Wavelength router for energy efficient photonic aggregation with large-scale λ-tunable WDM/TDM-PON

This paper proposes a wavelength router configuration with large aggregation ratio for lambda (λ)-tunable wavelength-division-multiplexing / time-division-multiplexing passive optical network (WDM/TDM-PON). With this router, the aggregation functions of layer-2 switches (L2SWs) in the conventional access networks are moved into the PON; photonic aggregation. Therefore, L2SWs are no longer required, which lowers power consumptions in the central office. Our wavelength router comprises cyclic arrayed-waveguide gratings (AWGs), two-stage power splitters that work for wavelength-routing and aggregating the traffics from different PON branches, respectively. Optical amplifiers are placed in parallel between each stage of power splitters to compensate for the insertion losses of this router itself, and the number of optical amplifiers is proportional to that of splitting ratios of power splitters on the optical subscriber unit (OSU) side. When the total aggregation ratio of the router is fixed, the allowable combination of the splitting ratios of each stage is decided to fulfill the loss budget requirements. Based on theoretical analysis clarifying the allowable combinations, we decide the router configuration with the lowest power consumption and estimate the impact of the photonic aggregation on the power consumption in the central office.