Insertion loss is a power loss that results from inserting a component into a previously continuous path or creating a splice in it. It is measured by the amount of power received before and after the insertion.
In copper cable, insertion loss measures electrical power lost from the beginning of the run to the end.
In fibre cable, insertion loss (also called optical loss) measures the amount of light lost from beginning to end. Many things can cause light to be lost: absorption, diffusion, scattering and dispersion.
It can also be from poor connections and splices in which the fibres don’t align properly.
Light loss is measured in decibels (dBs), which indicate relative power. A loss of 10 dB means a tenfold reduction in power.
Light strength can be measured with optical power meters, optical loss test sets and other test sets that send a known light source through the fibre and measure its strength on the other end.
Fiber light sources