Synchronous Optical Network, or SONET. A communication protocol called SONET was created by Bellcore and is used to send a lot of data over relatively long distances using optical fibre. Multiple digital data streams are transmitted simultaneously over the optical fibre with SONET.

Key Ideas

• Bellcore developed
• North American usage
• established by ANSI (American National Standards Institute).
• SDH (Synchronous Digital Hierarchy), which is utilised in Europe and Japan, is comparable.

Why is SONET referred to as a synchronised network?

Across the entire network, the timing of signal and equipment transmission is controlled by a single clock (the Primary Reference Clock, or PRC).

SONET Network Constituents

Multiplexer STS:

• performs signal multiplexing.
• optical signal from electrical signal is converted.

Demultiplexer STS:

• performs signal demultiplexing.
• optical signal to electrical signal conversion.

Regenerator:

• It is a repeater that regenerates (increases the strength of) optical signals.

Drop/Add Multiplexer:

• It enables the addition of signals from various sources to a particular path or the removal of a signal.

Why is SONET employed?

An electrical signal is changed into an optical signal by SONET so that it can travel farther.

Connections to SONET

• Section: The portion of the network that connects two nearby devices.
• Line: A section of the network that links two nearby multiplexers.
• Path: The network's end-to-end section.

Layers of SONET:

There are four functional layers in SONET:

1. Step Layer:

• It is in charge of transferring signals from their optical source to their optical destination.
• Providing path layer functions is STS Mux/Demux.

2. The Line Layer

• It is in charge of signal transmission across a real line.
• Add/Drop Mux and STS Mux/Demux both offer Line layer functions.

3. Stacking Section:

• It is in charge of signal transmission across a physical region.
• Each network device performs section layer functions.

4. Optical Layer:

• It corresponds to the OSI model's physical layer.
• It includes the optical fibre channel's physical specifications (light is present when 1 and not present when 0).

Benefits of SONET

• transmits information over long distances
• very little electromagnetic interference
• greater data rates
• Broad Bandwidth

SONET's drawbacks include:

• No standard that is compatible.
• SONET mux services are necessary for tributary services.
• Low cost and efficient for few channels.
• The SONET/SDH network management system is inadequate for managing and using the DWDM technique.
• At higher capacities, bandwidth efficiency is a problem.
• There must be more overhead.