基于外差探测的双金属片结构FBG温度传感系统

Double-sheet-metal Structure FBG Temperature Sensor System Based on Heterodyne Detection

提出了一种基于外差探测的双金属片结构光纤布拉格光栅(FBG)温度传感系统方案。将两个相同的FBG粘贴在膨胀系数不同的两个金属片上,利用两个金属片膨胀系数的不同,使两个FBG产生不同的中心波长的漂移,通过一个光电二极管探测其光强,再利用外差技术解调出温度的变化。与传统的双光纤布拉格光栅的系统不同的是,该系统中的参考FBG也能感测温度的变化,通过两个FBG反射波产生不同的相位差来获得温度的变化。数值仿真和理论分析表明该系统解决了传统M-Z干涉仪在测量温度时,应变与温度交叉敏感的问题。但是由于该系统的探测精度高,会导致量程范围的降低。因此该系统适用于温度变化不大,但精度要求比较高的情况。

Proposed is a double-sheet-metal structure FBG temperature sensor system based on heterodyne detection. Two same FBGs are affixed on two sheet metals with different coefficient of linear thermal expansion, because of which the changes of the two FBG＇s reflected wavelength are different, the two reflected signals are detected by a photoelectric detector, and the change of temperature can be obtained by detecting phase difference between the two reflected signals, which is different from that of traditional double FBG system. The two sheet metals make the two FBG in the same surrounding, and the two FBGs are affected by the same phase noises, which will not introduce phase difference between the two FBGs. Numerical simulation and analysis show that this system can solve the cross-sensitivity problem, but the high detection accuracy results in a narrow detection range. So the system applies to the situations which need high detection accuracy but narrow detection range.