG) is strongly dependent on the polarization properties of the TFBG. The polarization characteristic of the cladding modes can be used for twist measuring. In this paper, a highly sensitive fiber twist sensor is proposed. The transmission intensity on the strong loss wavelength showed a quasi-sin θ changing with the twist angle ranging from 0° to 180° for S- or P-polarized input. A high sensitivity of 0.299 dB/° is achieved, which is almost 17.9 times higher than that of the current similar existing twist sensor. The twist angle can be measured precisely with the matrix.     

Fiber laser source/analyzer for Bragg grating sensor arrayinterrogation

This paper reports on the application of a calibrated, narrow-linewidth, single-frequency, continuously wavelength-tunable erbium fiber laser to the interrogation of a multipoint Bragg grating temperature sensor. The fiber laser was wavelength-tuned, through an array of three fiber Bragg grating sensors, to determine the temperature of each individual grating. The temperatures of the three gratings were measured as a function of grating Bragg wavelength. The minimum wavelength resolution, due to electro-mechanical repeatability, of the fiber laser source/analyzer was determined to be approximately 2.3 picometers. This corresponds to a frequency resolution of approximately 300 MHz     

基于倾斜光纤Bragg光栅的横向压力传感器研究

设计了一种基于4°倾斜光纤Bragg光栅(TFBG)和弹 性 材料的横向压力传感器。利用TFBG光谱对周围介质折射率响应的特性,实现了 对较低压力范围(0~7N)的线性测量。采 用快速傅里叶变换(FFT)方法对光谱进行解调,测量灵敏度可达1920 a.u./(N/mm),线性拟 合度为0.998。研究了不同弹性材料对测量灵敏度的影响,实现对测 量范围和测量灵 敏度的调谐。本文传感器工作在反射光谱方式,易于集成(光栅区长度仅5mm),可以植入弹 性材料内部用于协调接触压力的测量。     

具有自标定功能的光纤光栅位移传感器

为了解决光纤光栅(Fiber Bragg Grating, FBG)位移传感器易受温度、振动等外界因素影响而导致测量重复性差的问题,本文利用磁铁非接触的力传递特性,以光纤光栅为核心元件,工字型梁、永磁体等为辅助元件研究了一种无接触的FBG位移自校准装置。利用移动端磁铁与位置标定端磁铁位置重合时,工字型梁所受磁力最大,进行位置信息的自校准,进而提高FBG位移传感器的测量重复性和测量精度。通过将自校准装置安装在卷尺结构的位移传感器上,对其传感特性展开实验研究,结果表明：在0～360 mm的测量范围内,校准前平均均方根误差为5.838 mm,校准后平均均方根误差为0.953 mm。本文采用自校准装置在很大程度上提高了FBG位移传感器的测量重复性,为位移传感器的环境适应性优化提供了一种新方法。     

基于长周期光栅滤波的光栅解调系统

基于长周期光栅的边缘滤波特性,设计了一种光纤布拉格光栅的传感解调系统,适用于布拉格光栅的静态和动态解调。系统实现了3.5 nm范围内的线性解调,波长灵敏度为0.092 nm-1,波长分辨率可以达到0.01 nm。振动测量中检测信号稳定,测量频率误差在1%以内。针对长周期光栅对温度和弯曲敏感的问题,采用了适当的温度补偿和封装技术,使长周期光栅的温度漂移系数从112 pm/℃下降到45 pm/℃,显著提高了系统的稳定性。     

Concentration sensor based on a tilted fiber Bragg grating for anions monitoring

The ubiquity and importance of anions in many crucial roles accounts for the current high interest in the design and preparation of effective sensors for these species. Therefore, a tilted fiber Bragg grating sensor was fabricated to investigate individual detection of different anion concentrations in ethyl acetate, namely acetate, fluoride and chloride. The influence of the refractive index on the transmission spectrum of a tilted fiber Bragg grating was determined by developing a new demodulation method. This is based on the calculation of the standard deviation between the cladding modes of the transmission spectrum and its smoothing function. The standard deviation method was used to monitor concentrations of different anions. The sensor resolution obtained for the anion acetate, fluoride and chloride is 79 × 10⁻⁵ mol/dm³, 119 × 10⁻⁵ mol/dm³ and 78 × 10⁻⁵ mol/dm³, respectively, within the concentration range of (39–396) × 10⁻⁵ mol/dm³.     

Long period fibre grating torsion sensor measuring twist rate and determining twist direction simultaneously

A fibre-optic torsion sensor based on a long-period fiber grating written by high-frequency CO/sub 2/ laser pulses is proposed and has been demonstrated. Such a torsion sensor cannot only measure the applied twist rate directly, but also determine the twist direction simultaneously.     

基于磁流体的光纤光栅电流传感器

为了满足在电力装备中对电流监测的需求,本文提 出一种基于磁流体的长周期光纤光栅(long period fiber grating,LPFG)光学电流传感器。 外界磁场的变化可以引起磁流体折 射率的变化,LPFG的谐振波长受环境折射率的影响。将磁流体包裹的LPFG封装 结构置于通电导体周围的磁场环境中,通过测量LPFG的波长漂移量即可得到被测电流的情 况。实验证明了电流传感器的可行性及稳定性,其灵敏度约为－2.3 nm/A;该传感器结构简单、 灵敏度高、抗干扰性能良好,同时体积小、无磁滞效应,易于和电力设备集成;在电力系统 的电流监测中具有广阔的应用前景。     

Fiber Bragg grating based shear-force sensor: modeling and testing

This paper presents the design and fabrication of a novel shear-force sensor using fiber Bragg grating (FBG) as the sensing element. The basic design consists of layers of carbon composite material (CCM) with an embedded FBG. A deformable layer of silicon rubber between the layers of CCM allows the applied shear force to change the grating periodicity and, hence, the reflected Bragg wavelength. The shift in the reflected Bragg wavelength shows a linear variation with the applied shear force. A theoretical model is established to study the shear sensing ability. In addition, numerical modeling is also carried out by the finite-element method (FEM). The experimental results are found to be in good agreement with the theoretical predictions as well as the FEM results. In this paper, the basic concept of shear-force measurement using FBG and related theoretical model and FEM simulation results are discussed together with experimental verification.     

A novel oil level monitoring sensor based on string tilted fiber Bragg grating

In this paper,we present a novel oil level monitoring sensor based on string tilted fiber Bragg grating(TFBG).The measurement range and sensitivity of oil level monitoring can be modulated via changing the length and number of string tilted fiber gratings.The transmission spectrum of string TFBGs immersed in oil changes obviously with the oil level variation.Experiments are conducted on three 2 cm-length serial TFBGs with the same tilted angle of 10o.A sensitivity of 3.28 dB/cm in the string TFBG sensor is ...     

少模光纤布喇格光栅的光谱特性研究

相较于传统的单模光纤布喇格光栅(FBG)传感器,少模FBG传感器在测量时不易受到外界无关参量的影响,精度更高,但其在光栅参数设计上缺乏相应的理论依据。针对此问题,基于FBG耦合模理论,利用OptiGrating和Matlab软件模拟分析了纤芯中存在LP₀₁模、LP₁₁模的少模FBG的反射谱。仿真结果表明:区别于传统单模FBG的单峰结构,少模FBG的反射谱具有三峰结构,光栅周期、光栅长度和折射率调制深度的变化会对各波峰的反射率及中心波长产生规律性的影响。     

柔性复合基体光纤布拉格光栅曲率传感器

面向生物医学智能装备和软体机器人等领域柔性机构以及高端装备和重大基础设施复杂结构的曲率测量需求,提出一种高适应性柔性曲率传感器。通过将光纤布拉格光栅封装在硅胶基体中,并将硅胶基体与聚氯乙烯薄片贴合,形成基于光纤布拉格光栅的柔性硅胶曲率传感器。采用光纤传感解调系统和标准曲率标定块,实验测得光纤光栅传感器反射谱特征及其随标定块曲率变化规律,分析了光栅波长位移与曲率变化的关系以及传感器灵敏度与嵌入硅胶基体深度的关系。实验结果表明:硅胶-聚氯乙烯基体的曲率传感器可以实现曲率变化实时测量,最高灵敏度可达0.329 2 nm/m-1。随着光纤光栅嵌入深度的增加,传感器灵敏度在0.2~0.35 nm/m-1范围内逐渐增大。在多次重复测量中传感器具有较好的一致性,可用于柔性机构和复杂结构的曲率测量。     

基于变电站沉降监测的光纤光栅传感器

根据光纤布拉格光栅传感器具有抗干扰强、高灵敏度和工作寿命长等优良的物理特性,针对变电站沉降变形监测工程中存在的耗费大量人力、工作环境恶劣、积累时间长等突出问题,设计了新型光纤光栅沉降位移传感器,其沉降测量量程最大为300 mm,灵敏度为17.8 pm/mm,沉降位移分辨率为0.784 93 mm。与传统的沉降传感器相比,在测量灵敏度、分辨率和沉降量测量范围上有了极大的提高。综合实验结果,该传感器能实现对变电站地基和电气设备进行大范围、高灵敏度、高分辨率地沉降监测。     

Spectra of fiber Bragg grating and long period fiber grating undergoing linear and quadratic strain

The effects of linear and quadratic strain on the reflective spectrum of FBG and the transmission spectrum of LPFG have been numerically investigated based on the coupled -mode equations. The results show that for the FBG or LPFG undergoing only linear strain, the reflection or transmission spectrum is symmetrical about its central wavelength, the dependence relationships of the central wavelength shift, full-width-at-half-maximum, peak intensity upon the strain gradient have been obtained.     

Refractive index sensor based on measuring the transmission power of tilted fiber Bragg grating

A low-cost, compact and practical method to measure the surrounding refractive index (SRI) is proposed by measuring the transmission power of the tilted fiber Bragg grating (TFBG). The transmission power of the TFBG is detected when the SRI varies from 1.3723 to 1.4532; the power decreases monotonously from ?2.14 dBm to ?3.26 dBm. Under this condition, the resolution of the refractive index of TFBG is predicted to be 10^?4 and the resolution of the concentration of the solution is as slight as 0.01%. Considering its simple configuration and high stability, this way is potential to monitor physical, chemical and biological parameters in the natural environments.     

用于沥青路面载荷监测的光纤光栅压力传感器

提出了一种可用于沥青路面载荷测量的新型高灵敏度光纤布拉格光栅(FBG)压力传感器.传感器采用金属材料和聚合物相结合的封装形式,通过改变聚合物的几何结构实现了高倍数压力增敏效果,并从理论推导了该传感器的光栅中心波长相对偏移量与加载其上压强之间的解析关系.实验结果表明:该传感器的压力监测灵敏度达到2.39×10-8 Pa-...     

基于非对称F-P滤波器的光纤光栅解调技术

介绍了利用非对称光纤Fabry-Pérot（F-P）腔作为边沿滤波器的光纤光栅波长移位检测方案。基于薄膜干涉理论对该非对称F?蛳P腔的反射率响应关系进行计算与分析，得出该F-P腔的结构参数，改善了普通F?蛳P腔的反射特性，具有线性范围宽和线性度好的优点。利用该F-P腔的某一线性滤波边缘,将传感光栅的波长信息转化为功率信息进行检测，可完成光纤光栅的传感波长解调。采用该检测方案进行了光纤光栅应变传感实验,实现了在7 nm范围内的波长线性解调,测量波长分辨率为0.01 nm。     

一种预张拉大标距光纤光栅应变传感器的研究

研究开发出一种用于大传感标距测量的新型光纤光栅(FBG)应变传感器,提出一种基于预张拉原理的传感器封装方法.分别开发出传感标距为10 cm与20 cm的大标距FBG应变传感器,预张拉稳定性试验结果表明,传感器内的预张拉水平可以保持在一稳定水平.应用等截面梁标定方法研究了该传感器的应变复敏特性,结果显示,传感器布拉格波长与大标足巨内的平均应变具有非常好的线性关系.应用水浴法研究了该传感器的温度灵敏特性,结果显示,传感器布拉格波长与温度具有非常好的线性关系.最后,通过与小标距裸FBG的对比试验研究其测量大标距内平均应变的性能,结果显示,传感器可以准确测量大标距内的平均应变.     

高灵敏度级联长周期光纤光栅温度与应变传感的理论研究

根据长周期光纤光栅(LPFG)的温度和应变特性,从理论上设计一种具有更高灵敏度的传感器。将两个具有不同包层参数和周期的长周期光纤光栅串联起来,构成光纤光栅传感器;并对其进行数值模拟,结果表明此传感器具有更高的温度和应变灵敏度,同时能实现双参数测量。对影响传感器灵敏度的因素进行了进一步分析表明光栅包层参数、周期对灵敏度都有一定影响,在其他参数不变的情况下高阶模次的灵敏度高于低阶模次,这一结果能进一步提高灵敏度。