A station-side device performs transmission and reception of an optical signal to and from a subscriber-side device, and includes a communication control unit configured to perform optical signal communication using a plurality of wavelengths by wavelength division multiplexing and time division multiplexing; and a registration unit configured to set an acceptance period in at least one wavelength among the plurality of wavelengths, to perform a new registration of a subscriber-side device in response to a registration request of the subscriber-side device received within the acceptance period, and not to set the acceptance period in at least one other wavelength among the plurality of wavelengths.