Direct ONU interconnection schemes towards latency-aware passive optical networks

This paper reviews the various existing direct optical network unit (ONU) interconnection schemes which provide direct communication among peers resided locally. Direct inter-ONU communication provides the opportunity to reduce substantial latency among two communicating ONUs. In reviewed schemes, ONU data is transmitted directly to the destined ONUs by avoiding transmission to the OLT, thus OLT complex re-routing, rescheduling and re-modulation is avoided. Direct ONU intercommunication does not impose any extra burden on upstream and downstream bandwidth therefore efficient bandwidth utilization is also increased. Reviewed schemes also utilize the OLT and ONU transceivers (TRxs) efficiently and reduces the energy consumption and OPEX.