Attenuation makes signals weaker in fiber optic cables. Check your optical transceiver's specs often. Clean connectors. Optical Signal Attenuation is the single greatest factor limiting the distance and performance of your network. This guide will demystify signal loss, explore its causes, and show you how. Attenuation in fiber optics is the gradual loss of light signal strength as it travels through a fiber cable. It's measured in decibels per kilometer (dB/km), and it determines how far a signal can travel before it becomes too weak to read.