On the Efficiency of Survivable Flex-Grid SDM Networks

In this paper, we focus on the performance of a survivable flex-grid network with space division multiplexing (SDM). To provide network survivability, we use dedicated path protection and shared backup path protection. For both schemes, we also consider squeezed protection that allocates backup resources only for a part of the primary flow. The squeezed protection is considered for the protection level changing from 0% (no flows are protected) up to 100% (full network protection) with a step of 10%. Moreover, we consider two SDM switching policies—independent (SDM-indsw) and joint (SDM-jsw). In this paper, we define all considered problem versions using integer linear programming technique as well as propose a dedicated heuristic algorithm. Then, we perform extensive simulations focused on the performance of a survivable SDM network in terms of the spectrum usage. The results show that the path protection in an SDM network brings additional spectrum consumption; however, the amount of additional resources depends on various factors such as required protection level, applied protection method, switching policy, and traffic pattern. Moreover, the results also reveal that SDM-indsw is much more spectrum-efficient than SDM-jsw considering all protection methods and levels. It uses, on average, half of the spectrum required for SDM-jsw. Additionally, the investigation shows that SDM-jsw is especially spectrum-inefficient when realizing variable-size demands (sets including both small and large demands).