研究了一种基于模间干涉原理的微型椭芯保偏光纤的折射率传感特性。利用氢氟酸腐蚀的方法将椭芯保偏光纤制作成折射率灵敏的传感头，传感头可以根据控制腐蚀时间灵活控制其锥区结构。详细分析了保偏光纤内基模与一阶高次模模间干涉产生的双边瓣能量分布与被测折射率的关系，深入研究了锥区半径、工作波长对折射率灵敏度的影响。研究结果表明，光源波长为980 nm，折射率在1.39 附近时，半径为8 μm 的传感头折射率灵敏度能够达到-7.1/RIU (即归一化光强与RIU 之比，其中RIU 为单位折射率)。

The refractive index sensing characteristics of the elliptical core polarization maitaining fiber(Ecore PMF) based on intermodal interference are investigated. The refractive index sensor probe is composed with a section of E- core PMF that etached by hydrofluoric acid. And the taper structure of sensor probe can be controlled by erosion time conveniently. The relationship of the two-lobe intensity distribution produced by the intermodal interference between the basic made and the first order higher mode of PMF with the analyte refractive index is analyzed comprehensively. Furthermore, the influence of the tapered area radius and the wavelength on the refractive index sensitivity is discussed deeply. The experiments demonstrate that the refractive index sensitivity of a refractive index sensor with 8 μm tapered area radius can reach - 7.1/RIU, which means the ratio between the normalized ralue and the refractive index unit (RIU), near 1.39 refractive index, when the laser source wavelength is 980 nm.