Faster, cheaper internet in the offing

In a breakthrough that could lead to superfast, cheaper internet, researchers have increased the maximum power, and the distance, at which optical signals can be sent through optical fibres.
Electrical engineers have broken key barriers that limit the distance information can travel in fibre optic cables and still be accurately deciphered by a receiver.
This advance has the potential to increase the data transmission rates for the fibre optic cables that serve as the backbone of the internet, cable, wireless and landline networks, researchers said.
The study presents a solution to a long-standing roadblock to increasing data transmission rates in optical fibre: beyond a threshold power level, additional power increases irreparably distort the information travelling in the fibre optic cable.

"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," said Nikola Alic, a research scientist from the Qualcomm Institute at the University of California, San Diego.
"Our approach removes this power limit, which in turn extends how far signals can travel in optical fibre without needing a repeater," said Alic, study corresponding author.

In lab experiments, the researchers successfully deciphered information after it travelled a record-breaking 12,000 kilometres through fibre optic cables with standard amplifiers and no repeaters, which are electronic regenerators.
The new findings effectively eliminate the need for electronic regenerators placed periodically along the fibre link.

These regenerators are effectively supercomputers and must be applied to each channel in the transmission.
The electronic regeneration in modern light-wave transmission that carries between 80 to 200 channels also dictates the cost and, more importantly, prevents the construction of a transparent optical network.
As a result, eliminating periodic electronic regeneration will drastically change the economy of the network infrastructure, ultimately leading to cheaper and more efficient transmission of information.
The breakthrough in this study relies on wideband "frequency combs" that the researchers developed.
The frequency comb ensures that the signal distortions - called the "crosstalk" - that arises between bundled streams of information travelling long distances through the optical fibre are predictable, and therefore, reversible at the receiving end of the fibre.

"We present a method for leveraging the crosstalk to remove the power barrier for optical fibre," said Stojan Radic, from UC San Diego and the senior author on the research paper published in the journal Science.