Complex decay behaviour of fibre Bragg gratings: further evidence of three energy level system of photosensitivity in germanium-doped optical fibre

A complex grating decay process is observed at elevated temperatures as predicted by our recent proposed three energy level model. The thermal stability of positive and negative index gratings in a Boron-co-doped germanosilicate fibre is characterised, so that the stability of such grating can be accessed for any writing fluence