Special issue paper. Subsystems for optical-fibre-communication field demonstrations

Recent progress in the various lines of research contributing to the realisation of an optical-fibre communication system has been extremely rapid. At present, long-lived, room temperature, continuous-working semiconductor lasers are being tested, and confidence is growing that today´s results are the harbingers of future progress. Several technologies have been shown to be capable of producing multimode or monomode fibre waveguides on a routine basis with attenuation well below 10 dB/km. Fast, reliable silicon avalanche photodiodes are available commercially, commercially. Connectors for single-fibre waveguides have been produced with 1¿2 dB/km loss and splices with much lower attenuation. Complete analogue and digital laboratory systems have been shown at manyconferences and exhibitions. From a position of such strength in the realm of research, it would seem that a wide range of targets would be set for a field trial. However, the introduction of an optical-fibre communication system into an existing network is possibly a more far-reaching step than any that has been taken since the inception of these networks. Because of this, a great deal of engineering confidence has still to be established. A large-scale field demonstration could achieve this, but many subsystems must be engineered before this can be held. With careful design, such a demonstration will assist in determining the targets to be set for a field trial.