Shifts in resonance wavelengths of Bragg gratings during writing or bleaching experiments by UV illumination within germanosilicate optical fibre

The resonance wavelengths of Bragg gratings are shown to increase with irradiation time during their inscription if the core of a germanosilicate fibre is exposed to a 243 nm UV fringe pattern. Exposure of the gratings to a 243 nm UV monotonic illumination leads to a recovery in the transmittance of the filters. Whether this irradiation induces a shift, or not, in the Bragg wavelength of the filters depends on the history of the grating writing experiment.