Synchronous networking of undersea cable systems

TAT-9 (transatlantic optical system) will link USA, Canada, France, UK and Spain with the first synchronous undersea cable network using UBMs (undersea branching multiplexes) operating at 591.2 Mbit/s. The authors discuss the architecture and reasons why the particular method of data formatting was adopted. The advantage offered by undersea multiplexing is that security, fault tolerance and traffic flexibility can all be built into the network. The TAT-9 scheme produced a common optical interconnect data format between the major undersea cable system suppliers before the American SONET and CCITT synchronous digital hierarchy (SDH) standards were finalised. Future submarine networks will have to interface to SDH traffic so they discuss whether the TAT-9 standard should be maintained whilst making the system transparent to SDH data signals