Experimental studies of the noise characteristics in nonlinear semiconductor optical amplifiers

This paper describes an experimental study of noise characteristics in saturated semiconductor optical amplifiers used for all optical signal processing applications. We demonstrate two effects that have been recently predicted theoretically. The first is a significant reduction in the narrow-band intensity noise power relative to the level predicted in linear amplifiers with the same gain. This effect results from the nonlinear coupling between the injected signal and the spontaneous emission. The second effect is an increase in the amplified spontaneous emission power of a saturated amplifier, which is due to the longitudinal dependence of the carrier density in nonlinear amplification