Introducing Flexible and Synthetic Optical Networking: Planning and Operation Based on Network Function Programmable ROADMs

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Elastic optical networks are envisaged as promising solutions to fulfill the diverse bandwidth requirements for the emerging heterogeneous network applications. To support flexible allocation of spectrum resources the optical network nodes need to be agile. Among the different proposed solutions for elastic nodes, the one based on architecture of demand (AoD) exhibits considerable flexibility against the other alternatives. The node modules in the case of AoD are not hard-wired, but can be connected/disconnected to any input/output port according to the requirements. Thus, each AoD node and the network (fabricated with AoD nodes) as a whole acts like an optical field-programmable gate array. This flexibility inherent in AoD can be exploited for different purposes, such as for cost-efficient and energy-efficient design of the networks. This study looks into the cost-efficient network planning issue for synthetic networks implemented through AoD nodes. The problem is formalized as an integer linear programming formulation for presenting the optimal solution. Furthermore, a scalable and effective heuristic algorithm is proposed for cost-efficient design, and its performance is compared with the optimal solution. The designed networks with AoD nodes are further investigated for a dynamic scenario, and their blocking probability due to limited switching resources in the nodes is examined. To alleviate the blocking performance for the dynamic case, an efficient synthesis strategy along with a scheme for optimal placement of switching resources within the network nodes is presented. Extensive results show that 1) even at high loads, the network with AoD nodes achieves saving of switching modules up to 40% compared to the one with static reconfigurable optical add–drop multiplexers (ROADMs) through a proper network design, 2) by diminishing the spectrum selective switches the overall power consumption of the network decreases by more than 25% for high loads, and 3) for the dynamic scenario the blocking owing to the node modules constraint is alleviated significantly by slightly augmenting the switching devices and optimally deploying them within the network nodes.