Optical Prime Time

As the load on communications systems multiplies, optical networks must become far more complex and interconnected. To fully optimize the flow of information along these networks, engineers need flexible and inexpensive ways to route the light. But at least one roadblock stands in the way: the lack of cheap, small, simple switches to direct the light. To help ease the congestion, scientists at Lucent Technologies’ Bell Labs have built a tiny optical switch that works like a seesaw.

“It’s basically a mechanical shutter” measuring about 100 micrometers across (about one-tenth the width of a human hair), says David Bishop, head of Bell Labs’microstructure physics research.The micro seesaw is made of a pivoting bar with a goldplated mirror at one end and an electrode at the other.The mirror is positioned between optical fibers.When the switch is off, the mirror rests below the fibers, allowing light to flow between them.When a voltage is applied to the electrode, it’s pulled down, swinging the mirror up between the optical fibers-and redirecting the light.

The switch is meant to be far smaller and cheaper than today’s technology. Existing devices based on lithium niobate crystals are fast but are also extremely expensive, costing roughly $1000 apiece; mechanical switches made of lenses and motors can also be used but are about the size of a pack of cigarettes, making them awkward as optical networks are miniaturized.

Lucent’s tiny switches, says Bishop, could be orders of magnitude cheaper than these devices, because large numbers can be made using the silicon technology used to fabricate integrated circuits.”This changes your notions of how you use optical switches and where you put them,” says Bishop.

Bishop points to potential use of the devices as tools for adding or dropping specific wavelengths of light in optical networks and as switches that reconfigure networks on demand.And, says Bishop, the micro switches could help facilitate the use of fiber optics in household and desktop applications-uses that require cheap and simple ways to route light.

Bishop says Lucent expects to commercialize the new switches “shortly.”The switches, he says, are now “ready for prime time.”


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