Research on phase mask method-based phase-shifted fiber grating fabrication and sensing properties

In this work, a simple phase-shifted fiber grating (PSFG) inscription technique based on screening method was demonstrated, in which a standard single-mode fiber (SMF) is irradiated by 193 nm excimer laser beam (ELB) via phase mask (PM). During the inscription processes, a small segment of filament with the diameter of about 1mm was perpendicularly inserted in the exposure area to cover the SMF before the ELB is irradiated into the SMF, thus the PSFG will be inscribed. Additionally, in order to clearly observe the PSFG on the temperature and stress characteristics, the reflectance spectrums recorded by a demodulator was processed with the PC. The experimental results show that the notch wavelength has red-shift with the ambient temperature and axial stress increase, or has blue-shift with the ambient temperature and axial stress decrease. The temperature and stress responses sensitivities of the PSFG are 10.26 pm/degrees C and 1.36nm/N, in a range from 40 degrees C to 90 degrees C and from 0.2 N to 1.6 N, respectively. And the experimental results exhibited good linearity with an R-square of about 0.998 and 0.999, respectively. The PSFG fabricated by this simple and feasible method can effectively reduce the reflectance spectrum bandwidth of the fiber grating without increasing the length of the grating region or reducing the refractive index modulation depth, thus satisfying the detection of weak dynamic signals.