To reiterate, a bi-directional test consists of two measurements on the same optical fiber, made by launching light into opposite ends of that fiber, then averaging the attenuation at connectors without disconnecting the launch and tail cord from the cabling under test. The Optical Time Domain Reflectometer (OTDR) is useful for testing the integrity of fiber optic cables. It can verify splice loss, measure length and find faults. Later, comparisons can be made. Recommendation ITU-T G. It includes a collection of references to the main measurement methods and. OTDR testing analyzes fiber optic cable performance from end to end by testing components along the cable, including connection points, bends, and splices. We hope that by sharing our knowledge, we will help.