In this paper, we study the applicability of the quasi-passive reconfigurable (QPAR) device, a special type of quasi-passive wavelength-selective switch with flexible power allocation properties and no power consumption in the steady state, to implement the concept of reconfigurable backhaul for 5G wireless networks. We first discuss the functionality of the QPAR node and its discrete component implementation, scalability, and performance. We present a novel multi-input QPAR structure and the pseudo-passive reconfigurable (PPAR) node, a device with the functionality of QPAR but that is pseudo-passive during steady-state operations. We then propose mesh and hierarchical back-haul network architectures for 5G based on the QPAR and PPAR nodes and discuss potential use cases. We compare the performance of a QPAR-based single-node architecture with state-of-the-art devices. We find that a QPAR node in a hierarchical network can reduce the average latency while extending the reach and quality of service of the network. However, due to the high insertion losses of the current QPAR design, some of these benefits are lost in practice. On the other hand, the PPAR node can realize the benefits practically and is the more energy-efficient solution for high reconfiguration frequencies, but the remote optical node will no longer be passive. In this paper, we discuss the potential benefits and issues with utilizing a QPAR in the optical infrastructure for 5G networks.This work has been funded by the Spanish project TIGRE5 CM (grant number S2013/ICE 2919), the EU H2020 5G Crosshaul project (grant number 671598), and the Australian Research Council’s Discovery Early Career Researcher Award (DECRA) funding scheme (project number DE150100924). The authors would also like to acknowledge the support of the Center for Integrated Systems, Stanford University, and Corning Incorporated.
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