Abstract: An optical amplification system connected via a connector to an optical transmission path through which Raman excitation lights are sent out prevents the Raman excitation lights from entering and keeps the Laser Safety function caused by the detection of reflection light when the optical connector is disconnected. The optical amplification system includes an optical amplifier to amplify optical main signals; an optical receiver element to detect reflection lights from an end face of the connector, when the connector is disconnected; a circuit to reduction control the output power of the optical amplifier, based on the detection of the reflection light by the optical receiver element; and a blocking filter inserted between the optical amplifier and the connector, for blocking the Raman excitation lights.