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ArcticMyst Security by Avery
1Gbps wireless network made with red and green laser pointers
- Thread starter steve001
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gozert
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Isn't this pretty much the same as how optical fiber internet works, except that there's nothing in between the transmitter and receiver? Still interesting to read regardless.
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Dr_Evil
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Sort of. Visible light doesn't travel very far when using fiber network cable. You might seen some red used in short, low speed fiber runs. Everything else is IR. It has been possible for at least the pass few years to use a single strand for transmit and receive. That method uses wave division multiplexing with 1310nm and 1490nm.
The problem with using cable is that the light bounces off the sides. That causes a loss over long distance. You'll have a greater signal loss over 25 feet using 660nm instead 1310nm. There are ways to help reduce he loss such as coatings and stuff.
bdgreenb
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i wish he would retest it while chain vaping in the room, i imagine the error rate would increase and actual passable data would diminish almost in line with the opacity of the room 
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Do they plan on deploying a system like this? It seems super ineffective and unreliable.
joeybab3
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i wish he would retest it while chain vaping in the room, i imagine the error rate would increase and actual passable data would diminish almost in line with the opacity of the room
Bu far the best thing i have ever read on this entire forum
Dr_Evil
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Ineffective, no. Unreliable, you'll most likely see degradation in snow, rain, smog or other conditions that will make the air not so clear. It would actually be cheaper than running cables all over. Plus you don't have to worry about bad cables.
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Hmm how is it effective? Is it cheaper than RF equipment?
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Who is going to clean the collimating lenses and receivers every week?
Will a DPSS green perform well in the full range of outdoor temperatures?
Will a DPSS green perform well in the full range of outdoor temperatures?
Dr_Evil
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Networks using optical stuff is fairly cheap. A 5mW emitter would be powerful enough. How's it effective? It's more secure for one. Let's say you have offices in 2 different high rise buildings. You can set up a line-of-sight network between them of a dedicated network separate from the internet. It is very difficult to tap into a network that uses optics without someone noticing. You can also get very high speeds. There are networks with speeds up to 10Gb/s.
Check these out
Laser Line of Sight Communications | FastLinks Wireless | FastLinks Wireless Network Solutions
New laser network between NYSE and NASDAQ will allow high-frequency traders to make even more money | ExtremeTech
diachi
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Not to mention reliability issues caused by weather. Good idea in theory, not actually very practical.
We've thought about it doing it for a voice link between the Rx/Tx side of a 10 meter band repeater (Using different sites for separation, duplexers for 28Mhz are too big to be practical for us! Vertically stacked vertical antenna's may also work...). Just wasn't going to be practical during snow, rain or fog - and we weren't trying to push 1Gbps of data over it, just a rather narrow audio signal.
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Benm
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The 'line of sight' part is a bit problematic since it has to be literally available when using lasers for the links. This means that the system will probably malfunction when it's raining, snowing, foggy, etc.
Then again, if you need to set up a point to point link in a remote area where little alternative is viable, i suppose it could be done. In terms of speed over a fairly long range (say 1 km or so) such a system would far outperform consumer wifi, despite being down from time to time due to weather. Obviously if you are in the desert or something this may be less off a problem - at least untill you get a sandstorm.
Then again, if you need to set up a point to point link in a remote area where little alternative is viable, i suppose it could be done. In terms of speed over a fairly long range (say 1 km or so) such a system would far outperform consumer wifi, despite being down from time to time due to weather. Obviously if you are in the desert or something this may be less off a problem - at least untill you get a sandstorm.
Three watt leds do far better then 15 mW lasers. No coherence, wider optical bandwidth, busts thru the scintillation
this site and its links explain it all...
KA7OEI Optical (lightbeam) through-the-air communications page
Watch the video on the front page....
Video URL:
https://www.youtube.com/watch?feature=player_embedded&v=Ef895aQCJxs
Steve
this site and its links explain it all...
KA7OEI Optical (lightbeam) through-the-air communications page
Watch the video on the front page....
Video URL:
https://www.youtube.com/watch?feature=player_embedded&v=Ef895aQCJxs
Steve
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Benm
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I think what we are looking at in the video (other link doesnt work from here) is speckle, caused by imperfections in the telescope used as a beam expander here.
Speckle obviously is a potential problem, but is most prominent when using something like a telescope that isn't solidly fixed to the laser. By solidly i mean that it should not be able to move in regards to the laser by something in the order of the wavelength.
In practice this is no easy thing: imagine having to construct a rig that kept a laser pointer at a distance from a telescope within 50 nm or so, even in windy conditions and such.
At larger distances atmospheric problems also play up. If you have a good view of some lights 20 km away, you will notice it's very hard to take a clear photograph of them with long exposure time. Even when not very visible to the naked eye, 'twinkle' becomes a problem in such cases.
Speckle obviously is a potential problem, but is most prominent when using something like a telescope that isn't solidly fixed to the laser. By solidly i mean that it should not be able to move in regards to the laser by something in the order of the wavelength.
In practice this is no easy thing: imagine having to construct a rig that kept a laser pointer at a distance from a telescope within 50 nm or so, even in windy conditions and such.
At larger distances atmospheric problems also play up. If you have a good view of some lights 20 km away, you will notice it's very hard to take a clear photograph of them with long exposure time. Even when not very visible to the naked eye, 'twinkle' becomes a problem in such cases.
While there is always some speckle, what you are looking at is index of refraction shifts along the path between hills, in the video.
The air path is anything but homegenous, with wind, Mie scattering from dust, molecular Rayleigh Scattering from O2 and N2, and thermals ALL contributing to the noise.
The LED does better in signal to noise ratio because its wider optical bandwith ensures there are more optical paths to overcome localized diffraction.
Steve
The air path is anything but homegenous, with wind, Mie scattering from dust, molecular Rayleigh Scattering from O2 and N2, and thermals ALL contributing to the noise.
The LED does better in signal to noise ratio because its wider optical bandwith ensures there are more optical paths to overcome localized diffraction.
Steve
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