On Wed, 16 Dec 2020 04:09:55 -0800 (PST), John Walliker wrote:

On Friday, 11 December 2020 at 01:08:38 UTC, Graham. wrote:

Are the submarine fibre optic cables vulnerable? If so, what's the
mechanism?

Long-distance submarine fibre-optic cables have repeaters which are
powered by high-voltage dc supplies at each end. Induced voltages
in the power conductors might, in principle, cause problems.

Induced how? From sunspots? Salt water is a conductive medium so
should shield most of the length. All a bit like the hydrogen scare
in the 1980s.