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August 1997


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Alumnus Works to Improve Fiber Capability at Bell Labs

Making the jump from graduate student researcher to contributing member of a world-renowned industrial research team involves developing focus and perspective, according to Ashish Vengsarkar (MSEE, '88; Ph.D., '91), a technical manager at Bell Labs, the research and development arm for Lucent Technologies.

Vengsarkar made the jump successfully. Since joining Bell Labs in 1991 as a member of the technical staff, he has been responsible for developing two commercially successful products, in addition to working on other product teams, authoring more than 50 journal papers, and participating in 18 patents. In 1995 he was promoted to technical manager, and he now manages all of the firm's research and development activities related to fiber devices.

Joining a group like Bell Labs can be intimidating. "All the big heroes in the field are right across the hall from you...It gets you wondering how you can do path-breaking work," he says. "I did succeed in a few things...I was in a hot field at the right time. There were many unsolved problems, and I had a terrific boss," he notes.

"My eyes were opened by a group project headed by Ken Walker, a Bell Labs Fellow." The project involved reducing polarization mode dispersion (PMD) of optical fibers by a factor of 10. "If you send a pulse of light through a fiber, it will quickly spread because of PMD. Walker came up with the idea to reduce PMD. I was working on fiber measurements, jumped on the team, and made it a top priority. That project exposed me to what it takes to achieve a big breakthrough."

Vengsarkar went on to develop two commercially successful projects of his own - dispersion compensating fibers and gain equalizers.

The first project concerns yet another tendency of pulses to spread as they travel through a fiber - a property that limits the information a fiber can carry. Vengsarkar developed a fiber that would compress the spread pulses back to their original shape. "This project was a success primarily due to my collaborations with my preform-making and fiber-drawing colleagues."

His second commercial product involved the tendency of pulses to lose power as they travel through a fiber. Commercial optical amplifiers would return a pulse to its original intensity; but could not equally amplify multiple channels.

He invented a grating-based device that would select the channels that got the gain, and reduce the gain in the mid-section of an amplifier. "If we reduced the gain for these channels at the input, we would have further reduced the signal and added too much noise during amplification. If we reduced the gain at the output, we would be losing precious power. However, at the middle, we can even the gain and neither lose power nor introduce noise."

Lucent's system developers have used these gain-equalizers and set several world records for transmission capacity in fiber communications systems.

Vengsarkar particularly enjoyed the power distribution rectifier product, not only because of its commercial potential, but also because he was involved from initial concept through design, development, testing, and final production.

Vengsarkar credits his success with having a good background in both the theoretical and practical aspects of fiber optics, having a great mentor and developing a cost/benefit philosophy.

He has also been bolstering the Bell Labs team by recruiting graduates of Tech's fiber optics program. "I believe Virginia Tech's fiber optics program is fantastic," he says. "In fact, we have recruited three students from the program, who are now full-time members of Bell Labs."

The Bradley Department of Electrical and Computer Engineering
Virginia Tech

Last Updated, November 23, 1997
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