Abstract: This work clarifies the analysis of the theoretical study of noise and transmission gain characteristics of semiconductor optical amplifiers (SOAs), which are relevant in the novel local area optical communication systems. We investigated the effects of noise on AlGaAs/GaAs SOA transmission performance through the measurement of output power, optical gain, the optical signal-to-noise ratio, and noise figure. It was observed that noise has a dramatic effect on SOAs’ operation transmission efficiency, and the performance of the amplifier structure may be limited. If the drive current and injection power at the SOA can be changed and its active region length modified, then the variation of gain, optical signal-to-noise ratio, and noise figure at the output of the structure can be obtained.