Opex Considerations for Optical Switch Upgrades: A Multiperiod Point of View

In order to provide the necessary capacity on the optical layer, one possibility is to light more fibers. Thereby the fiber nodal degrees of the optical switches are increased. In this paper we propose traffic affecting and non-affecting upgrading types for optical switch models, focusing on operational expenditures (Opex). Opex costs for node upgrades provide a small cost proportion of the overall costs. However, our results indicate that the correlated penalty costs for traffic interruption due to traffic affecting upgrades have considerable impact on the planning result. Two long-term planning approaches provide an upper and a lower bound of the planning optimality and illustrate the necessity of including forecast knowledge to the optimization.