Researchers Demo 2.5 Terabits per Second Link Using Orbital Angular Momentum

Light can be twisted and combined to transmit data at dramatically increased speeds June 29, 2012
I first reported Vorticity Transmission Could Increase Spectrum Efficiency in February 2011. In March of this year, I reported on 'Twisted waves' Technology Demonstrated in Venice, showing how quickly this discovery based on radio waves from space was being exploited here on Earth. This week, the University of Southern California (USC) reported a USC-led team demonstrated light can be twisted and combined to transmit data at dramatically increased speeds
A research team led by USC and consisting of scientists from U.S., China, Pakistan, and Israel developed a system that uses these twisted beams of light to transmit data at speeds up to 2.56 terabits per second. While the underlying technology is the same as the demonstration using 2.4 GHz in Venice, this demonstration used light waves. As Alan Willner, electrical professor at the USC Viterbi School of Engineering and an author of the article about the research that was published in Nature Photonics explained, “You're able to do things with light that you can't do with electricity. That's the beauty of light; it's a bunch of photons that can be manipulated in many different ways at very high speed." 
Willner and his colleagues used beam-twisting “phase holograms” to manipulate eight beams of light so that each one twisted n a DNA-like helical shape as it propagated in free space. Each of the beams had its own individual twist and each was modulated with its own 16-QAM signal, a common emission type for microwave links. For RF links, the challenge will be developing an device that performs the function of the “phase holograms” at RF frequencies. The technique, however, has promise for use in free space links between buildings in a city or between satellites in space.  The research team will also be looking at how it could be adapted for use in fiber optics. 

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