How is glass fibre material in optical fibres used?

Glass fibre material in optical fibres:

Silica is the generally used materials for the manufacture of a glass fibre. The glass utilized in a fibre-optic cable is ultra pure, silicon, ultra transparent, silicon dioxide or fused silica.

Glass fibres are prepared by fusing silica and metal oxides. By a pure glass fibre optic cable consists of a glass core and a glass cladding and is far the most extensively used into fibre. Throughout the glass fibre-optic cable fabrication procedure, impurities are purposely added to the pure glass so as to acquire the desired indices of refraction required to guide light.

Illustrations:

a. GeO₂– SiO₂ core, SiO₂ cladding

b. SiO₂core, P₂O₃-SiO₂ cladding