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Accelerate DAA rollouts using Passive DWDM

To overcome the high costs associated with deploying new fiber for DAA, MSOs are investing in Passive DWDM as a crucial building block to accelerate their network evolution plans. Cable MSOs, under pressure to match the 10G speeds offered by XGS-PON FTTH technology, have moved aggressively into DOCSIS 3.1 deployments, and are taking strategic steps to deploy DOCSIS 4.0 technology with symmetrical 10G capability. However, advanced DOCSIS networks require a transformation of the HFC infrastructure to a Distributed Access Architecture (DAA) featuring remote PHY (RPD) and remote MAC-PHY (RMD) nodes located closer to subscriber premises. Backhauling these RPD and RMD nodes means deploying much more fiber deeper into the HFC network and migrating the fiber portion of the network to a digital high-speed optical platform, driving the need for Passive DWDM in MSO networks. 

Figure 1. Migration to DAA in the Cable Access Network 

The Fiber Challenge 

From an optical distribution network perspective, the key migration step in DAA deployment is providing a fiber connection to each RPD/RMD, which requires support for longer reach to the RPD/RMD as well as higher capacity, as each remote node requires a new 10 gigabits per second (10G) connection. Moreover, the migration to Fiber Deep HFC architectures drives an order-of-magnitude increase in the number of remote nodes. For example, in July of 2023, Comcast announced that it had deployed over 100,000 Remote-PHY nodes as part of its implementation of DOCSIS 4.0. Cable MSOs must grapple with the demands of a deep optical technology refresh, the need to drive fiber deeper into the access network, and simultaneously cope with a massive increase in backhaul traffic. Although deploying dedicated fiber connections initially appears appealing, the long construction time and high cost associated with building new fiber infrastructure render it impractical. 

Figure 2. Dedicated Fiber Links for DAA Backhaul 

The Passive DWDM Solution

Passive Dense Wavelength Division Multiplexing (DWDM) technology emerges as a vital solution to economically expand the capacity of the existing fiber plant to allow it to carry much larger bandwidths required to support the number of Remote Nodes used in DAA. By multiplexing dozens of optical signals onto a single fiber, passive DWDM technology multiplies the capacity of fiber assets and extends network reach using cost-effective digital optical amplifiers. The passive DWDM approach maximizes the capacity of existing fiber infrastructure and reduces overall fiber deployment costs for MSOs transitioning to DAA architectures, while enhancing network scalability and performance. Re-using existing fiber for passive DWDM backhaul also avoids the need to wait for time-consuming fiber builds, allowing MSOs to accelerate service delivery to their subscribers.

Figure 3. Shared DWDM Links for DAA Backhaul

Advantages of Passive DWDM in the Cable Access Network

Passive DWDM equipment offers several benefits for operators planning a DAA migration while facing challenges imposed by a limited fiber plant: 


Optimized Fiber Utilization: Passive DWDM maximizes existing fiber infrastructure capacity by transmitting multiple signals over a single fiber, reducing the need for additional fiber deployment to support DAA evolution. 


Fiber Consolidation and Simplification: Cable MSOs can streamline network architecture by consolidating multiple fiber routes onto a single cable, reducing complexity and deployment expenses. 


Extended Reach and Network Expansion: When used in conjunction with EDFA amplifiers, operators can extend network coverage to new areas without significant fiber deployment costs. 


Vendor Agnostic Interoperability: Passive DWDM components adhere to industry standards, ensuring compatibility with various vendor products, simplifying integration into existing networks. 


Scalability and Futureproofing: DWDM systems allow incremental upgrades to support higher data rates, accommodating future bandwidth demands without requiring extensive network overhauls, thus optimizing investment returns, minimizing capital expenditures, and laying the groundwork for future HFC evolution or FTTH migration. 

Overall, passive DWDM technology provides a cost-effective and scalable solution for addressing fiber deployment challenges during the transition to DAA, enabling a smooth and efficient evolution of cable MSO networks. 

LambdaGain™ Solution Elements

High-Capacity ISP DWDM Mux/Demux: 


Our high-capacity passive DWDM Mux/Demux ISP modules accommodate up to 48, 100GHz spaced channels. With low insertion loss, LambdaGain mux/demux units are available in 1-RU and LGX form factors and offer standard LC connector interfaces, along with MPO and VSSF (Very Small Form Factor) options, delivering industry-leading port density. Standard LambdaGain mux/demux units support data rates up to 100Gbps per DWDM channel, with Extended-bandwidth options available for operators looking for compatibility with 400Gbps optics. 

Figure 4.  40CH LGX single fiber mux/demux using VSFF connectors for reduced headend footprint

Ruggedized OSP Passive DWDM Mux/Demux: 


To support migration to DWDM in the access plant, our solutions include a broad range of ruggedized DWDM mux/demux units that can be deployed in outside plant environments, such as manhole locations, poles, and other challenging environments. 

Figure 5. High Capacity remote DWDM Mux/Demux in weatherproof enclosure for installation in manholes, direct buried, or pole mount applications. 

DWDM SFP+ Pluggable Optics: 


LambdaGain fixed and tunable DWDM SFP+ optics have been rigorously tested and deployed with leading DAA networking equipment manufacturers. Our optics are compatible with major OEM spine/leaf DAA aggregation switches and RPDs. They feature low power consumption and support extended temperature ranges, available in commercial (0°C to +70°C), industrial (-40°C to +85°C), and extreme (-40°C to +95°C) operating temperatures for demanding applications. Stay tuned for future blogs where we’ll explore these options in greater detail. 

Figure 6. Fixed or Tunable DWDM SFP+ support commercial, industrial, and extreme operating temperatures  

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