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The Dunant subsea cable

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Re: The Dunant subsea cable

#191

Post by wmf »

potiuper wrote: post #172
rorykoehler wrote: post #142

Earlier quoted context omitted.

How deep would this bore tunnel be at the centre most point if it was perfectly straight? Would it go into the mantle?

d=r(1/cos(s/(2r))-1)=3958(1/cos(6906/7916)-1)~=2198 mi; Yes, into the lower mantle with only 692 mi to go to the outer core. What I would love the internetz to explain is how to justify the h8 for HFT, yet the luv for Musk since he is the one in the driver's seat at the moment for this stuff with StarLink and the Boring company.

Because HFT helps the rich AF get richer but Starlink benefits normal people?

Re: The Dunant subsea cable

#192

Post by LargoLasskhyfv »

extropy wrote: post #73
idlewords wrote: post #58

Earlier quoted context omitted.

You gotta bore for that sweet latency win. A chord tunnel between San Francisco and Hong Kong would save 1300 miles (20% improvement right there), and if you drill it straight enough, you won't even need a cable.

Need to have lava shields for that.

Who cares? Would be totally worth it because of unlimited geothermal energy!

Re: The Dunant subsea cable

#193

Post by crispyambulance »

sp332 wrote: post #146
crispyambulance wrote: post #104

Earlier quoted context omitted.

That's interesting! But multimode fiber isn't feasible for thousands of kilometers? This is transatlantic. Wouldn't that have to be singlemode just for the distances involved?

Even single-mode needs repeaters along the length of the cable to get across an ocean. I guess you could use multimode and a lot more repeaters, but that seems more expensive and more failure-prone.

Yes, and the SDM as described in the nature article in parent^2, it would require a something far more complex than a repeater (which in most cases is actually just a purely optical amplifier).

Current practice is to use erbium doped fiber amplifier or raman amp for boosting optical signal at long intervals for transoceanic runs. Given the complexity of spatial signal, I don't think a regular optical amplifier will work? I could be wrong, this tech is changing but submarine fiber-optics tech is necessarily conservative and slow moving.

Re: The Dunant subsea cable

#194

Post by alexhutcheson »

markphip wrote: post #31

I know there are many of these cables that have been around for years, but I am curious how are they physically secured? Especially where they transit from ocean to land? Is there some long underground/sea tunnel of conduit that the cable is routed through to the basement of some building? Or if you are walking along the beach somewhere is there just some cable running out of the ocean along the beach to some buildin…

http://dls.virginia.gov/commission/materials/subseacables.pd...

Re: The Dunant subsea cable

#195

Post by kstrauser »

jodrellblank wrote: post #69
idlewords wrote: post #58

Earlier quoted context omitted.

You gotta bore for that sweet latency win. A chord tunnel between San Francisco and Hong Kong would save 1300 miles (20% improvement right there), and if you drill it straight enough, you won't even need a cable.

Alameda enterprises excited by rumours of new chord tunnel Thursday, low latency burrito delivery futures up 5%.

Currently posting from Alameda. If you cause a local surge in demand that means I have to outbid a Manhattanite for a good burrito, I will cut someone.

Re: The Dunant subsea cable

#196

Post by LargoLasskhyfv »

mmmBacon wrote: post #164
O5vYtytb wrote: post #56

Earlier quoted context omitted.

My bet is on tech like Starlink with inter-satellite communication. Starlink should have lower latency with space lasers compared to fiber.

Starlink satellites are in orbit 550km high. So any journey would add at least 1100km. Moreover not sure that a single satellite would be able to hit another one across transpacific distances and may need to go through multiple hops to get there. Each hop will add latency since signal needs regeneration. So it’s not clear to me a swarm of satellites is a real winner from a latency POV. Furthermore, given costs to put…

Are you sure about the necessary regeneration? Let me hand wave from the dark skies here for a moment:

1.) Think of the precision mirrors in the so often mentioned EUV-lithography equipment from ASML for latest generation chips from TSMC.

2.) Now imagine something like that on board of a satellite, maybe smaller.

3.) Have 2.) moveable with sufficient precision to bounce the rays from satellite to satellite in realtime, without having to regenerate them in any way for about 4 to 5 hops.

4.) problem solved by purely 'optical' mesh while signal is 'in orbit'.

kthxbaiiii!

Re: The Dunant subsea cable

#197

Post by jamessb »

imoverclocked wrote: post #188
jamessb wrote: post #181

Earlier quoted context omitted.

But the correct statement is "no more than" not "at least". Consider a right-angled triangle with base length d and height 550, corresponding to transmission from a base-station to a satellite. The hypotenuse has length sqrt(d^2 + 550^2), so the difference in length between the hypotenuse and base is sqrt(d^2 + 550^2) - d. This has a maximum of 550 when d=0 (i.e., shooting straight up), and decreases as d increases:…

Are all base stations directly underneath a satellite? I think this is an over-simplification if we are chasing pedantics; There are cases where it will be more and others less so the slightly more precise wording might actually be "about 1100km." To the larger picture: it seems we often lose that order of length on the ground due to existing network topologies and geographical limitations.

Yes, this is an oversimplification: the original statement seemed to be based on getting a fact about trigonometry backwards, and I was just trying to resolve the underlying confusion.

Re: The Dunant subsea cable

#198

Post by koheripbal »

potiuper wrote: post #172
rorykoehler wrote: post #142

Earlier quoted context omitted.

How deep would this bore tunnel be at the centre most point if it was perfectly straight? Would it go into the mantle?

d=r(1/cos(s/(2r))-1)=3958(1/cos(6906/7916)-1)~=2198 mi; Yes, into the lower mantle with only 692 mi to go to the outer core. What I would love the internetz to explain is how to justify the h8 for HFT, yet the luv for Musk since he is the one in the driver's seat at the moment for this stuff with StarLink and the Boring company.

One of the important components of online hate is that it requires zero justification or logical consistency.

It just needs to feel gratifying.

Re: The Dunant subsea cable

#200

Post by LargoLasskhyfv »

BelenusMordred wrote: post #135
ceejayoz wrote: post #61

Earlier quoted context omitted.

This was done in the 70s/80s, but I doubt it's worth the effort now. It only worked because the Soviets assumed the cables were inaccessible. End-to-end encryption is a thing even for the general public now. Now we just compromise the servers/routers. https://gizmodo.com/the-nsa-actually-intercepted-packages-to...

> I doubt it's worth the effort now It's very much still happening. Metadata is enough for intel purposes, storage is ridiculously cheap and post-quantum breaks of key exchange is forever 20 years away like fusion. https://www.nytimes.com/2015/10/26/world/europe/russian-pres... https://www.theatlantic.com/international/archive/2013/07/th... https://www.zdnet.com/article/spy-agency-taps-into-undersea-...

https://nationalinterest.org/blog/the-buzz/exposed-the-us-na...

https://www.forbes.com/sites/hisutton/2020/08/19/how-russian...

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