Have you noticed that there are some SFP modules with colorful markings on the market? For SFP, we are not unfamiliar. SFP (Small Form-Factor Pluggable) is a compact, hot-pluggable transceiver used for both telecommunication and data communication applications. But do you know why they are designed with different colors?

 

 

 

 

These colorful SFP modules are called WDM (Wavelength Division Multiplexing) SFPs. WDM is a technology which combines two or more kinds of optical signals at different wavelengths and transmits them on a single optical fiber. By using WDM technology, SFP module can transmit signals at different wavelengths, which are identified by different colors. WDM SFPs can be divided into two basic types. One is CWDM (Coarse Wavelength Division Multiplexing) SFP, and the other one is DWDM (Dense Wavelength Division Multiplexing) SFP. The following passage is mainly about CWDM SFP.

 

 

Overview of CWDM SFP

 

CWDM SFP is a kind of optical transceiver which uses CWDM technology. Similar with traditional SFP module, CWDM SFP is also a hot-pluggable transceiver that interfaces a network device port (of a switch, router, media converter or similar device) to a fiber optic networking cable.

 

 

Generally speaking, CWDM SFP modules come in 8 wavelengths that range from 1470 nm to 1610 nm. Through the color markings on the devices, it is easy to identify the wavelength to which the Gigabit Ethernet channel is mapped. That is why SFP modules are designed with different colors. The following table lists the CWDM SFP modules with their wavelengths and color codes.

 

 

 

 

In addition, CWDM SFP is a compatible transceiver which provides data rates from 100 Mbps up to 4 Gbps, and reach a transmission distance at 20 to 40km, 40 to 80km and 80 to 120km. CWDM SFP modules also feature digital diagnostics, also known as digital optical monitoring (DOM), which is supported by the majority of switch and router OEMs in their operating system software.

 

Application

CWDM SFP is a MSA standard build and it is designed for operations in Metro Access Rings and Point-to-Point networks using Synchronous Optical Network (SONET), SDH (Synchronous Digital Hierarchy), Gigabit Ethernet and Fiber Channel networking equipment. For it is low in cost, CWDM SFP can be regarded as a convenient and cost-effective solution for the adoption of Gigabit Ethernet and Fibre Channel (FC) in campus, data-center, and metropolitan-area access networks.

 

 

Comparison With DWDM SFP

 

DWDM (Dense Wavelength-Division Multiplexing) SFP transceivers are used as part of a DWDM optical network to provide high-capacity bandwidth across an optical fiber network, which is a high performance, cost effective module for serial optical data communication applications up to 4.25Gb/s. From a low cost point of view, CWDM SFP module is inexpensive than DWDM SFP. For other aspects, the key in selecting CWDM or DWDM SFP lies in the difference between CWDM and DWDM. They refer to different methods of splitting up the light. For example, CWDM uses broader spacing between channels, allowing for inexpensive SFPs, while DWDM uses denser channel spacing, which allows for more wavelengths to be used on a single fiber. DWDM is typically used in large optical networks over longer distance. Therefore, DWDM SFP module is the ideal choice for SFP modules over long distance and with better scalability.

 

 

Conclusion

 

Data communication and fiber optical network develop rapidly. During the process, some problems occur which push forward the improvement of the products. SFP modules, essentially just completed the converted of data between different media, can realize the connection between two switches or computers within a long distance. CWDM technology is an effective way to meet the rapidly increasing demand of bandwidth in transmission network, and it can provide a cost-effective solution for high capacity in metropolitan area network and local area network. As a functional and economical optical communication product, CWDM SFP, combined with the advantages of them, becomes more and more popular with users and applied to various fields.