An Optical Time Domain Reflectometer (OTDR) is a versatile tool for identifying cable issues., splices, stress points, or breaks) along a fiber optic line. Fiber Optic Testing Testing is used to evaluate the performance of fiber optic components, cable plants and systems. Corning recommends that all fiber optic systems be tested to a minimum set. UL Solutions can assess fiber optic products, including but not limited to optical fibers, optical fiber cables, optical connectors, optical splitters/couplers, optical distribution boxes and fiber terminal boxes, for performance and reliability to any published industry standard, such as UL.