What Is a Fiber Distribution Hub (FDH)?
An FDH connects feeder fiber to distribution cables in an FTTx network, housing splice trays and splitters. See how it works and placement.
A Fiber Distribution Hub (FDH) is an outside plant enclosure that connects feeder fiber cables coming from a central office or hub site to the distribution cables that branch out toward homes and businesses. It houses splice trays, optical splitters, or both, marking the transition point between a network's feeder and distribution segments.
What an FDH Does in a Fiber Network
In a passive optical network (PON) architecture, feeder fiber runs from the central office or a regional fiber hub to the FDH. Inside the enclosure, technicians splice or terminate that feeder cable, then either splice through to distribution fiber or route it through optical splitters that divide a single feeder strand into multiple distribution legs. The FDH consolidates cross-connects in one accessible, protected location instead of leaving splices scattered along the route. That makes it easier to test, trace, and repair the network without digging up or climbing to every splice point individually.
Where FDHs Are Installed
FDHs come in a few physical forms: pole-mounted or ground-mounted cabinets for aerial builds, and below-grade vaults or pedestal enclosures for underground builds. Sizing depends on the number of feeder and distribution ports a network segment needs, which is set by subscriber density in that service area. Placement follows the same route-planning process as the rest of the outside plant build, so FDH locations are chosen early in network design, not added after construction starts.
FDH vs. Terminal or NAP
An FDH is not the same as the smaller enclosure at the curb or on a pole near a customer's home, usually called a terminal or network access point (NAP). The FDH sits upstream, aggregating and splitting fiber for an entire neighborhood or service area, while a terminal is the last enclosure before a drop cable reaches an individual premises. Understanding this distinction matters for troubleshooting: a fault traced to the FDH affects many subscribers, while a terminal-level fault usually affects one.
Fiber Distribution Hub (FDH), answered
What Is a Fiber Distribution Hub (FDH)?
A Fiber Distribution Hub (FDH) is an outside plant enclosure that connects feeder fiber cables coming from a central office or hub site to the distribution cables that branch out toward homes and businesses. It houses splice trays, optical splitters, or both, marking the transition point between a network's feeder and distribution segments.
How many customers does one FDH serve?
It varies by design, but a single FDH typically serves anywhere from a few hundred to over a thousand homes passed, depending on splitter ratios and the service area's subscriber density.
Is an FDH the same as a splice closure?
No. A splice closure is a sealed enclosure protecting a single splice point, while an FDH is a larger cabinet or vault that houses multiple splice trays and splitters and functions as a network-wide cross-connect point.
Do FDHs need power?
Standard passive FDHs don't need power since they only house passive splitters and splice trays. Power is only required if the site also includes active electronics, which is uncommon for typical PON deployments.