If you sink a few old ships around in the area you will never need to repair it again each two years. Extra bonus if they are exactly the same ships that you found red-handed damaging the cables.
PoignardAzur 5 hours ago||
tl;dr: They pull the damaged cable up, weld it to a new section of cable their brought, and then drop the cable with a detour to make room for the extra length.