| 摘要 |
<p>The present invention discloses a method and system for accurate time transfer in PON, used to solve the technical problems of the processing procedure being complicated, the protocol workload being huge and excessive network bandwidth being occupied when using the Precision Time Protocol in network to transfer time in PON. In the present invention, an Optical Line Terminal (OLT) ranges Optical Network Units (ONUs) and obtains ranging information, then, triggered by the periodic Pulse per n Second (PPnS), generates a PPnS timestamp based on the local reference counter and the Time of Day (TOD) above second; OLT transmits the ranging information, the periodic PPnS timestamp and TOD to ONUs; ONUs predicts the time of the next second according to said periodic PPnS timestamp, TOD and ranging information, and outputs the corresponding PPnS. The invention is characterized by the combination of the features of PON point to multi-point and PON ranging into its time transfer method, the high accuracy of time transfer, and the low hardware costs for OLT and ONU, as well as the extremely small bandwidth occupancy due to the usage of a single copy of PON itself to broadcast the time information.</p> |
