CWDM VS DWDM: Who Is The Best Choice For WANs

- Sep 01, 2020-

Background: Limited fiber resources;WANs bandwidth urgently needs to increase.

In recent years, As the number and types of users increase, the pressure on network capacity gradually shifts to WANs.


The features of WANs:

Short transmission distance;

Flexible access;

Wide bandwidth;

Diverse and complex business;

Lower power consumption;

Lower cost.


The differences of specifications between CWDM and DWDM:

Comparison item



Wavelength/frequency interval


50GHz 0.4nm

100GHz 0.8nm

200GHz 1.6nm

Range of wavelength

1270~1610nm, Maximum 18 bands

1528.77~1563.86nm,100GHz maximum 48 bands,50GHz maximum 96 bands

Allowable wavelength deviation




Without/with cooler(1G/10G)

Cooled laser(1G/10G)

System with or without amplifier

No (CWDM can use RA)

Yes (EDFA, RA)

TIU-T agreement



Monitoring Channel



Therefore, CWDM technology has the same core technology as DWDM. But CWDM has the advantages of low cost and low power consumption.

In result, the use of CWDM technology to build a WANs or network expansion is one of the most effective and economical ideal choices, which can greatly reduce networking costs, adapt to the continuous enrichment and increase of services, and solve the cost-effective problem of WANs expansion.

At present, CWDM technology is relatively mature and the products are relatively simple. It can be applied to the access layer and convergence layer of the metropolitan area network, but cannot be used in the core layer.

Because the 2.5Gbit/s bearer service rate and the capacity of only 8 waves of the CWDM system in the core layer of the metropolitan area network cannot fully meet the requirements of the core layer of the metropolitan area network, but for the access layer and convergence layer of the WANs.

In other words, generally the number of wavelengths required does not exceed 8, and most of the current CWDM systems can provide 8 wavelengths.

5G networks

At the same time, there are often some cases of long transmission distance and limited optical fiber resources in the local network.

The low-cost characteristics of the CWDM system can play the extreme between the transmission distance of 0~50km, so the CWDM system is used in the metro edge network and the local network. Only by following can we truly show our competitive advantage.

With the substantial increase in the amount of network communication data and the continuous increase of optical communication network capacity, CWDM technology will become an ideal low-cost solution for metropolitan area network construction with its characteristics of low cost, flexible topology, and multiple types of access services.

From this we can also predict that the future development trend of CWDM and DWDM is not to replace each other, but not to supplement.