If your slow Internet connection has you frustrated, just be glad you don't have to communicate with a probe on Mars. Even with new technology, scientists will be able to transmit only about 270 megabits per second between the two planets, not a lot of information when you're talking about superhigh-resolution photos. But a new study suggests that by twisting laser light, scientists could pack enough information into interplanetary beams to speed up extraterrestrial communications to the multi-gigabit level.
At the moment, laser-based communication between Earth and satellites uses so-called pulse-position modulation (PPM). In this strategy, information is coded into the timing of an infrared laser pulse. A given time span is broken into short windows, and data is encoded by sending the laser light to a detector during a particular window. To encode the alphabet, for example, the time span could be broken into 26 windows, one for each letter.
You could get higher bandwidth by cramming more windows into each time span. But the faster, more complex electronics needed to do that would make for an expensive and power-hungry system, says Ivan Djordjevic, an optical communications expert at the University of Arizona, Tucson. Instead, he says, we should scrap time encoding and harness a different property of light: its orbital angular momentum (OAM), a twisting pattern in the beam.
OAM concerns the phase o
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