Increasing the upstream capacity of passive optical networks by Pulse Amplitude Multiplexing

Pulse Amplitude Multiplexing (PAMx) is proposed to increase the upstream throughput of Passive Optical Networks (PONs). PAMx requires the change of the electronics at the Optical Network Units (ONUs) and Optical Line Terminal (OLT), but not of the optical or distribution network components. This scheme allows the simultaneous transmission of data from multiple ONUs whose power levels have been arranged by the OLT. Once the upstream bits are synchronized, the time slots that were previously exclusively occupied by a single ONU can now be shared by multiple ONUs. An algorithm in the protocol layer to support PAMx and further increase network efficiency is also proposed. Experimental results show the feasibility of doubling or even tripling the upstream throughput of PONs using PAMx.