Patent ID: 7787771

Claim:
A scheduling method of a PON including an OLT and an ONT, the OLT including a wavelength-tunable optical transmitter and a wavelength-locked optical receiver, the ONT transmitting upstream data to the OLT using the same wavelength as that of an optical signal received from the OLT, the scheduling method comprising multiplexing the optical signal by a TDM scheme based on the occupancy of downstream buffers for data transmission from the OLT to the ONT and the occupancy of upstream buffers for data transmission from the ONT to the OLT such that the OLT is configured to schedule transmission of gate messages to corresponding ONTs to enable the corresponding ONTs to coordinate transmission timing of upstream data to the OLT by interleaving polling by estimating a maximum loop-back transmission time (Ti) needed for signal transmission at a given ith wavelength to correspond to a larger one of either a downstream transmission time (DT(i)) or an upstream transmission time (UT(i)) for signal transmission between the OLT and the ONTs that operate at the ith wavelength, wherein DT(i) is estimated by DT ( i )=( DB ( i )+ GATE * ΣONTs ( i ))/( line Rate ( i ))+max RTT ( i )/2 where DB(i) is the ith downstream buffer, whereΣ ONTs(i) is the number of ONTs that operate at the ith wavelength, where GATE is the gate message transmission timelength, where line Rate(i) is the line Rate at the ith wavelength, and where max RTT(i) is a maximum roundtrip timelength at the ith wavelength, and wherein UT(i) is estimated by Ut ( i ) =(UB( i ) + REPORT* Σ ONTs ( i ))/( line Rate (i))+max RTT ( i ) where UB(i) is the ith downstream buffer, where Σ ONTs(i) is the number of ONTs that operate at the ith wavelength, where REPORT is a report message transmission timelength, where line Rate(i) is the line Rate at the ith wavelength, and where max RTT(i) is the maximum roundtrip timelength at the ith wavelength.