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New Laser Data Transfer Rate Record Set At 26 Tbps

Posted by Roblimo on from the squeezing-gallons-of-data-through-a-straw dept.

MasterPatricko writes "Scientists at the Karlsruhe Institute of Technology (KIT), Germany have published a technique to push optical data transfer rates to new levels. The article says, 'The trick is to use what is known as a "fast Fourier transform" to unpick more than 300 separate colours of light in a laser beam, each encoded with its own string of information.'"

17 of 127 comments (clear)

  1. Makes Sense... by WarpedCore · · Score: 3, Insightful

    So that one episode in Voyager where Seven of Nine makes a "Fourier Analysis" wasn't total bullshit?

    1. Re:Makes Sense... by Anonymous Coward · · Score: 3, Informative

      So that one episode in Voyager where Seven of Nine makes a "Fourier Analysis" wasn't total bullshit?

      No, we've been doing Fourier analysis for decades. Fourier himself invented it in the 19th century.

      Regarding the technique, it sounds like an optical-computing implementation of OFDM (orthogonal frequency division multiplexing), which is a core technology for ADSL and many other communications protocols. Electronic and radio OFDM is limited by peaking factor (the ratio of peak level to RMS level); doing this optically may get around this problem.

    2. Re:Makes Sense... by blair1q · · Score: 2

      The word you are looking for is "WHOOSH!".

      HTH

    3. Re:Makes Sense... by pclminion · · Score: 2

      Saying they used Fourier transforms is a "no shit" sort of statement. It's like saying you used a shovel when you dug a hole. You'd have to go out of your way NOT to use some aspect of Fourier theory in this problem space. By "used an FFT" they probably mean they're doing some form of OFDM modulation.

    4. Re:Makes Sense... by dogmatixpsych · · Score: 2

      We do the same thing with MRI scans to reduce scan times, varying the extent of the transform to alternate between speed and quality.

  2. I was going to make a "Library of Congress" joke.. by Anonymous Coward · · Score: 2, Informative
    But the FIRST line in the article was:

    At those speeds, the entire Library of Congress collections could be sent down an optical fibre in 10 seconds.

    Well played, BBC. Well played, indeed...

  3. Re:*Facepalm* by swanzilla · · Score: 3, Funny

    I'm not certain...British humor is puzzling.

    --
    0 = 1 + e^(Alt something)
  4. Re:I was going to make a "Library of Congress" jok by _0xd0ad · · Score: 2

    The best part is they were off by a factor of 8, since Tbps means terabits per second. Not so well played after all...

  5. Re:Thank goodness by _0xd0ad · · Score: 2

    http://www.loc.gov/webarchiving/faq.html#5

    As of April 2011, the Library has collected about 235 terabytes of data (one terabyte = 1,024 gigabytes). The archives grow at a rate of about 5 terabytes a month.

  6. Re:Colors by vlm · · Score: 2

    Serious question: It seems like it could be possible to use an infinite number of colors with interpolated laster on pulse modulation to transmit an infinite amount of information. Why won't this work?

    According to the Shannons theory it'll work just fine assuming you have infinite transmitter power with zero receiver noise so as to get that infinite SNR it would require.

    On the other hand, dispersion thru any media, optical fiber, even air, will totally screw it up at an infinitely short distance. Basically you will not be surprised to know that light travels at different speeds in glass or whatever depending on its frequency... that is pretty much how a prism makes a rainbow... So your 1500 nm bitstream will rapidly cover an area of 1499.(lots a 9s) to 15.(lots of 0s)1.

    The other problem is you'd like to think single mode fiber Really Means single mode, but theres dispersion there too. I suppose if you had an infinitely small point source for the transmitter, and the fiber were perfectly straight...

    http://en.wikipedia.org/wiki/Group_delay_and_phase_delay

    --
    "Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
  7. Re:Colors by pclminion · · Score: 2

    Serious question: It seems like it could be possible to use an infinite number of colors with interpolated laster on pulse modulation to transmit an infinite amount of information. Why won't this work?

    The uncertainty principle, basically. In the real world, there's no such thing as light of a single frequency. This is due to some basic properties of Fourier transforms. All real light pulses are finite in duration, which means they contain a range of frequencies, not a single frequency. The only way to achieve light of a single precise frequency is for the pulse to be infinite in duration. That's not physically possible.

  8. Re:Who whole damn library? by blair1q · · Score: 2

    As this is a fairly large tube, they should all fit just fine, especially if the go in brain-first.

  9. Link to the original by Simon80 · · Score: 2

    http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2011.74.html According to the abstract, the key contribution is an optical implementation of the Fast Fourier Transform (which is pretty cool). They only tested their work using fibre, not just laser beams or w/e is implied by the headline.

  10. Ok... let me try and translate by i_b_don · · Score: 2

    I work in this field so let me see what I can do to translate what's happening and which parts are actually interesting. I dont' know the details of the experiment I'm only going off the article's summary and assuming they're correct. (BTW, while I"m an expert in a tiny slice of this field, my "expert" level knowledge doesn't extend to the whole pie. So some things I say may be assumptions I've made and can be wrong. If you see a mis-statement please correct me.)

    First off, we do fiber optics all day long for internet backbone communications. We even do "multi-mode" optical (different color/wavelength lasers) all day long but only for short cable lengths. Neither of which is article worthy. This thing called a "fast Fourier transform" is just math that is taught in school and is nothing even close to revolutionary, it is simply a fundamental mathematical tool of everything in this field.

    First off let me give you the basic framework. When you're talking about sending data at these speeds and over these lengths, you can forget the idea that you're sending lots of data down the line in nice waveforms. The data is so distorted that significant energy is put into compensating and un-distorting the waveforms. Fiber optics at these speeds just doesn't work at all without heavy duty data recovery techniques. So we send down the line data, get back garbled gibberish, apply techniques for removing errors and you can recover your data stream.

    So typically when we do "long haul" fiber (> 1k or so) we do single mode fiber, this means a single frequency or color (remember your physics, each color is a different frequency of light). This is because different frequencies of light travel at very slightly different speeds down the fiber and if you have long enough fiber this difference in speeds becomes significant and starts to harm your ability to regenerate the information. Additionally one frequency can cause noise in another frequency band so keeping things to a single frequency makes things more stable at long haul lengths. This is why "traditional methods to separate the different colours will not work".

    So Professor Freude and the article:
    There are two steps forward here:

    1. He's using a single laser to create different frequencies of light. I don't know if this is a common technique or not. I've typically hear of different colors of light being generated by different lasers but I am not an optics guy so I'm not sure.

    2. He's using an optical method in place of a Fast Fourier Transform (FFT) instead of silicon that somehow helps him decode the data. An FFT mathematically converts from frequency domain to time domain so maybe he's just using a prism or something to separate the different frequencies as a pre-processor step and then pumping this into his processor, but I can't tell.

    So Professor Freude and team and working on making "multi-mode" work at long haul. This is typically not done today so that's the step forward and since you can pack more information into your data stream if you include multiple frequencies, that's a nice win. but of course research success does not necessarily equal a marketable product.

    (Again, I am not a guru here, so if you are, please politely correct any mis-statements I've made.)

    d

    --
    all language nazi's will burne in heil!
    1. Re:Ok... let me try and translate by Soft · · Score: 4, Informative

      We even do "multi-mode" optical (different color/wavelength lasers) all day long but only for short cable lengths.

      I'm afraid you're mixing up frequency/wavelength modes with propagation modes. Most long-distance systems use several different wavelengths, that's what WDM is. But they use single-mode fibers, meaning that light at a given optical frequency (and polarization) can only propagate in a single way, thus at a given speed. Multi-mode fibers, with a wider core, let light propagate over different modes (different possible paths in the core for light rays, kind of), which plays havoc with the signal (pulses get echoes and whatnot), which is why they are used only for short distances.

      The experiment described here uses OFDM, which in principle is akin to WDM but squeezing many wavelengths as close together as theoretically possible, too close to be separated by classical optical filters. Instead, you can separate them mathematically using an FFT, but that takes a lot of computing power. What the authors did is to implement FFT optically, which is very neat. It enables the use of OFDM at ultrahigh bit rates; and the details of OFDM are such that, used in the right way, it can be extremely resistant to signal degradation (look e.g. at Figure 4(c) in the Nature Photonics article, and think about how tightly a conventional system at that bit rate would have to manage dispersion).

      What bugs me is that they describe their setup as performing better than plain coherent detection (Figure 5), which I have a hard time believing. Exactly how did they do the comparison, I wonder.

  11. Re:Colors by peragrin · · Score: 2

    Not being a hardware geek, this is what I heard: Is it possible to recalibrate the phased tetryon emitters to modulate the warp field and provide infinite information?

    No, because subspace interference would cause a tachyonic wave which would open a temporary worm hole which then would suck the information into a parallel universe.

    ah so that is where Hawking radiation comes from. Parallel universes trying to send porn quickly.

    --
    i thought once I was found, but it was only a dream.
  12. How about summarizing the ACTUAL NEWS instead??? by Co0Ps · · Score: 2

    Wow, the summary is completely misleading and tells you nothing about the actual news. It reads like they just figured out that they can use multiple frequencies to send additional bands of data. Everybody with a slightest clue about how optical data transmission works knows this already. The news in TFA however is that they have figured out how to encode this data with a single laser instead of one laser per band making it enormously more economic. A car analogy would be if someone had figured out how to make cars fly without wings, and the summary would be "a new vehicle pushes transportation to its limits. by sitting in a container with an engine one can travel much faster than walking." Facepalm.