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The Research Of Linear Photodetector To Fiber Grating Demodulation System

Posted on:2010-10-28Degree:DoctorType:Dissertation
Country:ChinaCandidate:J TaoFull Text:PDF
GTID:1118360302981981Subject:Information and Communication Engineering
Abstract/Summary:PDF Full Text Request
The thesis focuses on the study on demodulation system of fiber Bragg grating (FBG) sensors with linear CCD. Since emerged in the late of 1970's, as an optical filter, FBG has been widely applied to optical fiber communications. Also it has been applied to optical fiber sensors and optical measurements because it is sensitive to strain and temperature. FBG sensor is a kind of wavelength-encoded optical sensor. And it has all the advantages normally attributed to optical sensor, such as light weight, small size, high sensitivity, etc. In addition, the FBG sensor is sensitive to the power fluctuation of the light source and easily multiplexed along a single fiber. It also uses the absolute measurement method. Although fiber grating sensor utilize the wavelength measurement method to sense the parameters such as strain, temperature, pressure and etc. The demodulation technique of the distributed fiber grating sensing will be critical when multi-parameters and multiple sensors. The demodulation system is also a very important part in the fiber Bragg grating sensing system. Based on the traditional CCD sensing demodulation method, we mainly focus on the discussion and the research of the internal construction of CCD sensing system and related signal processing issue by using the FBG as the research object. We built a FBG sensing system based on the near infrared CCD sensing demodulation method and analyzed the demodulation characteristics of this system. The details are described as follows:1. Generally introduce the present situation and development of fiber grating sensing technique and the principle and character of the usual demodulation technology. Especially introduce the demodulation technology based on the CCD sensing, and analyze the disadvantage of the fiber grating sensing which use the visible light CCD.2. Research in details of the main parts of the fiber grating sensing system:sensing part and signal processing part. And analyze the key devices:FBG, volume phase grating and linear CCD. Research the spectrophotometry principle of the phase grating and the sensing principle and the structure of the liner CCD by analyzing the FBG sensing characteristics, find solutions of the type choice of volume phase grating and sensor used in the FBG demodulation system.3. The data processing technique for fiber grating sensing system based on CCD sensor is presented and the data information collected from the fiber grating sensor array is proposed with the technique. Build two models:the model of fiber Bragg grating reflection wavelength and the pixel position, the model of intensity and pixel size. It advanced the method of improvement the localization precision of the spectrum peak. Adopt the signal processing algorithm to eliminate the noise and the background signal and solve the problem of low space differentiation rate of system.4. Using the demodulation method based on the near infrared CCD sensing technology, it build the fiber Bragg grating sensing demodulation system based on the volume phase grating and linear InGaAs sensor with WDM and TDM. Process the system output signal by DSP and design the related data collection software. The demodulation system not only has small size, high speed, but also has high repeatability and reliability. As a conclusion, it shows a good prospect.
Keywords/Search Tags:fiber grating sensing, linear CCD, spectrum peak, demodulation system, signal processing
PDF Full Text Request
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