DarkLight removes Li-Fi restriction, allows visible light to transmit data in the dark

Discovery uses light pulses imperceptible to the human eye to provide bandwidth that is 10,000 times greater than radio and more secure

DarkLight removes Li-Fi restriction, allows visible light to transmit data in the dark
Credit: Yandle via Flickr

Visible Light Communications (VLC), or Li-Fi, is a new optical wireless communications technology that promises spectacular amounts of new bandwidth for data transmissions. It uses visible light spectrum. Common lights could, indeed, be used to create the networked communications.

However, there’s a drawback to this optimistically regarded tech, say scientists. The receivers need to see the light bulbs. That means the space in which this technology is used can’t be dark, and that's a problem if someone wants to sleep in the room. 

A solution is to dim LEDs or switch them on and off at high speeds, so the eye can’t see it.

Researchers from Dartmouth College say they have a working solution for encoding “data into ultra-short, imperceptible light pulses.” The pulses aren’t visible.

They call it DarkLight and say it will increase the potential applications for Li-Fi, or VLC.

Their “DarkLight prototype supports 1.8 meter distance with 1.6 kbps data rate,” the scientists from the Department of Computer Science and Department of Physics and Astronomy say in an abstract of their paper (PDF), published on the college's website.

That’s enough distance, in the test environment, to send a signal from a ceiling-mounted smoke-detector-like device to a desktop or a bed.

It’s “Visible Light Communication in the dark,” they explain.

Li-Fi communications use cases

Li-Fi communications—which conceivably offers 10,000 times greater bandwidth than radio, the scientists claim—could ultimately be used for “low-cost beacons, backhaul, rural broadband, sensors and the Internet of Things, among other uses,” I wrote last year. Indoor positioning was tested by Philips and supermarket Carrefour in 2015.

Commonly installed rural solar panels as a broadband receiver was also a use discussed then.

At that time, the concept of switching lights on and off “within nanoseconds—too rapidly for the human eye to see”—was an approach discussed in order to make Li-Fi appear dark.

The Dartmouth scientists say their now-functioning system tackles “challenges in circuit designs, data encoding/decoding schemes, and DarkLight networking to efficiently generate and reliably detect” the ultra-short light pulses. In other words, they say their system works.

Their system “demonstrates for first-time, how visible light can transmit data in the dark,” according to their press release.

Better security than Wi-Fi or Bluetooth

If Li-Fi can be made to work properly, it could have some significant advantages over radio. In addition to the aforementioned bandwidth gains, visible light spectrum means it’s inherently secure.

In the same way that normal light doesn’t spill from room to room when the cracks in the door frame are sealed, Li-Fi data won’t spill from room to room. That conceivably makes it more secure than potentially hackable Wi-Fi or Bluetooth, for example. All you need to do to prevent Li-Fi from getting hacked is seal a room visually.

Light-based networks also have advantages in that they can work in places where radio interference could be problematic—hospitals, for example.

Lights are also everywhere—car headlights, street lights and reading lights are just a few examples.

But perhaps one of the most intriguing possible uses is in rural backhaul to basic solar panel—where the photovoltaic panel both powers the link and is the link.

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