Synchronous Digital Hierarchy (SDH) is an international standard for high-speed telecommunications network transmission. SDH is designed to provide a scalable and synchronous transport platform for voice, data, and video traffic over optical fiber networks. It is the international counterpart to the North American SONET (Synchronous Optical Networking) standard.
Key features of SDH include:
- Synchronization: SDH ensures synchronization across various network elements, allowing for the seamless multiplexing and transmission of different types of traffic.
- Hierarchical Structure: SDH uses a hierarchical structure of containers and frames to organize and transmit data. Containers can carry different types of data, and frames provide the structure for transmitting data across the network.
- Standardized Bit Rates: SDH defines a series of standardized bit rates for data transmission, known as STM (Synchronous Transport Module) levels. The most common STM levels are STM-1, STM-4, STM-16, and STM-64, each offering higher data rates than the previous level.
- Multiplexing: SDH allows for the aggregation of multiple lower-speed signals into higher-speed containers and frames. This enables efficient use of network resources and optimization of bandwidth.
- Protection and Restoration: SDH incorporates protection mechanisms to ensure network reliability in the face of failures. This includes path and line protection, enabling rapid restoration of services in case of network disruptions.
- Cross-Connectivity: SDH networks support cross-connections, allowing for flexible routing of traffic and efficient allocation of resources.
- Network Management: SDH includes provisions for network management and maintenance, allowing operators to monitor and control network elements and optimize network performance.
- International Standard: SDH is recognized and used internationally, providing compatibility and interoperability between different telecommunications networks around the world.
- Advancements: While SDH has been widely used for traditional telecommunications networks, newer technologies like Ethernet and IP/MPLS have gained popularity due to their flexibility, scalability, and support for packet-based data.
Overall, SDH plays a crucial role in enabling high-speed, reliable, and synchronized data transmission in telecommunications networks. While newer technologies have emerged, SDH remains relevant in certain applications where its features and benefits are well-suited to the network’s requirements.