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Optical/IP

Luxcore to Demo Optical Switch Advance

Luxcore Networks Inc. is planning to demonstrate a significant development in all optical switches at the Optical Fiber Communications(OFC) Conference in Anaheim, California, next week.

The startup will show a working prototype switch incorporating optical rather than electrical wavelength conversion – a development that could help carriers slash costs considerably.

Understanding this can be a little tricky, but the argument goes like this. First generation all-optical switches are fairly limited in what they can do. In their simplest form, they act like automated patch-panels, steering all the light from one fiber into another.

In their more sophisticated form, they're integrated with DWDM systems so that light is split into different wavelengths before it’s switched. In this case, the wavelengths coming out of one fiber can be routed into different fibers.

The big catch, however, is that the switch can’t change the wavelength of the light without converting it into electrical signals and retransmitting it – and this OEO malarkey is exactly what all-optical switches are supposed to eliminate.

Optical wavelength conversion promises to avoid this snag, but that’s only for starters.

Being able to shift light from one wavelength to another can be used to sidestep issues of one stream of signals blocking the path of another stream within a switch, according to Gerald Ramdeen, Luxcore’s combined CEO and CTO. As a result, the same capacity switch needs significantly less switching fabric if optical wavelength conversion is employed, he says. That equates to "less power, less space, less cost - and that's exactly what customers want", Ramdeen adds.

Luxcore’s way of doing optical wavelength conversion also appears to give its switch another plus. Light signals get a boost of power as they pass through. Ramdeen is cagey about giving details. “We’re using tunable lasers as a programmable pump source,” he says, adding: “We’re doing frequency mixing without all the nasty side effects.”

Our reading of this is that Luxcore’s using semiconductor optical amplifiers (SOAs). The tunable laser pumps different wavelengths of light into the SOA to change the wavelength of the light carrying the actual data.

Now for some details. Luxcore’s switch, called the LambdaXchange, will come in two sizes. The first one will have will eight input fibers and eight output fibers and a capacity of 20 terabit/s. The second one will have 16 input fibers and 16 output fibers and a capacity of 120 terabit/s. Both models will incorporate some state of the art DWDM technology – 240 channels, 80 in the C band, 80 in the L band and 80 in the S band.

The switch is formed from two subsystems. The first one incorporates wavelength multiplexers and wavelength converters, which also amplify light signals, as already noted. This subsystem also incorporates come unspecified components that reshape signals optically.

This first subsystem marshals the different streams of light from the carrier’s fiber infrastructure and feeds it into the second subsystem, the switching fabric. Right now, Luxcore is using MEMS (micro-electro-mechanical system) switching fabric, although Ramdeen points out that his switch “wasn’t engineered around MEMs”. It would be straightforward to replace the subsystem with something else, if it seemed appropriate.

Luxcore’s demo at OFC will be of a smaller switch, with just two input and two output fibers. It will support 40 wavelengths per fiber. The startup plans to demonstrate wavelength routing, optical wavelength conversion, add-drop functions and broadcast functions, according to Ramdeen. “We hope this is going to be the first example of optical wavelength conversion,” he says. “We’ll know on Monday whether it really is.

Luxcore expects to start shipping commercial versions of its switch in the fourth quarter of this year. It has 125 staff. It raised $10 million in series A financing last July (see Luxcore Raises $10m First Round) and is planning to start raising further funding soon. “We purposely delayed our next round until after OFC,” says Ramdeen. Originally, Luxcore was called Synchordia (see Startup Touts "First Optical Router").

-- Peter Heywood, international editor, Light Reading http://www.lightreading.com
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