Unveiling the Power of GPON in Modern FTTH Networks

FTTH (Fiber to the Home) is a fiber optic access technology that directly connects residential or corporate users, enabling a direct link from service providers to the end user. Meanwhile, GPON (Gigabit-capable Passive Optical Network), which provides data transmission via fiber optics, is usually the preferred choice in FTTH networks. This post mainly discusses the advantages of GPON in the FTTH access network and the components and architecture of GPON networks.

What is GPON？

GPON is a type of fiber-optic broadband network technology that allows for the delivery of high-speed internet, voice, and video services to homes and businesses. In GPON networks, data signals are transmitted over long distances using optical fibers, providing users with faster and more reliable connectivity compared to traditional copper-based networks. GPON operates on a passive optical network architecture, which means it utilizes passive optical components like splitters and combiners to distribute signals without the need for powered equipment along the transmission path.

Why Is GPON a Preferred Choice in FTTH Network?

Enhancing Home Network Connectivity

GPON technology supports downstream speeds of 2.5 Gbps and upstream speeds of 1.25 Gbps. This capability allows household members to engage in various online activities such as HD video streaming, online gaming, and video conferencing simultaneously. Furthermore, it supports multiple devices and users within a household to be online concurrently without compromising network performance, ensuring each family member can enjoy their online experiences without interruption.

Coverage Range Fits FTTH Deployments

GPON technology supports long-distance transmission, typically reaching up to 20 kilometers from the central office to the subscriber's premises. This extensive reach allows service providers to cover a wide geographic area with a single fiber optic network, minimizing the need for additional infrastructure investments. As a result, GPON is well-suited for various deployment scenarios, especially in Fiber to the x (FTTx) networks.

Cost-Effective Through Passive Architecture

GPON adopts a passive network architecture, which means the optical devices it employs do not require power supplies, thus reducing dependence on energy and active equipment. Meanwhile, the prices and failure rates of passive equipment are much lower than those of active devices, resulting in a corresponding reduction in overall operational costs. Furthermore, GPON networks utilize passive splitters to achieve a point-to-multipoint (P2MP) network architecture, significantly reducing deployment costs while ensuring signal quality. Therefore, GPON technology offers a highly cost-effective passive architecture in FTTH networks, allowing customers to maximize benefits with minimal investment costs.

Scalability and Reliability

The GPON network boasts high scalability, enabling service providers to effortlessly expand their networks to accommodate growing user bases. With the continuous evolution of PON networks, the optical network units (ONUs or ONTs) within users' homes can seamlessly transition to support higher-speed equipment in the future, such as units compatible with 10G-GPON, XGS-PON, or NG-PON2 standards. This facilitates increased bandwidth without the need to modify existing fiber infrastructure. This is to say, despite evolving bandwidth demands and internet technologies, existing FTTH infrastructure can reliably adapt and upgrade, ensuring the continuous delivery of efficient network services.

Components of GPON FTTH Access Network

In a GPON FTTH access network, there are three main components: optical line terminal (OLT), optical splitters, and optical network terminal (ONT).

Figure 1: Components of GPON FTTH Network

OLT (Optical Line Terminal)

The OLT functions as the endpoint for service providers in a passive optical network, typically situated in a data center or main equipment rooms Serving as the powerhouse for FTTH systems, the OLT transforms optical signals into electrical signals, presenting them to a core Ethernet switch. In doing so, it replaces multiple layer 2 switches at distribution points. The OLT's distributed signal connects to backbone cabling or horizontal cabling through optical splitters, establishing links with optical network terminals at individual work area outlets.

For more information, you can check: Exploring the OLT (Optical Line Terminal).

ONT/ONU (Optical Network Terminal/Unit)

Deployed at customer premises, the ONT/ONU connects to the OLT via optical fiber, with no active elements in the link. In the GPON network, the transceiver within the ONT/ONU establishes the physical connection between customer premises and the central office OLT. The ONT/ONU serves as the interface for end-users, facilitating the conversion of optical signals back into electrical signals for seamless connectivity to various devices such as computers, phones, and televisions in a Ffiber-the-home(FTTH) network.

Click on A Quick Guide to ONU (Optical Network Unit) to learn more.

Optical Splitter

What Is an Optical Splitter? The optical splitter divides the signal power, allowing a single fiber link entering the splitter to be split into multiple fibers. Multiple levels of fibers often correspond to various levels of splitters, facilitating the shared use of each fiber by numerous users. FS Passive optical splitters offer broad operating wavelength ranges, low insertion loss, uniformity, compact dimensions, high reliability, and support for network survivability and protection policies.

Architecture of GPON FTTH Access Networks

Employing a tree topology, GPON ensures maximum coverage with minimal network splits, effectively minimizing optical power requirements. The architecture of an FTTH (Fiber to the Home) access network can be delineated into five distinct areas: a core network area, a central office area, a feeder area, a distribution area and a user area/customer premises (see the picture below).

Figure 2: Architecture of GPON FTTH Network

Core Network

The core network integrates essential components such as ISP equipment, PSTN (public switched telephone network) - whether packet-switched or legacy circuit-switched - and cable TV provider equipment. This centralized hub forms the backbone of FTTH architecture.

Central Office

Serving as a pivotal location, the central office hosts the Optical Line Terminal (OLT) and Optical Distribution Frame (ODF), providing necessary powering. It may also house certain elements of the core network, consolidating key functionalities in one central hub.

Feeder Network

Extending from the ODF in the central office (CO) to distribution points, typically street cabinets known as Fiber Distribution Terminals (FDTs), the feeder network incorporates level-1 splitters. The feeder cable adopts a ring topology, enhancing reliability and providing Type B protection.

Distribution Network

The distribution cable links the level-1 splitter within the FDT to the level-2 splitter, often hosted in a pole-mounted box called a Fiber Access Terminal (FAT) at the neighborhood entrance. This level-2 splitter further refines signal distribution.

User Area

In the user area, drop cables establish connections from the level-2 splitter inside the FAT to subscriber premises. To facilitate maintenance, an aerial drop cable terminates at the subscriber's entrance via a Terminal Box (TB). Subsequently, an indoor drop cable links the TB to an Access Terminal Box (ATB) within the home. A patch cord then completes the connectivity, linking the Optical Network Terminal (ONT) to the ATB.

Consider the FS exemplary FTTH solution, which includes a range of specialized PON devices and components. The accompanying diagram illustrates a standard GPON network architecture. Positioned at the service provider’s central office, the Optical Line Terminal (OLT) acts as the pivotal control center for the PON network. It connects via a single fiber to one side of a 1x32 optical splitter. The other side of the splitter extends connectivity through 32 fibers to Optical Network Units (ONUs), delivering data, IPTV, voice, WiFi access, and additional services to 32 customer households.

Figure 3: FS FTTH Solution

Summary

Gigabit Passive Optical Network (GPON) stands out among other passive optical networks thanks to its immense benefits. A GPON-based FTTH network architecture is reliable, scalable, and secure. As a passive network, it lacks active components between the Central Office (CO) and the end users, which greatly reduces both the maintenance costs and the operational demands. GPON-based FTTH networks are a future-proof strategy for delivering broadband services. As a network solution provider, FS is dedicated to offering professional product support, technical assistance, and tailored solutions. For more details, please visit FS PON Networks.