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Fiber Optic Transmission Range Could See a Big Boost

July 15, 2015 By Molly White in

A potentially big breakthrough for optical networking comes from the University of California at San Diego, where photonics researchers have raised the maximum power at which optical signals can be sent over fiber, thereby extending transmission range.

According to a report published by UCSD News, the UCSD research team set a new record by enabling digital data to travel 12,000 kilometers (~7456 miles) over fiber optic cables using off-the-shelf amplifiers and no repeaters.

In the UCSD News article, Qualcomm Institute research scientist and corresponding report author Nikola Alic likened today’s fiber optic systems to quicksand.

“With quicksand, the more you struggle, the faster you sink,” he was quoted as saying. “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.”

Fiber Optic Transmission Range

The breakthrough method eliminates the need for electronic regenerators that telecom, cable and Internet service providers need to install along network transmission lines. These devices are used to boost the power for each of the 80 to 200 channels used in the transmission of light waves, UCSD News’ Liezel Labios explains. Network operators could potentially reduce infrastructure costs by making use of the new method.

The research team developed and used a type of optical signal transmission device called wideband frequency combs to achieve their barrier-breaking results. These optical electronic structures are able to reverse the crosstalk that distorts light wave signals and thus limits the rates and distances that signals can travel.

“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,” elaborated Stojan Radic, a professor in UCSD’s Department of Electrical and Computer Engineering and the senior author on the Science paper.

“In this study, we present a method for leveraging the crosstalk to remove the power barrier for optical fiber. Our approach conditions the information before it is even sent, so the receiver is free of crosstalk caused by the Kerr effect.”

The photonics researchers used the frequency combs they developed to synchronize the variations in various communications channels within a fiber optic strand. According to the researchers, this approach compensates in advance for the crosstalk that occurs between the multiple channels within the same fiber. It also ensures that the crosstalk between the communication channels can be reversed at the receiving end, the researchers said.