CWDM and DWDM, the "two brothers" in fiber optic communications, differ by only one letter in their names, but the difference is huge! Today, this article will explain the core differences and help you quickly distinguish them.

Ⅰ. Transmission Capacity: Worlds Apart

Technically, both rely on wavelength division multiplexing (WDM) technology, but they differ significantly in key parameters.

DWDM (Dense Wavelength Division Multiplexing) has an ultra-small wavelength spacing (0.8-2nm), which can accommodate dozens or even hundreds of wavelengths. A single optical fiber can easily handle Tbit/s-level bandwidth, making it a true "highway" suitable for ultra-large-scale transmission in backbone networks, data center interconnections, and other applications.

CWDM (Coarse Wavelength Division Multiplexing) has a wide wavelength spacing (20nm), generally with a maximum of 18 wavelengths. Its capacity is mostly in the hundreds of Gbit/s level, like a "city expressway," which is sufficient but not excessive.

Ⅱ. CWDM vs. DWDM

Ⅲ. Selection Tips:

CWDM uses "loose lanes" for short-distance, low-cost operations; DWDM uses "dense lanes" for long-distance, high-capacity operations.

5G fronthaul, campus interconnection, and temporary links → CWDM;
inter-provincial backbone, data centers , and 200km+ links → DWDM.

Simply put, DWDM is "performance-focused" while CWDM is "price-performance-optimized." Which one do you use more often in your projects? Let's discuss in the comments section.

About ETU-LINK

ETU-Link Technology Co., Ltd., founded in 2014, is a high-tech enterprise specializing in the research, development, production, and sales of optical communication components. With high-speed optical modules as its core product, the company specializes in serving the fiber optic communication markets, including telecommunications, data communications, and storage.