Charles K. Kao

Sir Charles Kuen Kao (November 4, 1933 – September 23, 2018) was a Hong Kong electrical engineer who contributed to the development and use of fibre optics in telecommunications. In the 1960s, Kao created various methods to combine glass fibres with lasers in order to transmit digital data, which laid the groundwork for the evolution of the Internet and the eventual creation of the World Wide Web.

Born in 1933 in Shanghai, Kao and his family settled in Hong Kong in 1949. He graduated from St. Joseph's College in Hong Kong in 1952 and went to London to study electrical engineering. In the 1960s, he worked at Standard Telecommunication Laboratories, the research center of Standard Telephones and Cables (STC) in Harlow, and it was here in 1966 that he laid the groundwork for fibre optics in communication. Known as the "godfather of broadband," the "father of fibre optics," and the "father of fibre optic communications," he continued his work in Hong Kong at the Chinese University of Hong Kong, and in the United States at ITT (the parent corporation of STC) and Yale University.

In 2009, Kao was awarded the Nobel Prize in Physics "for groundbreaking achievements concerning the transmission of light in fibres for optical communication." The following year, he was knighted by Queen Elizabeth II "for services to fibre-optic communications."

Kao was a permanent resident of Hong Kong, and a citizen of the United Kingdom and the United States.

Early life and education

Charles Kuen Kao was born on November 4, 1933, in Shanghai, China, and lived with his parents in the Shanghai French Concession. He studied Chinese classics at home with his brother, under a tutor. He also studied English and French at the Shanghai World School (上海世界學校) that was founded by a number of progressive Chinese educators, including Cai Yuanpei.

After the Communist Revolution in 1949, Kao's family settled in Hong Kong, which at the time was a British crown colony. Much of his mother's siblings moved to Hong Kong in the late 1930s. Among them, his mother's youngest brother took good care of him.

Kao's family lived on Lau Sin Street—at the edge of the North Point—a neighbourhood of Shanghai immigrants. During Kao's time in Hong Kong, he studied at St. Joseph's College for five years and graduated in 1952.

Kao obtained high score in the Hong Kong School Certificate Examination, which at the time was the territory's matriculation examination—qualifying him for admission to the University of Hong Kong (HKU). However, electrical engineering wasn't a programme available at HKU, the territory's then only tertiary education institution.

Hence, in 1953, Kao went to London to continue his studies in secondary school and obtained his A-Level in 1955. He was later admitted to Woolwich Polytechnic (now the University of Greenwich) and obtained a B.Sc. in 1957. He then pursued research and received his Ph.D. in Electrical Engineering in 1965 from the University College London—under the supervision of Harold Barlow—as an external student while working at Standard Telecommunication Laboratories in Harlow, the research centre of Standard Telephones and Cables (STC).

Ancestry and family

Kao's father Kao Chun-Hsiang (高君湘), originally from Jinshan City (now a district of Shanghai City), obtained his Juris Doctor from the University of Michigan Law School in 1925. He was a judge at the Shanghai Concession and later a professor at Soochow University (then in Shanghai) Comparative Law School of China.

His grandfather Kao Hsieh was a scholar, poet, and artist. Several writers including Kao Hsü, Yao Kuang (姚光), and Kao Tseng (高增) were also Kao's close relatives.

His father's cousin was astronomer Kao Ping-tse (Kao crater is named after him). Kao's younger brother Timothy Wu Kao (高鋙) is a civil engineer and professor emeritus at the Catholic University of America; his research is in hydrodynamics.

Kao met his future wife Gwen May-Wan Kao (née Wong; 黃美芸) in London after graduation, when they worked together as engineers at STC. She was British Chinese. They were married in 1959 in London, and had a son and a daughter, both of whom reside and work in Silicon Valley, California. According to Kao's autobiography, Kao was a Catholic who attended Catholic Church while his wife attended the Anglican Communion.

Academic career

Fibre optics and communications

In the 1960s at Standard Telecommunication Laboratories (STL) based in Harlow, Essex, England, Kao and his coworkers did their pioneering work in creating fibre optics as a telecommunications medium, by demonstrating that the high-loss of existing fibre optics arose from impurities in the glass, rather than from an underlying problem with the technology itself.

In 1963, when Kao first joined the optical communications research team he made notes summarising the background situation and available technology at the time, and identifying the key individuals involved. Initially Kao worked in the team of Antoni E. Karbowiak (Toni Karbowiak), who was working under Alec Reeves to study optical waveguides for communications. Kao's task was to investigate fibre attenuation, for which he collected samples from different fibre manufacturers and also investigated the properties of bulk glasses carefully. Kao's study primarily convinced him that the impurities in material caused the high light losses of those fibres. Later that year, Kao was appointed head of the electro-optics research group at STL. He took over the optical communication program of STL in December 1964, because his supervisor, Karbowiak, left to take the chair in Communications in the School of Electrical Engineering at the University of New South Wales (UNSW), Sydney, Australia.

Although Kao succeeded Karbowiak as manager of optical communications research, he immediately decided to abandon Karbowiak's plan (thin-film waveguide) and overall change research direction with his colleague George Hockham. They not only considered optical physics but also the material properties. The results were first presented by Kao to the IEE in January 1966 in London, and further published in July with George Hockham (1964–1965 worked with Kao). This study proposed the use of glass fibres for optical communication. The concepts described, especially the electromagnetic theory and performance parameters, are the basis of today's optical fibre communications.

In 1965, Kao with Hockham concluded that the fundamental limitation for glass light attenuation is below 20 dB/km (decibels per kilometer, is a measure of the attenuation of a signal over a distance), which is a key threshold value for optical communications. However, at the time of this determination, optical fibres commonly exhibited light loss as high as 1,000 dB/km and even more. This conclusion opened the intense race to find low-loss materials and suitable fibres for reaching such criteria.

Kao, together with his new team (members including T. W. Davies, M. W. Jones and C. R. Wright), pursued this goal by testing various materials. They precisely measured the attenuation of light with different wavelengths in glasses and other materials. During this period, Kao pointed out that the high purity of fused silica (SiO₂) made it an ideal candidate for optical communication. Kao also stated that the impurity of glass material is the main cause for the dramatic decay of light transmission inside glass fibre, rather than fundamental physical effects such as scattering as many physicists thought at that time, and such impurity could be removed. This led to a worldwide study and production of high-purity glass fibres. When Kao first proposed that such glass fibre could be used for long-distance information transfer and could replace copper wires which were used for telecommunication during that era, his ideas were widely disbelieved; later people realized that Kao's ideas revolutionized the whole communication technology and industry.

Kao also played a leading role in the early stage of engineering and commercial realization of optical communication. In spring 1966, Kao traveled to the U.S. but failed to interest Bell Labs, which was a competitor of STL in communication technology at that time. He subsequently traveled to Japan and gained support. Kao visited many glass and polymer factories, discussed with various people including engineers, scientists, businessmen about the techniques and improvement of glass fibre manufacture. In 1969, Kao with M. W. Jones measured the intrinsic loss of bulk-fused silica at 4 dB/km, which is the first evidence of ultra-transparent glass. Bell Labs started considering fibre optics seriously. As of 2017, fibre optic losses (from both bulk and intrinsic sources) are as low as 0.1419 dB/km at the 1.56 μm wavelength.