April 23, 2024
Synchronous Optical Network

Understanding SONET Technology Architecture, Standards, Protocols, and Applications

Synchronous Optical Network (SONET) is a standardized telecommunication protocol that allows transparent transport of multiple digital hierarchical services over optical fiber. The concept of SONET was introduced in the late 1980s to standardize synchronous digital hierarchy (SDH) technologies supporting telecommunication services. This article provides an overview of the SONET technology including its architecture, standards, protocols and applications.

SONET Architecture

A fundamental building block of SONET is the synchronous transport signal (STS). The basic STS frame operates at 51.84 Mbps and is identified as STS-1. Higher-rate signals are simply integer multiples of the basic STS-1 building block. For example, STS-3 operates at 155.52 Mbps (3 x STS-1), STS-12 operates at 622.08 Mbps (12 x STS-1), and so on.
The asynchronous transfer mode (ATM) is used to map lower-speed services like T1/E1, DS3, and Ethernet into the synchronous payload envelope of these higher-rate STS signals. Multiple lower-speed services can be statistically multiplexed over the same fiber using this approach.

SONET Protocol Standards

The key SONET standards defined by the Exchange Carriers Standards Association (ECSA) and the American National Standards Institute (ANSI) include:

Synchronous Optical Network (SONET): Defined the basic building blocks and interfaces.

– Synchronous Digital Hierarchy (SDH): An international version of SONET developed by the International Telecommunication Union (ITU).

– T1/E1 Mapping: Specifies how to map lower-speed services such as T1 and E1 into higher-speed SONET payloads.

– Operations Administration Maintenance (OAM): Defines operations, administration, maintenance and provisioning (OAM&P) functions.

– Automatic Protection Switching (APS): Specifies how to dynamically reroute traffic in case of fiber cuts or equipment failures.

These standards allow interoperability between networking equipment from different vendors. They help network operators uniformly manage performance, provisioning and fault isolation across multi-vendor network elements.

SONET Applications

Some of the key applications of SONET/SDH include:

– WDM Networks: Dense Wavelength Division Multiplexing (DWDM) and Coarse WDM (CWDM) leverage SONET/SDH to provide multi-gigabit transmission capacity over single strands of fiber.

– Metropolitan Area Networks: SONET/SDH is widely used to build high-speed MAN rings supporting services like Ethernet, IP, and storage area networks (SAN).

– Wireless Backhaul: SONET/SDH transmission systems provide connectivity between cellular base stations and core mobile networks.

– Carrier Networks: Long-haul and regional networks of telecom carriers use SONET/SDH for transparent transmission of voice, data and video traffic.

– Enterprise Networks: Many enterprises with branch offices rely on SONET/SDH leased lines or switches for WAN connectivity and remote LAN access.

– Cloud and Data Centers: Storage traffic within and between data centers increasingly use 10GbE, 40GbE or 100GbE interfaces over SONET/SDH networks.

– Legacy networks: SONET/SDH helps integrate legacy networks built on TDM, FDDI, ESCON, Fiber Channel into new IP/MPLS-based networks.

1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it