Friday, July 29, 2011

Light, the new broadcast medium

With the radio-frequency spectrum becoming increasingly crowded due to a growing demand for wireless communications, a new part of the electromagnetic spectrum is shaping up to be one of the broadcast mediums of the future.

I'm talking about the visible light spectrum, ranging from red through violet -- or any combination thereof.

Using lasers to carry data over short and long distances is now very "old hat" with fibre-optic cables being the primary conduit for such bursts of light -- but now there's something different being proposed.

Thanks to the growing cost-effectiveness of powerful light-emitting diodes (LEDs), researchers are promising that very soon we'll be able to use regular visible light to communicate data at very high rates.

Some have speculated using something as mundane as streetlighting to replace WiFi as a two-way high-speed short-range communications links and others have proposed higher intensity lights placed in widely visible locations as being suitable for broadcast-type communications, carrying radio and television signals.

Due to the extremely high switching speeds of modern power LEDs, the data can be encoded in binary form (off/on) without any visible flicker or significant reduction in overall light intensity -- thus allowing the dual-functionality of these public lighting/broadcast nodes.

Of course while this may all work very well at night, researchers are quick to point out that visible light is more easily disrupted than most lower-frequency parts of the electromagnetic spectrum. Something as common as rain or fog can significantly reduce the range of visible-light signals and during the day, such signals are likely to be heavily swamped by the light of the sun.

Never the less, there are applications where visible light communications links may have significant benefits over their radio-frequency peers. Possible candidates include underwater communications, domestic and office networking, the delivery of data services within RF-sensitive environments such as commercial aircraft and broadcast information within transport tunnels.

What will they think of next?

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