Dual-fiber CWDM MUX/DEMUX is typically used in CWDM network to achieve dual way transmission, which transmits and receives signals with the same wavelength. A duplex fiber links two dual-fiber CWDM MUX/DEMUXs, supporting the same wavelengths installed on each end of the optical network. Two fibers with the same wavelength enable duplex transmission on different directions. But in some specific condition, only one fiber is available for network capacity expansion, where a single-fiber CWDM MUX/DEMUX is needed. which is very much different from the dual-fiber one.
The single-fiber CWDM MUX/DEMUX has a simplex line por, that is how it differs from dual-fiber CWDM MUX/DEMUX. There are also single-fiber CWDM MUX/DEMUX which is made with a duplex port, but with only one of this duplex port is in use, the other is usually marked with N/A.
