A sensing structure of single-multi-single (SMS) and fiber Bragg grating (FBG) cascaded is proposed using the principle of interference of higher order modes to achieve sensor measuring. Two kinds of multimode fibers with the core diameter of 50 μm and 60 μm are used with the same length. Experimental results show that the temperature sensitivities of 50 μm and 60 μm are 0.095 nm/℃ and 0. 127 nm/℃ in SMS structure. The temperature sensitivity of SMS structure has a slight increase by using large core diameter mullimode fiber. The refractive index sensitivities of 50 μm and 60 μm are 61.96 nm/RlU and 128. 11 nm/RIU in SMS structure. The refractive index sensitivity of SMS structure has a great increase by using large core diameter multimode fiber. The sensor can be used for the simultaneous measurement of temperature and refractive index.%提出一种单模-多模-单模(SMS)与光纤布拉格光栅(FBG)级联的传感结构,利用了多模光纤内的高阶模干涉原理实现传感测量.本文采用了同长度芯径分别为50μm和60μm的多模光纤.实验结果显示,在SMS结构中,芯径50 μm和60μm的温度灵敏度分别为0.095nm/℃和0.127nm/℃,采用大芯径多模光纤略有提高SMS结构的温度灵敏度;折射率灵敏度分别为61.96nm/RIU和128.11nm/RIU,采用大芯径多模光纤大大提高了SMS结构的折射率灵敏度,该传感器能够用于温度和折射率的同时测量.
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