Let s look at what it is and when it is important and when it is not. We ll take a look at the effects in cable systems, both in the RF and optical domains. Return loss is a measure of how closely the impedance of a source matches that of a load. The source might be a signal processor and the load a headend combining network. Or the source might be a receiving antenna and the load the coaxial cable feeding signal to the headend.
Return loss is one of several methods of measuring the degree of match between the two.
Return loss and VSWR are simply two ways to look at the same thing. To get an idea of what return loss is about, think of ripples of water in a bucket. If you drop a stone in the middle of a bucket of water, you know that waves will ripple out from the stone, and when they hit the side, they will bounce back again. This characteristic impedance is the impedance that must be connected to each end to eliminate any reflections. If the source and terminating impedances are not equal to the characteristic impedance, then some power will be reflected.