Mixed 10/40/100-Gb/s transmission through bandwidth-managed ROADMs

We survey reconfigurable optical add/drop multiplexer (ROADM) architectures that enable efficient and flexible bandwidth utilization in dense wavelength division multiplexed (DWDM) systems. Recent system demonstrations showing the potential of in-service capacity upgrade by using mixed 10-Gb/s, 40-Gb/s, and 100-Gb/s channels in a same network are reviewed.