The Multicast Switch extends current ROADM technology to enable next-generation "colorless, directionless, and contentionless", or CDC, networks. In a CDC network, the Multicast Switch is coupled with Wavelength Selective Switches (WSS), which together are designed to direct any wavelength to any port (colorless), accept input wavelength channels from multiple directions (directionless), and to be able to drop two identical wavelengths from different directions through the same switch (contentionless).
A CDC ROADM is composed of two parts: 1xK Wavelength-selective-switches (WSSs) at the top layer and NxM multicast switch (MCSs) at the bottom layer. An NxM multicast switch is composed of N 1xM splitters at the first layer and M 1xN switches at the second layer. In the drop direction, the wavelengths from each of the N directions are broadcast to M drop ports via a 1xM splitter, while at each drop port, there is a 1xN switch to select wavelengths from one of the N directions. In the add direction, the reverse operation is done, i.e., each of the M coherent transmitters can send its wavelength to any of the N directions via a 1xN switch first, and then the wavelengths from various add ports are collected by a 1xM optical combiner. NeoPhotonics currently focuses on NxM MCS.
Small port count MCSs, like the 4×4, usually do not require amplification to compensate for the splitting loss.