The OMD-1800, as a CWDM optical mux and demux, is a bidirectional passive optical multiplexer and de-multiplexer, allowing multiple optical signals at different wavelengths to pass through a single optical fiber link. It combines up to 18 different wavelengths from different optical fibers into a single optical fiber. Also, it separates up to 18 different wavelength signals from a single optical fiber into 18 separate optical fibers.