Ultrahigh sensitivity polarimetric strain sensor based upon D-shaped optical fiber and surface plasmon resonance technology

An ultrahigh sensitivity polarimetric strain sensor is proposed based upon a four-layer D-shaped optical fiber and surface plasmon resonance (SPR) technology. In contrast to existing SPR-based sensors, which are based on changes in the refractive index of the overlayer, the sensor proposed in this study is based on the change in the refractive index of the fiber core in response to the application of an axial load. Specifically, the phase difference between the P and S waves after passing through the sensor under SPR conditions is measured using a common-path heterodyne interferometer and is used to determine the corresponding change in the refractive index of the core, from which the strain is then inversely derived. The experimental results show that the sensitivity of the proposed sensor is around 2.19×10? deg/ε, i.e., degree/strain. By contrast, that of a conventional (non-SPR) polarimetric fiber sensor is just 5.2×102 deg/ε. To the best of the authors' knowledge, the sensor proposed in this study represents the first reported attempt to exploit the refractive index change of the core of an SPR-based fiber sensor for strain measurement purposes.     

高灵敏度光纤应变传感器

提出一种基于锥形光纤和光纤F-P腔组合结构的光纤应变传感器。该传感器包含单模光纤拉锥形成的锥区和石英毛细管构建的F-P腔2个应变敏感区域。理论分析了光波在该传感器中的传播过程,获得了该传感器的光强传输函数。由于锥形光纤中激发出的包层高阶模参与干涉,导致传感器干涉光谱具有调制特性。实验获得了该传感器的干涉光谱,通过分析谐振波长偏移或消光比变化对应变实现独立测量,在0~500 με的测量范围内,该传感器的应变灵敏度为14.6 pm/με。利用锥形光纤引发的模式干涉和F-P腔的双光束干涉效应共同作用形成受调制的干涉谱型进行应变传感,应变灵敏度高,同时具备2种独立的应变检测手段(谐振波长和消光比检测)。     

Quantum-behaved particle swarm optimization algorithm for the reconstruction of fiber Bragg grating sensor strain profiles

A quantum-behaved particle swarm optimization algorithm used for demodulating the strain profile along a fiber Bragg grating (FBG) from its reflection spectrum has been demonstrated. By combining the transfer matrix method for calculating the reflection spectrum of a FBG and the quantum-behaved particle swarm optimization technique, we develop a new technique for the reconstruction of FBG sensor strain profiles. This proposed technique is verified through numerical example reconstructions of FBG sensor simulated strain profile cases and numerical simulations reveal good agreement between the original and the reconstructed strain profiles.     

High spatial resolution distributed strain sensor based on linear chirped fiber Bragg grating and fiber loop ringdown spectroscopy

A simple sensor system for high spatial resolution distributed strain field measurement is proposed and demonstrated experimentally. The fiber loop ringdown technique combined with a linear chirped fiber Bragg grating is used to realize the high spatial resolution. A proof-of-concept distributed strain sensor with 2?mm spatial resolution is realized. The sensor network is also explored and researched experimentally. The proposed technique suggests a broad range of applications for real-time distributed physical parameter sensing, such as strain or temperature.     

埋入式光纤光栅应变测量系统的设计

埋入式光纤光栅应变传感器作为大型土木结构健康监测的智能元件具有很好的发展前景。讨论了埋入式光纤光栅应变传感器的传感机理，设计了埋入式光纤光栅应变测量系统。从力学角度阐述了光栅传感探头的结构和制作工艺。采用可调谐F-P滤波器对光栅信号进行解调，解决了应变与温度交叉敏感问题。系统对应变的测量范围为0～1500με。通过理论分析证实了系统方案的可行性。     

A Novel Fiber Bragg Grating with Triangular Spectrum and Its Application in Strain Sensor

A novel fiber Bragg grating with triangular spectrum is presented. A strain sensor based on this fiber grating is proposed. Experiments showed that the sensor has advantages of high sensitivity, wider measuring range and immunity to fluctuation of the light source power.     

弯曲增敏型光纤曲率传感器机理的研究

近年国外出现一种直接检测弯曲的低成本光纤曲率传感器,采用弯曲增敏技术提高光纤对弯曲的灵敏度。这种传感器的线性范围宽,能区分正向弯曲和负向弯曲,在测量较大弯曲变形的场合更具优势;并且适合埋入结构内部检测,通过转换还可测量轴向应变。然而其传感机理方面的研究仍处于探索阶段。通过分析光辐射度余弦定律理论、回音壁光线理论、沟槽角度理论等国内外对该传感器机理的研究成果,并基于平面波导的光散射损耗理论,提出了光纤曲率传感器的机理。指出弯曲引起光纤敏感区表面散射损耗的改变是导致光传输损耗改变的原因;推导出损耗与光纤弯曲半径、表面特性、光纤结构参量关系的数学模型,并通过实验验证了模型的有效性。     

A new method to eliminate the influence of the backward defect infection and the position-dependent of the coefficient on distributed Brillouin fiber sensor

Two theoretical problems associated with the measurement of temperature or strain from the normalized power of Brillouin signal in a distributed fiber sensor are studied. One problem is the position-dependent of the coefficient relating the Brillouin power to the local temperature or strain. The other problem is the backward infection of the defect (local temperature or strain change). These two problems will degrade the measurement accuracy of a distributed Brillouin fiber sensor by changing the distribution of pump power. To eliminate these two problems, new reference functions are proposed to normalize the Brillouin signal. Simulation results by using fourth-order Runge-Kutta algorithm show that these new reference functions can eliminate the influence of these two problems on distributed Brillouin fiber sensor.     

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。     

基于光谱特征分析的光纤光栅腐蚀传感器研究

针对航空航天领域铝合金结构服役过程腐蚀监测需求,提出了一种基于铝质细管结构的预载荷型光纤光栅腐蚀传感器。给出了铝合金结构腐蚀在役监测机理,得到光纤光栅反射光谱特征与铝质细管厚度变化之间的理论关系模型,构建了酸碱环境下的光纤光栅腐蚀监测试验系统。通过在细管内部配置不受力且仅感受温度变化的光纤光栅传感器,解决了被测目标的温度与应力交叉敏感问题。研究表明,这种铝质细管封装设计不仅可以感受腐蚀对其力学性能的影响,还能够屏蔽外界腐蚀因素对管内光纤感知器件的干扰。随着金属管腐蚀程度加深,其管壁逐渐变薄,光纤光栅反射光谱逐渐向短波长方向偏移,且管壁厚度变化与光栅中心波长偏移量之间呈较好单调关系。这些特性能够为进一步开展基于光纤感知器件的机械结构在役腐蚀监测研究提供有益帮助。     

基于封装光纤Bragg光栅传感器的混凝土应变监测试验研究

研究了光纤Bragg光栅封装工艺,提出并实现了两种封装光纤Bragg光栅传感器:工字型钢管封装光纤Bragg光栅应变传感器及钢管封装光纤Bragg温度传感器。研究了传感器的埋设工艺,采用金属丝固定法、钢管抽出法两种方法进行了埋设。将它们埋入到钢筋混凝土梁中,实现对混凝土的拉、压应变及温度的测量。结果显示,在试验梁弹性阶段,可以较为准确的监测混凝土应变。     

基于掺铒光纤的微型光纤法布里-珀罗干涉传感器

提出了一种化学腐蚀掺铒光纤制作微型光纤法布里-珀罗干涉传感器的方法。通过对掺铒光纤进行化学腐蚀,形成凹槽,再与单模光纤直接熔接制作而成。实验制作的微型法布里-珀罗干涉传感器干涉条纹光滑,对比度达到15dB。对该微型光纤法布里珀罗干涉腔进行了应变和温度传感实验。实验结果表明,在0-600με￡内,波谷移动随应变改变的灵敏度达到1．7pm／με,线性度为0．9998,从73～23℃,波谷移动随温度改变的灵敏度3．9pm／℃,线性度为0．9982。该方法制作的微型光纤法布里-珀罗传感器具有操作简单,一次成型,制作成本低的优点。     

Intensity measurement based temperature-independent strain sensor using a highly birefringent photonic crystal fiber loop mirror

A fiber-optic strain sensor is demonstrated by using a short length of highly birefringent photonic crystal fiber (HiBi-PCF) as the sensing element inserted in a fiber loop mirror (FLM). Due to the ultralow thermal sensitivity of the HiBi-PCF, the proposed strain sensor is inherently insensitive to temperature. When a distributed-feedback (DFB) laser passes through the FLM, the output power is only affected by the transmission spectral change of the FLM caused by the strain applied on the HiBi-PCF. Based on intensity measurement, an optical power meter is adequate to deduce the strain information and an expensive optical spectrum analyzer (OSA) would not be needed.     

埋入式F-P光纤应变传感器在混凝土桥梁健康监测中的应用研究

对基于白光干涉的埋入式F_P光纤应变传感器的测试原理及主要结构参数进行了分析,介绍了该埋入式传感器的研制工艺特点。通过对传感器的性能考核试验,验证了该传感器具有优良的精度稳定性和耐久性,通过秦沈客运专线辽河特大桥施工过程监测试验,验证了该传感器满足桥梁施工现场复杂状况下混凝土结构应变监测的要求。由于该传感器的成本不及同类型进口产品的1/5,具有广阔的普及应用前景。     

光纤法-珀传感器监测混凝土固化期收缩应变的实验研究

本文介绍了光纤法-珀应变传感器的基本原理及优点,并用其进行了混凝土固化过程中的收缩应变监测实验,在混凝土两天的固化过程中监测到了130微应变的收缩应变.本文还对光纤法-珀应变传感器的温度稳定性能进行了理论分析及对比实验,实验结果表明,在一定条件下环境温度对光纤法-珀应变传感器的影响可忽略不计,因此可不用任何温度补偿.     

Dynamic strain measurement using two wavelength-matched fiber Bragg grating sensors interrogated by a cascaded long-period fiber grating

In this work, we describe a fiber Bragg grating (FBG) sensing system using two wavelength-matched FBG sensors for static and dynamic strain measurement. A cascaded long-period fiber grating (CLPG)-based demodulation technique has been used to interrogate the two wavelength-matched FBG sensors. Experimental results of static strain measurement show that the proposed system has a strain resolution of 1 με. This system has also been used for dynamic strain measurement. An eddy current displacement meter-based system has been used as a comparison measurement. Experimental results of dynamic strain measurement have proved that the FBG sensing system has a good performance in the measurement of dynamic strain. The results of static and dynamic strain measurement indicate that the sensing system using two wavelength-matched FBG sensors is superior to the single FBG sensor system.     

Integration of miniature Fabry-Perot fiber optic sensor with FBG for the measurement of temperature and strain

A sensor has been fabricated by the integration of a fiber Bragg gating sensor (FBGs) with a fiber Fabry-Perot (F-P) sensor fabricated by etching method. In the integrated sensor, the FBG was used to measure temperature, while the fiber Fabry-Perot interferometer sensor (FFPIs) was used for strain measurement. Wavelength decoding for FBG and peak tracking for FFPI was employed for demodulation, respectively. The result showed that the temperature and strain sensitivity for the integrated sensor is ~ 2.7 pm/μεand ~ 9.3 pm/°C, respectively.     

一种新型光纤法布里-珀罗应变干涉仪

论述了一种非本征法布里 珀罗光纤应变传感器。采用透明弹性聚合物薄膜作为法布里 珀罗干涉腔,聚合物固定在多膜光纤末端作为应变敏感元件。传感器的分辨率为2μm,测量精度在0～5000μm范围内为5μm。     

基于空气孔微结构光纤的表面等离子体共振折射率传感器北大核心CSCD

提出了一种基于表面等离子体共振(SPR)效应增强的光子晶体光纤折射率传感器。该传感器结构通过光纤熔接机拼接光子晶体光纤(PCF),在光子晶体光纤中间引入一个空气孔形成PCF-空气孔-PCF的光纤传感结构,随后使用磁控溅射镀膜工艺在其表面沉积一层薄金膜制备而成。实验探究了折射率及温度对传感器的响应。结果表明,在1.333~1.389的折射率范围内,所提出的传感器的平均折射率灵敏度为2 142.52 nm,且测量线性度为0.981,品质因子约13.10。实验结果表明该传感器对温度不敏感。相比于无空气孔的PCF传感结构,引入的空气孔增强了SPR效应,使得传感器拥有良好的共振峰深度。得益于上述优势,该类型传感器有望在生物医学、环境监测等领域得到应用。     

高分辨率光纤应变传感技术的研究

介绍光纤应变传感器中光纤端面反射镜的制作方法,镀膜光纤的连接技术和构成不对称光纤法布里－珀罗干涉腔的方法。应用低反射率不对称光纤法布里－ 珀罗干涉腔与光纤连接构成的光纤应变传感器,以提高分辨率;重点导出此干涉腔反射光与应变的数学模型,论述其工作原理和测量方法,通过实验证明文中所述应变传感原理和测量方法是正确的,其分辨率优于０－００６８με。