The OTDR sends light pulses down the cable, then analyzes backscatter to locate faults. You use the backscatter coefficient to identify attenuation changes and pinpoint breaks. For short cable segments, a visual fault locator (VFL) helps you confirm the exact fault location. OTDR testing analyzes fiber optic cable performance from end to end by testing components along the cable, including connection points, bends, and splices. What Is an OTDR? What Is an OTDR? An OTDR is a powerful tool that helps technicians and engineers assess the health of fiber optic cables. Getting it right the first time when installing or troubleshooting optical cables means reliable testing equipment and procedures. It can verify splice loss, measure length and find faults.