European telecommunications companies, anticipating the demand for delivery of interactive multimedia services to business and residential customers, are busy planning for tomorrow. On the drawing boards are broadband networks designed for increasing the traffic-carrying capability of core transport networks.Today’s modern networks are based on electronic synchronous digital hierarchy (SDH), the electronic successor to Europe’s plesiochronous digital hierarchy (PDH). SDH’s improved signal synchronicity between local modes compared with PDH, its cross-connects and high-capacity single carrier opto-electronic transmission line systems support various switched platforms, including asynchronous transfer mode, switched multimegabit data service, frame relay, etc. Tomorrow, it will be feasible and cost-effective to build the transport infrastructure using layers of electronic and all-optical nodes, interconnected with very-high-capacity wavelength division multiplexed carrier transmission systems.