British Telecom 565 Mbit/s lightline system

British Telecom is currently developing a 565 Mbit/s trunk optical fibre system which incorporates both multiplexing and line transmission. The system will operate at 1.3 µm over single-mode fibre with a 30 km repeater spacing. Extensive use is being made of ECL uncommitted logic arrays (ULAs) manufactured at British Telecom Research Laboratories (BTRL) and derived from the reliable ECL 40 process as used in submarine cable system integrated circuits. Details of the system design are presented together with the initial results of a laboratory system built out of commercially available components to establish confidence in the design.