Bragg gratings in the germanium-doped cladding rings of a Yb3+-doped solid bandgap fibre

Abstract

We demonstrate the inscription of Bragg gratings in the germanium-doped cladding rings of a large-mode-area, ytterbium-doped photonic-bandgap fibre. The gratings are inscribed in these doped rings that can support several modes, the refractive indices of which are derived from experiment and calculated theoretically.