Characteristics of phase-shifted fiber Bragg grating inscribed by fusion splicing technique and femtosecond laser

Abstract

Phase-shifted fiber Bragg grating (PS-FBG) inscription in nonphotosensitive single mode fiber (SMF) by the fusion splicing technique and femtosecond laser is reported. Two SMFs are fusion spliced to introduce a refractive index modulation point which acts as a phase shift, then exposing the fusion spliced fiber with femtosecond laser and a uniform phase mask. Two dips can be observed in the transmission spectrum of inscribed grating, and the max induced refractive index modulation can reach to 4.2×10−4 without any fiber sensitization for a peak power density of 4.5×1013 W/cm2. The annealing tests show that type I PS-FBG is successfully inscribed. This type of grating also shows good strain and pressure characteristics. Such PS-FBGs can be potentially used for optical fiber lasers, filters and sensors.