中文摘要：

基于光波导理论与光纤布拉格光栅（FBG）的模式耦合理论，对倏逝波FBG传感器的能量衰减特性进行了分析研究。最后得到了FBG的归一化反射率的表达式，它是外部介质折射率（SRI）和FBG纤芯直径的函数。理论仿真显示FBG归一化反射率会随着SRI增大和FBG腐蚀程度的加深而减小，呈非线性关系。实验结果也证明增大SRI（小于包层介质折射率）或者增大FBG的腐蚀程度都会使光纤纤芯中的传输能量减小，增强倏逝波与外部媒介的相互作用，从而增加传感器的灵敏度。

英文摘要：

Based on the optical waveguide theory and the mode coupling theory of fiber Bragg Grating （FBG）, the power attenuation properties of the FBG based on evanescent wave were analyzed. The normalized reflectivity of the FBG, which was the function of the surrounding refractive index （SRI） and the diameter of the FBG, was derived. The theoretical results show that the normalized refleetivity becomes smaller as the increase of the SRI and the depth the FBG. It is also proved that both the increase of the SRI and the etched depth can reduce the intensity of light propagating in the fiber and enhance the interaction between the evanescent wave and the surrounding medium, leading the sensitivity of the sensor to increase.