Inscription kinetics and thermal stability of Bragg gratings written within heated fibers

The writing of gratings within heated hydrogen loaded, non H-2 loaded germanosilicate or Ce3+ doped aluminosilicate fibers was carried out through UV exposure. The fibers were heated by means of a CO2 laser beam, The thermally induced change in the grating growth kinetics depends on the type of fiber used to write the grating. The thermal stability of gratings written in either heated or unheated germanosilicate fibers was investigated through isochronal (30 min) annealing experiments, Difference between the thermal behaviors of gratings written in the H-2 loaded and the non H-2 loaded fibers was demonstrated. There exists strong evidence that structural changes are involved in the photosensitivity of the germanosilicate fibers.