Method of fabricating optical fibres by the solution-doping technique

Abstract From the Canadian patent

Silica intended to form the core of an optical-fibre preform is deposited as an unvitrified soot inside a reaction tube, and a non-aqueous solution of one or more dopant precursor is then introduced into the tube without removing the tube from the apparatus. A first precursor may be for a dopant such as alumina to raise the refractive index of the layers formed by vitrification of the soot and a second, precursor for a dopant such as rare earth to improve the transmission properties of the preform material. The solution may be introduced and removed either through branches on the tube, or by filling the tube in each case, without removing it from the lathe used to rotate the tube during …