John Midwinter, who has died aged 83, did much to transform telecommunications from a simple phone-based service in the 1970s to the full broadband and internet network that we have today. Before such services came from the privatised British Telecom, the state provider was the General Post Office: during John’s time at the GPO research laboratory (1971-84), he shaped the understanding, design and development of the first optical fibre communications systems and their introduction into the UK network.
In the process he helped Britain lead the world in establishing optical communications as a fast-moving and competitive research area.
When, in 1966, Charles Kao of Standard Telecommunication Laboratories proposed the idea of optical fibres – strands of glass as thin as a hair carrying communications traffic – the challenges were huge, and struck many as insurmountable. A full system called for the design of optical transmitters and receivers, reliable lasers to generate pulses of light, techniques to modulate and demodulate data, and a better understanding of the physics of data-carrying optical pulses propagating in glass.
However, John, as head of what became the GPO’s optical communications division, set about developing a complete system carrying live traffic. In 1977 the world’s first optical fibre system was installed between Martlesham and Kesgrave, in Suffolk, with members of his research team splicing fibres in the snow, sleet and rain, to successfully demonstrate the transmission of data over approximately 8km of fibre.
The next problem was to significantly extend the length of these systems. This involved the use of mono-mode fibres of a much smaller diameter core, supporting a single path for the light to follow. Data-carrying pulses of light could be prevented from spreading, so allowing much higher data rates over longer distances.
This went against conventional wisdom, which held that it would be impossible to join such thin, fragile fibres. However, by the early 80s, John’s group achieved this feat, sending data at four times the rate over a distance of 60km.
British Telecom, as it was from 1980, stopped all work on competing technologies and in 1984 became the first telecommunication operator to switch entirely to single-mode fibre systems. The rest of the world soon followed, with the help of John’s textbook, Optical Fibres for Transmission (1979). As a result of his work, today more than 95% of all data is transmitted over optical fibres and more than 500m kilometres of fibre are installed each year on land or under the sea.
In 1984 Eric Ash, head of the department of electronic and electrical engineering at University College London, recruited John as BT professor of optoelectronics. At UCL John focused his research on exploring whether photons could be used to carry out processing functions in order to design, for example, an optical computer. But while photons were excellent for transmission, electrons proved better for switching and other digital functions.
By the early 90s, John returned to research on optical communications, exploring the use of multiple …….