Compared with time division multiplexing based passive optical network (TDM-PON), wavelength division
multiplexing based passive optical network (WDM-PON) is a better technology for the wider bandwidth and one to
one connection provided. An efficient evolution from TDM-PON to
WDM-PON without changing the current PON
is needed. We propose a novel evolution from TDM-PON to WDM-PON based on DPSK/NRZ orthogonal
modulation. No change for ONU of the existing TDM-PON is required. The good performance and feasibility of the
method after a 20-km transmission is experimentally demonstrated.