Amplified spontaneous emission and gain-saturation nonlinearity in high-gain optical amplifiers: The biased amplifier

The systematics of amplified spontaneous emission and gain-saturation nonlinearity in high-gain optical amplifiers are explored. It is shown that of all the variations of the several dimensionless parameters that occur, only a reduction of the small-signal gain-length product can simultaneously minimize these two problems. Furthermore, of the various possible changes of the dimensional quantities that make up the gain-length product, increasing the saturation intensity achieves the highest overall gain for a given measure of distortion, and the least distortion for a given value of overall gain. This leads to the concept of the biased amplifier, one version of which is then treated in detail numerically.