21 April

For the first time, optical fibre is used to carry live telephone traffic.

An optical fibre is a flexible, transparent fibre made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibres are used most often as a means to transmit light between the two ends of the fibre and find wide usage in fibre-optic communications, where they permit transmission over longer distances and at higher bandwidths (data rates) than wire cables. Fibres are used instead of metal wires because signals travel along them with lesser amounts of loss; in addition, fibres are also immune to electromagnetic interference, a problem from which metal wires suffer excessively.