An OLT that receives a signal in which transmission signals having a plurality of transmission rates are time-division multiplexed, as a received signal, and performs data reproduction by selecting reproduction data to be reproduced, among oversampled signals obtained by oversampling the received signal. The OLT includes a data-signal-information acquisition unit that acquires a transmission rate of a received signal targeted for a process of the data reproduction, a sampling frequency control unit that determines a sampling frequency to be used for the oversampling based on the transmission rate, and a sampling-clock generation unit that generates a clock signal having the sampling frequency determined by the sampling-frequency control unit, and performs the oversampling based on the clock signal.