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Meet a Scientist: Dr. Siddharth Ramachandran

As a Distinguished Member of Technical Staff of OFS Laboratories, Dr. Siddharth Ramachandran's primary research interests include optical physics with a focus on understanding and exploiting optical phenomena and the underlying materials systems to invent photonic devices in applications such as sensors, imaging systems, high-power and ultra-short lasers, and telecom systems.

Specifically, much of his recent work involves specialty fibers that are intentionally "few-moded." Multimode fibers are normally considered to be susceptible to a host of problems related to the fact that a light signal can randomly "hop" from one mode to another. Since each mode represents a distinct path for the signal to follow, such random hopping makes a system noisy, and thus undesirable. For these reasons the fiber optics community has avoided using higher order modes.

Dr. Ramachandran and his team theorized that these problems could be overcome by introducing the light into only one mode of a few-moded fiber that was designed so that the signal never randomly hops to another mode. "We succeeded in this effort by using specialty fibers made with our in-house modified chemical vapor deposition fiber fabrication technology, and by coupling light to desired modes with unprecedented modal purity," he recalls.

"What we found is that a fiber that is carefully designed to support not just one mode, but a few (typically 2-10), leads to several benefits," he explains. "Fundamentally, the higher the mode, the greater the design flexibility in obtaining substantially superior technical performance."

In terms of applications, some areas that may benefit from this research include dispersion compensation for long-haul telecom systems, dispersion engineering for ultra-short fiber lasers, and ultra-high power fiber lasers.

Dr. Ramachandran  received a Bachelor of Technology in Metallurgical Engineering from Indian Institute of Technology, Kanpur. At the University of Wisconsin, Madison he received a Masters of Science degree in 1993 and a Ph.D. in Electrical Engineering in 1998. His thesis topic was "Photonic integrated circuits and bulk photonic devices in chalcogenide glasses."

In 1998 he joined Bell Laboratories as a member of the technical staff. He remained on the staff when OFS acquired Bell Laboratories, and was named as a Distinguished Member of Technical Staff of OFS Laboratories in 2003. He has 18 invention records (patent submissions) filed and 11patents granted.

Very active in research and industry organizations, Dr. Ramachandran has had more than 100 papers published in scientific journals or presented at conferences. He is also author of two book chapters and served as editor in the Optical Fiber Communications Series (Springer, New York, 2006). He serves on a variety of panels of such professional organizations as the United States National Science Foundation, the Science Foundation of Ireland, IEEE, OFC, and the Optical Society of America.

Dr. Ramachandran is constantly stimulated by the challenges of producing ever more complex fibers for ever more demanding applications. "It's the core strength of OFS and a primary goal of the Specialty Photonics Division," he says. "The immense technical resources – ranging from fiber fabrication to systems demonstration – available at OFS Labs to researchers like me makes it an extremely exciting place to work."

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