研究了微管内壁涂覆介质层的折射率传感灵敏度增强效应，通过建立四层环状结构模型对薄壁微管和厚壁微管进行了模式场分布和传感灵敏度仿真计算。计算结果表明涂覆高折射率介质层有效增加了微管内部的光场能量，从而增强传感灵敏度，将薄壁微管的一阶径向模式折射率传感灵敏度提高近65倍，厚壁微管高阶径向模式的折射率传感灵敏度提高近302倍。随涂覆介质层厚度的变化，厚壁微管高阶径向模式的折射率传感灵敏度变化存在多峰特点，并对该现象从几何光学的角度进行了分析。

The sensitivity enhancement effect of microtube coated with a dielectric layer on the inner surface is presented. The simulations of mode-field distribution and senstivity are carried out for thin wall microtubes and thick wall microtubes with an established four-layer ring structure model. The results show that optical field energy in the core of the microtube can be increased when a dielectric layer with high refractive index is coated on the inner wall surface of the microtube, thus the sensitivity is enhanced. The sensitivity of the 1st-order radial mode of the thin wall microtube and the high-order radial mode of the thick wall microtube are enhanced by 65 and 302 times, respectively. The refractive-index sensing sensitivity of the high-order radial mode will experience multiple peaks accompanying with the thickness change of the dielectric layer, which is analyzed from the view of geometrical optics.