A SEMICLASSICAL MODEL FOR NOISE-PROPAGATION IN DEPLETED-PUMP OPTICAL AMPLIFIERS

Erbium-doped and parametric fiber-optic amplifiers can be modeled as a cascade of ''amplifying'' beamsplitters, each representing a short fi ber section in which the pump is approximately constant. Each beamspli tter obeys simple noise combination relations and its gain is calculat ed from the standard rate equations, The proposed model allows for the management of pump depletion in a very simple way by numerical analys is, avoiding direct quantum mechanical calculations, Sample noise prop agation diagrams are reported for technically significant values of th e parameters. For the four-wave-mixing amplifier, it has been found th at the 3-dB noise limit can be reached even for a strong gain compress ion.