MODEL RELEASED. Optical fibre manufacture. Techni- cians producing a glass blank (glowing) for making optical fibres. This blank is made from high- quality quartz glass, the basic material for making optical fibres. Optical fibres are made from flexible glass that has a high refractive index. Each fibre is then coated with an outer protective layer that has a low refractive index. Light beams travelling through the glass are internally reflected instead of passing out into the coating. The light may travel along the entire cable with little absorption. This glass will be used to make optical fibres which will carry communication data. Photographed in Germany.