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

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

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.     

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.     

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.     

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.     

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.     

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.     

Design and performance of a plastic optical fiber leakage sensor

In this article design and operation of a plastic optical fiber (POF) sensor based on the unconventional light leakage from one fiber to another one causing intensity modulation are presented. The dominant loss mechanism was found to be the evanescent loss and based on this phenomenon the optical fiber sensor was designed. The penetration depth of evanescent wave as a function of different refractive index of cladding was calculated. Operation of this sensor was tested as a liquid level sensor for different liquids and the experimental results are compared. The dry (air interface layer) and wet output (liquid interface layer) signals for this probe were measured for a series of measurements and important factors concerning sensor operation are described. The precision of measured values, reproducibility of the results (1.35% error), and the stability of sensing operation as a function of time at different launching powers are also reported (0.85% error). The reported results for this design are promising and verify the successful operation of such a device as a liquid level probe and also as an on/off level switch.     

Photonic crystal sensor based on surface waves for thin-film characterization

A new sensor based on optical surface waves in truncated one-dimensional photonic crystals is proposed for use in determining the optical properties of metallic or dielectric thin films and bulk media. Specifically, the method of optical characterization takes into account the changes that the surface waves of a layered structure undergo when either a thin film of arbitrary material is added at the surface or the optical properties of transmission medium change. For the surface-wave excitation the Kretschmann configuration used in attenuated total reflectance is employed.     

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.     

Preparation and characterization of silicon oil based ferrofluid

Stable silicon oil based ferrofluid was prepared in the present investigation. Silicon oil surfactant ethoxy terminated polydimethylsiloxane was used to modify the Fe₃O₄ nanoparticles. The Fe₃O₄ nanoparticles were firstly coated with a SiO₂ layer by the hydrolysis of tetraethoxysilane. Then using the active hydroxyl groups on the surface of the SiO₂, silicon oil surfactant was covalently grafted onto the Fe₃O₄ nanoparticles surface. The ethoxy terminated polydimethylsiloxane has similar molecular chain structure and good compatibility with that of the carrier liquid, thus ensuring stable dispersion of modified Fe₃O₄ in the carrier silicon oil. The interaction between Fe₃O₄ and the modifier was characterized by IR and XPS. The crystal structure and the magnetic properties of the Fe₃O₄ nanoparticles were determined by XRD and VSM, respectively. The size and morphology of the particles were observed using TEM. The properties of the silicon oil based ferrofluid were characterized by Gouy magnetic balance. The results indicated that the ferrofluid had high magnetism and good stability. The rheological properties and thermostability of the ferrofluid were also investigated.     

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.