An OTDR system utilizes a laser source that is turned “on” and kept powered until its light reaches the end of the fiber span being measured (i.e., until the fiber span is fully illuminated). At any point in time after the fiber is fully illuminated, the laser source can be turned “off”. The return (reflected and backscattered) signal is directed into a photodetector of the OTDR, and is measured from the point in time when the fiber span starts to be illuminated. The measurements are made by sampling the return signal at predetermined time intervals—defined as the sampling rate. The created power samples are then subjected to post-processing in the form of a differentiation operation to create a conventional OTDR trace from the collected data.