Enhanced sensitivity refractive index sensor using tilted fiber Bragg grating with thinned cladding

Short-period fiber Bragg gratings with gratings planes tilted at an angle 8° corresponding to the fiber axis show core mode and a large number of cladding-mode resonances in transmission. The differences between the cladding-mode resonance and the core-mode resonance are used to detect the variation of the surrounding refractive index; this refractive index sensor is immune to temperature effects by experimental demonstrations. After the cladding of the tilted fiber Bragg grating was etched by the hydrofluoric, TFBGs with different diameters and different-order cladding modes were investigated; the sensitivity of a TFBG to the external index can be significantly improved by reducing the cladding radius. Enhanced sensitivity and accuracy are achieved when the surrounding refractive index changes between 1.333 and 1.4532.