Radiation induced effects on FBGs using different femtosecond laser inscription methods

We consider a comparative study of radiation effects (γ and electron) on fibre Bragg gratings (FBGs) that were inscribed using a femtosecond laser in single mode silica optical fibre. The FBGs were inscribed using the point-by-point and the plane-by-plane inscription methods. The FBGs were exposed to a total accumulated radiation dose of 15 kGy in both γ and electron cases. The gratings’ spectra were measured and analysed before and after the exposure to the radiation, while complementary characterisation was undertaken using Raman and Fourier transform infrared spectroscopy. In addition, the changes of the temperature coefficient of the FBGs were analysed comparatively prior to the irradiation to explain how material changes responded to the particular types of radiation. Finally, we consider which of the two inscription methods proves more robust in such harsh environments.