Effect of gamma radiation on the reflectance spectrum of fiber Bragg gratings

The effect of grating fabrication on radiation sensitivity of the fiber Bragg grating has been investigated experimentally. The FBGs were fabricated in different processes and GeO₂ concentrations. H₂-loading was applied to change the radiation sensitivity of the FBGs. The FBGs were fabricated in photosensitivity fiber and coupling single mode fiber with GeO₂ concentrations in a range from 6 to 23 mol%. The temperature sensitivity coefficient variation during radiation was studied and temperature-induced Bragg wavelength shift was compensated. 3 types mathematic model were used for fitting curve of radiation-induced Bragg wavelength shift. The lowest Bragg wavelength shift (about 13 pm after a total dose of 50 kGy) was obtained by a grating written in photosensitive optical fiber PSF-GeB-125 with 20.2 mol% GeO₂ concentration and without H₂-loading treatment.