December 19, 2005

Free Space Optical - 72 km, 500 Mbps

Found what I was looking for - thanks to the Naval Research Laboratory. Moore et al. used a 1550-nm laser operating at 2.5 W to achieve an effective one-way link distance of 72 km. Recall that the Canon device achieves approximately 1 Gbps over about 1 km using a 11 mW laser. So, using a more powerful laser, here, 200x, gives a 72x improvement in range.

Posted by torque at 12:15 AM | Comments (179) | TrackBack

An open source 10 Mbps optical link

Spotted on an engadget comment: "Ronja is a free technology project of reliable optical data link with current range 1.4km and current communication speed 10Mbps full duplex."

Posted by torque at 12:04 AM | Comments (5) | TrackBack

December 18, 2005

Free Space Optics of the Mbps and Gbps variety

Not much is new under the sun, but what has been around, keeps getting better. Communication via free space optics has been around for literally ages - remember the signal fire lit above Minas Tirith to call Rohan for help. Probably about 1 bpm. Enter the latest generation of laser-based free space optical network: LightPointe's FlightStrata boasts 1.25 Gbps! You might be wondering why my mind has been hovering on these matters - I've been trying to come up with a backup scheme for my office network involving free space optics and a shed some distance away...

Oliver Rist and Brian Chee have a nice article on this popular-in-the-city option. Especially useful are price ranges for these devices - often hard to get without signing yourself up for a lifetime of spam. They review seven solutions from four different vendors: Adtran, Canon, LightPointe and Orthogon. I've heard of Canon and LightPointe, but not the other two (probably because they are microwave - not optical*). Prices range from about $10-30K for an end-to-end link - with a variety of options. At the highest bit rates, as you can imagine, atmospheric adjustment is involved.

*From a physics standpoint - it's all EM...

This is what you want to know:

ModelTechnologyRangeMax bit rateCost per link
Adtran 50455.8 GHz microwave25 mi90 Mbps$14,000
Adtran Tracer 64205.8 GHz microwave30 mi16.4 Mbps$12,000
Canon Canobeam DT-110Optical1.2 mi1.25 Gbps$14,200
LightPointe FlightLite 100Optical w/ RF backup.3 mi100 Mbps$7,500
LightPointe FlightStrata GOptical (4-beam)2.1 mi1.25 Gbps$28,990
Orthogon Gemini5.8 GHz microwave124 mi33.6 Mbps$11,990
Orthogon Spectra5.8 GHz microwave124 mi300 Mbps$20,000

Wait, 124 mi is really far!

Incidentally, all of these, I believe, are license-free. The Canon product uses a wimpy 11 mW eye-safe infrared laser. I wonder how much more range you can get by swapping it out for a "real" laser and leaving the modulation stuff intact.

Canobeam's optical beam transmission technology is reliable, secure and engineered for maximum safety. According to the International Electrotechnical Commission (IEC), the worldwide advisory agency responsible for eye safety guidelines, Canobeam's laser transmitters are designated as "IEC Class 1M" eye safe, or in other words, safe when viewed by the naked eye. (IEC/EN 60825-1/A2:2001 Class 1M; FDA Laser Notice.50)
And then, the best line:
"It is not recommended to view the light using magnifying objects such as binoculars at the point of output."

Posted by torque at 10:45 PM | Comments (2) | TrackBack