FlexLoop: A Distributed Scheduling Strategy for AWGR-Based Optical Networks

Optical networks based on arrayed waveguide grating routers (AWGRs) offer significant advantages, including low latency, high bandwidth, and low power consumption. However, addressing the contention issues associated with AWGRs has become a primary concern in practical deployment. Previous research has focused on centralized control methods to address this challenge, but their scalability is often limited. Additionally, distributed time-slot strategies have been implemented, but fixed time-slot configurations can result in performance loss. To effectively overcome these challenges, we propose a distributed scheduling strategy called FlexLoop. Authorizations are issued by receiving nodes and passed between sending nodes via the software-defined networking (SDN) switches. The authorization holder is permitted to transmit a batch of data to the designated node. Each receiving node has the autonomy to define the authorization passing rules through SDN switch configurations. Similarly, each sending node retains the flexibility to either use the authorization to transmit data or forward it to other nodes. Therefore, FlexLoop operates in a fully distributed manner and shows adaptability to various traffic patterns. Experimental results demonstrate that FlexLoop reduces packet latency by up to 92.01% and improves throughput by up to 77.09% compared to NegotiaToR. Additionally, a prototype system was developed, which validates the practical feasibility of implementing FlexLoop.