Research On Sensing And Demodulation System Of Fiber Bragg Grating

Fiber Bragg Grating sensor,which uses the property that Bragg wavelength is sensitive to temperature and strain,is a new kind of fiber optic sensor.In addition to having the same function as the traditional electronic sensors,the FBG sensor also has some special characteristics such as immune to electromagnetic interference,large test range,wide dynamic range and long-stability.So it is widely applied in many fields such as the structure monitoring of large compound material and the concrete,the performance monitoring of the intelligent materials,electric power industry,fire fighting and chemical engineering etc.The demodulation technique of FBG sensor is currently a critical and difficult problem in FBG sensor technique fields,and it is also one of the current hot issues in many research organizations.As far as the demodulation technique of FBG,traditional technique of wavelength test has disadvantages such as larger volume,lower precision, higher price and being difficult to be applied in practical sensor and demodulation system. So developing higher precision and lower price demodulation device becomes the key of practical application of FBG.The sensor and demodulation system of FBG is researched in this paper,main contents include:1.The development,classification and recent research state of FBG are introduced.2.Based on analysis of sensing principle and main optical property of FBG,strain sensing model,temperature sensing model and cross-sensitivity model are presented.3.The principle and characteristics of demodulation methods are analyzed,then FBG matching demodulation based on stepping motor is introduced.The relationship between the wavelength shifts of sensing FBG and the wavelength shifts of reference FBG is studied.The relationship between luminous power and the reflected wavelength of FBG is presented.4.In order to realize high speed FBG demodulation,FBG matching demodulation system is designed which based on DSP system(including DSP,MCU and subordinate chips),including hardware and software design.5.Using the sensing signal demodulation system for FBG which is designed,the experiment for testing the strain response properties of FBG is made.Using the stepping motor,reference FBG is tuned.Sensing signal demodulation for FBG is realized. Experiment results are analyzed.The feasibility of this demodulation system is conformed.6.The reasons of low precision of FBG sensing and demodulation system are analyzed,and the improving methods are proposed.