CWDM SFP or DWDM SFP? Which Is Your Option?

Small Form-Factor Pluggable (SFP) is designed to meet Multi-Source Agreement (MSA), 1 to 2.5 Gigabit Ethernet, Fibre Channel, and other communication standards to ensure network equipment compatibility. SFP transceivers are available with a variety of form factors, which allow users to select the appropriate transceiver for each link to provide the required optical reach over the available optical fiber type. It is used for both telecommunication and data communication. SFP has many types, such as 100BASE SFP, 1000BASE SFP, BiDi SFP... we would mainly introduce CWDM SFP, DWDM SFP and their differences in this text.

CWDM SFP

Extended from wavelength division multiplexing(WDM), Coarse Wavelength Division Multiplexing (CWDM) is used to increase the bandwidth of an optical fiber by multiplexing several wavelength onto it. Using 18 channels with wavelengths between 1270 nm and 1610 nm, it improves the transmission speed a lot. A CWDM SFP transceiver is a hot-swappable input/output device that plugs into an SFP port and links the port with the optic fiber network. CWDM equipment is designed for short-range communications and is mainly used for city and access networks. the CWDM SFP has many types with different color, just like the rainbow. Besides, color markings on the devices identify the wavelength to which the Gigabit Ethernet channel is mapped.

DWDM SFP

DWDM (Dense Wavelength Division Multiplexing) SFP transceivers are another type of WDM SFP transceivers after CWDM SFP. DWDM is designed for long-haul transmission where wavelengths are packed tightly together in order to increase bandwidth over existing fiber networks. And DWDM uses much more than 18 channels with wavelength for a much wider channel spacing compared to CWDM. DWDM uses denser channel spacing, which allows for more wavelengths to be used on a single fiber. There are 32 fixed-wavelength DWDM SFPs that support the International Telecommunications Union (ITU) 100-GHz wavelength grid. Establishing transport connections as short as tens of kilometers to enable nationwide and transoceanic transport networks, DWDM SFP is working hard for keeping the data highway alive and expanding.

Differences Between CWDM SFP and DWDM SFP

• Channel—CWDM uses broader spacing between channels and DWDM uses denser channel spacing, which allows for more wavelengths to be used on a single fiber. CWDM provides up to 16 channels across multiple transmission windows of silica fibers. Dense wavelength division multiplexing uses the C-Band (1530 nm-1565 nm) transmission window but with denser channel spacing. Channels plans vary, but a typical DWDM system would use 40 channels at 100 GHz spacing or 80 channels with 50 GHz spacing. Thus, DWDM SFP uses more channels than CWDM SFP.
• Wavelength and Distance—From the above statements, we are clear that there are many different wavelengths of CWDM SFP, such as 1271 nm, 1291 nm, 1310 nm... The minimum wavelength of CWDM SFP is 1271 nm while the maximum wavelength is 1611 nm. The maximum transmission distance of it is 120 km. Designed for a long-haul transmission distance, the maximum wavelength of DWDM SFP is 1620 nm and the maximum transmission distance is 200 km.
• Cost—CWDM uses broader spacing between channels, which allows for inexpensive SFPs to use. DWDM provides ultimate scalability and reach for fiber networks. Boosted by Erbium Doped-Fiber Amplifiers (EDFAs)—a sort of performance enhancer for high-speed communications, DWDM systems can work over thousands of kilometers. Most commonly, CWDM SFP is around 45$ while DWDM SFP is 200$. So the price of DWDM SFP is nearly 5 times of CWDM SFP. You can see the price more clearly in the following cable.

Summary

CWDM SFP and DWDM SFP are two types of SFP transceivers used to support 1 to 2.5 Gbit/s Ethernet, both of them are of great capacity and quality. For short distance transmission and money-saving, CWDM is suggested. For long distance and higher speed, DWDM is available with huge capacity and good performance. You can choose a right one according to your requirement.