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Information crossing the oceans on aerial highways

Images and data will one day be transmitted instantly across the planet thanks to “aerial highways” created through the use of “air wave-guides”… this is the vision investigated and promised by a research team from the University of Maryland.

October 2014

IMALab Information crossing the oceans on aerial highways

In the Big Data era, the ability to transport great masses of information over great distances in an extremely short time is an increasingly pressing need.

The most efficient method at the moment is the light that travels along optic fiber cables, a system which however involves laying extremely long and extremely expensive cables. Dozens of such cables have been laid on the ocean floor between Europe and the Americas, with an average length of 15,000 kilometers. And one cable has been laid between the United Kingdom and Japan which measures 28,000 kilometers.

Transporting data in light through the air, on the other hand, suffers from the limitations of light intensity diminution over long distances or disturbance from the presence of gas. Even the extremely tight and precisely directed beams produced by laser devices lose focus over long distances due to a natural spreading out process.

Fiber-optic cables trap light beams and guide them like a pipe, preventing loss of intensity or focus. Typical fibers consist of a transparent glass core surrounded by a cladding material with a lower index of refraction.  When light tries to leave the core, it gets reflected back inwards.  But solid optical fibers can only handle so much power, and they need physical support that may not be available where the cables need to go for some operations, such as the upper atmosphere.

Now, a research team from the University of Maryland, guided by Professor Howard Milchberg, is developing a way to make air behave like an optical fiber cable, guiding light beams over long distances without loss of power.

Milchberg’s "air waveguides" consist of a “wall” of low-density air surrounding a core of higher density air.  The cladding wall has a lower refractive index than the core — just like the cladding of optical fiber — and therefore reflects divergent light back to the center.

In experiments with an air waveguide used to transfer a signal from an emitter to a detector one meter away, the signal was measured as 1.5 times stronger than a signal transmitted without the waveguide.  That may not seem like much, but over distances that are 100 times longer, where an unguided signal would be severely weakened, the signal enhancement would be much greater.

Experiments are continuing, in order to demonstrate that the air waveguide technology can be used over much longer distances, and to develop ways of implementing this potential. If this works, it will open up a whole world of possibilities.  Air waveguides could be used to conduct chemical analyses of places like the upper atmosphere or inside nuclear reactors, where it’s difficult to get instruments close to what’s being studied.  Waveguides could also be used for carrying out LIDAR operations… a variation on radar that uses laser light instead of radio waves to make high-resolution topographic maps.

And beyond that, the sky’s the limit when it comes to imagining further revolutionary uses of this technology in the field of telecommunications and the development of ‘smart’ cities.



Full main research article published in Optica, July 2014