[iptrans]

Fortunately you only need repeaters every 80 km or so, so you'd only need a bit over a hundred repeaters across the 9000 km span.

Repeaters aren't terrible expensive, so they only add a few million to the total cost.

[eitland]

Checked your profile now, I belive it :-)

[jaytaylor]

And how are potential repeater unit failures accounted for?

[iptrans]

Repeaters are designed to last for the lifetime of the cable plant. Design lifetimes are 25 years or so.

Repeater design is inherently very, very conservative because if the repeater fails, the cable fails. This results in an outage lasting days, if not weeks, as a cable ship is dispatched to the failure location.

The cable ship has to trawl for the cable and pull it up to the surface. Then the cable is cut and replaced with a new section that includes a new repeater to replace the failed one. Expensive.