Some questions I’ve wandered about that I’m not able to understand
1. How do they avoid data loss considering that the probability of interferance across such long distance is extremely high
2. How are those cables phisically supported, and built to be able to sustain damage by corrosion, abrasion, animals, tides, etc
3. Who builds them and how is it profitable
In: Engineering
1. Why do you think the probability of interference is extremely high? Fiber optic cables are extremely “clear” with virtually no interference. They’re not perfectly transparent though, so at various intervals there are optical amplifiers to boost the signal. They receive power through power wires laid along with the fiber optics and generally only need to be placed at intervals of many tens of kilometers or more.
2. In the deep ocean, they are laid on the seabed and are usually minimally protected since there’s very little that can damage them. In shallower waters where there is greater risk of damage from anchors and whatnot, they’re either clad in more protective layers or buried in the sea floor or both. The [Wikipedia has a good image](https://en.wikipedia.org/wiki/Submarine_communications_cable) of such a cable. In the event that the cable is broken for whatever reason, the operators are able to determine the location of the fault, send a repair ship that can locate the cable, haul it up from the seabed, repair the fault, and return it back to where it was before.
3. Typically they’re owned by one or more private companies (usually major global internet providers like AT&T, Tata Communications, etc., but also companies like Google) and laid be specialized cable-laying ships. Those ships can be owned by the cable owners or are contractors. Some cables are owned by governments. Cable owners lease access to the cables to various other network providers and carry traffic for them in exchange for money.
1: Depends on the cable. Modern fibre optic cables don’t suffer from loss but can be interfered with. Sharks chewing on them seems to be a problem. But they do suffer from faults and faults aren’t uncommon. Fishing interference is the biggest cause of faults.
2: They don’t just drop a wire. It is surrounded by a lot of protection. This [link](https://www2.telegeography.com/submarine-cable-faqs-frequently-asked-questions#:~:text=How%20thick%20are%20undersea%20cables,layers%20of%20insulation%20and%20protection) explains how they’re constructed and laid.
3: Many companies. BT AT&T (and other telecoms from other nations), Facebook, Microsoft, Azure, Global Cloud Exchange and many more. Some companies group up. And if telecoms companies want to be able to transfer data – and they obviously do – then they have to pay to use the cables. Like shipping companies and their ships. The cables were worth $17 billion in 2023.
The lines are typically laid across the bottom of the ocean, and are heavy enough that they’re not going to be significantly affected by tides or currents or things like that. These days they’re often buried as much as is possible.
A very small percent of their cross sectional area is actually dedicated to the parts that carry data, much of the rest is various layers designed to protect the data carrying parts at the center. This typically includes metal tubing and a winding of steel cables, as well as multiple water proofing layers.
Deep down in the sea, there’s not much in terms of interference, especially because these days the cables tend to be fiber optic lines that use light to transmit the data.
Various telecommunications companies and other industry groups are usually the ones who pay for them, sometimes governments, and they can charge money to other companies that want to send data across them.
As end users, we generally don’t see any specific costs of bandwidth because we just pay rates to our cable company or phone carrier or whatever, but the ‘backbones’ of the internet have a whole system of contracts and agreements between the various companies that manage them and provide the bandwidth to keep the internet functional.
1. It actually used to be very lossy and we’d compensate by using loud and slow signals. Today we use fiber optic lines that are crystal clear for thousands of miles.
2. The cables themselves are about an inch thick and most of that thickness is just protective coatings for a hair thin fiberoptic line. We do have to pull them up now and then to fix them but we can also tell where the break in the line is based on how long it takes light to bounce off the break.
3. Large and specialized private companies. The biggest 3 are Global Marine Group, Prysmian S.p.A, and Jan De Nul Group. As for the business model, whomever owns the cable can charge a fee on every bit sent through it.
Really, really good, very lengthy article from Wired.com:
https://efdn.notion.site/Mother-Earth-Mother-Board-WIRED-a8ff97e460bc4ac1b4a7b87f3503a55c
Many years old, but still instructive and entertaining.
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