Sort of unrelated, but a very interesting application of TDR on cables: in military, infrastructure, and certain other installations, a common security measure

Sort of unrelated, but a very interesting application of TDR on cables: in military, infrastructure, and certain other installations, a common security measure is a fiber optic cable woven into the chain-link fence or shallowly buried. Any deflection of the cable (e.g. due to a person climbing the fence) results in a subtle reflection in the cable. By knowing the layout of the embedded cable, not only can the event be detected, but it can be localized and used to e.g. trigger automatic pan of PTZ cameras. A major brand-name for this system is FiberPatrol but there are several vendors. Unfortunately it is rather false-positive prone when applied to fences, significant wind loading can cause the chain-link to lash back and forth and repeatedly deflect the cable. The resulting alarm fatigue was implicated in the somewhat (in)famous case of the nuns as site Y-12. Nonetheless this application is very common at federal installations and also certain non-federal infrastructure installations, e.g. the legacy iron fences around Portland, Oregon's surface water reservoirs (where remote-controlled PTZ cameras appear to be used for rapid remote confirmation of FiberPatrol detections... you can give the fence a shake and watch a camera pan to you almost immediately).