Sensors in Tilted Fiber Bragg Gratings via Spherical Metal-Reflective Ends

This study proposes a refractive index sensor based on tilted fiber Bragg gratings (TFBGs) that connect metal-reflective spherical ends. The proposed fabrication method enables it to reflect light to increase the overall energy spectrum. We used the end of the fiber with a spherical shape and the coating reflective metal to compare the reflective energy in TFBGs. The reflective technique was employed to deposit nickel (Ni) and silver (Ag) onto the surface of the spherical end of TFBGs to precisely form the spherical-shaped tilted fiber Bragg gratings (STFBGs). The Ni-covered NiSTFBG sensor had an average sensitivity of 8.028 nm/RIU wavelength, which is a 1.64-fold improvement. The result shows the backward reflected wave is reflected by the metal layer has improved performance for the wavelength and transmission loss via the reflected metal spherical-shaped end of tilted fiber Bragg gratings.