Optical chip could lead to terabit Ethernet

Danish and Australian researchers have developed a chip that efficiently reads 640Gbps optical transmissions and could help pave the way to terabit Ethernet.

The breakthrough comes not on the laser end of the connection by boosting the speed of transmission, but rather at the receiving end where very high speed, error-free reception is required to sort out multiple wavelengths of signals that have been multiplexed at the sending end.

The discovery comes just as 100Gbps Ethernet is in its infancy but predicted to become more common over the next three years.

The new receiver technology described in an article to be published Feb. 16 in the journal Optical Express relies on a 5 cm optical waveguide, a dramatic reduction in size over competing technology that requires 50 meters of special optical fiber and is inherently unstable, according to the Optical Society of America.

The researchers say the compact size of their waveguide makes it possible to integrate it with other components to make faster optical chips.

Current top-speed optical networking employs optical time-division multiplexing (OTDM) that creates 64 10Gbps channels on a single wavelength, according to Leo Spiekman, a co-chairman of the Optical Fiber Communication conference scheduled for March in San Diego, Calif.

In order to demultiplex such an OTDM stream, a second control wavelength of light is introduced to the signal stream to read a particular channel. In current demultiplexers, that process takes place on spools of fiber where the length is so great that the signal and the control streams get out of phase, he says. The device from the researchers is short enough so this dispersion is not a problem, Spiekman says.

The experimental all-optical demultiplexing is done with a chip made of the material chalcogenide, the researchers say.

"You need this type of technology to make terabit speeds on single channels," Spiekman says. "This is one of the enablers for you to go to terabit Ethernet at some point in the future."

The researchers are led by Leif K. Oxenløwe of the Technical University of Denmark and scientists at the Centre for Ultrahigh Bandwidth Devices for Optical Systems in Australia.

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