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The Internet Media Networking

Terabit-Per-Second Class Connections over FTTH 117

Posted by Zonk
from the makes-for-great-gaming dept.
Big Fat Dave writes "Thanks to research from Japan's Tohoku University, an article at Tech.co.uk wonders if someday the megabit and gigabit classes of net connections will join kilobits in the 'antique tech' bin. By doing some advanced mathematics and 'tweaking' existing network protocols, researchers may be able to enable standard fiber-optic cables to carry data at hundreds of terabits per second. 'At that speed, full movies could be downloaded almost instantaneously in their hundreds. At the heart of the development is a technique already used in some digital TV tuners and wireless data connections called quadrature amplitude modulation (QAM). One glance at the Wikipedia explanation shows that it's no easy science, but the basics of QAM in this scenario require a stable wavelength for data transmission. As the radio spectrum provides this, QAM-based methods work fine for some wireless protocols, however the nature of the optical spectrum means this has not been the case for fibre-optic cables ... until now.'"
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Terabit-Per-Second Class Connections over FTTH

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  • ya but.. (Score:3, Insightful)

    by mastershake_phd (1050150) on Saturday November 17, 2007 @03:28PM (#21391555) Homepage
    At that speed, full movies could be downloaded almost instantaneously in their hundreds

    Not until the PC buses catch up..
    • by ceeam (39911)
      No "PC"s on "backbones" I think.
      • No "PC"s on "backbones" I think.

        True, but the routers and repeaters on the backbone have buses don't they?
        • Re:ya but.. (Score:5, Informative)

          by Ogun (101578) on Saturday November 17, 2007 @03:47PM (#21391721) Homepage
          Fastest backbone router that I know of is the Cisco CRS-1. It can scale to a system capacity of 92 Tbps in total, using 72 42U rack units as one large router. Still, the fastest interfaces on that machine is OC-768 at roughly 40 Gbps.
          • On one fiber?
          • Re:ya but.. (Score:4, Informative)

            by funkboy (71672) on Saturday November 17, 2007 @09:32PM (#21394101) Homepage
            Probably because you haven't seen a Juniper T1600 [juniper.net]. It has 2.5x the per-slot bandwidth of the CRS-1. The Cisco marketing literature may go to 92tbps, but I challenge you to show me a production CRS multishelf system with more than one fabric shelf. Once T1600 modules are available for the TX Matrix the system will provide 6.4tbps in two and a half racks, using far less power than the equivalent real estate worth of CRS hardware (2.4tbps max), at about the same cost. BTW a fully configured 72-rack CRS-1 would require about .8 megawatts of power and belch about 2.5 million BTUs of heat per hour...

            Erm, not that that's a biased viewpoint or anything (heh)...

            Anyway, IMHO far more important to router scalability is the per-slot and per-watt bandwidth, not how many systems you can chain together (as long as you can chain some reasonably useful number, but I don't see a need for more than 8 chassis in a system). The CRS-1 won't be able to handle 100gE without a system-wide fabric upgrade or double-width cards or something. The T1600 (and for that matter, the Foundry NetIron X series, though not in the same class of capabilities or scalability as the Juniper) will be able to slot in 8 100gE linecards the day they're available.
            • by jsiren (886858)

              a fully configured 72-rack CRS-1 would require about .8 megawatts of power and belch about 2.5 million BTUs of heat per hour...
              Or, keeping in the spirit of gratuitous unit conversions, approximately 2^11 calories per forthnight.
        • separate channels (Score:4, Interesting)

          by j1m+5n0w (749199) on Saturday November 17, 2007 @05:34PM (#21392445) Homepage Journal

          True, but the routers and repeaters on the backbone have buses don't they?

          The way a lot of telco hardware gets around the limitation that no computer exists that's fast enough to process the full available throughput, is that the connection is split into hundreds of separate channels, each one on a separate wavelength. A particular router interface need only deal with one channel, not all of them at once. (A single channel might be an OC-192, which runs about 10 gbps.)

          The channels are combined and split apart by a dense wavelength division multiplexer; I don't really know how they work, but if you think of it as an expensive prism you're probably not far off.

          • by anticypher (48312)
            I don't really know how they work

            Then you need a crash course in the state of the art in DWDM technology.

            Start here [ripe.net] {PDF warning!}. You can skip the first part and start at page 23, the first part was covered on slashdot [slashdot.org] before. [Peter, you win the bandwidth DSW for now, I'll reclaim my crown soon]

            There is an accompanying video [ripe.net] {quicktime warning!}. The 4th year university physics course material starts at about 12 minutes in. This is basically a good summary reduced to MTV-generation attention span length.
        • Re: (Score:3, Informative)

          by funkboy (71672)
          > True, but the routers and repeaters on the backbone have buses don't they?

          The 750hp 2.4L V8 engine in an F1 car produces about 3-4x the amount of power of a production car engine of the same displacement, but you don't see even high-end mfrs like Porsche putting that sort of thing in street cars (for reasons I hope I don't need to explain).

          The data plane in high-end routers have custom-designed switch fabrics [wikipedia.org], which technically are not buses and operate in a different (more scalable) fashion. The wiki
      • Re:ya but.. (Score:5, Interesting)

        by gad_zuki! (70830) on Saturday November 17, 2007 @03:40PM (#21391659)
        >No "PC"s on "backbones" I think.

        Then no terabit connection for you. I dont care how fast the backbone is. Where I live the last-mile technology is DSL which for my location maxes out at 1.5mbps.

        I think the "OMG LOOK HOW FAST TIS IS" kiddie-mentality of movies-per-second ignores the whole issue of last-mile distribution. And PC buses. And practility. And economics.

        Youd think slashdot would have better things to post than PR releases.
        • by alx5000 (896642)

          I think the "OMG LOOK HOW FAST TIS IS" kiddie-mentality of movies-per-second ignores the whole issue of last-mile distribution

          Yeah, at least of we got in LoCs per second, we'd be getting somewhere...

        • Re:ya but.. (Score:4, Informative)

          by Kjella (173770) on Saturday November 17, 2007 @05:43PM (#21392531) Homepage
          The practicality and economics is that in all larger construction projects here in Norway today, whether it's apartment blocks or new fields of housing they lay fiber connections. There are approximately two million households and about 150,000 (7,5%) of them can get fiber connections. Each year 30,000 new houses are built and many of them will have fiber connections, though lone houses don't qualify. If we say 25,000 a year (30,000 less lone houses plus retrofits) then over the next decade I expect that to rise to 150,000 + 10*25,000 = 400,000 (20%) for a conservative estimate. Oh yeah and we're considerably more sparsely populated than the US. Fiber has good end-mile economics as long as you're putting down cables anyway. Now, that wouldn't make it useful with a terabit last mile but if you want real capacity and not US "unlimited" capacity, then it's really nice if actually delivering is very cheap. And a few thousand people on gigabit connections add up to terabits quite fast...
        • Seeing as how they can do this on standard fiber optics, this is about as economical as you can get. If all they need to change are the end points, there isn't an issue of re-laying fiber, which is a large portion of the costs involved. If the backbones get a boost in capacity by a factor of 10-100, in theory end line uses should see speed increases as well as it would become much harder to saturate these new backbones. I don't think this would help much for DSL users (because it uses a common broadcast cha
          • The economics of running an online service will also change. As bandwidth costs on the backbones are lowered, it will become more feasable for smaller companies to provide bigger data services. This means things like youtube could easily go high definition, setting up your own audio stream service might actually be really cheap, and personal online storage of gigabytes of data transfers could also be possible and cheap.

            It will be interesting to see the progression of data technologies. Long ago we used fl

        • Re: (Score:3, Interesting)

          by evilviper (135110)

          Where I live the last-mile technology is DSL which for my location maxes out at 1.5mbps.

          So because it won't specifically affect your internet connection, it isn't news?

          I think the "OMG LOOK HOW FAST TIS IS" kiddie-mentality of movies-per-second ignores the whole issue of last-mile distribution.

          FTTH is last-mile distribution.
        • by funkboy (71672)
          > Youd think slashdot would have better things to post than PR releases.

          Depends on one's definition of "you"...
        • by jamar0303 (896820)
          1.5M? My god. America needs a telecom overhaul. This came from Japan, land of 100M residential fiber connections.
          • "America needs a telecom overhaul. This came from Japan, land of 100M residential fiber connections."

            If america had an overhaul imagine how many people would start pirating movies and games!!! i mean it took (um) my friend 16 hours to download a 6GB game over the weekend, imagine if every home had a 100MB upspeed instead of 40k? it would have taken minutes..

            Is piracy a problem in japan?
            • by jamar0303 (896820)
              No. But then again, Japanese CDs use DRM that is far less invasive- you can actually do stuff with it, and for me, it was trivial to work around for other uses. And for the true "pirates" JASRAC is far more rabid than their American counterpart the RIAA.
    • by ms1234 (211056)
      And since all the data flows through Microsoft in the future you will still have to wait a few hours :)
  • We'll barely be up to 100 Mbit when the rest of the world hits terabit. The media conglomerates that own the rights to provide internet service to your home will make sure of that.

    • by lattyware (934246)
      Yeah, so here in the UK, We'll be getting 24MB by then! London might be getting 50MB even...
      • You're talking rubbish. ADSL+ was being sold to UK subscribers over two years ago. I don't see why anyone should be blamed for the fact that where you live isn't populated enough to be deemed profitable yet. ISPs are not charities.

        http://www.pcpro.co.uk/news/77057/uk-online-joins-24mbps-adsl-rollout.html [pcpro.co.uk]
        • by lattyware (934246)
          Yes, you can get that, but only in Central London and Manchester. I wasn't blaming anyone, in fact, your little rant there was pointless. I was simply saying, the general UK might get faster speeds at such a time as everywhere else gets even faster speeds. I never said we should get it, I said we might, implying I'd want that.
          • My point was, no, it's not just Central London and Manchester. Two years ago, yes - but not now. You're suggesting that the trials failed and LLU has ceased - or that ISPs have done absolutely nothing in that time?

            I live in Kent and 24 Mbps is most definitely available - but I have 20 Mbps from Virgin.
            • Re: (Score:2, Insightful)

              by lattyware (934246)
              Your 20mbps is from Virgin. Who do cable. In a lot of, nigh most, areas you cannot get cable, and most areas do not have lines that can handle high speed connections. My point was that most areas will not get those kind of speeds, that is true. I did not suggest it was ceased. I suggested that not everyone is going to get those speeds for quite some time.
              • by vidarh (309115)
                You stated "Yes, you can get that, but only in Central London and Manchester," which isn't remotely true.
                • by holysin (549880)
                  "which isn't remotely true." Define remotely?

                  I have to side with Latty. It's really not far off, if you're not in London/Manchester it's a potluck to get fast service I'm currently living in the 10th largest city in England (as of 2004 estimates) in a newly built (2002ish) building, pretty much on top of two different university campuses, within easy walking distance to the town centre, and what are my options? Adsl. Nothing else (outside of dialup). There is some cable in the city, but not much. It's
    • Re: (Score:3, Insightful)

      by ScrewMaster (602015)
      The media companies (well, the motion picture companies) will do everything in their power to prevent it. All they have to do is have Congress or the FCC keep the telcos in power and we'll never see anything more than we have now. The very last thing they want is for it to be as quick to download movies as it currently is to download music.
    • What's the big deal about this? Verizon FIOS ads (fiber to the premises) have been advertizing "true quam" for their fiber connections for over a year. The idea that this is new and exciting technology is hogwash, it's been used in delivery of data to the end consumer for several years at least, I have friends who have had it installed at their homes for at least that long.

      Knowing that it's old tech takes the gee whiz factor out of it.
  • I bet... (Score:5, Funny)

    by ceeam (39911) on Saturday November 17, 2007 @03:31PM (#21391579)
    ...someone in MPAA just shat himself.
    • the vision (Score:5, Interesting)

      by Tumbleweed (3706) * on Saturday November 17, 2007 @03:51PM (#21391749)
      Actually, this opens up some interesting possibilities for people like the RIAA and MPAA. When you can download a whole CD or DVD in seconds, there's no longer much point to someone who's system is connected, in having physical media, or even a copy of the media, on their own machine. Whatever type of business model they'd wind up with could take that into account, and they could come up with a Netflix-type model, or something new and appropriate to the new reality (when have they ever done THAT, though?) - pay $x/mo, or $x/mo/bitrate/resolution, or whatever. The online rental business could be huge.

      There's also the benefit of being able to do real-time offsite storage. The people who would care about needing massive amount of storage for their movie collection - no longer need to store their movies locally. Your whole machine could wind up being nothing more than an online access point with it being customized to be the HCI that you prefer: curvy keyboard (w/ or w/o lights) or not, big-ass widescreen display ... or not, your choice of colour, and a big honkin' net connection. Lots of RAM and a SSD boot drive, and something (magnetic card, keyfob, whatever, or nothing - just swipe your retina across a scanner or something) you can take with you to plug into whatever other machines you use to let that machine know it's you and to configure to your preferences. And nothing more. No moving parts other than the keyswitches and GP/CPU fan.

      This is the kind of technology advancement that can change almost everything in its field if enough people with vision can take advantage of it and work together to make it seamless.
      • Re: (Score:1, Insightful)

        by Anonymous Coward
        Once you have everyone storing Gigs of data elsewhere then you've exponentially increased your bandwidth usage and you are back to having an effective download rate in the Mbps as opposed to Tbps.

      • by sxeraverx (962068)
        You really don't want to be swiping your retina across anything. Ever. It would hurt. You'd go blind. And you wouldn't even get any useful information out of it. It's the pattern of nerves behind your retina that a retinal scanner scans, AFAIR.
    • Re: (Score:3, Insightful)

      by vivaoporto (1064484)
      Not really. My cable TV provider (that is not a MPAA member, but certainly buy a lot of content from them) would love such technology in order to serve digital Video on Demand faster, less compressed and to more people at the same time. As other people observed, such a fiber would be next to useless to current home user technology (other components would become the bottleneck), but to content provider, it would be miraculous.
  • duh, what will it be used for? pr0n.
    • by ceeam (39911)
      Web-apps, terminals... Universal streaming of TV, radio, phone, etc signals over IP. You're like an IBM rep in the 50s about 5 computers being top for the world.
      • No he's not. He's being perfectly realistic. Porno consumes a significant chunk of global bandwidth today, and that will only increase as transfer speeds increase. What it will mean is that now I can get my skin flicks streamed in widescreen hi-def, rather than a small 5x6" window on my desktop.

        I don't have a problem with that.
  • Finally (Score:3, Funny)

    by djupedal (584558) on Saturday November 17, 2007 @03:37PM (#21391627)
    I can have my own copy of the Library o' Congress and let them worry about backup :)
  • every time connection speeds have increased (300 Baud, 1200, 56k, .... 20Mbps) you've needed more disk space to store the cr... you download. At Tbit speeds, where will you put all this?

    Similarly, once you spent a few seconds downloading everything off the internet, what will you do next?

    (3 seconds to download it, 25 years to read it all)

    • by hjf (703092)
      maybe this will make the Network Computer dream a reality? Imagine that you have an internet connection that's faster than any drive array you can make. Then add Web 3.0 apps to it. No more formatting, upgrading, antivirus, whatever. Maybe for us geeks that would be too much, but for Common People, that would be practical. Pay-per-use computing. It would be a service just like cable TV.
    • "once you spent a few seconds downloading everything off the internet, what will you do next?"

      Make more stuff.

    • by Kegetys (659066)
      > At Tbit speeds, where will you put all this?

      in /dev/null
  • LANs (Score:2, Insightful)

    by Sarten-X (1102295)
    This won't be as useful for Internet use (as mentioned above, the last link will continue to suck), but for businesses and other LANs with high demand (data centers, anyone?), this will be a big help.
    • by neomunk (913773)
      I didn't RTFA yet (it IS open in a tab though), but the title of the article would imply that we ARE talking about the last link. I'm pretty sure FTTH means 'Fiber To The Home'.
  • I'm not sure if this is the case still, but a networks teacher of mine told me some years ago that the bottleneck of the internet were the routers.
    • So you need 8 Mbit or so superjumbograms. In principle, not a problem, though some header fields need to be widened. The issue becomes one of memory bandwidth, instead: that's a fearsome hose, by today's standards.
    • by funkboy (71672)
      Actually, in the US the bottleneck is carrier monopolies and their influence on politicians (more at the local level than anywhere else).
  • I get something like 70 NTSC channels and everything above oh 400 Mhz on my cable system is QAM 256. I believe the cable company trucks the signal over fiber (QAM and all) to a local node where it is converted to RF and split into the house..

    How is this new or different?
    • by Myria (562655) on Saturday November 17, 2007 @03:55PM (#21391773)
      Just wait until someone with one of these gets Trojaned and the controller starts DoS-extorting Google.
      • by neomunk (913773)

        Just wait until someone with one of these gets Trojaned and the controller starts DoS-extorting Google.

        Yeah, that's the first thing I thought of too, well not Google, but close. Something like the combination of this story and http://it.slashdot.org/article.pl?sid=07/09/07/122200 [slashdot.org]

        Heh... Storm, SkyNet, what's the difference? :-D

        Oh, and since I'm posting, and I haven't seen it yet, I might as well ask if anyone has thought of a beowulf cluster implementing these things?

    • The story is about doing it over fiber optics -- using an optical signal instead of an electrical one.

      It seems like something that might be useful 20 years from now.
    • by Bigjeff5 (1143585)
      No, it's not the same because the cable company isn't don't QAM over Fiber, they're doing over... wait for it... CABLE. They may be moving the data around over fiber before it gets to your house, but that fiber optic connection is the fiber equivalent (in terms of modulation techniques) of the old 1 megabit co-ax. In fact, QAM is what allows that crappy co-ax connection that the cable company STILL uses to push video and internet up into the 10 - 20 megabit range.

      Apply that same tech to fiber, guess what?
  • We need faster hard drives to catch up
    • Its the year of Solid State Disk on the desktop.
    • Or lots of really cheap disks. There's already RAID which takes multiple disks and combines them to improve performance and redundancy. There's also ZFS which does the same thing but in software, and it makes managing large sets of disks simpler. At a larger scale you can start exploiting P2P methods where every peer contributes a small amount but when you put together the pieces it adds up big time.

  • QAM (Score:2, Insightful)

    by b1ffster (628989)
    Quadrature amplitude modulation (QAM) is frequency based. It's 4 way (hence the 'quadrature thing) They're been doing way more than QAM in the last decade, they're doing 64-way amplitude modulation, with frequency spectrums (cable) for ages How the fuck are they using multi-frequency modulation techniques on light rays (fibre) ? This is either crap, very good or deserves a Nobel prize! Is this an early April 1st ??
    • by j1m+5n0w (749199)

      How the fuck are they using multi-frequency modulation techniques on light rays (fibre) ? This is either crap, very good or deserves a Nobel prize! Is this an early April 1st ??
      Light is just another medium for transmitting a signal, why should it be any different? The only reason I can think of why they might not have done this earlier is that it's hard to do elaborate signal processing at the speeds they want to use.
    • by niceone (992278) *
      Quadrature amplitude modulation (QAM) is frequency based. It's 4 way (hence the 'quadrature thing)

      No, the quadrature thing refers to the two carriers being 1/4 of a wavelength out of phase. You can have any number of different symbols and it is still QAM: http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation [wikipedia.org].

      I'm not quite sure what the break though here is, and TFA isn't that clear, but I Wouldn't write it off.
    • Re: (Score:2, Interesting)

      by Wierdy1024 (902573)
      I call foul, While technically possible to get the 1/4 phase difference to do QAM from very stable lasers, with two optical paths very slightly different lengths, and amplitude modulation of both, transmission of such a signal over long distances is going to be impossible. QAM suffers very badly from multipath, where different parts of the signal travel different distances. In the case of light, if the route the light takes varies more than ~100nm, the signal will be unrecoverable. Also, the laser must
    • by Crypto Gnome (651401) on Saturday November 17, 2007 @07:17PM (#21393239) Homepage Journal

      They're been doing way more than QAM in the last decade, they're doing 64-way amplitude modulation, with frequency spectrums (cable) for ages How the fuck are they using multi-frequency modulation techniques on light rays (fibre) ?

      Are you aware that "radio waves" and "light rays" are fundamentally the same thing [wikipedia.org]?

      <Massive generalization> anything we have worked out how to do "with radio" is something that there is no fundamentally intrinsic reason why we should not (one day) be able to work out how to do "with light"</Massive Generalization> (and don't bother saying things like passing 'radio" through a sheet of cardboard which obviously blocks "light" - I'm talking about *uses* ie modulation/signalling techniques, not "modifying the laws of physics" issues)

      Or do you think that a 1kHz audio wave is in some *magic* way fundamentally and intrinsically different from a 5kHz audio wave? or a 25kHz wave?
      • What is an audio wave? You mean sound wave, which is a compression wave, which is nothing to do with em.
        • (sigh) WHY do I need to explain EVERYTHING? ..... an "audio wave" is the same moronically stupid term as "radio wave", and I was using the term in an example - if we (collectively, the human race) are capable of understanding that "sound waves" at 1kHz are not fundamentally different to "sound waves" at 5kHz then FOR $RANDOM_DEITYs SAKE WHY do we mystically believe that two waves in the electromagnetic spectrum are *fundamentally* different purely because one is higher frequency than the other.
    • by Ruie (30480)

      How the fuck are they using multi-frequency modulation techniques on light rays (fibre) ?

      The frequency of light is of the order of 100000 THz. So the frequencies they are interested in are much smaller and usually limited by dimensions of modulating devices and limits of electronics they use.

      A simple setup could be this: a frequency stabilized laser serving as local oscillator followed by two electro-optic crystals offset by a distance that corresponds to needed phase delay. If your electronics and crys

  • Whoa (Score:3, Funny)

    by NIckGorton (974753) on Saturday November 17, 2007 @04:10PM (#21391873)
    If its "Terabit-Per-Second Class Connection" I wonder what a first class connection gets you.
    • by TubeSteak (669689)

      If its "Terabit-Per-Second Class Connection" I wonder what a first class connection gets you.
      It'll get you champagne and steak all the way to Brazil.
      (I know there's a brazillion joke in there somewhere)
    • If its "Terabit-Per-Second Class Connection" I wonder what a first class connection gets you.

      A premium email account with Yahoo! with an extra 2GB storage, free anti-virus, and a Flickr account? I'd bet Premium(TM) First Class Connection subscribers get a fixed IP address.
  • Just watch, first person to get one of these connections will be the head researcher's mother. [slashdot.org]
  • If you step over the top sekrit 10TB monthly limit the provider will cut you off and send over the company dog to scoot its anus across your new carpet.

  • To get a TB/s - 10 Terabits/s (1/10th or less of what they claim) implies you have gates that operate at better than 0.1 pico-second reflex times (that is, off-on-off). I am only talking the receive buffer. I can see what you could do with all the new cores now - make them into a parallel IO where each takes a time slice of a microsecond or so, that is, a megabyte of data, oh wait, we can't do cache writes that fast currently. Looking at the article and tech I see a bunch of lambda's and a lot of parallel
  • Disturbance (Score:3, Funny)

    by FridayBob (619244) on Saturday November 17, 2007 @05:42PM (#21392521) Homepage

    At that speed, full movies could be downloaded almost instantaneously in their hundreds.
    At Slashdot, readers sensed a great disturbance in the Force, as if millions of movie studio and record company executives cried out in terror and were suddenly silenced.
  • an article at Tech.co.uk wonders if someday the megabit and gigabit classes of net connections will join kilobits in the 'antique tech' bin.

    I can remember when kilobit/sec connections were something to look forward to. I traveled three years (early '80s) with an acoustic coupler that could often communicate back to the office only at 300 baud (and periodically error out at that speed). Usually, I wanted to use 3270 emulation over the connection. This is like watching paint dry only more boring. It did hav

  • Neither this article, nor anything linked from it and accessible without subscription, describes the result in any useful detail.

    What is routinely done today in hybrid fiber/coaxial cable (HFC) cable TV systems, is to use linear RF-band, often 50-750MHz in 6MHz (North American standard) bands corresponding to television channels. Both 64- (6 bits/baud) and 256- (8 bits/baud) QAM modulation standards are used. 64-QAM has been around since maybe 1996.

    256-QAM requires a better signal/noise ratio through

  • Sorry but as long as I cannot access the actual article I have to assume is fake.
    This is science: convince the world!
    So putting your actual paper behind some login is a no-no.
  • by Tom Womack (8005) <tom@womack.net> on Saturday November 17, 2007 @08:39PM (#21393809) Homepage
    It looks as if

    http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=4348615&isnumber=4348298 [ieee.org]

    is something like the work being reported on; 'A 1 Gsymbol/s, 64 QAM coherent signal was successfully transmitted over 150 km using heterodyne detection with a frequency-stabilized fiber laser and an optical phase-locked-loop technique. The spectral efficiency reached as high as 3 bit/s/Hz.'

    Masato YOSHIDA's list of papers at

    http://db.tohoku.ac.jp/whois/Tunv_Title_All.php?&user_num=LTU0OA==&sel1=1&sel2=1&sel3=1&sel4=2&page=1&lang=E [tohoku.ac.jp]

    looks very plausible in the context of this work; 'coherent optical transmission' is I think the relevant buzz-word. Going from 1Gsymbol/s to 10Tsymbol/s is clearly a lot more work, but being able to do optical QAM at all is pretty spectacular.
    • Additional searching unearthed the following:

      http://www.jstage.jst.go.jp/article/elex/4/3/77/_pdf [jst.go.jp]

      This is not exactly the work referenced in the original article, but it is very likely related to it. Anything that requires a cell of isotopically weird (carbon 13) acetylene sounds fun to me.

      The crucial element appears to be a highly stabilized laser that is used in the receiver as a local oscillator to recover (by optical heterodyne detection) a UHF RF carrier that carries the actual QAM.

      I had read s

  • http://mobile.slashdot.org/article.pl?sid=07/11/16/1326214 [slashdot.org]

    I am not savvy about this stuff. Could this be the "stable wavelength" referenced in the article?
  • Of course those bitrates are theoretically possible with optical fibers. After all you could apply the advanced modulation schemes of DSL to them, theoretically.
    Actually right now for short distances the dispersion might be small enought to actually do QAM, but I don't believe it's feasible on longer lines.

    Of course once we get ways to use lightways in the same way as radio waves it all would be simple, but right now, even the best lasers still actually produce band-limited noise with a bandwidth of a few h
  • At this moment I don't think home users would benefit from a connection faster than 1 Gbps.
    I have a gigabit connection at home and I can download a DVD in less than 1 minute and it's not even getting close to reaching the limit of my connection. The hard-disk is getting overloaded at about 20MB/s in BitTorrent.

    You can watch streaming BluRay DVDs with a gigabit connection so unless we come up with some way of producing a lot more data for entertainment purposes, the terabits-per-second connections will be ov
  • Point 1: We have been using QAM in 56k modems for years. Point 2: There will have to be alot of infrastructre work done before we get the required singlemode fiber to my house. It won't hang from a power pole, every slight bounce and swing of that cable will induce phase noise (bad news for QAM). Buried cable will just love earthquakes!
  • by maz2331 (1104901)
    OMFG that is a lot of p0rn.
  • Once backbones get upgraded, we will see a sub-second slashdot effect.

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