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11

If you can control its emissions, and detect it, then you can use it for communications. X-rays are no exception. However there are many reasons they are not widely used, including expensive and limited optics, short distance line of sight outside a vacuum, and not as safe as many other forms of communications. Still X-rays have some uses and there are X-...


4

Technically speaking, frequency modulation of light would involve shifting the color since, if you look at the EM spectrum, you basically see a rainbow in the visible part of it from red (lowest frequency) to violet (highest frequency). If you wanted to, you could take the original signal, run it through an analog-to-digital converter, and do the ...


3

Hams have played with visible light communication for ages. Near-UV is pretty similar to visible light, so you could do the same sort of experiments, you can easily buy good LEDs and photodiodes in the UV range. There might be less ambient noise than in the visible and IR ranges, but there will be more atmospheric absorption. Do a bit of searching for ...


3

There exist tunable lasers, where the output frequency can be modulated. And there exists such a thing as an acousto-optic modulator though I'm not sure if those are used to actually modulate the frequency of light. Or a more D.I.Y. method could be: shine a narrow beam of continuous spectrum light (e.g. incandescent light) through a prism. Then capture a ...


3

What you will want to do is not just concentrate on the receiver, but also the transmitter. For the receiver you will want a lens to focus the signal from the transmitter down to as tight a point as possible. 2.7 miles means your light will be near enough parallel once it hits the lens*. If you have a 5cm (for example) distance between the LED and the lens, ...


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