[controversial97]

I might be totally wrong; It seems likely to me that, due to capillary action, if a hollow undersea fiber gets physically cut then seawater would flow into the hollow center.

The ends of the fiber might be at different depths with a pressure difference that could move water a long way into the fiber. I imagine the length that water got into would be ruined even if the water was pushed out again.

I conjecture that undersea hollow-core might end up being expensive to maintain.

[esoterae]

IIRC individual fibers are terminated every Nkm at a repeater. Not that it wouldn't be spendy, but I would also conjecture replacing a segment of fixed length instead of just gluing the ends back together might still be a reasonably strong constraint on unplanned repair cost (and also probably providing a pretty strong lower constraint as well--notably higher than solid core).

[xhrpost]

I don't think they are terminated every Nkm anymore. We have been able for quite some time to re-energize the signal directly in the optical core without needing to convert it to electric then back.

https://en.wikipedia.org/wiki/Laser_pumping

[oakwhiz]

If a cable is long enough to require amplifiers, they are spliced in. Couplers/circulators need to be in line with the doped section of fiber that forms the laser amplifier, both before and after. One of the couplers injects the pumping beam from another laser into the doped section. This necessitates splicing at every amplifier. Also, almost every strand in the cable would require amplification.

In addition there are feedback, failover and monitoring functions that require more optical components to be included, and it's likely that this type of functionality will increase as demand for improved latency and reliability increases, and new cable networks are built.

[LargoLasskhyfv]

I may be even more wrong, but maybe this leads to a more modular way of building/laying these "cables".

I imagine that you need less of them, because "faster" also means longer range until attenuation kicks in. How much more range/less amplifiers compared to current state of the art I don't know. I'd think it should be possible to lay down a new part the whole length between two amplifiers/laser pumps/couplings/ and "plug" it in by remote controlled submersibles, instead of lifting up the broken ends, and "splicing" it on the ship. Like pre-made Cat-5/7 with RJ-45 plugs, so to speak :-)

[oakwhiz]

Cables like this would have spare strands to be able to handle the situation in which a single strand was compromised by a break or pinhole, and possibly a different type of jacket on each strand to manage the stresses. If a section is badly damaged beyond the point of patchwork repair, then the only hope from that point is that the customers using the strands/wavelengths on the cable have an active alternate path while the whole section is dug up and replaced.

[dtgriscom]

If there's a leak that would allow water access to the core, the signal's already gone.

And, a hole that small in a block of glass could withstand a titanic amount of pressure.