Super-High Sensitivity of Fiber Temperature Sensor Based on Leaky-Mode Bent SMS Structure

A simple temperature sensor based on a bent single mode-multimode-single mode (SMS) fiber structure fixed on a polymer plate frame is proposed and experimentally investigated. The cladding of the multimode fiber in SMS is substituted with an E7 whose refractive index is a little higher than that of the core of the fiber. This construction brings two characteristics for the sensor: one is the leaky mode interference of the multimode fiber and the other is the preset curvature of the bent SMS fiber. When the temperature rises, the curvature of the SMS fiber is altered through the expanding of the polymer plate frame. The shift of central wavelength is observed on the output spectra of the fiber sensor along with temperature changing in the range from 51
^°
C to 65
^°
C. The proposed fiber sensor offers sensitivity of 6.5 nm/
^°
C, which is significantly higher than that of a normal straight SMS structure or a grating-based fiber structure.