混凝土结构的光纤光栅智能监测技术

根据混凝土结构的内部应变监测需要，提出了光纤光栅管式封装应变传感器，并对其传感特性进行了研究；探讨了光纤布拉格光栅传感元件在混凝土结构中的布设工艺，并用光纤光栅监测了水泥净浆的固化过程；用管式封装光纤光栅与裸光栅对钢筋温凝土梁进行了应变监测；最后将光纤光栅传感器成功地应用于黑大公路大桥。     

FBG智能传感器及其在土木工程中的应用研究

光纤光栅传感器已经越来越得到土木工程界的认可,并应用到了实际工程.针对大型土木工程结构长期健康监测的变形监测需要,在光纤光栅传输理论的基础上,分析了光纤光栅应变与温度传感特性以及光纤光栅应变传感的温度补偿原理和方法;研制开发出满足工程应用的光纤光栅封装传感器、FRP-OFBG复合智能筋、光纤光栅智能拉索;此外,考虑传感器开发和工程应用的需要,研究了光纤光栅应变传感的界面传递机理和误差修正.最后,建立了光纤光栅智能监测系统,并成功地将光纤光栅传感器应用到实际桥梁结构的施工与运营监测.     

光纤光栅技术在煤矿安全生产中的应用

目前光纤传感技术应用于矿井安全监控领域以弥补传统传感器存在测量精度低、稳定可靠性差、易腐蚀和易受电磁干扰等不足。本文介绍了光纤光栅传感原理,讨论了光纤光栅传感技术在煤岩动力灾害、矿井水灾和火灾的应用。研究结果表明光纤光栅传感器具有抗电磁干扰、耐腐蚀、测量精度高、易于传输、准分布式测量等特点,在煤矿生产中具有广泛的应用前景。     

一种简易测试光纤光栅应变测量系统的方法

针对光纤光栅应变测量系统应用测试问题,基于悬臂等强度梁应变实验,对比理论计算、光纤光栅应变传感器及电阻应变片的三种应变测量方法,得出光纤光栅应变测量系统具有较好的可靠性和准确性。以国外可靠光纤光栅应变测量系统为参照,提出了简易测量光纤光栅应变传感器和光纤光栅传感分析仪性能的方法。针对准分布式监测问题,主要分析了光分路器对光纤光栅传感应变测量的影响。上述分析为光纤光栅应变测量系统在工程中的应用提供充分依据。     

基于光纤布喇格光栅传感器的精密位移测量

首先对光纤布喇格光栅传感的基本原理进行了分析,并给出了光纤光栅位移传感的基本公式.在此基础上,设计制作了一种光纤光栅位移传感器.采用光纤光栅作为传感元件,利用多波长计进行波长检测,对位移量进行了传感测量.实验中,传感器位移检测范围为0.6mm,其传感测量精度为±43nm,测量分辨率为1.5nm.实验结果具有良好的线性度.     

光纤光栅振动传感系统仿真研究与分析

由于光纤光栅传感器具有灵敏度高、动态范围宽、不受电磁干扰、成本低、体积小等优点,使其在传感领域具有很好的应用前景.光纤光栅传感技术已成为现代传感领域的一个重要研究方向,其在振动传感领域的应用也取得了一定的成就.本文针对悬臂梁式光纤光栅振动传感,将光纤光栅振动传感元件近似为惯性式振动系统,以其数学模型为基础,利用Matl...     

光纤光栅传感器在建筑施工中的应用研究

光纤光栅传感器是一种新兴的传感器,文章主要介绍了其传感原理和特点,分别论述了光纤光栅温度传感器和光纤光栅应变传感器在建筑施工中的应用场合,介绍了典型的应用实例和各自的工作原理,找到了光纤光栅传感器在建筑施工应用方面的关键技术难点,并对这两个技术难点提出了解决方案,最后指出了光纤光栅传感器在建筑施工方面应用的前景和发展方向。     

复合材料胶层光纤布格光栅应变监测优化配置研究

航空航天用复合材料粘接胶层在制造和服役过程中不可避免会产生各种缺陷和损伤。针对其粘接胶层缺陷和损伤检测,基于光纤光栅应变传感原理,提出一种针对复合材料胶接层结构应变监测的光纤光栅传感网络优化配置的方法。通过仿真和实验研究了埋入复合材料构件胶接层的光纤布拉格光栅传感器在静载作用下的敏感区域分布特性,分析了载荷位移与布拉格波长漂移的关系,建立符合光纤布拉格光栅传感器实际特点的探测模型,采用粒子群优化算法进行光纤光栅传感网络的优化布置,研究结果表明光纤布拉格光栅传感器位置经优化后,覆盖率得到明显提高。     

光纤布拉格光栅应变与温度传感特性及其实验分析

对光纤布拉格光栅应变与温度传感特性进行了分析，理论计算了波长变化对传感系数的影响，提出了光纤光栅应变传感的温度补偿方法，并理论分析了光纤光栅温度和应变传感的耦合作用，最后，通过材料实验与等强度梁实验研究与分析了光纤光栅的应变与温度传感特性。理论分析与实验结果表明，两者吻合很好，光纤光栅的波长变化与应变和温度存在很好的线性关系，波长变化对传感系数的影响很小。     

一种用于低频测量的光纤光栅振动传感器

利用光纤光栅敏感技术,设计了一种用于低频测量的光纤光栅振动传感器.该传感器采用了等强度悬臂梁作为振动传感元件,并在等强度悬臂梁的上下双面优化布置性能匹配的两个光纤光栅,一个为振动敏感测量光栅,另一个为信号匹配滤波解调光栅.该结构设计可以补偿温度的不利影响,同时也提高了传感器信号检测的灵敏度.实测结果表明,该传感器可以用于25 Hz以下的低频目标的振动测量.     

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。     

基于遗传算法的光纤光栅横向均匀受压谱型识别技术的研究

采用遗传算法对光纤光栅横向均匀受压的谱型识别技术进行了研究,建立了系统的优化数学模型,确定了对应的目标函数,分析了种群规模、进化代数、交叉率、变异率等参数选值对算法运行结果的影响,并选取了算法的运行参数组合。构建了光纤光栅横向均匀受压传感系统,完成了相关的仿真与实验。结果表明,用遗传算法实现的光纤光栅横向均匀受力系统应力测量的实验精度可达到0.86%。     

Combined time- and wavelength-division-multiplexing demodulation technique of fiber grating sensor arrays using a tunable pulsed laser

Combined time- and wavelength-division-multiplexing demodulation technique of fiber Bragg grating (FBG) sensor arrays using a tunable pulsed laser is proposed and demonstrated. A tunable fiber laser based on a matched FBG is applied. The wavelengths of the sensing FBGs are obtained by detecting the maximum voltages with a photodiode that avoids the complex demodulation process. The advantages of this scheme are simple structure, high signal-to-noise ratio, and the sensing signals obtained by detecting the maximum voltages.     

Response of fiber Bragg gratings to longitudinal ultrasonic waves

In the last years, fiber optic sensors have been widely exploited for several sensing applications, including static and dynamic strain measurements up to acoustic detection. Among these, fiber Bragg grating sensors have been indicated as the ideal candidate for practical structural health monitoring in light of their unique advantages over conventional sensing devices. Although this class of sensors has been successfully tested for static and low-frequency measurements, the identification of sensor performances for high-frequency detection, including acoustic emission and ultrasonic investigations, is required. To this aim, the analysis of feasibilty on the use of fiber Bragg grating sensors as ultrasonic detectors has been carried out. In particular, the response of fiber Bragg gratings subjected to the longitudinal ultrasonic (US) field has been theoretically and numerically investigated. Ultrasonic field interaction has been modeled, taking into account the direct deformation of the grating pitch combined with changes in local refractive index due to the elasto-optic effect. Numerical results, obtained for both uniform and Gaussian-apodized fiber Bragg gratings, show that the grating spectrum is strongly influenced by the US field in terms of shape and central wavelength. In particular, a key parameter affecting the grating response is the ratio between the US wavelength and the grating length. Normal operation characterized by changes in wavelength of undistorted Bragg peak is possible only for US wavelengths longer than the grating length. For US wavelengths approaching the grating length, the wavelength change is accompanied by subpeaks formation and main peak amplitude modulation. This effect can be attributed to the nonuniformity of the US perturbation along the grating length. At very high US frequencies, the grating is not sensitive any longer. The results of this analysis provide useful tools for the design of grating-based ultrasound sensors for meeting specific requirements in terms of field intensity and frequencies.     

Brillouin Optical Frequency-Domain Single-Ended Distributed Fiber Sensor

We propose a scheme for single-ended distributed fiber sensing based on stimulated Brillouin scattering, in which a fiber Bragg grating is used as wavelength-selective reflector. The proposed configuration requires access to only one end of the sensing fiber, and operates in the frequency domain. Measurements with a spatial resolution down to 1 m and sensing lengths up to 5 km are reported.      

Fiber grating sensing interrogation based on an InGaAs photodiode linear array

We present a new method of the fiber grating sensing interrogation technique by utilizing an indium gallium arsenide photodiode linear array and blazed fiber Bragg gratings. An interrogation system based on an InGaAs photodiode linear array is designed, and the system performance is analyzed. The interrogation system shows a good prospect for smart sensing.     

Distributed measurement of static strain in an optical fiber with multiple bragg gratings at nominally equal wavelengths

The Fourier transform relationship between the reflected light froma Bragg grating and the complex spatial modulation of the Bragg grating is used to produce a distributed strain sensing system. A tunable external cavity diode laser along with a reference reflector in anoptical fiber are used to produce a measurement of the phase and amplitude of the reflected light from the modulated Bragg grating as a function of wavelength. The system is demonstrated with 22 Bragg gratings in a single fiber on a cantilever beam and compared with foil strain gauge readings.     

基于裸光纤光栅传感技术GFRP抗浮锚杆荷载传递机制的原位试验研究

基于3根全螺纹GFRP抗浮锚杆现场拉拔破坏性试验,成功地将植入式裸光纤光栅传感技术应用于抗浮锚杆拉拔试验中,研究了全长黏结GFRP抗浮锚杆在各级荷载作用下的承载特性、荷载传递特征及破坏机制。研究表明:植入式裸光纤光栅传感技术有其独特的优越性,不会对锚杆自身造成损伤;GFRP抗浮锚杆破坏以杆体基体材料剪切破坏为主,锚固长度为5.0 m,ϕ28 mm锚杆极限抗拔承载力为400 kN,能够满足工程需求;锚杆的轴向应力主要集中在距孔口约3.0 m的区域,且随着锚固深度的增加迅速衰减;剪应力峰值出现在距离孔口以下约0.8 m的位置,随着荷载的增加,剪应力曲线的峰值逐渐增大并向深部移动。在此基础上,进一步分析论证了GFRP抗浮锚杆的破坏机制,为GFRP抗浮锚杆的工程应用提供了理论依据。     

Advanced cure monitoring by optoelectronic multifunction sensing system

In this work, a dual functionality fiber optic sensing system for thermoset cure monitoring has been developed and successfully tested. Principle of operation relies on the use of a standard optical fiber in single ended configuration containing a single in-fiber Bragg grating. The change in refractive index directly related to material density at fiber end and the variation in the wavelength reflected by the fiber grating have been monitored simultaneously, throughout an In-Mould curing process of an epoxy resin. A compact and low cost in-fiber dual wavelength demodulation system has been developed and experimental results demonstrate the capability to on line identify the degree of cure, gel point, residual stresses and the glass transition temperature of the cured resin.