An apparatus to measure optical characteristics of a fiber optic transmission line or other optical medium may include a source to generate a bipolar pulse signal waveform. The apparatus may also include a mixer to mix the bipolar pulse signal waveform and an optical pulse and reflected signal waveform from the fiber optic transmission line or other optical medium to form a mixed product waveform, wherein the reflected signal is responsive to the optical pulse being transmitted into the fiber optic transmission line or optical medium.