Isochronal annealing of BG written either in H/sub 2/-loaded, UV hypersensitized or in OH-flooded standard Telecommunication fibers using ArF laser

On one hand, the stability of fiber Bragg gratings (FBG) written either in ultraviolet (UV) hypersensitized, OH flooded, H
₂
loaded or in pristine fibers has been investigated through isochronal annealing experiments. The stability of the modulation proved to be higher in the hypersensitized and OH-flooded fibers. In contrast the annealing-induced shift in the Bragg wavelength (lambda
_B
) was lower in the H
₂
-loaded and pristine counterparts. On the other hand, germanosilicate preform plates have been sensitized and then exposed in similar conditions to those used for writing the gratings. Vacuum-ultraviolet (VUV) and infrared (IR) absorption spectroscopy has been carried out with a view of monitoring the formation (or bleaching) of defect-associated bands. These observations are discussed within the framework of a defect model