Making waves in lightwave communications since 1960
- By Deborah Minors
Honorary graduate: Dr Tingye Li
The world in which electrical engineer Tingye Li graduated in 1952 was a technological chasm compared to the 21st century. Lasers were unheard of and the Internet not yet conceived. Li’s pioneering work in lasers and optoelectronics increased the speed of optical communications 100-fold, a development that is the foundation of the Internet and contemporary digital communications. Wits awarded Li an honorary degree in July 2011 in recognition of his contribution to the field.
The School of Electrical and Information Engineering hosted Dr Tingye Li (BSc Eng Electrical 1952, honorary DSc Engineering 2011) during his first trip to South Africa in 60 years. Li delivered talks on the “Evolution of the lightwave communications industry: Technologies, demand and business” and “Lightwave communications: A mainstay of the information society”, in Johannesburg on 20 and 21 July, and he delivered the graduation address at which he received his honorary degree.
Born in Nanjing, China in 1931, Li is the son of a former mayor of Shanghai and later governor of Taiwan, and a Chinese women’s liberation movement feminist, who died recently, aged 105.
Li lived in Canada and the United States prior to studying at Wits, and returned to the US to complete his PhD (1958) at Northwestern University, Evanston.
He joined Bell Laboratories (now AT&T) in New Jersey in 1957, where he remained until his formal retirement in 1998.
Over 40 years in the fields of lasers, optical fibre (lightwave) communications, microwave antennas and satellite communications, Li made fundamental contributions to optical science and communications engineering.
He was the first to point out fundamental aspects of laser design, theory and practice relating to laser propagation and operation.
A seminal study by Li and a colleague in 1961 revealed various modes of energy distribution in lasers, each with varying velocity, an observation that is fundamental to understanding laser design. The study, cited more than 595 times since publication, represents one of the key insights into the science of laser operation.
Arguably Li’s greatest contribution has been in the field of optical fibre communication. He was instrumental in developing the world’s first amplified wavelength division multiplexed (WDM) transmission system – technology which combines multiple analogue or digital data streams into one signal over a shared medium, by using wavelengths (colours) of laser light.
Based on the premise that a communication technique can be practical only if it is compatible with existing technology, Li explored the use of “optical amplifiers” in his WDM system.
The use of optical amplifiers in this 1992 experiment revolutionised lightwave communications. It increased the speed at which optical data could be transmitted 100-fold – the highest rate available at the time. This shaped communications systems in the modern information society, including the Internet.
Now an independent consultant in the field of lightwave communications, Li said in an interview in the Northwestern University alumni magazine, “[Lightwave communications] is a field of never-ending interest. It involves fundamental science, it involves high tech, and it involves the innovation to turn fundamental science into technology that can be used to benefit society and humankind.”
He adds that his rigorous training in mathematics, science and engineering at Wits served him well. “It has been a very exciting career, and it will never end until I finally close my eyes and leave the world. As long as I can use my brain, I will keep pursuing what intellectually stimulates and challenges me.”