A single detector based spectroscopy system using FAST (fiber array spectral translator) fibers and two excitation sources in conjunction with a holographic spectrum analyzer (HSA) to obtain simultaneous and selective display of spectroscopic regions of interest. A sample can be illuminated with different laser excitation wavelengths and resulting multiple spectra can be comparatively observed on a single display screen for more fruitful analysis of sample spectral responses (and, hence, sample chemical or physical properties) under different excitations. The HSA may be configured to focus on user-selected spectral regions of interest from different such spectra and a single CCD detector may be configured to collect spectral data from all selected spectral regions of interest in corresponding portions of the CCD pixel array, thereby allowing subsequent simultaneous display of such selected spectral regions of interest. The HSA may also allow simultaneous collection and display of portions of a single spectrum from a single excitation wavelength. A user can perform better comparative analysis when spectral regions of interest are juxtaposed with each other on a single electronic display.