Patent ID: 8630539

Claim:
A communication system that connects a plurality of user-side optical line terminating apparatuses (Optical Network Units, hereinafter referred to as ONUs) to a station-side optical line terminating apparatus (Optical Line Terminal, hereinafter referred to as OLT) using a common optical fiber, wherein the ONUs each includes: an optical transceiver connected to the optical fiber, with the optical transceiver being configured to reduce power consumption by shifting to a power saving mode for temporarily stopping a transmitting function; a control device configured to control transmission by the optical transceiver of first information concerning one or more power saving modes executable by the ONU to the OLT; and a storage device configured to store second information representing permission or non-permission of the power saving modes for the ONU to suppress the execution of the power saving modes based on the second information, and the OLT includes: an OLT optical transceiver connected to the optical fiber; and an OLT control device configured to acquire, via the OLT optical transceiver, the first information concerning the executable power saving modes from the ONU and to control the OLT optical transceiver to transmit a writing command for the second information representing permission or non-permission of the power saving modes to the ONU, to thereby cause the ONU to rewrite the second information.