Two years of experience with broadband ISDN field trial

In 1988 the BERKOM field trial became operational, demonstrating the first broadband exchange and transmission system that is fully based on ISDN. The product version of an ISDN exchange (System 12) has been enhanced by broadband circuit switches for 2 Mbit/s and 140 Mbit/s. Signalling for both narrowband and broadband channels is performed via an extended D-channel protocol with service indicators for identification of the various channels and channel types. 150 Mbit/s transmission equipment has been installed for 30 subscribers covering lengths of up to 30 km. The system makes use of the wavelength division multiplexing tech- niques for the realization of bidirectional transmission via a single monomode fiber per subscriber. A system enhancement has been realized by supporting distribution services: TV and stereo sound The transmission equipment with a speed of 600 Mbit/s provides for the subscriber up to 4 different TV channels simultaneously, which can be selected out of 48