Abstract: The present disclosure relates to systems and methods for calibrating LIDAR systems using internal light. In one implementation, at least one processor of a LIDAR system may control at least one light source; receive from a group of detectors a first plurality of input signals associated with light projected by the at least one light source and reflected from an object external to the LIDAR system; determine based on the first plurality of input signals a distance to the object; receive from the group of detectors a second plurality of input signals associated with light projected internal to the LIDAR system by the at least one light source; determine based on the second plurality of input signals that there is performance degradation in at least one detector of the group of detectors; and initiate a remedial action in response to the determined performance degradation.