报道了一种基于多模干涉理论的光纤折射率传感器,其传感器结构由两段单模光纤中嵌入一小段无包层多模光纤组成。研究了传感器的传输光谱与折射率的关系。实验结果表明,当外界折射率变化范围为1.336~1.372时,传感器获得灵敏度为5.4×10-5RIU(RIU为折射率单元)。该传感器在生物化学测量中有比较好的应用前景。 An optical fiber refractive index sensor based on multimode interference theory is reported. The sensor structure consists of two sections of single-mode fiber embedded with a small section of uncoated multimode fiber. The relationship between the transmission spectrum and the refractive index of the sensor was studied. Experimental results show that the sensitivity of the sensor is 5.4 × 10 -5 RIU (RIU is the unit of refractive index) when the refractive index of outside varies from 1.336 to 1.372. The sensor in the biochemical measurements have a better application prospects.