DWDM (Dense Wavelength Division Multiplexing) and CWDM (Coarse Wavelength Division Multiplexing) are both technologies used in fiber optic communication to increase the capacity of a single optical fiber by combining multiple signals onto different wavelengths of light. However, there are some key differences between the two:

1.Wavelength Spacing: DWDM uses a very narrow channel spacing, usually 0.8 nm or less, which allows for a high number of channels to be multiplexed onto a single fiber. CWDM, on the other hand, uses wider channel spacing, typically 20 nm or more, which limits the number of channels that can be multiplexed onto a single fiber.

2. Channel Count: Due to the narrower channel spacing, DWDM can support a higher number of channels, usually up to 80 or more, compared to CWDM, which typically supports up to 16 channels.

3. Transmission Distance: DWDM is typically used for long-haul and high-capacity applications, as it can support transmission distances of hundreds of kilometers. CWDM is more commonly used for shorter distances, such as within a data center or metropolitan area network.

4. Cost: CWDM is generally considered to be a more cost-effective solution than DWDM, due to its simpler and less complex technology.

Overall, DWDM is better suited for high-capacity and long-distance applications, while CWDM is more suitable for lower capacity and shorter-distance applications.