Submarine cable cut identification

Shore stations can locate a break in a cable by electrical measurements, such as through spread-spectrum time-domain reflectometry (SSTDR).
SSTDR is a type of time-domain reflectometry that can be used in live environments very quickly. Presently, SSTDR can collect a complete data set in 20 ms.
Spread spectrum signals are sent down the wire and then the reflected signal is observed. It is then correlated with the copy of the sent signal and algorithms are applied to the shape and timing of the signals to locate the break.

Disclaimer: As obtained from the Internet