How pressing of a problem is the quality of optical fiber? Something tells me tells me that even if you imagine that all the capacity already existed, the mere shipping of raw goods up and finished goods down would probably eat any marginal profits over earth-manufactured fiber.
For regular data transmission, I can't imagine it to be worth it - far bigger gains could be made by just making repeaters smaller and cheaper by iterative design improvement.
Perhaps there are scientific uses where loss in fiberoptics makes a project infesible? Or perhaps quantum entangled photons, which one can't amplify?
I suppose the issue is no matter how small and cheap the repeaters get, they will still need power, backups, replacements and all the complexity that implies.
I also have a feeling I've read the power needed for the repeaters generates magnetic fields that attract sharks. Shark bites are a not entirely trivial source of fiber cuts, which require very expensive fleets of cable repair ships to be maintained on standby and simply driving down the number of fiber cuts could be a fairly significant source of cost savings.
