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'Optical Fiber' Made Out of Thin Air
Dave Knott writes: Scientists from the University of Maryland say they have turned thin air into an "optical fiber" that can transmit and amplify light signals without the need for any cables. As described in the research, this was accomplished by generating a laser with its light split into a ring of multiple beams forming a pipe. Very short and powerful pulses from the laser are used to heat the air molecules along the beam extremely quickly. Such rapid heating produces sound waves that take about a microsecond to converge to the center of the pipe, creating a high-density area surrounded by a low-density area left behind in the wake of the laser beams. The lower density region of air surrounding the center of the air waveguide has a lower refractive index, keeping the light focused, and allowing the higher-density region (with its correspondingly higher index of refraction) to act like an optical fiber. The findings, reported in the journal Optica, have applications in long range laser communications, high-resolution topographic mapping, air pollution and climate change research, and could also be used by the military to make laser weapons.
On top of a shark's head.
Can this be mounted on a Shark?
Now we just need frickin sharks that can fly.
and the only ones that looked remotely practical was the laser weapon and remote sensing requiring high power high focus.
Using lasers for freespac communications is already very practical and well solved, just look at this example
http://esc.gsfc.nasa.gov/267/2... (BTW definitely one of the better uses of NASA's budget. )
All the other mentioned applications also have off the shelf solutions that perform exceptionally well. The weapons and high power remote sensing however while listed last seem to have the most to gain. Being able to generate a waveguide in either case solves their two big problems atmospheric distortion and the need to focus large amounts of laser energy on a small point.
I see you stopped your music education in kindergarten.
Excuse the other bullshit we made up to make this look like civil research.
Here's a link to the press release from UMD with some links to the professor's web site.
http://cmns.umd.edu/news-events/features/2356
When reading the description of a bundle of laser beams guiding a central one, I can't help but think of a ladder evolving in the game of Go... http://en.wikipedia.org/wiki/L...
One of the chief benefit of optical fiber is that it doesn't require LOS. All they've done here is demonstrate the capability to mimic the loss-less advantages of optical fiber without actually having a fiber ... once they can do this around corners... then maybe they've "created optical fiber out of thin air" until then not so much.
But, does it bend? After all, that's the point behind fiberoptics, to be able to snake a light beam around corners and through tight spaces so that we don't have to maintain perfect optical alignment over a distance. So, what's the point of this setup? Does it keep moths away by burning them on the outer beams?
When our name is on the back of your car, we're behind you all the way!
It's the stuff they made the Emperor's clothes with.
"A person is smart. People are dumb, panicky dangerous animals and you know it." - K
My phone does this, it's called "Speaker mode"
Seriously, saying "fiber optic cables from thin air" is an idiotic statement. IR remotes have been doing this for decades, and using lasers to do so has also been done for ages.
I'm puzzled as to what this does or what it's good for, exactly.
... they have turned thin air into an "optical fiber" that can transmit and amplify light signals without the need for any cables.
1. Air already transmits light signals. It's transparent.
2. They haven't mentioned anything about amplifying light signals. This would be hard.
So, they are creating a "pipe" that can transmit light... but it doesn't stop beam spread (since the beams that make up the "pipe" still have diffraction-limited beam spread), and it can't bend light around corners. So, they now have a pipe that will funnel a laser beam along the path made by other laser beams, which take it exactly the same path that the beam would go without the pipe...
http://www.geoffreylandis.com
Sounds prohibitively expensive.
Increasing the bandwidth of existing fiberoptic cables:
We present simulations of a scheme to perform wavelength conversion of signals that eliminates phase-noise transfer from the pump to the converted signal. Nondegenerate four-wave mixing in a semiconductor optical amplifier is used to convert the signal to a new wavelength; and if an optical comb generator is used as the multiple-pump source, then the signal can be converted without incurring any phase-noise transfer from the pumps. We highlight the capabilities of this scheme by simulating the conversion of 16-QAM signals at 10 Gbaud and showing that errors due to phase-noise accumulation are eliminated thus enabling conversion whose only impairment would be the total additive optical noise.
Source: http://doras.dcu.ie/19643/
Pretty well actually
http://www.fastlinks-wireless....
http://etherealmind.com/free-s...
They are currently in widespread use
The real question is just how much improvement would you get with the new system under inclement conditions. The other big question is how they fare against microwave links.
Is it just me, or does the idea of "creating a ring of lasers" to enable laser communication seem sort of silly? I mean, we already can communicate using a single laser. Why bother with the ring? Does it cut through fog or something?
The one aspect I found interesting is the differential air density. Properly tuned, it might be useful to push or drill at a distance with only light.
Why not just use the first laser to transmit the data you need in the first place?
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Stay tuned for some shock and awe coming right up after this messages!
Yes, because of those fat grants scientists get for climate change research, right?
So if I understand this correctly, the beams that form the "psudofiber" have to be intense enough to heat the surrounding air in less than a microsecond... and the signal will be pushed down the center of the pipe... so all those hoards of unholy photons that created the pipe in the first place are going to arrive at the destination a microsecond before the signal does, and they should still be nicely focused and searching for a nice electronic sensor to deposit all that energy into... Or did I miss something?
Which has more power: the hammer, or the anvil?
Baby on board, oh how I adored...
Science advances one funeral at a time- Max Planck
Holography. Seriously, how is this missing?
But can it vaporize a human target from space?
That sign on my car's window paa-yyy aayyy aayyys...
This would be good for performing measurements on objects you wouldn't want to get that close to. Like nuclear reactors.
Would be like the 'End' sequence in Ender's game where they use the drones to protect the gunship (or in our case the actual laser signal)
More like thick air wrapped in thin air.
Read: http://www.ars-nova.com/Theory...
Silence is a state of mime.
Predicted the 1960's (Kerr-induced self-focusing: http://journals.aps.org/prl/ab... ), and it was a big part of SDI: http://www.ncbi.nlm.nih.gov/pu... and was again applied to space-to-ground weapons systems in 2009: http://journals.aps.org/prl/ab...
It was ale demonstrated at LLNL in 2009: http://www.researchgate.net/pu... and 2010: http://www.researchgate.net/pu...
What's new about this one is that they've renamed the tunnel as the desired artifact, rather than describing it in beams going down the tunnel.
All you'd need is a big spinning mirror and you could vaporize a human target from space.
Uh oh ... better tell the Key of A# that its supertonic is a C. It will be surprised!
A million pigeons cried out in terror and were suddenly silenced.
Donte Alistair Anderson Roberts - hi son!
Karma: Chameleon
so.... A laser tube to conduct a laser signal? To protect the internal laser?
-no sig today-
air is not transparent
To the extent that air is not transparent, this doesn't work.
and does cause beam scattering.
This does not address beam scattering. If the air is scattering the laser beam, it still scatters the beam.
by creating a refractive channel like this they absolutely will reduce beam dispersion.
It would reduce beam spread... except that the beams that create the channel are not themselves channeled.
obviously it doesn't eliminate beam spread
on this we agree
but even a fiber channel perfectly designed for a single mode will have some diffusion so whats your point?
My point is that from a surface-level analysis, it doesn't do anything useful.
they may be able to increase snr by 10^4 over current technologies at 100 m. that's a serious improvement that shouldn't simply be dismissed so thoughtlessly.
Let me repeat. The beams that create the channel are not themselves channeled. So the channel itself... has the diffraction, scattering, and beam spread of an unchanneled beam. The net result can't be better than an unchanneled beam, because it is made out of an unchanneled beam.
http://www.geoffreylandis.com
Solitons, baby.
...or a laser bread slicer can now all be ours!!
I was not trying to kill him, I was simply sending him a large amount of high speed data.
Do not look at laser with remaining good eye.
So the channel itself... has the diffraction, scattering, and beam spread of an unchanneled beam.
The beams making the channel are channeled by themselves, they create filaments that self-focus the beam. Self-focusing beams in air have been pretty well established at this point and will go quite far if you have enough power because of the attenuation involved.
It's "how I adore", not "oh how I adored" and it's "window pane" not whatever you wrote.
Amateurs.
So the channel itself... has the diffraction, scattering, and beam spread of an unchanneled beam
The channel is created out of lasers strong enough to create self-focusing filaments in air. Even if you have slight beam spread, the filamentation process cause the beam to essentially collapse to a very small diameter as long as you are above a certain power density (although high enough, and you get multiple filaments). This will negate diffraction and beam spread. Because the filament process is quite non-linear, scattering is not much of an issue and the fraction of small fraction of scattered light will not have the same effects on the air. The only big effect on the channel creation is a strong attenuation of the beam due to all of the energy being spent on ionizing the air column.
Let me repeat. The beams that create the channel are not themselves channeled. So the channel itself... has the diffraction, scattering, and beam spread of an unchanneled beam. The net result can't be better than an unchanneled beam, because it is made out of an unchanneled beam.
Not necessarily. Since the surrounding laser pulses should spread in a more or less uniform way, the central channel of denser air should still occur as distance from the emitter increases and remain centralized in the channel. It sounds like it will make air work a little like graded index multimode fiber. The difference in density between the central channel and the surrounding air will likely fall off with distance, making the air channel less efficient, but still present out to some distance. It's not like this would allow perfect single-mode propagation to infinity in a coherent beam, but it could improve bandwidth and/or distance capability for point-to-point laser communications.
Granted, I'm just another /.-er who never RTFAs, but I do have some experience w/ FO comms and free-air transmitters (of one wavelength or another).
So consider: the channeling lasers may disperse, but they carry no information beyond the existence of the channel and possibly the source and destination. The transmitted data packets do not disperse, so what you've got is the equivalent of a phased-array transmitter with zero sidelobes.
https://app.box.com/WitthoftResume Code: https://github.com/cellocgw
A pipe is interesting, but being able to create such pressure zones and corresponding changes in index of refraction is more interesting in generating 3D holography in a volume of air - you could make an array of these and then pulse the whole works so as to cause the air to refract in space. Just the thing for making a hologram without resorting to some kind of added media such as fog or microparticles to be the reflective "screen" in the tank.
Nice sig, man!
So the channel itself... has the diffraction, scattering, and beam spread of an unchanneled beam.
The beams making the channel are channeled by themselves, they create filaments that self-focus the beam. Self-focusing beams in air have been pretty well established at this point and will go quite far if you have enough power because of the attenuation involved.
So, what you just said is that the beams self-channel anyway.
So, if beams self-channel, this innovation does nothing, right? It's a complicated system of multiple beams to make the beam channel, which is to say, self-focus. But you just told me "self-focusing beams in air have been pretty well established at this point."
http://www.geoffreylandis.com
From the first sentence of the paper abstract:
Collection of weak signals from remote locations is the primary goal and the primary hurdle of optical stand-off detection schemes.
If this is being used to channel weak signals, than the weak signals will not create filaments or self-focus. In a bigger picture though, while a single beam will filament, a lot of improvements have been found by using two or more beams to minimize the total attenuation, as opposed to just sending all of the light at once. Especially since above a certain power density you can have problem with multiple filaments forming within the beam and they won't be symmetric or well-behaved compared to a beam with a single filament.
Someone has found Tesla's notes?
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