A fibre optic cable propagate a signal as a pulse of light along a transparent medium.
A fibre optic cable is made from a glass or plastic core that carries light surrounded by glass cladding that (due to its lower refractive index) reflects "escaping" light back into the core, resulting in the light being guided along the fibre. The outside of the fibre is protected by cladding and may be further protected by additional layers of treated paper, PVC or metal. This required to protect the fibre from mechanical deformation and the ingress of water.
Fibre optic cable consisting of a core and cladding with different refractive indices in some cases fibre optic cables are strengthened by strengthening fibres or external protective wrapping.
Fibre optic cable used to transmit a serial bit stream using pulses of light
Fibre optic cables are increasingly replacing copper conductors in WANs and MANs because of their unique properties:
Fibre optic cables may also be used in LANs (e.g. 10BF) and are used to span larger distances, provide potential upgrade to higher data rates or to provide electrical isolation (e.g. when a cable must be laid between two buildings).