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"Twisted" OAM Beams Carry 2.5 Terabits Per Second 142

Posted by samzenpus
from the greased-lightning dept.
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."
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"Twisted" OAM Beams Carry 2.5 Terabits Per Second

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  • Lasers vs wireless (Score:5, Interesting)

    by Anonymous Coward on Monday June 25, 2012 @09:48AM (#40438029)

    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

  • by Shavano (2541114) on Monday June 25, 2012 @10:01AM (#40438167)
    No it's not practical over significant distances. Those different polarization states (that's what they are) are nor mathematically independent so there is a lot of ISI. You can only trade higher throughput for loss of SNR. 95 BPS per Hz is impressive but it can only be done in the most tightly controlled conditions. It will never be done in anything other than point to point links with very strong signal. Moreover, OAM is a buzzword without a clearly defined physical mechanism. EM waves have frequency and polarization and phase. Their "orbital angular momentum" is some combination of these parameters so you can't increase bandwidth over what can be done using some combination of these.
  • by Sentrion (964745) on Monday June 25, 2012 @10:19AM (#40438341)

    Just because you won't have a 2.5 terabit connection for your laptop or cell phone doesn't make this any bit less cool. There are many applications where point-to-point line-of-sight communication is useful. As some have already suggested, this might help boost the speed of fiber optic networks. This could be useful for more secure networks, such as between military aircraft and satellites. Depending on cost, power requirements, and how well the signal propagates through the atmosphere, this could become an alternative to digging trenches and burying cable. Image a network of repeater towers that could increase the speed of communication across cities or even across continents without the hassle of digging trenches or hanging lines on telephone poles.

  • Re:Holy Crap! (Score:5, Interesting)

    by NettiWelho (1147351) on Monday June 25, 2012 @10:44AM (#40438607)

    yet in the U.S. Internet access speeds and costs have remained stagnant.

    lolwut? These are just approximate dates and speeds from memory, so I may be off by a few years but the gist of it is about right:

    25 years ago, I had 300 baud dialup. 20 yeas ago, I had 14.4Kb dialup 15 years ago, I had something like 56Kb dialup 12 years ago, I had 256 Kb DSL 10 years ago, I had 3 Mb cable 5 years ago, I had 6 Mb cable today, I have 15 Mb cable (and some people have stuff like FIOS)

    The details will be different for everyone, but unless you're going to tell me everyone but me was using multiple Mb connections in the 1980's, I'm going to have to call bullshit on that claim. US access speeds have been steadily increasing every since I've been watching them, and they've continued to do so in the last few years. My connection went from 6 to 15 MB just a year or two ago.

    Over here in Finland, just over the past few years my connection speed has gone from 10/1Mb/s to 200/15Mb/s (cable, uncapped) while the price has gone down from 49 euro/month to 14 euro/month. Have the prices dropped similarly in the US?

  • Re:Holy Crap! (Score:5, Interesting)

    by wolrahnaes (632574) <seanNO@SPAMseanharlow.info> on Monday June 25, 2012 @11:41AM (#40439405) Homepage Journal

    That argument would work if places that matched density with European or Asian cities also matched or approached their internet connectivity. They don't, however, not by a long shot.

    Sure, someone living out in Nowhere, Idaho can't expect readily available and inexpensive broadband, but someone living in or around NYC, LA, or DC should. They don't have shit worth comparing either, for the most part. Lucky pockets of population have FTTP services or cable carriers who don't suck, but the vast majority have yet another overpriced Time Warner or guaranteed to be shit DSL.

    If the Europeans can deploy these nice networks in cities that were never built to be friendly to modern infrastructure, why can't we seem to figure it out even in new construction?

  • by Prune (557140) on Monday June 25, 2012 @01:45PM (#40441137)
    Further discussion actually supports GP. Peer reviewed IEEE paper shows OAM is a scam: http://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=2062936&fileOId=2339120 [lub.lu.se]

Given its constituency, the only thing I expect to be "open" about [the Open Software Foundation] is its mouth. -- John Gilmore

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