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By goodvin | 13 December 2023 | 0 Comments

Introduction to FTTN Networks

Introduction to FTTN Networks

Fiber to the node (FTTN) is an important fiber optic network architecture for providing high-speed broadband access. FTTN combines fiber optic cabling and existing copper infrastructure to deliver improved performance in a cost-effective manner. This article provides an overview of FTTN networks, their deployment, technologies, and pros and cons relative to other fiber access methods.
Overview of FTTN Architecture
In an FTTN network, fiber optic cables run from the service provider's central office to nodes located near end user premises, typically serving up to several hundred customers. The remaining connection from the fiber node to the customer premises uses the existing copper lines such as telephone wires or coaxial cables.
Different variants of FTTN include:
.Fiber to the curb (FTTC) - Fiber nodes are located in street cabinets nearer to user premises.
.Fiber to the neighborhood (FTTN) - Nodes are positioned to serve a neighborhood.
.Fiber to the building (FTTB) - Multi-tenant buildings have fiber nodes installed inside or near the building.
At the fiber node, the optical signals coming from the central office are converted into electrical signals for transmission over copper wires to the user premises. The fiber node houses active electronics like DSLAMs to enable this fiber-copper transmission.
FTTN Technologies
There are several technologies used in FTTN networks that optimize the fiber-copper combination:
.VDSL - Very high bit rate DSL runs over copper lines from fiber nodes. Supports speeds of 100Mbps or more using vectoring and other innovations.
.G.fast - DSL technology that achieves gigabit speeds over copper lengths up to 250m by utilizing higher frequencies up to 212MHz.
.DOCSIS 3.1 - Cable networks leverage the DOCSIS 3.1 standard to offer gigabit speeds over existing coaxial connections to the fiber node.
.Hybrid fiber-coaxial (HFC) - Combines fiber optic and DOCSIS-based coaxial cable, which simultaneously delivers broadband, video and voice services.
FTTN employs these transmission technologies to deliver fiber broadband speeds without a full fiber installation to user premises.
Benefits of FTTN
FTTN offers several advantages over fully fiber or legacy copper networks:
Cost-efficiency - Leverages existing copper while requiring less new fiber deployment compared to FTTH/FTTP networks.
Higher speeds - Enables gigabit broadband speeds by overcoming distance limitations of copper infrastructure.
Scalability - Additional nodes can be added deeper in the network over time, and eventually evolve to full FTTH.
Quick deployment - FTTN can be rolled out rapidly by upgrading existing equipment at central offices and customer sites.
Reliability - Provides better reliability and uptime compared to old copper networks.
Limitations of FTTN
The main limitations or disadvantages of FTTN include:
.Distance/Speed constraints - Line speeds still depend on copper line length from node to user site. Longer lines cannot support gigabit speeds.
.Shared bandwidth - Available capacity is shared among users connected to the same fiber node.
.No fiber redundancy - Outages at the fiber node impact all connected users. Fully fiber networks have redundant paths.
.Copper maintenance - Maintenance and troubleshooting of aging copper cables persists in FTTN.
.Not future-proof - While FTTN offers short-term speed boost, only full fiber networks can support long-term gigabit demands.
FTTN vs FTTH Architectures
FTTN provides an interim upgrade path from copper to fiber, balancing costs and benefits:
.FTTN offers faster deployment and lower upfront costs compared to FTTH which requires extensive new fiber builds.
.However, FTTH provides higher reliability, future-proof capacity and avoids copper infrastructure maintenance.
.FTTN struggles to deliver symmetrical gigabit services available with FTTH.
.FTTN can complement 5G mobile networks, while FTTH backs high-density 5G deployment.
.Overall, FTTN provides a step-wise migration path towards full FTTH/FTTP down the road.
FTTN retains higher speed copper-based links while bringing fiber closer to the user. This unique combo allows FTTN to deliver next-gen broadband economically by optimizing existing infrastructure. However, FTTN may gradually give way to end-to-end fiber deployments to meet rising long-term speed, reliability and symmetry demands. FTTN forms an interim waypoint in the larger migration towards an all-fiber future.

Q1: What are typical distances for FTTN deployment?
A1: Typical FTTN deployment distances are:
.Fiber cable from central office to node: Up to 20 km
.Copper cable from node to user: 300m for VDSL2 supporting 100Mbps, or 100m for G.fast gigabit speeds
.FTTN allows the fiber backhaul to cover longer distances, bringing nodes closer to users.
Q2: Does FTTN support voice services?
A2: Yes, FTTN supports traditional telephone and Voice over IP (VoIP) services. Analog telephone signals are digitized at the fiber nodes and transmitted over the fiber backhaul. IP-based VoIP services are also carried natively on the IP/Ethernet network under FTTN.
Q3: What frequency bands are used by G.fast?
A3: G.fast uses a wide band of frequencies up to 212MHz, much higher than VDSL2 or ADSL. Specifically, it uses:
.2.2 MHz to 106 MHz for downstream
.5.2 MHz to 212 MHz for upstream
This wide frequency range enables gigabit speeds over short copper lengths.
Q4: Can FTTN evolve to FTTH easily?
A4: Yes, FTTN networks can be upgraded to FTTH by extending fiber from the nodes directly to user premises. This eliminates the copper portion completely. Existing fiber links, central office equipment and power infrastructure can be retained. Overall, FTTN provides an incremental path to full FTTH.
Q5: How does FTTN improve reliability compared to ADSL networks?
A5: FTTN offers better reliability than legacy ADSL over long copper distances due to:
.Shorter copper cable from node to premises
.High-quality fiber backhaul with self-healing capability
.Redundant power supplies at central office and remote nodes
.Improved monitoring and diagnostics capabilities
Keywords: FTTN, FTTC, VDSL, G.fast, DSL, fiber to the node, broadband networks, last mile access, gigabit Internet

Recommended Reading: Introduction to FTTx networks

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