Introduction

In the preceding chapters we investigated in detail the gain spectra of fiber OPAs with CW pumps. This is an important case for several reasons. From a practical standpoint, CW pumps are a requirement in applications such as amplifiers for optical communication. Also, experiments with CW pumps are simple to set up and are thus widely used. From a theoretical standpoint, the assumption of a CW pump leads to the relatively simple sets of equations and analytic solutions that we have studied in previous chapters.

It is also often desirable, however, to use pumps that do not have constant intensities, for a variety of reasons. One reason is that pumps that are pulsed with a low duty cycle can generate high peak powers while having a modest average power; this is a common way of generating peak powers of several watts or tens of watts using relatively inexpensive EDFAs with sub-watt average output power. Another reason is to generate OPA gain only during specified periods of time, to select particular parts of a signal waveform in order to implement some signal processing function. Examples of this are optical sampling for displaying optical pulse shapes, optical sampling for generating multiple replicas of optical signals, and optical switching for demultiplexing optical pulse trains.

Here we present alternative techniques for calculating the output fields of pulsed-pump OPAs.