Sunlight streaming through your living room window could be used to transmit data through your house – like Wi-Fi made of light.
Researchers designed a ‘smart glass’ system that can modulate the sunlight passing through it.
The system encodes data into the light that can be detected and decoded by devices in the room – and would be more environmentally friendly than normal Wi-Fi or mobile phone data transmission.
Basem Shihada, of King Abdullah University of Science and Technology in Saudi Arabia, had what he says was a ‘lightbulb moment’ while experimenting with a phone camera.
He said: "I was simply hoping to use a cell phone camera to record a video of the encoded light stream to try to decode the video to retrieve the data; that's when I thought, why not do the same with the sunlight?”
“This would be much easier and can be done over the cell phone camera too. So we began to explore sunlight as an information carrier.”
The team has now designed a sunlight communication system comprised of two parts.
"There is a light modulator that can be embedded in a glass surface and an in-room receiver," said Osama Amin, a research scientist in Shihada's labs.
"The modulator is an array of our proposed smart glass elements known as dual-cell liquid crystal shutters (DLSs)”
The liquid crystal shutter array, which would act like a filter to encode signals into the light as it passes, would require just one watt of power to operate, which can be supplied using a small solar panel.
In previous optical wireless communications system designs, data has typically been encoded by varying the light intensity, explained Sahar Ammar, a student in Shihada's team.
"But if the frequency of these intensity changes is too low, it can be detected by the human eye and cause an uncomfortable flicker effect," she said.
The DLS is therefore designed to manipulate a property of light called polarisation.
"Change in light polarisation is imperceptible to the eye, eliminating the flicker problem," Ammar said. "The communication system works by changing the polarisation of the incoming sunlight at the modulator side. The receiver can detect this change to decode the transmitted data."
According to the team's calculations, the proposed setup could transmit data at a rate of 16 kilobits per second.
"We are now ordering the necessary hardware for a testbed prototype implementation," Shihada said. "We would like to increase the data rates from kilobits to mega- and gigabits per second," he adds.
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