This is a CWDM slim 4-channel mux cartridge that operates over wavelengths 1551nm, 1571nm, 1591nm, and 1611nm. It also includes a 1310 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.