Some optical communications experiments

Experiments performed to evaluate the possibilities and limitations of beams of coherent light as carriers of wideband information are described. These include transmission of television pictures, multiplexed voice-frequency channels, and other signals over enclosed paths by both phase and amplitude modulation of optical carriers. It is shown that long-distance transmission can be achieved without serious distortion of the beam wavefront. This is verified from determinations of heterodyne detection efficiency and by direct measurements of the optical phase distribution over wavefronts which have been transmitted for distances as great as 20 miles through beam waveguides.