Analyzing ROADM costs in SDM networks

As bandwidth demanding applications are spreading, optical networks will run out of bandwidth soon. Space Division Multiplexing (SDM) seems to be a promising solution as it will provide additional bandwidth by incorporating various spatial channels in Multi-Core Fibers (MCFs) and Multi-Mode Fibers (MMFs). Moreover, SDM needs to cut equipment costs down. SDM uses Jointly-Switching wavelength channels across all spatial channels, with the assistance of an adapted Wavelength Selective Switch (WSS). In this paper we analyze the cost of several SDM network configurations. We focus on the number of spatially dimensions, the R-degree of Colorless Directionless Contentionless Reconfigurable Optical Add-Drop Multiplexers (CDC-ROADMs) and the spatially integrated transceivers. Afterwards we derive the minimum number of WSSs needed for ROADM operation. The analysis indicates cases in which we can use much less SDM components and so significantly reduce costs. Moreover, we design an SDM network for Greece, and identify cases where the equipment costs can be minimized.