Effects of thermal annealing on Bragg fibre gratings in boron/germania co-doped fibre

This paper shows that two annealing processes must be considered when predicting the effect of temperature on fibre Bragg gratings that have been written by UV radiation in boron/germania co-doped fibres. Both the thermal decay of the grating-related refractive index and the annealing of the boron-induced refractive index contribute to the wavelength shift observed. We have combined the theory of these two effects to match data taken experimentally (accuracy ±0.3 nm) and successfully explained a selection of observed wavelength shifts ranging from -2.83 to +0.75 nm.