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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.
I thought the conductor just waved a baton in some strange patterns and got paid handsomely for that. He is so ashamed for getting paid so much for doing so little he does not dare show his face to the audience, and turns his back to them. Never knew it was his job to tune all the instruments of the entire orchestra before the concert.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
Yes, but with this new technology their costs will be lower and so they'll be able to get more profits.
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not faster. Why? Comcast/TimeWarner et al want slower speeds so they can charge more for high speeds....
Wouldn't matter this is a backend/longhaul improvement. They can still charge you more for less.
So the problem is cross contamination between fiber channels due to frequency differentials, I think they equalized all frequencies somehow but I don't fully get it. Red is longer than blue for example and if separate strands of fiber carry different 'colour' and frequencies 'bleed' from strand to strand how do you equalize that exactly? Have wave peaks correspond? How? Are they proportionate to remain synchronized? If this is a serious problem, why not add more isolation between strands?
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Since the diameter of the earth is 7 926.3352 miles, this could conceivably remove any need for repeaters. I still bet it will not improve fiber rollout by big telcos in the U.S.
Literally, an autoplaying Dove shampoo commercial on Slashdot. Starts playing 10 minutes after the site loads when the tab has even been in focus for about that time. Fucking pathetic times for this website
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.
Back hoes. ;)
Since the diameter of the earth is 7 926.3352 miles, this could conceivably remove any need for repeaters.
I got the impression from the (sketchy) article that repeater AMPLIFIERS were still needed but repeater REGENERATORS were not.
I.e. you still needed to boost the strength of the signal to make up for the losses. But the progressive degradation of the quality of the signal - with data from different frequency bands bleeding into other bands (especially in the amplifiers themselves) due to nonlinear "mixing" processes - had been headed off, by synchronizing the frequencies of all the carriers to exact multiples of a common basic difference-between-the-carriers frequency.
This apparently sets up a situation where the distortion products of each carrier's interaction with nonlinear processes cancel out with respect to trying to recover the signals on another carrier - much the way the modulation products do in OFDM modulation schemes. In OFDM it allows you to make essentially total use of the bandwidth. In this system it lets you use simple, cheap, amplifiers to get your signal boost, rather than ending the fibre before things get too intertwingled, demodulating all the signals back to data streams and recovered clocking, then generating a fresh set of modulated light streams for the next hop - MUCH more expensive and power hungry.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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.
I got the impression from the (sketchy) article that repeater AMPLIFIERS were still needed but repeater REGENERATORS were not.
Then again - another part of the article makes it look like an additional result was that they could boost this less-subject-to-degradation-by-nonlinear-distortions signal at the start until the fibre itself was acting non-linearly, in order to get a signal strong enough to survive a much longer hop.
So it's not clear to me whether the distance was achieved by:
- long hops enabled by strong signals, and NO amplifiers
- longer propagation without regenaration using JUST amplifers
- a combination of the two: Both getting long total length without regeneration AND being able to use stronger signals and thus use larger space between the amplifier-type repeaters.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
My understanding that the transmissions over modern fibers use all sorts of tricks to pack more information into it, including frequency modulation, multiple polarization states, etc. I wonder how this new frequency comb technique plays with those.
Crosstalk? It's optical. make the casing out of an opaque material. I didn't think EM radiation and radio waves, etc can create new photons inside of a plastic material. What crosstalk are they talking about?
I guess no one bothered to RTFA and delve deeper. Looks like the Kerr effect is the non-linearity of the refractive index; i.e. the refractive index changes with power, so that limits the light intensity they can shoot down the fiber. Looks like this development is a form of predistortion, most likely to aligning the phase of the carriers/channels to limit the crest factor (instantaneous total amplitude of combined channels) to minimize the kerr effect. We do this in the RF comms industry, but doing it optically is probably very tricky.
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)."
Because of the monopolistic stranglehold that companies such as Comcast and Verizon hold over the last mile, American consumers won't see a dime of any cost savings from this.
Meanwhile consumers in Europe and Asia will continue to see faster cheaper broadband.
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No information on bandwidth, signal strength, channel separation or anything else. Only that it "acts like a concert conductor".
How low can a scientific article sink, and still be the basis for a slashdot story? This must be a new low.
Current trans oceanic fibers do transmit multiple colors at high speed with amplifiers on the seabed and no regenerators. New installations carry 64 Tb/s per fiber. and often 64 fibers are laid. Some are left dark, but theoretical capacity for a cable is therefore 8192 TB/s bidirectional capacity
This might be up to 8 billion HD channels or everyone the entire earth watching different TV channels at the same time. Not sure how much more bandwidth is needed in a cable.
don't cut it off www.mgmbill.org
I thought dispersion was a greater problem than cross-talk.
Well, to be more specific the conductor facilitates a single interpretation in the change of pulse and other variables open to interpretation. A good orchestra can easily keep a steady pulse and play together rhythmically without a conductor just fine. They can even start together blindfolded, this is about listening to each other, esp breathing, it is actually not as hard as you might think. A very good orchestra can even come to a good consensus as to musical interpretation without a conductor, but will generally come together much faster with a good conductor. A very good orchestra will completely ignore a bad conductor during a performance and sound better for it.
School orchestras and the like will have conductors perform a more "keep everyone together rhythmically" type function, but this is not the ideal situation. More of an aid to learning situation.
I assume less electronics in-cable would result in more harbor 'accidents' for the NSA repair crews to 'fix'.
Doesn't matter, fiber isn't pushed out anywhere anymore.