Next-generation optical access networks should not only increase capacity but also be able to redistribute capacity on the fly in order to manage larger variations in traffic patterns. Wavelength reconfigurability is an instrument that can enable such capability of network-wide bandwidth redistribution since it allows dynamic sharing of both wavelengths and timeslots in WDM-TDM optical access networks. However, reconfigurability typically requires tunable lasers and tunable filters at the user side, resulting in cost-prohibitive optical network units (ONUs). In this paper, we propose a novel concept, named cyclic-linked flexibility, to address the cost-prohibitive problem. By using cyclic-linked flexibility, the ONU needs to switch only within a subset of two preplanned wavelengths, but the cyclic-linked structure of wavelengths allows free bandwidth to be shifted to any wavelength by a rearrangement process. A basic rearrangement algorithm is developed to demonstrate that cyclic-linked flexibility performs close to a fully flexible network in terms of blocking probability, packet delay, and packet loss. Furthermore, we show that the rearrangement process has minimum impact on in-service ONUs. To realize cyclic-linked flexibility, a physical implementation is proposed with a feasible cost and wavelength-agnostic ONU design.
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