In relation to the fiber-optic element shown in Pig. 9.1, one must take into account the frequency dependence of the amplitude, phase, and group delay in the fiber. Thus, the fiber should have a flat amplitude and group-delay response within the passband required to send the signal tree of linear distortion. In addition, since modal-distortion-limited bandwidth is difficult to equalize, it is best to choose a single-mode fiber. The fiber attenuation is also important, since the carrier-to-noise performance of the system will change as a function of the received optical power