镀膜长周期光纤光栅的折射率传感特性

摘要

Based on the model of triple-clad long-period fiber grating and characteristic e-quation, the refractive index sensing characteristics of the coated long-period fiber grating is studied in this paper. Conclusion is drawn that, the resonant wavelength of the coated long-period fiber grating varies with the changes of the environment refractive index, and in the variation there exists a leap. The resonant wavelength maintains the same before and after the leap: if it shifts towards the short -wave before the leap, then it will sustain in the same direction after the leap. After coated, the detected range of the LPFG refractive index would be widened, and the detecting sensibility of the coated LPFG would be at least an order of magnitude higher than it is without being coated. What's more, the closer the overlay thickness approaches to OOT, the higher the sensibility of the coated LPFG will be.%基于严格的光栅三包层模型及其色散方程,对镀膜长周期光纤光栅的折射率传感特性进行了详细的研究.研究发现,镀膜长周期光纤光栅的谐振波长随环境折射率的变化而变化,而且这种变化有一个跳跃,跳跃后的变化与跳跃前相同:如跳跃前向短波方向漂移,则跳跃后也向短波方向漂移.镀膜后,长周期光纤光栅的折射率探测范围得到拓宽,而且探测的灵敏度比没有镀膜时高一个数量级以上.薄膜厚度越接近最优厚度(OOT),镀膜长周期光纤光栅的灵敏度越高.