Sir Charles Kao
Scientist whose work on fibre optics enabled broadband
SIR CHARLES KAO, who has died aged 84, was known as “the godfather of broadband” and in 2009 shared the Nobel Prize in Physics with George Smith and Willard Boyle for his discovery that light could be transmitted over long distances via optical glass fibres.
It was the Irish scientist John Tyndall who in 1870 observed that a flow of water could channel sunlight – a phenomenon known as total internal reflection. Fibre optics – transparent rods of glass capable of transmitting signals much more efficiently than metal wire – operate under the same principle.
There was interest in the 1960s in using optical fibres to carry telephone calls, but the fibres then available were capable only of transmitting light tens of metres before it petered out. Working at Standard Telecom Laboratories (STL) at Harlow in Essex, Kao worked out that the loss of light was not an inherent property of the glass, but was due to imperfections in the material, the most significant problem being traces of iron.
In 1966 in “Dielectricfibre surface waveguides for optical frequencies”, written jointly with George Hockham, Kao suggested that ultra-transparent glass fibres made from fused silica could represent “a new form of communication medium”, making it possible to transmit signals across 100 kilometres or more.
There was some scepticism, including from Kao’s wife who, he recalled in 2006, told him to “pull the other leg” when he told her he was late for dinner because he was working on a “world-shaking project”. Some of Kao’s fellow engineers laughed in disbelief when the paper was presented.
But the paper sparked an intense worldwide race to produce glass fibres with low optical losses to replace traditional copper cables. In 1970 scientists at Corning Glass announced they had developed the first such fibre. Subsequent years saw the development of everpurer optical fibres and new transmission techniques that made it possible to carry messages over longer distances, leading to the explosive growth of optical communications and paving the way for the so-called information superhighway and broadband.
Charles Kuen Kao was born in Shanghai on November 4 1933. In 1948 his family moved to Hong Kong, where he was educated at St Joseph’s College. He then moved to London, where he studied Electrical Engineering at Woolwich Polytechnic (now the University of Greenwich), followed by a PHD as an external student at University College London under Harold Barlow, while he was working at STL in Harlow.
In 1970 he joined the Chinese University of Hong Kong (CUHK), founding its department of electronics, becoming a Reader and then Professor of Electronics, and later serving as vicechancellor of the university from 1987 to 1996.
He also spent much time in the US, working as chief scientist, then director of engineering, at the ITT Corporation in Roanoke, Virginia. In 1982 he became the first ITT Executive Scientist, stationed mainly in Connecticut. He also taught at Yale University.
After his retirement from CUHK Kao took a six-month sabbatical in London at Imperial College’s department of electrical and electronic engineering, and for the next five years was a visiting professor in the department.
In his later years Kao suffered from Alzheimer’s disease, and in 2010, with his wife, he set up the Charles K Kao Foundation to help patients and increase public awareness of the disease.
Among numerous honours and prizes, Kao was elected a fellow of the Royal Society in 1997 and knighted in 2010. Kao Park, a business park in Harlow, has been named after him.
Charles Kao married May-wan “Gwen” Wong in 1959. She survives him, with their son and daughter.
Sir Charles Kao, born November 4 1933, died September 23 2018