Patent ID: 7609967

Claim:
A method for automatically maintaining bi-directional communication between an optical network unit (ONU) and a central office (CO) in a passive optical network (PON) when the CO upgrades from a first optical line terminal (OLT) having a first PON mode to a second OLT having a second PON mode, the method comprising: obtaining a PON mode relating to downstream data flow from the OLT to the ONU; and upon detecting a change in said PON mode from the first PON mode to the second PON mode: synchronizing said ONU to operate according to a downstream configuration of the second PON mode by performing: attempting to synchronize the ONU according to a last-known downstream configuration of the PON; when the ONU is unsynchronized, attempting to try to connect again with a downstream configuration used prior to the last-known setting; when the ONU is still unsynchronized, attempting to synchronize the ONU according to the line rates and line-codes that are pre-defined in the ONU; and synchronizing said ONU to operate according to an upstream configuration of the second PON mode.