The two key WDM technologies are Coarse Wavelength Division Multiplexing, CWDM and Dense Wavelength Division Multiplexing, DWDM. Which solution is best suited to a given environment depends on the network and user requirements.
CWDM:Coarse Wavelength Division Multiplexing (CWDM) is a wavelength multiplexing technology for city and access networks. Transmission is realized using 18 channels with wavelengths between 1270 nm and 1610 nm. Due to the channel spacing of 20 nm cost-effective lasers can be used. The channel width itself is 13 nm. The remaining 7 nm is designed to secure the space to the next channel.
DWDM principle:The functionality of DWDM (Dense Wavelength Division Multiplexing) resembles to the one of CWDM. The DWDM channel spacing is 0.8/0.4 nm (100 GHz/50 GHz grid). This small channel spacing allows to transmit simultaneously more information. Currently a restriction on wavelengths between 1530 nm and 1625 nm exists which corresponds to the C and L band. DWDM wavelengths are more expensive compared to CWDM caused by the need of more sophisticated transceivers.
This table shows the comparison between CWDM and DWDM.
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Item |
CWDM |
DWDM |
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Definition |
Up to 18 different CWDM wavelength over one pair of fiber
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Up to 96 DWDM wavelength over one pair of fiber |
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Highlights
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• Up to 18 CWDM wavelength over one pair of fiber • CWDM channel spacing 20 nm, 1270 nm to 1610 nm • Distances up to 120 km • Cost-effective WDM solution • Scalable by hybrid CWDM/DWDM - perfect solution for your investment |
• Up to 96 DWDM wavelength over one pair of fiber • DWDM channel spacing 0.8 nm (100 GHz grid) or 0.4 nm (50 GHz grid) • Distances over 1,000 km can be achieved with the use of optical amplifier • DWDM wavelength: 1528 nm (channel 61) to 1563 nm (channel 17) |
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Technical Details
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ITU-T G.694.2 λ: 1271 nm - 1611 nm Max. 18 channels can be used due to the waterpeaks Channel spacing: 20 nm |
ITU-T G.694.1 C-Band λ: 1530 nm - 1565 nm max. 360 channels (12,5 GHz Grid) L-Band λ: 1565 nm - 1625 nm max. 560 channels (12,5 GHz Grid) |
The two key WDM technologies are CWDM and DWDM. Which solution is best suited to a given environment depends on the network and user requirements.
The sweet spot for CWDM is up to 10 Gigabit Ethernet and 16G Fibre Channel. And it is quite unlikely capacities with increase beyond this in the future. DWDM however, is able to handle higher speed protocols up to 100Gbps per channel making it a more suitabletechnology for higher speed protocols.
Traditionally CWDM components have been lower in cost making it more popular than DWDM. Now the price for both solutions is comparable. With higher speeds, more channel capacity, longer distances and passive networking, DWDM is the technology of choice for green field installations.