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Smart Switches

Experts are quick to point out that even today’s most impressive optical switches represent only an early step in the evolution of functional optical devices. In a world of advanced microelectronics, today’s prototypes are still bulky-and they’re dumb. Although they can switch light beams with ease, they can’t read the messages carried in them. As a result, electronic devices must be used to control the photonic switches, telling them when and where to redirect the beams of light. That’s acceptable if the goal is simply to reconfigure the main pathways of light at the network hubs. But that initial goal certainly will not satisfy the ambitions of telecom providers for long. They would like to extend the full power of optical switching all the way to the end users, creating a truly “all-optical Internet.” And that means smarter optical switching.

The Internet is built around packets-strings of data that find their destination by hopping between local and regional “nodes” where the mesh of transmission lines that form the Internet intersect. E-mail a snapshot and it will be chopped into hundreds or thousands of packets that travel separately from node to node. Each packet carries with it an Internet protocol, or IP, address that is read by electronic switches called routers at each node. Whereas the switches at the network backbone can blindly shift an immense number of packets in bulk, routers must ponder each packet. The IP address tells the routers where the packet is going; the routers then forward it to the next appropriate node. This process is repeated across the Net until the individual packets that make up the snapshot have arrived at their destination, where they are reassembled.

This forwarding arrangement is part of what makes the Internet resilient. If a node goes down or is temporarily swamped, neighboring routers simply divert the flow of packets around it. However, routers are straining to keep pace with the surging Internet traffic, just like their electronic cousins in the network backbone. Each channel of light in today’s fastest fiber-optic cables transmits thousands of packets every second, with additional channels being squeezed in all the time. While electronic routers have managed to keep up with converting the optical signal to electrons and reading the IP address on each packet, they are now being pushed to their limits.

Herein lies the next big job for photonic switches. In tomorrow’s all-optical Internet, operating at speeds unimaginable with electronics and delivering that speed to your home PC, photonic switches must be smart enough to serve as routers by recognizing the packets of information and determining where they should go. In other words, the devices must have the speed of optics and the intelligence of microelectronics. And that will happen, say those in the field. “The future of networking is going to be optical IP switching,” says Gary Bjorklund, chief technology officer with Miami-based Nanovation Technologies.

To spur the creation of optical components that are far smaller and smarter, earlier this year Nanovation pledged $90 million over six years to finance research at MIT in the field of microphotonics. The goal is to emulate the integration of transistors and other electronic devices onto a chip by shrinking optical switches, fibers, lasers and detectors, and stringing them together on a single optical circuit. Just as stuffing together more and more transistors, diodes and capacitors has greatly multiplied the speed and power of microelectronics, both MIT and Nanovation are betting that integrated microphotonics circuits will deliver similar advances in performance.

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