What is the difference between WDM and SONET?

To begin with, let us learn about Wavelength Division Multiplexing (WDM).


WDM represents Wavelength Division Multiplexing. WDM is completed only in fibre optic channels. In WDM, there are several light waves from multiple sources are linked utilizing a prism to form a composite light signal sent across the channel.

The application of WDM is the SONET network in which several optical fibre lines are multiplexed and demultiplexed. There is a new technique referred to as DWDM (dense WDDM). It can create multiple huge computers of the medium by composing mediums closer to one another. It achieves even higher efficiency.

Types of WDM

There are two types of WDM, which are as follows −

  • Dense Wavelength Division Multiplexing

    It is a technology in which several optical signals (laser light) of multiple wavelengths or colors are combined into one signal and are transmitted over the connecting channel to an extended area.

    When the optical signal transmission distance shifts into hundreds of kilometers, there are few signal losses. It can satisfy this signal loss, optical fibre amplifiers are used in the DWDM transmission system.

    The DWDM technology required this gain bandwidth to transmit several optical signals together effectively. DWDM can send up to 80 channels (80 optical signals) with 100 GHz (0.8 nm) spacing.

  • Coarse Wavelength Division Multiplexing

    CWDM is a technology in which multiple optical signals (laser light) of multiple wavelengths or colors are combined into one signal and are transmitted over the transmission channel for a short interval.

    DWDM technology is generally useful for long-distance transmission higher than 100 km. But, if the transmission distance is less than 100 kilometers, we are not required to facilitate optical amplifiers.

    The CWDM system has a channel spacing of 20 nm among the optical signals. This allows the assistance of cheap elements, such as uncooled lasers, MUX, and DEMUX.


SONET stands for Synchronous optical networking. It is a standardized digital connection protocol that can share a high volume of data over relatively long areas using a fibre optic channel. In SONET, there are various digital data streams are shared at the same time over optical fibre using LEDs and laser beams.

SONET supports multiple data streams simultaneously. It was created to support efficient services in telecommunication systems and thus became widely adopted. SONET uses standardized costs so that all types of organizations can be interconnected.

In packet-oriented networks, a single packet normally includes two parts such as the data header and the payload. During transmission, the data header is shared first and then the payload is sent. With SONET, however, a slight change is created. The header is defined as overhead and is not sent before the payload.

Updated on: 18-Nov-2021


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