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What is the difference between CWDM and DWDM

WDM stands for wavelength division multiplexing. It’s a technique for combining signals of different wavelengths for transmission through optical lines. Multiple data streams can be delivered on the same optical cable without interfering with each other since each data stream has its own wavelength. It is like increasing the number of lanes on a highway to improve the efficiency of traffic flow. WDM helps optimize network investment by maximizing the utilization of optical fiber.

What is CWDM?

CWDM stands for Coarse Wavelength Division Multiplexer. It can be used on a variety of fiber optic networks and is most commonly used in point-to-point topologies in enterprise and telecom access networks.

Multiplexer modules for CWDM are available in four channel, eight channel, and sixteen channel variants. These modules passively multiplex optical signals from various electronic devices, route optical fibers to them, and then demultiplex the signals into individual, distinct signals for input to the device at the other end of the optical fiber link.

What is DWDM?

DWDM is an abbreviation for Dense Wavelength Division Multiplexer. Because DWDM uses tighter wavelength spacing to install more channels on a single fiber, the number of multiplexed channels in DWDM systems is substantially higher than in CWDM systems.

Multiple DWDM channels are multiplexed onto one or two optical fibers using DWDM multiplexer/demultiplexer modules.

Difference between CWDM and DWDM


The spacing in CWDM is greater than in DWDM. This means that CWDM can handle up to 18 channels on a single fiber pair, but DWDM can support up to 40, 80, or 96 channels. The channel spacing in DWDM is 0.8/0.4nm, while the channel spacing in CWDM is 20nm.

Transmission Distance

The transmission distance of CWDM is less than that of DWDM. Because the wavelength of DWDM is well integrated with the optical fiber during optical transmission, DWDM can cover a greater distance than CWDM. CWDM, on the other hand, cannot be propagated over long distances since CWDM wavelengths cannot be amplified by EDFA amplifiers; hence it is limited to 100 miles (160 kilometers).


Since the DWDM system’s wavelengths are closely spaced, they must maintain a more stable frequency than CWDM systems with larger channel spacing. As a result, they require cooled lasers, whereas CWDM systems require uncooled lasers.


Equipment for DWDM is usually more expensive than equipment for CWDM. However, because DWDM is more widespread, DWDM transceivers are less expensive than CWDM transceivers. The number of channels accessible on a single link is greatly reduced due to the broader CWDM channels, although optical interface components do not need to be as precise as DWDM components. As a result, CWDM equipment is significantly less expensive than DWDM equipment.


The decision between CWDM and DWDM is mostly based on your own requirements. If you wish to send more data to more distant locations, DWDM is the way to go. If you simply need to send data over small distances and want to save money, CWDM is the way to go.

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