The axial coherence length of laser radiation is both specific and unique to lasers. An angle-scanned interferometer is described as a coherent energy modulator in a coherence-discriminating laser receiver. A symmetrical solid-spaced Fabry-Perot interferometer etalon is used. Etalon pairs are used in a logic arrangement that passes coherent laser signals and rejects incoherent background signals. Two pairs of stepped etalons are used to detect a single laser pulse. The fundamental limits of performance of this type of laser receiver are listed.