No matter what kind of network you maintain, you always have the same demands: more speed, less cost, and larger capacity. For any network with heavy demands on data and/or distance, this always results in implementing fiber optics. This is technology that grows and shifts every day, and it can be exhausting to stay on top of the mountains of information out there. To help with that, a few simple explanations of popular fiber optic tech can make your life a lot easier. In that effort, today’s lesson is on CWDM technology. It’s one of several fiber optic cable choices, and it can fill many roles.

What Is CWDM?

The acronym stands for Coarse Wavelength Division Multiplexing. As the name states, it is a form of multiplexed fiber optics, so CWDM networks can send simultaneous, two-way communication. The term “coarse” refers to the wavelength spacing between channels. CWDM utilizes laser signals that differ in increments of 20 nm. A total of 18 different channels are available — with a wavelength range from 1610 nm to 1270 nm — and 8 can be utilized in a single system. Since each channel is capable of data rates of 3.125 Gbps, the aggregate ability is 10 Gbps for any CWDM cable.


Sometimes, it’s easier to understand the value of a piece of technology by comparing it to alternatives. In wavelength division multiplexing, DWDM (Dense WDM) is the other popular choice. DWDM has a wavelength spacing of 0.4 nm. That enables a denser packing of signals (hence the name) and can produce much higher data rates — up to 100 Gbps. The primary difference between CWDM and DWDM is that chromatic spacing. While DWDM can send and receive more information, the smaller differences reduce the tolerance of the signal and require far more precision in the laser design. This is why DWDM is much costlier per foot of cable than DWDM.

Where Is CWDM Best Used?

With high data rates, a low cost and good transmission range (up to 60 km), CWDM shines in many instances. It’s best at city-level applications. Many broadband internet providers build the bulk of their infrastructure on CWDM lines. Large campuses and data centers also benefit from integrating CWDM.


One of the often overlooked advantages of coarse WDM is its compatibility with both GBIC and SFP connections. This makes it ideal for upgrading legacy systems that still use the older interface.


To summarize, CWDM is ideal for fast and long networks that don’t need more expensive speeds. It’s also ideal for a gradual upgrade of older systems.


The most important thing to remember is that you never have to marry a cable choice. Networks are living animals, and you’ll always find various niches within the design. CWDM can be your flexible line that keeps your options open, but you can still utilize other cable designs where the need arises.