Slowing light to speed data: USC Viterbi School wins $4.3M photonics IT contract

Award builds on previous success in blending laser information streams using tunable time delays

Two prize-winning USC specialists hope to break a bottleneck that has long limited communication systems from using light - photons - instead of electronics for data information processing.

Alan Willner and Robert Hellwarth, both professors in the USC Ming Hsieh Department of Electrical Engineering, have received $4.3 million in DARPA funding to develop "continuously tunable optical delays," which they hope will change the rules of manipulating photonic data at ultra high speeds.

"The technical community is missing a simple way to tune the time delay of one photonic data stream relative to another, which is a key building block for many types of data-processing functions," said Willner. "We think we've found it."

According to Willner, 2006 President of the Institute of Electrical and Electronic Engineers' (IEEE) Lasers and Electro-Optics Society (LEOS), optical fibers can carry enormous volumes of information coded in photonic form, with far greater bandwidths than metal electrical cables.

Still, "photonics usually can't compete with electronics when it comes to processing data," says Willner, "because silicon transistors are extremely cheap and can perform processing operations that have long been very difficult to do with light. With electronic systems, it is easy to temporarily store information. "

"Therefore," he continued, "we are left with a significant mismatch - data transmission is performed optically but data processing is done electronically. Normally, transmitted photonic data would need to be turned into electronic data for processing and then turned back into photonic data for further transmission."

Willner says that if such photonic-electronic conversions can be avoided, great savings in expense and energy are possible.

For example: numerous low-speed branch data streams can feed into larger trunk lines. While the trunk cable has more than sufficient capacity to carry all the information, before it can do so, the information has to be 'multiplexed' - i.e., the data bits and packets must be collated in such a way that different channels don't interfere with each other within the same time slot.

To do this now, the laser-coded information has to be converted into electronic form, multiplexed, and then reconverted to laser pulses. "This is energy inefficient, cumbersome, and takes away system capacity," says the scientist.