基于相移布喇格光纤光栅的折射率传感实验研究

利用图解法求解光纤特征方程,获得腐蚀过程和传感过程中光纤光栅的光谱特性,设计了光纤光栅的部分腐蚀方案,采用氢氟酸溶液腐蚀制作相移布喇格光纤光栅。对光纤光栅进行部分腐蚀,将形成相移光纤光栅。根据相移光纤光栅的特性,讨论了利用反射光光强解调的方式,该方式具有结构简单且对温度不敏感的优点。     

用于钢筋混凝土梁的光纤光栅应变传感器

在变形测定器中,光纤Bragg光栅被粘贴于内管的两端,这两端的距离确定了传感器的量规长度。为了测量拉应变和压应变,该光纤光栅必须保持处于与可能的最大压应变相等的永久性拉应变。将光纤Bragg光栅贴于H154梁的混凝土表面和H158梁的钢筋表面,以分别检测拉应变和压应变。当钢筋混凝土梁受到千斤顶的加载时,它的应变可由光纤Bragg光栅的反射Bragg波长的偏移量获得。实验表明,作为一种绝对检测器件,光纤Bragg光栅为钢筋混凝土梁提供了有效监测,其中,拉应变~1000me,而压应变~1500me。     

光纤布喇格光栅反射波长移位的探测

综述了光纤布喇格光栅反射波长移位的探测方法。提出一种新的压电陶瓷－应变片组合探测光纤布喇格光栅反射波长的方法,它具有波长移位探测精度高、线性度好、结构紧凑等优点。     

Strain and damage monitoring of CFRP in impact loading using a fiber Bragg grating sensor system

A fiber-optic system featuring strain measurement and ultrasonic detection was constructed with fiber Bragg gratings based on wavelength–light intensity conversion technique. This fiber Bragg grating sensing system consists of a broadband light source, a broadband optical filter for strain measurement and a narrowband tunable filter for ultrasonic detection. The system was applied to strain measurement in impact loading to carbon fiber-reinforced plastics and the subsequent impact damage detection. Experimental results demonstrated that fiber Bragg grating sensors could measure strain with higher resolution compared with conventional strain gauges. Furthermore, ultrasonic inspection in which ultrasonic sensitivity was maximized by controlling the transmissive wavelength of the tunable filter could detect a 6.3 × 9 mm² impact damage.     

Modeling, design, fabrication, and testing of a fiber Bragg grating strain sensor array

The modeling, design, simulation, fabrication, calibration, and testing of a three-element, 15.3 cm fiber Bragg grating strain sensor array with the coherent optical frequency domain reflectometry (C-OFDR) interrogation technique are demonstrated. The fiber Bragg grating array (FBGA) is initially simulated using in-house software that incorporates transfer matrices. Compared to the previous techniques used, the transfer matrix method allows a systemwide approach to modeling the FBGA-C-OFDR system. Once designed and simulated, the FBGA system design is then imprinted into the core of a boron-germanium codoped photosensitive fiber using the phase mask technique. A fiber optic Fabry-Perot interferometric (FPI) strain gauge calibrator is then used to determine the strain gauge factor of a single fiber Bragg grating (FBG), and the results are used on the FBGA. The FPI strain gauge calibrator offers nondestructive testing of the FBG. To test the system, the FBGA is then attached to a 75 cm cantilever beam and interrogated using an incremental tunable laser. Electric strain gauges (ESGs) are then used to independently verify the strain measurements with the FBGA at various displacements of the cantilever beam. The results show that the peak strain error is 18% with respect to ESG results. In addition, good agreement is shown between the simulation and the experimental results.     

利用WDM光纤耦合器的光纤光栅传感解调技术

根据 WDM 光纤耦合器波长解调方案的工作原理、偏振特性以及影响系统波长分辨力的因素,提出一种改进的利用 WDM 光纤耦合器的光纤光栅传感解调技术。该技术在原技术的基础上,采用偏振控制器控制入射光偏振状态,提高了解调的精度和稳定性。对 WDM 光纤耦合器的多次波长扫描结果表明,采用偏振控制器后,其波长误差可减小到 5pm 左右。实验采用 1540/1560nm的 WDM 光纤耦合器对单点光纤光栅应变传感器进行静态解调,结果表明:按此技术开发的解调系统具有 0.01nm 波长分辨力和 10nm 的波长线性解调范围。     

From the reflected spectrum to the properties of a fiber Bragg grating: a genetic algorithm approach with application to distributed strain sensing

We describe a genetic algorithm approach to solve an inverse problem in optics, which determines the characteristics of a fiber Bragg grating from its reflected spectrum. The validity of the proposed method is demonstrated by use of a Bragg sensor for the measurement of nonlinear strain acting on a uniaxial aluminum test specimen.     

Phase-based Bragg intragrating distributed strain sensor

A strain-distribution sensing technique based on the measurement of the phase spectrum of the reflected light from a fiber-optic Bragg grating is described. When a grating is subject to a strain gradient, the grating will experience a chirp and therefore the resonant wavelength will vary along the grating, causing wavelength-dependent penetration depth. Because the group delay for each wavelength component is related to its penetration depth and the resonant wavelength is determined by strain, a measured phase spectrum can then indicate the local strain as a function of location within the grating. This phase-based Bragg grating sensing technique offers a powerful new means for studying some important effects over a few millimeters or centimeters in smart structures.     

Pressure Vessel Wall Thinning Detection Using Multiple Pairs of Fiber Bragg Gratings For Unbalanced Strain Measurements

This paper proposes a method for using a pair of identical fiber Bragg gratings to measure the unbalanced strain factor in an isothermal-mechanical system. Cascading two identical fiber Bragg gratings, the unbalanced strain factor caused by the disturbance can be interrogated from the peak difference of the two reflecting Bragg wavelengths. If the mechanical system is in an isothermal environment, the thermal variations in the Bragg grating detection system can be automatically compensated. To verify the feasibility of the unbalanced strain detection using a pair of fiber Bragg gratings, the wall-thinning monitor in a pressure vessel system was investigated. The proposed technique is easy to install, immune to electro-magnetic and thermal interference, and highly sensitive in-time to remote monitoring for fiber optic smart structures.A finite element model (FEM) is used to simulate the wall thinning in a pressure vessel system. The minimum detectable unbalanced strain and cross-talk between two reflecting Bragg wavelengths were investigated.ROC Revised for Journal of Nondestructive Evaluation, 2000     

Femtosecond laser-inscribed fiber Bragg gratings for strain monitoring in power cables of offshore wind turbines

A fiber Bragg grating sensor system used for monitoring the effects of strain on the power cable of an offshore wind turbine is presented. The Bragg grating structure was inscribed into coated nonphotosensitive standard telecommunication fibers using an IR femtosecond laser and the point-by-point writing technique. Because of the presence of the protective coating of the fiber, the mechanical stability of the resultant sensor device is better than that of a sensor consisting of a bare fiber. A system containing this sensing element was to our knowledge for the first time successfully installed and tested in an offshore wind turbine prototype (REpower 6M, REpower Systems, AG, Germany) in February 2010, near Ellh?ft (Germany). The fabrication process of the fiber Bragg gratings, measurement results of the online monitoring, and a comparison between the sensor signal and commonly used sensing techniques are presented.     

基于倾斜光纤光栅的传感解调技术

该文设计了一种基于倾斜光纤光栅（tilted fiber Bragg grating,TFBG）的不受温度影响的光纤布拉格光栅（fiber Brag ggrating,FBG）应变解调系统．将倾斜光纤光栅用作边沿痣波器,当周围环境温度变化时,利用倾斜光纤光栅纤芯模与包层模的温度特性与普通光纤布拉格光栅相同这一特点,无需另加温度补偿,就可以实现FBG应变传感的动态解调,消除温度噪声对应变信号的影响．由实验可知,当温度在25℃到39℃范围变化时,解调系统的性能基本不发生改变,解调范围达到6nm．     

Strain sensitivity control of fiber Bragg grating structures with fused tapers

We report on the analysis and experimental validation of the strain sensitivity dependences of a fiber Bragg grating written in standard optical fiber when combined with fused tapers. By controlling the difference between the cross sections of the fused taper and the Bragg grating, the strain sensitivity of the Bragg wavelength can be changed by acting on the gauge length. The strain sensing characteristics of an interferometric structure formed by fabricating a fused taper in the middle of a fiber Bragg grating are also reported.     

Multiplexed Fiber Bragg Grating Interrogation System Using a Microelectromechanical Fabry–Perot Tunable Filter

This paper describes a fiber Bragg grating strain sensor interrogation system based on a microelectromechanical systems tunable Fabry–Perot filter. The shift in the Bragg wavelength due to strain applied to a sensor fiber is detected by means of a correlation algorithm which was implemented on an embedded digital signal processor. The instrument has a 70 nm tuning range, allowing multiple strain sensors to be multiplexed on the same fiber. The performance of the interrogator was characterized using an optical fiber containing six grating strain sensors embedded in a fiberglass test specimen. The measured root mean square (RMS) strain error was 1.5 microstrain, corresponding to a 1.2 pm RMS error in the estimated wavelength shift. Strain measurements are produced with an update rate of 39 samples/s.      

光纤布拉格传感器兰姆波检测的反射谱分析

传统的兰姆波多采用压电陶瓷换能器激发和接收。建立了新的超声兰姆波无损检测系统,其基本思想是采用布拉格光纤传感器作为兰姆波的接收器。光纤光栅传感的基本原理是通过检测光栅反射的中心波长移动实现对外界参量如超声的测量。超声作用下光纤光栅的反射谱发生变化,对超声作用下光纤光栅的反射谱变化进行了数值分析,结果表明,超声对光栅反射谱的影响与超声波长与光栅长度的比值是高度相关的。只有当这个比值相当大时,反射谱的形状才不会变化而中心波长发生偏移,此时光纤传感器可用来探测兰姆波。这个结论为利用新的兰姆波无损检测系统在布拉格光栅长度的设计和兰姆波波长的选择方面提供了有用的工具。     

基于光电缆的分布式温度传感网络的实验研究

本文提出增加一根光纤光栅与光电缆绕制在一起,用于监测电缆中的实时温度.采用有限元分析方法,建立了光电缆温度场模型.使用可调谐脉冲激光为光源,在一根光纤上刻制多个相同中心波长的布拉格光栅,即采用全同光栅作为系统的温度传感器,当光电缆线路中温度发生异常时,反射回来的光栅中心波长发生偏移,通过检测反射光中心波长发生的偏移量可...     

用纤内Bragg光栅进行动态应变测量的研究

描述了用纤内Bragg光栅进行动态应变测量研究的意义，原理和方法，提出了两种用纤内Bragg光栅动态应变测量时进行Bragg波长偏移量的解调方法；光干涉相位检测Bragg光栅反射波长偏移的解调方法和用DWDM密集波分复用器解调Bragg波长的方法，前者适用于高频宽带动态应变测量，后者适用于有限频率或中等频率响应的动态应变测量。     

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。     

Simultaneous measurement of strain and temperature by use of a single-fiber Bragg grating and an erbium-doped fiber amplifier

We propose and demonstrate a novel sensor by using a single-fiber Bragg grating that can simultaneously measure strain and temperature with the aid of an erbium-doped fiber amplifier. By using a linear variation in the amplified spontaneous emission power of the erbium-doped fiber amplifier with temperature, we determine the temperature. By subtracting the temperature effect from the fiber Bragg grating Bragg wavelength shift, we determine the strain. Experiments show rms deviations of 18.2 muepsilon and 0.7 degrees C for strain and temperature, respectively.     

Dual temperature and strain measurement with the combined fluorescence lifetime and Bragg wavelength shift approach in doped optical fiber

We have constructed fiber-optic sensors to measure temperature and strain by combining the properties of fiber Bragg gratings with the fluorescent lifetimes of various doped fibers. Sensors have been made with the fiber Bragg grating written directly into the doped fiber to ensure the collocation of the strain and temperature measurement points. Results are compared with those obtained previously from a Bragg grating written into standard photosensitive fiber spliced to doped fiber. Standard deviation errors of 7 microepsilon and 0.8 degrees C have been obtained for strain and temperature ranges of up to 1860 microepsilon and 120 degrees C, respectively.     

基于双模LPFG折射率不敏感双参量传感器

环境折射率和环境温度变化是影响光纤应变测量误差的主要因素.本文利用双模光纤纤芯双模式(LP01和LP11)支持特性设计了一款环境折射率不敏感的双模光纤(DMF)长周期光纤光栅LPFG)应变传感器.设计了传感器模型结构,制作了最优化参数的传感器样品.实验测试了DMF-LPFG传感结构对外部环境中应变、温度和折射率的响应....