Synchronous Optical Network (SONET)

What is a Synchronous Optical Network (SONET)?

Synchronous Optical Network (SONET), developed by Bellcore, is a standardized digital communication protocol used to transmit a large amount of data over relatively large distances using optical fiber. Developed in the mid-1980s, SONET was designed to provide a high-speed, low-error transmission method that could unify the diverse telecommunications infrastructure, which previously relied on multiple standards and transmission rates. It's predominantly used in North America, while the Synchronous Digital Hierarchy (SDH) standard is used in Europe and most of the world, although the two standards are broadly compatible.

With SONET, multiple digital data streams are transferred simultaneously over the optical fiber. Key Points:

• Developed by Bellcore
• Used in North America
• Standardized by American National Standards Institute (ANSI)
• Similar to Synchronous Digital Hierarchy (SDH) which is used in Europe and Japan.

Key Features of SONET

• High Data Rates: SONET supports high bandwidth, starting from 51.84 Mbps (OC-1 level) and scaling up to 10 Gbps and beyond (OC-192, OC-768).
• Synchronous Transmission: Data is transmitted in a synchronous format, meaning that the sender and receiver clocks are synchronized, allowing for efficient and predictable data transmission.
• Multiplexing: SONET allows for the multiplexing of lower-rate signals into a higher-rate signal, making it highly efficient in combining different types of traffic such as voice, data, and video into a single optical fiber.
• Standardization: Provides a standardized interface for connecting fiber-optic transmission systems, ensuring compatibility and interoperability between equipment from different manufacturers.
• Network Management: Includes extensive Operations, Administration, Maintenance, and Provisioning (OAM&P) capabilities, enabling network operators to monitor, manage, and maintain network performance effectively.
• Fault Tolerance: Features like automatic protection switching (APS) provide high levels of fault tolerance and reliability by rerouting traffic in case of a link failure.

SONET Architecture

SONET architecture is based on a hierarchy of signal levels called Optical Carrier (OC) levels. The basic unit of SONET is the Synchronous Transport Signal level 1 (STS-1), which operates at 51.84 Mbps. Higher levels of OC-n signals are direct multiples of this basic rate, providing a scalable framework to support increasing bandwidth demands.

Advantages of SONET

• Scalability: Can easily scale to meet growing bandwidth requirements by upgrading to higher OC levels without changing the underlying infrastructure.
• Flexibility: Supports the integration of various types of communication services, including traditional telephony, cellular networks, and Internet data traffic.
• Reliability and Robustness: Offers built-in protection mechanisms and redundancy to ensure high levels of network availability and reliability.
• Simplified Network Management: Provides comprehensive tools for managing and diagnosing network issues, reducing operational costs.

Applications of SONET

• Telecommunications Networks: Used by telecommunications providers to aggregate and transport voice and data traffic over long distances.
• Internet Backbones: Forms the backbone of the Internet, providing high-speed data transmission between data centers and network access points.
• Corporate Networks: Used in large enterprises to interconnect data centers and office locations with high-speed optical links.
• Mobile Backhaul: Supports the backhaul of mobile network traffic from cell sites to the core network.

Challenges and Future of SONET

Despite its advantages, the use of SONET has been gradually declining in favor of more flexible and efficient technologies such as Ethernet, Multiprotocol Label Switching (MPLS), and Dense Wavelength Division Multiplexing (DWDM) that offer higher bandwidth and lower cost per bit. However, SONET/SDH infrastructure still underpins much of the global telecommunications network, providing critical high-speed transport for many applications. The transition to newer technologies is ongoing and is expected to continue as the demand for bandwidth grows and network requirements evolve.

See Also

Synchronous Optical Network (SONET) is a standardized digital communication protocol used to transfer multiple digital bit streams over optical fiber using lasers or light-emitting diodes (LEDs). Developed in the mid-1980s, SONET is a set of transmission protocols that allows for the integration of synchronous signals into a low-jitter, high-bandwidth signal stream. It was designed to provide a robust and flexible transport infrastructure for both voice and data traffic, with a strong emphasis on reliability, scalability, and network management.

• SDH (Synchronous Digital Hierarchy): The international equivalent of SONET, widely used outside North America.
• Optical Fiber Communication: Covering the transmission of light as an optical signal over a fiber optic cable for telecommunications.
• DWDM (Dense Wavelength Division Multiplexing): A technology that increases bandwidth by sending multiple signals simultaneously on the same optical fiber.
• Ethernet: Discussing the most widely installed local area network (LAN) technology.
• Multiplexing: Explaining the process of combining multiple signals into one signal over a shared medium.
• Telecommunications Infrastructure: Covering the physical hardware, transmission media, and software systems used to deliver telecommunications services.