Three-dimensional grid architecture supporting discretionary direct communication among optical network units in metro-access networks

In this paper, a three-dimensional grid architecture supporting discretionary direct communication among optical network units (ONUs) is proposed. By setting up one $N \times N\hspace{3pt}$N×N arrayed waveguide grating (AWG) and two coarse wavelength division multiplexers in the remote node (RN), the optimal path selection of discretionary direct communication among ONUs can be carried out. At the same time, the construction of the RN is simple. By combining with a three-band wavelength allocation, downstream and upstream signals as well as direct-communication signals can be simultaneously transmitted. By utilizing a four-level protection mechanism, three kinds of optical fiber fault protection (i.e., feeder fiber fault protection, distribution fiber fault protection, and interconnecting fiber fault protection) can be achieved. Besides, both the scalability and the reliability of the network can be greatly improved. Finally, the feasibility of the proposed architecture is demonstrated by the simulation experiment.