MODEL RELEASED. Optical fibre manufacture. Technician adjusting the manufacturing process of a glass blank used to make optical fibres. This blank is made from high-quality quartz glass, the basic material for making optical fibres. Optical fibres are flexible glass strands which have a high refractive index. Each fibre can transmit light along its length with little or no absorption. Light beams travelling through the glass are internally reflected instead of passing out into the coating. The glass blank will be used as a template in the manufacture of actual strands. Optical fibres can be used to carry communications data in the form of light pulses.