FTTH Tutorial: Complete Guide to FTTH Network Architecture, Diagrams, Configuration and AON vs PON vs EPON Vs GPON

Fiber to the Home (FTTH) is a key technology in delivering high-speed internet directly to homes and businesses. This tutorial explores the essential aspects of FTTH, including network architecture, configuration and the various technologies involved, such as AON, PON, EPON, and GPON.

Earlier telecommunication networks were using optic fibre cables for connectivity between exchanges across sea. This has been replaced with all fibre network. This concept provides connectivity between user premises and the service provider using fibre optic. It has become more popular because of higher bandwidth and cheap cost. Moreover it is reliable and secure way of communication compare to wireless networks.

Fibre optic networks have been evolved very quickly and service providers are deploying different fibre configurations based on different applications. It is designed as FTTx. Here 'x' stands for final terminating point on the user side. 'x' can be Home or Premise or Building, Curb or Node. Based on this there are different terminologies of fibre optic deployment configurations. They are FTTH (Fibre to the Home), FTTP (Fibre to the Premise), FTTB(Fibre to the Building) FTTN(Fibre to the Node) and FTTC (Fibre to the Curb).

FTTH is a type of fiber-optic communication delivery in which the optical fiber runs from a central point directly to individual buildings, such as residences or businesses. This contrasts with technologies where fiber runs to the curb or node and then uses coaxial cables or copper wires to complete the connection.

FTTH Configuration

As shown in the figure-1, the basic elements of the fibre optical network are OLT, ONU and ODN.
Optical Line Terminal (OLT): Located at the service provider's central office, the OLT is the endpoint hardware device in a passive optical network.
Optical Network Unit (ONU) / Optical Network Terminal (ONT): These devices are located at the user's premises and connect to the OLT via the optical fiber.
Optical Distribution Network (ODN): This network connects the OLT and the ONT, consisting of optical fibers, splitters, and connectors.

In this FTTH configuration modem is used at the user premises which converts optical signal to the electrical signal and vice versa. User computer is connected with the network using ethernet card.

FTTH Architecture diagram

A basic diagram includes the OLT at the central office connected via optical fibers to an ONU/ONT at the subscriber’s premises, often passing through a splitter. This shows the high-level layout of a typical FTTH network.

Active Optical Network (AON): In AON, each user has a dedicated fiber connection back to a switch in the provider's network. AON uses electrically powered equipment, such as Ethernet switches, to manage data.

Passive Optical Network (PON): PON uses unpowered splitters to divide a single optical fiber into multiple signals to serve multiple premises. This reduces the number of fibers needed but shares bandwidth among users.

The major deployment consideration for telecom service provider is to decide on FTTH architecture. There are two categories of architectures. They are active optical network(AON) and passive optical network(PON). These AON and PON have been explained below.

Configuring an FTTH network involves several key steps, focusing on both hardware setup and network management.

OLT Configuration
Defining Services: OLTs are configured to define the services (e.g., internet, voice, video) that will be delivered to the ONUs/ONTs.
Bandwidth Management: Quality of Service (QoS) settings ensure that bandwidth is allocated efficiently, prioritizing traffic as needed.
Security: Implementing encryption and other security measures to protect the data transmitted over the network.
ONU/ONT Configuration
Service Provisioning: This involves setting up the ONU/ONT to receive the defined services from the OLT.
Firmware Updates: Keeping the ONU/ONT updated with the latest firmware ensures it operates efficiently and securely.
Splitter Configuration
Splitter Placement: Determining the optimal location for splitters is crucial for minimizing signal loss and ensuring a robust connection.
Signal Testing: Testing the signal strength at various points in the network to ensure that it meets the required standards.

AON vs PON : Active vs. passive Optical networks

AON is a point to point FTTH architecture. This type uses active devices and connects OLT (Optical Line Terminal) placed at central office with ONT (Optical Network Terminal) placed at user premises using dedicated cable. Distance can be about 80 Km and the fibre cable provides full bi-directional communication. Figure-2 depicts typical active star ethernet (ASE) architecture which is a point to point architecture. This ASE architecture reduces cost due to sharing of the fibre cable.

PON is a point to multipoint FTTH architecture. This configuration is used for various applications. It includes voice, video, data etc. This configuration uses optical splitter to connect OLT located at service provider side with multiple ONUs located at user premises. Optical splitters are available in different configurations viz. 1:4, 1:8, 1:16, 1:32, 1:64 etc. As the name suggests this architecture uses all the passive components between OLT and ONUs. No electronic or electrical active components are used. There are two benefits to this type of architecture; easy maintanance and lower cost. Typical distance between OLT and ONU is about 35Km.

As shown in the figure-3, transmission from user premises to service provider is referred as uplink and from service provider to user premises is referred as downlink. In the uplink TDMA is used and in the downlink TDM is used. TDMA stands for Time Division Multiple Access and TDM stands for Time Division Multiplexing.

EPON (Ethernet PON) and GPON (Gigabit PON) are two main types of PON technologies, each with its unique characteristics.

EPON (Ethernet Passive Optical Network)

Technology: EPON is based on the Ethernet standard (IEEE 802.3) and delivers data in Ethernet frames.
Speed: Typically supports speeds of up to 1 Gbps.
Use Case: Widely used in Asia, particularly for delivering triple-play services (internet, TV, and voice) over a single fiber.

GPON (Gigabit Passive Optical Network)

Technology: GPON, defined by ITU-T G.984, delivers data using the Generic Framing Procedure (GFP) and supports multiple services including voice, video, and high-speed data.
Speed: Supports up to 2.5 Gbps downstream and 1.25 Gbps upstream.
Use Case: Popular in North America and Europe for its high data rates and ability to handle a mix of services efficiently.

There are different standards which are evolving under PON based on ethernet technology advancement. They are EPON(Ethernet PON) and GPON(Gigabit Ethernet PON).

Comparison between PON vs EPON vs GPON

Summary

Understanding the intricacies of FTTH, including network architecture, configuration, and the differences between AON, PON, EPON, and GPON, is crucial for anyone involved in designing or managing fiber-optic networks. Each technology offers its own set of advantages and challenges, and the choice between them depends on specific network requirements, cost considerations and regional preferences. This guide provides a foundation for further exploration into the world of FTTH, ensuring that you are equipped with the knowledge to make informed decisions about your network infrastructure.

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