An SOA (Semiconductor Optical Amplifier) is a semiconductor element that amplifies light. Antireflective processing is applied on both facets of a semiconductor laser to eliminate the resonator structure. When light enters from outside the semiconductor, the light is amplified by stimulated emission.SOA is used for amplifying an optical signal. SOAs are included in the optical transceiver modules used for communication between data centers to amplify the optical signal in the 1.3 um band used for Ethernet communication in order to compensate for transmission loss