SUBSCRIBER-SIDE OPTICAL COMMUNICATION DEVICE, COMMUNICATION SYSTEM, CONTROL DEVICE AND POWER-SAVING CONTROL METHOD

An ONU 2 causes a receiver 221 and a transmitter 222 of an optical transmission-and-reception module 202 to enter into a power-saving state separately and includes a CDR 203 that clocks based on a signal from an OLT 1, an oscillator 207 that generates an internal clock, a time stamp counter 209 that manages a time of the ONU 2 based on the clock in a period in which the CDR 203 regenerates the clock and manages the time of the ONU 2 based on the internal clock in a period in which the CDR 203 does not regenerate the clock, an MPCP control unit 208 that decides, when a Cyclic Sleep mode is set, a receiver-time synchronization time that is a period in which the receiver 221 is normally operated within a sleep time, based on a difference between a time stamp value included in the signal transmitted from the OLT 1 and a time stamp managed by the time stamp counter 209, and a power-saving control unit 212 that controls the receiver 221 to be normally operated in the receiver-time synchronization time.