Evolution from TDM-PON to WDM-overlaid PON employing a wavelength-conversion node

A cost-effective and smooth evolution scheme from a time-division multiplexing–passive optical network (TDM-PON) to a WDM-overlaid PON that can provide high-speed fiber-to-the-home service to a wide area with a high population density is proposed. Existing optical transmitters of TDM-PON optical network units (ONUs) are reusable by employing a wavelength-conversion node at the ONU site, which transforms the wavelength of each ONU to a predefined WDM wavelength. A specially designed optical router is needed at a remote node site; it should broadcast downstream signals to each ONU, routing upstream ONU signals to a wavelength-conversion node and passing the wavelength-converted signal to an optical line terminal. A simple but efficient remote node structure is proposed. A wavelength conversion node should be designed carefully since it repeats burst-mode signals from multiple ONUs. A 2R repeater-based wavelength conversion node is suggested. Performance of various schemes is analyzed and their measurement results are provided.