Dual-Parameter Sensor Based on Tapered FBG Combined With Microfiber Cavity

A hybrid sensor based on tapered fiber Bragg grating (FBG) combined with microfiber cavity tapered FBG combined with a microfiber cavity is proposed and demonstrated in this letter. It is fabricated by taper-drawing from a normal FBG. The FBG taper and microfiber end form an interferometric cavity. Temperature and refractive index (RI) can be measured simultaneously using such a hybrid structure. The temperature and RI variation are determined by the wavelength shift and fringe contrast change, respectively, thus the temperature and RI measurement base on the proposed structure is free of cross-sensitivity intrinsically. The obtained temperature sensitivity is
${\sim}{\rm 13}~{\rm pm}/^{\circ}{\rm C}$
for temperature, whereas the RI sensitivity is
${\sim}{\rm 15}~{\rm dB}$
/RIU for the RI range from 1.33 to 1.43.