Synchronous Optical Networking (SONET) is a standardized protocol for transmitting digital information over optical fiber. Developed in the United States and later standardized by the American National Standards Institute (ANSI), SONET is the U.S. counterpart to the international standard known as Synchronous Digital Hierarchy (SDH), which is used predominantly outside of North America.
SONET was designed to address the challenges of integrating different digital transmission standards onto a single network.
The key features and aspects of SONET include:
- Standardized Rates: SONET defines a hierarchy of signaling rates, starting with OC-1 at 51.84 Mbps and scaling up through OC-3, OC-12, OC-48, OC-192, and beyond.
- Multiplexing: One of the main advantages of SONET is its ability to multiplex multiple digital signals of different rates onto a single higher-rate signal. This makes efficient use of the available bandwidth.
- Ring Topology: SONET often uses a ring topology for redundancy. The bidirectional line-switched ring (BLSR) and unidirectional path-switched ring (UPSR) configurations provide protection against failures, enabling rapid recovery from fiber cuts or equipment malfunctions.
- Overhead and Management: SONET frames have overhead bytes that facilitate network management, error correction, and other essential functions.
- Interoperability: SONET was designed to carry payloads of varying digital transmission standards, making it a versatile choice for consolidating multiple data streams onto a single optical network.
- Scalability: The SONET framework is inherently scalable, allowing for the easy addition of new nodes and higher data rate capabilities as network needs grow.
- Transparent Payload Envelopes (TPE): SONET can encapsulate various payloads in its Transparent Payload Envelope (TPE), enabling it to carry data from different sources and standards.
SONET’s development was driven by the need to accommodate the rapid growth of telecommunication networks during the late 20th century. It offered service providers a robust and flexible standard for high-speed digital transmission over optical fiber, simplifying network design, operation, and maintenance. While newer technologies and protocols have emerged with the evolution of optical networking, SONET remains an integral part of many legacy telecommunication infrastructures.