采用轮式侧边抛磨技术对单模多模单模光纤结构的多模光纤部分进行侧边抛磨处理，研究了不同抛磨深度情况下该光纤结构对环境折射率的传感特性.结果显示，单模多模单模光纤结构的光谱特性曲线中存在多个损耗峰，这是由多模光纤中多种高阶模式相互干涉形成的.当单模多模单模光纤结构被侧边抛磨到接近纤芯时，光谱没有发生较大变化，只是各损耗峰波长发生了不同程度的漂移；但是，当抛磨掉部分纤芯时，单模多模单模光纤结构的光谱曲线发生较大变化，抛磨后单模多模单模光纤结构对外环境折射率变化敏感.当抛磨区深度为10 μm，长度为20 mm时，折射率传感器的最高灵敏度只有703.2 nm/RIU；当抛磨区深度为15 μm时，最高灵敏度为798 nm/RIU；当抛磨区深度为20 μm时, 最高灵敏度高可达1 190 nm/RIU.研究表明，通过侧边抛磨单模多模单模光纤结构可实现一种新型的光纤折射率传感器，且可通过增加抛磨深度来提高该传感器对折射率的传感灵敏度.

A new type of optical fiber refractive index sensor was reported. The partial multimode fiber of Singlemode-Multimode Singlemode (SMS) fiber structures were side polished, and then the refractive index sensing properties were analyzed. The results show that multiple loss peaks can be observed in the spectrum of the SMS fiber structures because of the mutual interference by the high order modes of multimode fiber. The spectrum of the SMS fiber structures just drift a few nanometres when the SMS fiber structures are polished to close to the core; but when being side polished to the core of the fiber, the spectrum changes dramatically. After being side polished, the refractive index resolution of the SMS fiber structures will be higher. When the polishing depth is 10 μm and the polishing length is 10mm, the refractive index sensitivity of the SMS fiber structure is 703.2 nm/RIU. When the polishing depth is 15 μm, the refractive index sensitivity of the SMS fiber structure is 798 nm/RIU. When the polishing depth is 20 μm, the refractive index sensitivity of the SMS fiber structure is up to 1 190 nm/URI. A new type of optical fiber refractive index sensor can be realized with a single side polished SMS fiber structure, and the sensitivity of the sensor can be improved by increasing the depth of polishing area.