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Mega Bandwidth Acheived
PDG writes "The
german engineering firm Siemans has produced the rate 1.2
tbs (YES, tera bits per second) over a SINGLE strand of
fiber, thus proving the limitless power of fiber. "
One step closer to the ultimate goal for
humanity: infinite bandwidth. Or maybe thats just my ultimate
goal. Nevermind.
Carefull with that word, "limitless." Even fiber has a finite bandwidth, even if it is very large. I don't know for sure what it is, but since we can propagate femtosecond optical pulses in fiber, I would guess on the order of 10's of THz.
In any case, given the resource hungry nature of today's applications, I'm sure we'll smack up against the bandwidth limit of fiber RSN.
details, details...
a BIG game of quake
trade hundreds of mp3's, and mpg's
use those net fones
and maybe realvideo will be clear for once...
does anyone have anything else?
Multiple optical elements? Lasers? I had heard from somewhere that the LED's they use to light the fiber were too slow to achieve this kind of bandwidth.
What can push that kind of bandwidth? Yeah it would be neat to have one in my house, but your garden variety pentium can't even fill up a Fast Ethernet connection. I guess this has more backbone applications (implications?).
It is not merely an engineering firm, it is one of the worlds biggest multinational technology corporations, Siemens...
I believe they use a special tranciever chip that uses several different wavelengths, the chip sort of crams all the different wavelengths [colors] into the same fiber. I've seen a prototype for a chip that separates two wavelengths from each others, it is using a prisma that bends the light into "the colors of the rainbow", then there's just separate receivers for different parts of the spectre.
Am I right?
Unfortunately, with today's physics, we can never achieve infinite BW. So it can't really be a goal of ours until we set out some new physics...!
jason
More technology for the Cable Modem/ADSL monopolies to keep us from having access to!
Now this is a story worthy of slashdot!
A tbs-only Internet (I3?) would be an awesome sight to behold. It would finally make a world-wide computing cluster possibly--and think what we could do with that!
Wow, man, if we get Linux drivers for this we could make one really _awesome_ Beowulf cluster. Kewl, huh?
[For the humor-impaired, the above is a satire of the idiots who think Beowulf is actually useful for anything but a very narrow range of tasks.]
Muhahahaha! It doesn't matter how much bandwidth is available. Users will always find a way to max it out. 1600x1200x24bppx30fps two-way live video streams? It'll happen when it can happen.
ok theory man.
try it and tell us your results.
I have tried it
All you have to do, is devise a emitter/receiver that can manipulate finer and finer variants in the individual wavelengths. Let's say they're using 10 nm variances. Eventually, they could use 1 nm, then .1, then .001. As long as we can continue to generate and detect more and more minute changes, we can increase the maximum bandwidth. We could also venture outside of the range of visible light, for an even larger range.
hope you don't want to use anything besides realaudio....
Right, but the minimum degree of separation between wavelengths/channels will become very small before we reach a limit. THe max bandwidth over a single fiber is not limitless, but very, very high.
I had a realization the other day. In the old days, we all had terminals hooked to a time-sharing mainframe. Processor time was expensive because there was a shortage.
Then we started getting desktop PCs. Now processor time is cheap for regular tasks, but still semi-expensive for large tasks (because multi-CPU machines are very expensive).
Let's try this instead: Every desktop on the network (say, a corporate LAN) should be a node in a computing cluster. The user can use it just as before (checking email, running some software, surfing the web). But we can use all their spare cycles (and if they leave the machines on at night that's pretty good) to run the large tasks.
I realize this isn't a new idea, but I don't think it has fully penetrated corporate America how useful this would be. Obviously they have to be parallelizable tasks, but many tasks are, at least on some level. For example, in my company we run reports overnight. Each report could be sent to a different PC to be run. Would probably reduce our running time from ~6 hours to ~(length of longest report).
With an even higher speed network (1.2 tbs) more data-sharing is possible making more parallization attractive.
Other uses:
Software companies (on the order of IBM or MS) could run their nightly build on the cluster.
Companies with a lot of PCs but little need for a cluster could rent out the power overnight. 500 CPUs for 12 hours could do a lot of work. And the money is practically all profit!
. . . people who don't give a shit about [Linux] Beowulf one way or another aren't "humor-impaired"; they're "life-enabled".
Deal.
Not that I wouldn't have found your post funny if I DID give a shit.
Most likely they're using a SSD, a solid state ram drive, consisting of a high-speed ram chip brick. Crazy expensive but it doesn't get much faster.
Now *that's* a lot of TPM (thrusts per minute)
Well - I remembered but had to look up the exact figure to be sure ;) Anyway, the theoretical limit on fiber optic cable is about 50THz. Note that even if you could achieve a 50THz transmission rate, your data rate would be somewhat lower - you cant just send the raw bits, you need some type of encoding scheme to be sure you can correctly receive the bits at the other end of the serial link. (Some examples - a simple asynchronous UART uses an extra start and stop bit for every 8 bits of data. Another example would be Biphase Mark Signaling like is used on an AES/EBU or SPDIF serial audio link.) And then, well your doing your engineering homework, you will probably decide to add some error checking/correction scheme on top of this just to be safe. So - all that said, lets say you theoretically achieve 25Tbps on a theoretical 50THz fiber optic link - that's still pretty good ;)
Don't tell them that, they'll only get curious and want to come and visit :)
Typical modems don't go above 1200 (or is it 2400?) baud (phase changes). All modem speeds above that are reached by encoding multiple bits pr. phase change.
Dude! Even if you don't have a use for a 1Tb network in your house doesn't mean there is no use for the technology! For example, lets say you want a 100Mbit link to the Internet - all those 100Mbit links add up and you've got to have some kind of ultra fast backbone to handle the traffic! Duh!
But just think for a moment - lets say you had a 1Tb link to your house. An ultra high fidelity uncompressed CD (say 75 minutes at 96kHz, 24bit stereo) is like 2.6 Gigabytes or about 20 Gigabits of data. You could download like 50 of these every second!
Now, if you were to settle for today's CD quality (74 minutes at 44kHz, 16bit stereo) well, that's only about 780 Megabytes per disc or about 6.2 Gigabits of data. You could download like 160 of these every second!
Now, if you were to settle for crappy sounding 12:1 compressed MPEG Layer 3 - well, shame on you for being a tone deaf fool but you could download 1920 full CDs per second on your 1Tbit link.
I guess your right - this does sound a little excessive. I think you would run out of good CDs to download even in ultra high quality 96k 24bit format pretty quick. I know! You could use it to watch real time uncompressed high definition television in component format at 100fps!!! Hmmm - 1920 x 1080 x 3 x 8 x 100 = 4.9 Gigabits per second. Shit! Well, I guess you could watch a bunch of those channels simultaneously and download some ultra high fidelity CDs at the same time. I don't know, maybe your right, maybe 1Tbps is just too much bandwidth.
But that's the "one bit, one phase shift" assumptions, which didn't hold true for analog modems, and that I doubt will hold true for fibers. Remember, this is analog transfer, there's not just on and off, you can encode more than one bit pr. phase shift.
Any physical fiber that I've heard of has a certain attenuation per length,
for communication fiber it's spec'd in dB/km of fiber. This attenuation varies with wavelength,
there is a "best" wavelength eg. 1.6 microns; attenuation goes up at higher and
lower frequencies. Theoretical information capacity is a function of
frequency bandwidth and signal-to-noise ratio. For fixed input power, the latter goes down
as the attenuation goes up. The figure of merit for comm. fiber is a bandwidth-length product, ie,
100 mbps/10 km. You could go faster, but with a shorter run, or farther with a lower datarate, given
the same transmitter power and receiver noise level. A different way of thinking about the receiver is
as a quantum detector, since light is quantized into photons. Then the information capacity depends on how well you
can localize (in time) the detection of a photon, and how many photons you can detect per second and still distinguish them. -john beale (beale@best.com)
Yes but that's probably realistic. Fiber optic cable works because its internal refractive index is such that a particular band of light is efficiently transmitted. Sure, in theory, you could transmit on several different wavelengths within that band or use other techniques such as trying to encode multiple bits per phase change with amplitude or both but reality is your worst nightmare and you will still hit a ceiling either because of interference in the cable, inability to make a transmitter that can switch fast enough, a receive that can capture transitions fast enough, or similar.
man I could download all the linux distros and test out which one I really like!!!! And it would take 3 weeks to download!
That's probably the cutest description I've ever heard for the"bank with adjacent electronics division", Siemens. (> 400k employees)
But anyway: Extremely cool news.
This is stuff that really matters!
Ill still be able to 0wn it on my 28.8
Even if you had a perfectly reflective fiber optic channel that didn't lose a single photon, you still would have limited bandwidth. The granularity of the wavelength of a photon is related to plank's constant. The smallest difference in two wavelengths is an integer multiple of planks constant, which means there are only so many different wavelengths in the visible light spectrum. Granted the granularity is very small, but it's not zero.
phase and amplitude determine the color in a wavelength of light. ;-) so I guess is about the symbot constellations
More bandwidth doesn't make Quake [much] better. What will do Quake better is increasing the speed of light. ergo, LPB ("Low Ping Bastards")
What, that crap posted on ZDNet? Sorry, I was busy reading the section about fiber optics in my Physics text. ;) Yeah, 60 channels x 20Gbit each using 60 different wavelengths of light and WDM. But those 60 wavelengths of light could (in fact, probably are) in a fairly narrow frequency band and there by fit within the optimal transmission band of the particular cable being used. I didn't say you couldn't use multiple bands, I said that even if you did there is still going to be a limit.
It's just as simple to lay 10, or 100, or even 1000 fibers as it is to lay 1, so we really shouldn't have to worry about maxing out our bandwidth any time soon.
..
Unfortunately, in the rush to have fiber optic networks, the phone companies generally burried a single strand instead of 10 or 100. Marketing strikes again
...and if polarization is consistent through the
fiber you can get two "channels" per color.
nb. I don't think polarization stays constant
through fiber optics or through the doped fiber
amplifiers mentioned in another thread.
I agree...
... but dividing fiber into millions of channels .. may not be the best way ti go... however human it may seem.. to divide great things into smaller things...
I do believe Muliplexing is not really relative to bwndwidth.. it's cool to think about it when you are a Telco
The maximum potential routing bandwidth currently is on the order of 100 Gb/s. But thats with current routers. There is some study being done on nanomirrors and nanolasers (for those who don't know, mirrors and lasers that are smaller than the wavelength of light be directed or created) that could be used as routers for these types of insane bandwidth machinations. Now while 1.2 tbs is interesting its not half as interesting as the routers being researched...
1 gigabit/s == 125MB/s
read first, then flame
I think the 3 in the calculation above should be 4, shouldn't it? In addition to hue, chrominance(sp?), and luminosity, component video has a sync signal as well, doesn't it? At least I'm pretty sure HDTV does.
why don't you do something instead of being so goddamned self-righteous. also, this is the computer INDUSTRY - the point is to make money, not necessarily to come up with technology cool enough to satisfy undergrad trolls on /. when YOU produce groundbreaking research, email tac0.
samedi@disinfo.PRAGMATISM.net
I think they probably either sent less than an actual 1.2tb and it took a lot less than a second, or they just had a few kb of data stored in some disgustingly fast cache and sent the same thing millions of times.
If you don't find it useful, then I hope you will stay with your 28.8 modem and let the rest of us use up the available bandwidth in the future.
The data probably never "lived" anywhere at all. My bet is that they used some hardware on the send size to generate a semirandom pattern, and some other hardware on the receive side to verify that the pattern was received. This approach is common in high-speed work.
Higher bandwidth is great news, but don't think it's going to do anyone but telcos any good. Over the long haul everyone's still bound by the speed of light. As bandwidth goes higher while latency remains constant, the "pipe length" gets to be more and more of a pain to manage effectively. Imagine if you can send six million packets before you get your first ACK, and you'll see the tip of the iceberg.
Local (i.e. "within one box") memory-system designers already worry more about latency than bandwidth. Short-range external interconnects are getting that way too; even the best multigigabit interconnect in this space still has a 2 usec end-to-end delay for zero-length packets. Again, the pipes are getting kinda long.
As I said, more bandwidth is cool, but I'd be a lot more excited if someone came up with a way to improve _latency_ by the same factor.
My guess is that it would be cheaper to build bigger back-ends and thinner front-ends. Today's super powered PC is a compensation for bandwidth limitation (see the Intel Pentium III ads.)
More bandwidth seems to support the network computing paridigm rather than the distributed computing one.
On the other hand, isn't the Plan 9 operating system designed to do what you suggest?
(It would be nice if the RSA crackers or scientists could rent out everyone's screensaver running PCs at night, but very few people actually need *more* CPU.)
The point is that we're out of the Mega and Giga range, afterall.
What's after Tera anyway? What are the next couple of prefixes?
I'm still Reeling at the upgrade from 7 level paper tape to 1/4 inch tape!!!
The bandwidth needed for 1 phone call
(uncompressed) is 64k/sec.
1.2tbits = 150 Gig bytes/sec
that's 2,343,750 phone calls at the same time.
allowing 2% of america to concurrently use a single piece of fiber. Now when are these long distance charges going to go down?
1 Tbps has been achieved in the laboratory years ago in the high powered research tanks of Lincoln Labs, Bell Labs, and others.
Unfortunately, routing at this speed is very impractical; all-optical routing is still several years away.
hey buddy,
have a nice day!
Brought to you by the guys that gave you
WebWasher. Well, I guess Siemens really is
a company that I like to call a Y2K company.
Go on, guys!
you could have full scale quake wars with like 1,000+ ppl on those $60,000 machines to crack DEC codes... that'd be cool and you could have a modification that would allow for battle field commanders that could give orders and stuff... it'd kick ass... my 0.02
-Aaron
Actually the baud rate of a V.34bis modem can go as high as 3429 under good line conditions, and this rate is required to achieve 33.6k (~9.7 bits/baud then). 3200 is more typical.
And 56K PCM modems must run at *8000* baud, the underlying phone system sampling rate (using only amplitude modulation in the downstream direction).
I think the old V.22bis 2400bps. modems ran at 600 baud, 4 bits/baud.
Actually, you'd need about a 1TB line to broadcast holographic information!
And it may not be all that far off now that we
have cool things coming out like multi-wavelength
lasers and such. Possibly in our lifetimes
(or say, the next 50 years or so).
A writer's credibility is directly related to the care in which the trivial things are checked for exactitude.
In other words, /. ranks quite high on the bogosity scale.
Fucking faster than FireWire, too
Take a look at this. Fujitsu pushed 1.1 Tbits through 150km of fiber, almost twice as far as Siemens, in Feb 96. The problem with this is that pushing that much data through a fiber in the lab is a very different proposition to pushing it under the Atlantic. Different wavelengths travel through glass at different speeds (which is why you get a spectrum out of a prism), and as soon as you start pumping data into a laser it starts emitting slightly different wavelengths because that is what modulation does. The upshot of this is that the nice clean pulses emitted by the laser are smeared out by the fiber. The real figure of merit for an optical link is the product of the speed and the distance. By this measure Fujitsu were almost twice as good back in 96.
Try dsitributed.net. (http://www.distributed.net). Thez are using your desktop pc as part of a BIG "cluster". about 10k computers...
Correct! I did some research on these Erbium amplifiers during my undergrad work, and here's the skinny: It turns out that the most efficient wavelength in fiber optics can be reproduced by a certain energy level delta in erbium (since its higher atomic number provides many deltas to work with). What they do is excite the erbium atomes with a laser. The fiber is looped along the doped section of fiber--bent fiber=loss of signal. As the signal is lost, it collides, in phase, with all the excited Erbium atons, which all release this effifcent wavelength. This method provides an amplification on the order of 40dB, which is immense. It also vastly cleans up any bandwidth spreading that would be present.
Interestingly enough, it sounds like this multiplexing method, while drastically increasing bandwidth, may make this elegant method unusable. Different wavelengths would need different energy levels, all of which probably could not be produced by erbium. I would be interested in seeing how they get around this, if they can. IF they actually have to go to an electric amp, they will probably loose most of the bandwidth they are trying to create! I suppose they could dope the fiber with multiple atom types to simultanously amplify all bandwiths. However, the entire fiber would need to be amplified at a rate consistant with the most inefficient wavelength in the signal, making the entire process more expensive.
Of course, you'll need something a bit faster than PCI to keep up with that.. :)
Ahem.. .. That's " pr0n " to you.
They probabally aren't using a drive at all. They've probabally just designed some program that sends out a specific stream of bits (maybe incrementing numbers) and another end that reads them and then forgets them. A HD would just slow down the test, besides you'd need a Solid State disk with Fibre just to keep up :)
I read the internet for the articles.
I don't know about 100BaseT, but I KNOW your garden variety Pentium II can't fill a Gigabit Ethernet. Heck, an Ultrasparc or a MIPS R10k can only fill an Gigabit to about 50% before topping out. In fact on the large machines were you see Gigabit installed, you generally find a processor devoted to handling the gigabit.
I read the internet for the articles.
Not quite. This works for a while, but you will always reach a limitation in the underlying media. Copper's limit was very low by today's stanrards (although I can tell you that 28.8 was pretty damned pie-in-the-sky astonishing when most of us had 300, 1200, or 2400 bauders!)(and we went to I believe double the previously accepted theoretical upper limit anyways, but still there was a limit). Optical's limit will be a result of imperfections in the fiber causing signal degradation at ultra-fine tunings. Boy, doesn't that sound exactly like the problem with copper? Well, it should.
It's absolute basic signal transmission theory here. As someone else said, when you get right down to it, eventually you always come back to the basics.
Fiber is limitless bandwidth only so far as, to paraphrase badly, it is sufficiently advanced to look like magic. Once it becomes commonplace, we'll hit the limit. Call that the first law of bandwidth and write a book about it :->
A few off the top of my head:
Aw, heck, why am I even trying?!? Today's systems are so incredibly bandwidth-constrained it would be a pleasant breath of fresh air to have to worry about something besides how many bits can physically be fit into the pipe for once!
Posted by tdibble:
... faster than light transmission ... hmmmmm ... physics be damned! :->
Now, if we could create an Alcubierre warp drive, or even an ordinary wormhole, run this fiber through *that*
Posted by Lord Kano-The Gangster Of Love:
Fingle fiber bandwidth may not be limitless, but the fact that the data may be sent along MULTIPLE optical fibers makes the potential bandwidth limitless.
1.2 THz on a single strand. How about 100 strands? 1.2 PHz (petahertz)? How about 1000 strands?
Many of us will probably live to see EHz, either in network or CPU speeds.
Through a conduit the size of a pepsi can you could have more bandwidth than all of the networks currently in the world.
LK
I haven't read the article itself yet, but I'm almost positive it uses some form of WDM (Wavelength division multiplexing). So it's not a single 1.2 tbps channel, it's many slower channels, all on one fiber. Total is 1 tb/s. I know Lucent has what is essentially an optical router on a chip that is used for splitting something like 20 channels from a single fiber.
retrorocket.o not found, launch anyway?
kilo 10^3
mega 10^6
giga 10^9
tera 10^12
peta 10^15
exa 10^18
zetta 10^21
yotta 10^24
-- Too lazy to get a lower UID.
Unfortunatly, that is true. Still, it's much cheaper than burying new fibre.
Somewhat off topic, I wonder how much bandwidth is being wasted now either in the voice networks or in data networks that could stand a hardware upgrade?
It's easy to acheive mega bandwidth. Achieving it is a bit more difficult.
Of course, the bottleneck would then be loading
the files off of the server's hard disk, so
unless you've got a really slow hard disk, it
still wouldn't be faster.
So now from what I understand they split the fiber virtually into 60 channels... as tech becomes better they'll be able to split into more and more channels and the receivers will be able to correctly differentiate between these channels... Similar to how modern modems operate... (i.e. the better you can synthesize and detect different phase and amplitudes in a medium the more dense your constellation patterns become and therefore the more bits per second you can shove through it)
:-)
Interesting how everything always comes back down to the basics...
Whatever. Most people won't see this stuff for real for ages. Though I happen to know that SGI are investigating using fibre instead of PCB for ludicrous speed main memory connections - for high end SMP machines of course. Apparantly they have stuff running in the lab, running at several 100 GBytes/sec. Most of todays PCs have 0.8GByte/sec main memory.
Fiber does have a specific bandwidth limit - if we assume that blue (4000 Angstrom) light is the highest frequency the fiber can carry with acceptable loss, the total bandwidth of the fiber works out to about 7.5e14 Hz. In practice, this will limit the data rate to somewhere on the order of 2e14 bits per second, which while a lot is only about a hundred times the rate posted in the story.
Further advances in optical fiber technology may push the data rate up to 1e15 bits per second, and on-the-fly compression will help get even more out of them.
-dentin
Alter Aeon Multiclass MUD - http://www.alteraeon.com
In any case, given the resource hungry nature of today's applications, I'm sure we'll smack up against the bandwidth limit of fiber RSN.
The future of Microsoft Office... One copy located on a microsoft server being shared out to anyone on the internet with a license.
Unfortunately, the 1.2 tb/s connection filled solid within minutes of being hooked up. Further research found that all the engineers at Siemens were trying to use it to access Slashdot.
sPh
Well, let's see, multiplexing is time division, and we can assume digital vs. analog...
In other words, it's doing pretty much what you'd expect it to?
Dewey, what part of this looks like authorities should be involved?
Nothing we have just now.
However it is "just" a bunch of 20Gbit/sec links we need to fill, so "all" we need is something to make use of 20Gb/sec, and to buy a whole buttload of them.
Let's see, I think Juniper's current product is (see http://www.juniper.net/products/m4 0-brochure.htm) capable of 2*8*2.5Gb/sec, or 20Gb/sec as a theoritical max. So in thery you could use a few racks of the highest capacity/highest density routers to drive one of these monsters. In practice I expect it would take at least another spin of Juniper's hardware to do it, but in realiaty they have time for another spin or three before this stuff is likely to be for sale anyway.
I guess we have just solved the "what can we build the backbone out of to support upgrading all the current modem connections to DSL" question...
It isn't 2:30 yet, even in the eastern time zone. Where are you posting from?
How about using it for a true merging of voice, data and video? I'ld love to fire up my computer and have it deliver me whatever movie I want a the moment I want it and feed it off to my TV.
** Martin
Unless, of course, you replace the fiber with a tube made of MIT's new "perfect reflector" material. Which is, unfortunately, even more involved.
Kythe
(Remove "x"'s from
Kythe
It doesn't work this way. Fibers have different transmission characteristics for different frequencies, and increasing modulation rates (barring clever encoding schemes) increases the maximum frequencies of the sidebands. Eventually, the frequencies become high enough that they begin to be attenuated, and data is lost. For fiber, 'though, the limit is "pretty damn high" (as someone else said here). I've heard estimites of the theoretical maximums on typical fiber ranging from 25 Tbps on up. MIT recently developed a "perfectly reflecting mirror" that could be spun into tubes, i.e. a replacement for fiber that wouldn't need repeaters, etc. I'd like to know what the bandwidth would be on such systems.
Kythe
(Remove "x"'s from
Kythe
This is really cool. Now if we can just improve memory access times, life will be wonderful.
Kythe
(Remove "x"'s from
Kythe
I'd love to have a terabit pipe running into my home... now I just need a terabit interface for my brain. Yay!
/Andrew
Yeah, but /. isn't out there, it's in here.
More bandwidth wouldn't make a world-wide cluster possible - the killer with a big cluster is the latency, which increasing the bandwidth doesn't help much with.
Check out the globus project, who are actually trying to build something like this
www.globus.org
-Erik
A week or two ago I posted an estimate on this based on signal processing; the ultimate limit for all techniques using visible light is on the order of 1.0e15-1.0e17 bps, which leaves plenty of breathing room.
In practice, the optical properties of the fiber will impose a more strict limit. Another person has posted an estimate in this thread (2.0e14 bps and up, IIRC).
For a more detailed description of where my estimate comes from, read through the posts on the "chaotic laser" thread (or select "User Info" above).
The theoretical upper limit to data transmission using visible light can be estimated by considering the properties of the visible light beam that is carrying the signal. Treat the beam as a stream of photons. We'll call the "amplitude" of the modulated signal in any time slice the number of photons that arrive in that time slice. Due to the nature of light, the shortest timeslice that it is meaningful to define is the time required for the light to propagate one wavelength. Picking 600 nm for simplicity of calculation, that gives 5.0e14 time slices (and hence samples) per second.
Now, we have to figure out how many amplitude levels are available to us in each sample. The short answer is that we can stuff in as many as we want, but at an ever-increasing power cost. The measurement of the number of photons in a given sample isn't perfect. Even under the best conditions possible, the error will be roughly on the order of the square root of the number of photons transmitted. So, in order to get n data levels, we'll need about n squared photons per sample. The energy of each photon is equal to Planck's constant times the frequency of the photon, or about 3.3e-19 J. As we need 2^n levels to transmit n bits of information, the energy required per sample is (in the worst case) 3.3e-19 * 2^(2n).
Let's say that we want no more than about 10 watts of power dissipated in the worst case. This gives us 2.0e-14 J/sample, which means that 2^(2n) must be equal to about 60600. For simplicity, we'll bump the power up slightly and call this 65536 (2^16). This gives n=8. So, at something like 11 watts, the maximum data rate that can be achieved using a visible light carrier is somewhere in the realm of 4.0e15 bps.
You can get higher bandwidth by increasing the power, but this gets very ugly very quickly. Therefore claims of anything greater than this over a single fiber or single laser beam should be taken with a very large grain of salt.
In practice, this is not what limits the maximum data rate over fiber. As you modulate a carrier, you spread out its frequency spectrum. This means that your 600 nm laser beam, after being chopped up into sample elements and modulated, winds up not being purely 600 nm any more. For relatively low data rates, this isn't much of a problem. However, when the frequency of modulation approaches that of the frequency of the carrier itself, it starts becoming significant. An optical fiber, like any other optical medium, transmits different wavelengths at different speeds. This causes signals that are time-domain modulated to smear out, limiting the data rate that can be used. Similarly, a fiber's transmitting properties only apply over a certain frequency range. No matter what the modulation method used, the optical properties of the fiber will place limits on what can be reliably transmitted. Further, signal boosting for transmission over long distances is performed by feeding the signal into an erbium-doped fiber configured to act as a laser. This will have an even narrower range of operating frequencies than the fiber itself has.
I am not an expert on the optical properties of fibers or on erbium-doped fiber lasers. People with more knowledge re. this than myself have posted on slashdot already, and have given estimates in the range of 1.0e11 and up. However, the fundamental limits to optical data transmission remain very high, as illustrated above.
This is called "frequency domain multiplexing" and has been used for years with analog transmission. Some schemes of fiber transmission use it too.
However, it doesn't matter whether you transmit at a low data rate on several frequencies or at a high data rate on one frequency, because the physical effect is the same. When you modulate data on to a carrier, you blur out the carrier's frequency spectrum. The amount by which the carrier spreads out is directly related to the bandwidth/sampling rate of the data being modulated on to it. If you have a beam of light at, say, 600 nm (frequency 5.0e14 Hz), and modulate data on to it at 100 THz (1.0e14 Hz), your resulting beam will actually have its spectrum spread from (roughly) 4.0e14 Hz to (roughly) 6.0e14 Hz (about 500 nm to 750 nm.
So, in summary, you _do_ use a range of frequencies even when you are doing time-domain multiplexing on a single-frequency carrier.
No. Any wavelength of light is possible. Energy is quantized, not wavelength. Therefore, if I have a photon of 632 nm light, it's energy is given by E = hv, where h is Plank's constant, and v is its frequency (c/632nm). I can still have a photon with wavelength 632.0000001 nm.
How are you going to produce your arbitrary photons, though? Photons emitted from collapsing electrons will only come out at fixed wavelengths, determined by the electron energies. And, my understanding of lasers is that all the light from one is produced by the same compound, and by the same electron transition by that compound. So, you're not going to be able to pick any aribtrary wavelength, because you probably won't be able to find just the right compound and be able to excite it perfectly to produce your desired wavelength.
Of course, I grew to hate physics in college, so go ahead, everyone, and point out just how I'm completely wrong and stupid on all this. I won't mind a bit. :-)
I want.
Celebrate the finer things in life
Quite frankly, I'm extremely disappointed to see the plain lack of ingenuity in the entire computer industry.
You've got a cable capable of sending a whole spectrum of light, so why wouldnt you divide it up into the different colors? The fact that dividing it up into different areas of the spectrum is a new idea and hasnt been utilized for years now almost disgusts me. It seems almost common logic for this to be the next logical step. I honestly expected technology to utilize potentials like this. Do modems do the same, utilize only on or off pulses or do they take advantage of the possiblity of changing amplitude and frequency to allow for potential increase?
Myren
It's Siemens, not Siemans.
Tera not Mega! What is this, the 80s? C'mon!
My only question is, what in the heck were they feeding this connection with? That's a bunch of data to either read or generate in one second. Their test system must have a stupidly fast hard drive. :)
--jwriney
John Riney III
jwriney@awod.com
Siemans is now Oce, but they are still a cool company.
They make great giant laser printers. I worked on a couple in my Computer Operator days. We had a couple old IBMs we got rid of in favor of another Siemans and had very little problems. The IBM were mich higher maintenance (chuckle chuckle).
So this means fiber lines that already exists can be terabitized just by switching routers on both ends (once they exist)
:)
Cool
You wouldn't use this thing for one machine. You would have a dedicated box at each end of the line to divide it into many, many DSL speed channels, or a very good number of gigabit connections. Even still, a 1000 gigabit channels would be great to have. A normal machine these days can handle gigabit ethernet, provided you have a gigabit ethernet card. Luckily, all even slightly newish or even a bit old Macs have built in gigabit ethernet. My 180 MHz 604e PPC Mac has gigabit ethernet built in, and it's more than a year old!
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NTT (http://www.ntt.co.jp) had about the same demonstration in 1995 (! - search wired.com-archives for 'soliton'): 1 TBit with 10 GBit-sources x 10TDM x 10WDM, but they also claim to have these lines in the market this year (see c't-Magazin i. 1/98 p. 64). And, yes, together with optical routers, switches and the other stuff.
To have something working in the labs does not necessarily mean, you can deliver a fair implementation that is useful to your customers.
But I do not believe it is really true, before I see it on their list of offers. Even NTT is better in announcing than implementing.
And by the way: a Terabit per second even exceeds memory-Bandwith (RAM) by at least some degrees of magnitude!
and I don't mean the 80k reach...
What's the most home users get right now? cable, ADSL, etc. they are cheap, but they are also shared bandwidth (local loop or at the central office). There are some other access methods, like ATM, but they are not widely used (i think in New Brunswick, canada, eh!)
For a guarantied bandwidth, business pays big bucks! $800/mo for a T1 $2k/mo for a T3 (~50M), don't know for a SONET OC3 (155M) or OC12 (620M) but only the very big companies can afford/justify leasing that type of bandwidth...
I'll be happy when hook up a T3/DS3 to my basement gateway/firewall (or when i can afford one)
A truth that's told with bad intent, Beats all the lies you can invent. -- William Blake
I'd love to have that kind of speed, but I must agree...to do what with? What kind of redicilous storage system will be used to store say..the data collected if this link was running at full speed for 24 hours?
Maybe there will be uses for long distance transfers..ie. with use of some multiplexing, but otherwise I cannot think off what it could be used for in the private/small business sector.
When in doubt...GUESS!
check out www.silkroadcorp.com. they have built an external optical modulator to increase the bandwidth. then, by multiplexing oc-48's together, they have demonstrated 200Gb/s over 200 miles and boast figures in the 10Tb/s range.
Just to let you know, 2.5 Gbps is easily achievable currently, 10 Gbps is a little more difficult but do-able. By the time you get to 20 or 40 Gbps dispersion is pretty bad and you run into other attenuation problems, that's why it's best to break the stream up into multiple wavelengths.
Also, current commercially available capacity on a fibre is about 320 Gbps, 32 x 10 Gbps.
Cheers
>:]
I'm in the east, why? Is 2:30 too early for stories?
PDG--"I don't like the Prozac, the Prozac likes me"
"Where is my mind?"
Imagine the routers!