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Scientists Overcome One of the Biggest Limits In Fiber Optic Networks
Mark.JUK writes: Researchers at the University of California in San Diego have demonstrated a way of boosting transmissions over long distance fiber optic cables and removing crosstalk interference, which would mean no more need for expensive electronic regenerators (repeaters) to keep the signal stable. The result could be faster and cheaper networks, especially on long-distance international subsea cables. The feat was achieved by employing a frequency comb, which acts a bit like a concert conductor; the person responsible for tuning multiple instruments in an orchestra to the same pitch at the beginning of a concert. The comb was used to synchronize the frequency variations of the different streams of optical information (optical carriers) and thus compensate in advance for the crosstalk interference, which could also then be removed.
As a result the team were able to boost the power of their transmission some 20 fold and push data over a "record-breaking" 12,000km (7,400 miles) long fiber optic cable. The data was still intact at the other end and all of this was achieved without using repeaters and by only needing standard amplifiers.
As a result the team were able to boost the power of their transmission some 20 fold and push data over a "record-breaking" 12,000km (7,400 miles) long fiber optic cable. The data was still intact at the other end and all of this was achieved without using repeaters and by only needing standard amplifiers.
Conductor keeps them on the same rhythm. Concert master/mistress is the person in charge of getting everyone in tune.
Interesting article but very light on details. I would love to read the actual paper but looks like it was published in Science. The actual press release here: http://ucsdnews.ucsd.edu/press... has slightly more info than the linked article. This link to the PDF from August 2014 with the theoretical basis is free: http://ieeexplore.ieee.org/sta... It looks like they are boosting WDM signals so this would work with existing long-range infrastructure.
To help understand the scale, the cable length is approximately the diameter of the earth (12742 km).
It is also 25-50% longer than the undersea hop for the longest cable paths (NY to London, LA to Sydney, San Francisco to Tokyo, Sao Palo to Gibraltar, etc.). This has the potential to allow electronics to stay on land, where they are easily maintainable and upgradable and with easy access to electricity.
Interesting development, indeed.
It's crosstalk between wavelengths on the same strand. Read up about CWDM and DWDM.
From PBUK at ISPreview -
"The team have done an impressive experiment, but their press office could do with some wide reading.
Pre-distortion of signals is already used in the fibre systems deployed by BT, Virgin Media, Vodafone, O2, SSE, and many others. The same coherent technology is already doing 22,000km unrepeatered across the Pacific. A 20 fold launch power improvement is only 13dB, which is about 50km.
What is new is processing all the channels together to calculate the pre-distortion. Lovely idea for the lab, but wouldn’t work in practice where channels are deployed one at a time, as each transmitter costs as much as a house (so you don’t deploy them unless you use them)."