Fibre optics. Several optical fibres for use with lasers. These fibres are made from a pure silica glass core with a fluorine-doped silica cladding and an acrylate coating. The core has a high refractive index and the coating has a low refractive index. This ensures that light travelling along the fibre is totally internally reflected. Optical fibres are used to transmit data using light. They can also be used to transmit laser light without appreciable loss of energy. These fibres can be used for dye lasers in birthmark removal.