Pointy pulses improve optical fiber throughput by a factor of 10
By Darren Quick
December 5, 2013
As the volume of data carried around the world via optical fibers continues to increase, researchers at the Swiss Federal Institute of Technology in Lausanne (EPFL) have found a way to increase data throughput capacity by ten times. Because it is based on changing the shape of light pulses to reduce the space between, the breakthrough would work on existing optical fiber infrastructure.
"Since it appeared in the 1970s, the data capacity of fiber optics has increased by a factor of ten every four years, driven by a constant stream of new technologies," says Camille Brès, of the EPFL's Photonics Systems Laboratory (PHOSL). "But for the last few years we've hit a sort of ceiling, and scientists all over the world are trying to break through."
While others have attempted to solve the problem by altering the properties of the fibers themselves, Brès and fellow EPFL scientist Luc Thévenaz claim to have broken through the current throughput ceiling by focusing on the pulses of light that travel through them.
Data is transmitted through optical fibers as a series of light pulses that form codes. Simply put, a transmitter at one end sends an "on" pulse to signify a 1, and an "off" pulse to signify a 0, with the pulses decoded at the receiving end of the fiber. The limiting factor has been that there needs to be some space between the pulses so they don't interfere with each other, ensuring the data can be reliably decoded at the receiver.
After noticing that the changes in the shape of the pulses could limit the interference, Brès and Thévenaz were able to produce long-sought-after "Nyquist sinc pulses" that fit together more closely.
"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 Brès. "There is of course some interference, but not at the locations where we actually read the data."
The researchers were able to generate a pulse that is more than 99 percent perfect using a simple laser and modulator, but believe the technology could fit on a simple chip. This, coupled with the fact that existing optical fiber networks wouldn't need to be replaced, should make it attractive to many in the telecommunications industry.
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