基于倾斜光纤光栅的相对湿度传感器

提出了一种基于倾斜光纤光栅(TFBG)的包层上覆盖着聚乙烯醇(PVA)的空气相对湿度传感器,成功实现了对相对湿度在20～98%RH范围内的监测。研究发现,TFBG的透射功率在20～74%RH和74～98%RH2个相对湿度区域内分别呈现不同的线性变化,敏感度分别为2.52 dBm/%RH和14.95 dBm/%RH,并且在高湿度区有更高的敏感性。     

Optical fiber relative humidity sensor using the hydroxyethyl cellulose hydrogel film

In order to demonstrate the feasibility of hydroxyethyl cellulose hydrogel as an optical fiber sensor moisture sensitive material, a new optical fiber humidity sensor based on hydroxyethyl cellulose is proposed. First, a hollow-core fiber(150μm) is fused to a single mode fiber. Second, a 10μm thick hydroxyethyl cellulose hydrogel film is coated on the end face of the hollow-core fiber. Finally, the proposed humidity sensor is placed in a constant temperature and humidity chamber for a humidity response test. Experimental results show that this sensor has good humidity response characteristics and only needs 2.75s from 35%-85% RH, with the RH sensitivity being 224.5pm/%RH. As a good moisture sensitive material, hydroxyethyl cellulose has a good application prospect in various humidity sensors.     

Characteristics of Smart Concrete with Fiber Optical Bragg Grating Sensor

Based on the adrantages of the fiber Bragg grating sensing technology, this paper presents a principle of a novel smart corwrete with fiber optical Bragg grating sensor, analyses the theory and characteristics,illustrates the key technology and method to make the fiber Bragg grating sensor for the smart concrete, and proves the feasibility with experiments.The results inlicate that the smart concrete with fiber Bragg grating sensors is feasible in the structure monitoring and damage diagnosing in the long run.     

单光纤光栅对温度与应变的同步测量

提出了一种采用单光纤布拉格光栅(FBG)进行温度与应变同步测量的新颖设计。一根FBG被分成等长的两部分,用环氧胶水涂敷在其中一部分的表面,再套上金属套管,此时可以看成具有不同的布拉格波长的2个FBG,利用它们之间不同的杨氏模量和热膨胀系数,应变和温度能够同步测量。实验结果表明,在2700με和75℃的测量范围内,可以达到约6.1με和1.0℃的应变和温度精确度,误差主要来源于光谱仪分辨率的限制和FBG其中一部分的胶水涂抹不够均匀,通过使用高分辨率的解调仪和提高胶水涂抹工艺可得到更高的测量精确度。     

光纤光栅传感器与沥青混合料协同变形分析

为研究光纤光栅传感器与基体沥青混合料间的协调变形性,采用大型有限元软件ABAQUS建立两者协调变形评价的四点弯曲加载沥青混凝土梁试件模型,分析有无传感器存在对模拟结果的影响以及不同模量的封装材料和沥青混合料组合下传感器所在区域的应变分布规律.结果表明,相同条件下高模量传感器的存在改变了梁体应力场及应变场的分布,使水平拉应力集中在传感器附近,降低了梁底拉应变和梁体应变场的整体变化幅度;传感器模量大小的变化对局部区域影响不大,但对梁整体应变分布影响较大,传感器模量的增大致使梁底水平拉应变和梁体应变场的整体变化幅度均逐渐降低,但其降低的速率在逐渐减小而趋于稳定.     

Digital monitoring for heavy duty mechanical equipment based on fiber Bragg grating sensor

The digital monitoring principle and technologies for heavy duty mechanical equipment based on fiber Bragg grating (FBG) technology are introduced in this paper. The fundamentals of new-style FBG sensing technology, including the photorefractive effect of FBG, the physical formation, and the relation between optical properties and grating parameters, are investigated. The plaster, encapsulation and distribution planning of FBG sensor (FBGS), which is used to monitor heavy duty mechanical equipment under abominable environment and extreme conditions, are also studied. In addition, theoretical and experimental researches on the strain, temperature, displacement, and stress transmission characteristics between FBGS and detection interface are presented. The principle and method for temperature compensation in non-uniformity temperature field are described in detail as well. Comparing with the traditional sensing monitoring techniques, the application of FBGS technology on digital monitoring and diagnosis for heavy duty mechanical equipment has a number of significant technical advantages and will make a new breakthrough in this field.     

光纤光栅冰力传感器的开发及应用

根据裸光纤光栅(FBG)对应变的灵敏度远高于对压力的灵敏度这一特点,设计了一种基于等强度梁结构的FBG冰力传感器,并可以通过调节封装构件的尺寸调节其测量压力的灵敏度系数。对传感器的标定结果显示,这种FBG冰力传感器的线性相关度良好,实测的灵敏度系数与理论值一致。该种传感器在冰激桥墩振动模型试验中得到了应用,成功监测了桥墩在不同冰速撞击下受到的冰力。实验表明,这种FBG传感器灵敏度高、可靠性好、对结构自身的影响很小,可直接测量冰的撞击力,适合于模型实验中的冰力监测。     

新型多模光纤光栅特性的研究

提出了一种单轴各向异性材料为包层,主轴折射率沿光栅轴线(Z轴)方向的新型多模光纤光栅模型,引入主轴折射率比参数Kcl,运用耦合模理论等方法,对此类光纤光栅的反射特性进行研究,并着重讨论了数值孔径NA与主轴折射率比参数Kcl对多模光纤光栅中低阶模式特性参数的影响。研究结果为传感、测量等领域获得新的应用提供了理论依据,可以用多模光纤光栅代替单模光纤光栅制作光纤传感器以降低成本,也可作为对光纤光栅进一步深入研究的参考。     

光纤布拉格光栅传感器拉力和温度交叉关系的研究

在光纤光栅传感器的应用中,是由拉力还是由温度引起的波长测量值的变化是很难区分的。用定义拉力和温度的相关函数方法,把温度因素从波长与温度、拉力的交叉关系中分离出来,对光纤布拉格光栅的拉力和温度之间的相关特征进行理论研究,并用实验装置进行实验数据的测定。实验中,拉力在1 000～16 000με,温度在1～30℃之间时,相关函数项的实验数据与理论计算基本一致。这样,当光纤布拉格光栅（FBG）类型的传感器被应用于探测比较大的建筑物的结构形态时,温度和拉力之间的相互影响就可以用这种方法被估算出来。     

固化于CFRP的光纤布拉格光栅应变传感特性研究

将碳纤维复合材料(CFRP)与光纤传感器相结合构成智能先进复合材料,对固化于CFRP的光纤布拉格光栅应变传感特性进行了实验研究.实验结果表明:光纤布拉格光栅B ragg波长对应变表现出很好的线性和重复性;布拉格光栅与基体材料粘结情况的好坏,对应变灵敏性与可靠性有直接影响;用电阻应变仪对布拉格光栅光纤传感器应变传感特性进行实验对比标定,得出了表征FBG性能的应变传感灵敏系数.结果表明测试数据稳定可靠,FBG光纤传感器具有优异的应变传感特性,为智能先进复合材料的研发与应用提供了重要依据.     

光纤光栅检测的锚杆拉拔实验研究

为了实现煤矿锚杆受力过程及安全状态的长期连续监测,用光纤光栅传感技术构建锚杆支护的监测系统并做了实验.在实验室模拟煤矿井下巷道锚杆支护的受力过程,使用Φ18的金属锚杆,实验拉拔载荷达到76.44kN,采用3个沿杆身安装的光纤光栅传感器测试轴向应变,1个光纤光栅端头式测力计测试锚杆端部轴力,在杆身对应位置安装3个电阻应变片,研究锚杆端部轴力和杆身应变的变化.拉拔实验表明,光纤光栅端头式测力计检测锚杆轴力与杆身光纤光栅传感器、电阻应变片测试应变结果相一致,杆身光纤光栅传感器的应变传递系数为0.879.光纤光栅端头式测力计具有可重复使用、易于安装和保护的优点.     

基于平面膜片温度压强同时测量的光纤光栅传感器

提出一种基于膜片的双光纤Bragg光栅实现温度与压强同时区分测量的光纤光栅传感器．分别将光纤Bragg光栅沿膜片的径向和环向粘贴在膜片上,当温度发生变化或者膜片受到压力作用时,都会引起光纤Bragg光栅蜂值波长偏移．由于温度的变化所引起的两栅波长偏移量是相等的,此时两光纤Bmgg光栅波长偏移量之差完全取决于膜片所受的压强,据此可以实现温度与压强的同时区分测量．该传感器线性度很好,可以用来同时区分测量温度在40～110℃,压强在0～6MPa环境中的温度和压强,其温度测量误差不大于1℃,压强测量误差不大于0．2MPa．     

光纤光栅局部受温特性分析

应用传输矩阵法建立了光纤光栅局部受温时的反射谱变化模型,并进行仿真分析。理论分析表明：当光纤光栅某段所受温度瞬态变化时,其反射谱不再保持单个谐振峰,而是产生分裂点,且分裂点波长随温度的变化呈线性、周期性移动,同时给出了分裂点波长线性、周期变化的表达式。通过实验进一步研究,实验结果和理论分析相吻合。     

基于悬臂梁啁啾调谐的光纤光栅滤波器

提出并发展了一种基于悬臂梁结构的啁啾光纤Bragg光栅(CFBG)啁啾调谐方案,获得了一系列性能优异的可调谐CFBG滤波器,包括调谐范围达到36 nm(1.8～37.8 nm)的带宽可变反射滤波器、色散在178～2 100ps/nm范围内可调的色散补偿器、基于取样CFBG或重叠写入CFBG的信道间隔可调谐滤波器等。这些FBG滤波器不但能维持较高的反射率,还能保持中心波长基本不变。     

埋入光纤布拉格光栅传感器的智能碳纤维复合塑料

根据弹性力学和边界条件,得出了光纤布拉格光栅(FBG)传感器应变测量值与基体材料实际应变的关系方程。通过裸光栅直埋基体材料界面传递的特征系数,可表征和计算FBG检测应变与测点实际应变的误差及修正系数。并对固化于CFRP的FBG变传感特性进行了实验研究。结果表明:FBGBragg波长对应变表现出很好的线性和重复性。用电阻应变仪对FBG传感器应变传感特性进行实验对比标定,得出了表征FBG性能的应变传感灵敏系数。FBG传感器具有优异的应变传感特性,为先进智能复合材料的研发与应用提供了依据。     

双膜片结构光纤光栅地震检波器低频特性的研究

提出了一种双膜片式的光纤光栅(FBG)地震检波器,此结构有效限制了检波器横向响应。对该检波器的纵向加速度灵敏度和幅频特性进行了理论分析,并指出了影响这种检波器纵向加速度灵敏度的因素。实验结果表明,该种检波器在5～200Hz频率范围内频响平坦,纵向加速度灵敏度为24.3pm/g,谐振峰在900Hz附近,与理论计算较好的吻合。     

Application of fiber Bragg grating based strain sensor in pipeline vortex-induced vibration measurement

The vortex-induced vibrations (VIV) is an important topic of study in many different scientific and engineering fields. While VIV can be of benefit in some cases, oftentimes, it is an undesirable phenomenon that can be quite dangerous. In particular for offshore pipelines, VIV can lead to fatiguing of the pipe structure and can cause disastrous consequences if left unchecked. A number of different methods have been applied to the measurement of VIV, especially for the elongated, thin cylindrical structures. The use of fiber optic fiber Bragg gratings (FBGs) in particular has gained popularity over the recent years due to their distinct properties. However, FBGs are also very fragile and are susceptible to failure when placed in harsh environments without protection. In this paper, 56 FBGs encapsulated in stainless steel tubes were applied to the measurement of VIV in a 28-m model pipeline under controlled and uncontrolled conditions. Tests show that the encapsulated sensors possessed good sensitivity as well as fatigue life (>80000 cycles). The measurements from FBGs were also high enough to allow frequency domain analysis of the pipeline VIV under the two conditions. The authors conclude that the encapsulated FBGs are a viable tool for the study of VIV in pipeline structures.     

光纤Bragg光栅光谱特性研究

根据耦合模理论得出光纤Bragg光栅的反射率表达式、Bragg光栅的反射特性、设计反射中心波长λD=2neffA.通过对Bragg光栅反射率表达式进行数值模拟,绘制在不同参数下反射率特性曲线和带宽特性曲线,并分析了反射率Rg,带宽△λ与光栅栅距A,栅长L和折射率微扰值(δneff)之间的关系,得到了它们之间的最佳配合,对制作优良特性的光栅具有指导意义.     

裸光纤光栅及其封装后的低温特性

设计了一种基于不锈钢管的小尺寸光纤光栅（FBG）温度传感器：推导了裸FBG以及不锈钢管封装的FBG温度传感器的温度敏感因素并进行了实验验证；实验研究了-70～0℃之间的裸FBG和其封装后FBG温度传感器中心波长的低温变化特性。比较了相同条件下裸光纤光栅（FBG）和不锈钢管封装的FBG温度传感器的实验结果。分析了-60℃和0℃时FBG温度传感器透射光谱图同时对波长与温度的关系曲线进行了线性拟合并得到它们在线性变化区间的温度灵敏系数KT分别为10．1pm／℃和21．3pm／℃.