低温环境下光纤光栅啁啾异常现象研究

Abnormality of Fiber Bragg Grating Spectrum at Cryogenic Temperatures

研究了光纤光栅的低温传感性能,在液氮温度下,带涂覆层的光纤光栅易出现啁啾异常现象,而裸光纤光栅无啁啾现象,说明光纤光栅低温啁啾的形成机理与光纤本身的光学性质无关,而在于力学机制。使用合适的低温胶粘剂将裸光栅粘贴到聚合物基底材料上,可大大减少光纤光栅在低温出现的啁啾现象;通过将基片封装光纤光栅粘贴到金属试件上进行液氮温度下的拉伸试验,获得了良好的低温应变响应特性。结合光纤光栅传感器的应变传递特性和光的干涉理论,对光纤光栅低温啁啾现象的形成机理进行了合理的解释。

Sensing characteristics of fiber bragg grating（FBG） at cryogenic temperature were investigated.It was found that the reflected spectrum of coated FBG was easy to be chirped and that of bare FBG could be normal,which indicated that the FBG chirping at liquid nitrogen temperature was caused by mechanical mechanism rather than optical mechanism.Bare FBG was bonded onto a polymer substrate by a certain cryogenic adhesive,and then metal specimen bonded with a FBG sensor was employed for tensile tests at liquid nitrogen temperature.The experimental results indicated that the FBG chirping can be greatly reduced and well strain characteristics can be obtained at cryogenic temperature of the FBG sensor packed with a polymer substrate.The FBG chirping mechanism at cryogenic temperature was explained with the theories of strain transferring of FBG sensors and interference of light.