Synchronous Digital Hierarchy (SDH) is a standardized digital communication protocol used to transmit large amounts of data over optical fiber networks. It organizes data into a structured format, allowing for efficient and reliable transmission. SDH supports various data rates and can carry multiple types of services, such as voice, video, and data, making it versatile for telecommunications. One of the key features of SDH is its ability to synchronize different data streams, ensuring that they remain in time with each other. This synchronization is crucial for maintaining the quality of service in networks. SDH is often compared to Asynchronous Transfer Mode (ATM) and is widely used in telecommunications infrastructure globally.