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Research On Intensity Modulated Optical Fiber Sensor For Liquid Concentration Testing System

Posted on:2009-12-25Degree:MasterType:Thesis
Country:ChinaCandidate:J JiaoFull Text:PDF
GTID:2178360272986722Subject:Environmental Science
Abstract/Summary:PDF Full Text Request
Concentration is an important parameter of solution. At present, the detection technology for concentration requires complex or expensive experimental device. According to total reflection principle, Fresnel formula and Lambert-Beer's law, the linear relationships between the liquid concentration and refractive index, the liquid concentration and absorbance are analyzed respectively, and the negative exponent relationship between the optical leakage strength and clad liquid concentration is obtained. According to the above conclusions, the light intensity modulation is used to detect the solution concentration. The change of light intensity is measured to test solution concentration. The experiment indicates that the concentration of solution can be realized by the intensity modulated optical sensor developed here.The intensity modulation principle is chosen to develope the concentration testing system. The sensitive unit is made by welding naked optical fiber. Inserting it into testing liquid, loss of light intensity is measured and the liquid concentration is known directly. The 650nm light signal is emitted by semiconductor laser diode (LD). The total reflection of light is in the optical fiber and light is lost in the optical fiber sensitive unit before it arrives at the light detector. In the light detector, the silicon photodiode transforms the light signal into the electrical signal and the output electrical signal is measured after amplified by the LM358. In order to increase the accuracy of measurement, the digital multimeter is followed the light detector to read the voltage value directly. The results show that the performance of the optical sensor developed here can detect the liquid concentration well. A simple, fast and scatheless way to peel off the fiber cladding is also presented.The low-cost fiber optic connector is adopted to couple the optical fiber and light in order to avoid the complex calibration process of optical focusing lens. System design is simplified, and the cost is reduced. It is also found that the liquid detection system has reliability, stability, high sensitivity, anti-electromagnetic interference, corrosion resistance, simple structure, small size, light weight, minimum invasion, etc. Good prospects of application are showed.
Keywords/Search Tags:Liquid concentration, Total reflection principle, Fresnel formula, Lambert-Beer's law, Optical fiber sensor, Intensity modulation
PDF Full Text Request
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