Annealing of arc-induced gratings at high temperatures

Long period gratings arc-induced in different types of fibre were annealed at 1000degC for 24degh. During the annealing, the spectrum of the gratings written in Ge-doped fibres shifted towards longer wavelengths whereas an opposite shift was observed for gratings written in Ge-free fibres. A discussion on the mechanisms responsible for that behaviour is presented.