Study of the fabrication parameters of large core Yb 2O 3 doped optical fibre through solution doping technique

Abstract

Double clad large core Yb 2O 3 doped fibres with core diameter up to 20 μm have been fabricated by the solution doping technique through deposition of multiple porous core layers. The process parameters have been optimized with respect to the uniform doping of Al 2O 3 and Yb 2O 3 within the large core preform through soaking of the deposited multiple porous layers of fixed SiO 2–P 2O 5 composition with an alcoholic solution of a mixture of suitable strength of AlCl 3·6H 2O and YbCl 3·6H 2O to get the desired low NA around 0.09–0.11. The most critical parameters associated in this process are the deposition temperature with respect to uniform deposition of un-sintered layers of equal thickness with suitable porosity, viscosity of the soaking solution, pre-sintering temperature, proper mixing of the inlet gas mixture as well as proper drying of the thick porous layer after solution soaking process. This investigation will be very useful for development of large core Yb 2O 3 doped laser fibre technology.