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Scientists Double Optical Fiber Transmission Capacity 229

Posted by timothy
from the Polarisationsmultiplex-Datenübertragungssystem dept.
ms writes: "Yesterday golem.de reported that the Optical Communication and High-Frequency Engineering Group at the University of Paderborn (Germany) claims to have made a technology practical which doubles the transmission capacity of optical fibers to 80 GBit/s. In their so-called "polarization division multiplex data transmission system" they don't only send one but two mutually orthogonal light waves through the fiber. They say the only big problem was the dispersal of the light waves which limits the data rate. Additional they had to fight against the phenomena that the polarization direction of the light waves changes while it goes through the fiber. Now, after two years of research, they invented an "automatic optical compensator of polarization mode dispersion" which fights both the limitations. With this gadget they were able to send data at a rate of twice 40 GBit/s (that's 85,899,345,920 Bps) over a test-line of 212 km. And "only the available equipment limited distance and data rate". As we all know, optical fibers build the (cronically overloaded) backbone of our beloved Net. (BTW: That's Net., not .Net!)" Here's the babelfish translation, too.
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Scientists Double Optical Fiber Transmission Capacity

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  • Any chance I can get a hookup into this? :-) I wouldnt mind downloading directly off that fiber line..

    Moderation: Humor=+1 Underrated=+1 Insightful=+1
  • Mind Blown (Score:3, Interesting)

    by Zen Mastuh (456254) on Tuesday October 09, 2001 @05:07PM (#2408119)

    Just trying to grok "mutually orthogonal". Is that redundant, or just over my head? Not trying to nitpick, but to understand something my networking prof never explained.

    • I'm not certain but I think it's just muddy syntax - I assume they just mean perpendicular. Orthoganl in this context I would assume means at right angles, and implies the mutually part - so yeah, sort of redundant or just badly stated.
    • In geometry, orthogonal just means perpendicular. But, according to searchStorage: "In computer terminology, something - such as a programming language or a data object - is orthogonal if it can be used without consideration as to how its use will affect something else. " So, the light waves are mutually orthogonal (they are data objects in this case), but I'm not exactly sure how to apply the definition to exactly what the scientists are doing with fiber optic cables.

      F-bacher
    • Orthogonal is a math term, not a networking term.

      In 2 dimensional space it's the same as perpendicular, but in 3 dimensions "perpendicular" is technically insufficient to describe the relationship. As you add dimensions orthogonality gets progressively more complicated, hence the addition of "mutually". It could be redundant depending on the situation, but better safe than sorry...

    • mutually orthogonal (Score:5, Informative)

      by MarkusQ (450076) on Tuesday October 09, 2001 @05:28PM (#2408257) Journal
      Just trying to grok "mutually orthogonal". Is that redundant, or just over my head? Not trying to nitpick, but to understand something my networking prof never explained.

      "mutually orthogonal" means (for a set of two or more elements) that each pair of elements is orthogonal--AFAIK, it's a synonym for "pairwise orthogonal". "orthogonal," of course, has lots of synonyms, including "linear independence," "at right angles," "having zero dot-product," "statistically uncorrelated," etc.

      So, the three spacial dimensions, the set {phase of the moon, day of the week, time of day}, etc. are all "mutually orthogonal." When talking about a set of only two elements, the "mutually" is superfluous, but not redundant.

      -- MarkusQ

      • "orthogonal" implies in more than one element, so the "mutual" is redundant. If A is orthogonal to B, then B is, necessarily, orthogonal to A.
    • Orthogonal can either mean that the two don't affect each other, or that they are at right angles to each other. In this case, it means both - the angle of polarization of one beam of light is orthogonal to the angle of polarization of the other, and thus a polarization filter parallel to one beam of light passes it through unhindered and completely blocks the other beam. In this way you can process the two beams separately even though they are running down the same fiber.

      But, yeah, mutually orthogonal is redundant. You have to have something to be orthogonal to, and if you're orthogonal to it, it must be orthogonal to you.
    • "Mutually orthogonal" refers to the fact that the optical carriers are travelling perpendicular to each other, but are travelling through the same space (transmitted concurrently), as opposed to being transmitted using a tdma-type technology where the signal would be pulsed on one axis and then other consecutively. This is very much like the technology used in satellite communications, where each transponder has A and B poles.
  • Sweet... Can we use this new technology to ease the congestion over the trans-atlantic/pacific backbones???
    • Sorry, but any excess capacity will immediately be filled by script-kiddie ping floods.

      Anyone ever done a study on what percentage of traffic passing over backbones is ICMP-echo and reply?

      -NevDull

      • Re:Cool (Score:2, Funny)

        by RetroGeek (206522)
        We did a test on a private WAN and about 50% of the traffic was heartbeats.
        • You folks are using NetBeui as your filesharing system aren't ya?

          Switch it to NetBeui over TCP/IP (if you wish to avoid NFS) and you'll cut the heartbeats to 1/10th.

          Microsoft products and NetBeui are very chatty with the 'are you still there?' crap.
  • Dark fiber (Score:4, Interesting)

    by Foxxz (106642) on Tuesday October 09, 2001 @05:08PM (#2408130) Homepage
    This is going to help the industry alot. Right now there is pleanty of unused fiber, but the problem is the devices that use the fiber take too much room. if we build them smaller and faster we can increase capacity easily.



    -Foxxz

    • Re:Dark fiber (Score:5, Insightful)

      by sllort (442574) on Tuesday October 09, 2001 @05:27PM (#2408247) Homepage Journal
      This is going to help the industry alot. Right now there is pleanty of unused fiber, but the problem is the devices that use the fiber take too much room. if we build them smaller and faster we can increase capacity easily.

      The other thing that would help the industry would be to stop going bankrupt. Most to all of the CLECs (PS/Inet anyone?) are bankrupt and insolvent, and the major carriers - WorldCom, Verizon, Global Crossing - have horrible credit ratings and a total freeze on capital equipment purchasing. Right now no one is buying next generation optical equipment. Look at Nortel stock... if you bought $1000 of Nortel stock last year, you'd have $43 today. I won't even mention Lucent. Those are the big boys - the small ones (cough Iron Bridge cough) are all dead or dying.

      Optical equipment vendors have no customers. Optical equipment manufacturers are slashing R&D and personnel, and relying on existing revenue streams for survival.
      Optical network carriers are nearly bankrupt.

      ...and NO ONE is paying for premium bandwidth.

      So pretty much, this isn't gonna help anybody. The next advance in optical networking isn't going to be the next next-generation fiberoptic breakthrough. It's going to be a solvent carrier, or a paying customer for broadband.

      • by Anonymous Coward
        If you bought 1000 beers and returned the cans for $.05 each you would have $50.00

        Therfore save money, drink more.
      • Re:Dark fiber (Score:2, Redundant)

        by taliver (174409)
        Look at Nortel stock... if you bought $1000 of Nortel stock last year, you'd have $43 today.


        And If you'd had bought $1000 worth of beer last year, you'd have $75 due to the nickle from the deposit, and you'd have had 250 six packs... A much better ROI.
      • What I don't understand is that the demand is out there... at least among the people I talk to either on IRC or in person, everyone who is on POTS dial up is not there by choice. Maybe if they would have spent less time on the backbone and more time on the last mile, they wouldn't be insolvent.
      • Re:Dark fiber (Score:5, Insightful)

        by mangu (126918) on Tuesday October 09, 2001 @06:30PM (#2408514)
        The other thing that would help the industry would be to stop going bankrupt.


        That's a normal thing in industries. It happened in the 1890's when railroad equipment manufacturers went bankrupt. It happened in the 1930's when car manufacturers went bankrupt.

        When an industry is growing, a lot of new companies are spawned. Then, there comes a period of readjustment, when the market gets saturated and there is a mass extinction among companies.

      • Re:Dark fiber (Score:2, Insightful)

        by Happy Monkey (183927)
        In a larger sense, though, the provider bankrupcies are a good business plan for the country. Some companies go bankrupt laying the infrastructure, and then sell it cheap to other companies. These new companies are not saddled with the huge debt from the construction, and can offer the service much cheaper. It's almost like government sponsored infrastructure projects, except the "taxpayers" are voluntary stock and venture capital gamblers.

        The equipment manufacturer bankrupcies aren't so good, though.
      • ...and NO ONE is paying for premium bandwidth.

        They should have ran all that fiber to the home instead. No one's using all the bandwidth because there's not enough people to deliver it to. We need broadband to the home that works well and is universally available. Until then the high-bandwidth content will not be feasable.

    • Re:Dark fiber (Score:3, Insightful)

      by Shotgun (30919)
      No, the problem is that the devices that use the fiber are expensive and there is currently a glut of bandwidth. Oh, stop your screaming. It used to be that you'd pay $20/month for 64k of rarely used bandwidth. 64k is the nominal bandwidth assigned to a phone call in modern digital networks. If you made a long distance call (one that traversed central offices), you paid more and by the minute.

      An always-on, connect instantly to anywhere in the world, ADSL line has several hundred K of bandwidth, and people scream at anything above $49.95/month. There currently is a glut of supply driving down prices. These next generation inventions will only see production if they can supply more bandwith at the same equipment cost.

      In any case, the dark fiber will remain so until someone can light it really cheaply, or someone is willing to pay for the laser.

  • Now we have the next question that comes to mind. I want to know if there's a software solution to all of this, or if the hardware itself has to be upgraded to take advantage of these speeds.

    Also, I know it can be done over existing lines, which is great for the installed base, but it still doesn't help run them all over. I'm just lamenting the fact that they don't have, and probably won't have in my lifetime, fiber as widespread as telephone line. Sorry for the OT part.
    • Now we have the next question that comes to mind. I want to know if there's a software solution to all of this, or if the hardware itself has to be upgraded to take advantage of these speeds.

      I would guess the hardware would need to be upgraded since two light streams are being transmitted through the fiber. Unless of course you could rig up a fork/splice (probably involving duct tape of course) with a transmitter on each fork, but I doubt it. I'm going to go out on a limb here and guess that this new technology won't be economically feasible for most people for a while. I'd love to be proven wrong though.
    • I guess in my country (DE) especially in Eastern Germany, fiber is more spread than copper. Due to this, this sounds to me like a fabulous solution to get more bandwidth. Anyway since Im a student at the University of Paderborn I must say that great stuff is happening here... ;)

      *** Hm... this just tastes like inky nails...
  • Great, now bring it to my casa...or maybe light all the fiber that is already in the ground.
    • Su casa, is right. You're more likely to plop this between your router under the stairs to your workstation in the den sooner than you'll realize any benefit beyond your door. But, hey, there's always hope you'll see it before arthritis and failing eyesight set in.


      Time for my own fibre supplement...

  • Remember (Score:1, Insightful)

    by Haxx (314221)

    that's 85,899,345,920 Bps

    Up from 300 Bps 14 years ago. Not too shabby.

    • Re:Remember (Score:1, Informative)

      by Anonymous Coward
      Wrong. 300bps was the speed of your f'ing modem, not the state of the art high bandwidth technology of the day.


      A more appropriate comparison is to 56kbps modems we have today. 300 to 56000 in 14 years. That roughly a doubling of speed every 2 years. Slower than computer CPU development, but then we are limited by the telco equipment, aren't we.

    • Interestingly, atleast to me, that's almost exactly 4x per year. As in 300 * 4^14 is almost exactly 85,899,345,920.

      Justin Dubs
    • Well, that 300bps was what you could manage across an analogue telephone line with a commercially-available modem.

      Telecom backbones, even 14 years ago, were waaay beyond 300bps. And this technology really is backbone stuff, not for us consumers *wistful sigh*
      • in Newark, NJ. Nobody was using it for data back then of course, but squeezing 1.544 megabits/sec onto a copper pair, in order to move voice circuits around, is nothing new.

        I wish the Slashdot team knew a bit more about telecom, they'd accept fewer of these stories and say fewer stupid things about them. "Chronically overloaded backbone" my ass, there are millions of miles of dark fiber out there. The glass isn't the problem, it's the silicon, the greenbacks, and the red tape that make things suck.
  • 300km worth of cable = 10MBytes of storage with access times of 1 msec... So I guess we have to wait until we can pump bandwidth up 4 orders of magnitude to have a neat little system... (with 300km worth of cable in a drum...)
    • If you could make the cable dense enough to fit in a space the size of a normal harddrive -- and made it low power (already solid state) that would rock my world as a swap device.

      I'm willing to accept an average of 1msec seeks (600km of fibre) to double capacity.
  • by nizo (81281) on Tuesday October 09, 2001 @05:13PM (#2408161) Homepage Journal
    From the babelfish translation:


    Additionally it possesses a controlling mean, which is to after-pursue even largest polarization modifications, as they occur on very long transmission circuits contrary to competitive systems also, noly-break.

    Once I figure out what a noly-break is, I should be able to build my very own high speed home network!

    • debalelized: In contrast to competitive systems it also contains a controlling unit, which will follow without causing interruptions even the largest changes in polarity, as they will occur in very long distance transmissions.

      Go, girl! Into the bright/light future of home networking.

      Chriss
    • For some reason, Babel Fish translates "unterbrechungsfrei" as "noly-break". A much better translation would be "free of interruption".
  • The "backbone" of the whole internet and telephone net consists of optical fibers. For transmission capacity doubling each optical wavelength may carry two signals with mutually orthogonal vibration directions. The results of this technology could be outstanding.

    Now when can I get this to the curb?
  • by Renraku (518261) on Tuesday October 09, 2001 @05:14PM (#2408168) Homepage
    Maybe some day cutting a fiber line would yield deadly results. Imagine accidently digging through a fiber line only to be cut in half by the power of the beam. That would rule! As if being electrocuted to death wasn't enough, soon we can be killed by data...I can see where the 'freak accident causes supergenius to be born' movies are going to come from..
    • Hmmm, if the countryside was littered with laser-blinded backhoe operators as a result of their slicing through the wrong cable, I don't know how that would be much worse than the current situation. You know what they will say: there are old backhoe operators, and bold backhoe operators, but there are no old, bold backhoe operators :)

    • by Anonymous Coward
      and how much would it piss you off to be sliced in half by a warezed copy of windows xp going across the fiber?
  • to be able to throughput at that speed, I can't imagine the hardware that is needed...

    I mean, I hope that nobody had the idea that he will be able to have it directly into his Athlon 1.4 Ghz... Poor fool...!
  • Does anyone have a link to a good translation of the article [golem.de]? The translation at altavista is incomprehensible!

    Thanks!
    • Re:Langauge (Score:1, Funny)

      by Anonymous Coward
      With what do you deal with yourselves? I have always babelfishuebersetzungen found, in order to be completely readable and understandable!
  • Does orthagonality relate to the wavelength or the relative angles the light is sent? If the latter, any reason they couldnt' use colour as a second channel? (particular wavelengths)
    • by astroboy (1125) <ljdursi@gmail.com> on Tuesday October 09, 2001 @05:43PM (#2408324) Homepage
      The `orthogonality' here refers to polarization. For a little intro, see a page like this one at Case Western [cwru.edu]. Light's an electromagnetic wave, consisting of an electrical and a magnetic field at right angles to each other.

      The beams in this article are orthogonal in the sense that channel #1 has it's E-field pointed prependicular to channel #2's E-field so they won't interfere with each other (so they're `orthogonal' in the usual compu-geek sense of the term, too.)

      The german team seems to have solved two big engineering problems with sending two channels of information this way. One is to send a mean-polarized signal so that you can compare the two channels against it (kind of a carrier signal for polarization) to see which channel is which.

      The other I confess to not understanding. Apparently there are sync problems -- signals carried one polarization may travel faster than the other polarization. I can only guess that this is a problem caused by inhomogenaities in fibre. Whatever its caused by, they've managed to measure it and compensate for it.

      As for your other question, they definately can and do use frequency as a way of encoding information. Just like with radio signals, you can use the brightness of the light (amplitude modulation, or AM) or its color (frequency modulation, FM). In practice, FM is less problematic; the amplitude of a signal is easily confused by noise, whereas frequency is much less so.

      • Apparently there are sync problems -- signals carried one polarization may travel faster than the other polarization.


        This phenomenon is called polarization-mode dispersion and we just covered it in my fiber-optic communications class. It occurs because of birefrigence, which is the phenomenon where different polarizations see different refractive indices. Since refractive index is the speed of light in vacuum divided by speed of light in a medium, this means signals with different polarizations will travel different speeds. Even worse, since fiber birefringence is probably stress-induced and varies over the length of the fiber, it is difficult to tell what the polarization axes of the fiber are so that you can minimize this effect.

        Polarization-mode dispersion is a problem even when you're not multiplexing by polarization because it results in the ordinary and extraordinary polarization of a light pulse separating and possibly colliding with other pulses, thereby limiting the bandwidth of the fiber. On the other hand, if you use the ordinary polarization as one channel and the extraordinary polarization as a separate channel, both channels will propagate with zero polarization-mode dispersion and double the effective bandwidth of the fiber. They will propagate at different speeds, but that really isn't an issue as long as the light pulses that represent your 0's and 1's aren't spreading.

        The trick is determining the ordinary and extraordinary axes of the fiber, which is the breakthrough that this group made. It sounds like they use a reference channel to determine the ordinary and extraordinary polarization axes of the fiber and also to measure the change in polarization introduced by the fiber so that they can demultiplex the two polarization channels. This is a very simple and elegant way to negate polarization mode dispersion and to enable polarization-division multiplexing.
    • Orthogonality in this case refers to modes of the electric field. A mode is labeled by a frequency and a polarization state. So, yes, two beams of different wavelength are orthogonal modes, and can be resolved by using a grating to diffract each component to a seperate detector. This is called WDM -- wavelength division multiplexing.

      States with opposite polarization (horizontal and vertical, right and left circular, etc) are also orthogonal modes, and can be seperated, for instance, by a polarizing beam splitter. This is PDM.

      The total bandwidth of a communication link is bps/mode * useful modes, so either increasing the number of frequencies or polarizations, or both, can improve bandwidth.

      WDM is limited because each pulse actually covers a range of frequencies, and you need to choose them far enough apart that they don't overlap, or you won't be able to discriminate them well. PDM is limited because it is hard to get fibers to not fs*k with the polarization of light, plus there are only two orthogonal states, so you can only easily get a factor of 2 improvment in bandwidth.
  • Now I can get spammed in half the time.


    It's ironic that this article comes on the heels of some articles I just saw (in metamoderation) about how oversold services (DSL/Cablemodem) are. This would be a great thing, if any company still has the capital to lay new fiber, though I expect many are just trying to eke out a returns on what they already have. My ISP, Concentric/XO was last listed at $0.40 a share, and they're advertising cheep long distance, etc. right now.

  • by case_igl (103589) on Tuesday October 09, 2001 @05:17PM (#2408194) Homepage
    It seems every year we find a way to double the amount of data that we can send down fiber. As a result of this, companies are actually deploying less new fiber in the field and taking older lines out of commission.

    One of the things that worries me about this is the increased vulnerability. In the past, huge fiber networks were used that can be one tenth the size today. All too often a clueless construction worker rips up a section of fiber and causes some havok.

    Won't this kind of thing happen more frequently if less fiber is deployed that can handle more traffic? And does this bring us any closer to fiber to the curb - it doesn't seem like it.
    • by sllort (442574) on Tuesday October 09, 2001 @05:34PM (#2408286) Homepage Journal
      All too often a clueless construction worker rips up a section of fiber and causes some havok.

      The industry euphimism for this phenomenon is a "backhoe failure". Metro fiberoptics are all deployed in a "ring" configuration - if a ring is cut, the traffic is sent the other direction on the ring withing 50 milliseconds. The operative protocol here is called SONET [atd.net]. SONET rings have been around for a long time, and they pretty much solve the issue of backhoe failures. Some vendors are pushing proprietary mesh-based architectures which offer even more redundancy.

      The issue you bring up, however, does exist on one-way long-haul fiberoptic lines. Major carriers spend millions on 24 hour overflights by patrol helicopters to monitor these fibers for cuts - and some of the largest players in the telco field are oil suppliers because they already patrol their oil pipelines for just this kind of event; burying fiber next to the pipeline is cheap by comparison.

      The massive transmission capabilities introduced by advances in fiberoptics DO give us more ability to heal networks, because they give us additional load-bearing capability during failure. The missing piece is actually building equipment which will heal the network effectively, in time. If you're truly interested in ongoing research in this area, open up google and ask it about "GMPLS".

      Enjoy.
      • I know this is a little off topic, but I think the correct term is "Backhoe Fade". A quick search turned up an "official" government project [petting-zoo.net].

        BTW, the word "fade" is a throwback to the time when most longhaul communications was done using troposcatter microwave systems. Small atmospheric changes such as rain, volcanic dust, solar flares and sunspots would cause the Recieve Signal Level to drop. Ok, Ok, who am I kidding; those bastards would fade at dawn, dusk, mid-day, mid-night, summer and winter solstace, equinox, and any time someone stood too close to the radio. A guy I knew actually shot a radio once for excessive fade. He claimed it was an accident, but the investigator was clued in by the fact that there were 3 holes in the radio...

      • Interesting.

        But I still think the primary reasons for using oil and rail lines is that the oil and rail companies already own the right of way. I can't imagine what it would take to get 3,000 miles of clear path across the U.S. in the 21st century. It probably saves several billion dollars in negotiations and leases.

        Getting a little economy of scale on maintenance is a nice bonus.

        --Blair
    • People have this tendancy to put all of the cables in the same place anyway, because you can dig a huge ditch or dig up all the streets once, and put in a whole bunch of cables, or because there's only a few paths that you can afford to dig up. Having greater capacity on each cable just means that you won't need as many cables in the same hole. Whatever makes a cable break is likely to kill the whole group. The redundency comes largely from wanting to connect each pair of points for normal operation, which means that you'll have other routes if one goes down.
    • And does this bring us any closer to fiber to the curb - it doesn't seem like it.

      WE have fiber to the curb. ;-)

      As part of a experimental project the whole suburb where I live was wired with fiber to the curb. Unfortunately the telco since decided to put a hold on the project and hasn't really taken advantage of the investment. There was a debate about offer superior versions of DSL, but they decided that cost was too prohibitive for the small client base. They might be offering it to businesses, but they aren't to consumers.

      It's not just a matter of having everything wired up, but there is also an issue of having a cost effective use for it. If you're surfing the internet and playing online games, DSL or Cable offers as much speed as most people need.

      Right now the only visible consequence of the fiber to the curb, is that ALL of this suburb can get DSL regardless of their location relative to the CO. Now if only someone will hurry up with widespread videophones...
    • Is anyone really taking fiber out? In my experience DWDM systems are used to relieve "fiber exhaust" when all the fiber in an area is already being used and there's a demand for more capacity you take the OC48 muxes off the fiber and put DWDM muxes on it. Then you plug the OC48 muxes into the DWDM muxes leaving you with 30+ new channels (frequently called lambdas).

      In case you weren't aware, people hate having the streets dug up. They hate the traffic delays and they hate the ruts that inevitably result from digging up pavement. Consequently, telecom companies have a tough time getting permits to lay new fiber. That's why being able to send more data without laying more fiber is a good thing.

      If a ring is cut (I've heard it called "backhoe fade" as opposed to another poster's mention of "backhoe failure") it protection switches automatically if the tributaries are routed correctly, which they may not be. One side effect of using DWDMs is that they can protect the whole SONET rings riding them even if the low speed electrical tribs aren't routed with protection.
  • Nitpicks (Score:2, Informative)

    by Anonymous Coward
    First, twice 40Gbps is not 85,899,345,920 bps, it is actually 80,000,000,000 +/- 1,000,000,000. We don't measure Gbps in powers of 2. Secondly, the internet backbone is not overloaded, but is running at about 20% capacity according to the people who operate it.
    • the internet backbone is not overloaded, but is running at about 20% capacity according to the people who operate it.

      And on the declining revenues they're getting by on, my hat's off to those folks! [dragonswest.com]

  • Patents, anyone? (Score:1, Interesting)

    by Anonymous Coward
    Thoughtfull /.'ers can ignore this.

    Knee-jerk /.'ers, ask yourself: Once you've realized what a cool thing this is, and understand that hard work went into making it happen, are you then going to demand they make it "Open" and "Free" and not patent it, because Patents Are Bad and Sharing Intellectual Property is the Right of All Mankind? Or will you realize that they have a right to benefit from their hard work and wish them luck?

    Great job, and I wish them great success, for the selfish reason that I wish to benefit from this technology and think it could actually reduce infrastructure costs, thus (somewhat slightly) reducing my costs (or at least delaying the next inevitable increase).


    • Knee-jerk /.'ers, ask yourself: Once you've realized what a cool thing this is, and understand that hard work went into making it happen, are you then going to demand they make it "Open" and "Free" and not patent it, because Patents Are Bad and Sharing Intellectual Property is the Right of All Mankind? Or will you realize that they have a right to benefit from their hard work and wish them luck?

      Good post. I agree with you, and naturally disagree with the "we must share all advances for the good of the people" attitude. Communism isn't counter-culture, anti-establishment, nor is it cool. It just plain sucks.

      • Good post. I agree with you, and naturally disagree with the "we must share all advances for the good of the people" attitude. Communism isn't counter-culture, anti-establishment, nor is it cool. It just plain sucks.

        Good post for you too. It is one thing when people choose to share things for the advancement of all people, like GPL and public domain and such, but it is a different thing when you don't believe in property rights at all.
    • Imagine if HTML was patented way back in the 1.0 days. By now the owners of the patent would have:

      • Charged so much (in the name of the Profit) as to run off all potential users
      • Enlisted Congress to enact draconian penalties to prevent people from "stealing" the precious bodily^H^H^H^H^H^H intellectual property
      • Bankrupted the company through poor business practices, letting the fruits of the engineers' labor rot away in some attorney's vault

      Instead they gave freely and changed the world. ;)

  • "As we all know, optical fibers build the (cronically overloaded) backbone of our beloved Net.

    Hmm, and same Timothy posted this article [slashdot.org] on June 25th about a lot of fiberoptic cables that have been put into the ground but haven't been put to work.
    You gotta love the consistency of Slashdot posts :)

    • by sllort (442574) on Tuesday October 09, 2001 @05:49PM (#2408350) Homepage Journal
      Hmm, and same Timothy posted this article [slashdot.org] on June 25th about a lot of fiberoptic cables that have been put into the ground but haven't been put to work.
      You gotta love the consistency of Slashdot posts :)


      Dark fiber is fiber with no optical equipment connected to it. Fiber is not the expensive part of optical networking. Air-conditioned environment-controlled closet space filled with millions of dollars of self-healing optical equipment is the expensive part. A lot of metro optical carriers use the benchmark of $100,000 per month per 7 foot rack in operating costs. The denser the equipment, the cheaper the equipment, the more of that dark fiber the carriers can light to form the backbone of the Internet.

      So, in short, Slashdot was right and you were totally wrong. Or Insightful. Your choice.
  • dispersal of the light waves

    Modal or spectral dispersion? I'm assuming they're using singlemode fiber, so it's likely spectral dispersion, for those who wonder (and lazy to read the article).
  • by skroz (7870)
    How does their technique differ from dense wave divisional multiplexing? Anyone know?
    • In WDM (I'm not sure the acronym is right) what you do is send more than one signal by using different light colours (frequencies) that don't interfer with each other.
      What you do here is send two signals that have the same frequency but orthogonal polarizations so they don't interfere to each other either; imagine one of the waves going on the vertical direction while the other goes horitzontal, that would be orthogonal and you could recover both the vertical and the orthogonal one independently.
    • Re:DWDM? (Score:3, Informative)

      by Snags (18929)
      DWDM (dense wavelength division multiplexing) referrs to multiplexing multiple optical signals on a fiber by having them exist at different wavelengths of light. This is very similar to how the cable TV line carries 100 or so channels of TV signal by having them at different frequencies.

      The D (for dense) means that there are many such channels, often 40+. This article referrs to having two 40Gb/s channels at the same wavelength, but with opposite polarizations so they don't interfere with each other much. This same signal could be used as a base for a DWDM system to effectively double the current maximum speed of like 10Tb/s (40Gb/s * 250 channels).
  • 80 Gbit/s != 85 899 345 920 bps

    The prefixes kilo, mega, giga are SI prefixes and are always powers of 10, and should never, I repeat never, be used when talking about powers of 2. Use the terms "large gigabits/gigabytes" or "kibis, mebis and gibis" instead, to avoid confusion.

    In telecommiunication measurements like bps, the SI prefixes have traditionally always been used properly.
  • I work for williamscommunications.com and we already use DWDM (Dense Wave Division Mulitiplexing), which allows multiple freqs of light down the same strand. OC-192 transport systems with DWDM, operate in duplex on a single fiber, delivering up to 80 Gbps in eight waves in each direction.

    Work w/ this everyday, why is this news???
    • The fact that they've just doubled it to 160GBps in your case.

      It's not DWDM that they're using -- but (from what I can tell) it also doesn't negate using DWDM along side.

      Kinda like satelite transmissions using horizonal, vertical, left circular and right circular polorizations at the same frequency. Then for kicks they start using many channels in that manner.
  • by NerveGas (168686) on Tuesday October 09, 2001 @06:03PM (#2408407)
    We already have much more fiber capacity than we can use. The real bottleneck of the Internet right now is... the switching. OC-768 units (38.8 gigabits/sec) won't even reach volume production until 2003 or later, and they wouldn't even handle half of one of these fibers, let alone multiple fibers coming from various locations. It's like running a 2" diameter fuel line to the engine of your Hyundai.

    All-optical switches have been developed, but are not going to be widely deployed for some time. I have a feeling that even all-optical switches will be many years before they reach the speeds needed for 80 gb/s fibers.

    The true improvement of the Internet will occur when switching capacity increases by at least an order of magnitude in a very short amount of time. Right now, good, guaranteed bandwidth is barely any less than it was back in 1997. Sure, as switching capacity slowly progresses to fill the needs of the backbone providers, the Internet keeps running - but you still end up paying out the nose for guaranteed bandwidth. Once the switches catch up with the fibers, however, that *might* change. Maybe.

    steve
    • Somebody mod this up!

      Even when you have all-optical switches, they will initially be circuit switches, with nailed-up optical paths betweeen edge devices, putting more stress on the edge routers because they have more circuits to switch between. People are researching packet switching and burst switching but that's even further off.
      • Yeah, mod BOTH of those up.

        There's a huge difference between nailed-up connections and packet-level switching. I mean, hell, a punched-down copper jumper is about as sophisticated as the "optical switches" they have now.

        When we get optical logic that can examine packet headers at high speeds, we'll see some development. But for right now, the bottleneck is the silicon chip at the end of the strand of glass.
  • I propose that in response to Microsoft's usurping of the dot, we counter-respond with an acquisition of the asterisk.

    Thus, instead of using .NET, or The Net, or 'net, or Net, we all start using *Net.

    That way we can pretty much cover all bases, since everyone knows that * is a wildcard - the All-unifying Infinite Eternal Symbol of All.

    All those in favor, say "*me"...
  • by JimDog (443171)
    I don't understand the importance of this discovery. I'm pretty sure existing DWDM systems can put at least 16 wavelengths on a single fiber at OC-192 (10 Gbps) speeds for a total capacity of 160 Gbps...
    • by JimDog (443171) on Tuesday October 09, 2001 @07:06PM (#2408652)
      Indeed, upon further research, we're already way beyond 80 Gbps on a single fiber. DWDM [techtarget.com] (dense wave division multiplexing) can increase the capacity of a single fiber to 1.6 Tbps, and soon to 3.2 Tbps with 80 wavelengths at OC-768 according to this press release from NEC [nec.co.jp]. As the press release states, a 3.2 Tbps data rate is the equivalent of transmitting 1600 feature-length films every second.
    • maybe they meant they were using two, orthoganal (via the polarization) signals of the same wavelength, so that you can densely divide and multiplex that however you like, and you can double the resulting bandwidth via polarizing and recycling that wavelength.

      16 wavelengths = 160 Gbps
      16 wavelengths, twice each (one's all sideways from thuther) = 320 Gbps.

      Though I'm just talking out of my ass.
  • THIS IS NOT NEWS (Score:2, Informative)

    by SETY (46845)
    From the article I quote:

    The system transmits data of two polarization channels with 40Gbit/s each, i.e., together 80Gb/s bit per second, over a 212km long optical fiber - much further than otherwise possible.

    This is kind of an intresting experiemnt, but this is not news. The "otherwise possibe" part makes it sound like no one has done PMD compensation before, this is false. Here is why:


    1. PMD compensators are being built by many research groups. You still can't call up an order one (AFAIK), but soon.
    2. PMD (mean DGD, differential group delay). DGD changes with time and wavelength.
    3. PMD on buried fiber varies slowly. It is easy to compensate.
    4. Nortel, Alcatel and others with be releasing 40 GB/s (per WAVELENGTH) systems next year. They are suppose to run 100's of km, between regens and at many wavelengths (160?).


    Here is a link with almost all peer reviewed papers on PMD:
    [tu-harburg.de]
    Here one can see many references to PMD compensation and even some at bit rates of 160 GB/s. With PMD compensation the line speed isn't that important, it is the accuracy and speed of your compensation.


    This is not a break through.

  • Optics explained... (Score:3, Informative)

    by peter_gzowski (465076) on Tuesday October 09, 2001 @06:57PM (#2408608) Homepage
    I see some others posting explanations about physics behind this, but it seems a bit unsatisfactory for some. Here's my best shot at it:

    There are two orthogonal polarization modes that propagate down fiber, meaning the there's a sort of up-down oscillation of the electric field (one mode), and a left-right oscillation (other mode). If fiber were perfect, you could send a signal along each polarization, and they wouldn't bother (interfere with) one another, but it's not. If you send polarized light down a fiber, it will not keep the same polarization (unless you use polarization-maintaining fiber, but that's a pain, and you can only send one polarization down).

    So people generally send down (relavitively) unpolarized light. They modulate this one signal as fast as they can (getting about 40Gb/s), and then deal with dispersion as best they can.

    Dispersion results from the spread in frequencies (colours) of your signal (each colour travels a different speed in the fiber) and also from the fact that a fiber has polarization mode dispersion (the part of the signal along one polarization axis travels at a different speed than the other part, called PMD from here on in). Both of these effects cause a pulse that you send down the fiber to be distorted (part of the pulse travels at a different speed than the other part). Chromatic dispersion (the first kind) has been dealt with (fibers have a wavelength at which the loss is lowest and a wavelength at which the chromatic dispersion is lowest, and it's been worked such that these two things are at basically the same wavelength), but PMD is a big limitation to pushing the capabilities of fiber. This was stated on the front page post:

    They say the only big problem was the dispersal of the light waves which limits the data rate.

    I think that should read "dispersion", not "dispersal".

    So, what these guys have done is made a PMD compensator. Somehow it automatically makes sure that a given polarization of light stays in that polarization as it travels down the fiber. If one can preserve the polarization of both modes (which is different than polarization maintaining fiber, which takes ONE polarization of light and keeps it polarized), and then send a signal along each polarization axis, then one doesn't need to deal with PMD, because within a given signal, all the pulses are travelling at the same rate.

    Then, if you don't have to deal with PMD, then there's very little to slow you down in pushing data through the fiber, basically just how fast you can modulate your laser (I think you could drive a LiNbO3 Mach-Zhender modulator up to about 80Gb/s or so, whereas I think in the article they were driving it at 40Gb/s). That's why they say the data rate was only limited by available equipment. I'm not sure how the PMD compensator works, I'll have to read the actual article more closely. I hope this helps!
  • Making bigger and bigger pipes is the way of the net. The technology just has to get better by making the rates higher and the packages smaller.

    The next question is, what do we do with all this new capacity? The telecommunications industry is finding all this out since so much infrastructure was built during the boom and everything went bust. There was so much infrastructure out there that was completely useless (think dark fiber) because of incomplete implementation.

    They put plenty of fiber in the ground and run out of money before they can get any equipment to light it up. They put plenty of DWDM equipment to light the fiber but they can't sell a whole OC-48 to anyone at a competitive price. They get tons of metro networking equipment but they've just spent all their money and can't make a management system to turn up any metro circuits.

    So, these kinds of technological improvements are the greatest thing in the world and they have to keep pushing the envelope. However, there must be concurrent development along all other lines to manage all these ass-kicking boxes and make them usable! If not, no one will buy it because it can't contribute to a sustainable business model.
  • by Chagrin (128939) on Tuesday October 09, 2001 @09:17PM (#2408928) Homepage
    • As we all know, optical fibers build the (cronically overloaded) backbone of our beloved Net.
    If it's overloaded by cron, couldn't we just kill the cron daemon?

  • Bytes per second != bits per second

    Somebody please correct the story.

  • "polarization division multiplex data transmission system" [using an] "automatic optical compensator of polarization mode dispersion"

    If it's twice as fast but takes four times as long to say it, does that actually mean its effect is half the speed? The article didn't say if the "test-line of 212 km" was just so they could write the name on the side.

    And to think people believe we IT staff make up impenetrable terminology in an attempt to justify our salaries!
  • As we all know, optical fibers build the (cronically overloaded) backbone of our beloved Net


    While I am always for extending bandwidth, I jump on the term "chronically overloaded" (note the letter "h", which seperates chronic from mere cronjobs)... Not long ago, regarding the 9/11 effects of everyone and their dog logging on to the net on the search for information, I read that the net backbone currently is anywhere between 40% and 50% at any given time. It took 9/11 to get peaks up to 80%-85%.

    I tend to think being at half load most of the time is not anywhere near "chronical overload".

Today's scientific question is: What in the world is electricity? And where does it go after it leaves the toaster? -- Dave Barry, "What is Electricity?"

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