Silica-coated dual-tube zirconia induction furnace for high-strength optical-fibre production

The dual-wall zirconia induction furnace consists of an inner susceptor tube and an outer insulation tube. The centre piece of the inner tube is coated with a thin silica film. The performance of the newly designed furnace was evaluated in terms of the strength of drawn fibres. The proof test of 47 km length of fibre demonstrated superb strength results, yielding the average survival length at 1·4 GN/m2 (200 klb in−2) to be ∼8 km.