Telecommunication is communication at a distance using electrical signals or electromagnetic waves. Examples of telecommunications systems are the telephone network, the radio broadcasting system, computer networks and the Internet.

An optical signal consists of a series of pulses produced by switching a laser beam off and on. Its speed depends on how fast the beam can be switched on and off, and how much the pulses spread in length during transmission, an effect called dispersion.

Fixed networks a group of computers, printers, phones, and other equipment that are connected by wires, rather than by radio signals: Having fixed network points also means that cables will have to be shifted whenever the office layout changes.

Optical fibre is used as a medium for telecommunication and computer networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance communications, because infrared light propagates through the fibre with much lower attenuation compared to electrical cables.

A fixed line can be seen as a connection to an end customer, by means of a cable, through which a user can make phone calls or connect to the Internet. Fixed lines are clearly separate from the mobile phone network, by which end users are connected to the network via wireless transmission technologies.