Kazumara

joined 1 year ago
[–] Kazumara@discuss.tchncs.de 2 points 3 months ago

Wow interesting! Thanks for checking the label!

[–] Kazumara@discuss.tchncs.de 3 points 3 months ago

Yes, and that's before muxing!

I need only 75 GHz of spectrum to send 400 Gbit/s through our country. We've currently got a link running between Zürich and Lugano (two amplifier sites in between, before and after the alps), and I've got 4400 GHz of usable spectrum with our currently deployed system, so if we needed it and spent like two million dollars we could deploy 23.2 Tbit/s within months, using just our normal commercial stuff, on a single fiber pair.

[–] Kazumara@discuss.tchncs.de 2 points 3 months ago* (last edited 3 months ago)

Using G.657.A2 fiber you could get away with 7.5 mm bend radius, or 15 mm diameter, for the innermost layer of the spool. That's around 5/8 inch for freedom units.

But then again if you went that tight you'd need like 56'000 windings for 10 km. That sounds like a fuckton, and like we can't ignore the outer diameter being larger.

Approaching it from the other side: The fiber diameter with coating but without any mantle is 0.25 mm. If you want to put 10 km on a 100 mm long spool you could put in 400 layers lengthwise, and each layer would have to be a spiral of 25 m (of course you'd spool it outside in, not layer by layer, but should be mathematically similar enough). Using this spiral calculator and some random changing of the values it looks like an outer diameter of 91 mm (3 & 5/8 inch), and inner of 15 mm and a thinkness of 0.25 mm would work for a 25 m spiral.

Or if we go for 125 mm drum length, so 500 layers, with 20 m each we get 82 mm (3 & 1/4 inch) outer diameter.

Or if we go for 150 mm drum length, so 600 layers, with 16.7 m each we get 75 mm (3 inch) outer diameter.

So yeah I think your estimate was pretty spot on, if the 10 km length is the right assumption.

[–] Kazumara@discuss.tchncs.de 2 points 3 months ago* (last edited 3 months ago)

Today's wires aren't actually wires, they are optical fibers. It must be G.652 or G.657 from telecom use, since that's commercially available en masse. I think most likely would be G.657.A2 because that can be bent tighter. Here's an example data sheet from a random google search. I wrote it in a different comment already, but the core has 9 micrometer, the cladding 125 micrometer and the coating 250 micrometer diameter. For telecom applications you'd add at least a mantle, or more likely use a cable with many fibers in little pastic tubes wrapped around a metal core for stability, 12 x 12 is fairly standard. Here of course it's just a single fiber without mantle being spooled off.

[–] Kazumara@discuss.tchncs.de 4 points 3 months ago (2 children)

Bidirectional transceivers (so both directions on a single fiber) can do 100 Gbit/s ethernet too. No way you'd do that for drones of course, but just to show how far you can get with a single fiber.

[–] Kazumara@discuss.tchncs.de 3 points 3 months ago (2 children)

bend the fiber around a pencil and only experience degraded signal

Interesting. Are you using G.657.A2 then?

[–] Kazumara@discuss.tchncs.de 17 points 3 months ago* (last edited 3 months ago) (1 children)

Those news are already not so new any more. We've had reports of those two months ago.

Since fiber optic wire guided missiles exist it's not that much of a leap to think it should work with drones too, so long as the weight works out.

Fiber is really really thin. 9 micrometer core diameter and 125 micrometer cladding diameter (incl core) and 250 micrometer coating diameter (incl core, cladding). The 10 km spools we use in our lab for network equipment testing are boxes of only like 20x20x10cm, and those aren't optimized to be extra small with bend insensitive fiber. I can totally believe the 1.2-1.4 kg for 10 km in the article.

Edit: leak -> leap

[–] Kazumara@discuss.tchncs.de 13 points 3 months ago

I thought they were threatening him with flowers? He must be reading too much into it.

[–] Kazumara@discuss.tchncs.de 2 points 3 months ago

dine in but order online?

This exists. A Mexican and an Asian chain here in Zürich do this.

[–] Kazumara@discuss.tchncs.de 36 points 3 months ago (4 children)

By the way, only some concentrations camps in Nazi Germany were exterminations camps. So even without any mass murder this can easily be regarded as equivalent in function to a concentration camp.

[–] Kazumara@discuss.tchncs.de 26 points 3 months ago (2 children)

Still can't believe this stupid liar became governor

[–] Kazumara@discuss.tchncs.de 1 points 3 months ago* (last edited 3 months ago)

Ah, yes it's for personal use, true. But the meaning of personal item as it relates to customs means an item that you take with you on the travels for your own use, so the assumption is that it leaves and re-enters your country with you. So that there is no net export or import involved. Here's the definition my government provides (helpfully even available in English).

My claim, if asked, would have been, that I always use two phones and I just took both with me when I went to Germany and then obviously took both back to Switzerland.

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