ONU 2A for P-P includes a signal-type discriminating unit 22A that discriminates whether a type of a downstream signal transmitted from OLT is for the P-P or not, and outputs an enable/disable control signal that controls an optical transmitter to an enable state or a disable state, and a control unit 21 that controls the optical transmitter to the enable state or the disable state according to the enable/disable control signal, wherein the signal-type discriminating unit 22A outputs to the control unit 21 a disable control signal that controls the optical transmitter to the disable state under an initial state before the type of the downstream signal is discriminated, and outputs to the control unit 21 an enable control signal that controls the optical transmitter to the enable state after the downstream signal is discriminated to be for the P-P.