Patent ID: 7616899

Claim:
A synchronizing method in an optical access network comprising, in a tree-shaped structure, a center device, a plurality of remote devices, and at least one optical switching device connected between the center device and the remote devices; the center device transmitting to the optical device a downstream control packet having written therein a transmission time thereof, and an identification number, a transmission start time and a transmission duration time of the remote device to which the downstream control packet is transmitted; the optical switching device transmitting the downstream control packet to the remote device to which the control packet is transmitted; the remote device to which the downstream control packet is transmitted, upon receipt of the downstream control packet, setting its own clock to the transmission time, to transmit to the optical switching device an upstream control packet having written therein the transmission start time at the transmission start time; the optical switching device transmitting to the center device the upstream control packet; and the center device determining the packet transmission start time of the remote device after a receipt of the upstream control packet, said method characterized in that: the center device determines a round trip time respectively between the center device and the remote device to which the packet is transmitted and between the center device and the optical switching device; and the optical switching device sets its own clock to the transmission time to obtain a value of a difference in the round trip time and the information thereof, and determining a delay time from a dispatch of an instruction of a connection start to an upstream optical means of the upstream optical switching device up to the time of transmitting the upstream control packet with a result that a value obtained by subtracting the delay time from a sum of the transmission start time and the difference thereof is set as a connection start time, and the connection start time is set at least to the transmission duration time.