This paper describes the current research status of the λ-tunable Wavelength-Division Multiplexing/Time-Division-Multiplexing-Passive Optical Network(WDM/TDM-PON). This optical access system realizes new cost-effective operations from the network operator′s point of view. The main feature of the proposed system is that it aggressively exploits wavelength tunability. We classify the system configurations and applications. Then, we describe key technologies, namely newly developed λ-tuning burst-mode transceivers and a widely applicable Dynamic Wavelength and Bandwith Allocation(DWBA) algorithm. Finally, we summarize our research and discuss several issues related to the λ-tunable Wavelength-Division Multiplexing/Time-Division-Multiplexing-Passive Optical Network(WDM/TDM-PON).