Stress changes in H2-loaded SMF optical fibers induced by cw-Ar+ 244 nm irradiation

Bragg gratings were inscribed in H2-loaded SMF-28e optical fibers and measured for axial stress changes for various exposure doses. Mean refractive index changes as high as 7.5 × 10-3 were observed under cw-244 nm irradiation of 143 W/cm2. Bragg grating reflectivity >99% was achieved for 0.7 mm long (1/e2) gratings. Axial stress measurements realized before and after UV exposure of the fibers, show two competing dose-dependent photosensitivity mechanisms: Negative stress changes at the early stages of exposure and positive stress changes for high exposures.