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  • Router Promises Faster Switching

Photonics Spectra
Aug 2001
Kevin Robinson

DAVIS, Calif. -- An all-optical data network scheduled to be built later this year at the University of California may herald the future of the Internet: unbelievably fast switching that could make the promise of real-time, 3-D videoconferencing and other high-bandwidth applications a reality. The heart of the system is an all-optical router, the brainchild of S.J. Ben Yoo, a professor of electrical and computer engineering at the university.

The routers in the all-optical network scheduled to be built at the University of California use wavelength conversion to resolve contention. Conversion enables the system to switch wavelengths to avoid bottlenecks on busy fibers. Courtesy of S.J. Ben Yoo.

Yoo characterizes optical networking technology in terms of generations, based on how much of the switching is done optically. In the first generation, which is currently in place, he said, the fiber component of the network is "a dumb, fat pipe" that offers long-haul, high-bandwidth transmission from point to point. Expensive electronics separate and switch each channel.

Second-generation technology reconfigures circuits without converting the signals via electronics, but individual packets of information, such as a browser's request for a Web page, still must be converted to an electronic signal and processed before switching. With Yoo's optical routing, however, the data remains in optical form until it reaches its destination.

Yoo's development incorporates a short, optical label that contains the routing information for each data packet entering the router. The router reads this label, checks the traffic conditions on the network ahead and sends the packet on with a new optical label.

He explained that today's routers read the forwarding information for an incoming packet, compare it against a routing table and forward the packet accordingly. The problem is that if there is contention, when more than one packet is slated to go to the same output, the routers hold the packet until this condition disappears over time, at the expense of transmission rates.

The all-optical system, by contrast, uses the optical network's wavelength-conversion capabilities for contention resolution. Bringing time, space and wavelength domains to bear on contention resolution is far more effective than relying on time domain, Yoo said.

Petabit switching

A 1997 method for improving contention resolution, called multiprotocol label switching, integrates data networking and supports a number of protocols, but it does not take advantage of optical networking capabilities, he said. A newer version, MPLambdaS, falls short, too: It switches the optical circuits but not the data packets. The optical-label switching incorporated in Yoo's optical router better integrates data and optical networking.

In the long run, an all-optical Internet could display transmission rates higher than 1 Tb/s, possibly as high as 10 Tb/s on each fiber, requiring petabit-per-second switching capability at the node. "Our optical router can achieve this and much more," Yoo said.

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