Fiber-Optic Refractive Index Sensor via Macro-Bending Tapered Waveguide

In this letter, a novel intensity modulated fiber-optic refractive index sensor is proposed based on the tapered no-cladding-double-cladding-multimode fiber structure fabricated by arc-discharged splicing technique. In order to further improve intensity response of external refractive index, the polylactic-acid based angled-package is prepared via 3D printing technique. The experimental results show that, due to the enhanced evanescent wave effect, the intensity changes are dramatically enhanced and the maximum reaches 1101.5 dB/RIU achieved by the 60-degree package, which corresponds the detection limit of
$9.07\times 10^{-6}$
RIU. Besides, the ultra-low cross-sensitivity of
$7.41\times 10^{-5}$
RIU/°C is gained owing to the tiny temperature shift of <0.1 dB/°C.