基于多模干涉效应的单模-多模-单模(SMS)结构光纤折射率传感器通常需要进行包层腐蚀来提高灵敏度,而且易受环境温度影响。为克服SMS结构的这些不足,提出了一种新型的基于纤芯失配多模干涉的光纤折射率传感器,由单模光纤-色散补偿光纤-单模光纤(SMF-DCF-SMF)级联光纤布拉格光栅(FBG)构成,长度不超过100mm。对其灵敏度、线性范围和温度特性等进行了测试,实验结果显示在测量折射率为1.33～1.39的折射率液时,特征波长与折射率呈线性关系,灵敏度为232.8nm,级联的FBG具有良好的温度校准功能。 Single mode - multimode - single mode (SMS) fiber optic refractive index sensors based on multimode interference effects typically require cladding corrosion to increase sensitivity and are susceptible to ambient temperature. In order to overcome these shortcomings of SMS structure, a new type of fiber refractive index sensor based on core-mismatched multimode interference is proposed. It consists of single-mode fiber-dispersion compensating fiber-single mode fiber (SMF-DCF-SMF) Bragg grating (FBG), the length does not exceed 100mm. The sensitivity, linearity and temperature characteristics were tested. The experimental results show that the characteristic wavelength and refractive index have a linear relationship with the refractive index of 1.33 ~ 1.39 with a sensitivity of 232.8nm. The cascaded FBG has Good temperature calibration function.