What is DWDM (Dense Wavelength Division Multiplexing)? - Neos

What is DWDM (Dense Wavelength Division Multiplexing)?

DWDM wavelength

Dense Wavelength Division Multiplexing (DWDM) is an optical networking technology that dramatically increases the bandwidth of existing networks. Learn how it works and how DWDM solutions can help supercharge your business’s connectivity.

What is Dense Wavelength Division Multiplexing (DWDM)?

Dense Wavelength Division Multiplexing (DWDM) is a kind of Wavelength Division Multiplexing – a technology used to expand the capacity of fibre optic networks. It allows multiple data streams to be transmitted over different light wavelengths through a single fibre.

It’s called ‘dense’ because the gaps between each channel’s wavelengths are much smaller than in Course Wavelength Division Multiplexing (CWDM). As a result, you can transmit many more channels on a single fibre over longer distances.

Learn more about the difference between CWDM and DWDM

How does DWDM work?

Dense Wavelength Division Multiplexing slices the ultraviolet light section of the electromagnetic spectrum into small segments. It’s this tighter wavelength spacing that allows a large number of channels to be carried over a single pair of optical fibres.

DWDM operates on the C band (1525nm to 1565nm wavelengths) or L band (1570nm to 1610nm). The wavelength spacing varies, but a typical DWDM system uses 0.4nm spacing to create up to 88 channels.

DWDM (typical 88-channel plan)

DWDM - typical 88-channel plan showing 0.4nm wavelength spacing


That means you can use your existing network infrastructure far more efficiently, removing the high cost and disruption of laying more fibre.

What are the main components of DWDM systems?

A DWDM system consists of five main components:

  • Optical transmitters and receivers
  • DWDM mux and demux filters
  • Optical add/drop multiplexers
  • Optical amplifiers
  • Optical transponders

Optical transmitters and receivers

Optical transmitters and receivers are fundamental components of DWDM systems. Multiple transmitters in each system provide source signals before they are multiplexed, with several individual lasers deployed to handle different channels in the signal.

Each optical transmitter is fed with electronic data bits – ones and zeros – which trigger the modulation of precise optical pulses. To represent ‘one’, the transmitter’s laser generates a pulse of light. To represent ‘zero’, the laser remains inactive.

The pulses of light then travel the length of the optical fibre, where they are demultiplexed before terminating at optical receivers. These optical receivers detect the light pulses and convert them back into electronic data bits.

DWDM mux and demux filters

The mux filter receives different signals from the optical transmitters via multiple fibres. It then combines and transmits them as a composite signal over a single optical fibre.

At the demux filter on the receiving terminal, all the separate wavelengths of the composite signal are separated and sent down different fibres to the optical receivers.

Mux and demux devices are usually passive, requiring no power supply or maintenance to function correctly.

Optical add/drop multiplexers

Optical add/drop multiplexers (OADMs) are installed at intermediate points along a transmission line. They enable new signals to enter the network and existing signals to leave, separating or rerouting different wavelength channels.

Most signals simply pass through the OADM unchanged, but some are dropped by splitting them from the line. At the same time, signals originating at that point can be added and transmitted to another destination.

Reconfigurable optical add-drop multiplexers (ROADMs) are now widely used, allowing the routing and rerouting of any wavelength in any direction.

Optical amplifiers

Optical amplifiers enhance optical signals by directly stimulating photons, increasing amplitude and strengthening the signal.

They’re built into the fibre and can amplify signals over a wide range of wavelengths. A vital part of DWDM systems, they greatly extend the transmission distances of DWDM equipment.

RAMAN amplifiers can be used to allow transmission over longer distances.

Optical transponders

An optical transponder, also known as an O-E-O (optical-electrical-optical) wavelength converter, is a crucial signal transmission component. It gathers incoming optical signals from the client service and converts them to outgoing optical wavelengths compatible with DWDM components.

First, it converts the optical signal into an electrical signal. It then performs either 2R (reamplify and reshape) functions or 3R (reamplify, reshape and retime) functions. Finally, it converts the signal back into an optical signal, hence the name O-E-O.

What is DWDM used for?

Faced with an explosion of data fuelled by the adoption of AI, 5G and IoT, businesses are looking to boost their network capacity. They use DWDM to greatly increase the bandwidth and reach of their optical networks.

With DWDM, you don’t need to install new cables, avoiding the huge costs and long lead times of fibre infrastructure upgrades. Instead, you can fully realise the investment in your existing network by enabling different data streams to be sent simultaneously over a single optical fibre.

While DWDM hardware can be more expensive than other solutions, the cost is justified by significant financial and time savings. In addition, amplifiers serve as repeaters, mitigating optical power loss and enabling DWDM operation over long distances.

Overall, DWDM provides tremendous scalability, reliability and reach for fibre optic networks. Without it, many cloud computing solutions would not be possible, and infrastructure overheads would be significantly higher.

Is DWDM the same as Dark Fibre?

A Dark Fibre network consists of ‘unlit’ fibre optic cables with no service or traffic running on them. You deploy and manage the equipment needed to light it.

DWDM is a technology you can deploy to enhance your network efficiency and maximise capacity. However, running your own DWDM service requires significant IT resources and expertise to deploy and maintain your network.

If you don’t want the upfront costs and hassle of Dark Fibre, consider a managed DWDM solution.

Learn more about Dark Fibre vs DWDM

DWDM solutions for your business

At Neos Networks, we’re helping businesses nationwide transform their networks with DWDM-enabled Optical Wavelengths up to 400Gbps.

If you’re looking to upgrade your network to meet the exploding demand for bandwidth, get in touch.


We’ll be happy to design a high-capacity DWDM solution for your business.

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