To obtain a slave station device capable of reducing power consumption.
An ONU includes a power saving mode in which a sleep period to make an optical transmitter 141 into a power saving state and an active period to tentatively activate the optical transmitter 141 are repeated periodically. The ONU includes: receiver units 161-1, 161-2 for receiving data to be transmitted to an OLT 1; and based on the data, a power saving control unit 111 for calculating the sleep period which is the length of the sleep period capable of data transmission. On receipt of data in receiver units 161-1, 161-2, the sleep period length is set to be a sleep time calculated by the power saving control unit 111, so that data is transmitted to the OLT 1 in the active period.
HIRANO YUKIO
YAMASHITA AKIHIRO
