'Twisted' waves could boost capacity of wi-fi and TV

[bananas]

Source: BBC

A striking demonstration of a means to boost the information-carrying capacity of radio waves has taken place across the lagoon in Venice, Italy.

The technique exploits what is called the "orbital angular momentum" of the waves - imparting them with a "twist".

Varying this twist permits many data streams to fit in the frequency spread currently used for just one.

The approach, described in the New Journal of Physics, could be applied to radio, wi-fi, and television.

<snip>

Read more: http://www.bbc.co.uk/news/science-environment-17221490

[Orrex]

1. AT&T has already announced plans to limit their unlimited twisted data streaming service.

[patrice]

2. Mugging the people!! for PUBLICLY DEVELOPED & SUBSIDIZED (in tax breaks & low wages) resources.

[Ezlivin]

3. I think I'll twist one up right now

Oh, wrong forum....

[tridim]

4. SETI should probably take note of this (if it works).

Though I'm still trying to imagine what a real-world twisted wave would look like since radio waves aren't just 2D sine waves.

[TalkingDog]

8. OK that makes my head hurt.

I was going to say - like the whirlpool in your tub except in a wave form... but then I realized that's still, essentially, 2-D.

ow... my head

[tridim]

9. I'm thinking it gets into the realm of 4D shapes like the hypersphere.

Other sites describe it as rotini-like, which obviously isn't correct.

[kestrel91316]

5. I can't even get my basic wifi router to work. How troublesome would this

newfangled stuff be???

[bananas]

6. What kind of problems are you having?

Post a message in the Computer Help and Support Group http://www.democraticunderground.com/?com=forum&id=1095

[kestrel91316]

10. Thanks. Hope they can help me. I don't want to have to hire a geek to hook up a $40 router.

[eppur_se_muova]

7. Um, isn't this just circular polarization ?

The discussion of 'orbital' vs 'spin' angular momentum seems a bit off to me, but then angular momentum has never been my strongest topic. Orbital angular momentum is a property posessed by electrons in atomic systems; I don't see how a photon, which is not in an orbital, can display orbital angular momentum. It seems to me that this is more of a distinction between properties of individual photons vs collective phenomena of a large ensemble ... but what do I know. This may be one of those cases where a theory makes correct predictions for the wrong reasons ...

[Fumesucker]

11. Evidently different "pitches" of circular polarization can be separated out at the antenna..

I know right and left hand CP can be discriminated at the antenna, that's why CP is so resistant to multipath, reflected waves have the opposite handedness.

[KamaAina]

13. I thought of polarization as well

For years I'd thought of using it in multiplexing. Looks like the real world has appropriated yet another of my half-baked "Ralph Kramden schemes".

[Fool Count]

14. It is, indeed, just circular polarization. You generate it by delaying one of the two linearly

polarized waves (orthogonal to each other) by Pi/2 phase (or a quarter period). In theory, you
double the capacity by having two independent waves instead of one. In practice, it would work
as long as propagation does not destroy the polarization properties of the wave. It is trivial
to separate the two orthogonal linearly polarized waves at the antenna.

[midnight]

12. K&R