Fibre Optic Cable

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 (when the signal can take one of several paths it is called "multi-mode", whereas a single longidtudinal path is called "single mode").

Fibre optic cables are used in LANs where they offer specific advantages. They are increasingly replacing copper conductors on some applications because of their unique properties:

Lower signal loss per unit distance (resulting in longer distances between repeaters)
Higher Capacity (allowing operation at higher data rates)
Smaller physical size (allowing more fibres in a duct or trunk)
Immune to interference (Provides electrical isolation between local and remote nodes. It may therefore be used to connect buildings which could potentially operate on different mains phases, provides immunity form lightning strike, and is suitable for use in industrial environments where there is a high level of background noise.)
In some applications, fibre is used to provide a very high level of security - i.e., because it is very difficult to monitor or tap the cable to observe the frames being carried.
Fibre optic cabling is often regarded as an investment, since the same cable infrastructure can support a number of different network technologies, with potentially large increases in speed being available without need to upgrade the installed cable