Studies are being carried out in Italy concerning the strategy for the introduction in the 1990's of optical fiber systems in the distribution network, in order to supply customers with broad-band services (in particular with video services). This paper deals with some of the main choices that are being done, in particular in view of a field trial which is planned in Rome in 1988.

This paper is a review of European field trial experience with fiber optic trunking systems from 1975 to the present. Details of the systems installed and of the experiences in each of the participating European countries are given.

"COS 2" is the second Italian field trial with an optical cable. In this experiment about 5 km of optical cable were installed in normal telephone ducts of the Turin local network between two telephone exchanges. The cable has a capacity of 8 fibers, but, for cost reasons, in 4 of the 5 km of cable only 3 fibers were inserted. An installation procedure was developed, allowing the independent laying of several cables in one duct; it was possible to pull up to 1 km of optical cable in order to minimize the number of splices. A special splice (Springroove®splice) and splicing technique, not requiring the use of a microscope or other intricate tools, were employed. Field measurements of transmission characteristics (attenuation and bandwidth) were performed by means of specially designed measurement equipment. An experimental 140 Mbit/s system was tested on a link about 9 km long (without intermediate repeaters) obtained using this cable.

This paper deals with an experimental 139.264 Mbits/s digital transmission system on 1.2/4.4-mm coaxial cable at present under field trial. The system utilizes the hybrid transmission technique in which many analog repeaters axe placed between two regenerators. A detailed equipment description is reported and the results of the field trial on an experimental link are given.