High temperature annealing of type I and type IA FBGs

This study reports on high temperature behaviour and stability tests of type I and type IA FBGs. The gratings temperature is firstly increased monotonously up to 650 °C, then fixed at this temperature for several hours. By monitoring the reflection spectra of the gratings we show that standard type I grating disappears and then regenerates while type IA grating decreases monotonously and shifts to lower wavelength before it disappears without regenerating.