Study of the fabrication parameters of large core Yb2O3 doped optical fibre through solution doping technique

Double clad large core Yb2O3 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 Al2O3 and Yb2O3 within the large core preform through soaking of the deposited multiple porous layers of fixed SiO2–P2O5 composition with an alcoholic solution of a mixture of suitable strength of AlCl3·6H2O and YbCl3·6H2O 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 Yb2O3 doped laser fibre technology.