Reference:
http://www.sciencedaily.com/releases/2013/12/131204091423.htm (collected)
Optical fibers carry data in the form of pulses of light over distances of thousands of miles at amazing speeds. However, their capacity is limited, because the pulses of light need to be lined up one after the other in the fiber with a minimum distance between them so the signals don't interfere with each other. This leaves unused empty space for data in the fiber.
EPFL's Camille Brès and Luc Thévenaz have come up with a method for fitting pulses together within the fibers, thereby reducing the space between pulses.This opens the door to a ten-fold increase in throughput in our telecommunications systems.
Traffic problems on the information superhighway:
In modern telecommunications exchanges, for example when two cell-phones are communicating with each other, the data are transported between the two antennae on optical fibers, by means of a series of light pulses that form codes.
Simply put, an "on" pulse corresponds to the number 1, while an "off" pulse corresponds to 0. The messages are thus sets of ones and zeros. These codes are decoded by the receiver, providing the initial message. The problem with this system is that the volume of data transmitted at one time can't be increased. If the pulses get too close together, they no longer deliver the data reliably. "There needs to be a certain distance between each pulse, so they don't interfere with each other," says Luc Thevenaz, of EPFL's Fiber Optics Group (GFO). However, the EPFL team noticed that changes in the shape of the pulses could limit the interference.
Pulses that fit together like a jigsaw puzzle:
Their breakthrough is based on a method that can produce what are known as "Nyquist sinc pulses" almost perfectly. "These pulses have a shape that's more pointed, making it possible to fit them together, a little bit like the pieces of a jigsaw puzzle lock together," says Camille Brès. "There is of course some interference, but not at the locations where we actually read the data."
The first to "solve" the puzzle:
The idea of putting pulses together like a puzzle to boost optic fibers' throughput isn't new. However, the "puzzle" had never been "solved" before: despite attempts using sophisticated and costly infrastructures, nobody had managed to make it work accurately enough -- until now. The EPFL team used a simple laser and modulator to generate a pulse that is more than 99% perfect.
The technology is already mature:
The new pulses could well generate interest among many telecommunications-industry market participants. The technology is already mature, as well as 100% optic and relatively cheap. In addition, it appears that it could fit on a simple chip.
