Repetition-rate dependence of gain compression in InGaAsP optical amplifiers using picosecond optical pulses

A two-level model of a semiconductor optical amplifier is used to calculate gain compression due to picosecond optical pulse injection. Gain compression (measured in decibels) is shown to depend linearly on output pulse energy, with a slope that is characterized by a saturation energy. The authors present measurements of gain compression in the three regimes of repetition rates. A very low repetition rate (200 kHz) is the single-pulse injection regime, 500 MHz to 2 GHz is the regime where the pulse period is comparable to the gain recovery time in the amplifier under test, and 3-6 GHz is the regime where the pulse period is smaller than the gain recovery time. In all cases, the measurements confirm the gain compression characteristics predicted by the model. They show that a short gain recovery time results in an increased output power for a given acceptable level of gain compression, as well as an increased gain level for a given output power