@gregvp Hi gregvp, thanks. The wire moves both axially and radially. It is being reeled and unreeled continuously. About 100 inches per second axially, much slower radially. It moves about 30 feet, close to its full length. It is a stranded wire, about 1mm thick. It's in a very accessible place. No such big environmental considerations. It doesn't connect anything, everything can be altered except the wire itself. It is not possible to inject a signal because I can't cut into its protective coating, just to avoid the coating stripping off during such a long test. It doesn't carry any signal, it's just part of the physical device. It has an aluminum testing apparatus that we can alter in any way. We just need to know when the wire breaks, if it ever does.
Thanks for your interest in this problem. I'm hoping this helps give people any ideas that might be feasible. I think we might try a laser but I'm concerned the receiving window will be too small. We'll see though