Technique for detecting the status of WDM optical signals

An apparatus for detecting the status of wavelength division multiplexed optical signals, the apparatus comprising:

• a splitter for splitting an original, multiplexed, polychromatic optical beam into at least two representative, multiplexed, polychromatic optical beams;
• a demultiplexer comprising:
• a lens system for collimating a first of the at least two representative, multiplexed, polychromatic optical beams, and for focusing each of a plurality of collimated, representative, monochromatic optical beams;
• and
• a diffraction grating for separating the first collimated, representative, multiplexed, polychromatic optical beam according to wavelength into the plurality of collimated, representative, monochromatic optical beams, each of the plurality of collimated, representative, monochromatic optical beams for communicating a respective, representative optical signal;
• and
• a detector for detecting the presence or absence of a respective, representative optical signal on each of the plurality of focused, representative, monochromatic optical beams.