I'm certainly no expert here but I'm guessing it doesn't make sense for two reasons: 1) Modern communications fibers are complicated (https://en.wikipedia.org/

I'm certainly no expert here but I'm guessing it doesn't make sense for two reasons: 1) Modern communications fibers are complicated (https://en.wikipedia.org/wiki/Submarine_communications_cable https://en.wikipedia.org/wiki/Submarine_communications_cable [1]) and presumably expensive so speculatively adding them to power cables would likely be a pricey endeavor. 2) AFAIK most submarine cables are systems — e.g. a ring the connects various places so that there are two paths between points — so trying to plan one to that co-opts existing bits of fiber piggy-backed on power probably wouldn't be easy. Also you'd have the issue of dealing with different generations of fiber, standards, etc. [1] On reading this it turns out that modern fibers actually carry power as well so that repeaters en route can be powered.