Fibre optics material. Coloured scanning electron micrograph (SEM) of cuts made into material used in a fibre optics cable. Various materials are used in a fibre optics cable. The core and cladding are made of silica (glass) of varying refractive properties, and carry and reflect the light passing through the cable. Surrounding these inner layers are a buffer layer made of resin, and a large jacket layer made of plastic. Typically, the jacket layer will be around 0.5 millimetres across, while core will only be 8 micrometres across. The cuts seen here have been made with an ion beam. Magnification: x240 when printed 10cm wide.