What is Wavelength Division Multiplexing (WDM)?

Posted by Jonathan Benfield on Tue, Apr 20, 2021 @ 08:04 AM

What is Wavelength Division Multiplexing (WDM)?

WDM is a technology approach that allows for the combining ("mux") of multiple individual light wavelengths (signals/channels) from multiple lasers on a single fiber using a passive component for transmission to another location. At that receiving location, WDM components then work in the reverse, demultiplexing ("demux") the combined wavelengths back into individual signals and routed to their respective receivers.  

While other components used in a network like an optical splitter may seem similar to a WDM, it’s important to differentiate the two as they address different applications. Optical splitters simply split a complete light signal into the desired ratio. For example, a 1x2, 50/50 splitter will split the total amount of light being transmitted in half with 50% going to each respective output fiber. By contrast, a 1x2 WDM (demux) will take a transmitted signal composed of multiple wavelengths, say 1310nm and 1550nm for simplicity, and divide them into their individual wavelengths (1310nm to one output and 1550nm to the other. Unlike optical splitters that simply divide the total light signal, WDMs are targeted at the wavelength level.  

It’s not uncommon to sometimes hear an engineer say they need a "filter" to break out a specific wavelength or range of wavelengths for an application, which would require a WDM component.  A real-world scenario could include utilizing a 1625nm or 1650nm WDM/filter with a fiber monitoring system, to ensure routing only that monitoring signal back to the device while letting all other data signals pass accordingly.

WDM Transport Diagram
Image Credit:  ChampionOne

Why Use WDM?

Multiplexing technology was developed to support transmitting multiple signals across a single fiber (or fiber pair in the case of a complete link) to increase bandwidth capacity. Multiplexing offers a far more cost-effective option to increase bandwidth vs. installing or purchasing individual fibers for every wavelength. The result is much higher data capacity and efficiency when, for example, 18 wavelengths/channels using Coarse Wavelength Division Multiplexing (CWDM) can be combined onto a single fiber rather than installing and using 18 individual fibers. As the name implies, Dense Wavelength Division Multiplexing (DWDM) offers even more density with 40 or 80 channels/wavelengths possible.

Today, some transceiver modules for the 40G, 100G, 400G+ have multiplexers built inside the module, so an additional passive component is not required. The transceiver can simply connect directly into a standard network fiber pair and the signals are already multiplexed, saving additional hardware, rack space, and cost for managing the transmitted and received signals.


Is WDM New?

The short answer is "no", as this technology was developed many years ago and has been deployed across global networks in one form or another to a significant degree. According to an article back in 1997 from the International Society for Optics and Photonics, “To our knowledge, it [WDM] dates back at least to 1958, to an IEEE paper by R. T. Denton and T. S. Kinsel. About 20 years later, the first practical components for multiplexing were proposed from different laboratories, mainly in the U.S., Japan, and Europe.” 


Coarse Wavelength Division Multiplexing (CWDM) vs. Dense Wavelength Division Multiplexing (DWDM)

As mentioned above, Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM) are two forms of WDM technology that extend the capabilities of WDM and address increasing bandwidth capacity requirements.  Typically, DWDM is preferred for long-distance data transmission because the connection can be amplified. 


Need a Customized WDM Solution?

M2 Optics offers a complete portfolio of WDM solutions built to your exact specifications that allow for achieving system objectives in the most efficient manner. Whether the need is a small channel count Optical Add-Drop Multiplexer (OADM) module, or a full 80 channel DWDM mux/demux rack-mount platform, M2 can support your requirements. 

WDM Optical Filter Module

Some example applications can include:

  • Wavelength Multiplexers for increasing bandwidth capacity on existing fibers
  • WDM Filters for routing specific wavelengths to monitoring equipment
  • Add/Drop Multiplexers for adding/dropping wavelengths along a network route
  • Aggregation / CEx Multiplexers for managing different provider services (ex: Ethernet, P2P, FTTx, and Monitoring) on the same fiber

Simply contact us with your requirements and our team will build a customized solution that delivers maximum ROI for your network infrastructure.

 

Topics: wavelength filtering, WDM, cwdm, dwdm, wavelength division multiplexing