A Compact Refractometer With High Sensitivity Based on Multimode Fiber Embedded Single Mode-No Core-Single Mode Fiber Structure

A novel refractometer based on multimode fiber (MMF) embedded single mode-no core-single mode (ME-SNS) fiber structure is presented and investigated in detail. The ME-SNS structure has a higher refractive index (RI) sensitivity because of the stronger evanescent field generated by RI modulation. There is an obvious attenuation dip when 3 segment MMFs are embedded in single mode-no core-single mode (SNS) fiber structure. Total length of sensing unit is only 1.8 mm. Experimental results show that the maximal RI and the temperature sensitivity of the ME-SNS fiber structure are 567.158 nm/RIU and 0.009 nm/°C.