Engineers from the University of California, San Diego in the US have
smashed the current limit, by deciphering information that had been sent
through fibre optic cables across a record-breaking distance of 12,000
km, without having to regenerate the signal. That means their signal was
nearly 20 times stronger than our cables can currently handle.
now, when we send information over a certain distance, we need to use devices called 'repeaters'
along the cable to convert the data into an electrical signal. This
slows the system down and limits how much information can be sent, but
it's necessary because our optical signals just can't handle that much
power without being distorted an unrecognisable amount.
"Today’s fibre optic systems are a little like quicksand," lead researcher Nikola Alic explains in a press release. "With quicksand, the more you struggle, the faster you sink. With fibre optics, after a certain point, the more power you add to the signal, the more distortion you get, in effect preventing a longer reach."
"Our
approach removes this power limit, which in turn extends how far
signals can travel in optical fibre without needing a repeater,” he adds.
To
avoid this distortion, which is known as 'crosstalk', the team first
had to study it closely and map the interaction that occurred between
the various channels of fibre optic cables. "Crosstalk between
communication channels within a fibre optic cable obeys fixed physical
laws. It’s not random," says Alic. And this means they could learn how to predict it.
His
team then created a 'frequency comb' - a device that predicts and
reverses crosstalk - which allowed them to send 20 times stronger
signals through fibre optic cables, without the need for regenerators.
Alic compares
it to a conductor tuning up an orchestra at the start of a performance:
by synchronising the starting point of the signals using the frequency
comb, the team can ensure that they are deciphered without distortion on
the other end, even if they've been blasted over 12,000 km.
The
researchers now need to work on getting these frequency combs integrated
into existing fibre optic cables. But once they do, they not only have
the potential to make fibre optic cables more efficient and remove the
'speed limit' currently set on the Internet, but it could also greatly
reduce the cost.
Source: UC San Diego News Centre
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