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Light for data transmission

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Bern1937

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I am looking for ideas and suggestions on using light for data transmissions. Range will be up to 500 feet, during daylight hours, and outdoors. Want to use relatively common LEDs and diode detectors, due to pricing. The sending end will be moving and sending out light 360 degrees. The receiving end will have a very basic and crude tracking system, so possibly a very simple and broad focus lens can be used. What I am looking for is thoughts on what color of light to use. Since there will be high ambient light can I use a certain color/frequency and some type of filter to get a better signal to noise ratio than if I just use white and a sensor that will look at all the background light? --- Also has anyone been able to get this amount of range, using simple systems without the use of elaborate lenses?
 
I wont disagree with ronsimpson. Personally, I don't know if it is possible, but it does seem difficult. My gut feeling is that in order to have any chance of making this work you will need narrowband light source (laser edge emitting LED or superluminescent LED instead of standard LED), and then use the proper narrow band optical filter. Then, you may still need electrical modulation and electrical filtering to reject DC ambient light that gets through the filter, and perhaps even phase detection (PPL) to provide extra discrimination. Data rates will likely be limited too, even if you can get the concept to work.
 
I have a device that shoots a beam of light across my driveway to see if a car is on the road.
It uses elaborate lenses. IR light. Does not transmit 360 but more like 1 degree. Uses IR filters.
The data rate is very very slow. Indoors it reaches out a long distance. Outdoors, not 500 feet, not 50 feet, but 25 feet if the sun is high. If the sun is low and shinning on the lenses it does not work at all.
 
Yeah, it seems that the main issue is going to be the small optical power that will arrive at a photodetector 500 ft away if the beam pattern is omnidirectional. I think if the power level is brought up significantly, then the various known techniques can work to filter DC ambient light. But practically, a laser and directionality are going to make it much more feasible.
 
Your constraints are very tricky.

At first I was thinking infra red laser, but you want 360 degrees, and standard parts, infra red leds might get 30 feet in daylight.
You might be better with radio than light.
 
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