AN OPTICAL FIBER TEMPERATURE SENSOR BASED ON AN ETHANOL FILLED FABRY-PEROT CAVITY

Optical fiber Fabry-Perot interferometers have been widely used as sensors. A novel anhydrous ethanol-filled optical fiber Fabry-Perot temperature sensor was reported in this article. Based on the characteristics of the temperature-controlling refractive index, the ethanol may serve as a sensitive medium for a sensor. According to the experimental results, the refractive index of the ethanol was changed by approximately 0.02617 when the temperature increased from 16°C to 74°C. A cavity length of 94 μm was used to demonstrate the feasibility of this sensor. The resonance wavelength of the sensor shifted about ?0.42 nm/°C. The novel optical fiber Fabry-Perot temperature sensor was simple, compact, sensitive, and immune to electromagnetic interferences.     

SIMULTANEOUS MEASUREMENT OF STRAIN AND TEMPERATURE WITH POLARIZATION MAINTAINING FIBER BRAGG GRATING LOOP MIRROR

□ A novel simultaneous method of strain and temperature measurement based on a polarization maintaining fiber Bragg grating loop mirror is proposed and demonstrated. The sensing head was composed of a fiber loop mirror and a section of fiber Bragg grating made of a polarization maintaining fiber. The Bragg wavelengths of the fiber grating in the polarization maintaining fiber were along slow and fast axis showing different sensitivities to strain and temperature with the interferometric peak wavelength of the fiber loop mirror. By monitoring the shifts of the Bragg wavelength and interferometric peak of the fiber loop mirror, with its temperature sensitivity of 0.1167 nm/°C and strain sensitivity of 0.0093 nm/μ?, a temperature measurement resolution about 0.009°C and a strain measurement resolution of 1.08 μ? was achieved theoretically and experimentally.     

液晶F-P腔中的反射相移

采用一种简化的薄膜矩阵方法,引入相移系数N的概念,分析了可调谐液晶Fabry-Perot腔(F-P腔)介质反射镜中心波长附近的反射相移色散对其调谐性能的影响。对文中给出的具体器件参数,在腔长小于5μm时,即约为3倍中心波长(1.55μm)时,受反射相位穿透深度的影响,器件的半峰值全宽(FWHM)急剧变小,自由光谱范围(FSR)将变窄;且腔长越小,影响越大。     

一种新型的高压电器温度在线测量系统

基于螺旋形液晶填充光子晶体光纤的温度传感特性,提出一种新型的高压电器温度传感器系统。该传感器系统由宽带光源、螺旋形液晶、光子晶体光纤、光纤F-P腔(Fabry-Perot cavity)滤波器、信号处理放大电路等组成。将螺旋形液晶封装在光子晶体光纤的纤芯空气孔中,利用光子晶体光纤对温度和弯曲不敏感特性以及螺旋形液晶的螺距对温度变化非常敏感的特性,传感器的选择反射光波长依赖于温度的变化,采用光纤F-P腔滤波器解调出光波长的变化,利用反射波长与温度之间的关系,实现温度的测量。测量系统选用合适液晶,可以得到不同的温度测量范围,能对高压电器温度进行在线检测,测量精度可以达到±0.1℃以内,并具有本征安全、高精度、高电绝缘和抗电磁干扰、对应变和环境光变化不敏感以及与普通传输光纤兼容性好等优点。     

Frequency selection of the radiation of a fiber laser with a reflection interferometer

This paper considers the results of using a two-mirror multiple-beam reflection interferometer (RI) which has a response function in reflection similar to the response function of a Fabry-Perot interferometer in transmission. The two-mirror cavity of the RI included two flat mirrors, one of which was highly reflective, and the other had an asymmetric coefficient of reflection from different sides. The light reflected from the RI was brought to an optical fiber through a collimator lens. The optical fiber, collimator, and RI constituted an integrated fiber RI, which was first used for continuous tuning of the wavelength of an erbium ring fiber laser with a continuous generation in the spectral range 1520–1566 nm.     

An all-fiber Fabry-Pérot interferometer for pressure sensing in different gaseous environments

A gas pressure sensor based on an all-fiber Fabry-Pérot interferometer (FFPI) is reported. The sensing head consists of a small section of silica rod spliced with a large offset between two single-mode fibers. The silica rod is used only as mechanical support so that an air cavity can be formed between both SMF. It is shown that the FFPI sensor is sensitive to gas pressure variation and when submitted to different gaseous environments, namely carbon dioxide, nitrogen and oxygen – sensitivities of 6.2, 4.1 and 3.6 nm/MPa, respectively, were attained. The refractive index change on nitrogen environment by means of gas pressure variation was also determined and a sensitivity of 1526 nm/RIU was obtained. The response of the sensing device to temperature variations in air was also studied and a sensitivity of −14 pm/°C was attained.     

法布里-珀罗光纤温度传感器的理论模型与仿真

设计了一种新型F-P(Fabry-Perot)干涉腔式温度传感器,具有高灵敏度、电绝缘性及抗电磁干扰等优点,能够胜任极端恶劣环境下的温度测量。采用腔内端面的反射光数学模型,并考虑输出光功率的线性度,对F-P传感腔初始腔长H、光纤端面反射率r的选取进行了优化设计与分析。应用有限元分析软件ANSYS对传感器的理论模型进行仿真与验证,模拟结果显示,当待测温度的变化范围为0~100℃时,干涉腔腔长随温度近似于线性变化,相应的理论灵敏度为1.636 nm/℃,精度为±0.2℃。     

膜片式微型F-P腔光纤压力传感器研究

对基于Fabry-Perot（F-P）干涉仪原理的膜片式微型光纤压力传感器的制作工艺进行了实验研究。在单模光纤端面上直接熔接外径约175μm的毛细石英管,在石英管的另一端制作敏感膜片,从而在光纤端面与膜片内表面之间形成F-P干涉腔。首先采用电弧熔接、切割、腐蚀膜片的方法制作了石英膜片式压力传感器,该传感器在0-3.1MPa压强范围内F-P腔的腔长变化灵敏度为41.09nm/MPa,压强测量分辨率681Pa,并具有很小的温度敏感系数。在30-140℃的温度范围内,温度交差敏感小于1.07KPa/℃。为了克服石英膜片减薄困难的缺点,选用聚合物材料（PSQ）作为压力敏感膜片制作了F-P传感器,室温下在0.1-2.1MPa压强范围内PSQ膜片的F-P腔长变化灵敏度达到 1 886.85nm/MPa,压强测量分辨率达到53Pa。     

Investigation of Annealing Temperature on Structural and Morphological Properties of Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanoparticles for Humidity Sensor Application

Cr₂O₃ nanoparticles have been prepared for precipitation technique at reaction temperature 50 °C. The prepared samples were annealed different temperatures at 500,700 and 1000 °C. Synthesized powders were characterized as X-ray diffraction, optical, transmission electron microscope, SEM with EDAX, humidity sensor, FTIR. The annealing temperature has been found to be playing a crucial role in the controlling particle size. XRD study shows the rhombohedral crystal structure of highly preferential orientation along (1 0 4) direction. FTIR reveals that the presence Cr–O bonds in the structure. The TEM images show that the size of NPs of Cr₂O₃ varied from 26 to 60 nm with average crystalline size 43 nm. UV–visible spectrum shows the absorption band of Cr₂O₃ nanoparticles at 400 nm. The humidity sensor of the Cr₂O₃ nanoparticles was studied by two temperature method. 1000 °C annealed Cr₂O₃ nanoparticles show better sensing properties and exhibits good linearity in response than 500 °C. SEM images show the clusters and agglomeration of nanoparticles. EDAX spectrum confirms the presence of Cr₂O₃ nanoparticles. Each samples have been characterized as sensing materials to determine relative humidity in the range of 20–90%. The humidity sensing property increased with increasing of annealing temperature and the resistance was decreased.     

紫外-真空紫外空间遥感仪器漫反射板的研究

紫外-真空紫外遥感仪器采用铝制漫反射板,传统光学研磨的漫反射板不均匀、半球反射率低、漫反射特性很差,这会影响仪器定标精度。本文提出光学研磨+化学磨砂的新工艺与检测方法,并搭建主要测试装置。测试结果表明,新工艺的朗伯余弦辐射特性得到明显改善,在0°与45°入射时归一化曲线接近标准余弦曲线;300nm处半球反射率均匀度从0.77提到到0.98;200-400nm半球反射率平均提高33%;将其应用于紫外-真空紫外遥感仪器上进行了角度响应测试,漫反射特性明显优于美国02年发射的同类仪器SBUV/2。     

Field identification and spatial determination of hazardous chemicals by Fourier transform infrared imaging

A hyperspectral imaging device is reported for the remote sensing of hazardous chemical clouds. The device, which is based on Fourier transform spectrometry, displays two-dimensional images of spatially resolved spectral information delivered from a focal-plane-array detector. An algorithm for chemical-cloud detection using the spectrum obtained by the hyperspectral imaging device was also developed. In order to promptly extract results from the large quantity of spectral information, the detection algorithm included approximate and precise detection steps. The performance of the hyperspectral imaging device was characterized in the lab and in the field using the detection algorithm. The real-time distribution of a chemical cloud was successfully observed.     

Novel torsion sensor using a polarization maintaining photonic crystal fiber loop mirror

A novel torsion sensor employing a short length of polarization maintaining photonic crystal fiber was inserted into the fiber loop mirror with an output probe. The sensing scheme was described theoretically by a Jones matrix and experimentally demonstrated. The results showed that the sensitivity of the intensity loss in response to the twist angle may be up to 0.0394 dB/° and a resolution of 0.025° was achieved. This torsion sensor is attractive due to its compact size, insensitivity to temperature, and suitability for longer distance transmission than conventional sensors.     

Simultaneous measurement of refractive index and temperature by integrating an external Fabry-Perot cavity with a fiber Bragg grating

A fiber sensor for simultaneous measurements of refractive index and temperature based on the integration of a fiber Bragg grating (FBG) with an external Fabry-Perot (F-P) cavity is presented. The fringe contrast of the interference spectrum generated by the F-P cavity is used to determine the external refractive index, while the wavelength shift of the FBG is used to measure temperature. The result showed that the refractive index and temperature sensitivity for the integrated sensor is 8.1 × 10(-6) and 0.01006 nm/°C, respectively.     

基于微纳光纤Sagnac环结构的光学电流传感器的响应特性研究

磁流体具有固体物质磁性及液体流动性的特性,且无本征矫顽力,无剩磁,磁场响应速度快,灵敏度高,将微纳光纤Sagnac环特殊的光传输性能与磁流体独特的磁光特性相结合,提出了一种基于磁流体包覆微纳光纤Sagnac环的全光纤电流传感器.理论推导了传感器的电流传感机理,设计了传感器的封装方法,并对传感器的温度特性和传感特性进行了...     

光纤法珀式SiC耐高温压力传感器的制造与测试

针对高温环境下压力参数的原位测试需求,基于碳化硅（SiC）材料优异的耐高温特性,研制了一种光纤法珀式全SiC结构耐高温压力传感器。采用超声振动铣磨的加工方法制备了表面粗糙度Ra约11.9 nm的SiC传感膜片。利用SiC晶片氢氟酸辅助直接键合技术,实现SiC传感膜片与SiC基板的高强度气密性键合。搭建了高温压力测试系统,对制备的SiC耐高温压力传感器样机进行了高温环境下的性能测试。结果表明,该传感器能够实现600 ℃高温环境下 0~4 MPa范围内的压力测量;600 ℃下传感器的压力灵敏度达到104.42 nm/MPa,具有较高的线性度,R2＞0.99。     

High sensitivity all-fiber Sagnac interferometer temperature sensor using a selective ethanol-filled photonic crystal fiber

An all-fiber Sagnac temperature sensor based on 3?dB tapered coupling and ethanol selective-filled photonic crystal fiber was demonstrated theoretically and experimentally. The ethanol selectivity-filled photonic crystal fiber has noncircular symmetry and thus exhibits birefringence. The ethanol selective-filled photonic crystal fiber, acting as the sensing element, was inserted in a Sagnac loop interferometer to measure temperature. The output spectra of Sagnac interferometer applied different temperatures were measured and analyzed. Experimental results have shown the temperature sensitivity of the Sagnac interferometer is 1.65?nm/°C in the range of 25–33°C.     

光纤傅里叶变换光谱术在光纤光栅传感解调中的应用

介绍了光纤Mach-Zehnder干涉仪的基本原理和光纤傅里叶变换光谱仪(FFTS)的结构;基于光纤Mach-Zehnder干涉仪,采用傅里叶变换光谱算法对光纤Bragg光栅传感器的波长进行了解调。宽带光源发出的光经过光纤耦合器进入光纤Bragg光栅,其反射光由耦合器返回进入到FFTS中进行测量,FFTS的最高光谱分辨率达到0.05 cm-1,即在近红外1 550 nm波长处分辨率为0.012 nm。分别对光纤Bragg光栅的应变特性和温度特性进行了测量。测量显示:光纤Bragg光栅的应变灵敏度为0.833 pm/με,温度灵敏度为19.78 pm/℃。得到的结果表明FFTS系统具有高分辨率、大测量范围的特点,可满足光纤Bragg光栅传感器波长解调的需求。     

基于LabVIEW的光纤布拉格光栅多节点应变监测技术

针对光纤光栅传感系统多节点有源地址查询技术,发展了一种基于LabVIEW软件平台的虚拟仪器,控制模拟电子开关各信道的导通时间,将来自传感光栅的脉冲信号按时序分配至各光纤光栅对应的输出信道,而且使开关动作与环行腔激光器中F-P滤波器的扫描同步。系统的测量范围为-672~672με,分辨力为5.9n,ε1540nm波长时系统传感灵敏度的实验值为1.57°/με,与理论值1.59°/με基本吻合。     

Sensitivity-optimized long-period fiber gratings for refractive index and temperature sensing

A long-period fiber grating sensor was fabricated by periodically changing the structure of single-mode fiber with an electric arc discharge technique. After the fabrication, the refractive index and temperature sensitivities were optimized by etching the cladding with hydrofluoric acid solution. The experimental results illustrate that the thinner cladding shows relatively higher refractive index and temperature sensitivities for the same order cladding mode, which are accordant with that of numerical simulation. After the long-period fiber grating was etched for 15?min, average refractive index sensitivities of 214?nm/refractive index unit (RIU) (1.3333?–?1.3931) and 1987?nm/RIU (1.4115–1.4555) were achieved. An extremely higher refractive index sensitivity of 2731?nm/RIU appears near 1.4555. By systematically studying the temperature sensing characteristic of cladding-etched long-period fiber grating in this work for the first time, the temperature sensitivity can reach as high as 144.23?pm/°C when the ambient temperature changes from 30 to 80°C. This work provides a theoretical reference for the fabrication of a high-sensitivity refractive index and temperature sensor based on arc-induced long-period fiber grating.     

微型膜结构全光纤珐珀干涉高温传感器

制作了一种微型膜结构的全光纤在线珐珀干涉式高温传感器。该传感器是在单模光纤端面依次熔接一段大芯径空芯光纤和一段研磨的多模光纤膜片而构成的,因此,温度引起的珐珀腔光程差改变量由空芯光纤的热膨胀和温度引起腔内压强改变从而改变膜片的扰度两部分组成,从而使相同温度变化下传感器的光程差变化量更大,分辨率更高。实验结果表明,在100～650℃,该传感器单位温度变化的光程差变化量约为1.029 nm,温度分辨率约为1.5℃,测量线性度约为0.996 7,且滞回小,重复性好。这种膜结构的全光纤珐珀干涉式高温传感器因其体积小,温度分辨率高,将在多点高温测量领域有好的应用前景。