INFRARED INFORMATION-TRANSMISSION

Information transmission systems using an infrared optical carrier can be categorized in two major areas: 1) the guided transmission systems, involving silica-based optical fibers for the near-infrared region (0.8 to 1.6 μm) or fluoride glass fibers for the mid-infrared region (2 to 4 μm), 2) the unguided free-space communication systems, on one hand atmospheric transmissions, and on the other hand intersatellite links. The general principles of these systems and the present state of the associated component technology is described. A state-of-the-art of optical fiber link experiments is surveyed, including coherent detection experiments and the first laboratory transmission trials using fluoride glass fibers. Finally, information is given on atmospheric free-space transmission and on future plans for intersatellite links.