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

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.

But Willner says the new optical system he and Hellwarth are building will provide another way, in which data can stay photonic and pass through at extremely high speed.

Their technique is to convert the photonic information from one color to another one, and then pass the data through an element that has a speed of light which is dependent on the color of the light - i.e., red photons could travel slower than blue photons. Each photonic data stream is given its own "color," or delay value, and then seamlessly woven together and sent on their common way without ever going through an electronic interface.

Willner has already succeeded in efficiently delaying a single 80-Gigabit/s data stream and multiplexing two separate 40-Gigabit/sec data streams. His plans call for upping capacity to the 100's-of-Gigabit/sec range.

Multiplexing is only part of the suite of applications. Another is buffering. A complete rundown of the benefits of a tunable system from the proposal: it could allow "accurate synchronization for bit-level interleaving, time-slot interchange, multiplexing and demultiplexing, time switching, and data packet synchronization."

The system that the USC team proposes comes out of recent research by Willner and others worldwide in creating systems that use new techniques to slow light down. For all these applications, a high degree of delay control is needed in the ability to continuously tune the timing of the high-speed-data flow.

The design goal is a system that can tunably slow light from 0 up to 5 microseconds - that is, a slowed stream can arrive up to 5 microseconds later than an untreated on; the 5 microsecond delay would require a roughly 50 fold improvement on their current published value of 100 nanoseconds.

To put this in perspective, a delay of 5 microseconds for a 500-Gbit/sec data stream is the same as delaying a data stream by millions of bits, an amount that could open up many possible applications.

Source: University of Southern California

Related stories:

'The photon force is with us': Harnessing light to drive nanomachines
Science fiction writers have long envisioned sailing a spacecraft by the optical force of the sun's light. But, the forces of sunlight are too weak to fill even the oversized sails that have been tried. Now a team led by researchers at the Yale School of Engineering & Applied Science has shown that the force of light indeed can be harnessed to drive machines — when the process is scaled to nano-proportions.
Ultra-wideband radio rides a beam of light
(PhysOrg.com) -- Multiple high-definition videos and other data-rich services may soon stream through homes, offices, ships and planes via new hybrid optical/ultra-wideband-radio systems developed by European researchers.
New research field promises radical advances in optical technologies
(PhysOrg.com) -- A new research field called transformation optics may usher in a host of radical advances including a cloak of invisibility and ultra-powerful microscopes and computers by harnessing nanotechnology and "metamaterials."
Brightening the future for optical circuits
(PhysOrg.com) -- By working together to share costs and know-how, European researchers are shaking up the way research and development is carried out on optical chips.
A broadband single-photon source
As science makes progress toward practical quantum computing, improved quantum cryptography and scalable quantum communications systems, single photon sources will become more important. Until now, though, efficient solid-state single photon sources are hard to come by. “The standard procedure,” Peter Lodahl tells PhysOrg.com, “has been to put a quantum dot in a photonic crystal cavity.”
Using 'slow light' to modulate single photon wavepackets
(PhysOrg.com) -- Single photons have been studied for a long time, Steve Harris tells PhysOrg.com. “But this is the first time that their wavepackets have been modulated.” Just as electrons may be described as either particles or waves, photons may also be described as particles or waves, and “in a similar manner to classical pulses of light their wavepackets may be modulated to encode additional information.” Harris immediately notes that over the last several years that several groups of scientists have used other techniques to generate shaped photonic wavepackets.
Future nanoelectronics may face obstacles
(PhysOrg.com) -- Combining ordinary electronics with light has been a potential way to create minimal computer circuits with super fast information transfer. Researchers at Umeå University in Sweden and the University of Maryland in the U.S. are now showing that there is a limit. When the size of the components approaches the nanometer level, all information will disappear before it has time to be transferred.
Northeastern University Physicists Develop Nano-Optical Lens
(PhysOrg.com) -- Using semiconductor nanotechnology, Srinivas Sridhar, Ph.D., Distinguished Professor and Chair of Physics at Northeastern University, and his team of researchers from the university’s Electronic Materials Research Institute have created a new microlens that focuses infrared light at telecommunication frequencies.

News discussion:

Physics news