Return Loss

We can measure the return loss on fiber optic and copper cables
A collection of network cables

What Is Return Loss?

When light or electricity passes over a link or cable, some of the power is lost. This is true for data as well as electricity. One way of measuring this is called Return Loss.

The source device will inject a certain amount of power into a link. This is true for fibre optic and copper links.

Some of that power will be lost as the signal travels across the link. This is called Insertion Loss or Attenuation.

We can reflect that signal back to the original source device, and measure the power level. The difference between the power injected at the source and the power that is reflected back is the Return Loss.

Like insertion loss, this is measured in decibels (dB). The higher this number, the better.

Also, see the Insertion Loss article by Fluke Networks.