Damn, how big is a 41km spool of fiber optic cable?
this post was submitted on 27 Jan 2025
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Messy napkin maths to explain this to myself, because it is wild to me that 41 km of anything fits in that. I will use the top picture and assume that the guy's hand is about the same size as mine; my hands are reasonably large, so this should err on the safe side, and his hands are at a similar distance from the camera to the spool. That gives me a very approximate scale of 2 pixels per millimetre.
Diameter of the spool case: 365 px = 183 mm = 0.183 m Radius of the main section of the case: 91 mm = 0.091 m Length of the main section of the case: 477 px = 239 mm = 0.239 m
Volume of a cylinder = pi r r l v1 = pi * 0.091 * 0.091 * 0.239 v1 = 0.00622 m^3
I will assume that the shaft of the spool is the same diameter as the narrow part of the case
Diameter of the spool shaft: 55 px = 28 mm Radius of the spool shaft: 14 mm = 0.014 v2 = pi * 0.014 * 0.014 * 0.239 v2 = 0.00015 m^3
Subtract shaft from first volume = 0.00607 m^3
I'll assume that the cable has the same volume, as if the case had zero-thickness walls and the cable filled the case perfectly. Since the cable has the same volume, dividing that volume by 41,000 m should give us the cross-sectional area.
0.00607/41000 = 1.48e-7 = 0.000000148 m^2
Square root of that to get the length and height of that cross section = 0.000345 m = 0.345 mm
This number can effectively serve as the diameter of the cable, since it'll have a circular cross section. And... yeah, I can find 0.25 mm diameter optical fibre easily, so the numbers check out.
I work in telecommunication and see fiber quite regularly.
It really is thin, and fine is a better word. In general what you see is the coating of the fiber, and that already is very fine. The fiber itself is nearly invisible even when you hold a strand between your fingers against the light.
A single of these nearly invisible fibers can transport a GBit/s into your home. βAny sufficiently advanced technology is indistinguishable from magicβ - yep, Arthur C. Clarke was right.
Funnily enough I have also worked with them, but all of mine were short lengths so I have absolutely no sense of scale for what kilometres of it looks like rolled up. Or had, I suppose, until now. I just used them to run light into awkward spots for sensors, though, so I wasn't exactly maxxing out the potential applications
By a neat coincidence I also play a bit of guitar, and a quarter millimetre is the diameter of the thinnest string on most of mine. For any other guitarists reading, a 10 gauge string is 0.254 mm
0.2mm is also a common layer height in 3D printing.
Having a hard time imagining commercial grade optic wire a quarter of a mm think surviving things like a mildly stiff breeze against some bushes or tree branches.
I suppose unless you're at the very end of the length of it, it can probably account for that to some degree by just letting more fibre out. This paper (which I have only skimmed, so sorry if I've got this wrong) seems to say that fibres even thinner than that β 0.15 mm β can handle a force equivalent to a couple of kilograms hanging off of them
Damn, fam did the math. Props.
And how much? Seems like it would be pretty pricey.
From what I've seen, they cost around 1-2k Dollars for 40 kms, probably cheaper if you buy in bulk. A single spool of 125 Β΅m fiber weighs around 3 kg but half of that is probably the spool itself.
Probably pretty reusable as well
Probably not as the drone would need to return home over the same route and that is a bad idea since then the enemy can follow the drone back with their drones.
often these drones are one way they can go farther without needing to save battery to get back and they can more out of the battery by overcharging it.
I was thinking of reeling in whatever cable survives the destruction after impact. It'd be easy enough to QC it after rewinding.
But yeah probably safer to abandon it
The cable is unlikely to be strong enough to reel it in by pulling, not to mentioned it would be tangled around things on the ground (including the cables from other drones). As such I think all attempts to retrieve it will fail because it breaks.
https://www.amazon.co.uk/Jeirdus-Launch-Singlemode-Measuring-Optical/dp/B07H5J2T5G
About 1500 EUR or USD. ItΒ΄s a spool 15cmx15cmx12cm, 1 kg. 6inx6inx5in, 2 lb for the metric impaired.
That's impossible. How can it be that small?!? They list the same dimensions regardless of which size spool you choose.
I work in telecommunication and see fiber quite regularly.
It really is thin, and fine is a better word. In general what you see is the coating of the fiber, and that already is very fine. The fiber itself is nearly invisible even when you hold a strand between your fingers against the light.
A single of these nearly invisible fibers can transport a GBit/s into your home. βAny sufficiently advanced technology is indistinguishable from magicβ - yep, Arthur C. Clarke was right.
Fly-by-wire FPV drones. Wild.
Post-war this is gonna be an interesting cleanup.
Right? I'm reminded of the lower dimensional floss covering the worlds in the 3 body problem series.