I know nothing of this type of engineering. How do you even start a project like this? Map the bottom of the ocean, figure out all the danger zones? What is the cost of doing something like this?
That is at least 1 order of magnitude cheaper than I would have guessed. Mind boggling that it's cheaper to do that then buy like the 4th best meal delivery app in Canada or whatever.
It's probably cheaper than people would expect because the long run across the deep ocean is a lot more straightforward than most people would expect.
1. For the deep ocean parts of the route, cables and associated equipment (such as repeaters) are simply spooled out from the back of the cable laying ship, to settle on the ocean floor.
2. For shallow waters, the cable is buried. This is done by dragging a plow along the bottom which cuts a furrow and puts the cable into it. The plow has an altitude control and a camera so that an operator on the ship can control it, and a magnetometer to check if the cable is properly buried behind it.
3. For areas where burying isn't practical but they anticipate ships will anchor, they use armored cable.
For #1, the costs are going to be the cost to operate the ship while it slowly spools out the cable and the cost of the cable. For #3, same thing, but with more expensive cable. For #2 I'd expect it is similar, except the ship goes a lot slower (about 0.5 knots when using the plow, compared to about 5 knots when laying surface cable).
Finally, there is this.
#4. At the shores, they need to avoid damaging reefs and other habitats, not wreck the beach, and things like that. The cable needs to be in conduits that are buried or anchored. And building those conduits needs to be done in a way that does not mess up the environment.
So what you've got then for a long cable project is two ends that present underwater construction projects, the shallow waters near the two ends where you have to bury the cable, and then the long deep ocean stretch where you are just spooling the cable out.
This suggests the costs are going to have a component that doesn't really depend on how long the thing is (the two ends and the shallow waters near the ends where burial is needed) and a component that is proportional to length (the long run between the two shallow waters near the ends).
At 5 knots, it would take about 1000 hours to lay the deep sea part of the cable. If the ship costs $50k/hour to operate, that would be about $40 million. (I have no idea what it costs to operate these ships, but Google tells me that big cruise ships cost about that much to operate, and I'd guess that a cable laying ship is cheaper).
Assuming the underwater cable itself is 10 times as expensive as regular cable, its about $150 million for 9000 km.
That's brings us to about $200 million for the deep ocean part.
> Assuming the underwater cable itself is 10 times as expensive as regular cable, its about $150 million for 9000 km.
Still sounds really inexpensive when I consider it contains a large number of repeaters and is meant to stay at the bottom of the ocean.
Edit: Forgot to write, I haven't run the numbers myself but I enjoyed your reasoning here, you put a smile on my face :
> At 5 knots, it would take about 1000 hours to lay the deep sea part of the cable. If the ship costs $50k/hour to operate, that would be about $40 million. (I have no idea what it costs to operate these ships, but Google tells me that big cruise ships cost about that much to operate, and I'd guess that a cable laying ship is cheaper).
I figure the hard engineering challenge is the repeaters. How do you build repeaters and power them, considering you can't really service or replace them ever over the lifespan of the cable (the deep ocean bits anyway)? A repeater every 80km is a whole lotta repeaters.
My estimate came to around $22k/kilometer for the cable itself plus the laying it in deep ocean. I didn't estimate the costs of repeaters.
The Google project was $33k/kilometer, so I don't think I could have been too far off on the cable itself. Looking at other undersea fiber projects, that seem about typical. For example, this one [2] estimated $27k/kilometer [1].
Here's an Alibaba seller with submarine fiber for $2000-9000/kilometer [2].
The submarine cables have an aluminum or copper tube around the fiber optics, an aluminum water barrier, and a sheath of stranded steel wires, and an outer polyetylene layer, with various other layers of mylar, polycarbonate, and petroleum jelly in between.
I'd expect the metal layers to be the most expensive parts. Looking at the cost of tubes or cables of those materials, it looks like each of those would be in the $1000-2000/kilometer range.
Yeah that's what I was thinking too. It doesn't sound like money well spent, it sounds like a bargain to me, like "you'd be stupid not to do it" cheap for something the size of Google.
That sounds like money well spent, and a good deal considering what it enables. It would be incredible to see the multiple levels of govt around the world collaborate to create a publicly funded (bond sales) project for laying fibre optic across the planet which could not be sold to a private corp, and that guaranteed access to it based on population proportion, not GDP.
The article is now almost a quarter century old and the cables have gotten better. In fact, even that cable probably got a lot faster after optical coherent detection was introduced, i.e. much more capable modems. But the way the cables are actually laid and especially the details of the shore landings and the issues of terrestrial runs, are as current as ever.
Pretty much, you do surveys, probably based on existing ocean floor sonography, and then contact out a cable to someone like NEC, TE SubCom, Huawei, etc… Load it up on a cable laying vessel, and use software like Makai Lay to optimally place the cable on the ocean floor. [This is the basic idea, I wouldn’t treat this as an authoritative answer, I’m just loosely adjacent to this industry]
While not being super technical, there is an interesting miniature "The First Word Across the Ocean" in the "Decisive Moments in History" book by Stefan Zweig. It tells the story and circumstances of how the first trans-atlantic cable (back then for telegraphs) was laid in the late 19th century.
The funny thing is, that when you realise that they just lay it down on the sea floor and you start to think through all the potential issues with throwing a very thick special cable on the ocean, you will realize that it already just works as it is for a while.
Their Oregon to Japan cable, 9000km and laid in 2016, cost $300M.
https://www.computerworld.com/article/2939316/googles-60tbps...