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Tribute to a telecoms pioneer

Last week the death of Charles Kuen Kao, the engineer who received the 2009 Nobel Prize in Physics for pioneering work in fibre-optic communications, was announced. 52 years ago, Kao published a ground-breaking paper that heralded the use of optical fibre for high speed communications.

The story of the birth of optical fibre communications is an example of how many of the technologies we all depend on came from international research. Kao was born in China and worked at the Standard Telecommunications Laboratories in the UK. His group at STC was set up to investigate the use of laser communications by the British inventor of pulse code modulation, Alec Harley Reeves.

Kao and his colleagues at STC had heard that Eli Snitzer at American Optical had shown that a very thin glass fibre could be used to confine light to a single path. However, because the very high loss of the glass available then made communications over more than a few metres impossible, other researchers concentrated on metal waveguides. But Kao asked the crucial question that no else had thought of asking: how transparent can glass possibly be made?

Harold Rawson, a glass expert at the University of Sheffield in the UK, told Kao that by purifying glass, fibre could carry optical signals over several kilometres.

Kao then carried out tests on glass made by Corning in the USA to withstand high temperatures. But no one apart from Kao had thought to measure its optical properties. He found the glass could be the basis of a practical communications system.

Further research by Corning resulted in glass fibre that could carry telecommunications traffic over long distances and which the Internet and mobile communications ultimately rely on.