35 dB / Km at 1310 nm, which with a typical link loss of 20 dB, gives a maximum link length of 57 Km. The lowest loss wavelngth region is around 1550 nm. Best performance is achieved with for example Corning SMF-28® ULL with <0. 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. The estimate, called a "loss budget" is calculated using typical component losses for. ity check. This type of testing is the most accurate testing available and is the most accurate characterization of the fiber optic system's apability. It includes a collection of references to the main measurement methods and. This test will measure the loss of a fiber optic cable, singlemode or multimode, including connectors on each end individually.