Light intensity modulation fiber-optic sensor for curvature measurement

A light intensity modulation fiber-optic sensor, which can measure curvature directly, has been developed. It is suitable for the measurement of thin, embedded or highly flexible structures. An experimental analysis on the static and dynamic characteristics of sensor has been undertaken. The results show that the output voltage has polarity and a good linear relationship with curvature when the curvature radius is larger than 60 mm. The mathematical model relating the relative output loss, parameters of sensitive zone’s configuration (depth, number, height and half angle of tooth) and bending radius is described analytically based on the geometric optics. Curvature fiber-optic sensors can be used to build a quasi-distributed fiber-optic sensor system, which can measure curvature and torsion angle simultaneously.     

Electric current measurement using fiber-optic curvature sensor

A novel fiber-optic curvature sensor, which can measure curvature directly, has been developed in recent years. The electric current measurements system based on fiber-optic curvature sensor and electromagnetic principle is developed. A fiber-optic curvature sensor is bonded to a thin-walled cantilever and two circular magnet targets with the same parameters are configured at the tip of the cantilever symmetrically. In this case, the throughput of the sensor will be changed due to the bending deformation of cantilever, which is proportional to the electromagnetic force caused by measured electric current. Direct and alternate characteristics of the proposed measurement system are studied experimentally. The results show that the measurement errors are within the range of ±5.5 mA and the corresponding accuracy is within 1% at the current measurement range from −300 mA to 300 mA, which indicate the feasibility of the proposed measurement system.     

Fabry-Perot optical fiber tip sensor for high temperature measurement

We propose a novel Fabry-Perot optical fiber tip sensor for high temperature measurement. The sensor consists of a short section of a special all-silica photonic crystal fiber spliced at one end to a silica single-mode fiber. Because of its all-silica structure, the sensor allows linear and stable measurements of temperature up to 1200 °C with a high sensitivity. The sensor is easy and inexpensive to fabricate and could find wide applications in mechanics, aeronautics, and metallurgy.     

Fiber-optic sensor for the estimation of microbial corrosion of metals

This paper presents an optical approach to estimate the degree of corrosion of metals by measuring the changes in surface texture. The principle behind this method is based on scattering of light by objects. Source fiber is used to focus the light on the biocorroded metal surface. The resultant scattered and reflected light intensities are measured individually using detector fibers placed at different angles. The degree of corrosion is estimated as a ratio of scattered and reflected light intensities of specimen surface in a relative scale from 0 to 100. The observed optical measurements correlate well with the measured corrosion rate (correlation coefficient (R²)=0.972). A consistent relationship is found between optical measurements and corrosion levels.     

基于蓝宝石晶片的光纤法布里-珀罗高温传感器

提出并研制了一种基于蓝宝石晶片的光纤法布里-珀罗(法珀)高温传感器.该传感器采用斜端面蓝宝石光纤作传输波导,蓝宝石晶片作法珀干涉仪,"陶瓷插芯-陶瓷套管"结构做为传感器的固定结构.通过傅里叶变换-最小均方差联合算法解调传感器的反射光谱,实现了20℃~1 000℃范围内的温度测量,测试准确度为±2.5℃.该传感器具有体积小、成本低、制作简单以及重复性高的优点,可用于高温环境下稳定、精确的温度测量.     

Fiber-optic distributed sensor based on phase-sensitive OTDR and wavelet packet transform for multiple disturbances location

A novel location scheme based on the wavelet packet transform (WPT) for the phase-sensitive optical time-domain reflectometry (OTDR) is proposed. The wavelet packet energy of the backscattered signal at a time interval over the sensing fiber is provided to discriminate the disturbances regions from other regions. It is insensitive to the frequency drift of the laser. The simultaneous measurement of two disturbances at 5 km and 7 km positions is achieved by the location technique based on the WPT over a 9 km monitored length with a 50 m spatial resolution even when a laser with a frequency drift rate of 230 MHz/min is utilized. During 100 times experiments the false alarm rate is only 2% and the maximum location error is 150 m.     

Fiber-optic dielectric multilayer temperature sensor: in situ measurement in vitreous during Er:YAG laser irradiation

A fiber-optic instrument for temperature measurement is presented. The sensing element consists of an optical dielectric multilayer system acting as a micro-interferometer which is deposited on a single-mode fiber tip. The sensitivity of the implemented system is theoretically derived and experimentally determined by a calibration measurement. The small size of the probe makes the system well-suited, for instance, for endoscopic in vitro and in vivo measurements in medical applications, especially in small samples. The sensor is used for the investigation of the transient thermal behavior of vitreous during Er:YAG laser irradiation in order to study the local thermal effects that are important to minimize the potential for unintentional injury in laser vitrectomy and laser vitreoretinal surgery.     

Temperature-insensitive FBG tilt sensor with a large measurement range

A novel two-dimensional tilt sensor with a large measurement range is demonstrated by using four fiber Bragg gratings (FBGs) attached on a cylindrical cantilever-based pendulum. Experimental results show that tilt accuracy of ±0.2° and resolution of 0.013° have been achieved in the range of −40°-40°. The temperature effect is automatically eliminated without additional temperature compensation elements.     

3维VSP光纤检波器井下地震采集系统

介绍了一种用于石油勘探的井下3维VSP(Vertical Seismic Profile)采集系统设计方案,实验验证该系统达到了可测量动态范围80 dB(可测量最大值与最小之比),系统采集、处理和传输的总延时低于200 ms(2 kbit/s采样率)的指标,适用于井下VSP采集.系统采用六级光纤加速度传感器组成阵列,其中每级传感器由三个麦克尔逊干涉仪构成.使用高速DSP处理芯片实现相位产生载波(Phase Generated Carrier,PGC)解调等算法以获得地震波信号;同时应用多个ARM处理器设计光纤检波器阵列控制器以及阵列内部总线.     

温度测量范围加倍的单微环传感器

本文提出了一种基于U形波导耦合单微环结构的新型SOI(绝缘体上硅)温度传感器.温度变化引起感温部位有效折射率和长度变化,导致传感器的输出光谱发生漂移.根据传输矩阵法和耦合模理论,设计了新型传感器模型,并且分析了感温部位不同时系统输出光谱特性.结果表明:当U形波导耦合单微环整体结构感温时,输出光谱无伪模,消光比达到31 dB,可作为最佳感温元件.相比于传统的双直波导耦合单微环结构,当U形波导的两个耦合点间的距离为微环周长的整数倍数时,FSR(自由光谱范围)可加倍至56 nm,灵敏度提高到89.2 pm/?C,测量范围为298—720 K,实现了SOI微环谐振器的高温测量.     

分布式光纤温度压力传感器设计

为了实现油田井下温度压力的全分布式测量,提出了一种基于光纤散射原理的分布式温度压力测量方法。该方法通过对普通光纤进行封装设计,制作成传感光纤。由于光纤传感器周围流体的温度和压力会对传感光纤内的散射光产生调制作用,通过光纤解调仪解调出光纤拉曼散射参数和布里渊散射频移就能够实现温度和压力的实时在线测量。实验结果表明:设计的分布式光纤温度压力传感器可以实现的温度测量分辨率为0.1 ℃,压力测量分辨率为0.07 MPa。基本满足油田井下温度压力测量的全分布式、实时在线、可靠性高、精度高、抗干扰能力强等要求。     

绝对重力测量中振动传感器振动补偿性能的分析

绝对重力测量的精度主要受振动噪声的限制.振动补偿是一种简单可行的振动噪声处理方法,它通过传感器探测振动噪声来对测量结果进行修正.现阶段对于不同传感器的振动补偿性能缺乏系统的分析与评估,仅停留在应用阶段.本文从理论出发分析了传感器性能对补偿效果的影响,并通过实验评估了不同振动环境下不同传感器的振动补偿性能.实验结果显示,采用低噪声地震计的振动补偿效果主要受带宽和量程的限制,在安静环境下可实现优于百微伽的单次测量标准差,但补偿效果随振动噪声高频成分的增强而降低,在动态环境下地震计则受量程限制而无法工作.采用加速度计的振动补偿效果主要受分辨率的限制,在复杂和动态环境下均可实现毫伽量级的单次测量标准差.本文为振动补偿技术应用于绝对重力测量提供了振动传感器选型的理论和实践依据,有望为振动补偿技术的进一步发展提供技术支撑.     

Novel optical sensor for simultaneous measurement of liquid concentration and temperature

The paper describes a new optical sensor for simultaneous liquid concentration and temperature measurement. Temperature-dependent semiconductor absorption at the band edge is used as the principle of the temperature measurement, and the sensor exploits beam deviation caused by refraction due to the liquid concentration at the receiving end face of the optical device. The light intensity peak value and its deviation are detected by a charge-coupled device (CCD), and then the measured optical signal is reflected by a reflecting pyramid prism. The sensor probe is composed of an intrinsically pure GaAs single crystal, a reflecting pyramid prism, a partitioned water cell. Theoretical analysis and preliminary experimental results verify the feasibility of the proposed system.     

Fiber-optic sensors for the estimation of oxygen gradients within biofilms on metals

This paper presents an optical approach to measure the oxygen gradients in biofilms grown on stainless-steel 316L. The sensor is constructed by immobilizing an oxygen-quenchable fluorophore at the tip of an optical fiber. The response time and reversibility of fiber-optic sensor have been analyzed. By mounting the optical fiber using a computerized micromanipulator, the vertical profiles of oxygen are measured with 10 μm depth resolution across biofilms on metal coupons. Steep concentration gradients of oxygen have been observed within the biofilm, both perpendicular and parallel to the metal surface. Optical response of the biofilm grown metal surface is found to be a consistent measure of the oxygen profiles within biofilms.     

一种基于电容传感器的液体密度测量电路的设计

设计了一种基于电容传感器的液体密度测量电路,介绍了设计思想和各部分的工作原理,给出了总的测量电路图.利用本电路测量相对误差在0.5%以内,具有测量准确度高、测量速度快、数字显示直读、使用简单的特点.     

基于无芯光纤的多参数测量传感器

设计并制作了一种基于单模-无芯-单模-无芯-单模光纤结构的马赫-曾德尔传感器,可用来同时测量折射率和温度.该传感器中,两处无芯光纤充当输入、输出耦合器,中间单模光纤作为传感臂.利用有限元仿真和理论分析,确定耦合器和传感臂的最优长度为15 mm.在无芯光纤中激发出的高阶模进入单模光纤的包层传输,由于倏逝场的作用,受到环境折射率和温度的影响.选取透射谱不同干涉级次的波谷作为研究对象,实现了折射率和温度的同步测量.实验结果表明:1545 nm附近干涉谷的折射率和温度灵敏度分别为–153.89 nm/RIU(refractive index unit)和0.166 nm/℃;1570 nm附近干涉谷的折射率和温度灵敏度分别为–202.74 nm/RIU和0.183 nm/℃.该传感器在实现折射率和温度同步测量的同时,仍能保持较高灵敏度,在生物医疗等方面有着较好的应用前景.     

角度型表面等离子体振荡传感器测量精度提高的新方法

设计了一种基于棱镜的角度型表面等离子体振荡自动测量系统,建立了共轴双旋转台的机械结构,提出了新型扫描的角度测量法,得到表面等离子体振荡谐振曲线。研究了影响系统多次测量一致性的因素,提出了减少采样点、提高单点数据采集次数,并采用三级变步长的测量方法,测量时间缩短至小于原来的1/10,使系统测量精度从1E 4折射率单位提高到了4E-5折射率单位。     

基于容栅传感器的试件拉伸率在线测量装置

材料力学实验中在做破坏性拉伸试验时,需要测量拉断试件的长度,但是由于拉断试件测量时断口对接不紧密,以及人为读数误差等原因造成实验结果与理论值之间存在很大的差别.对此设计了基于容栅传感器的试件拉伸率自动测量装置,数字显示读数,提高了测量精度;同时该装置可以安装在机械加工设备上进行长度在线测量,提高加工效率.     

Capacitive position measurement for high-precision space inertial sensor

Low noise position measurement is fundamental for space inertial sensors, and at present the capacitive position sensor is widely employed for space inertial sensors. The design for the possible suppression of the front-end electric noises for a capacitive sensor is presented. A prototype capacitive sensor with 2×10⁻⁶pF/Hz1/2 at frequency above 0.04 Hz is achieved and further improvements are discussed.      

同轴全息术用于粒子场测量的数值模拟

采用数值方法模拟了同轴全息术测量粒子场的过程,对两种不同的数值算法＿直接傅里叶变换算法和卷积算法,进行了分析和比较,结果表明卷积算法符合实际要求。分析了记录图像的空间频谱及其对图像采样频率的要求,得出了在记录波长、采样间隔等条件一定的情况下的最小记录距离。对于一幅512×512像素的数字图像,若像元尺寸为6.7 μm,所用光波长为532 nm,则最小记录距离为43.2 mm。在此基础上对实验记录的振幅和相位型静态粒子的数字全息图,均得到了满意的数值再现像。