Research On Annealing Process And Dual-measure Of Temperature And Strain Fiber Sensor Based On Thermal Regeneration Grating

Fiber Bragg grating have been widely used in the field of optical fiber communication and optical fiber sensing.However,the performance of normal FBG in high temperature is poor which limits the FBG's applications in the field of high temperature environment such as aerospace,metallurgy,and petrochemical industry.The thermal regeneration grating formed by high temperature annealing has successfully achieved an operation temperature up to 1000?,making it ideal choice for high temperature sensing.In this thesis,the thermal regeneration grating was studied both theoretically and experimentally.The main work is as followed:(1)The fiber grating and the thermal regeneration grating are reviewed in the background section.And the research status and formation mechanism of the thermal regeneration grating are introduced emphatically.The sensing mechanism of temperature and strain in fiber grating and fiber interference structure are discussed.(2)We demonstrate the thermal regeneration grating written in the hydrogenated standard communication optical fibers by two annealing processes.They have higher thermal stability and better temperature resistance compared to that of the standard annealing process.The experimental result shows that thermal regeneration grating which are pre-annealed at 700? has charted a reflectivity larger than 65%.It can measure temperatures from 300? to 1100? with a temperature sensitivity of 16.1pm??(R~2>0.99.(3)We design an all-fiber sensor capable of simultaneous measurement of axial strain and temperature in a high temperature environment.It is composed of a Fabry-Perot interferometer structure(FPIS) cascaded with a fiber Bragg grating inscribed in pure-silica fiber by femtosecond laser and phase mask.The FPIS is fabricated by fusion splicing a section of simplified hollow-core fiber(HCF)between two pure-silica fiber by several electrical arc discharges.The optimized FPIS is cascaded with the seed grating and then subjected to a thermal annealing process in order to activate the thermal regeneration grating.The experimental results show that the proposed sensor can be used for simultaneous measurement of strain and temperature.The sensor temperature and strain measurement range are200-1000? and 0-800??,and d its characteristic matrix conditions for the 14.28.