Wednesday, 27 June 2012

Twisted Light Leads to 2.56 Tb/s Link

Scientist from California and Israel say they've transmitted data through the air at a rate of 2.56 terabits per second using beams of "twisted light."
Such light poses the quantum property orbital angular momentum. As Alexander Hellemans explained in our May issue:
A photon can carry angular momentum just as a rotating body does and can even transfer the momentum to small particles, causing them to rotate.In theory, a photon can occupy any one of an infinite number of these quantum states, each associated with an integer value. These quantum states impart the radio beam with a distribution of phases as it travels through space that gives the beam the shape of fusilli pasta (a helix).
Beams with different orbital angular momentum can be transmitted together on the same beam and then distinguished from each other at a receiver as if they had been sent on separate channels.
The communications technology could find a home in  satellite communication links, in short free-space optical links on earth (such as between buildings in a city), or maybe in  fiber optic cables (which the engineers say is their next step).
Orbital angular momentum has been studied intensively at optical wavelengths, but recently physicists have been trying to apply it to radio frequencies. Scientists in Europe claimed the first twisted RF communications earlier this year. But others question whether twisted RF is really different from other multiple-input-multiple-output radio techniques.
The research was publish on 24 June in Nature Photonics. The research team included Jian Wang, Jeng-Yuan Yang, Irfan M. Fazal, Nisar Ahmed, Yan Yan, Hao Huang, Yongxiong Ren, Allan Willner, and Yang Yue from the University of Southern California; Samuel Dolinar from NASA's Jet Propulsion Laboratory; and Moshe Tur from Tel Aviv University.



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