Synchronous Optical Network (SONET), developed in the US by the ANSI and Synchronous Digital Hierarchy (SDH), developed in the Europe by the ITU-T are two almost identical standards for transmitting various data payloads over optical fibers at high speeds.
Here, the entire network is time-synchronized tightly, which is a significant difference from the previous Plesiochronous Digital Hierarchy (PDH) standard. This synchronization significantly reduces buffering in the transmission and thus improves the data rate. The data rates for SONET/ SDH vary from 155 Mbps for OC-3/ STM-1 to 40 Gbps for OC-768/ STM-256. SONET/ SDH has well-defined frame structure and uses TDM as the underlying mechanism for multiplexing services. SONET/ SDH is still widely used across the world. Even where the core network is getting transformed into a packet core, there are a significant number of client interfaces continuing to use SONET/ SDH. Changing client services is an expensive and time-consuming affair. Circuit Emulation of SONET/ SDH is an effective strategy for network backbone modernization without impacting the client service.
For long, Tejas has been a leading provider of SONET/ SDH solutions. Tejas Circuit Emulation Service (CES) cards have one of the most advanced implementations of the circuit emulation function in the industry today. As a result, with Tejas multi-purpose platforms, service providers can support SONET/ SDH in addition to multiple technologies such as PTN, OTN, DWDM on the same platforms.