Tingye Li, an electrical engineer whose calculations in the early 1960s helped guide the development of the laser and propel the dizzying increase in the speed of fiber-optic communication, died on Dec. 27 in Snowbird, Utah. He was 81.
Family photo
Some of the work done by Dr. Li and his colleagues at Bell Labs laid the groundwork for today’s broadband.
The cause was a heart attack while he was on a family ski trip, his family said. He lived in Boulder, Colo.
Lasers were in the early stage of development when Dr. Li and a colleague at Bell Labs, A. Gardner Fox, developed a computer simulation of how lasers produce the focused light energy that has transformed fields from medicine to space travel. They reported their findings in a paper published in 1961.
Dr. Arno Penzias, a former director of Bell, called their paper a tool kit for subsequent designers of lasers and other optical systems. He said it helped transform the “wonderful invention” of the laser — an acronym for light amplification by stimulated emission of radiation — into “a practical communications platform.”
In essence, the researchers provided a mathematical model for how light bounces about inside a laser between two mirrors as it gathers energy, predicting factors like the shape and intensity of light beams. Alan Willner, an electrical engineering professor at the University of Southern California, called the work “the foundational teaching” on the innards of lasers.
“There aren’t many papers that help define a field, but this was one of them,” he said in an interview.
The research that led to nearly instantaneous communication by light waves was itself snail-like. Dr. Li and Dr. Fox had to write their own programs, punching them into decks of cards, for a room-size computer that was less powerful than a palm-size calculator today. The computer ran the program for two or three hours. A frequent error message meant that the researchers had to scour the cards for a single improperly punched letter, Jeff Hecht wrote in “Beam: The Race to Make the Laser” (2010).
Bell Labs was virtually unchallenged as the largest and most inventive laboratory in the world, having a hand in many of the 20th century’s most important inventions. Dr. Li, who wrote or helped write more than 100 papers, patents and books, led research teams at Bell for more than three decades.
Some of their work laid the groundwork for today’s broadband. One area of study was in finding ways to use light waves to convey information on optical fiber rather than copper wire or radio waves. Another team Dr. Li led developed optical amplifiers, which amplify an optical signal directly without the need to first convert it into an electrical signal.
Dr. Li was an early proponent of using the rare earth metal Erbium in the amplifiers, an improvement that helped raise their capacity more than a hundredfold.
“Tingye Li has shaped the lightwave network infrastructure we know today,” the Institute of Electrical and Electronics Engineers said when presenting him with its Edison Medal in 2009.
Li Ding Yi, as his name is transliterated from Chinese, was born in Nanking, China, on July 7, 1931. His mother, Lily, was one of the first generation of Chinese women to receive a modern higher education. She became an activist for women’s rights.
His father, Chao, was a Chinese diplomat who was consul general in Vancouver, where Tingye attended middle school, and was later posted to South Africa, where Tingye earned an undergraduate degree in electrical engineering from the University of Witwatersrand. He earned a Ph.D. in electrical engineering from Northwestern University in Evanston, Ill.
Dr. Li joined the Bell Telephone Laboratories (later AT&T Bell Laboratories) in 1957 and worked there until 1998. He worked there with the Nobel Prize recipients Charles Hard Townes and Arthur L. Schawlow, who together invented the maser, which amplified microwaves the way lasers would soon amplify light.
“There was a lot going on and a lot of people helping each other,” Dr. Penzias said.
Dr. Li often quoted Confucius, though friends suspected he occasionally concocted his own learned sayings and then attributed them to the sage. He frequently went to China to help it develop optical communications. The Chinese Academy sent his family a letter at his death praising him for helping China “leapfrog to a higher level” in handling telecommunications traffic.
Dr. Li is survived by his wife of 56 years, the former Edith Wu; his daughters, Deborah Li Cohen and Kathryn Li Dessau; and four grandchildren.
In a speech on his 80th birthday, Dr. Li revealed that he had proposed marriage to his wife for their next life, after they are both reincarnated. She tentatively agreed, he said, if he behaved.
