Abstract

Long-distance, high-data-rate laser communication systems in the past invariably incorporated bulky transmit and receive telescopes to compensate for limited available radiance from laser sources. Development of more-sensitive optical receivers as an alternative to increased transmitter power has previously centered on optical heterodyne and predetection amplification. Both approaches have demonstrated limited improvements in system performance. We present preliminary experimental results and communication system analysis of a new approach for an optical receiver employed in free-space optical communications. The high sensitivity receiver is based on the optical field retaining its temporal form (and its coherence properties) despite attenuation on long-distance propagation. A field whose power corresponds to infrequent photon arrivals, if resonant with a high-finesse etalon, sees the full 100% transmittance, consistent with coherent field addition, although a photon detector would find the incident power to be very granular. If photon counting is deferred until the optical field is coherently amplified, the form of the field is kept intact.

© 1993 Optical Society of America