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.