How Fiber Internet Works: A Technical Guide (2026)

Fiber optic internet transmits data as pulses of light through thin glass or plastic strands, enabling speeds up to 10+ Gbps with latency under 15ms. Light travels through the fiber core via total internal reflection, allowing data to move at roughly 70% the speed of light. An ONT (Optical Network Terminal) at your home converts light signals to electrical data for your router. Fiber is immune to electromagnetic interference and signal degradation over distance.

The Physics of Fiber Optics

Fiber optic cables contain one or more hair-thin strands of glass or plastic called optical fibers. Each strand has a core (where light travels) surrounded by cladding (a layer with a different refractive index that reflects light back into the core). Data is transmitted by rapidly pulsing a laser or LED light source on and off -- these light pulses represent the 1s and 0s of digital data. The light bounces along the core through total internal reflection, traveling at approximately 200,000 km/s (about 70% of the speed of light in a vacuum).

Single-Mode vs Multi-Mode Fiber

Single-mode fiber uses a very thin core (8-10 microns) that allows only one mode of light to propagate, enabling transmission over very long distances (up to 100+ km) with minimal signal loss. This is what your ISP uses for the backbone network and the line running to your home. Multi-mode fiber has a larger core (50-62.5 microns) that allows multiple light modes, suitable for shorter distances (up to 2 km). Multi-mode is used in data centers and some building internal networks.

From Fiber to Your Home: FTTH Architecture

Fiber to the Home (FTTH) brings a fiber optic cable all the way to your residence. The network architecture typically uses GPON (Gigabit Passive Optical Network) or XGS-PON technology. From the provider's central office, fiber runs to neighborhood distribution points (typically serving 32-128 homes), then individual fibers branch to each home. A small box called an ONT (Optical Network Terminal) is mounted on the outside or inside of your home, converting light signals to electrical ethernet signals that your router can use.

Why Fiber Is Superior to Other Technologies

Fiber's physical properties give it fundamental advantages. Light signals don't degrade significantly over distance (unlike DSL's copper signals, which weaken rapidly). Fiber is immune to electromagnetic interference from power lines, appliances, and weather (unlike cable's coax). The bandwidth capacity of a single fiber strand is essentially unlimited with current technology -- providers can increase speeds by upgrading equipment at each end without replacing the fiber itself. This means the fiber installed at your home today can support speeds that won't be commercially available for decades.

Fiber Installation Process

Fiber installation involves running a cable from the nearest distribution point to your home. This may involve underground burial, aerial attachment to utility poles, or conduit routing depending on your neighborhood's infrastructure. A technician installs the ONT where the fiber enters your home, typically taking 2-4 hours. The ONT provides an ethernet port that connects to your router. Some providers include a router/gateway with the ONT. Once connected, fiber requires minimal maintenance and provides the most reliable residential internet technology available.

The Advantages of Light-Based Data Transmission

Fiber optic technology leverages several physical properties of light that give it fundamental advantages over electrical transmission through copper cables. Light doesn't generate electromagnetic interference and isn't susceptible to it -- your fiber connection can run alongside power lines, through areas of heavy electromagnetic activity, and past appliance-heavy kitchens without any signal degradation. This immunity to interference is why fiber delivers such consistent, reliable performance.

Signal attenuation (weakening over distance) is dramatically lower in fiber compared to copper. Copper DSL signals degrade significantly after just 1-2 miles, while fiber can transmit data over 60+ miles without amplification. This means a fiber customer 10 miles from the provider's equipment gets the same performance as one 100 feet away -- a critical advantage for suburban and semi-rural deployments where customers may be far from the central office.

The bandwidth capacity of fiber is virtually unlimited with current technology. Researchers have demonstrated data transmission speeds exceeding 1 petabit per second (1 million Gbps) through a single fiber strand in laboratory conditions. Even commercial wavelength-division multiplexing (WDM) technology supports dozens of independent data channels on a single fiber, each carrying 100+ Gbps. This extraordinary capacity headroom means the fiber installed at your home today can support speeds that won't be commercially necessary for generations.

Types of Fiber Deployment

FTTH (Fiber to the Home) brings fiber all the way to your residence, offering the best performance. This is what AT&T Fiber, Verizon Fios, Google Fiber, and Frontier Fiber provide. FTTB (Fiber to the Building) brings fiber to a building's utility room, with the final connection to individual units made over existing copper or coax wiring inside the building. FTTN (Fiber to the Node) brings fiber to a neighborhood cabinet, with the final mile delivered over copper DSL. FTTH provides the best speeds; FTTB is acceptable; FTTN is essentially upgraded DSL with limited improvement.

When signing up for fiber internet, verify that your plan is FTTH -- true fiber to your home. Some providers market FTTN connections as "fiber" when the actual fiber only reaches a neighborhood cabinet, with the final connection running over slower copper. FTTH plans will typically advertise symmetric speeds (matching upload and download), which is a reliable indicator of a genuine fiber-to-home connection.

The Future of Fiber Technology

Fiber optic technology continues advancing, with each generation delivering faster speeds through the same physical cables already installed. GPON (Gigabit Passive Optical Network), which currently serves most residential fiber customers, supports up to 2.5 Gbps downstream. XGS-PON doubles this to 10 Gbps symmetric. The newest standard, 50G-PON, will support 50 Gbps on a single wavelength. These upgrades require only equipment changes at the provider's central office and the customer's ONT -- the fiber cable itself remains unchanged.

This upgrade path is uniquely valuable among internet technologies. Copper-based services (cable, DSL) face hard physical limits on bandwidth that can only be overcome by replacing the cable itself. Wireless technologies (5G, satellite) are limited by available radio spectrum. Fiber's bandwidth capacity is effectively unlimited with foreseeable technology, making it the most future-proof infrastructure investment possible. A home with fiber access today will have access to speeds we can barely imagine for decades to come.