为了提高光纤倏逝波传感器的灵敏度，该文提出了一种新型结构传感光纤。传感光纤由传统塑料光纤+新型阶跃光纤(折射率由纤芯向包层阶跃增大)+传统塑料光纤级联而成。新型阶跃光纤为倏逝波传感器的敏感区，光纤纤芯由聚甲基丙烯酸甲酯构成，包层由聚砜与GeO2混合物构成。利用几何光学分析了光纤光传输特性，实验测试了光纤光传输特性及其对外界折射率敏感特性。结果表明，当新型阶跃光纤包层中GeO2掺杂质量分数为1.5%，涂覆层厚为200 μm时，传感光纤具有较好的光谱传输质量及高的折射率响应灵敏度。

To increase the sensitivity of fiber-optic evanescent wave sensors, a sensing optic fiber with novel structure was proposed in this paper. The sensing optical fiber was by fabricated by cascading of a traditional plastic optical fiber, a novel step optical fiber (with a refractive index increasing step from the fiber core to the cladding) and another traditional plastic optical fiber together. The new step optical fiber was the sensitive area of the evanescent wave sensor. The fiber core was made of polymethyl methacrylate, and the cladding was made of a mixture of polysulfone and GeO2. The optical transmission characteristics of the prepared optical fiber were analyzed by using geometrical optics. The optical transmission characteristics and its sensitivity of the prepared optical fiber to the external refractive index were investigated. The results highlight that when the GeO2 doping content in the cladding of the new step optical fiber was 1.5 wt% and the coating thickness was 200 μm, the sensing fiber showed good spectral transmission quality and high refractive index response sensitivity.