A description is given of 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 made it possible to mount this demonstration are described in detail, together with specific system results. A discussion is presented of the possible field deployment of other coherent system options, based on FSK modulation of DFB and DBR lasers, and polarisation diversity reception. The considerable potential afforded by coherent techniques for meeting future network requirements is highlighted. The demonstrated advantages of greater power budget and wavelength selectivity, combined with the use of optical amplifier multiwavelength 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. >

Progress towards the field deployment of coherent optical fiber systems

Compact, fibre-coupled Faraday optical isolators have been assembled. Isolators with both conventional and polarisation maintaining monomode fibre tails have been fully characterised in insertion loss, return loss and isolation ratio over the wavelength range 1480-1560 nm. >

S.A. Al-Chalabi

Papers

Characteristics of fibre-coupled optical isolators at 1.5μm