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Using Visible Light for Data Transfer
James Evans writes "Wired has an article about a New Zealand company which has developed a technology to transmit data at speeds up to 400Mbps up to 4km. They are working to have it more resistant to changes in weather, as well as increasing the distance. It has a number of advantages, including lack of federal regulation of the spectrum, as it is of course, visible light."
In related terrestrial networking news, waytoomuchcoffee writes "Science Blog reports that the backbone for the World's Fastest Network is up and running. It's a fiber optic 40 gigabit per second connection between Chicago and LA. Teragrid is a project by the National Science Foundation designed to link up supercomputer centers."
How long do you suppose the lack of federal regulation will last?
So, I guess we can finally have mirrors that are mirrors? Excellent!!!
"We are accountable for not only what we do, but also that which we don't do." -- Moliere
Some places do have ordinances against light pollution. I wonder how this would fit in. Also, will it come with a warning, such as "Do not look at transmitter with remaining good eye"?
Donate background CPU time to fight cancer.
they better be careful at 400mbps, they may break the switch on their flashlight.
http://hksoul.myftp.org/
Packet loss due to snow storm?
LAck of regulation is nice, but is there really a lot of regulation for InfraRed and UltraViolet?
It sounds like a VERY nice system for short-range, non-critical communictaions, but personally, I can't think of any points I would want to communicate to where I have line-of-sight... If I could get an inexpensive device that could communicate for about 10 miles, I would certainly get several.
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Doesn't this just sound like fiber optics without the fiber?
I seem to remember this being done a long time ago. I've got an electronics book with a schematic for a serial 28k transmitter using visible light.
--Quentin
The LED-color should be chosen according to the content transferred... users sharing pr0n via P2P could build their own red-light-destrict! --- I wonder if powerful LEDs will attract insects and such - the connection speed could be reduced drastically by bugs.
We have been streaming voice data over fiber-optic lines for a while now, and even digital data signals for networking. This sounds like fiber-optic transmission without the actual fiber-optic line! Very cool, indeed.
Perhaps this is the future of truly wireless computing?
One thing the article states is that the current range is about 11 km. This seems a little short. However, considering this is a line-of-sight type of thing, that does make sense. Give 'em time, and they'll get it down to hundres of miles with good reliability, and then I think we'd see a bit move towards it for WAN technology and business usage.
Be excellent to each other. And... PARTY ON, DUDES!
I was thinking that we'll have really fast semaphore flags next.
The problem is really tired arms.
If moderation could change anything, it would be illegal.
Except with morse code, I believe, you have to find the right frequency. Not much of a problem, but likely harder to find than a little light strobing across the street. Then there's the rather obvious quote from the article
On the other hand, bad weather, or anything that might block the light's path, can cause slowdowns or power failures.
"File transfer failed: Code 75(flock of seagulls)"
*honk*
This is my sig. It's prescription, I swear. I need it for reading things... on the other side of things
Sounds like a cool technology clean, high performant, low infrastructure, does not slice limbs off or create two headed babies. This should make it a very attractive sell to commerce and to the public
I would have some security concerns though since it makes it a lot easier for those of malicious intent to intercept the signal as its basically being broadcast in the open. The technology would seem to lend itself naturally to strong encryption though.
I think they could be onto something big here.
Do not try to read the dupe, thats impossible. Instead, only try to realize the truth
What truth?
There is no dupe
So much to do, so little bandwidth.
--
Try Mozilla
...using nothing more than a prism.
They wouldn't even know you where there!
Fixed wireless communications based on lasers are already available commercially, and have been for a number of years. Do some searching on Google.
Security?
That was the first thing that occured to me when I read the post. It will probably be like everything else. First comes the technology, then years later everyone slaps themselves on the forhead for not thinking of making it secure from the beginning. Like Telnet, FTP, POP, 802.11, IM's, etc.....
Doing Free Space Optics isn't new. It's been done for many years now, although primarily with laser-based systems.
I work for a company that is currently developing a LED-based FSO system -- Omnilux.
The big push now in the FSO market is to find the right balance between performance and cost. Too many companies were trying too hard to push data longer distance, then faster, costs be damned.
FYI, visible light is roughly 400 to 700 terahertz.
Consider this, most cellphones around the world operate at 1500MHZ and so have a seemingly impressive maximum THEORECTICAL data transfer rate of 750Mbits/sec. Unfortunately due to physical contraints on modulation systems a good rule of thumb is that the actual data rate provided is about 1/2000 of this and so we end up with around 375 Kbits/sec that is just coming out with 3G systems.
You should really read up on communications theory, especially the basic stuff done by Shannon, Nyqvist and all the others.
The theoretical limit for a digital signal modulated in a perfect noiseless analog channel is infinity for any frequency! Where you get your numbers from I have no idea but they are totally incorrect!
And if you hava a noisy channel the theoretical maximum is dependent on the bandwidth and the noise, nothing else. And just because a signal hase a basefrequency of 1.5 GHz doesn't mean that it has a bandwidth of 1.5 GHz. Go check, all mobile phones have a much, much smaller bandwidth. We are talking orders of magnitude here.
I don't think a video camera would achive much, unless you have a video camera that can record over 400 million fps.
reminds me of a slashdot story a while back about a group of people that was able to get your data transfer by looking at your (external) modem's LED.
I mean, same thing except, well, faster...
The cool part, though, is that now the router's status LEDs are actually good for something. You can theoretically face two routers toward eachother and that's IT! done! until some idiot walks between them. ha!
but really though, The thing with radio we seem to not be able to do with light yet is frequency modulation. If we can do that, I think we can push some very serious bandwidth through this spectrum.
The data-hiding possibilities are immense. you can technically send humongous amouts of data through a TV set, even, if it was made of as many LEDs as there are pixels, and by varying the each LED just ever-so-slighly. You can be watching the TV for pictures, and your Aibo would be sitting beside you, downloading zillions of bytes of data, and gaining consciousness (sorry just watched the animatrix, heh).
My life in the land of the rising sun.
But after reading the article, and seeing how they'd use LEDs (they don't say how big though), and the bandwidths involved, the lights would seem to be constanly on, do you think?
That'd mean no real lightwave pollution (it's all line-of-sight) and little visual pollution or distractions due to thousands of flashing lights?
Of course, I still have to wonder about the effects of different weather. I see it'll still work with a hand moving in front of it, but what about heavy smog days, or blizzards? Would torrential rain make problems with light refraction??
I guess it beats training swallows to carry coconuts engraved with data packets from rooftop to rooftop (they could grip 'em by the 'usks)
Hats off to the Kiwis for this one though, it sounds pretty exciting :)
Woohoo! I can't wait to see my IT Manager scaling our office building to deal with pigeons nesting on the transmitter!
"Nature will find a way..."
It could be as secure as wi-fi where the actual "media" is free for anyone to grap. What this means is that it requires strong crypto to be secure.
;)
I think the realiability is bigger issue. What if someone wants to cut your operations. Big piece of carton or huge van to front of emitter could quite efectively cut it. How's that for denial of service
Well, i admit that i havent read the article so i dont know how it actually operates but what about "light noise" from other sources.. Or other co-existing "light hubs" in the area. How do they effect the data and its reliability. Only way to prevent this (which i can think off) is using laser as transport medium light and thats not so new anymore is it. And DoS'n laser is even more simpler since the lightbean is really narrow usually and doesnt spread as "normal light".
yush
Great, I won't have to buy more crappy pringles in order to steal credit card numbers.. I already own a mirror..
A very important point is that Infra Red light is absorbed by the cornia (outside) of the eye and dosnt penatrate to the retina where it can cause real damage. Visable light does penetrate (obviously) to the retina and WILL fuck your eyes up. I've worked with IR lasers for a few years, they are much safer than visable light devices.
Also saying use of visable light avoids licencing isues is a bit misleading.
As to my knowlage, no country regulates visable, IR or even UV unless in lasers (or other sources) where they may get to the powers likey to cause physical danger (not very relavent here, less so with IR rather than visable light).
Put your hand up if you need a licence for your IR TV remote controal!
Anyway, a practical solution would be to use lasers of differnet wavelengths and swich to the correct one depending on weatehr conditions. EG fog attenuates some wavlengths strongly, rain scatters a differnt set of wavelengths more readily, etc (As a crude example, consider the different wavelenghs reaching your eyes from the sun in these different weather conditions)
This technique of swithing to the most aproprate wavelength for the conditions is used in army laser range finders.
Anyone quoted by a reporter knows how little they understand
Don't believe what you read is the truth.
It I am not sure how this is article bestows very interesting or novel information. Granted, the article mentions the wavelengths used are "visible", and "red". My guess is that they are emitting somewhere between 600 and 800 nm (typical visibly range is from 400 nm (purpleish) to 700 nm (red) however this is not a strict cut off, and if bright enough, even above 830 nm is visiblish).
Most telecom takes place at about 1550 nm, well into the infrared, but this is primarily because the typical fiber has nice properties in this range (absorption and dispersion). Therefore I am not sure there is much fundamental difference between infrared light telecom and visible telecom. Indeed they use very similar laser material (GaAs-based or InP-based diodes), are modulated the same way, etc.
Possibly this is neat because it is free-space optical stuff. However this (as pointed out previously) is not new. There are companies that are in place as we speek. Maybe deregulation may be of interest, but if the light it kept at the same wavelength as in fiber, then there is no need for an electronic klugey transceiver (detect the light in the fiber at 1550nm and drive a laser to re-emit the same signal at 6xx nm). Instead, an add-drop filter could be slapped on to the end, pick off the right wavelength, and feed that to a fiber which could be collimated as the source. This collimated beam then could travel over kilometers with no trouble. An all optical solution has a much
just a thought
Free air optical networking isn't really a new idea. Infrared units are pretty common. I'm not sure what supposed advantage using visible light has over infrared... IR isn't regulated (at least in the US, I can't imagine that it would be anywhere).
I investigated this for networking a couple of buildings my company had near together. Pretty cool stuff. You could get a gigabit connection over a few km of thin air. Cheaper units did 155Mb and for dirt cheap you could get 10Mb. Short range units used LEDs. Longer range ones used lasers.
I've been wondering why consumer ISP's haven't taken to this yet. It's a great last mile solution.
--Keepiru
--slashsuckATvegaDOTfurDOTcom
So what if they operate at 1500MHz? It is the bandwidth that is important. Example: Radio stations operate at 90-110MHz range. But each one has a bandwidth of around 30Khz.
So, first of all, the cellphones have a bandwidth allocated within a frequency range around 1.5Ghz. Let's take GSM, which is the most widely used standard:
In case you don't understand, it is simple. If you have a single signal at 1.5Ghz frequency, you could get a data rate equalling half the frequency. However when you transmit data you basically cause side-frequencies to appear in your spectrum. Do not assume that just because the system transmits at the base frequency of 1.5Ghz that the signal spectrum will be just a point at 1.5Ghz and 0 everywhere else. The spectrum will spread. If you use up all your possible bandwidth the spectrum will take up all the frequencies from 0 to 1.5Ghz.
Furthermore, consider the fact that there are many cellphones, sharing infrastructure. The protocol does both time-division and frequency-division multiplexing. While a *single* cellphone could perhaps work with a station at .75Gbit, this ceases to be the case when you add a few thousand cellphones. The band is subdivided to a pre-specified number of sub-bands - not only that, but there is also some time-division multiplexing going on, with each cellphone only doing rx/tx at a fraction of the total time.
Of course, the same is true for all electromagnetic wave devices.
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Imagine that you might be able to upgrade a set of traffic lights to actually make something faster!
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I just read about this the other day in the book "Dealers of Lightning" (page 140). While they were developing the laser printer in the 70's, some of the researchers had to move to a different building 1KM away. They had line of sight between the two locations, so they rigged up a system of lasers and photodetectors to bridge their network between the two buildings.
The beam went over a public highway, and after one woman went into a ditch after it startled her one foggy morning, they coarsened the beam to make it invisible.
Why is everyone acting like this is a new thing? Hams have been doing the same thing for years. There have been construction articles in popular electronics mags for years about going digital with a pair of LEDs.
-- Ed Carp, N7EKG erc@pobox.com PGP KeyID: 0x0BD32C9B What I'm up to: http://intuitives.mine.nu
I'm not too clear on how this works. Wouldn't it be quite easy to disrupt a beam of light, through physical or other means? Seems you could put a piece of aluminum foil in it's path or disrupt the beam with other beams quite easily. And what about safety issues? Is it visible to drivers? I remember reading that when PARC first had a line of sight laser to connect two buildings across a highway, during inclement weather drivers would crash while distracted. If it's too high, would have to worry about aircraft. And since a laser can damage your eyes, wonder if this type of light can as well.
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They tried it in a conference. They wanted to telecast conference proceedings in a building some distance away using this method. They set up this equipment, tested everything the night before the opening day, works perfectly.
First day of conference. No signal. The receiver didn't see the transmitter at all. Total flop.
So they checked it thoroughly again that night. Everything was still working fine.
Next morning: same story. No signal.
This repeated on all 3 days of the conference.
Organizers were left scratching their heads. Funny part is, it worked at night and failed at day without their touching anything. Sabotage? The devil??
Later they found it was because the light beam was getting bent in daytime due the temperature gradient (same way that mirages occur). Poof.
Of course, these are just problems that will inevitably occur when a technology is in its nascent phase, I'm sure it'll get ironed out as it goes commercial.
The article talks about rain and fog, but is silent on the sunlight issue.
We set up a microwave link between two buildings several miles apart. We had to get a right of way from all the land owners inbetween.
I wasn't involved directly in that project, so I don't know if it was needed because it was microwaves, or just in general.
I wouldn't rush to think this is some sort of easy method to solve problems, though.
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Visible light huh? Like... I can see it? Hmmmmm. Hope someone thinks to encrypt it :)
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Not exactly, if you (theoretically) modulate a 1.5 gig signal with a signal at half that frequency, two sidebands appear in this case from 0.75 gig to 2.25 gig is the resulting signal spread. So if you use all your possible bandwidth (and again this is theoretical, I know of no system that 'coud' do this) then a bandwidth of 0-3gig will result. Interestingly, in this scenario (ie FM or AM modulation) the bandwidth consumed is double what the maximum modulating frequency is. So one sideband is 'wasted' as it carries a mirror of the others information. Also the carrier frequency itself is redundant, it carries no useful information. Given these facts, Single Side Band (SSB) is much more efficient in terms of bandwidth & power required (power saved in the transmission of carrier & one sideband can be used to increase the remaining sideband)
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I don't imagine using this thing for sending a very important document/work. It looks more like a cheapest way to do fast networking. It's LIGHT. A flying duck cross over the lightbeam and BANG! :) This appart from other problems like insecurity (I mean, I think it's easier to do a light-receiver than a radio-receiver... more people would be able to 'investigate'), etc.
:D
Neighborhood network? perhaps. Just imagine a lanparty on my neighborhood, and every tv/vhs/dvd/thing-with-a-infrared-remote-control getting weird
drmad.
drmad
this technology has been available for decades, it's called free space optical datacom. As the link points out, there's even a google directory listing for providers of this technology.
there are significant limitations on this tech however. cheif among them is reliability in various weather conditions. rain, fog, snow, and passing birds tend to cause havok with a laser beam. setting a laser up to point to a target 1 or 2 kilometers away is no small feat, and even harder is making sure it stays on target months and years later.
there's a reason why most wireless shorthaul links use microwaves, as the laser technology really doesn't work very well.
A lot of infrared (IR) lasers (common examples are Nd:YAG or Ti:sapphire) operate in the near infrared
Yep, you are right. Some near IR wavelengths will be let through the cornea, and you wont have the blink reflex to protect your eye. However, this is slightly misleeding as the vast majority of IR (at wavelenghts a little further from the visable) is safe. Especially at the power levels discussed here.
The only time it decomes dangerous is when the IR light is strong enough to heat the cornea!
For example, at 1.55 microns (wavelength most suited to optical fibre) the British Standard guidelines state the maximum permisable exposure to the eye at this wavelength is the same as skin. In simple laymans terms, it has to be strong enough to burn flesh (skin or eye) before it will damage the eye!
Of couse, the real bastard lasers are UV. A fairly dangerous wavelength (suntan anyone) that you cant see. Not good for your eyes either!
Anyone quoted by a reporter knows how little they understand
Don't believe what you read is the truth.
Check out http://www.plaintree.com - they use eye safe LEDs for transmission, with speeds up to 155 MBPS, or T1/E1 at ranges to 3KM. They are using this at the Ottawa airport. They have been in business since 1988.
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UV lasers can be bad, but they don't do retinal damage at short enough wavelengths. In fact, UV is used in "Laser Vision Correction", because it ablates the cornea nicely without penetrating at all into the retina.
For really severe retinal damage, visible and near IR are the worst.
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It's a fiber optic 40 gigabit per second connection between Chicago and LA.
Get your bits
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Layer 1 security (physical access denial) is not good security. The best way to secure networks is to use secure protocols - wrap everything up in SSL.
As for the service interruption concern, it would seem prudent to use several redundant beams spaced at irregular vertical and horizontal intervals - wide enough so that a small flock of pigeons doesn't interrupt service.
Since the laser's light is coherent, you can use this interference to reconstruct subtle changes in the distance from the laser to the reflective surface. In other words, you can eavesdrop on someone by looking at how the windows in the room vibrate! Supposedly this was once used to find out what people were saying in an embassy.
At short distances you can use a grapefruit instead of a window, but talking into a grapefruit is just weird. :)
I was driving to work North on Willows Rd in Redmond, WA today and I saw Terabeam's laser flashing away. It is pointed almost directly along the road to their satellite building to the South.
I haven't noticed it before, so I wondered if they had some beam dispersement issues. I got a little concerned that the laser was damaging my eyes. Hopefully the power on the lazer diode is turned down. You never know what is going on in development hardware ;)
The light looks like your run of the mill strobe light. The pattern looks like the LEDs on your hub. Not sure why because that flash speed is not consistent with the marketing info on www.terabeam.com.
Unfortunately the fog here in the valley tends to prohibit their use of the system.
Holland
How long do you suppose the lack of federal regulation will last?
I don't know about the US. (The FCC has been moving to open, rather than close, bands for some time now.) But it's already banned in Britain.
You probably already know that radio broadcasting in Britain is (or was a few years back - just in case they've changed their mind) a government monopoly. People tried to work around that in various ways.
One of them was a company that did a cute hack: They shined an infrared laser straight up, and modulated it with an entire FM band full of radio stations (similar to the way you can put a private FM band on a cable TV wire). Anybody who wanted to could mount a photocell or infrared-sensing diode (in a little telescope) on their window sill, point it at the invisible pillar of light, and couple it to a radio to receive the new band. Business model was to rent the stations out as commercial broadcast stations with all of London as target market.
The agency in charge of the British radio monopoly (British Post Office?) complained. And parlement extended the top end of their jurisdiction from whatever the previous legal end of the microwave spectrum was to infinity.
So in Britain, if it's electromagnetic energy (even gamma rays) and you can use it to beamcast or broadcast information, you need a license.
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Oh... you mean here?