Differences between CWDM and DWDM

Coarse Wavelength Division Multiplexing (CWDM) and Dense WaveLength Division Multiplexing (DWDM) are two kinds of wavelength-division multiplexing (WDM) which is a technology multiplexing a number of optical carrier signals onto a single optical fiber by using different wave lengths of laser light. Seeing from their development, DWDM came well before CWDM. DWDM appeared only after a booming telecommunications market, driving prices to affordable lows. Whereas CWDM breaks the spectrum into big chunks. Here is some information related to the differences between CWDM and DWDM.


CWDM is a method of combining multiple signals on laser beams at various wavelengths for transmission along fiber optic cables. Its WDM system has less than 8 active wavelengths per optical fiber.
DWDM is a fiber-optic transmission technique that employs light wavelengths to transmit data parallel-by-bit or serial-by character. Its WDM system has more than 8 active wavelengths per optical fiber.

Each CWDM wavelength, which can be expanded to 10Gbps support, typically supports up to 2.5Gbps. This transfer rate is sufficient to support GbE, Fast Ethernet or 1/2/4/8/10G FC, STM-1/STM-4/STM-16 / OC3/OC12/OC48 and other protocols. However, since the optical amplifiers cannot be used due to the large spacing between channels, the CWDM is typically deployed at networks up to 80Km.
Providing up to 96 wavelengths (at 50GHz) of mixed service types, the DWDM systems can transport to distances up to 3000 km through the deployment of amplifiers and dispersion compensators, which increases the fiber capacity by a factor of x100. Today’s DWDM solution is often embedded with Reconfigurable Optical Add Drop Multiplexer (ROADM). The ROADM enables the building of flexible remotely managed infrastructure in which any wavelength can be added or dropped at any site.

The function of CWDM is to help carriers make the best of their network capacity in the regional, metro and access network sectors. Comparing with DWDM, CWDM supports fewer wavelengths; but it is much cheaper than DWDM. Thus CWDM is the perfect choice for those areas having average traffic growth projections.
Since the laser of DWDM is more precise and stable, it tends to be more expensive at the sub-10G rates. However, for 10G service rates, it is a more appropriate solution,which provides large capacity data transport and connectivity over long distances at affordable costs.

Due to fewer number of layers in the filter design, the filter of CWDM is inherently less expensive to make than that DWDM. Typically, there are over 100 layers required for a 200 GHz filter design as used in metro DWDM products, where there are only 50 layers in a 20 nm filter used in Metro CWDM products. The result is shorter manufacturing time, less materials and higher manufacturing yields for CWDM filters. As a result, CWDM filter costs are generally less than 50 percent of the cost of comparable DWDM filters.

CWDM networks use CWDM modules such as CWDM MUX/DEMUX and CWDM OADM. While DWDM MUX/DEMUX and DWDM OADM are used in DWDM networks. A series of WDM modules are provided in Fiberstore, which enable the expansion of existing fiber capacity.

Add Comment Register

Leave a Reply