A uni-directional test will be conducted on all pigtail splices with no greater than a. 8 dB after 5 repeated attempts results in the replacement and re-splicing of that pigtail. Guidelines On What Loss To Expect When Testing Fiber Optic Cables To be able to judge whether a fiber optic cable plant is good, one does a insertion loss test with a light source and power meter and compares that to an estimate of what is a reasonable loss for that cable plant. Fiber optic testing of a newly installed system not only verifies that the system meets its design requirements, but also creates a performance baseline for all future testing and troubleshooting of t at system. Corning recommends that all fiber optic systems be tested to a minimum set. Fiber optic systems include both passive components and active electronics. Key tests include: Effective fiber testing utilizes advanced tools such as Optical.