2.4 Gbit/s and beyond [optical communications]

Telecommunications transmission has increased in capacity by exploitation of digital techniques allied to developments in optical fibre transmission. The present position is that bit-rates within the digital hierarchy up to and including 565 Mbit/s are carrying traffic in the network over optical fibre. All of these systems are asynchronous and most of those currently being installed operate over an established network of single-mode fibre exhibiting a dispersion zero near 1300 nm. Looking beyond 2.4 Gbit/s transmission, these views require reassessment. The speed increments required by 5 and 10 Gbit/s time division multiplexed systems can be achieved by techniques which can be identified in 1988. However the timescales for such developments may not relate well to the needs of network growth. A range of optical techniques is also available which could provide an alternative approach to network expansion as well as providing facilities not presently available. Some of these are considered