Researchers at the University of California – San Diego announced a breakthrough in photonic transmission with the potential to increase the efficiency of long haul fiber optic cables.
Research published in the June 26 issue of the journal Science describes a solution to a long-standing roadblock to increasing data transmission rates in optical fiber: beyond a threshold power level, additional power increases irreparably distort the information travelling in the fiber optic cable.
“Today’s fiber optic systems are a little like quicksand. With quicksand, the more you struggle, the faster you sink. With fiber 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 fiber without needing a repeater,” said Nikola Alic, a research scientist from the Qualcomm Institute, the corresponding author on the Science paper and a principal of the experimental effort.
In lab experiments, the researchers at UC San Diego demonstrated transmission over a distance of 12,000 kilometers with standard amplifiers and no repeaters (electronic regenerators). The breakthrough relies on wideband “frequency combs” that the researchers developed. The frequency comb described in this paper ensures that the signal distortions — called the “crosstalk” — that arises between bundled streams of information travelling long distances through the optical fiber are predictable, and therefore, reversible at the receiving end of the fiber.
“Crosstalk between communication channels within a fiber optic cable obeys fixed physical laws. It’s not random. We now have a better understanding of the physics of the crosstalk. In this study, we present a method for leveraging the crosstalk to remove the power barrier for optical fiber,” explained Stojan Radic, a professor in the Department of Electrical and Computer Engineering at UC San Diego and the senior author on the Science paper. “Our approach conditions the information before it is even sent, so the receiver is free of crosstalk caused by the Kerr effect.”
