| Fiber Bragg grating(FBG) is a new type passive optical component with the refractive index modulated along the fiber length.It has widely applied in fiber communication systems due to its high wavelength selectivity,low insertion loss,and electromagnetism interference immunity.Recently FBG has become a very important component for optical sensing devices considering its many merits such as high sensitivity,light weight,small size,easily array and wavelength encoded,and it has become one of the most promising optical device.It is well known that the application in sensing fields such as high temperature measuring and monitoring remains a international hot.The normal measurement methods are difficult to be extended to practical applications for the expensive price and complicated production process.So it is of great significance to carry out a new method to measure high temperature with low-cast.Based on the current situation.FBG fabricated in Ge-doped single mode fiber by UV (248nm) exposure through phase mask.Got FBG1 with low-reflectivity and FBG2,FBG3 with high-reflectivity.Different refractive index of FBG1 and FBG2 sensors were monitored from 30℃to 1000℃,respectively.The experiments indicated that both FBG gratings were erased at 870℃.However,when the temperature was up to 900℃,the high-reflectivity of FBG's grating appeared refective peak again with 1 dB;moreover,the highest erasing temperature could reach to 1000℃.High-reflectivity FBG3 was monitored in the same condition.The annealed experiment got the same result.Used the annealed high-reflectivity FBG3 to monitor from 30℃to 1000℃.The temperature sensitivity is 0.02nm/℃and the linearity is 0.999.The results showed that with the annealed high-reflectivity FBG can measure the temperature rang from 30℃to 1000℃.The measuring temperature range of high-reflectivity FBG can be increased by using annealing treatment.And we could use this method fabricate the FBG sensors that can measure high temperature with low-cost. |
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