FTTB (Fiber to the Building)
An access architecture where optical fiber terminates at a multi-tenant building's basement or telecom room, with internal cabling distributing to each unit.
FTTB stands for Fiber to the Building. It refers to a fiber-optic access architecture in which optical fiber runs from the central office to a single point inside a multi-dwelling unit (MDU) — typically the basement, telecom room, or risers — and internal cabling (usually existing copper, coax, or new fiber) carries service to each unit.
FTTB is the dominant deployment model for high-density urban MDU buildings in 2026 because it solves a specific economic problem: pulling individual fiber drops to every unit in a high-rise is operationally and contractually difficult. FTTB lets operators serve a 200-unit building from a single building-level demarcation, reusing existing in-building riser plant for the last segment.
When the in-building distribution is also fiber, FTTB approaches FTTH performance and is sometimes called "FTTH-MDU." When the in-building distribution is copper or coax (typical in older buildings), bandwidth and reliability are limited by the copper plant.
In MapItRight, FTTB deployments are modeled as a single fiber drop to the building demarcation point, with optional internal-distribution modeling for buildings where the operator owns or manages the in-building plant.
FTTB uses the same optical standards as FTTH for the external fiber segment — ITU-T G.984 (GPON) or G.9807.1 (XGS-PON) — with the optical link budget and 20 km distance limit applying equally. The in-building copper distribution in FTTB-copper deployments typically uses VDSL2 (ITU-T G.993.2) over existing category 3 or category 5 riser cabling, delivering 50–300 Mbps per unit depending on floor count and riser quality. FTTB-fiber variants (sometimes called FTTH-MDU) use in-building fiber risers, typically 2-fiber per unit, to deliver FTTH-class performance at each unit demarcation.
FTTB vs FTTH: FTTB delivers fiber to a single building demarcation — typically one drop cable serving the entire building — while FTTH runs individual fiber strands to every premises. For a 100-unit high-rise, FTTH requires 100 separate drops from the nearest NAP, while FTTB requires one. FTTB reduces drop material cost by 80–90% and eliminates the need for conduit distribution inside building walls, but the in-building copper segment limits per-unit bandwidth and adds copper maintenance overhead not present in full FTTH.
Accurate FTTB records matter for fault localization, BEAD classification, and MDU service-level management. BEAD treats FTTB-copper differently from FTTB-fiber: only FTTB deployments capable of 100/100 Mbps symmetrically per unit qualify as "served" under BEAD rules, and in-building copper often fails this test. GIS records that capture the in-building distribution type — copper vs fiber, riser length, number of units served — are necessary for accurate compliance reporting and proactive upgrade planning.
FTTB is most common in urban high-density markets where buildings have 20+ units, making individual FTTH drops economically or physically impractical. A typical FTTB deployment serves a 50–300 unit building from a single building-level ONT or active Ethernet switch. MDU-focused operators like urban ISPs and housing authority networks often build 80–95% FTTB by building count while achieving 60–80% of subscriber count, since urban MDUs concentrate population. The decision between FTTB-copper and FTTB-fiber depends primarily on riser access rights negotiated with building owners.