SDH, or Synchronous Digital Hierarchy, is a standardized multiplexing protocol used to transmit large amounts of data over optical fiber networks. It organizes data into a series of time slots, allowing multiple data streams to be combined and sent simultaneously. This technology is essential for telecommunications, enabling efficient and reliable communication. The SDH framework supports various data rates and is compatible with other digital transmission systems. It provides features like error correction and network management, ensuring high-quality data transmission. SDH is widely used by service providers to deliver services such as internet, voice, and video to customers.