Optical Transmission Research

Abstract

The availability of coherent sources producing usable amounts of power in the optical frequency range has stimulated considerable research in optical communications. Devices such as oscillators, modulators, detectors, and ancillary apparatus having desirable characteristics exist and are being used to design and build prototype terminals. Two possible media are being studied and means are being sought to improve their performance. They are 1) through-the atmosphere propagation and 2) enclosed media with appropriate focusing and directing elements. Experimental optical transmission systems can readily be assembled with information capacities in a single RF channel comparable to those of microwave radio or millimeter waveguide. Such optical systems are not yet competitive for high reliability common carrier service because 1) long-distance transmission techniques of adequate reliability have not yet been advanced, and 2) optical repeater components are not yet competitive with their lower frequency counterparts. Some features characteristic of optical transmission systems are reviewed in this paper, along with a brief indication of the state-of-the-art for major components.

Design of a 94 GHz Millimeter-Wave Four-Way Power Combiner Based on Circular Waveguide Structure

“…High-frequency millimeter-wave has the advantage of narrow beams, strong penetrability, high resolution, and better anti-interference, displaying well-applied prospects in communications [6][7][8][9], imaging [10,11], and radar [12,13]. Simultaneously, high-frequency millimeter-waves have a shorter wavelength, which could effectively reduce the size of components and provide more benefits in terms of system miniaturization.…”

The optical fibre as a transmission medium

“…The concept of light amplification by stimulated emission of radiation (laser) set forth in the classic paper by Schawlow and Townes (1958) created new enthusiasm for Alexander Graham Bell's early ideas of telephony over light beams (Kompfner 1965). Line-of-sight transmission through the atmosphere turned out to be severely limited by adverse weather conditions (Miller and Tillotson 1966). Guided transmission employing periodic focusing elements in underground conduits appeared economical only for extremely high information capacity (Miller 1970).…”