Xu Wan

Two novel methods for liquid refractive index or concentration measurement using reflex fiber optic sensors

Two novel content meters for liquid refractive index or concentration measurement are proposed based on the simple reflex fiber optic sensor configurations. One sensor exploits a reflex and concentrically arranged fiber probe structure which is very similar to the traditional intensity-modulated fiber optic displacement sensors, but the light captured by receiving fibers is modulated by the varied solute concentration, being in proportion to the liquid refractive index, instead of displacement. The other sensor works based on detecting the edge shift of the reflected light spot, which is modulated by the refractive index variation of the liquid. Theoretical analysis and simulations are carried out with the measurement range of refractive index from 1.0 to 1.5.

High-accuracy measurement of low-water-content in liquid using NIR spectral absorption method

Water content measurement technologies are very important for quality inspection of food, medicine products, chemical products and many other industry fields. In recent years, requests for accurate low-water-content measurement in liquid are more and more exigent, and great interests have been shown from the research and experimental work. With the development and advancement of modern production and control technologies, more accurate water content technology is needed. In this paper, a novel experimental setup based on near-infrared (NIR) spectral technology and fiber-optic sensor (OFS) is presented. It has a good measurement accuracy about ∓ 0.01%, which is better, to our knowledge, than most other methods published until now. It has a high measurement resolution of 0.001% in the measurement range from zero to 0.05% for water-in-alcohol measurement, and the water-in-oil measurement is carried out as well. In addition, the advantages of this method also include pollution-free to the measured liquid, fast measurement and so on.

Technology for inspecting the end face of fiber connector based on digital micro-holography

In order to meet the requirement of inspecting fiber connector end face, a new detection system based on digital holographic microscopy is designed and the method to reconstruct three- dimensional image of the end face is proposed. Experimental results show that the technology can inspect the concentricity of fiber connector end face, the ellipticity of fiber core and the cladding and other parameters. Meanwhile the three-dimensional shape of fiber connector end face can be obtained.

Study on demodulating wide range off-centering of distributed FBG by AWG

According to the deficiencies of static demodulating method of Arrayed Waveguide Grating (AWG) for Fiber Bragg Grating (FBG) reflecting wave wavelength and the characteristic of central wavelength of tunable AWG shifting with applied voltage, the dynamic demodulating method based on tunable AWG for FBGs central wavelength wide-range is presented. The experiment systems are set up with tunable AWG, adjustable voltage source, photomultiplier, data acquisition card, and computer. Experiment results show that the system can effectively resolve the problems of measurement wide-range off-centering for the FBG, and computer can real-timely report the results of off-centering of the FBG central wavelength. AWG with the 2nm channel-spacing is used to demodulate, and the off-centering range of reflecting wave wavelength of the measured FBG reach 6nm, its measurement error is less than 0.02%.

Novel detection system for micro-strain signal based on demodulation method of tilted fiber Bragg grating sensors

A research on distributed Fiber Bragg grating (FBG) demodulation system is based on tilted Fiber Bragg grating (TFBG). In order to separate temperature effect with fiber Bragg grating, we use two adjacent FBG (one used for sense, the another for reference ) which have the same central wavelength but different grating length, by parallel connection to make a sensing probe; Put the FBG keep close to equal thickness of rigidity cantilever beam of isosceles triangle, demodulate spectrum signal from sensing probe by using optical properties of main mode and side mode of TFBG and mechanical properties of cantilever. With the help of a computer to control cantilever beams cyclic oscillating and collect transmission spectrum signals of TFBG at the same time, analytical processing data for real time display of await strain. Experimental results show that it is feasible to demodulate distributed optical Fiber Bragg grating by TFBG (resolution of micro-strain is 0.009με ), which solves the cross sensitivity of temperature and strain. The system is stably and reliable, low cost.

AWG eletro-optical wavelength demodulation system without temperature effect

Based on the Arrayed Waveguide Grating (AWG) equation and output light intensity equation, dual peaks electro-optical AWG is presented, whose properties are analyzed in details in the paper. The experiments for the electro-optical dual peaks AWG are simulated by Optiwave software, and the experimental results verify the theory very well.