PROGRESS TOWARDS THE FIELD DEPLOYMENT OF COHERENT OPTICAL FIBER SYSTEMS

In this paper, we describe the first demonstration of a coherent optical transmission system deployed in an operational network. The miniaturized external cavity laser and the automated endless polarization control scheme which enabled us to mount this demonstration are described in detail, together with specific system results. We then discuss the possible field deployment of other coherent system options, based on FSK modulation of DFB and DBR lasers, and polarization diversity reception. Finally, we highlight the considerable potential afforded by coherent techniques for meeting future network requirements. The demonstrated advantages of greater power budget and wavelength selectivity, combined with the use of optical amplifier muitiwavelength repeaters, make coherent techniques particularly relevant to the growing demand for greater transmission capacity, transparency, and network flexibility. An increasingly urgent need for robust coherent optical technology can thus be anticipated, for wideband transmission and passive routing, for both telecommunications and computer networks of the near future. © 1990 IEEE