Abstract: A system for assessing organ function couples light emitters into an optical fiber delivery assembly of which the tip extends to or into an internal organ and illuminates tissue; the device senses temperature at the tip, and a collection fiber collects light scattered, reflected or emitted by the surrounding tissue. Control and processing modules drive the laser diodes and process return spectral signals, e.g., to assess metabolic activity and detect onset of shock. A prototype uses four laser diodes with peaks at 735, 760, 805 and 890 nm, with a front end splitter providing a reference beam to a photo detector for normalizing detection output and correcting the signal samples. The device may include a plurality of laser diodes and may select subsets of the sources to tailor spectral illumination to different target enzymes, metabolites or other compounds.