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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.
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.
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
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.
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air is not transparent and does cause beam scattering. by creating a refractive channel like this they absolutely will reduce beam dispersion. obviously it doesn't eliminate beam spread but even a fiber channel perfectly designed for a single mode will have some diffusion so whats your point?
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.