For multimode fiber, the loss is about 3 dB per km for 850 nm sources, 1 dB per km for 1300 nm. 5 dB/km max per EIA/TIA 568) This roughly translates into a loss of 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. Both the TIA and ISO cabling standards list the acceptable loss limits for fibre optic components, and these values are. Fiber optic loss, also known as optical attenuation, refers to the light loss between the transmitter and receiver. Intrinsic loss: Rayleigh scattering, inherent absorption. Losses in the optical fiber can be categorified.