This article provides an overview of current efforts in reducing energy consumption in passive optical access networks. Both ITU-T and IEEE standardized PONs are considered. The current solutions proposed by standardization authorities, industry, and academia are classified based on the layer they address in the standardized architectures: physical layer, data link layer, and hybrid. Then, the article provides answers to major questions, such as where, when, and how to reduce PON energy consumption in TDM PONs by means of a quantitative evaluation. Results show that to reduce energy consumption, ONUs must be provided with physical devices that are not only power-efficient but also provide improved services (e.g., fast synchronization) to upper layers. For this latter purpose, novel physical ONU architectures are proposed to speed up the synchronization process and enable effective data link layer solutions. Finally, the feasibility of switching ONUs to low power mode in idle slots is assessed through a testbed implementation.
An optical multi microring network-on-chip (MMR NoC) is proposed and evaluated through numerical simulations. The network architecture consists of a central resonating microring with local microrings connected to the input/output ports. A mathematical model based on the transfer matrix method is used to assess the MMR NoC performance and to analyze the fabrication tolerances. Results show that the proposed architecture exhibits a limited coherent crosstalk with a bandwidth suitable for 10 Gb/s signals, and it is robust to coupling ratio variations and ring radii fabrication inaccuracies.
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