Research On High Temperature Sensing Technique Of Fiber Bragg Grating

Fiber Bragg grating(FBG)sensors have many advantages such as electromagnetic immunity,high sensitivity,light weight,small dimension and corrosion preventive.They have been widely used in electric power,civil engineering,petrochemical industry,medical diagnosis and national defense.Ordinary FBG is difficult applying in environment exceed 300? long-term because of thermal decay effect.With the continuous development of industrial level,the monitoring of environment temperature makes higher demands in many industries.The high temperature monitor system is desiderated.Aiming at these demands,FBG high temperature sensing technology is researched in this paper.Firstly,the research status about FBG high temperature sensing is summarized.Then fundamental theory,manufacturing method and temperature sensing principle about FBG are recommended.On this basis,three parts of the main content are studied.The main content involving fabrication of high temperature regenerated FBG and study on spectral properties,packaging of high temperature FBG sensor,sensing properties,and multiplexing of multiple FBG sensors.In this paper,regenerated FBGs(RFBGs)are fabricated through high temperature annealing.The spectral curve is analyzed theoretically.Effect of different annealing temperature on RFBG is researched.And temperature stability of RFBG is researched.Packaging technique of RFBG is proposed.The high temperature FBG temperature sensors with silica-metal packaged is fabricated.And temperature properties of RFBG sensors are tested.The output curve of sensors are provided from 100? to 800?.Results show that,performance of the sensor is excellent.The deviation of stability is 0.5?(P-P)under 800?,and the repeatability is 3?(P-P).Multiplexing technology of high temperature FBG sensors are researched.Significant advantage of FBG demodulation base on optical frequency domain reflection(OFDR)technique is proposed.This system discriminate different FBGs through the position.Therefore this system has capability that achieving large-scale multiplexing.Through experimental analysis,this system has capability that multiplexing 500 FBG.The error is 0.8pm(1?)compared with sm125 demodulation instrument.