Study On Demodulation Accuracy Of Grating Array Temperature Measurement System

The variation of ambient temperature will change the refractive index variation period and effective refractive index of Fiber Bragg Grating,resulting in the deviation of the central wavelength of Fiber Bragg Grating.The accurate measurement of temperature can be achieved by analyzing the wavelength deviation.The new generation of grating array fiber sensing technology adopts grating array sensor as temperature sensor,and adopts industrial wire-drawing and grating writing integrated online production technology.It is a new multi-parameter fiber sensing technology with large scale,no connection,high precision and quick response,which can be flexibly configured.Temperature sensing is one of the most important and direct application directions of the new generation grating array fiber sensing technology.This paper mainly studies the demodulation accuracy of the grating array temperature measuring system,which is determined by many factors,including the performance of the grating array thermometer,the characteristics of the grating array sensor and demodulation algorithm.This paper starts from the characteristics of grating array sensor and demodulation algorithm,on the one hand,the relationship between the wavelength offset of the grating array sensor and the temperature change is obtained through experiments and data analysis,and the more accurate temperature sensitivity coefficient is calculated;on the other hand,on the basis of the existing demodulation wavelength algorithm,the spectral characteristics of different degrees of temperature variation are analyzed,and an optimized demodulation wavelength scheme is proposed.The demodulation accuracy is controlled within 1?,which effectively improves the demodulation accuracy of the grating array temperature measuring system.The main research contents of this paper are as follows:(1)the research status of FBG sensing technology at home and abroad is introduced,and the status of grating array temperature measuring system,the basic characteristics of FBG,FBG writing technology,FBG temperature sensing principle,FBG sensing demodulation technology,including hardware demodulation technology and software demodulation technology are deeply analyzed.(2)The temperature characteristic of grating array sensor is studied experimentally,and the relation between wavelength and temperature is obtained.And the algorithm is integrated into the self-developed verification program of temperature demodulation algorithm.Through testing,the algorithm can improve the precision of temperature demodulation system of grating array effectively.(3)The demodulation algorithm design process of grating array temperature measuring system and temperature demodulation system is introduced in detail,including spectral data collection and splicing process,In addition,noise reduction and recursive average filtering are carried out for the splicing spectrum,and then the wavelength demodulation algorithm of the grating is deeply analyzed,and the optimization algorithm is proposed based on the existing demodulation algorithm.(4)Independently developed a QT(Cross-platform C++ GUI application development framework)based verification program for temperature demodulation algorithm,which can obtain the wavelength data of grating,locate,calibrate,demodulate the wavelength and temperature data in real time.