Sigma is a compact STM-1/STM-4  add/drop multiplexer, specially suitable for the utilization in extending networks to the edge by providing cost-effective multi-service access and delivering more revenue-generating services to subscribers. It transports TDM (Time Division Multiplexing), Ethernet and IP (Internet Protocol) over existing SDH (Synchronous Digital Hierarchy) network, and can be customized for the traffic demand, in the access network, which is typical for residential and business applications.