Method, system and optical network device for synchronizing time of a passive optical network

An optical network device, comprising a processor configured to:

• receive a first PON protocol transmission frame carrying a first clock packet;
• acquire a first time at a first packet time stamp generating point located at a PON Media Access Control (MAC) layer of the first PON protocol transmission frame, the acquired first time being regarded as the time when the first clock packet is received;
• receive a second PON protocol transmission frame carrying a second clock packet, wherein the a second clock packet carries the time when the first clock packet is sent;
• and
• adjust local time according to a difference between the time when the first clock packet is sent and the time when the first clock packet is received.

A point-to-multipoint optical communications system, comprising an Optical Line Termination (OLT) and an Optical Network Unit (ONU), wherein:

• the OLT comprises:
• means for forming a downstream Passive Optical Network (PON) protocol transmission frame from the OLT to the ONU and processing an upstream PON protocol transmission frame from the ONU to the OLT;
• a master clock synchronization processing module, configured to send a first clock packet carried in a first downstream PON protocol transmission frame and a second clock packet carried in a second downstream PON protocol transmission frame to the ONU, wherein the second clock packet carries the time when the first clock packet is sent;
• and
• a master clock packet time stamp generating module, configured to acquire time according to frame data of the first clock packet at a PON Media Access Control (MAC) layer and regard the acquired time as the time when the first clock packet is sent;
• the ONU comprises:
• means for forming a upstream PON protocol transmission frame upstream PON protocol transmission frame from the ONU to the OLT and processing a downstream PON protocol transmission frame from the OLT to the ONU;
• a slave clock packet time stamp generating module, configured to acquire time according to frame data of the first clock packet at the PON MAC layer and regard the acquired time as the time when the first clock packet is received;
• and
• a slave clock synchronization processing module, configured to receive the first downstream PON protocol transmission frame and the second downstream PON protocol transmission frame and adjust local time of the ONU according to a difference between the time when the first clock packet is sent and the time when the first clock packet is received.