tim's journal

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:

Model	Technology	Range	Max bit rate	Cost per link
Adtran 5045	5.8 GHz microwave	25 mi	90 Mbps	$14,000
Adtran Tracer 6420	5.8 GHz microwave	30 mi	16.4 Mbps	$12,000
Canon Canobeam DT-110	Optical	1.2 mi	1.25 Gbps	$14,200
LightPointe FlightLite 100	Optical w/ RF backup	.3 mi	100 Mbps	$7,500
LightPointe FlightStrata G	Optical (4-beam)	2.1 mi	1.25 Gbps	$28,990
Orthogon Gemini	5.8 GHz microwave	124 mi	33.6 Mbps	$11,990
Orthogon Spectra	5.8 GHz microwave	124 mi	300 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 December 18, 2005 10:45 PM | TrackBack