The Collector Filter module (CFM) transfers optical signals between the DWDM side of the ONS 15201 Single-Channel Unit (SCU) and the Client Layer Interface Port (CLIP) module. It also transfers the part of the signal not intended for the SCU to the opposite port on the other side. Only one CFM is used in each collector node.The CFM adds the output signal from the CLIP DWDM laser to the optical line. The CFM also drops the incoming signal from the same ITU channel. In protected mode, this signal goes to the A and B receivers on the ONS 15201 CLIP module. In unprotected mode, this signal goes to the A receiver only.