Bragg gratings within each of the 3 GeO 2 -doped rings of a step-ring index low order Yb³⁺-doped core Cantor fractal bandgap fibre

Abstract

UV-induced Bragg gratings are written into the three concentric GeO 2 -doped rings of an Yb 3+ -doped-core Cantor fractal photonic-bandgap fibre. These rings can support several modes and the effective indices of these modes are derived experimentally from the grating peaks. They are found to be in excellent agreement with numerical simulation.