基于F-P腔和FBG的强度调制型光纤液位传感器

设计了一种用于液位测量的光纤F-P(Fabry-Perot)传感器,并从传感头的设计制作出发,讨论了提高传感器输出信号对比度的方法;测量系统采用宽带光源,解调时经FBG(Fiber Bragg Grating)反射和透射得到传感信号和参考信号,对两路光强信号进行联合处理,补偿了光源功率波动和光路损耗变化引起的不良影响,消除了强度调制型传感器的固有缺点,此方法具有结构简单、成本低的优点;该系统可进行连续测量,测量范围为0到200kPa,相当于测量水深0到20m,其分辨力小于1cm(水面高度变化),特别适合对易燃易爆的环境中的油库液位进行测量。     

Bile enterogastric reflux sensor using plastic optical fibers

Abstract

A portable optical-fiber sensor for ambulatory assessment of the enterogastric reflux, based on the optical properties of the bile, was developed. It makes use of two light-emitting diodes and of an appropriate electronic circuit that processes the signals and provides the readout on a display. A suitable probe for in vivo measurements was designed. Plastic fiber bundles are used in order to obtain probe flexibility and low price. In vivo measurements performed on different patients show the superiority of this technique over existing methods.     

Bile enterogastric reflux sensor using plastic optical fibers

A portable optical-fiber sensor for ambulatory assessment of the enterogastric reflux, based on the optical properties of the bile, was developed. It makes use of two light-emitting diodes and of an appropriate electronic circuit that processes the signals and provides the readout on a display. A suitable probe for in vivo measurements was designed. Plastic fiber bundles are used in order to obtain probe flexibility and low price. In vivo measurements performed on different patients show the superiority of this technique over existing methods.     

A smart optical liquid level sensor based on Hg cladding optical waveguide

A smart optical liquid level sensor based on the theory of connected vessels is introduced. The Hg cladding optical waveguide (HCOW) is taken as its probe, and the change of liquid level is presented by the change of the HCOW length. Both the theoretical analysis and experiments show that when the waveguide diameter and the light wavelength are certain, the optical power loss decreased linearly with the increase of the HCOW length. By detecting the power loss of HCOW, optimizing the structure of probe and selecting the appropriate apparatus for detection, the real time detection of liquid level with high precision can be got. The experimental results show that the measurement accuracy is 5.2 mm within 10 m liquid level, and its theoretical precision can be up to 0.02%.     

Fiber-optic sensor for liquid level measurement

A novel (to the best of our knowledge) liquid level sensor based on multimode interference (MMI) effects is proposed and demonstrated. By using a multimode fiber (MMF) without cladding, known as no-core fiber, liquids around the MMF modify the self-imaging properties of the MMI device and the liquid level can be detected. We show that the sensor exhibits a highly linear response with the sensing range and multiplexed operations easily controlled by just modifying the length of the no-core fiber. At the same time, we can measure the refractive index of the liquid based on the maximum peak wavelength shift. We can also use the sensor for continuous and discrete liquid level sensing applications, thus providing a liquid level sensor that is inexpensive with a very simple fabrication process.     

基于光子晶体光纤的弱压力传感器研究

利用有限元法仿真了光子晶体光纤的双折射与横向压力之间的关系,研究弱压力条件下光子晶体光栅的特性。虽然光子晶体光纤比传统的阶跃光纤对压力更为敏感,但弱压力导致的双折射变化很小,应用测量布拉格波长的变化测量压力的变化比较困难。采用偏振相关损耗来测量外界微弱压力导致的双折射变化。仿真结果表明：利用偏振相关损耗的方法,测量灵敏度可达0.75dB/MPa。     

Design and operation of a fiber optic sensor for liquid level detection

Design and construction of an optical fiber sensor for liquid level detection are reported. This sensor operates based on light intensity modulation, and such modulation results from alteration of total internal reflection into partial reflection at the interface. The modulated intensity has been measured by using a pair of fibers, one transmitting source light, another acting as receiving fiber, and a glass prism providing the total and partial reflections. During the level measurements, when a liquid in a vessel touches the 45° faces of the 45-90-45° prism, the total internal reflection is disturbed, and the reflected light is modulated. The performance of this sensor is tested with different source lights including a light emitting diode (LED), a diode laser, and a He–Ne laser. Extinction ratio has been measured for different liquids, and compared. This ratio for water using LED source is about 0.03, for diode laser is 0.006 and for He–Ne laser is 0.003. Although this device was tested as a liquid level sensor, but the distinct results obtained for samples with different index of refractions demonstrate that the reported sensor can also be used as a liquid refractometer.     

基于labview与容栅传感器的液位测控系统

根据容栅传感器的检测原理,设计了一套基于LabVIEW和容栅传感器的液位精密测控系统,精度达0.05ml。利用容栅传感器输出的电容信号经信号调理模块输入msp430单片机处理并精密控制液位,采用LabVIEW设计系统监控界面程序,实现系统数据的显示、存储、绘图以及人机控制测定仪工作等功能。可配装为数显测定仪和物体密度测量仪,人机界面良好,成本低,易推广。     

Multi-hole plastic optical fiber force sensor based on femtosecond laser micromachining

We study the theoretical and experimental effects of hole quantity and inter–inter-hole spacing on insertion loss for using femtosecond laser to make bend-sensitive multi-hole plastic optical fiber(POF), and also analyze the mechanism of bending loss in multi-hole POF. A force sensor based on bending loss of the multi-hole POF is fabricated. The measurement ranges from 0 to 65 N, and the maximum output change exceeds 15.51 dB with good linearity and repeatability, and the sensitivity is 0.24 dB/N.     

基于光纤形状改变实现的液位传感器实验

利用光纤自身形状的变化制作的传感器是一种新型液位传感器.本文介绍了光纤液位传感器的实验原理、光纤尖的制作方法,并利用光纤液位传感器实验系统测量了光纤尖在空气、甘油、酒精和水中不同位置的反射光功率.     

Microfluidic temperature sensor based on temperature-dependent dielectric property of liquid

We propose a low-cost compact microfluidic temperature sensor by virtue of the temperature-dependent permittivity of liquid. The sensor is composed of a coplanar waveguide(CPW) transmission line loaded with three resonators and a microfluidic plate with three channels. The resonant frequency of each resonator relies on the temperature-dependent dielectric property of liquid in corresponding channel, which therefore can be used to extract the temperature. The proposed sensor features a compact size and low cost since it requires only micro fluid volume instead of additional electronic components to produce significant frequency shift with changing temperature. Moreover, it exhibits decent accuracy and stability in a temperature sensing range from 30℃ to 95℃. A theoretical analysis of the sensor is provided, followed by the detailed characterization method, and a prototype is designed, manufactured, and measured to verify the theoretical analysis.     

Impulse characteristic as a response of a liquid sensor based on shear-horizontal surface acoustic waves

The feasibility of using the impulse response of a liquid sensor based on shear-horizontal surface acoustic waves to identify liquids is justified. Identification of some liquid analytes with a single-channel sensor is experimentally demonstrated. The sensor is built around a delay line based on shear-horizontal surface acoustic waves that are excited in a 36°YX LiTaO₃-Al film-SiO₂ film-molecularly imprinted polymer film layered structure. By way of example, the concentration of the morpholine impurity (molecules of which are used as a template in synthesis of this molecularly imprinted polymer) in the liquids is measured. Impulse characteristics are derived by applying the fast inverse Fourier transformation to the amplitude-frequency responses of the sensor taken in a 60-MHz wide band at a center frequency of 105 MHz. The reproducibility of results obtained using such a technique and its application are discussed.     

Preparation,surface modification and microwave characterization of magnetic iron fibers

In this paper, magnetic iron fibers of 3–10 μm diameter and an adjustable aspect ratio were synthesized successfully by a method involving pyrolysis of carbonyl under a magnetic field. A surface modification technology was also investigated. The electromagnetic parameters of the iron-fiber–wax composites were measured using the transmission/reflection coaxial line method in the microwave frequency range of 2–18 GHz. The results show that the prepared iron-fiber–wax composites exhibit high magnetic loss that can be further improved after phosphating. On the other hand, the complex permittivity was significantly decreased after phosphating. As a result, this kind of iron fiber may be useful for thin and lightweight radar-absorbing materials.     

Agile lensing-based non-contact liquid level optical sensor for extreme environments

To the best of the author's knowledge, demonstrated is the first opto-fluidic technology- based sensor for detection of liquid levels. An opto-fluidic Electronically Controlled Variable Focus Lens (ECVFL) is used to change the spatial intensity profile of the low power optical beam falling on the liquid surface. By observing, tuning and measuring the liquid surface reflected intensity profile to reach its smallest size, the liquid level is determined through a beam spot size versus ECVFL focal length calibration table. Using a 50 μW 632.8 nm laser wavelength liquid illuminating beam, a proof-of-concept sensor is tested using engine oil, vegetable oil, and detergent fluid with measured liquid levels over a 75 cm range. This non-contact Radio Frequency (RF) modulation-free sensor is particularly suited for hazardous fluids in window-accessed sealed containers including liquid carrying vessels in Electromagnetic Interference (EMI) rich environments.     

等芯径等间距三光纤补偿式位移传感器的实验研究

介绍了补偿式光纤位移传感器的结构和原理,实验测量了等芯径等间距光纤位移传感器的输出特性和位移的关系. 结果表明:2根接收光纤各自的线性范围小,补偿后的光纤位移传感器不仅能改善测量的线性度,而且能在一定程度上放大传感器的线性测量范围. 补偿式光纤位移传感器采用等芯径等距离方式可以有效地消除光源输出强度波动、表面反射率不同和光纤传输损耗对输出特性的影响.     

Pressure and temperature characterization of two interferometric configurations based on suspended-core fibers

In this work, two all-fiber interferometric configurations based on suspended core fibers (SCF) are investigated. A Fabry–Pérot cavity (FPC) made of SCF spliced in-between segments of single-mode and hollow-core fiber is proposed. The interferometric signals are generated by the refractive-index mismatches between the two fibers in the splice region and at the end of the suspended-core fiber. An alternative sensing head configuration formed by the insertion of a length of SCF as a birefringence element in a Sagnac loop interferometer is also demonstrated. In this structure, the interferometric signals are generated by interfering two counter propagating beams with different polarization states which propagate through a length of SCF as a birefringence element. The sensitivity to pressure and temperature was determined for both configurations. The results show that the pressure sensitivities are ? 4.68 × 10^? 5 nm/psi and 0.032 nm/psi for FPC and Sagnac loop interferometers, respectively. The temperature sensitivity of both structures has been obtained and the results have been discussed.     

Synthesis, characterization and fluorescence studies of a novel europium complex based sensor

A novel europium(III) complex was synthesized using TTA (α-thenoyltrifluoroacetone) as the first ligand and H₂bpdc (2,2′-bipyridine-3,3′-dicarboxylate) as the second ligand. Elemental analysis, thermal analysis, IR and UV–vis spectrum and fluorescence spectrum of the europium(III) complex were carried out. A characteristic Eu³⁺ fluorescence emission was observed in ethanol–water (1:1) solution, indicating that the complex is stable in solution and the emission of Eu(III) ions was not influenced by the water molecules. The fluorescence emission of the complex was quenched completely by the Co²⁺ and Fe³⁺ ions, but the quenched emission was recovered in the presence of glycine. Moreover, the Eu³⁺ emission was very sensitive to pH, so the complex can be used as pH-dependent fluorescence probe or chemosensors.     

基于稳态电热拉曼技术的碳纳米管纤维导热系数测量及传热研究

利用稳态电热拉曼技术测量了碳纳米管纤维对流换热环境下的导热系数. 该方法基于材料拉曼信号与温度之间的关系, 实时探测一维材料在不同电加热(内热源)下的中心点温度, 利用对流环境下的稳态导热模型推导出材料的导热系数, 实现了一维微纳材料热物性的无损化和非接触式测量. 实验发现: 碳纳米管纤维的导热系数远低于单根碳纳米管的导热系数, 但高于碳纳米管堆积床的导热系数. 这表明碳纳米管体材料的热物性主要取决于内部管束的列阵和管束间的接触热阻.     

Preparation and characterization of titania based nanowires

A new method for preparation of titania nanowires with diameter around 10 nm and length up to 2–3 μm is described. The precursor was prepared from sodium titanate by adding ethylene glycole (EG) and heating at temperature of 198°C for 6 h under reflux. The sodium titanate glycolate formed by this way aggregated into 1D nanostructures and was subsequently transformed into titania glycolate during a chemical treatment with 98% sulfuric acid. Titania nanowires with variable amount of anatase and rutile were prepared by heating to temperatures in the range 350–1000°C. The precursor as well as titania based samples were characterized by X-ray diffraction, Infrared spectroscopy, Scanning electron microscopy, High resolution transmission microscopy, Thermogravimetry, Differential thermal analysis, Evolved gas analysis and Emanation thermal analysis. The nitrogen adsorption/desorption was used for surface area and porosity determination. The photoactivity of the prepared titania samples was assessed by the photocatalytic decomposition of 4-chlorophenol in an aqueous slurry under UV irradiation of 365 nm wavelength.     

Preparation and characterization of aligned carbon nanotubes/polylactic acid composite fibers

Aligned functionalized multiwalled carbon nanotubes/polylactic acid (MWNTs-PCL/PLA) composite fibers were successfully prepared by electrospinning processing. The MWNTs bonded with the polycaprolactone chains exhibited excellent uniform dispersion in PLA solution by comparing with the acid-functionalized MWNTs and amino-functionalized MWNTs. Optical microscopy was used to study the aligned degree of the fibers and to investigate the influences of the electrodes distance on the alignment and structure of the fibers, and results showed that the best quality of aligned fibers with dense structure and high aligned degree were obtained at an electrodes distance of 3 cm. Moreover, the MWNTs embedded inside the MWNTs-PCL/PLA fibers displayed well orientation along the axes of the fibers, which was demonstrated by field emission scanning electron microscopy, transmission electron microscopy and Raman spectroscopy.