A novel optic fiber hydrogen sensor is proposed in this paper. Two Bragg gratings with different reflectivity were written in single mode fiber with phase mask method by 248 nm excimer laser. The end-face of singe mode fiber was deposited with WO3-Pd-Pt multilayer films as sensing element. The peak intensity of low reflectivity FBG is employed for hydrogen characterization, while that of high reflectivity FBG is used as reference. The experimental results show the hydrogen sensor still has good repeatability when the optic intensity in the fiber is only 1/3 of its initial value. The hydrogen sensor has great potential in measurement of hydrogen concentration.
A fiber refractive index sensor based on porous alumina is fabricated by pasting porous alumina film with 42.36μm on single mode fiber tip using the UV-cured adhesive. Experimental results show that the proposed sensor has a very high correlation with glycerine concentration (0.0%~80.0%) with correlation coefficient of 99.771%. Its sensitivity and resolution was measure to be 99.771%, 154 nm/RIU and 1×10-4 respectively when the refractive index changes from 1.333 to 1.443.
This paper reviews the recent development of optical fiber sensors at the National Engineering Laboratory for Optic Fiber Sensing Technologies (NEL-FOST) at Wuhan University of Technology. Integration of optical fiber with sensitive thin films will new possibilities for industry application, such as optical fiber hydrogen sensors based on Pt-doped WO3 coatings, fiber humidity sensors with porous oxide coating and high-temperature sapphire fiber sensors based on multilayer coating on fiber tip. Ultra-weak FBG array with thousand of FBGs with on-line draw tower technology will enable FBG sensing network with large capacity, also improved sensing performance and mechanical stability.