The Optical Time Domain Reflectometer (OTDR) is useful for testing the integrity of fiber optic cables. For every fiber optic cable plant, you need to test for continuity and polarity, end-to-end insertion loss and then troubleshoot any problems. If it's a long outside plant cable with intermediate splices, you will. Splices are critical points in the optical fibre network, as they strongly affect not only the quality of the links, but also their lifetime. It can verify splice loss, measure length and find faults.