FTTH Network Architecture for Residential: Open Access and Future-Proof Design

What is FTTH network architecture for residential networks?

It is the layered design that carries fiber from an exchange to every home. Read it from the core outward and it has four segments.

1. Core and aggregation. The OLT sits here, with the uplinks to the wider network.
2. Feeder and distribution. Fiber runs from the OLT to splitters in cabinets, or to a fiber hand-off frame in a point-to-point design.
3. Drop. Short cables run from the last splitter or frame to each building or home.
4. In-building and home. Riser fiber and the ONT finish the path inside an apartment block or house.

The big topology choice is PON against point-to-point. In a PON, one fiber is shared by many homes through passive splitters. In a point-to-point network, each home has its own fiber back to a central frame. BEREC’s report on next-generation access notes that the two behave very differently for wholesale: in a PON only the last segment, the dedicated fiber between the end user and the last splitter, can be physically unbundled. That one fact shapes everything in the next section. On greenfield estates, see FTTH network design for new housing developments.

The numbers show why architecture matters now. Europe has passed 295 million homes but only 54% subscribe, so the next gains come from competition and service quality on existing fiber, not new ducts. Indonesia’s fixed broadband penetration of about 42% leaves wide room to grow. In both markets, the network that can host several ISPs and absorb the next speed tier wins more subscribers per kilometre of fiber.

How do you design FTTH network architecture so multiple ISPs can use one residential fiber network?

Pick the layer where each ISP plugs in, then design the network around that choice. There are three: fiber at Layer 1, bitstream at Layer 2 and IP at Layer 3. Each moves work and risk between the network owner and the ISP. For the business side of that choice, compare the open access and retail FTTH models.

BEREC describes bitstream as Layer 2 (Ethernet) and Layer 3 (IP) access, and notes that higher layers add functionality but reduce the ISP’s flexibility. A Layer 2 Ethernet bitstream typically needs VLAN allocation, quality-of-service handling, flexible interconnection and a free choice of customer equipment. BEREC also warns that a native Ethernet network is limited to about 4,000 VLANs, so large open-access networks plan their VLAN scheme early. BEREC’s report dates from 2010. The layers themselves have not changed, but check current national rules before you copy any detail.

Open access inside an apartment building

The same question appears again at the building. The Fiber Optic Association’s MDU guide describes two layouts. In the first, a splitter at the entrance facility sends a drop cable to each unit, which it calls home-run style. This lets the owner offer multiple providers, since each unit’s fiber can plug into whichever provider’s equipment the resident picks. The cost is more fiber and cable. In the second, cascaded splitters sit in the riser or on each floor. They use fewer fibers, but the FOA notes this limits the building to one service provider. Its example is a 1:4 first splitter feeding 1:8 floor splitters, a 32-way split serving 4 floors with 8 units each.

Choose this if

How do you future-proof FTTH network architecture for growing bandwidth demand and high-density housing?

Treat the fiber and splitters as a 30-year asset and the optics as a 10-year one. Demand keeps growing, and upstream is growing fastest. If the passive plant is generation-neutral, each speed upgrade becomes a change of OLT card and ONT, not new construction. Our guide to GPON to XGS-PON migration shows which customers to move first.

These figures are US data from OpenVault, reported through a news summary, so use them as a trend signal and not as a forecast for another country. The direction is clear in any market: usage grows every year, heavy users grow faster than the average, and upstream grows fastest. A residential design that sizes only for today’s downstream will be short within one upgrade cycle.

Size the split with real take-up

Splitter ratio sets the shared capacity per home. The table divides the nominal line rate of each PON by the number of homes on the split, once at the 54% take-up Europe reports and once at the worst case where every home is connected. GPON runs at 2.488 Gbit/s downstream, and XGS-PON at a nominal 10 Gbit/s symmetric under ITU-T G.9807.1.

These are our calculations (line rate divided by split size times take-up), not guarantees. Homes are rarely all busy at once, so real experience is better than the table. Still, the table shows why a 1:64 GPON split gets tight as heavy users grow, and why XGS-PON on the same fiber gives roughly four times the headroom. Note that the XGS-PON row is a PON-level division. Check the OLT and ONT datasheets for the real limits.

Let generations share one fiber

You do not have to choose one PON for the life of the network. ITU-T G.9805 defines how two or more PON systems share a common optical distribution network, using wavelength coexistence elements. It covers GPON, XG(S)-PON, NG-PON, 10G-EPON and 50G-PON. Amendment 2, approved on 29 November 2025, adds Class C+ and Class D optical path loss specifications for multi-PON module configurations and deprecates the 12.5 Gbit/s upstream option of 50G-PON. The 50G-PON physical layer itself is specified in ITU-T G.9804.3.

Design rules for a generation-neutral plant

1. Keep splitter points accessible. Put them in cabinets or MDU rooms you can reach, not buried in joint closures, so a split change is a visit and not a dig.
2. Leave a loss margin. Coexistence elements add loss. Budget the worst path with the element in place and check the optical class against ITU-T G.9805.
3. Use bend-insensitive fiber. The FOA notes it allows small drop cables inside buildings, which matters in dense blocks.
4. Plan for take-up that grows. The FOA advises against assuming 100% take-up and says to plan for future additions. Walk the building before you design it.
5. Reserve ports and duct. Spare OLT ports, spare fibers at the frame and spare innerduct cost little now and avoid civil work later.
6. Prepare migration notices. Each ONT swap is a customer event. TheWriter.id’s free Outage Message Generator drafts copy-ready notices for email, SMS and status pages.

What should you confirm before finalising a residential FTTH architecture?

Confirm the topology, the hand-off, the building wiring and the upgrade path, in that order. This list turns the sections above into questions for a designer or integrator.

• Is the network PON or point-to-point, and does regulation require physical unbundling?
• At which layer does each ISP plug in, and who runs the OLT?
• Is there a VLAN, quality-of-service and interconnection plan that stays inside the VLAN limit?
• Do apartment blocks use home-run drops, or does cascading tie the building to one provider?
• What is the shared capacity per home at realistic take-up, not 100%?
• Is the passive plant generation-neutral, with a loss budget that allows a coexistence element?
• Are splitter points accessible, and are spare ports, fibers and duct reserved?
• Who writes and sends the customer notices for each migration?

FTTH network architecture: frequently asked questions