Download free OTDR Trainer Software for PCs After you study this page, you can download a free OTDR Trainer to run on your PC. The Optical Time Domain Reflectometer (OTDR) is useful for testing the integrity of fiber optic cables. Whether you're a network engineer or. OTDR testing analyzes fiber optic cable performance from end to end by testing components along the cable, including connection points, bends, and splices. The OTDR works like a radar, sending light pulses and analyzing reflections to show where issues exist. It can verify splice loss, measure length and find faults.