Time Lens Speeds Up Optical Data Transmission

Time Lens
This silicon chip is patterned with waveguides that split optical signals and combine them with laser light to speed data rates.
Credit: Alexander Gaeta

(PhysOrg.com) -- Researchers at Cornell University have developed a device called a "time lens" which is a silicon device for speeding up optical data. The basic components of this device are an optical-fiber coil, laser, and nanoscale-patterned silicon waveguide.

Current methods for speeding up optical data transmission require bulky and expensive optical equipment and consume a lot of energy. This new device is both energy efficient and is incorporated on a chip. This makes it ideal to move large quantities of data, at speeds up to 270 gigabits per second over telecommunication facilities and other optical devices.

Alexander Gaeta, Cornell University Professor of Applied and Engineering Physics, explains: "As you get to very high data rates, there are no easy ways of encoding the data." Alexander Gaeta has been one of the foremost developers of the new silicon time lens, alongside with his colleague Michael Lipson, who is a Cornell University associate professor of electrical and computer engineering. Their accomplishment can be found in the latest issue of the renowned scientific journal, Nature Photonics.

Keren Bergman, Columbia University Professor of Electrical Engineering, explains: "Power consumption is becoming a more constraining issue, especially at the chip level. You can't have your laptop run faster without it getting hotter." Optical chips can make computers run much faster without generating the un-necessary heat. Using an ultrafast modulator, it can compress data encoded with standard equipment to very high speeds.

The "time lens" uses a signal encoded on laser light using a conventional modulator. The modulated light signal is then attached to the silicon chip through an optical-fiber coil that sends it to a nanoscale-patterned silicon waveguide. On the chip, the signal interacts from a laser, which causes it to split up into different frequencies. The light travels through another strand of fiber cable and sends it to another nanoscale-patterned silicon waveguide, where it interacts with light from the same laser. In the process the signal is re-assembled but with its phase changed. The signal leaves the via another fiber cable at 270 gigabits per second.

The physics behind the process is very complex but the outcome is accomplished by taking a stream of bits that are traveling slow and making them travel much faster, says Keren Bergman.

By staying with silicon, "you can leverage all the technologies that have been developed for electronics to make optical devices," says Alexander Gaeta of Cornell University.

Via: Technology Review

© 2009 PhysOrg.com

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