GPON Explained: How Modern Fiber Internet Works and FTTH vs Other Technologies

GPON is one of the most widespread fiber optic internet technologies, delivering high speeds, stable connections, and the ability to connect many users without compromising quality. In fact, GPON is the backbone of most "fiber to the apartment" (FTTH) connections offered by today's internet providers.

Unlike older technologies such as ADSL or cable internet, GPON uses a passive optical network: data travels as light through a thin fiber, and distribution among subscribers happens without active amplifiers. This makes the network more reliable, energy-efficient, and resistant to interference.

GPON enables a single provider port to serve dozens of apartments while maintaining high speed, low latency, and dependable performance-even under heavy load. To understand why this technology outperforms others and how fiber reaches your home, let's break down how GPON networks work, their components, and their pros and cons.

What Is GPON and Why Is This Technology so Popular?

GPON (Gigabit Passive Optical Network) is a passive gigabit optical network technology that delivers internet to apartments and private homes via fiber optic cable. The key difference between GPON and other access types is the absence of active equipment between the provider and the subscriber. All core network elements are passive: they don't require power, don't overheat, don't break down, and need almost no maintenance.

With GPON, a single fiber channel from the provider's central hub is split into dozens of connections using passive splitters. This setup lets providers serve many subscribers simultaneously, maintain high speeds, and lower infrastructure costs.

Compared to ADSL, Ethernet to the home, or cable networks, GPON offers several advantages:

• High speed: up to 2.5 Gbps downstream and 1.25 Gbps upstream
• Minimal latency: critical for gaming, cloud services, and streaming
• High stability: fiber is immune to electromagnetic interference
• No active intermediary equipment: fewer points of failure
• Long-lasting cable infrastructure (fiber can last for decades)

GPON's popularity stems from its scalability, readiness for future standards (like XG-PON and XGS-PON), and the ability to quickly deploy even in old buildings and densely populated areas. That's why most FTTH connections today use GPON-it offers the optimal balance of speed, reliability, and cost.

How GPON Works: A Simple Explanation

GPON operates by transmitting data through a single fiber optic cable, which is then split among multiple subscribers via passive splitters. This architecture is called PON (Passive Optical Network) because there's no powered equipment between provider and user. This makes the network reliable and inexpensive to maintain: nothing to overheat, freeze, or fail.

GPON's setup is a "point-to-multipoint" system:

• At the provider's side is the OLT (Optical Line Terminal), the central device managing the network
• Between buildings are optical splitters dividing the signal 1:16, 1:32, or 1:64
• At the subscriber's location is an ONT/ONU-a small optical terminal that converts the light signal into standard Ethernet

Data transmission is divided into two directions:

• Downstream: from provider to subscribers, sent continuously and broadcast
• Upstream: from subscribers to provider, distributed in time slots (TDMA) to avoid collisions

The OLT sends one powerful signal evenly distributed among all connected users. For uploads, ONTs are assigned "time slots" in which they can transmit data, ensuring no packet collisions.

For a deeper dive into the physical principles of light transmission, reflection, and modulation, see the article How Fiber Optic Internet Works: Cable Structure, Speed, and Light-Based Data Transmission.

This architecture allows GPON to deliver high speeds, robust network resources, and minimal signal loss over long distances-making it ideal for mass-market home internet.

What Makes Up a GPON Network: OLT, Splitters, ONU/ONT

A GPON network is composed of three key elements: provider equipment, passive optical infrastructure, and the subscriber terminal. Each piece plays a role, but the entire system is transparent for the end user-everything happens automatically, with no active devices between provider and apartment.

OLT - Optical Line Terminal

This is the "brain" of the GPON network, located at the provider's central site. The OLT generates the optical signal, allocates bandwidth among subscribers, assigns time slots for data transmission, and manages the network topology. A single OLT port can serve dozens or even hundreds of connections, depending on the split ratio.

Optical Splitters

These are passive light dividers that split a single incoming optical signal into 8, 16, 32, 64, or more outputs. Splitters require no power, contain no electronics, and can function for years without maintenance. Placement depends on network layout:

• In building entryways
• On each floor in a distribution box
• In outdoor cabinets
• In manholes or on poles

Splitters can be cascaded-for example, a 1:4 splitter in a manhole, then 1:8 in the building-allowing flexible coverage across entire neighborhoods.

ONU / ONT - Subscriber Terminals

The ONT (Optical Network Terminal) or ONU (Optical Network Unit) is the device located in the user's home. It receives the light signal, converts it to Ethernet, and manages subscriber authentication-in essence, it's an "optical modem." Sometimes the ONT is combined with a Wi-Fi router, known as a GPON router.

ONT functions include:

• Decoding the downstream optical stream
• Sending data upstream strictly in its assigned time slot
• Providing security via authentication
• Monitoring connection quality

The provider's responsibility typically ends at the optical connector or ONT, though many ISPs supply combined ONT routers and support this part of the network as well.

Together, the OLT, splitters, and ONT create a reliable, scalable infrastructure for stable gigabit internet with minimal delays.

GPON vs. PON: What's the Difference and How Is the Technology Evolving?

GPON is one of several standards under the PON (Passive Optical Network) umbrella. In essence, PON is a general concept, while GPON is a specific implementation with defined speeds, protocols, and architecture. Unlike copper or active optical networks, PONs have no amplifiers or switches along the way-everything is achieved through passive components.

Main types of passive optical networks include:

• EPON: a Japanese standard based on Ethernet
• GPON: an international ITU-T standard focused on high efficiency
• XG-PON: next-generation GPON with up to 10 Gbps downstream
• XGS-PON: a symmetric 10 Gbps/10 Gbps version for enterprise networks
• NG-PON2: a multi-wavelength standard supporting up to 40 Gbps

GPON's main distinction is its use of the GEM (GPON Encapsulation Method), which efficiently packages data from different protocols and minimizes overhead. GPON supports up to 2.5 Gbps downstream and 1.25 Gbps upstream, making it ideal for mass-market FTTH connections.

EPON works more like classic Ethernet but is less spectrum-efficient under heavy load-one reason why most European and Russian providers prefer GPON.

XG-PON and XGS-PON represent the future of the technology. They are backward-compatible: to upgrade to 10 Gbps, operators only need to replace OLTs and ONTs; splitters and fiber lines remain unchanged.

In summary, GPON is the most common and versatile version of PON, with ongoing development focused on increasing speed and symmetry while maintaining low latency, passive infrastructure, and high network lifespan.

FTTH: What It Is and How Fiber Reaches Your Apartment

FTTH (Fiber To The Home) is a connection scheme in which fiber optic cable runs directly into the user's apartment or home. This is the most modern and reliable way to access the internet, unlocking the full potential of technologies like GPON, XGS-PON, or future NG-PON2 standards.

The key feature of FTTH is the absence of intermediate copper segments. In older setups like FTTB (fiber to the building) or FTTN (fiber to the node), the last segment from the cabinet to the apartment used twisted pair or coaxial cable. FTTH eliminates this "weak link" by bringing fiber directly to the subscriber.

A typical FTTH installation looks like this:

1. Provider's fiber runs along the street to a distribution cabinet
2. From there, fiber is pulled into the building to an optical distribution box
3. Technicians lay a thin indoor fiber cable to the apartment
4. An ONT is installed in the apartment, converting the signal to Ethernet
5. The user connects a Wi-Fi router to the ONT

Benefits of this setup include:

• Minimal signal loss along the entire route
• No interference typical of copper cables
• Consistently high speeds, regardless of distance
• No contact burn-out, oxidation, or electromagnetic disturbances
• Network is ready for future upgrades without additional cabling

Unlike FTTB, where several apartments share a copper switch, FTTH provides each user with a dedicated fiber line-enabling speeds of 1-10 Gbps and beyond.

Thanks to its scalability and reliability, FTTH has become the gold standard in new residential developments and is being actively rolled out in older buildings. Combined with GPON, this architecture delivers the cleanest, fastest internet access available.

GPON Speed: Real-World Throughput and Limitations

GPON is among the fastest mainstream internet access technologies, but real-world speeds depend on network architecture and how many subscribers share a single OLT port. By standard, GPON supports 2.488 Gbps downstream (to users) and 1.244 Gbps upstream (from users). This is not per user, but the total bandwidth divided among all connections via splitters.

Typical OLT split ratios are 1:32 or 1:64, meaning up to 32 or 64 subscribers share a single stream. However, because actual network load is distributed (not everyone streams 4K video at once), users typically enjoy highly stable speeds-usually 300-1000 Mbps, depending on their plan.

GPON speed limitations depend on:

• Provider's chosen split ratio
• Optical line quality and route length
• Signal loss and noise on splitters
• OLT power and ONT sensitivity
• State of the home network (router, Wi-Fi)

Despite bandwidth sharing, GPON remains more stable than any copper technology. Fiber is virtually immune to interference, doesn't lose speed over distance, and offers low latency (typically 2-4 ms), which is crucial for gaming and video calls.

The only real GPON limitation is the standard's throughput. For plans above 1 Gbps, providers move to XG-PON or XGS-PON, delivering 10 Gbps while remaining fully compatible with existing infrastructure.

So, GPON delivers high, real-world speeds for most home users, and its limitations are easily managed when operators use appropriate split ratios and quality optical equipment.

GPON Pros and Cons

GPON has become one of the most sought-after wired internet technologies thanks to its high speed, stability, and affordable scalability. Like any technology, though, it has strengths and weaknesses to consider when choosing a provider or building a network.

Advantages of GPON

1. High Speed
   Even basic GPON provides gigabit speeds-more than enough for most home needs. The technology doesn't lose speed over distance, a key advantage over cable and DSL networks.
2. Low Latency
   Passive architecture and no active nodes between provider and subscriber ensure low ping (2-4 ms). Essential for gaming, video calls, and VPN work.
3. Reliability
   No active elements to break or overheat. Splitters are passive devices that can operate for decades.
4. Energy Efficiency
   Equipment uses minimal power; outdoor infrastructure needs no electricity.
5. Easy Scalability
   One OLT port can serve dozens of subscribers-providers simply add splitters and ONTs, no need to replace the main line.

Disadvantages of GPON

1. Shared Bandwidth
   The main drawback: speed is shared among all branch subscribers. If the split ratio is too high (e.g., 1:128), speeds may drop during peak hours.
2. Installation Quality Demands
   Poor fiber splicing or cheap splitters can seriously degrade signal quality.
3. Challenging Installation in Old Buildings
   In some buildings, it's difficult to lay fiber quickly or neatly.

Overall, GPON's advantages far outweigh the drawbacks, making it the optimal solution for gigabit home internet.

How GPON Is Installed in an Apartment: Steps and Requirements

Connecting GPON in an apartment is straightforward for the user but requires technical precision from installers. The primary task: bring fiber to the premises and correctly set up the subscriber terminal (ONT) to convert the light signal into standard Ethernet.

The installation process:

1. Check for GPON availability in the building
   The provider verifies whether the fiber trunk and free OLT ports are present. In new or recently upgraded buildings, fiber is usually already available.
2. Laying fiber to and inside the apartment
   Thin in-building fiber is routed:
   • along cable trays,
   • around the wall perimeter,
   • through hidden channels if available,
   • along the baseboard.
   Fiber is flexible but needs careful handling-sharp bends are not allowed.
3. Connecting to the splitter
   The optical box with the splitter is located in the building. The installer connects your cable to one of its ports.
4. Installing the ONT/ONU
   The terminal is placed in the apartment near the cable entry point. Some ONTs are full-featured Wi-Fi routers, while others are simple terminals requiring a separate router.
   • Receives and decodes the optical signal
   • Sends data only in its assigned time slots
   • Verifies subscriber authorization
   • Provides Ethernet for your router or PC
5. Equipment setup
   The provider configures parameters on the OLT (ONU number, profile, VLAN), after which the ONT is linked to the network. Most settings are automatic-users don't need to configure anything.
6. Signal level check
   Optical loss is measured (dBm). Acceptable levels are usually from −8 to −28 dBm-if the signal is weak, connectors may be replaced or the line adjusted.

After these steps, your internet is ready to use. All that's left is to set up your Wi-Fi router, if it's not integrated into the ONT.

Conclusion

GPON has become the primary standard for home fiber optic internet thanks to its combination of high speed, stability, and easy scalability. The passive network architecture ensures reliability and energy efficiency, while running fiber directly to the apartment minimizes interference and unlocks gigabit connections' full potential.

The technology is future-proof: as it evolves (with XG-PON, XGS-PON, and beyond), speeds will increase to tens of gigabits without the need to replace the cable infrastructure. GPON offers operators and users the ideal mix of speed, cost, and longevity, making it the best choice for modern FTTH networks.