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.