Wednesday, May 2, 2012

1Gbps wireless network made with red and green laser pointers

laser-pointers-348x196 Back in the olden days, when WiFi and Bluetooth were just a glimmer in the eye of IEEE, another short-range wireless communications technology ruled supreme: Infrared Data Association, or IrDA for short. IrDA was awful; early versions were only capable of kilobit-per-second speeds, and only over a distance of a few feet. Trying to get my laptop and mobile phone to link up via IrDA was, to date, one of the worst tech experiences I’ve ever had.

There’s a lot to be said for light-based communications, though. For a start, visible (and invisible) light has a frequency of between 400 and 800THz (800 and 375nm), which is unlicensed spectrum worldwide. Second, in cases where you really don’t want radio interference, such as hospitals, airplanes, and other sensitive environments, visible light communication (VLC), or free-space optical communication, is really rather desirable. Because of the prevalence of light sources (one in every room!) VLC could also be the basis for ubiquitous networking. Just last year, Harald Haas demonstrated an LED light bulb that could transmit HD video using VLC.

Now, I think for the first time ever, researchers at the National Taipei University of Technology in Taiwan have transmitted data using lasers — not high-powered, laboratory-dwelling lasers; handheld, AAA-battery laser pointers. The setup is rather simple: The engineers took a red and green laser pointer, wired in a 500Mbps data stream into each, and simply pointed them at photodiode receptors. On the receiving end, the signals are amplified and then multiplexed to create a 1Gbps data stream. The complete setup, according to New Scientist, cost just $600. laser-pointer-vlc-network-640x329

Yes, that’s a 1Gbps wireless network (around 100MB/sec, or about 10 times the speed of your 802.11n WiFi router), over distances of up to 25 meters, for $600. Not too shabby, especially when you consider that a commercial installation would probably cost a fraction of that. The bit error rate (BER) is also incredibly low: At 10 meters, just one bit per billion was erroneous; WiFi, by comparison, is fairly content with a BER of 1 in 100,000, or a packet error rate of 10%.

Will laser-based VLC actually find its way to market, then? There’s no getting around the fact that laser links are highly directional (even more so than the shoddy IrDA networks of yore), and atmospheric conditions will play a big part in the BER, and thus the actual data rate. With WiGig making its way to market, laser pointer VLC will probably never be seen by consumers. Still, for quick bursts of data between mobile devices, or wireless communications in hospitals, or simply as a fun hobby for amateur radio (?) operators, cheap, laser pointer VLC could be very useful indeed.

Extreme Tech

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