I thought the point of fibre was that it was low noise ...
EDIT There's a good discussion of what you're talking about here [0]
Upon further reading, there's a such thing as an all optical regenerator which would appear to provide the best of both worlds, though there's nothing here about how widely these are used [1]
[0] http://www.rfwireless-world.com/Terminology/Optical-Repeater...