850nm vs. 1550nm?
800-850nm is the common wavelength used in Free-Space Optics for the thru-the-air beam due to cost / performance optimization.
Some manufacturers market 1550nm devices based on the fact power levels can be increased 100 x's while remaining eye safe due to human eye aqueous fluid energy absorption science.
This is one of the times you can literally make the statistics support either side of the discussion, depending on which side you happen to be on. Although it is true you can hit the laser with 100 x power, it does not follow that the link's margin ends up anywhere near 100 x's as high.
It does not end up even 10 x's as high.
Our experience is that it is more like 10% more at best, which is lost due to high beam divergence rates and mis-pointing as the only links with 1550nm lasers in them currently do not offer active alignment.
And there is a fairly high price to be paid for going with 1550nm lasers. They require active heating and cooling to maintain intensity and/or their center frequency which is a costly addition on their system boards (about 2x $).
Also, night vision scopes, sometimes used in diagnosing alignment issues on non-active aligned links, cannot be used as they do not register 1550nm light.
Overall, 850nm is probably the winner.
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What's HOT, what's not...
Auto tracking? >>
Single vs. multiple beams? >>
Hybrid FSO + RF? >>
850nm vs. 1550nm? >>
Passive vs. Active? >>
Wikipedia on FSO >>
FSO vs. RF? >>
Security? >>
Eye Safety >>
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Where does Free-space Optics fit best? >>
Where does Free-space Optics not fit? >>
Competitive comparison of the major Free-Space Optics solutions. >>
Free-Space Optics White Papers. >>
Who are we, and what’s our motivation for supporting this web site? >>
And last but not least…here’s our Free-Space Optics commercial website for specific product and/or service inquiries. >>
...and our refurbished FSO equipment site. >>