SDH Technology

Because with the PDH technology (Plesiochrone Digital Hierarchy) crucial international standards were absent and, in addition, higher transmission rates were demanded to affordable prices, the Synchronous Digital Hierarchy (SDH) asserted itself in the end of the 80s more and more as a technology of the future.

With transmission rates up to 10 Gbit/s (STM-64) and the possibility to be able to steer and to supervise the standardized network elements from central place, this technology is extremely adapted for the development of transport or backbone networks. By simplified Add & Drop functions, channels with smaller bit-rates are set aside and are inserted from high-bit-rate SDH currents, without complex demulitplexing or multiplexing of the whole signal.

SDH transport network is implemented according to customer's demand as a ring structure or mesh structure and contains different network elements to fulfill the desired functions. Corresponding to the high demand for bandwidths, the SDH technology becomes more and more displaced in direction of Access. Two areas appear from it: the SDH transport level and under it the SDH-Access.