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:
Copyright SRDE 2002
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