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"Twisted" OAM Beams Carry 2.5 Terabits Per Second
MrSeb writes "American and Israeli researchers have used twisted, vortex beams to transmit data at 2.5 terabits per second. As far as I can discern, this is the fastest wireless network ever created — by some margin. These twisted signals use orbital angular momentum (OAM) to cram much more data into a single stream, without using more spectrum. In current state-of-the-art transmission protocols (WiFi, LTE, COFDM), we only modulate the spin angular momentum (SAM) of radio waves, not the OAM. If you picture the Earth, SAM is our planet spinning on its axis, while OAM is our movement around the Sun. Basically, the breakthrough here is that researchers have created a wireless network protocol that uses both OAM and SAM. In this case, Alan Willner and fellow researchers from the University of Southern California, NASA's Jet Propulsion Laboratory, and Tel Aviv University, twisted together eight ~300Gbps visible light data streams using OAM. For the networking nerds, Willner's OAM link has a spectral efficiency of 95.7 bits per hertz; LTE maxes out at 16.32 bits/Hz; 802.11n is 2.4 bits/Hz. Digital TV (DVB-T) is just 0.55 bits/Hz. In short, this might just be exactly what our congested wireless spectrum needs."
Holy Crap, where do I sign up!?!? ^_^
I do not like them, SAM I am.
Sadly, there won't be much ways to download stuff, since every little legal thing that can be used to download illegal things is being outlawed (or will soon by SOPA clones).
Nerdy news for your nerdy needs? http://www.soylentnews.org Soylent News is people!
Just what the subject says...
This is very cool, but the current super high bandwidth demonstration is being done with optical light over very short (1 meter) distances.
The article did point to an article from a couple months ago about the first ever OAM transmission; which was done with radio waves. But the antennas used look very directional and there was no mention of bandwidth.
Optical might be useful to further increase the speed of fibers, and highly directional radio might help for satellite broadcast or to compete with microwave relay towers. But requiring highly directional antennas, on both ends, isn't good for mobile wireless.
Hopefully we'll see another story soon where someone figures out how to detect and transmit OAM encoded radio waves from non-directional antennas.
From the article: "fastest wireless network ever created". Since this thing uses lasers and requires line of sight it would perhaps be more relevant to compare to other laser transmission schemes, where the record stands at 26 Tbit/sec
The next task for Willner’s team will be to increase the OAM network’s paltry one-meter transmission distance to something a little more usable.
Yeah 1 meter transmission distances, using visible light, will have limited practical use. Don't get me wrong, it's cool, but like many cool technologies it's "just a few years away" from practical mainstream availability.
Another excuse for the carriers to charge even more for "network upgrades and higher speeds" while still limiting us to 2GB due to "network utilization."
Awesome, I've been saying for years that OAM would win!
(But then again, I always root for the OAM beam!)
Any relationship to http://mobile.slashdot.org/story/12/03/02/1343228/twisted-waves-could-boost-capacity-of-wireless-spectrum ?
http://iopscience.iop.org/1367-2630/14/3/033001/pdf/1367-2630_14_3_033001.pdf
I am still not sure exactly what the physics is here.
So, are the conspiracy theorists gonna come out and claim this as proof that the U.S. and Israel were, in fact, working together to build Stuxnet and Flames?
Cool! I can hit my monthly cap in .0001 seconds!
Cross the streams!
Now i CAN download the entire internet!
Come on drive mfgs.. waiting on you.
Two reasons:
* This is applicable to point-to-point links, not broadcast.
* This involves a structured beam multiple wavelengths in diameter -- infeasibly large at 1-10 GHz frequencies.
So what is it good for? Free-space optical comms! It could also be applied to sub-THz frequencies for increased range, but not to wavelengths as long as are commonly used today. Applications include backhaul for GSM towers and satellite-to-satellite comms.
It's worth noting, however, that free-space optical comms are not particularly bandwidth-constrained, so the incredible spectral efficiency (TFA says 95.7 bits [sic] per hertz) is not as important as it might seem -- you have literally hundreds of terahertz available in the optical window, so when you need more capacity, you can simply add another wavelength to the beam instead of adding orbital structure to the beam.
I'm not hating on this research -- it's ridiculously cool stuff, and far enough from my field I'd be foolish to think I know better -- but I do remain unclear whether this will end up with any definite advantage over existing techniques.
> 95.7 bits per hertz
95.7 bits per cycles per second?
Still trying to resolve whether OAM is more than pattern polarization in a regular antenna. If it is not, then:
1) the spatial region of receiving the differently-polarized "streams" will spread out with distance from the transmitter, and
2) there will be a finite isolation between the different polarization states in a real receiving device, essentially setting up a maximum signal to noise ratio (SNR); this sort of finite isolation between states is likely to exist in any event
With any comms system, you can increase the data throughput without expanding spectral occupancy (bandwidth), but the penalty is to require higher and higher SNR to tell the different symbol states apart (each symbol represents more and more bits as your throughput increases)
But, the experimenters in this case may be waaaaaay more smart/experienced/better looking than me...
...and Dee Snyder has another special message for you.
Spectral efficiency does seem to be measured in bits per herts. At least, Wikipedia says so, so it must be true:
http://en.wikipedia.org/wiki/Spectral_efficiency#Link_spectral_efficiency
Actually I misread, it's bit/s/hertz.
Never cross the beams.
Which actually makes sense, unlike the units in the summary.
Once they commercialize this, it will be found to cause cancerous-like growths in the brain and begin the zombie apocalypse!
Nothing to see here but us trolls...move along...
Interesting, but the hyperbolic comparisons lacking all context obfuscate rather than illuminate. This research will do absolutely nothing to address wireless spectrum congestion and the posters claim of such is based on a lack of understanding of fairly basic communications theory.
Whatever modulation you use bandwidth efficiency is still subject to the Shannon limit. We are already for all practical purposes at the Shannon limit using modern forward error correction coding over an arbitrarily wide range of spectral efficiencies (bits/Hz) using QAM constellations. Most importantly the energy efficiency (bits/W) at the Shannon limit drops as spectral efficiency increases. In other words the current issues with spectral congestion have absolutely nothing to do with limitations in modulation. We are at the Shannon limit already in modern communications protocols and at this point are only trading energy and spectral efficiency as the application dictates. This new research, while very interesting and certainly important for various future applications, has absolutely zero to do with addressing "our congested wireless spectrum".
Good judgement comes from experience
:: Experience comes from bad judgement
:::: Abundance comes from alleviating congestion
:: Congestion comes from delivering abundance.
It's pretty much a theorem in transportation systems that you can't alleviate congestion by boosting capacity until the less direct or desirable routes are destitute.
There should have been a Star Trek episode where high-end subspace polarizers keep disappearing from engineering consoles because the Ferengi have taken on a contract from Monster Cable to supply private Holodeck enthusiasts with the finest detail in nose hair.
Isn't that just one use?
Pirk: Mr Fukov, twist factor 1000. Just pick a direction
Fukov: It doesn't go to 1000....
Spook: It would be logical to avoid the direction we just came from. The station commander would hardly appreciate it.
Pirk: Hmph. Engage...
http://www.youtube.com/watch?v=yPglc3z6r_A
"Intelligence has nothing to do with politics!"
-Londo Mollari
This news has arrived way past the deadline for stories of this nature, which was back on April 1.
Seeing that local asphalt roads are currently ripped up, to be replaced by graded gravel, I'm not sure why you think we aren't bankrupt already.
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6059486 PDF for those with no IEEE access: http://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=2062936&fileOId=2339120 The short version: nothing new here and equivalence to traditional multiple-antenna methods, with same bandwidth limitations; move along.
"Politicians and diapers must be changed often, and for the same reason."
There's no such thing as a distinct OAM quantum number in photons; it's just a linear combination of eigen modes in a multi-mode coordinate system from "pixels" spread out in space and angle to a mixture of modes described by bessel function (or whatever corresponds to an eigenfunction of R cross P in the wave guide). You can't in the end wind up with more eigen modes than you started with in the original multi-mode fiber.
I cringe every time some says OAM has more degrees of freedom. hold onto your wallet
The only value of this is
1) if the OAM modes for some reason do not couple with each other if you bend the fiber. Then they are the eigen modes of a bendable fiber and thus the best way to make use of the multi-mode fiber.
2) it is easier to orthogonally detect the OAM modes then the traditional modes.
But then why not just say that, since that's the important point, not the so-called orbital angular momentum buzz term.
The simple fact of the matter is that it has been show that the elusive particle, the Bugeton, is made up of OAM modes. But only dishonest scientist can detect it.
Some drink at the fountain of knowledge. Others just gargle.
I work in satellite communications, where circular polarization (e.g. LHCP and RHCP) is common, especially in some C-band links. Can someone explain to me how OAM is different from CP? Because it sure sounds like CP to me.
And if they're modulating the data onto the phase, wouldn't that simply be phase shift keying?
I read a short IEEE Spectrum article about this just yesterday, and I'm still puzzled. Tech writers tackling this subject would be well advised to mention CP in their writing and explain how this differs.
One simple rule for its versus it's