Coarse Wavelength Division Multiplexing (CWDM) enables carriers to deliver more services over their existing optical fiber infrastructure by combining multiple wavelengths on a single fiber. In a typical CWDM system, a multiplexer (mux) is used at the transmitter to join the several signals together, and a demultiplexer (demux) is used at the receiver to split the signals apart. Multiple CWDM mux/demux modules may be chained through the expansion port on the modules. This increases flexibility and enables growth for evolving networks. This tutorial will tell you how to stack two CWDM mux/demux modules via expansion port.