A system and method for conditioning a beam of light comprised of several wavelengths by means of selecting from among the plurality of available wavelengths, a desired set of wavelengths simultaneously. A small number of multi-wavelength lasers or continuous spectra light sources, or both, may be the source for the plurality of light wavelengths, and a configuration of beam splitters/combiners, mirrors and wavelength selectable pass- and stop-filters provide a combined beam of light wavelengths selected from among the available wavelengths.