SDH

In telecommunications, SDH stands for Synchronous Digital Hierarchy. It is a standardized multiplexing protocol used to transfer multiple digital bit streams over optical fiber using lasers or highly coherent light from LEDs. Developed to replace the older Plesiochronous Digital Hierarchy (PDH) system, SDH allows for a more reliable and efficient means of data transmission.

Key Features of SDH:

1. Synchronous Transmission: All data streams are synchronized to a single clock, reducing the complexity of synchronization and allowing for easier multiplexing and demultiplexing.

2. High Data Rates: SDH supports high data rates, making it suitable for transferring large amounts of data, including voice, video, and data services.

3. Flexibility and Scalability: It can easily accommodate different types of traffic and can be scaled to support higher data rates as needed.

4. Management and Maintenance: SDH includes robust network management and maintenance capabilities, allowing for better fault management, performance monitoring, and configuration control.

5. Interoperability: SDH is an international standard (ITU-T G.707, G.783, G.784, and G.803), ensuring compatibility between equipment from different manufacturers.

SDH Frame Structure

The basic unit of SDH is the Synchronous Transport Module level 1 (STM-1), which has a bit rate of 155.52 Mbps. Higher levels are multiples of STM-1, such as STM-4 (622.08 Mbps), STM-16 (2.488 Gbps), and STM-64 (9.953 Gbps).

Applications of SDH

• Backbone Networks: SDH is commonly used in the backbone networks of telecommunications providers due to its high capacity and reliability.
• Metropolitan Area Networks (MANs): SDH is also used in MANs to connect various local area networks (LANs) and provide high-speed data services.
• Carrier's Carrier Networks: It is used by carriers to provide transport services to other carriers.

SDH continues to be a critical technology in the telecommunications infrastructure, especially in regions where existing SDH networks are already established and continue to provide reliable service.