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.     

A fiber-optic voltage sensor based on macrobending structure

We propose and demonstrate an optical voltage sensing scheme based on a macrobending optical fiber in a ratiometric power measurement system. This novel approach to sensing has not been utilized before and has the advantage that the sensor involves simple fabrication compared to existing fiber-optic voltage sensors. To prove the feasibility of such a fiber-optic sensor, a sensor for a voltage range from 0∼100 V is demonstrated, with a resolution of 0.5 V. The sensor is robust, linear, and shows a competitive measurement resolution. The sensor can be easily scaled to suit other voltage levels and be effectively combined with optical current sensors.     

Fiber-optic reflex sensor for in-line production measurement

The paper describes experiments concerning distance measurement with fiber-optic sensor and improvement of the measurement principle. The sensor probe was well-designed with a small structure and multi-function. The novel optical fiber probe arrangement as well as the possibilities of use for complex measurement problems are explained using the measurement of an internal screw thread as an example. The experimental results show that the measurement uncertainty of the thread minor diameter can reach ±10 μm, and the stability of the measurement system is better than 0.07%.     

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.     

Applications of angled-mirror in fiber-optic sensors

An angled-mirror as fiber-optic sensor's reflective modulator is introduced. This paper reports two optical-fiber sensors based on the angled-mirror reflective modulator. One is fiber-optic sliding sensor, the other is called fiber-optic three-states-position sensor.     

基于薄芯光纤模态干涉技术的曲率光纤传感器

提出了一种新的基于薄芯光纤模态干涉技术的光纤曲率传感器。在单模光纤的中间部分插入薄芯光纤用于传感光路,没有插入薄芯光纤的单模光纤用于参考光路,以消除环境对曲率测量的影响。由于插入的薄芯光纤和单模光纤纤芯失配,导致包层的高次模被激发,并与纤芯模在单模光纤内形成干涉。当改变薄芯光纤的曲率时,沿纤芯和包层传播的模态和光纤长度会发生改变,使得干涉谷峰发生平移。将传感光纤的两端固定的平移台上,当调节平移台距离时,薄芯光纤的曲率发生改变,导致干涉谷峰向短波方向平移。通过观察谷峰的平移距离可以实现曲率的传感测量。实验表明,该装置具有低损耗、低成本和高灵敏度的特点。     

脉冲声测量技术在光纤水听器测量中的应用

本文介绍了脉冲声测量技术在非消声水池中光纤水听器测量中的应用。理论上分析了脉冲宽度的选择标准，并搭建了实验系统，对某一光纤水听器的声压灵敏度进行了测量，实验结果验证了该技术用于光纤水听器测量的可行性。     

Fabry-Perot interference-based fiber-optic sensor for small displacement measurement

A simple fiber-optic sensor based on Fabry-Perot interference for small displacement measurement is investigated both theoretically and experimentally. A broadband light source is coupled into a Fabry-Perot cavity formed by the surfaces of a sensing fiber end and the measured object. The interference signals from the cavity are reflected back into the same fiber. A small displacement via changes in cavity length can be obtained by measuring the wavenumber spacing of the interference fringes. The experimental data meet with the theoretical values very well. Given the light source bandwidth of 40 nm and the initial distance of 30 μm, the proposed displacement sensing system could achieve high resolution measurement of 16 nm.     

Determination of low-level water content in ethanol by fiber-optic evanescent absorption sensor

Evanescent field absorption spectroscopy in the infrared range of coiled fiber-optic sensor has been applied to determine the low-level water content in ethanol. Principal component regression and classical least square models have been utilized to build the calibration model and predict the water concentrations. The standard errors of predictions of water concentrations in ethanol were 3.16% and 0.42% respectively. Some methods to improve the accuracy of predicted water concentration in ethanol were suggested. The predicted concentration of water is acceptably accurate and cost-effective. The study demonstrates that the coiled fiber-optic sensor based on evanescent absorption spectroscopy is a feasible technology for prediction of the low-level water content in bio-ethanol and other industries in both on-line and remote situation.     

干涉光纤电流传感器

提出了一种新型的高压电流光纤传感器,由Sagnac干涉仪和光路构成,采用Labview编写虚拟仪器的测试端软件。该系统利用法拉第效应,借助电子电路,获得干涉后输出光强信号中一次谐波成分,就可以将高压母线中待测电流的大小和相位分量测出。由于采用的新颖的双光路设计,与通常的干涉仪相比该系统的动态测量范围扩大数百倍,而且系统不受外界缓变量的影响。     

Experimental research on a novel fiber-optic cantilever-type inclinometer

Experimental setup for tilt measurement and a novel signal detection method for demodulation of fiber Bragg grating (FBG) wavelength shift are proposed. Being attached, respectively, on the upper and lower surface of only one single pendulum-type cantilever element, only a couple of matched FBGs are used for both tilt angle sensing and wavelength shift signal demodulating. So the received light power will change due to the split of the two reflected spectra of FBGs, which corresponds to the tilt angle. In addition, the cross-sensitivity effect of FBG-based sensors will be solved automatically due to a differential signal process method. Experimental results indicate the measurement accuracy is about ± 0.03°, and measurement resolution is estimated to be about 0.002°.     

Stabilized fiber-optic extrinsic Fabry–Perot sensor system for acoustic emission measurement

A fiber-optic Fabry–Perot (F–P) acoustic emission (AE) sensor system based on an improved double wavelength stabilization technique is described. Without stabilization, the sensor system drifts out of quadrature due to the presence of low-frequency dynamic strains. The stabilization is achieved by using a dense wavelength division multiplexer (DWDM) to generate two quadrature phase-shifted output signals. An optimum model of double wavelength stabilization is established. The filtering wavelengths of DWDM are calculated using an optimization design method. The performance of the developed sensor system was verified by two preliminary tests. One was a test on the stabilization of operating point of fiber-optic F–P sensor, and other was the detection of simulated AE signals generated by the impact and pencil lead breaking. The test results demonstrate that simulated AE signals are successfully detected using this stabilized sensor system, which solves the fade-out problem.     

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.     

An investigation of a fiber-optic air-backed mandrel hydrophone

In this work, a optical-fiber air-backed mandrel hydrophone is proposed and investigated both analytically and experimentally. The two-dimensional and three-dimensional quasistatically theoretical models of the hydrophone is created and compared, and the phase sensitivity of the hydrophone is analyzed. The theoretical result of phase sensitivity with three-dimensional model is −153.3 dB re rad/μPa. Twenty-two hydrophones of this type according to the model presented are constructed and tested. The experiment results show that experimental results of mean values of phase sensitivity are about −153 ± 0.5 dB re rad/μPa and have the close agreement with the estimation of theoretical models. The size of the fiber sensor is ∅12 × 55 mm, the normal phase sensitivity achieves −308 dB re 1 μPa⁻¹, the 3 dB effective bandwidth of the frequency response is 30 kHz, and the responsivity decreases less than 0.5 dB when static pressure is 2 MPa (200 m water depth). The hydrophone is easy to constructed at low cost with simple structure, and some new type of it with the required performances could be designed according to the model presented.     

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.     

光纤式内表面检测与自适应采样方法的研究

提出一种用于复杂内轮廓表面检测的新型单模光纤传感器 ,建立了镜面反射条件下的数学模型。根据轮辐式设计的二维光纤阵列探头结构 ,不仅可以得到被测点处的高度信息 ,还可同时得到倾斜信息 ,有效地解决了高度测量时表面倾斜给测量带来的影响。能对光源波动、表面反射率变化等引起的测量信号不稳定问题起到一定的补偿作用。为了提高采样效率 ,提出了一种曲线外插估计法 ,给出下一个测量点的位置。实验结果表明该方法能够有效地应用于逆向工程中产品内表面的检测之中     

Wavelength-encoded fiber-optic temperature sensor with ultra-high sensitivity

We present in this paper a wavelength-encoded fiber-optic temperature sensor with ultra-high sensitivity. The sensor consists of a segment of multimode fiber (MMF) with a polymer cladding spliced between two single mode fibers, forming a multimode fiber interferometer. For a temperature sensor with a 55 mm long MMF and a 45 mm long polymer cladding, a temperature sensitivity of −3.195 nm/°C has been achieved over a temperature range of 10 °C which is mainly limited by the spectral range of the light source used in the experiments. It has been found that the high temperature sensitivity is mainly attributed to the high thermo-optic coefficient of the polymer cladding. Other advantages of the temperature sensor reported here include its extremely simple structure and fabrication process, and hence a very low cost.     

光纤扫描式激光光斑测量仪

 设计并开发了光纤扫描式激光光斑测量仪。光纤探头采用逐行扫描的方式对激光光斑进行扫描,采集的光信号经能量转换、数据采集,最终传输到电脑,再由软件绘制出光斑图像。针对于大口径、脉冲激光光斑的测量提出了一种快速扫描的方案,并在此基础上计算分析了仪器的测量精度和测量时间这两个重要参数。与CCD摄像法进行了对比实验研究,结果表明：相对于CCD摄像法会受到接收屏的散射及成像系统误差带来的影响;此设备采用直接测量的手段,能够更加准确地获得光斑的实际尺寸以及光斑能量的空间分布。应用该仪器成功地进行了聚焦光束传输质量的测量。     

Measurement of curvature distribution using digital speckle three-shearing aperture interferometry

Digital speckle three-shearing-aperture interferometry used for the measurement of curvature distribution fields of a deformation object is proposed for the first time. In this method, pure curvature distribution fringes without containing slope distribution fringes can be obtained by using digital speckle three-shearing-aperture interferometry. Two specklegrams, one before and the other after object deformation, are recorded by a CCD camera and stored in a computer. A 2-D fast Fourier transform (FFT) and a 2-D inverse FFT (IFFT) are performed on the two specklegrams. The subtraction of the transformed specklegrams will produce curvature distribution fringes, and the speckle noises in curvature distribution fringes can be removed after these fringes pass through low-pass filtering. Results from theory and experiments are in good agreement.     

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.