An international team of researchers have managed to achieve data transmission speeds of 2.5 terabits per second by “twisting” light waves. They believe the same technique could also be used for more traditional wireless transmission.
The technique involves controlling the movement of light waves in two different ways: the spin angular momentum (which is already controlled in radio wave transmissions) and the orbital angular momentum (which has not previously been controlled.)
The most popular analogy is if we had previously been able to control the way the Earth spins on its axis, we now also gained the ability to control the way it moves around the Sun. Another way to picture it would be as a set of screws: whereas we’ve previously only been able to control the direction the screw faces, we can now vary the thread and thus control the amount of twist.
Scientists from Sweden and Italy have previously demonstrated that it is possible to transmit light beams controlling both forms of momentum. Now a collaboration of the University of Southern California, Tel Aviv University, and the Nasa Jet Propulsion Laboratory have carried out an experiment into practical uses of the concept.
The idea was that whereas optical transmissions currently send data over multiple streams of differing colors, the researchers could instead use light beams with a different orbital angular momentum.
To do this, they combined eight beams of light into one, with four twisted together in the center and four in a ring around them. Ironically the set-up was somewhat similar to a metal cable with twisted wires surrounded by a plastic sheath.
At the receiving end, this single beam was switched back into the eight original beams and the data extracted. The increased space efficiency allowed the 2.5 terabits per second.
It’s too early to get overexcited about the idea of downloading Blurays from Netflix in under a second: the experiment was only carried out across a one meter space. The researchers believe that the limitations that would come from using optical cabling would likely mean the technique would be restricted to transmissions of up to a kilometer or so.
One of the researchers, Professor Alan Willner, said those problems wouldn’t exist in space, meaning the technique could be adopted for high-speed communications between different satellites.