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 modular 4×16 MCSs are designed to reduce first installation costs of contentionless ROADMs and to provide customers with a "pay-as-you-grow" approach for future degree and add/drop port expansion. For example, for degree expansion, after first installing a 4×16 MCS for 4 directions, a second one can be installed as needed, and without disrupting traffic, to achieve an 8×16 configuration, which accommodates 8 directions and provides 16 add/drop ports. A third module achieves 12×16 and a fourth achieves 16×16. Similarly, for add/drop port expansion, additional MCSs can be added to additional WSS ports to achieve Nx32, Nx48 and so on.