Research On Performance Of Ultra-high Temperature Fiber Grating

Currently,the development of fiber gratings is relatively mature,and fiber grating sensors have been used in various industries.However,in extreme environments,such as high temperature environments(greater than 300?),the research of fiber gratings has some difficulties,and it is also a hot research direction.Some theories are not yet mature,such as the theoretical model of regenerated fiber grating.However,from the perspective of combining theory and experiment,this paper deeply analyzes the grating technology and experimental results of ultra-high tenperature fiber gratings.This paper mainly carries out related research from the following four aspects.The main work is summarized asfoflows:Firstly,based on the background of the research,the development and application of ultra-high temperature fiber gratings are summarized.The types of current ultra-high temperature fiber gratings and their devetopments are introduced respectively.From the perspective of current market applications,the description of the development prospects of ultra-high tenperature fiber gratings is giveaSecondly,from the basic method research,the cotpled mode theory and transfer matrix method of fiber grating are derived in detail.The classification and main preparation methods of fiber gratings are introduced,and the fiber gratings are theoretically simulated.The reflection and transmission spectra of some fiber gratings are given,and analyze that the changes in their length and refractive index modulation depth have a certain impact on their spectra.The relationship between the peak power of the reflection of the seed grating during the annealing process and the grating erasure time and the conpletion time of the new grating growth was studied.Theoretically,the relationship between tenperature,strain and center wavelength of fiber grating is analyzed,and the relationship between temperature and strain sensitivity of fiber grating and temperature,strain and center wavelength are derived.Furthermore,from the aspect of experimental methods,the preparation method of regenerated fiber grating which can be applied in ultra-high temperature environment is introduced.The formation mechanism and preparation process of regenerated fiber grating are introduced in detail In addition,the relationship between the heat treatment tenperature of the seed grating and the peak power of the reflection,the grating erasure time and the completion time of the new grating growth was analyzed by experiments.The data was fitted by Matlab programming,and the fitting curve of the relationship between them was obtained.The high temperature annealing of the seed grating was carried out to prepare regenerated fiber grating and the temperature and strain characteristics of the seed grating were studied.In the high temperature test,the relationship between the center wavelength and temperature at different temperatures was studied,and the temperature sensitivity was obtained.In the strain test,regenerated fiber grating with different diameters were used to test the strain at different temperatures,and the strain sensitivity was calculated.It was concluded that the reduction of the cladding can increase the strain sensitivity and the temperature has little influence on the sensitivity.The mechanical strength of different gratings was quantitatively analyzed by experiments,and it was verified that the axial stress of the seed grating after the high temperature annealing was greatly reduced.