Strain-Temperature Discrimination Using Multimode Interference in Tapered Fiber

Tapering single-mode-multimode-single-mode structures to enhance sensitivity is proposed and experimentally demonstrated. 50-mm-long coreless multimode fiber sections are spliced between single-mode fibers (SMFs) and tapered. They are characterized in strain, and an increase in strain sensitivity is obtained with taper diameter reduction. Sensitivities as high as -23.69pm/με for the 15-μm taper are attained. Temperature sensitivities also depend on taper diameter. A combination of two different diameter tapered SMF MMF-SMF structures, with cross-sensitivity to strain and temperature, is proposed as a sensing system for the simultaneous measurement of strain and temperature with resolutions of ±5.6 με and ±1.6°C, respectively. A good condition number of 3.16 is achieved with this sensing structure.