Light network via air hits 224 Gbps

Telecommunications-specific light over air, as opposed to Li-Fi, could be the answer to crowded last-yard media delivery.

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How about this for an idea: run broadband to the home via wires and then spurt the last few meters via airwaves.

Neat idea, right? You get the benefits of bulk speed through wire and the portability of a consumer device through airwaves.

And, if you think you've heard the idea before, you're not mistaken. It's called wired Internet service coupled with Wi-Fi. Been there, done that.

Still, it's a good idea.

Well, here's a novel twist on that theme — run broadband via fiber to the home and then send the last couple of yards via airwaves. But, in this case, don't translate to Wi-Fi for the last few yards. Use the light you've already got in the fiber and just extend it outwards from the wire to the devices.

Why bother with multiple technologies? Just use one.

Let there be light

Researchers are getting close to conceivably making this idea a reality, and have surprisingly obtained significant speeds in experiments. It's hard to do, though, because the light is difficult to point.

Neil Savage, reporting in IEEE Spectrum, the electrical and electronics engineer's association publication, says that the Oxford University-based team has gotten 224 Gbps over air. In contrast, the latest super-duper Wi-Fi routers that I've been writing about recently provide up to 3.2 Gbps over airwaves.

Potential with this light-based networking is 3 terabits per second, according to the team.

How it works

The idea is that you install a base station in the ceiling of a room. The base station projects infrared light towards a device like a PC. The PC does its thing, and then communicates data back to the base station in order to send it out onto the Internet again.

This technology is not Li-Fi. That technology uses visible light of the kind already used to illuminate a room. This new gear utilizes telecommunications light—the same kind of light used in a fiber cable. Thus the cleverness; there's no need to convert data.


The problem with the whole thing—and in fact the reason that you'd ordinarily use a cable to carry light-based data—is that light that's not contained in a carrier, like a cable, disperses.

The light needs aligning and steering. The way the experimenters are doing this is with an array of crystals in a grate.

That's like how a projector works, Dominic O'Brien, a photonics engineer working on the project, told IEEE Spectrum. O'Brien calls it Holographic Beam Steering.


Caveats abound, as one might imagine. The experiment thus far has only been controllable for three yards—still, that's a workable result for a home. And the device must be in a fixed position.

That stationary location is a bit more of a deal breaker as we transition to a portable, mobile device existence. However, fixed positions are still found today. One example of that is the old PC, and another—a rapidly growing and bandwidth-intensive device— is the television-connected media streaming player.

Conceivably, Internet of Things devices like refrigerators will be fixed too. Future device tracking systems, though, might alleviate this portability problem.

Field of view

Field of view is another factor. Good spread is crucial because the technology is based on numbers of wavelengths. The more wavelengths used, the more throughput. A 60-degree field can use six wavelengths, whereas a 36-degree view provides for three.


But where this technology may truly reveal its brilliance is in regards to the sticky matter of spectrum. Optical spectrum is more than radio. It's huge and unlicensed. Radio frequencies, of the kind jammed into 2.4 GHz and 5 GHz used by Wi-Fi, aren't so forgiving.

Just don't smoke under the base station or in front of that media player. The particles could cause the light to scatter, according to one IEEE Spectrum commenter.


Copyright © 2015 IDG Communications, Inc.

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