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Expand congested CWDM Links with DWDM Integration

The choice between CWDM and DWDM has traditionally been positioned as an exclusive one: CWDM for cost-effective links, and DWDM for high performance (in terms of speed, range, and channel capacity). However, in today’s DWDM transceiver market, fixed wavelength 10G DWDM transceivers have generally reached price parity with 10G CWDM transceivers. In situations where it may be difficult or time consuming to deploy additional fiber for DWDM, operators with a large installed base of CWDM services may find that inserting DWDM channels over existing CWDM links can allow them to cost-effectively expand network capacity, accelerate service deployment, and start leveraging the advanced capabilities of DWDM networks.   

DWDM over CWDM Integration Network Configuration 

Many operators are already using individual DWDM optics over the 1531nm and 1551nm ports on CWDM muxes, leveraging DWDM transceivers’ greater speed and range, and taking advantage of DWDM tuneable optics to implement quick-turnaround solutions. By taking the next step of connecting DWDM muxes into the 1531nm and 1551nm channel ports of their existing CWDM muxes, telecom service providers can add significant capacity to their links extremely quickly, thanks to the much greater number of channels available in the ITU-T G.694.1 DWDM grid.  

Figure 1Simple DWDM over CWDM Network Integration 

Capacity Expansion 

In a maximum DWDM integration implementation, up to 26 ITU standard 100GHz DWDM channels can be added into the 1531nm and 1551nm ports of a CWDM Mux. However, LambdaGain proposes a simplified approach using standard 8-channel DWDM muxes, connected to the CWDM 1531nm port and the 1551nm port, as shown in the accompanying diagram. This means that in a typical existing CWDM link using 8-channel CWDM muxes, service providers can easily increase capacity from eight wavelengths to 22 wavelengths. In turn, the total capacity of a link, which would previously have carried a maximum of 80 Gbps using 10 Gbps CWDM optics, can be increased to 220 Gbps using common 10 Gbps DWDM optics. With a migration to 25 Gbps DWDM optics, the capacity can be easily increased to 460 Gbps, and the option of even higher speed DWDM optics remains available for future upgrades. 

Engineering Considerations & Range 

The range achievable with an integrated DWDM + CWDM network will depend on a number of factors, including: 


  • Mux/Demux losses 
  • Optical gain of selected SFPs 
  • Engineering assumptions such as: fiber loss/KM, Patching and Connector margins, and so on. 


In the typical scenario shown in the diagram, with LambdaGain 10G tuneable optics and LambdaGain DWDM + CWDM muxes, an optical reach of 26 Km to 38 Km can be planned into the network, depending on the optics selected. Specific situations will require individual analysis. 

Business Benefits 

In metro access network environments, the ability to integrate 10G and/or 25G DWDM optics into existing CWDM fiber links presents several compelling advantages: 


Cost Efficiency & Time to Market: achieved by avoiding engineering and construction of new fiber circuits exclusively for DWDM, as well as the ability to use tuneable DWDM optics that can be cost-effectively kept in inventory 


Scalability: Operators can essentially triple the capacity of an existing 8-Channel CWDM link with minimum investment by adding two, 8-Channel DWDM muxes to the link (using 10 Gbps optics). Even more capacity can be added by cascading additional DWDM muxes via the first layer of DWDM muxes’ EXP port.  


Future Proofing: thanks to rapidly evolving DWDM optics, additional capacity could also be added by migrating to higher speed optics – 25 Gbps, 50 Gbps, and 100 Gbps.  Speeds beyond 100 Gbps can be supported with extended bandwidth DWDM muxes.  To find out more about extended bandwidth DWDM and their applications, click here 


Minimal Customer Impact: Adding a DWDM mux to expand capacity involves only a single port on the CWDM mux, minimizing impact of the network reconfiguration on customers and end-users, while significantly expanding capacity. 

LambdaGain Solution Elements

The LambdaGain solution is built around our high-performance family of low-loss CWDM and DWDM mux/demux units, and our family of fixed and tuneable DWDM 10 Gbps and 25 Gbps optics.  


The key solution elements that drive the success of our CWDM/DWDM integrated solution include: 

LambdaGain CWDM dual-fiber muxes are widely deployed in telecom service providers’ networks to increase capacity in access network backhaul links. They are compatible with ITU-T G.694.2 and form the foundation on which the new DWDM network is built.

LambdaGain DWDM dual-fiber muxes are available with Super Low Loss optical performance which is ideal for integration applications. They are compatible with standard ITU-T G.694.1 channels plans and support optical bit rates up to 100 Gbps. They also support EXP ports to connect expansion muxes for additional link capacity. Extended Bandwidth muxes are available for speeds beyond 100Gbps.v

Fixed-wavelength DWDM optics are now price competitive with CWDM optics at 10G speeds. Moreover, field wavelength tunable DWDM optics are cost-effective and simplify deployment logistics by reducing the number of SKUs required to deploy DWDM networks down to a single unit. They offer high power and high sensitivity for extended range performance and currently support both 10 Gbps and 25 Gbps speeds.


Integrating DWDM networks into existing CWDM infrastructure using 10G fixed wavelength DWDM optics and DWDM passive mux/demux modules provides a cost-effective, accelerated solution for expanding the capacity of congested CWDM backhaul links. Depending on the number of extra channels added, tunable 10G optics can be considered to simplify operations and reduce inventory complexity, cut down OPEX, and accelerate deployments. Integrated DWDM + CWDM networks can be a powerful tool for operators facing fiber shortages that could impede DWDM migration while also minimizing the disruption to in-service customers on the CWDM link.

Contact Us 

Interested in learning more about how passive DWDM technology can optimize your cable network’s transition to Distributed Access Architectures (DAA)? Don’t hesitate to reach out to us! Our team of experts is ready to discuss your specific needs, provide tailored solutions, and guide you through the implementation process. Contact us today to start the conversation and take the first step towards a more efficient and scalable network infrastructure. 

About FONEX Data Systems inc. 

FONEX data systems inc. (FONEX), delivers optimised, purpose-built solutions for wireline and wireless telecommunications service providers across Canada, the USA, and Europe. We combine over 30 years of expertise in telecommunication architectures, standards, and trends with a leading-edge portfolio of carrier-class products to meet and exceed our customers’ business, technical and operational requirements. Find out more about FONEX here.  


Fernando Donoso

Product Marketing Manager