The insertion loss (or attenuation) is usually specified in decibels, calculated as 10 times the logarithm of base 10 of the ratio of input and output powers. High-quality fusion splices may reach values like. 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. Insertion loss, also known as attenuation, is the loss of optical power that occurs when light passes through a fiber optic connector. It is caused by factors such as misalignment, air gaps, and imperfections in the connector components. Excessive insertion loss can lead to weak signals, increased bit errors, and.