Fiber loss, also called fiber optic attenuation or attenuation loss, refers to the loss of signal between input and output. Losses can be introduced by various means such as intrinsic material absorption, scattering, bending, connector loss and more. Corning recommends that all fiber optic systems be tested to a minimum set. 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. Optical fiber loss refers to the decrease in optical power due to absorption and scattering after optical signals are transmitted through optical fibers.