Generally, the optical attenuation loss of an optical module between 0. 3 and 3 dB is considered normal. This is not an arbitrary adjustment but a necessary measure, carefully implemented based on signal transmission principles, device specifications, and practical. 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. The link attenuation of the. Attenuation is the gradual loss of optical signal power as light travels through a fiber, measured in decibels (dB), and typically expressed as a rate: decibels per kilometer (dB/km).