Optical attenuation is the gradual loss of flux (light intensity) as an optical signal travels through a fiber. Measured in decibels (dB), it's the logarithmic ratio of the output power to the input power. To determine the power budget and power margin needed for fiber-optic connections, you need to understand how signal loss, attenuation, and dispersion affect transmission. The uses various types of network cables, including multimode and single-mode fiber-optic cable. This guide will demystify signal loss, explore its causes, and show you how. Optical fibers typically use decibels to measure signal attenuation (dB). However, LEDs are not coherent sources.