CWDM

Coarse Wavelength Division Multiplexing (CWDM) is a form of WDM that combines multiple optical signals on different wavelengths of light within a single fiber. It relies on relatively wide channel spacing, typically around 20 nanometers, and covers a broad spectral range in the near-infrared, commonly from about 1270 to 1610 nanometers. This coarse grid allows for simpler and lower-cost equipment compared with denser DWDM systems.

CWDM systems generally support a modest number of channels, often in the range of 4 to 18, depending on the hardware. The wide spacing enables the use of cost-effective, temperature-tolerant laser sources and less complex filtering. Because of these characteristics, CWDM is well suited for metro and access networks, as well as regional links where total capacity needs are moderate and budget constraints are a priority. The technology typically uses standard single-mode fiber and standard optical components, reducing deployment and maintenance costs.

Key components in a CWDM network include CWDM transceivers (such as SFP or SFP+ modules), CWDM multiplexers/demultiplexers, and optical filters or thin-film devices for channel separation. The system often does not require the stringent wavelength stabilization and dispersion management associated with dense WDM, making it attractive for shorter distances and simpler network architectures.

Standards governing CWDM are primarily defined by ITU-T, with G.694.2 detailing the CWDM wavelength grid and channel spacing. CWDM remains a cost-effective alternative to DWDM for appropriate applications, offering easier deployment and lower equipment costs at the expense of reduced channel count and spectral efficiency.