Synchronous multiplexers

Synchronous digital hierarchy (SDH) is a technology of broadband transport networks which provide an infrastructure for subscription of users to a wide range of services. SDH networks are capable of transferring data at bit rates of up to 10 Gbit/s, provide a wide range of assess rates including those which are compatible with plesiochronous digital hierarchy being transparent for traffic of any nature (voice, data, video). Service information imbedded in a SDH signal ensures centralized control over network devices and network as a whole for its flexible and well-timed management as well as for providing the users with necessary data streams protected against any network failures. Today there are a great number of SDH networks operating with STM-1, STM-4 and STM-16 systems. In recent years there appeared a cheaper alternative for STM-64 system that is Dense Wavelength Division Multiplexing (DWDM). SDH networks are circuit-switched networks with Time Division Multiplexing (TDM) where data from specific users are addressed according to timeslots within a frame unlike packet-switched networks which move data according to the destination address in each package.