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Spooky-Manufacturing / PicoTimer

PicoTimer is an open-source and open-hardware project that enables you to trigger multiple circuits with pico-second accuracy.
GNU General Public License v3.0
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optical beam vs. transmission line? #1

Open sbourdeauducq opened 4 years ago

sbourdeauducq commented 4 years ago

Why is a light beam better than a (cheaper and easier) RF transmission line with a splitter? The fully-electrical solution can even easily produce sharper edges than the optical transducers (laser diode turn-on time, capacitance of the photodiodes, etc.), and if you use the same semi-rigid coaxial cable everywhere there is no difference in propagation time (I suspect not worse than those caused by e.g. the changing index of refraction of air with temperature and pressure in the optical case). If you use a mercury-wetted reed relay you can get very sharp rise times in a simple way.

NoahGWood commented 4 years ago

Hi @sbourdeauducq, I apologize for the delay in response as I've been very busy with a variety of projects to assist with covid relief.

Part of the problem we were having with a wire solution was that electricity travels at close to the speed of light, but not quite as fast. Our goal was to make this as inexpensive to implement as possible, but the maths showed we'd need to have a few nanometers difference in wire lengths between the components to achieve the desired accuracy. This would mean we need to have very finely tuned manufacturing processes to implement, whereas with the extra few thousand m/s you get from using light you're able to use fiber optics with length differences of a mm or so for the same accuracy.

Either way will work, but it's been my understanding that the least expensive and complex method would be the optical, I'd be very interested in reading more about your proposed method though if you have a better way to do this!

Thanks for taking the time to raise this issue :)