This is the most mainstream ROADM structure on the market at present. As shown in Figure 2, its UNI side is composed of 1×N port WSS, and the UNI side is composed of a multicast optical switch MCS. An M×N port MCS switch has M input ports and N output ports, and is composed of M 1×N port optical splitters (PS) and N M×1 port optical switches (OSW). The optical signal is input from one of the input ports, and is first divided into N parts by the optical splitter, and broadcast to all N optical switches; then the optical switch corresponding to the target output port selects the received optical signal, and other optical switches ignore it. signal.
According to the functions of the 1×N port WSS and MCS, this ROADM structure can realize the CDC function. However, the optical splitter in the MCS generates too much loss when splitting and broadcasting, so an optical amplifier array is required to supplement the optical power. It is expensive to configure the optical amplifier array.