When I was working at RayNet (then a division of Raychem), the entire work they were doing was based on both injecting and detecting signals into and out of fiber optic cables. They did it by bending the cables around a radius, and if done correctly you can make things work quite well. We were developing "fiber to the curb" to have nice digital signals get there. Now days, DSL is used, and they have remote terminals for both the data and the voice.

Things change over 20 years! What used to be OK (8kHz data for voice), is nothing compared to 3MHz+ coming into your home. Oh, well.

Yes, submarines did tap a cable as discussed.