FttbEdit

Fiber to the building (FTTB) is a form of broadband architecture in which a fiber backbone reaches a central point within a building—such as a basement, a dedicated equipment room, or a street cabinet serving the structure—and the final, internal leg to individual units runs over existing copper or coaxial cabling, or over shared Ethernet inside the building. The fiber portion carries the bulk of the access link’s capacity, while the inside-the-building wiring delivers services to residents or occupants. This approach is commonly used in dense urban environments and in many multi-dwelling units (MDUs) because it blends high capacity with lower up-front cost and faster deployment relative to running fiber all the way to every dwelling.

FTTB distinguishes itself from full fiber to the home by ending the optical link at a common termination point in the building rather than at each unit’s doorstep. From the building’s termination point, service is distributed using a combination of technologies, including copper-based links such as VDSL or G.fast, coaxial cables, or internal Ethernet networks. The fiber portion is typically connected to a small number of service termination devices—such as an Optical Line Terminal (OLT) in the service provider’s network and an Optical Network Terminal (ONT) at or near the building—and then shared among tenants. In many installations, the building’s shared equipment is managed by the building owner, a property manager, or a service provider, with the fiber leg providing the high-capacity backbone. See also Optical line terminal and Optical network terminal.

Architecture and technology

Core concept

In FTTB, the fiber runs to a central node in the building, often called a distribution point or central termination area. From there, the last mile to each unit uses existing building wiring or a shared internal network. This arrangement reduces the number of individual fiber drops and speeds up initial deployment in dense housing. For users, this often translates into high downstream capacity and strong performance for streamed video, cloud services, and online productivity tools. See fiber optic for background on the transmission medium and its advantages.

Building-side topology

The internal network can be copper-based (Cat 5e/6/6a or similar) or coaxial, depending on the building’s infrastructure and the chosen technology. When copper is used, the distance from the central termination to the farthest unit and the copper grade determine achievable speeds and reliability. In some cases, Ethernet-based architectures are deployed inside the building to move data from the terminal point to units. See Ethernet for general context.

Service delivery options

GPON, a form of passive optical networking, is a common method for sharing fiber capacity among multiple tenants in FTTB deployments. In GPON-based FTTB, the fiber feeds a shared optical network terminal in the building and uses a single optical link to serve many units. See GPON for details.
Active Ethernet is another approach in FTTB deployments, where Ethernet frames are carried over fiber directly to a building’s termination device, with separate ports or switches distributing bandwidth to each unit. See Active Ethernet for more on this option.
The “last mile” inside the building may use VDSL or G.fast over copper or be routed over a private Ethernet switch, depending on vendor choices and building constraints. See VDSL and G.fast for related copper-based technologies.

Equipment and management

The main network devices in FTTB include the service provider’s OLT and the building’s terminal hardware, often including an ONT or a similar demarcation device at or near the unit entry. Network management, QoS, and service-level guarantees are implemented at the central point and extended through the building’s internal network. See Optical line terminal and Optical network terminal for these components.

Deployment considerations

Economics and deployment speed

FTTB is typically less expensive to deploy than full FTTH in high-density buildings because it avoids running fiber to each dwelling unit and leverages existing internal wiring. It can also speed up service availability in older structures where retrofitting fiber to every unit would be costly or disruptive. See Broadband for broader economic and policy contexts.

Ownership and competition

In many markets, the ownership of the central termination equipment and the internal distribution network can be handled by the building owner, a telecom operator, or a management company. The arrangement influences competition, pricing, and upgrade paths. See Building and Telecommunication policy discussions for related considerations.

Performance and upgrading

The performance of FTTB depends on the fiber segment’s capacity and the quality of the internal wiring. While typical fiber backbones can deliver multi-gigabit capabilities, the in-building copper or coax segments may cap attainable speeds. Upgrades often focus on upgrading the central fiber capacity (e.g., from GPON to higher-capacity PON variants or to a pure Ethernet-based approach) or replacing aging in-building copper with higher-grade cabling where feasible. See Gigabit-capable Passive Optical Network and Ethernet for reference points on performance.

Security and reliability

Because multiple tenants share the building’s termination point and, in some designs, portions of the internal network, appropriate segmentation, access controls, and QoS policies are important to maintain reliability and privacy. Proper design mitigates cross-tenant interference and ensures consistent service quality. See Network security and Quality of service for related topics.

Comparison with other architectures

FTTH (fiber to the home) reaches each dwelling with fiber to the unit, offering the highest potential symmetry and future-proofing but at a higher upfront cost in many circumstances. See Fiber to the home for contrast.
HFC (hybrid fiber-coaxial) uses fiber to a distribution hub and coax inside the building; this approach is common in certain urban deployments and offers different performance characteristics and regulatory considerations. See Hybrid fiber-coaxial.
Traditional copper-based access (e.g., DSL over copper) is generally slower and more distance-sensitive than fiber-based approaches, though it can be cheaper to deploy in some legacy situations. See Digital subscriber line for background.

History and context

FTTB emerged as a practical compromise in markets with dense housing where the cost of full FTTH would be prohibitive or time-consuming to deploy. It shares a lineage with GPON and other passive optical networking approaches developed to efficiently serve multiple units from a single fiber backbone, while also absorbing the realities of existing building infrastructure. See Broadband and Telecommunications standard for broader historical context.