An OTDR is an optoelectronic instrument that uses time-domain reflectometry to characterize and locate faults in optical fibers The underlying idea is so send a short pulse into the fiber and "listening" to any echoes coming back from it. An OTDR injects a series of optical. The Optical Time Domain Reflectometer (OTDR) was developed precisely for this environment. in cable TV, LAN, metropolitan networks or long-haul. metry (OTDR), covering its principle, impl e an essential tool for: characterisation, certification, maintenance and monitoring optical networks. from Hughes Research Laboratory in 1976 (Barnoski and Jensen 1976), and then Stewart D. Personick proposed the concept of.