高精度准分布式光纤光栅传感系统的研究

利用一个经过温度补偿封装的长周期光纤光栅解调系统中所有测量点的传感光栅的波长漂移,实现了实时、高效解调的准分布式测量.理论研究表明该系统适用于对温度、应变等参量的多布点准分布式测量.并以温度为例从实验上研究了高精度的准分布式光纤光栅传感系统.通过改善每个测量点的测量精度来提高整体系统的测量精度.利用金属槽对传感光纤布喇格光栅进行增温敏封装,使其温度灵敏系数比普通裸光栅提高了3.6倍,并利用经过温度增敏封装的光栅作为传感元件,在110℃(-50 ℃-60 ℃)的动态范围内实现了精度为0.04- ℃的多布点准分布式温度测量,理论分析与实验结果一致.     

Modeling and performance analysis of a fiber Bragg gratinginterrogation system using an acousto-optic tunable filter

The performance of a fiber grating interrogation system using an acousto-optic tunable filter (AOTF) is analyzed. An equivalent linear circuit is presented to describe the system, which tracks the wavelength of a fiber Bragg grating (FBG) sensor in a FBG sensor array. From the model, the tracking resolution of a shot-noise-limited system has been determined for both transmissive and reflective interrogation of FBGs. An optimum ratio between the bandwidths of the FBG and the AOTF has been derived. Experimental results of a tracking system are presented to validate the theoretical predictions. The theory should also be suitable for interrogation systems using other forms of tunable bandpass filters for tracking the FBG wavelength     

光纤光栅应力传感器信号检测中双值问题的研究

介绍了采用匹配光纤布拉格光栅解调法(detector FBG)进行强度解调的基本原理，选择反射谱与传感光纤布拉格光栅(sensor FBG)反射谱部分重叠的解调光栅，通过探测解调光栅反射光强的变化进行解调。对这种光栅匹配解调法引起的反射光功率与应力为高斯函数而不是线性对应的问题——双值问题进行了研究，提出了一种新颖的多档光栅并联解调的解决方案，选择并联解调光栅的中心波长和带宽，从而实现所传感的应力与探测到的光功率之间的线性对应，并建立理论模型进行了模拟，从理论上进行了公式推导。最后以两档光栅并联解调为例，用实验证明了该方案切实可行，同时达到的传感范围为522με，测量精度为2．6με。     

EFPI和光纤光栅传感器混合测量技术

研究了一种对外腔式F-P干涉型(EFPI)传感器和光纤光栅(FBG)传感器进行混合测量的技术。用窄线宽的扫描光注入EFPI或FBG,通过测量FBG的反射光波长和EFPI的反射光光谱完成在同一台仪器的不同通道实现了对FBG或EFPI的同时测量。还研究了在一根光纤上同时实现FBG和EFPI测量的技术,结果表明FBG串联在EFPI前面时,可准确测量出FBG的波长和EFPI的腔长。而EFPI串联在FBG前时,只能测量EFPI,而不能完成FBG的同时测量。     

基于外差探测的双金属片结构FBG温度传感系统

提出了一种基于外差探测的双金属片结构光纤布拉格光栅(FBG)温度传感系统方案.将两个相同的FBG粘贴在膨胀系数不同的两个金属片上,利用两个金属片膨胀系数的不同,使两个FBG产生不同的中心波长的漂移,通过一个光电二极管探测其光强,再利用外差技术解调出温度的变化.与传统的双光纤布拉格光栅的系统不同的是,该系统中的参考FBG也能感测温度的变化,通过两个FBG反射波产生不同的相位差来获得温度的变化.数值仿真和理论分析表明该系统解决了传统M-Z干涉仪在测量温度时,应变与温度交叉敏感的问题.但是由于该系统的探测精度高,会导致量程范围的降低.因此该系统适用于温度变化不大,但精度要求比较高的情况.

Abstract：

Proposed is a double-sheet-metal structure FBG temperature sensor system based on heterodyne detection. Two same FBGs are affixed on two sheet metals with different coefficient of linear thermal expansion, because of which the changes of the two FBG's reflected wavelength are different, the two reflected signals are detected by a photoelectric detector, and the change of temperature can he obtained by detecting phase difference between the two reflected signals, which is different from that of traditional double FBG system. The two sheet metals make the two FBG in the same surrounding, and the two FBGs are affected by the same phase noises, which will not introduce phase difference between the two FBGs. Numerical simulation and analysis show that this system can solve the cross-sensitivity problem, but the high detection accuracy results in a narrow detection range. So the system applies to the situations which need high detection accuracy but narrow detection range.     

一种FBG靶式流量传感的结构设计及实验研究

针对传统液压系统检测中存在的传感器体积较大、测量精度不高等问题,设计了一种基于光纤Bragg光栅(FBG)的一体式靶式流量传感器。在分析FBG及靶式流量传感原理的基础上,设计一种结构紧凑、便于密封和拆装的一体式靶片,将置于流体中迎流靶片所受的与流速成对应关系的冲击力转化成FBG波长的漂移,双FBG对称粘贴于悬臂梁上下表面的中轴线上,在提高传感灵敏度的同时,有效解决了温度与应变的交叉敏感问题。通过砝码干校实验测得传感器的灵敏度为3.55pm/g,其对应的流量灵敏度为0.076L/s。实验结果表明,双FBG中心波长的变化总量与加载在靶片上的质量有良好的线性关系,灵敏度是单个FBG灵敏度的2倍,且几乎不受环境温度的影响,稳定性、可靠性较好。     

Experimental Demonstration of Multipoint Temperature Warning Sensor Using a Multichannel Matched Fiber Bragg Grating

A novel time-division-multiplexing fiber Bragg grating (FBG) sensor for multipoint temperature warning sensor is proposed and demonstrated. A multiwavelength pulsed laser based on a multichannel matched FBG is employed. The sensor array consists of multiple uniform FBGs at different positions and with different nominal wavelengths. When the temperature exceeds the threshold at a certain position, the light at the corresponding time slot and wavelength can be detected. The sensor provides a simple and flexible solution to locate the abnormal temperature increase with different tolerable thresholds at different locations.     

Absolute strain measurement using an in-fibre-Bragg-grating-basedFabry-Perot sensor

A novel method far achieving both large dynamic range and high resolution for static strain measurement is proposed and demonstrated. This method is based on the combination of two in-fibre Bragg gratings (FBG) and an all-fibre Fabry-Perot interferometric sensor (FFPI) formed by the two FBGs. The FFPI is used to carry out high-resolution strain measurement via phase detection of the interferometric signal while the wavelength shift of the two FBGs forming the FFPI is used for determining the fringe number of the interferometric signal     

基于FBG的CH4浓度传感系统

提出了一种基于光纤布拉格光栅(FBG)的新型CH4浓度传感方案.利用CH4催化元件将CH4浓度信息转化为温度信息,并映射为FBG反射波长的漂移量.将自制的FBG封装成CH4传感器,并实验获得了FBG反射波长漂移量与环境CH4浓度的曲线.验证了采用传感FBG和参考FBG的斜边检测方案可提高系统检测分辨率和温度稳定性.     

光纤光栅传感器阵列化与温度补偿研究

利用啁啾光纤Bragg光栅（FBG）反射和长周期FBG边沿滤波，提出并实现了一种综合的FBG传感快速解调方案。封装1对FBG进行应变差动传感、同时消除温度影响，不增加波长资源占用并使应变灵敏度得到有效提高，温度影响在很大范围内几乎为0。在全光纤化解调温度补偿型传感的基础上，研究了两路时分复用的设计方法，给出了时分链路间延迟光纤与光脉冲和解调端时分选通门的关系，实验结果与理论分析吻合。     

新型高速列车实时追踪系统

介绍了利用光纤光栅(FBG)波长编码的特点,采用新型分布式FBG传感实现高速列车实时追踪。其主要结构是沿线等间距设置众多具有不同中心波长的FBG传感头,当列车车轮压上传感头时,中心波长发生偏移,偏移的次数就是列车的轴数,所有传感头所计轴数应该相同,如不相同说明有车厢脱节。从车轮到达每个传感头的时间间隔,可计算出列车的运行速度、加速度,如果在整个调度区间有多趟列车,则在调度中心可精确判断每趟列车所在的位置、行进的速度、加速度和每趟列车间的距离。     

高分辨率光纤光栅温度传感器的研究

报道了一种具有高分辨率和高效且价廉的解调系统的光纤布拉格光栅(FBG)温度传感器.提出了光纤光栅的金属槽封装技术,以提高传感光栅的温度灵敏性.研究了金属槽封装光栅的温度灵敏性,理论分析和实验结果表明,封装光栅的温度灵敏系数比普通裸光栅提高了3.6倍.系统利用一长周期光栅(LPG)作为线性滤波器,宽带光源经此长周期光栅调制后入射到传感光栅,可解调布拉格传感光栅的波长位移.理论分析与实验结果一致,系统可达到的温度分辨率为0.02℃.     

Electronic technique for temperature compensation of fibre Bragg gratings sensors

Optical sensors composed of fibre Bragg gratings (FBG) are becoming a choice for a wide range of sensing applications. However, in order to manufacture temperature independent sensors, it is necessary to compensate for the intrinsic temperature dependence of the FBG. In this letter we present an extremely effective, simple and low cost novel technique for stabilising the bias point of an interrogation current amplitude detection system which uses a laser diode source and a pair of matched FBGs. An electronic feedback control circuit measures the wavelength shift due to temperature variations in a reference FBG and actuates on the laser diode temperature, to induce changes in its wavelength output and compensate for the temperature dependence of the FBG sensor.     

光纤光栅传感器温度-应变分离技术的研究

应变、温度分离是影响光纤布喇格光栅(FBG)传感器实际应用的一个重要问题.该文通过分析FBG应变、温度交叉敏感产生的原因,提出了一种基于双FBGs的用于小应变、小温度变化范围的FBG封装.其中一个FBG只感知温度,另一个FBG既受温度的影响也受应变的影响,通过结果计算就可以分离出应变、温度,而且采用温度增敏后还可以提高温度的测试精度.     

Optical fiber sensor by cascading long period fiber grating with FBG for double parameters measurement

An optical fiber sensor for strain and temperature measurement based on long period fiber grating (LPFG) cascaded with fiber Bragg grating (FBG) structure has been proposed and realized both theoretically and experimentally. Theoretical analysis shows that two microstructures with similar sensitivities cannot be used for double parameters measurement. The LPFG is micromachined by the CO2 laser, and the FBG is micromachined by the excimer laser. For the validation and comparison, two FBGs and one LPFG are cascaded with three transmission valleys, namely FBG1 valley at 1 536.3 nm, LPFG valley at 1 551.2 nm, and FBG2 valley at 1 577.3 nm. The temperature and strain characteristics of the proposed sensor are measured at 45—70 °C and 250—500 με, respectively. The sensitivity matrix is determined by analyzing wavelength shifts and parameter response characterization of three different dips. The proposed optical fiber sensor based on LPFG cascaded with FBG structure can be efficiently used for double parameters measurement with promising application prospect and great research reference value.     

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。     

基于单片机实现的光纤光栅应力传感器

提出了一种用单片机控制光介质薄膜干涉滤波器探测光纤光栅波长偏移量的方法,并 构建了对外界应力实时检测的光纤光栅应力传感系统。实验中采用了一种超磁致伸缩材料(GMM) ,使光纤布拉格光栅( FBG)产生有效的B ragg波长偏移,用控制电流来调控FBG的应变和Bragg波长偏移;电流加到1A～5A之间时,反射峰的中心波长的偏移量随所加电流呈线性增加的趋势,偏移量达到1. 10nm ( 1551. 94nm～1553. 04nm) 。该系统具有对应力测量结果分辨率高、精度高等优点。     

Ultrasonic embedding of nickel-coated fiber Bragg grating in aluminum and associated sensing characteristics

Fiber Bragg Gratings (FBGs) were embedded in metal foil using ultrasonic welding processes. Ultrasonic welding embedding processes, cross-sections of welded samples, the form change and wavelength shift of the Bragg peak during the processes, as well as the sensing characters of embedded FBGs were investigated. To understand the effects of metal foil properties on fiber embedding, optical fibers were embedded in similar and dissimilar metal foil samples. In order to study the effects of protective coating properties on the embedding processes, bare fibers, chemical nickel-plated fibers and chemical-electro nickel-plated fibers were compared in the ultrasonic welding process. Results indicate that only chemical-electro plated fibers and FBGs were successfully embedded in aluminum foils due to good protection and an appropriate matrix metal. Examination of the form change and wavelength shift shows that the FBGs are preserved well after the plating and ultrasonic welding processes. Thermal sensing results show that temperature sensitivity of the FBG was enhanced after chemical-electroplating and further enhanced after embedding in aluminum, which resulted from different thermal expansion coefficients of the SiO₂, aluminum and the nickel layer. Strain sensing results show (i) the embedded FBG remains in good condition when a cyclic tensile load (0–40 N) is applied; (ii) the relationship between wavelength and the applied load shows a linear trend.     

采用掩模板制作的光纤布喇格光栅传感器

光纤布喇格光栅(FBG)是国际上光纤传感技术研究的前沿热点。在恶劣环境下对复杂结构进行变形和健康监测，具有波长编码等明显的其他传感器所没有的特点。将由光纤光栅组成的阵列埋入结构材料内部，可用来监测桥梁、大坝、重要建筑物以及船体、航天器内部的温度、应变、压力及材料结构状态的变化。该文介绍了采用掩模板制作光纤光栅传感器的原理和方法，分析了采用相位掩模法制作的分布式光纤布喇格光栅传感器的灵敏度等测量性能和噪声的随机过程特性，从而为其在船舶结构变形测量技术中的应用提供了科学依据。     

Spun FBG Sensors With Low Polarization Dependence Under Transverse Force

External perturbation such as transverse force can increase the birefringence of most fiber Bragg gratings (FBGs). As a result, the interrogation accuracy of an FBG-based sensor may be significantly deteriorated due to an uncertain wavelength shift caused by the variation of polarization state of the input light. In the experiments, the reflection spectra of the FBG-based strain sensors made of the spun and conventional single-mode fibers were compared under different transverse forces when the polarized and unpolarized light was injected, respectively. It is shown that the spun FBG sensors have lower polarization dependence on, and consequently stronger resistance to, transverse force than the conventional FBG sensors