Phase-shifted fiber Bragg grating inscription by fusion splicing technique and femtosecond laser

• Phase-shifted fiber Bragg grating inscription by femtosecond laser is proposed.
• Two or three dips are observed by controlling the laser exposure intensity and time.
• The induced refractive index modulation of 6.3×10−4 is achieved.
• These PS-FBGs show good temperature, strain and pressure characteristics.

A new method for phase-shifted fiber Bragg grating (PS-FBG) inscription in single mode fiber by fusion splicing technique and femtosecond laser is presented. The PS-FBG is produced by exposing the fusion spliced fiber with femtosecond laser through a uniform phase mask. The transmission spectrum of the PS-FBG shows a nonlinear red shift during the inscription process, and two or three main dips can be observed due to the formation of one or two FBG-based Fabry–Pérot structures by controlling the exposure intensity and time of the laser. For a peak power density of 4.8×1013 W/cm2, the induced refractive index modulation can reach to 6.3×10−4 in the fiber without sensitization. The PS-FBG's temperature, strain and pressure characteristics are also experimentally studied. These PS-FBGs can be potentially used for multiple wavelength fiber lasers, filters and optical fiber sensors.