利用单模光纤(SMF)中的包层模与纤芯导模之间的干涉，提出了一种基于多模-单模-多模(MSM)结构与布拉格光栅(FBG)级联可同时测量温度和折射率的传感器。基于MSM结构的干涉谱和FBG的透射峰对温度和折射率具有不同响应灵敏度的特点，利用敏感矩阵实现了对温度和折射率的同时测量。实验测得MSM结构和FBG的温度灵敏度分别为0.055 2 nm/℃和0.015 8 nm/℃，MSM结构的折射率灵敏度为109.702 nm/RIU，而FBG对折射率变化不敏感。温度和折射率的测量精度分别为 ±0.32 ℃和± 0.002 3。实验显示提出的MSM结构的温度灵敏度比单模-多模-单模(SMS)结构传感器提高了5倍，同时由于SMF中的包层模对外界环境的变化较敏感，该MSM结构也可应用于其他传感领域。

A novel fiber sensor composed of a Multi mode fiber-Single mode fiber-Multi mode fiber(MMF-SMF-MMF,MSM) structure and a Fiber Bragg Grating(FBG) was proposed for simultaneous measurement of temperature and Refractive Index(RI) based on the interference between guided mode and cladding modes of a Single Mode Fiber(SMF). Due to the different responses of the MSM structure and FBG to temperature and RI variations, the proposed fiber sensor was used to measure the temperature and the RI simultaneously by utilizing a well-conditioned sensitivity matrix equation. The experimental measurement shows that the temperature sensitivity coefficients of the MSM structure and FBG are 0.055 2 nm/℃ and 0.015 8 nm/℃, respectively. The RI sensitivity coefficient of the MSM structure is 109.702 nm/RIU, whereas the FBG is insensitive to RI change. Furthermore, obtained sensing resolution is ±0.32 ℃ for the temperature and ±0.002 3 for the RI. Experiments also indicate that the temperature sensitivity coefficient of the MSM structure is five times over that of the SMS structure. Considering that the cladding mode nature of the SMF is more vulnerable to other parameters of the surrounding medium, the MSM structure can also be applied in other sensing fields.