Optical Digital Signal Processor Boosts Speeds
Perry J. Greenbaum
A new approach to signal processing promises to reduce bottlenecks in telecommunications networks. Lenslet Labs Ltd. of Ramat-Gan, Israel, has developed an optical digital signal processor that operates thousands of times faster than today's electronic ones.
The technology takes multiple electronic digital input signals, converts them into optical signals, performs the desired computation and then converts the optical output signals back into digital electronic form. The processor is intended to fit snugly on a board in a standard rack.
"End to end, it's an electronic system," said Avner Goren, Lenslet's vice president of marketing and business development. "But internally, it's an optical system."
Unlike most digital signal processors, Lenslet's optical core, which it has trademarked as EnLight256, uses mathematical transforms that work well for wireless technologies, which require multichannel correlations. Equally important, the optical engine may be tailored to the type of transform that is required.
Optoelectronic conversion has been attempted numerous times, mainly with liquid-crystal technology. That approach, however, results in a bottleneck, mainly because it is limited to speeds of 200 Hz, a far cry from the needed gigahertz range.
1012 operations per second
The company instead combined commercially available light modulators that operate in the gigahertz range with algorithms that encode, condition and decode the signal. "The [intellectual property] is in the surrounding electronics, the encoding, the decoding and signal conditioning," Goren explained. "That enables us to use standard off-the-shelf light sources."
Lenslet says that the optical engine, which can perform up to 1012 operations per second, is suited to applications that require a high degree of processing power and high levels of parallelism.
Target applications include wireless base stations, digital subscriber line modems and digital audio broadcast. In these areas, the EnLight256 will compete against electronic digital signal processors and application-specific integrated circuits.
The company estimates that one optical engine can replace 10 application-specific integrated circuits, but will use one-quarter the board space, consume one-fifth the energy and cost half the price.
The company expects to release more details of the engine's internal architecture in March.
"Once you see the optical structure, you will be surprised how simple it is," Goren said, adding that a camcorder is much more complicated, optically. "We are using optics that have been around since the 19th century."
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