Provided is an optical network system and optical network unit (ONU) structure enabling a passive optical access network having a meshed structure with at least two central nodes and plurality of ONUs. One embodiment employs a partially or fully meshed structure of optical fibers between customer locations and multiple optical line terminal (OLT) locations creating a passive optical access network. The ONUs can communicate with a neighboring OLT or ONU using a symmetrical or asymmetrical TDM scheme, and convert between the different TDM schemes. For this purpose, the ONU structure includes two transceiver units, one connected to the western network port and the other to the eastern. The ONU can establish communication between either network port and a further ONU or an OLT, with the ONU controller adapted for passing through data, and converting TDM schemes.