Increasing TDM Rates for Access Systems Beyond NG-PON2

Despite the first ever standardization of a passive optical network (PON) that exclusively uses an expansion in the wavelength domain rather than the time domain to enhance network throughput, continued progress in increasing time-division multiplexed (TDM) PON capacity is essential in providing per-wavelength capacity upgrades to time- and wavelength-division multiplexed PONs or as an alternative TDM-only solution. We discuss candidate technologies for increasing the per-wavelength data rate in PONs and speculate more generally regarding the near-term and long-term evolution of PON systems.