Temperature-sensing characteristics of polarization-maintaining fiber Bragg grating inscribed directly by 800-nm femtosecond laser pulses

Abstract

Abstract A temperature-sensing system based on a polarization-maintaining fiber Bragg grating (PM-FBG) with dual-wavelength peaks was proposed and demonstrated experimentally. First-order bow-tie- and panda-type PM-FBGs with 3-mm gratings were inscribed by a 800-nm femtosecond laser by the point-by-point method, in which the laser was focused onto the fiber core through the fiber coating and cladding. The FBG arrays were directly fabricated by the femtosecond laser writing technique. The PM-FBGs with dual-wavelength reflection-spectrum peaks were scanned by a cost-effective interrogator system using modulated-grating Y-branch (MG-Y) tunable laser to sample the wavelength center position. In the temperature-sensing experiment, the sensitivity of the bow-tie-type PM-FBG exceeded 14 pm/°C within the 30–90 ℃ range. The proposed PM-FBGs and its interrogation system can be widely used in the field of fiber sensing and fiber laser.