This is a 2 channel DWDM mux demux that operates over channels 21-22. It also has a monitor port and an express port. This unit can be used as either a multiplexer or de-multiplexer (mux/demux) and is a plug and play system. All of our mux/demux products are 100% compliant and provide a cost effective solution for your network upgrade needs. With our certification test program we guarantee your product will work correctly the first time.