金属涂层SPR的单端面LPFG折射率传感器

提出了一种新型的单端面反射的镀有金属膜的长周期光纤光栅传感器.这种基于表面等离子体谐振的具有三层结构的传感器分为两个部分,光栅部分用连续CO2激光脉冲制作,金属膜是由真空镀膜制成.在光栅上镀上各种不同厚度的薄金属膜来激发表面等离子体波,用这种光纤光栅传感器来测量液体的折射率,并研究它的反射谐振谱的特性.在标准气压下,镀有80 nm银膜的光栅从水(ns=1.33)到酒精(ns=1.36)中光栅谐振波长改变了1.14nm,其敏感度达到折射率变化～5×10-4谐振波长改变20 pm.研究发现不同厚度的不同金属膜显示了不同的敏感度.通过比较光栅在空气,水,酒精,甘油,以及在它们的混合物溶液中的谐振波长,得到这种反射式的长周期光纤光栅传感器的敏感特性.为制作一种高性能的用来测量折射率的光纤光栅传感器提供了一个有益的参考.     

光纤布拉格光栅应变传感器的低温特性

研制了一种新颖的菱形光纤布拉格光栅（FBG）低温传感器。采用有限元方法分析了这种结构的力学性能和温度特性。将该装置置于低温（液氮）拉伸设备中，实验研究了这种封装形式的低温应变特性。采用光纤布拉格光栅网络分析仪和低温应变仪，分别测量了液氮温度下菱形应变传感器的波长变化量和应变变化值，测得其应变系数为-0．7185μe／pm，线性度达到0．9998。     

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LPFG微弯特性的高精度位移检测系统

在研究长周期光纤光栅(LPFG)温度及微弯特性的基础上,通过引入聚合物温度增敏封装后的光纤布拉格光栅(FBG)作为解调滤波器,搭建了温度自补偿微位移检测系统.将LPFG粘贴于试件上进行微弯测试,在固定波长处.其插入损耗的变化与弯曲度变化呈线性关系.为解决LPFG带宽宽、谐振波长难以精确测量的问题,选择特定波长的FBG作为滤波器,实现了位移检测系统的功率化解调.同时,对FBG利用聚合物进行了温度增敏封装,使其温度灵敏度与LPFG尽量相同,消除了温度对系统的影响.试验结果表明,传感系统输出的光功率与微位移呈良好的线性关系,位移灵敏度为2μW/mm,分辨力为0.5×10-2 mm.所设计的系统结构简单、灵敏度高、线性度好,不受外界温度干扰.     

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。     

光纤布拉格光栅温度传感特性与实验研究

从光纤布拉格光栅温度传感模型出发,对光纤布拉格光栅温度传感的理论进行了分析,并通过实验对裸光栅的温度特性进行了研究,推导出了光纤布拉格光栅温度传感的一阶有效线性灵敏度系数的解析式.实验结果表明,光纤光栅在所测温度范围内具有良好的线性特性,与理论结果基本一致.表明光纤光栅温度传感的理论模型具有良好的实验基础.     

光纤布拉格光栅温度传感特性与实验研究

从光纤布拉格光栅温度传感模型出发,对光纤布拉格光栅温度传感的理论进行了分析,并通过实验对裸光栅的温度特性进行了研究,推导出了光纤布拉格光栅温度传感的一阶有效线性灵敏度系数的解析式。实验结果表明,光纤光栅在所测温度范围内具有良好的线性特性,与理论结果基本一致。表明光纤光栅温度传感的理论模型具有良好的实验基础。     

基于FBG轴向拉力的液位测量传感器

根据光纤布喇格光栅(fiber Bragg grating,FBG)的传感原理,提出了一种基于波纹管结构的FBG液位传感器,利用补偿FBG(FBG1)与液位FBG(FBG2)具有相同的温度灵敏度进行温度补偿,将FBG2固定在波纹管内,液压产生的张力可以使波纹管的自由端产生位移,从而使固定在里面的FBG2产生轴向应变进而影响布喇格中心波长的改变.通过布喇格中心波长的改变来监测液位的变化,在40~340mm的液位变化范围内进行了实验研究.结果表明,光纤布喇格光栅中心反射波长漂移对液位呈现良好的线性关系,线性拟合度大于0.998,灵敏度为15.7pm/cm,理论测量范围可达到3m.说明通过改变波纹管的波纹数目和其他参数,可实现对传感器测量范围和灵敏度的调整,以满足各种应用场合.     

温度应变同时测量的光纤光栅系统的研究

为了同时传感温度和应变,在同一根光纤的两个不同地方写入相同的Bragg光栅,设计制成一种特殊机构的传感系统。由于测量结构特殊,两处光纤光栅的反射峰具有成比例的应变响应系数和不同的温度响应,测出温度后,应变也同时算出。实际测量表明,该系统结构简单,测量精度高,能进行实时测量。     

带温度补偿基于薄壁圆筒结构的光纤光栅压力传感器

阐述了一种带温度补偿、基于薄壁圆筒结构的高量程光纤光栅（FBG）压力传感器.薄壁圆筒直接作为弹性体,在压力作用下产生轴向位移来拉动压力敏感光纤以实现压力传感;通过被动温度补偿和残留温度效应主动实时修正来共同消除薄壁圆筒和压力敏感FBG的温度漂移;同时,对带温度补偿的FBG压力传感器的温度稳定性进行了讨论,给出了理想情况下该系统可达到的最优温度稳定性及决定因素.研究结果表明：基于30CrMiSiA材料管道结构的FBG压力传感器可以进行压力传感,其重复性为0.505 2%;回程误差为4.006%;线性度为0.285 5%;传感器精度为±2.639 8%;基于温度补偿进行温度去敏也有很好的效果,在-30～100℃范围内,该系统的温度稳定性因子为9.079 6%;随着实验温度范围减小至0～60℃,系统温度稳定性因子也减小至4.0%.     

应变传感器的稳定性

从材料力学、量子力学和电子力学方面深入探讨了造成应变传感器不稳定性的本质原因,并总结了改善应变片不稳定性常用的方法。     

Refractive index and temperature sensors based on no-core fiber cascaded with long period fiber grating

A kind of compact fibre-optic sensor based on no-core fibre (NCF) cascaded with a strong coupling long-period fibre grating (LPFG) is proposed and experimentally demonstrated. The sensing mechanism is based on the Mach–Zehnder-like interference between the core fundamental mode and cladding mode of the fibre structure. The NCF and LPFG are used as the mode exciter and combiner, respectively. Due to the particular properties of the strong coupling LPFG, the measurements of refractive index (RI) and temperature with high sensitivity are realized by monitoring the transmission spectrum with intensity and wavelength interrogation techniques, respectively. The achieved RI sensitivity reaches ?580.269 dB/RIU in the range of 1.436–1.454 and the temperature sensitivity reaches 27.2 pm/°C.     

基于超磁致伸缩材料的FBG电流传感器温度特性研究

针对基于超磁致伸缩材料的FBG电流传感器,分析了温度对传感头各个部分和整个传感头的影响,通过试验研究了FBG、Fe—Ga超磁致伸缩棒以及传感头三个部分的温度特性。结果表明,FBG的温度特性为线性,Fe—Ga超磁致伸缩棒以及传感头的温度特性整体为非线性,Fe—Ga超磁致伸缩棒的温度响应大于FBG的温度响应,传感头的温度特性主要取决于Fe—Ga超磁致伸缩棒的温度特性。在26℃到60℃范围内,根据传感头的温度特性,可采取分段补偿的方法消除温度影响,将温度特性分为线性区和非线性区两个范围,分别得到了传感头温度特性拟合方程。     

A health management algorithm for composite train carbody based on FEM/FBG hybrid method

In this study, a health management program for a composite train carbody was developed using the acquired strain distributions from fiber Bragg grating (FBG) sensor arrays. To determine appropriate locations for the FBG sensors, a finite element analysis (FEA) was executed. In this FEA, a FE model of the Korean tilting train (TTX) was used as a representative composite carbody train. The FEA results of various derailment situations and high speed operation on curved track were used as the database of each deformation case. In the last step, the health management program was produced using LabVIEW software. In this post-processing algorithm, the method of least squares was used to determine the difference between the FEA results and the acquired strains. This program shows the estimated deformations and plots of the acquired strains, as well as displaying an emergency indicator when necessary, all through post-processing of the strains. Finally, this FEM/FBG hybrid method was verified by several simulations using the reproductive sensor data.     

Refractive index sensor based on the diamond like carbon diffraction grating

In this work we present an optical refractive index (RI) sensor based on the spectral analysis of anomalies in the optical response from the diffraction grating employing polarized polychromatic light. The sensor consists of holographic diffraction grating (period 423.5 nm) coated with a thin (110 nm) SiO_x doped diamond like carbon film (DLC) that defines sensitivity of the sensor as well as the range of the spectral analysis. The deposition of the DLC film (synthesized by the direct ion beam deposition from the hydrocarbon source) has influence on the shape but not on the position of the anomalies observed in the specular reflection spectrum. From the reflection spectra the RI dispersion curve of liquid analyte-water was obtained.     

Range-expansion technology and fatigue performance study on the self-sensing steel strand with an embedded fibre Bragg grating sensor

For the protection of a fragile optical fibre with a fibre Bragg grating (FBG) sensor, the encapsulating method of embedding the FBG sensor in a longitudinal groove set in the central wire of the steel strand is presented. According to the theoretical analysis of the strain transfer and sensing capacity between the embedded FBG sensor and substrate, the requirements for the cross-sectional size of the groove and bond-length of the optical fibre to the self-sensing steel strand are discussed. A prepressure technology is proposed to overcome the problem of low ultimate tensile strain of FBGs. Experiments for range-expansion with different prepressure values were carried out. The results showed that a prepressure of 30% P_c produced the optimum range expansion of the FBG sensor with a maximum strain measurement of 12,361 με, which was 1.3 times higher than the yield strain of the strands. The analyses of the fatigue performance and static load tests on self-sensing steel strands were also carried out. The results indicated that the self-sensing steel strand exhibited good performance after fatigue loading operation of 2 million cycles with a maximum stress of 0.45 σ_b and a stress amplitude of 250 MPa. Moreover, the decrease in the monitoring strain sensitivity of the FBG was calculated to be below 3.5%, whereas the experimental data showed good linearity and repeatability. Therefore, for effective lifetime monitoring of steel strands under fatigue loading, it is suggested that the FBG sensors need to be placed under a certain prepressure before the construction and service of self-sensing steel strand.     

Study of a fiber optic humidity sensor based on agarose gel

An optical fiber humidity sensor was fabricated using a hydrophilic gel (agarose) deposited on the tapered plastic optical fiber (POF). The sensing element, agarose, can absorb and exude moisture from/to the ambience, thereby altering its refractive index and changing its ability to modulate the intensity of light that propagates through the fiber. Thus, the operating principle of the sensor is based on the intensity modulation technique, which utilizes a tapered POF probe coated with agarose that is sensitive to humidity. The POF, which was fabricated using an etching method, has a waist diameter of 0.45 mm and tapering length of 10 mm. As the relative humidity varies from 50% to 80%, the output voltage of the sensor with agarose gel of 0.5% weight content decreases linearly from 2.24 mV to 1.55 mV. The agarose-based sensor produces a sensitivity of 0.0228 mV/%, with a slope linearity of more than 98.36%. The tapered fiber with agarose gel of 1% weight content produces a sensitivity of 0.0103 mV/% with a slope linearity of more than 94.95% and a limit of detection of 2.635%, while the tapered fiber with agarose gel of 1.5% weight content produces a sensitivity of 0.0079 mV/% with a slope linearity of more than 98.53% and a limit of detection of 6.853%. The fiber with agarose gel of 0.5% weight content shows higher sensitivity compared to that of 1% and 1.5% due to the effect of pore size, which changes with concentration. The results demonstrate that agarose-based optical fiber sensors are both sensitive and efficient for economical and flexible measurements of humidity.     

基于光流传感器的视频稳像技术

针对平台运动导致的视频抖动问题,提出了一种基于光流传感器的视频稳像技术。该方案首先通过对一般光流传感器的改进,使其具有旋转运动下输出准确运动矢量的能力,然后利用光流传感器获得相邻两帧图像之间的运动矢量,并通过坐标变换计算出主相机的实时平移和旋转信息;其次,对原视频图像序列进行运动补偿,以获得稳定的图像序列,最终实现了视频稳像。实验结果表明,稳像后的图像序列与未稳像之前相比峰值信噪比提高了11.86 dB。该方案在视频抖动较大的情况下,能够明显减小图像序列的抖动现象,具有稳像效果好的特点,满足视频稳像的性能要求,对提高平台抗扰能力有着较高的实用性。