Control of Bragg wavelength drift in high-temperature annealing cycles for RFBGs and fs-FBGs

We investigate the regeneration process of UV-written and femtosecond pulseswritten FBGs in standard fused silica glass encapsulated in sealed and unsealed tubes with air and Argon. Then we subject both grating types in unsealed tubes to several high temperature cycling to study the Bragg wavelength drift. We show that the regeneration occurs only in air or unsealed tubes and the RFBGs show less drift than fs-FBGs during the post-annealing process in small diameter tubes (1mm).