1Gbps Wireless Network Made With Red and Green Laser Pointers

MrSeb writes "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. Now 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. A red and green laser pointer were used, each transmitting a stream of data at 500Mbps, which is then multiplexed at the receiver for a grand total of 1Gbps."

Not new

[Anonymous Coward]

This is old hat:
http://www.airlinx.com/products.cfm/product/19-0-0.htm

It's stuff you can just go buy in a shop, we've used it here for around 15 years to connect across a street to the other office. We have a laser interlink.

Old news...they wear out

[drwho]

This was done years ago. I remember seeing the story, I think it was on gbppr. The problem is, these laser pointers aren't designed to be used constantly and they wear out.

Re:radio lasers

[mpoulton]

Are there any radio lasers around?

That would be a MASER (microwave, not light), and they predate lasers. However, a maser holds no advantage over a regular microwave transmitter for terrestrial communications. The distance of point to point microwave links with standard radio technology is limited by the curvature of the earth, not power or beam divergence. Even with tall towers, it's very hard to obtain a line of sight path between two points on earth more than about 50 miles apart.

Re:Not new

[symbolset]

And a screaming deal at only $28,000 for a pair. [neobits.com]

Re:Not new

[dark12222000]

You're missing the point. The summary clearly states that the interesting point here is that it was done with cheap 10$ laser pointers that you can buy from Amazon. Yes, this was old tech - if you were willing to shell out 15k for high end gear. The fact that it can be reproduced for a much lower price (maybe a few hundred at most by the time you get integrated units and pay for research?) and therefore more likely to see more widespread usage, is the point.

A similar project

[ard]

A proof of concept on laser pointer networking was done two years ago, if you are interested see
http://www.diva-portal.org/smash/record.jsf?searchId=4&pid=diva2:325270 - Fulltext at
http://www.diva-portal.org/smash/get/diva2:325270/FULLTEXT01

Also of interest to the low-cost DIY crowd

[subreality]

10Mbit, 1200-1400 meter range, GFDL-licensed open designs: https://en.wikipedia.org/wiki/RONJA [wikipedia.org]

Instead of lasers they use LEDs with relatively inexpensive lenses.

Re:Old news...they wear out

[thegarbz]

Got a source on that? Laser diodes don't "wear out" as far as I am aware. They may be damaged by thermal runaway in the short term or long term by poor design but the only critical factors here is the stability of the current source, choice of bias point, and thermal design. They certainly don't get tired over time.

Re:Cell Towers?

[adolf]

Visible line-of-sight issues ruin the possibility in many applications. Rain is murderous to low-power visible light connections, as is fog and snow. Even wind will affect a laser-based length over any substantial distance as the end-points sway (and yes, all towers sway in the breeze).

Meanwhile, cell towers quite commonly already link with microwave: The big parabolic reflectors covered with fiberglass radomes that you see on many (perhaps most, or nearly all) cellular towers are not for subscriber usage, but to link neighboring towers together. This is often done using licensed frequencies, though unlicensed bands are also used.

There are generally also redundant backhauls using copper or fiber or both, but I guess the point I'm trying to make is that cell towers -already- use wireless RF backhauls...and that the tech described in the article isn't likely to change that.

As it stands, resistance to rain-fade and other weather seems to be excellent, at least anecdotally: I've never experienced it, and I've carried a cell phone for at least 1.5 decades.

(Disclaimer: I work with RF and wide-area long-range wireless networking as part of my day job, though not necessarily with back-end cellular systems in particular. Just because optical networking seems like a general non-starter to me doesn't mean that it's unsuitable for the uses that you suggest.)

Re:Not new

[Midnight Thunder]

While the technology is old, the implementation seems to be new. Also, the form it has taken means that we are likely to see cheaper commercial solutions coming out or a whole bunch of hobbyists implementing this themselves - or both. $100 vs $4000+. I can just imagine mesh networks based on this.

If these can be coupled with solar power and are of low energy use, then I can imagine these being alternative solutions to laying cables in remote areas.