Because a trunk communication system using optical fibres has wideband capabilities, it has the potential to handle many more channels than more conventional systems and hence cope with the increased data, voice, video and facsimile information transmitted by the satellites to combat zones.

Fibre optics also offers electrical isolation from one point to another and it is immune to lightning discharges and to electromagnetic and electrostatic interference. Security is also greatly enhanced because it is not possible to eavesdrop as easily as it would be for radio links and the cross talk encountered in cabled wire pairs is eliminated.

An extensive programme of work was undertaken to study the propagation of light waves down optical fibres and ways in which the light can be modulated by modifying the electro-optical properties of crystals. The results of this work has produced profound benefits for the world wide telephone circuits.

Optical Communication Systems

Optical communication systems were first studied in the Quantum Physics Division at SRDE in the early 1960s using the Helium-Neon Gas laser, and the Gallium Arsenide diode lamp. Semiconductor photodiodes and photomultipliers were used as receivers and examples of TV transmission by amplitude modulation, and speech transmission by pulse position modulation were demonstrated.

An analysis group provided mathematical services to the Establishment as a whole and produced a library of in-house computer programs. Problems that arose in the general field of communications, in particular radio wave radio propagation by ionospheric and tropospheric scatter and anomolous UHF propagation, were investigated. This work was also in conjunction with fundamental studies on the aerials used in the different communication links.

The Research and Development programme also included:

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