Photodarkening in optical fibres: Comparative study of photo-induced defects using different photon sources

In this paper, recent investigation on Ce-doped fibres is presented and for the first time, parallel irradiation with high intensity photons in the NIR, UV, X-Ray and gamma ray wavelength regions was performed in order to study the materials structure and its relationship with photodarkening. A set of preform core samples are prepared with appropriate Al/Yb and Yb/Ce concentrations. The obtained defects are identified by UV-VIS spectroscopy, fluorescence spectroscopy and electron paramagnetic resonance (EPR) spectroscopy.