Hindsight is 20/20. In February of 1995, Newsweek published an article titled “The Internet? Bah!” wherein the author deemed the hype surrounding an online future to be a large helping of “baloney.” Twenty years later, fiber optic cables buried in the ocean floor carry over 99 percent of that so-called drivel to millions of people – who rely upon the data like never before. Currently, 299 cable systems are active, under construction or expected to be fully funded by the end of 2015. But there’s only so much they can carry.
“The global demand for Internet data is rising at a phenomenal pace,” said Dr. Robert Maher at University College London. “And within a short period of time, about 10 years, this demand will exceed the amount of data we can currently send over a fiber cable.”
As data needs increase, more frequencies of light are being packed into fiber cables. Unfortunately, large numbers of light frequencies in one cable can distort and interact with each other in negative ways, causing errors in data reception. Maher and his colleagues alleviate this crunch by demonstrating a new way to process fiber optic signals, potentially doubling the distance at which data travels error-free through transatlantic submarine cables. The method also reduces the cost of long-distance optical fiber communications by making electronic signal boosts superfluous, a welcome change for buried or submarine cables.
“By eliminating the interactions between the optical channels, we are able to double the distance signals can be transmitted error-free from 3190 to 5890 km, which is the largest increase ever reported for this system architecture,” Maher said. The researchers had to devise a technique that would simultaneously capture a group of optical channels – a superchannel – with a single receiver. Distortion was then undone by sending the data channels back on a simultaneous “virtual digital journey.”
A DP-16QAM superchannel was used to make up a set of frequencies, which were coded using amplitude, phase and frequency to create a high-capacity optical signal. Seven spectrally shaped 10-GBd subcarriers spaced at the Nyquist frequency created the superchannel, detected using a high-speed superreceiver. A new signal-processing technique enabled the reception of all the channels without error. The researchers ultimately achieved effective nonlinearity mitigation using multichannel digital backpropagation, combined with an optimized forward error correction implementation to achieve the record gain in transmission reach.
And as the threats of Internet moderation and neutrality increase, the need for open, clean-moving data has never been more important.
“To sustain growth in Internet data, which is crucial to both social and economic development, we must devise new techniques to increase the amount of information that we can send over an optical fiber cable,” Maher said. “If we cannot increase the amount of information that we can send over optical fibers, this will ultimately lead to more aggressive charging models in order to moderate Internet use, which will have a significant impact on the lives of everyday people.”
- fiber optic cable
- A package for an optical fiber or fibers that may include cladding, buffering, strength members and an outer jacket.
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