Abstract: In an optical multiplexer-demultiplexer system, an optical multiplexer system includes a first set of bandpass filters and an optical multiplexer for combining different wavelengths of input optical or laser signals T into a single output optical or laser signal O1 after bandpass filtering of the input optical or laser signals T by the first set of bandpass filters. An optical demultiplexer system includes a second set of bandpass filters and an optical demultiplexer for outputting the output optical or laser signal Ol via a COM port after passage through one of the second set of bandpass filters. The optical demultiplexer is also operative or configured to receive via the COM port an input optical signal comprising a number of different wavelength optical or laser signals R. Via the optical demultiplexer and the second set of bandpass filters, the different wavelength optical or laser signals R can be separated and output separately by the optical demultiplexer system.