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I think lolc was referring to optical links in space specifically — no radio involved. No fiber necessary (or possible) because of line of sight.
by zamfi 9y ago
I think lolc was referring to optical links in space specifically — no radio involved. No fiber necessary (or possible) because of line of sight.
- cbhl 9y agoAn earth-to-space optical link would still suffer from diffraction, right? As I understand it, this is also the same reason why it's dangerous to point laser pointers at airplanes.
- dreamcompiler 9y agoIt's dangerous to point lasers at airplanes because laser light doesn't decrease as 1-over-r-squared. Which means the human pilot can be temporarily blinded by the beam, even many miles from the source. It has nothing to do with diffraction.
- cbhl 9y agoThanks for that explanation!
- jakobegger 9y agoThis is incorrect. Laser beams are only "straight" at short range. At long range, laser beam intensity does decrease as 1/r^2. The reason for that is that the diameter of the laser beam increases due to diffraction. If you want to know why, I recommend reading about Gaussian beams and Rayleigh Range.
- tinus_hn 9y agoIt’s dangerous to point lasers at planes because if you hit the window the light scatters and illuminates the complete window, blinding the pilot. There are videos on YouTube if you want to see what it looks like. It isn’t like you’re pointing directly into the pilots eye, the chances of that are rather slim.
- Boxxed 9y agoWhat exactly does it mean to have an optical link in space that's not a radio? Radiowaves are light, aren't they? Is this just semantics in regards to light near the visible spectrum vs not?
- bdamm 9y agoFrequency matters; masers are much more challenging than lasers, for example. But in any case, a direct laser link can carry enormous amounts of data. Even indirect LED transmission has been shown to viably carry many Gb/s. The challenge, of course, is the aim. It's not that easy to hit a pea that's several thousand of km away. I imagine feedback aiming systems where the vessels steer each other's transmitters, but that requires some amount of surface area for reception and that part doesn't scale as easily as fibers do.
- jakobegger 9y agoDiffraction affects laser beams just like all other radiation. You can't just focus a laser beam on a pea over a distance of 1000km. (well, theoretically you could, but you need a 20m parabolic mirror to focus it)