Principles of Synchronous Digital Hierarchy

29Advent of Digital Technology

Figure 2.9a shows the input and output waveforms when the signal oper-

ates within the linear region of the transfer characteristic, of the transmitter

or the channel, causing no distortion to the output; Figure 2.9b shows the

input and output waveform when the range of the input signal goes beyond

the linear region of the transfer characteristic. The resulting output wave-

form in the second case is distorted.

This type of distortion is called harmonic distortion. The nonlinear opera-

tion results in the generation of second, third, fourth, and so on orders of

harmonic wave components. If all these components are added up, they will

give rise to the shape of the distorted waveform obtained at the output as

show