WDM 101: Why Wavelength Division Multiplexing Carries So Much Promise
Light has fascinated humanity ever since we first glimpsed the sunrise. Over the years, we've advanced our understanding of light – how to measure it, where it comes from, how it travels – and built our knowledge of the universe as a result. Fifty years ago, we learned how to effectively transmit light signals over long distances with a revolutionary new material: optical fiber.
Today, one of the latest, and most high-impact, innovations in light allows us to manipulate the spectrum of wavelengths that comprise light. It’s called wavelength division multiplexing (WDM), and it carries great potential to help network operators stay ahead of growing demands for bandwidth.
Think of light passing through a prism: You’ve probably seen the rainbow that materializes as the light splits into a variety of colors. Each of these colors represents a set of wavelengths -- a "band" which we can isolate and manipulate independent of the other colors. In telecommunications, we utilize light to transmit information through fiber optic cables, often in the form of a red or green laser. When we do that, we're utilizing all the wavelengths within the "red" or "green" part of the spectrum, without isolating individual wavelengths. With WDM, that laser can be split into its constituent wavelengths -- meaning the same information which previously occupied a whole "color" of wavelengths, now occupies just a fraction. That’s why WDM is so promising when it comes to boosting the capacity of networks.
WDM is deployed within a network via products called a "Multiplexer" (mux) and "demultiplexer” (demux). These are essentially lenses attached to the active equipment (lasers) that allow us to manipulate the individual wavelengths within the laser transmitting light down the fiber. A transmission of light -- representing a phone call, a text, a video – is then sent through the laser and channeled by the Mux into a distinct wavelength. This then travels the length of the fiber alongside other transmissions on different wavelengths. The transmission is then received and processed by the demux which separates the individual signals into a form that the transceiver receiving the information can understand.
You can see where this is going: As we continue to split the light into more and more wavelengths, the potential capacity of just a single fiber strand grows dramatically.
It's important to note here that the technology behind WDM is rapidly developing -- we haven't yet reached the limit on how many distinct wavelengths we can channel through a single strand of fiber. Coarse Wavelength-Division Multiplexing (CWDM), the first generation of WDM, offers up to 18 channels. Dense Wavelength-Division Multiplexing (DWDM), a new iteration, offers up to 160 channels. A major concern in today’s connected world is fiber exhaust, where the demands for fiber exceed the amount of available fiber in the network. The evolution of WDM technology can alleviate fiber exhaust, by requiring fewer fibers to transmit and receive multiple services.
With demand for bandwidth growing constantly, operators are looking at all possibilities to accelerate capacity deployments in their networks -- be they data centers, urban cellular networks, or even the long-haul networks that connect cities. The core value of WDM is that it allows operators to increase capacity without laying extra cable in the ground. That’s especially important in congested areas where it’s hard to find space to lay additional cable. Given the bandwidth demands currently facing operators, WDM technology is increasingly being utilized in deployments across the world.
Network deployments are often viewed in two categories: greenfield and brownfield. Greenfield deployments are new construction -- building a network on "green", undeveloped land. Brownfield builds occur in already-developed spaces, where one has to work with – or around -- existing infrastructure. In greenfield environments, additional fiber can easily be added in the planning process. In brownfield environments, however, you can't always just add additional fiber given the existing space constraints. This makes accommodating the bandwidth requirements of 5G, IoT, and Smart Communities particularly challenging. In these environments, WDM is a key component enabling a connected future.
The pace at which WDM technology is innovating means there are always new developments in the technology and how to best implement it. Staying up-to-date on the capabilities and best-practices associated with WDM products can be overwhelming. Corning’s engineers are constantly working to help network operators make the most of WDM technology, and we want to share our expertise with you. Click here to get in contact with our engineers, who can help you to maximize WDM within your network.