What is 100G QSFP28 4WDM Optical Transceiver?

When it comes to optical fiber communication, you should probably heard about the concept of wavelength division multiplexing(WDM) technology. WDM is an important way of communication capacity expansion at present. In short, it is a technology that two or more optical carrier signals with different wavelengths are combined by a wave splitter at the transmitting end and separated by a wave splitter at the receiving end. The advantage is that the use of optical fiber is greatly reduced, thus reducing the construction cost.  fibermall types of WDM

However, wavelength division multiplexing (WDM) technology can be divided into several different types according to different wavelength intervals. The main types of WDM are: CWDM (Coarse Wavelength Division Multiplexing), DWDM (Dense Wavelength Division Multiplexing), SWDM(Short Wavelength Division Multiplexing), LWDM(Long Wavelength Division Multiplexing), etc. 

Then, what is 4WDM?

The so-called 100G QSFP28 4WDM is a 4WDM optical module with a transmission rate of 100G and in the form of QSFP28 package. 4WDM is 4-channel wavelength division multiplexing. Then, the CWDM4 optical module is also a four-way wavelength division multiplexing. So is there any difference between the two?

 

To summarize:

·CWDM4 is applied to 2km; 4WDM is applied to 10km, 20km, 40km three scenarios.

·2km and 10km using 1271nm, 1291nm, 1311nm, 1331nm wavelength; and 20km and 40km wavelength interval becomes smaller, respectively 1295.56nm, 1300.05nm, 1304.58nm, 1309.14nm.

·40km using APD ROSA.

Some of the standards for WDM technology are set by the organization Multi-Source Agreement (MSA), which is like a law that must be followed in our human society. And the protocol for 100G QSFP28 4WDM optical modules is set by the 4WDM MSA. Depending on the transmission distance, this organization has developed different schemes for optical module manufacturers.

Generally, the 4WDM optical module is the same as CWDM4 optical module, both are quad-wavelength-division-multiplexing. But the former has a small wavelength spacing, and is temperature sensitive, and is suitable for long distance scenarios from 20km to 40km. The latter does not require a cooled laser, consumes less power, and is suitable for scenarios from 2km to 10km. For this reason, the QSFP28 100G CWDM4 is more popular.

At present, only a few optical transceiver manufacturers can provide 4WDM 40km transceivers, including Finisar, Oclaro, Eoptolink and Fibermall, etc. The following table shows the main characteristics of the four brands:


From this table, we can see that the only difference is "power consumption". The power consumption of Fibermall's 4WDM 40km optical transceiver is only 3.8W. Generally, for 40km products, EML (Electric Absorption Modulation) is required for modulation technology; Fibermall breaks through the technical limit and adopts DML (Direct Modulation) scheme, which greatly reduces the additional power brought by EML.

In fact, these manufacturers also offer other transceivers that comply with the 4WDM-40MSA standard: Finisar and Oclaro also offer dual-rate QSFP28 4WDM transceivers for 100GE and OTU4, which can be used not only for DCI applications but also for optical transport networks; Fibermall offers industrial-grade temperature for 5G mid- and backhaul ( -40℃~85℃) QSFP28 4WDM-40 optical modules, which is undoubtedly a further improvement of 5G technology solutions.https://www.fibermall.com/