Patent ID: 8098678

Claim:
A passive optical network (PON) system, comprising: an optical line terminal (OLT); a plurality of optical network units (ONUs) connected to the OLT through a passive optical network respectively; a gateway connected to the OLT through a communication line; wherein the OLT includes: correspondence information between an output port number of the GW and an identifier (ID) of an optical network unit (ONU) that uses a GW output port identified with the output port number; an OLT control part that allocates a bandwidth distributed to each of the plurality of ONUs dynamically as the next upstream frame transmission bandwidth; and a downstream frame generation part that generates a downstream frame including bandwidth control information indicating an upstream frame transmission bandwidth for each ONU according to a frame transmission bandwidth allocated by the OLT control part, wherein the OLT control part, when receiving a congestion occurrence notice indicating a number of the output port in which congestion occurred from the GW, identifies the ONU corresponding to the congestion output port number in the correspondence information and allocates the upstream frame transmission bandwidth to the identified ONU which is less than the bandwidth allocated to the identified ONU before the congestion of the output port occurred.