About 20yrs ago all of our cad terminals used fiber to carry the analog RGB signals from the mainframe to the workstation CRT's. One fiber for each color and one for the kbd/tablet and terminal text.

Over several years a number of the fibers were broken eventually using up all the spares. Every one assumed it was the pigtails coming out of the drops that had been broken from mishandling.

It was a surprise when the OTDR showed that all the breaks were due to failed splices inside a closed junction box.

It was the first I had heard of or seen what a TDR could do. Seemed magical. The unit in use had a crt and a paper tape output. Even used on a good fiber the tech could spot where every splice was all the way back to the other end. He even showed how bending a fiber a little to sharply could be seen.

Those workstations were insanely priced $25k for a desk an rgb monitor, digitizing table, keyboard and a circuit card that mapped the terminal text on top of the graphic display. Today it's almost impossible to spend more than half that much on a high end PC workstation including all the compute power, which the old cadds workstation totally lacked.