18 February 2009—The day an average telecom carrier can send 1 trillion bits (one terabit) of data per second down a single optical fiber may still be many years away. But in the lab, the single-fiber terabit threshold may well be crossed just one or two years from now, thanks to recent research.
Two groups of engineers—one from Australia and Denmark and the other from California—have independently created new optics technologies that could greatly increase the Internet’s speed limits. The key to the new technologies is nonlinear optics, in which physics allows for an optical fiber’s properties to be adjusted from moment to moment.
On the Internet, packets of data are carried mostly by laser light over optical fibers. But in order to route a data packet through each leg of its trip, the address of the packet’s destination must be decoded. This can be done only electronically, by converting the data’s photons into electrons. The electronics are the horse and buggy of the system—unable to keep pace at even a fraction of the bits per second that an optical fiber can handle.
Two leading contenders in the terabit Internet race involve tunable optical fibers and tunable arsenic-glass chips. In both cases, lasers transmit the signal’s zeroes and ones, while a separate laser (or set of lasers) adjusts the properties of the optics in order to ”demultiplex,” or break up, the data into separate streams whose data is in the right range for electronics.
”The highest bit rate that you can do electrically is 40 gigabits per second right now,” says Leif Katsuo Oxenlowe, associate professor of photonics engineering at the Technical University of Denmark, in Lyngby. ”That’s at least what’s commercially available. In labs around the world, [electronics is] reaching 100 Gb/s.”
Oxenlowe says his group of 13 scientists—led by Benjamin Eggleton at the Centre for Ultrahigh Bandwidth Devices for Optical Systems (CUDOS), which is part of the Laser Physics Centre at the Australian National University in Canberra—has been testing a 5-centimeter-wide glass chip that can receive optical signals of up to 640 Gb/s and, when a laser periodically changes the chip’s index of refraction billions of times per second, siphon off a 10 Gb/s signal. That slower signal, in turn, can then be piped into a standard electronic router.