This Recommendation deals with the classification and the characteristics of multi-degree reconfigurable optical add/drop multiplexers (MD-ROADMs), including two-degree ROADMs. Some examples of MD-ROADM configurations and applications are given in the appendices.

Photonic cross connects (PXC), which are a special category of MD-ROADM characterized by a unique switching matrix (see Figures 7-4, 7-5, 7-6, 7-7, 9-2, I.4 of [ITU-T G.680]) are outside the scope of this Recommendation.