Tingye Li: A Global Force in Optical Communications

Born into a world on the brink of war, Tingye Li shaped a communications industry that linked the world in peace. Li, the popular 1995 OSA President who died last December at 81, lived a truly global life.

 

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Every time you make a phone call or use the Internet, you can thank Tingye Li. From the oscillations inside laser cavities to the complex methods used to send multiple information streams down a single fiber, the discoveries that he and his research teams have made are deeply woven into the fabric of global networks.

Li, the 1995 OSA President who died last December at age 81, lived a truly global life. Born to a diplomat, he resided on three continents before reaching adulthood. When he started at Bell Labs, his only employer, the Cold War space race was on; by the time he retired, the nascent World Wide Web was growing by leaps and bounds. By his own account, he had traveled a “gigameter” (a million kilometers) over the course of his career to foster technological cooperation and progress between his adopted and native countries.

Li and a colleague predicted the transverse modes in laser cavities at the dawn of the laser revolution. Twenty years later, he led the team that developed sparse-channel wavelength division multiplexing (WDM) systems, which, along with optical amplifiers, changed the economic paradigm of telecommunications.

His long list of achievements include high awards from OSA and IEEE, one of the most cited papers ever published in his field, and honorary doctorates and professorships. Yet his colleagues invariably remember him for his personality: his warmth, excellent sense of humor, mentorship of young colleagues, intellectual breadth and depth, and passion for his work. He was a technical giant who was so popular among his contemporaries that no one wanted to run against him in an OSA election.

 

figureIn this family photo dated 1936, Li is the sweater-clad boy standing between his two widowed grandmothers. The extended family lived together as a multigenerational household in Nanjing. 

 

figureTingye Li as a young man in South Africa in 1953.

Learning on new continents

Tingye Li was born on 7 July 1931 to a prominent diplomat’s family in Nanjing, which was the capital city of China. His father, Sizhao Li, was a senior officer in the Foreign Ministry, and his mother, Weipeng “Lily” Xie, was a rarity in her country during that era: a college-educated woman. Tingye was the eldest of four children: sister Wei-ling, brother Ting-Kai and sister Yuling.

Based on Tingye’s cheerful disposition, you might never guess that he had a childhood shaped by war. When he was just six years old, Japanese forces invaded mainland China and captured its capital, Nanking (now called Nanjing), which had been home to the Li family. According to some estimates, more than 200,000 civilians were brutally assaulted and killed in a six-week span—although accounts vary on the nature and scale of the carnage.

The Nanking Massacre, as it is sometimes called, was a key precipitator to World War II in the Pacific. Fortunately, in the fall of 1937, just before Nanking fell to Japan, the Li family escaped with the government to Chongqing (then known as Chungking), far to the west and protected from the invaders by a mountain range.

While many survivors never spoke about their harrowing wartime experiences, Li wanted his family to know about his. Scott Cohen—one of his grandsons—described them in a fourth-grade essay in 2000, writing that Tingye “ran as fast as he could toward the air raid shelter in the dark of night.”

The war was in full swing when the Li family moved to Vancouver, Canada, after the Chinese government had appointed his father consul general there. Tingye was 12 years old.

“They flew out of Chungking over the mountains to Calcutta, India,” wrote Scott. “From there they took a train to Bombay. Tingye looked out from the window and saw the strange Indian countryside. He had never been outside of China before.” The family boarded a captured Italian liner that the United States had turned into a troop transport ship and headed for North America via Australia. The vessel dodged Japanese submarines throughout its 37-day journey, and the ship ahead of Tingye’s went down. “Tingye was scared that they might be sunk and his short life might be over,” Scott wrote.

When Li was 12, the Chinese government appointed his father consul general to Vancouver, Canada. Despite not knowing much English upon arrival, the Li children settled in and flourished in Vancouver. One of Tingye’s favorite pastimes as a child was building radio sets.

When he was 17, his father was transferred to a similar post in Johannesburg, South Africa, and the family followed. For his undergraduate studies, Tingye enrolled at the University of the Witwatersrand, where he earned his bachelor’s degree in electrical engineering. At the time, “Wits,” as it was often called, accepted students of all ethnicities; it did not restrict matriculation by race until the apartheid government forced it to do so several years after Li had graduated.

In January of 1953, the two Li brothers visited Europe and then sailed to the United States to continue their educations. Li enrolled at the Illinois Institute of Technology for his graduate degree, but after a year or so he transferred to Northwestern, where he received his Ph.D. in electrical engineering.

Meant to Be:
Tingye Woos Wu

In 1953, Tingye and his brother were young adults who wanted to further their educations in the United States. They traveled to the United States from South Africa, where their father had been stationed as a diplomat. Their journey started on a passenger ship to England and ended after the two reached New York aboard the beautiful Cunard ocean liner Mauretania.

Along the way, a friend was flipping through Life magazine and spied a wedding photo taken at a fancy estate in Chicago. The bride, Eileen Wu, and her maid of honor, Edith, were the daughters of K.C. Wu, a prominent American-educated Chinese politician who served as mayor of Shanghai and governor of Formosa. He had sent his daughters to live with the family of an American friend, Robert McCormick, publisher of the Chicago Tribune, while studying at Northwestern University in Evanston, Ill.

“At that time, the McCormicks pretty much owned the town,” said Debbie Li Cohen, the elder of Li’s two daughters. The prominence of both the McCormick and Wu families prompted the wedding coverage in Life. Seeing the magazine pictures, a friend teased Li that he really ought to look up the younger Wu sister when he got to Chicago.

He did. After a year at the Illinois Institute of Technology, Li transferred to Northwestern to continue his studies in electrical engineering. It was there that he met and fell in love with Edith. He married her on 9 June 1956, a year before he finished his Ph.D. He often told people that he had “wooed Wu and won Wu.”

Bell Labs: The early years

In 1957, straight out of graduate school, Li took a job at the Holmdel, N.J., branch of Bell Telephone Laboratories, one of the world’s premier industrial laboratories. He would remain there for 41 years, working his way up to department head and building creative research teams that laid the groundwork for today’s telecommunications industry. One of his friends and Bell Labs collaborators, OSA Honorary Member Herwig Kogelnik, says that Li simply loved working there all those decades.

Initially, Li joined the radio research department and started working on a hot technology for the space age: antennas for satellite communications. Through Project Echo, followed by Telstar, the company collaborated with NASA and other agencies to send microwave and television signals across thousands of miles of Earth’s surface by way of low Earth orbit. For the projects, Bell Labs built large aluminum “horn antennas” at its Holmdel laboratory and a second site in Andover, Maine. The two antennas had somewhat different shapes—the Holmdel one was “pyramidal” while the Maine device was conical like the horn of an old gramophone.

For a special Telstar issue of the Bell Systems Technical Journalin July 1963, Li and two co-authors computed the gain and radiation patterns for the two antennas in different excitation modes. Undoubtedly the knowledge of the directionality and other electrical characteristics of the Holmdel antenna assisted two other Bell Labs researchers, Arno Penzias and Robert Wilson. In 1964, they used the device to test out their new, ultra-sensitive microwave receiver—and ended up confirming the existence of the cosmic microwave background radiation, the distant echoes of the creation of the universe.

Understanding the laser

As the 1950s blended into the 1960s, Bell Labs became enmeshed in the quest to build a working device that would give off stimulated emission of visible light. While Hughes Research Laboratories “won” the race when Ted Maiman fired up the first ruby laser in 1960, other industrial labs were poised to make other important strides. At Bell, Li and a colleague, A. Gardner Fox (1912-1992), delved into the theory of the laser cavity.

Fox was the senior member of the pair; he held a master’s degree from the Massachusetts Institute of Technology and for many years edited the IEEE Journal of Quantum Electronics. Speaking on the 50th anniversary of the laser in May 2010, 1999 OSA President Tony Siegman said that Fox had created the first microwave relay links for long-distance phone calls in the early 1950s.

The two researchers had access to their employer’s IBM 704 mainframe computer, which could process data at the then-respectable speed of 4,000 floating-point calculations per second. Li and Fox took the 1958 prediction by Arthur L. Schawlow and Charles H. Townes that the “optical maser” would require a resonant cavity with parallel reflective ends and calculated the modes that would appear between those reflectors.

“Fabry-Perot interferometers, whether of the plane or concave mirror type, are characterized by a discrete set of normal modes which can be defined on an iterative basis,” Fox and Li wrote. Their results suggested that curved mirrors would lower the losses in confocal cavities.

 

figureA. Gardner Fox (left) and Tingye Li in an undated Bell Laboratories file photo.

 

figureLi gives a talk at Bell Labs Crawford Hill to top AT&T executives in 1972, after Li’s research department had demonstrated the first successful optical repeater required for fiber transmission systems.

The pair published a short piece in the Proceedings of the Institute of Radio Engineers and a more detailed article in the Bell System Technical Journal. Thousands of researchers have cited one or both iconic papers over the years. “Fox and Li” became a phrase that conveyed instant meaning to anyone working in optics, according to Alan Willner, an electrical engineering professor at the University of Southern California.

Li joined Fox and another Bell Labs colleague, Gary D. Boyd, on a patent application for an optical maser cavity, filed 7 Oct. 1960 and granted on 25 Sept. 1962.

Lightwave communications

In the 1970s, Li became convinced that optical fibers had the potential to improve telecommunications. Writing for Optics News—the precursor to this magazine—in 1977, he explained the basic principles of optical communications: optical losses, the fiber-manufacturing process, dispersion calculations and so forth.

By the mid-1980s, Li had become director of Bell’s lightwave systems research department. He was already known for putting together teams of creative yet practical researchers; he often said, “I only hire people smarter than I.” No one from upper management had directed his group to pursue multiplexing, but he had a vision. He knew more data could be sent through optical systems.

Under Li’s direction, Bell researchers used erbium-doped optical amplifiers to create WDM systems, which created “virtual” fibers by putting multiple data channels down a single physical fiber. In 1991, the team traveled to Roaring Creek, Pa., and hitched their system to previously installed single-mode fiber cables. Their experiments yielded 2.5 Gbit/s transmission per channel, a huge jump in performance over existing networks, and Li dubbed it a “roaring success.” Dense WDM was here to stay; optical fiber transmission capacities increased exponentially, and the Internet became an economically practical tool for society.

Family matters

Li and his wife raised two daughters, Deborah (Cohen, right) and Kathryn (Dessau).

Growing up in New Jersey, Debbie was aware that her father enjoyed his job at a prestigious institution, but mostly she remembers the family routine. After a full business day, her father would come home and her mother would make a martini for him and a Manhattan for herself. After cocktails, the family would eat dinner and then listen to a poem that Tingye read aloud. As the daughters did their homework, Li would take a nap, then rise at 10 or 11 p.m. to sit at the kitchen table writing papers on legal pads, until 2 a.m.

Tingye was proud of his daughters’ achievements—Debbie graduated from medical school, while Kathy earned a Ph.D. in applied physics—and the families they built for themselves. He cultivated very close relationships with his four grandchildren, who called him “Gung Gung.”

“He was incredibly proud of us,” said Debbie Cohen. “Not even a waiter taking our dinner order was immune from hearing about all of our recent accomplishments.”

Mentoring around the world

Li’s approachability and earnest desire to connect with people earned him the nickname “Uncle Tingye.” He treated everyone with the respect and care, young and old alike. Li became a mentor to legions of young people and was an ideal role model.

He was continuously writing letters of recommendation for students and colleagues, agonizing over every word and often submitting the last (but perhaps best) letter. According to Willner, who credits Li for bringing him into OSA volunteerism, “most people did not even know that it was Tingye’s kind, gentle hand that helped them.”

When Li ran for vice president of OSA in 1992, a position that would culminate in presidency of the Society, he ran unopposed. According to other OSA members, nobody wanted to run against Li because of the strong prevailing feeling that he should lead the Society. “He was our leaders’ leader,” Willner said. “He was the person our leaders turned to for wisdom and advice.”

OSA’s 1997 President, Janet S. Fender, recalls socializing with Tingye and Edith Li at Society events. “Everyone loved Tingye, a kind and gentle human being with a spark and twinkle in his eye—and a ready smile on his face,” wrote Fender, chief scientist of the U.S. Air Combat Command at Langley Air Force Base. “A great sense of humor mixed with thoughtful seriousness, he had a very balanced personality.”

Willner recalls the warmth that Li showed to OSA staff members at the Society’s conferences and meetings. “Everyone he met was important to him,” Willner said. “He would give lots of hugs and ask people about their families.” (In 2006, when Li turned 75, more than 100 OSA employees posed on the steps of OSA headquarters in Washington, D.C., for a portrait for Tingye. He was delighted with the gift.)

Once he retired from AT&T Labs in 1998, Li embarked on a new phase of his career. Though nominally an independent consultant, he vigorously pursued two activities: mentoring the next generation of optical researchers and helping China to develop a modern telecommunications infrastructure. He made nearly 60 round trips between his native and adopted nations, advising Chinese telecom researchers and working to strengthen the relationship between China and the rest of the world. Numerous Chinese universities named him an honorary professor, and he was a driving force in getting the Asia Communications and Photonics conference off the ground.

In 2011, Li made his first visit to South Africa in nearly 60 years to receive an honorary doctorate from his undergraduate alma mater. In a letter to OSA staff, he expressed his joy that the country had advanced far in its tolerance of all people in the post-apartheid era.

 

figure Tingye Li on the ski slopes.

 

figureTingye and Edith touring the Huangpu River in Shanghai with friends during the 2010 Asia Communications and Photonics Conference.

When not traveling or mentoring, Tingye and Edith Li lived in Boulder, Colo., where ski slopes would be always nearby. In the late 1980s, Li had begun a tradition of gathering the family during Christmas week at Snowbird, a resort in the Wasatch Range of northern Utah. He had learned to ski at the ripe age of 40 and decided that his family ought to learn as well; the four of them had traveled to a small New Jersey ski area with a rope tow and learned how to get up and down the hill. As he aged, Li was pleased that he could finally ski at some resorts for free.

At the end of last year, he enjoyed a day of skiing on Wednesday, 26 Dec. The next morning, it was snowing, so he went for a swim in Snowbird’s pool, from which guests could view the distant mountains—perhaps the last thing Li saw before suffering a fatal heart attack.

Li’s legacy

In March, Li’s colleagues paid tribute to him with a special symposium at the OFC/NFOEC conference in California. The same month, his family and friends held a memorial service in Boulder. Kaminow, Li’s best friend for 50 years, was unable to attend the memorial due to health concerns, but he submitted a statement that read: “His enthusiasm for life was contagious, and his spirit touched so many people throughout the world.”

Friends remember Li saying that his goal was to leave the world a little better place than he had found it. Between the advances he made in communications technology, his work to bridge East and West, and his genuine, avuncular warmth, he certainly surpassed his goal. His grandson Scott is not alone in the sentiment he expressed in the last sentence of his fourth-grade essay: “I love to listen to him and wish I could have been with him and lived the life of Tingye Li.”


Patricia Daukantas is a freelance writer specializing in optics and photonics.


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Tingye Li: A Global Force in Optical Communications

Born into a world on the brink of war, Tingye Li shaped a communications industry that linked the world in peace. Li, the popular 1995 OSA President who died last December at 81, lived a truly global life.

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