The concept of deep-space optical communications was formulated shortly after the invention of lasers. The promise of laser communications, high data rate delivery with significantly reduced aperture size for the flight terminal, led to the pursuit of several successful experiments from Earth orbit and provided the incentive for further demonstrations to extend the range to deep space. This paper is aimed at presenting an overview of the current status of optical communications with an emphasis on deep space. Future perspectives and applications of optical communications related to near-Earth and interplanetary communications are also addressed.

NASA's Mars laser communications demonstration (MLCD) project (since discontinued) was designed to achieve data rates greater than 1 Mb/s from the farthest Mars range and greater than 30 Mb/s from the nearest Mars range. We present here pathways whereby ongoing optical technology advances should allow 30 dB of increased data rates relative to MLCD by 2020. In other words, technical advances should soon allow the return of deep-space data at rates of 1 Gb/s from the maximum Mars range, 100 Mb/s from Jupiter distances, and 10 Mb/s from Uranus, all many orders of magnitude greater than present radio-frequency capabilities. The potential for realizing the stated capability with less than a three times increase in dc power required from the spacecraft and no increase in payload mass is discussed.