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Subsea Cable to Connect Asia, Europe, and North America Through the Arctic

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Re: Subsea Cable to Connect Asia, Europe, and North America Through the Arctic

#31

Post by troymc »

jsjohnst wrote: post #21
mhandley wrote: post #18

Earlier quoted context omitted.

Starlink gets the speed of light in a vaccuum, which is roughly 50% faster than the speed of light in glass.

Fiber gets closer to the speed of light, even when accounting for retransmission delays, than just 50%. The index of refraction for glass is commonly quoted as 1.5. That makes it 33%. Also, Starlink isn’t vacuum speeds either (unless you are talking about the inter satellite laser links and not the downlink to CPE, which even they I’m not sure operate at full “speed of light in a vacuum”).

The refractive index of air is very close to that of vacuum (which is 1), so most Starlink transmissions between nodes (ground-satellite, and satellite-satellite) will travel at near light speed.

Re: Subsea Cable to Connect Asia, Europe, and North America Through the Arctic

#32

Post by wallacoloo »

zamadatix wrote: post #24
jsjohnst wrote: post #21

Earlier quoted context omitted.

Fiber gets closer to the speed of light, even when accounting for retransmission delays, than just 50%. The index of refraction for glass is commonly quoted as 1.5. That makes it 33%. Also, Starlink isn’t vacuum speeds either (unless you are talking about the inter satellite laser links and not the downlink to CPE, which even they I’m not sure operate at full “speed of light in a vacuum”).

The refractive index is only one part of the story, light does not follow a straight path through fiber it bounces around. I'd assume this to be about the newer inter-sattelite links as comparing fiber to fiber plus some seems obvious.

> light does not follow a straight path through fiber it bounces around.

this is only relevant for multimode fiber, right? in singlemode fiber the light must propagate parallel with the fiber. even in multimode fiber, some light is parallel, so it doesn’t necessarily limit latency — it creates dispersion.

Re: Subsea Cable to Connect Asia, Europe, and North America Through the Arctic

#33

Post by zamadatix »

wallacoloo wrote: post #32
zamadatix wrote: post #24

Earlier quoted context omitted.

The refractive index is only one part of the story, light does not follow a straight path through fiber it bounces around. I'd assume this to be about the newer inter-sattelite links as comparing fiber to fiber plus some seems obvious.

> light does not follow a straight path through fiber it bounces around. this is only relevant for multimode fiber, right? in singlemode fiber the light must propagate parallel with the fiber. even in multimode fiber, some light is parallel, so it doesn’t necessarily limit latency — it creates dispersion.

Singlemode is designed to minimized modal dispersion but it still occurs, especially over the longer distances including from stresses in the core rather than traditional bouncing. First photon isn't as important, it's the signal peak that matters as the receiver will try to decode from that. Typically this latency is hidden by needing repeaters every ~60km anyways due to both dispersion and loss. I'm not sure how far apart Starlink inter-satellite can repeat and if they can "skip" satellites as long as there is a clear direct path to another farther along the path, I haven't been in contact with their engineering folks since I changed jobs last year and am no longer a corporate customer.

Re: Subsea Cable to Connect Asia, Europe, and North America Through the Arctic

#35

Post by edoceo »

jvmiert wrote: post #6

For anyone curious, there's an image of the route in this article: https://www.aroged.com/2021/12/24/far-north-digital-and-cini...

That article has the same ad like a dozen times in a row, and also what is clearly JavaScript leaking out around them. Cool visual but what a sloppy site.

Re: Subsea Cable to Connect Asia, Europe, and North America Through the Arctic

#37

Post by jsjohnst »

dghughes wrote: post #25
mhandley wrote: post #18

Earlier quoted context omitted.

Starlink gets the speed of light in a vaccuum, which is roughly 50% faster than the speed of light in glass.

From what I understand Starlink satellites do not communicate between each other yet, maybe that's outdated info. I know there will be inter-sat comm eventually. But they are 500km in altitude and the atmosphere is 100km so they only have about 400km of vacuum from obit to Earth stations. So it's a 1,000km round trip and then through ground stations, fibre cabling.

> From what I understand Starlink satellites do not communicate between each other yet, maybe that's outdated info.

It’s always been wrong. By design the Starlink satellites communicated with each other. Too cost prohibitive and infeasible in other ways to have a ground station covering every satellite.

Re: Subsea Cable to Connect Asia, Europe, and North America Through the Arctic

#38

Post by jsjohnst »

troymc wrote: post #31
jsjohnst wrote: post #21

Earlier quoted context omitted.

Fiber gets closer to the speed of light, even when accounting for retransmission delays, than just 50%. The index of refraction for glass is commonly quoted as 1.5. That makes it 33%. Also, Starlink isn’t vacuum speeds either (unless you are talking about the inter satellite laser links and not the downlink to CPE, which even they I’m not sure operate at full “speed of light in a vacuum”).

The refractive index of air is very close to that of vacuum (which is 1), so most Starlink transmissions between nodes (ground-satellite, and satellite-satellite) will travel at near light speed.

> The refractive index of air is very close to that of vacuum

Yeah, 1.0003 vs 1.0. Very close, but not the same was my point.

Re: Subsea Cable to Connect Asia, Europe, and North America Through the Arctic

#40

Post by ksec »

Is this Cable specifically for connection to go from EUR to JAP without going through China?

I am wondering if this is made possible only because of the melting ice cap, where the "possibility" of travelling through the arctic is now a low cost issue. I am also assuming once the cable are laid, it doesn't make much of a difference whether the surface is Artic or Pacific? I am assuming the sea floor is roughly all the same.

And why aren't Greenland better connected? The only immediate upside I see is the Iceland Connection. Considering they have possibly the Greenest Datacenter on the planet. ( I do wonder how do they protect against Earthquake ? )

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