基于反射光谱特征辨识的光纤气压与温度集成监测方法

针对飞行器机载环境多参量综合测试需求，研究了一种基于反射光谱特征辨识的光纤布拉格光栅(FBG)气压与温度集成监测方法，给出了基于膜片式结构的双参量传感机理及其理论模型。采用基于耦合模理论的OptiGrating软件，得到不同气压与温度条件下光纤布拉格光栅传感器仿真反射光谱。在此基础上，借助弹塑性和恢复性能优良的平膜片感压机构，构建了膜片式双光纤气压/温度集成监测模型。研究表明，恒温条件下应变传感光纤光栅反射光谱随气压增加而逐渐向短波方向偏移，其中心波长灵敏度约为0.803 0 nm·MPa-1，且反射谱主峰及其旁瓣峰值均随气压变化呈现良好线性关系；当气压恒定而温度变化时，处于仅感温不受力状态的温度传感光纤光栅反射光谱中心波长灵敏度约为9.39 pm·℃-1；当气压与温度交叉变化时，能够实现对变温条件下的微小气压变化实时监测。传感光纤光栅受非均匀应变效应反射光谱存在一定啁啾现象，其反射光谱旁瓣峰值波长随环境温度、气压变化均会发生偏移，具有良好线性关系，且在不同气压下反射光谱对应的同一阶数旁瓣峰值幅度相等。该研究能够为航空航天器系统多物理参量在线综合测试提供有益帮助。

The Integrated Monitoring Method of Optical Fiber Gas Pressure and Temperature Based on Reflection Spectrum Characteristic Identification

Aiming at aircraft airborne environment multi-parameter comprehensive testing requirements,by analyzing the theo-ries and experimental results,a kind of fiber Bragg grating (FBG)gas pressure and temperature integrated monitoring method based on spectral reflectance characteristics identification is studied,and the dual parameter sensing mechanism as well as its the-oretical model based on the diaphragm structure are also studied in this paper.OptiGrating software based on the coupled mode theory was used to simulate the reflection spectrum of the fiber Bragg grating sensor under different pressure and temperature conditions.Therefore,the characteristics of fiber Bragg grating sensor under different pressure and temperature conditions in simulate environment appeared.On this basis,with the aid of the flat diaphragm pressure sensitive structure enjoying a excellent elasticity and recovery performance,a diaphragm type double optical fiber gas pressure/temperature integrated monitoring sys-tem was constructed,and the package of the diaphragm type double fiber optic pressure/temperature sensing model was studied. Beyond that,the performance characteristics of the sensing model was also presented.A series of data analysis of the experiment showed that the strain sensing fiber Bragg grating reflection spectrum shifted to short wavelength direction under the condition of constant temperature with the increasing of the gas pressure,and the strain sensing fiber Bragg grating reflection spectrum sensi-tivity coefficient was about 0.8030 nm·MPa-1 .The reflection spectrum peak and the sidelobe level showed a good linear rela-tionship with the pressure changing.When the air pressure was constant and temperature changed,fiber Bragg grating center wavelength sensitivity of temperature sensing fiber Bragg grating which was not affected by strain and only sensitive to tempera-ture was about 9.39 pm·℃-1 .However,when the pressure and temperature cross changed,micro pressure can be monitored in real-time under the condition of variable temperature.Fiber Bragg grating sensing by the inhomogeneous strain effect has cer-tain chirp reflection spectra,the sidelobe peak wavelength of reflection spectrum will shift because of the change of temperature and pressure,which needs measurements at any moment in accordance with the monitoring environment.It has to be noticed that the temperature and pressure both have a good linear relationship with the fiber Bragg grating reflection spectrum center wave-length,and the spectral reflectance under different air pressure corresponding to the same order number sidelobe peak amplitude is equal.The above research provides a useful help for online comprehensive test of multi physical parameters in aviation space-craft system.