SDH add/drop multiplexer rings in Northern Ireland

BT Northern Ireland has introduced a network of optical fibre rings into the province as part of an EEC-assisted project known as STAR (Special Telecommunications Action for Regional Development). This network consists of three fibre rings, each equipped with STM-1 add/drop multiplexers and it represents one of the first applications of SDH rings anywhere in the world. The authors describe the SDH equipment used in the Northern Ireland STAR (NISTAR) project and discuss the protection and synchronisation strategies employed in the network. This is followed by an outline of the new testing and commissioning techniques that are required to characterise this equipment and to establish an operational ring network. Finally results of initial network performance tests are presented