Differences Between CWDM SFP and DWDM SFP

With increasing demand for cable capacity, WDM (wavelength division multiplexing) technology is designed for a better transmission in fiber optic communication. Nowadays, SFP (small form-factor pluggable) modules, combined with WDM technology, become more and more popular around the world, and there are two types of SFP modules—CWDM SFP and DWDM SFP. This article mainly introduces the differences between them and provides effective CWDM SFP&DWDM SFP solutions.

 

CWDM SFP—CWDM (Coarse Wavelength Division Multiplexing) SFP is a type of single-mode transceiver which combines CWDM technology. It is used for Gigabit Ethernet or fibre channel (FC) in campus, data center, and metropolitan area access network. Like traditional SFP modules, CWDM SFP is a hot-swappable input/output device that plugs into a SFP port or slot of a switch or router, linking the port with the fiber optic network. Generally, CWDM SFP modules come in eight wavelengths that range from 1470nm to 1610nm distinguished by different colors. Here is a picture of different color coded CWDM SFP modules:

 

 

DWDM SFP—DWDM (dense wavelength division multiplexing) SFP is a hot-pluggable transceiver used as part of a DWDM optic network to provide high-capacity bandwidth across a fiber optic network. DWDM SFP has so dense wavelength intervals that it can multiplex more than 80 separate wavelengths or channels of data into light stream transmitted on a single optical fiber. Therefore, DWDM SFP can maintain a more stable wavelength than CWDM SFP and it can be used for long distance optical transmission. But it is a high-cost device and energy consumption. An image of DWDM SFP is shown below.

 

CWDM SFP and DWDM SFP are both using multiple wavelengths of laser light for single transmission on a single fiber, but they still have many differences from the aspects of wavelength spacing, modulation laser, and transmission distance etc. The following part will compare CWDM SFP and DWDM SFP from these aspects.

• Wavelength Spacing—As their names imply, the words—“dense” and “coarse” reveal the differences of their wavelength spacing. CWDM SFP has a wider spacing than DWDM SFP. It can transport up to 16 wavelengths between 1270 nm to 1610 nm with a 20nm interval, while DWDM SFP can accommodate 40, 60, 80, or even 160 wavelengths with a narrow spacing of 0.8 nm, 0.4 nm or 0.2 nm from the wavelengths of 1525 nm to 1565 nm (C band) or 1570 nm to 1610 nm (L band). There is no doubt that DWDM SFP has a higher performance of transmitting a greater number of multiple wavelengths on the same link.
• Modulation Laser—CWDM SFP uses the uncooled laser while DWDM SFP uses cooling laser. Laser cooling refers to a number of techniques in which atomic and molecular samples are cooled down to near absolute zero through the interaction with one or more laser field. DWDM SFP with cooling laser, which adopts temperature tuning, has better performance, higher safety and longer life span than the electronic tuning uncooled laser used by CWDM SFP. But it will also consume more energy.
• Transmission Distance—Since the wavelengths are tightly packed, DWDM SFP can achieve a longer distance transmission, while CWDM SFP whose wavelengths are not amplified cannot support long distance. And thanks to amplified wavelengths, DWDM SFP can transmit more data over a significantly larger run of cable with less interference than a comparable CWDM SFP. Typically, the maximum transmission distance of CWDM SFP is up to about 100miles (160 km), whereas an amplified DWDM SFP can go much further as the signal strength is boosted periodically throughout the run.

 

1000Base-CWDM-SFP-1590, compatible with Gigabit Ethernet and IEEE 802.3z standard, transmits over single-mode fibers with LC connector interface. As its name suggests, the operating wavelength of 1000Base-CWDM-SFP-1590 is 1590 nm for a maximum transmission distance of 80 km. It also supports digital optical monitoring (DOM) which enables the end user to monitor temperature, voltage use, Tx power and Rx power of SFP optics.

 

DWDM-SFP1G-31.90-100 is designed for single-mode fibers with LC duplex interface and accommodates 57 wavelengths at a nominal wavelength of 1513.90 nm. As we all know, the wavelengths of DWDM SFP are highly integrated in the fiber during light transmission, so DWDM SFP is able to reach a longer distance than CWDM SFP. This kind of DWDM SFP can travel longer than the CWDM SFP module introduced above, up to 100 km.

 

To sum up, CWDM SFP and DWDM SFP have different features. CWDM SFP is less expensive, but its performance is far behind DWDM SFP. DWDM SFP can transmit further and has higher performance than CWDM SFP. however, it will cost more and consume more energy. People should understand these differences between CWDM SFP and DWDM SFP before choosing them. For example, if you are looking for SFP modules over long distance with high capability, DWDM SFP is the best choice. Besides the solutions mentioned above, FS.COM provides a whole series of CWDM SFP and DWDM SFP with high quality and great price to meet your requirement.