This application discloses an optical amplifier apparatus including a first amplifier unit and a hybrid filter unit. The first amplifier unit is configured to receive a first beam including signal light and first monitoring light. The first amplifier unit is further configured to amplify the first beam to obtain a second beam. The hybrid filter unit is configured to: receive the second beam output by the first amplifier unit, and separate the first monitoring light and the signal light from the second beam. The hybrid filter unit is further configured to: transmit the first monitoring light in the second beam to a monitoring light detection apparatus of a first station through a first output port. The hybrid filter unit is further configured to: perform gain flattening filtering processing on the signal light in the second beam to obtain filtered signal light, and output the filtered signal light.