Scalability of ROADMs for multiple parallel fibers

Growing traffic loads in communication networks demand for cost-efficient multi-degree switching architectures. Implementing reconfigurable optical add/drop multiplexers (ROADMs) offers cost-efficient and highly flexible solutions in terms of wavelength and direction reconfigurability. First, we give an overview of existing ROADM architectures by introducing a classification matrix. In the second part of the paper, we propose and analyze a concept, which can overcome scalability limitations and decrease the cost of ROADMs connected by parallel fiber pairs. This concept is based on the elimination of switching components, while preserving the most important flexibility advantages of a ROADM.