Patent ID: 8565601

Claim:
A communication method for an optical communication system that connects a plurality of user-side optical line terminal apparatuses (hereinafter referred to as ONUs) to a station-side optical line terminal apparatus (hereinafter referred to as OLT) using a common optical fiber, the communication method comprising: a step of the ONU in a deregistered state staying on standby until the ONU is registered in the OLT; a discovery step of the OLT discovering the ONU in the deregistered state connected to the OLT via the optical fiber and registering the ONU as the ONU in a registered state; a communication step of the ONU that receives a synchronization signal monitoring out of synchronization by comparing the synchronization signal and a time of the ONU and, when the out of synchronization is detected, returning to the deregistered state and stopping transmission; and a power saving step of the ONU intermittently executing power saving control for stopping or reducing power supply to a transmitter or a receiver for a predetermined pause duration while maintaining a communication link in the communication step, wherein after the pause duration, the ONU temporarily suppresses a shift to the deregistered state due to detection of the out of synchronization.