FTTx: Where the Fibre Ends
The x in FTTx stands for the point where fibre terminates. The further the fibre reaches, the better the performance potential of the last-mile connection:
- FTTH / FTTP: Fibre to the Home or Premises. The optical strand runs all the way to an ONT inside or on the wall of the property. This is the gold standard for residential broadband and the basis for gigabit and multi-gigabit consumer plans. Used interchangeably in most markets; the UK and Australia officially prefer FTTP.
- FTTC: Fibre to the Cabinet. Fibre runs to a street cabinet, then VDSL2 copper pairs cover the final few hundred metres to the home. Speed depends heavily on line length — a 50 m run can deliver 80 Mbps while a 400 m run may only reach 30 Mbps. Upload is always asymmetric and latency is higher than pure fibre.
- FTTB: Fibre to the Building. Common in apartment blocks. Fibre reaches the basement or comms room, then copper or Ethernet inside the building connects individual units. Shared internal cabling quality varies widely.
PON Technologies Compared
| Standard | Downstream | Upstream | Notes |
|---|---|---|---|
| GPON | 2.5 Gbps shared | 1.25 Gbps shared | Dominant mass-deployment standard worldwide |
| XGS-PON | 10 Gbps shared | 10 Gbps shared | Symmetric 10G; common for multi-gig upgrades, often on same fibre as GPON |
| EPON | 1 Gbps shared | 1 Gbps shared | Ethernet-based PON; common in Japan, China, and parts of Asia |
| NG-PON2 | Up to 40 Gbps aggregate | Up to 10 Gbps aggregate | Uses multiple wavelengths (TWDM); enables very high capacity per feeder fibre |
| Active Ethernet | Up to 10 Gbps dedicated | Up to 10 Gbps dedicated | Each subscriber gets a dedicated fibre strand to the exchange; no shared PON capacity |
The Access Network Parts
| Part | Meaning | Job |
|---|---|---|
| OLT | Optical Line Terminal | Provider equipment at the exchange or central office; schedules all ONT traffic |
| Splitter | Passive optical splitter | Splits one feeder fibre to serve multiple premises; typical ratio is 1:32 |
| ONT / ONU | Optical Network Terminal / Unit | Converts optical signal to Ethernet at the subscriber premises |
How PON Splitters Work
A passive optical splitter divides the light signal from one feeder fibre into multiple outgoing paths without any active electronics in the field. A typical residential deployment uses a 1:32 split ratio, meaning one feeder fibre serves up to 32 homes. The splitter requires no power and no maintenance. Because the split is passive, the OLT at the exchange manages time-division multiplexing (TDMA) to allocate upstream transmission slots to each ONT so their signals do not collide on the shared path.
Splitting does reduce optical power budget. A 1:32 split introduces roughly 15 dB of insertion loss. Fibre plant designers account for this by specifying maximum distances and confirming the total loss budget stays within the ONT's receive sensitivity. Higher split ratios such as 1:64 are possible but reduce the power margin available for longer runs or connectors with higher loss.
PON Wavelength Plan
GPON and XGS-PON use separate wavelengths for downstream and upstream traffic on the same fibre strand, allowing full-duplex communication over a single fibre:
- 1490 nm: Downstream data (OLT to ONT) in GPON.
- 1310 nm: Upstream data (ONT to OLT) in GPON and XGS-PON.
- 1577 nm: Downstream in XGS-PON.
- 1550 nm: Reserved in many deployments for a broadcast RF overlay, historically used to deliver analogue or digital TV signals directly over the fibre without converting to IP.
Fibre and Latency
Light travels through glass fibre at approximately two-thirds the speed of light in a vacuum, giving a propagation speed of roughly 200,000 km/s. This produces very low latency on the access segment — typically 1–2 ms from the ONT to the nearest exchange. Combined with no electrical interference, no crosstalk between subscribers, and no signal degradation over distance comparable to copper, fibre offers the most consistent low-latency access medium available for fixed broadband. A well-provisioned FTTP connection should show idle latency under 5 ms to a local server in a speed test.
Market Terms by Region
Different countries use different terminology for the same underlying technologies:
- United Kingdom: Openreach and altnets use FTTP for full-fibre and FTTC for the older VDSL2 cabinet product. The term "fibre broadband" has historically been applied to both FTTC and FTTP in marketing, which can cause confusion.
- European Union: FTTH and FTTB are the standard terms. Regulators track FTTH coverage separately from FTTC and other FTTx variants in their connectivity reports.
- Australia: The NBN (National Broadband Network) uses FTTP, FTTC, FTTN (fibre to the node, similar to FTTC), HFC (hybrid fibre-coaxial), and Fixed Wireless depending on the area. The NBN upgrade programme is progressively replacing FTTN and FTTC with FTTP.
Shared Capacity and Real-World Speed
PON is shared, but it is not shared in the same way as old cable segments. The OLT assigns time slots and capacity across all ONTs on the splitter. A well-designed PON has enough headroom that users see consistent speeds at peak times. Congestion can still happen if the provider oversells a segment, uses too aggressive a split ratio, or underbuilds backhaul from the exchange to the core network.
Speed tests on FTTP should normally show strong upload and low latency over Ethernet. If wired results are good but Wi-Fi is poor, the fibre access network is not the problem. Check router WAN port speed, Wi-Fi standard, mesh backhaul, client adapters, and device placement before assuming an issue with the optical line.
Frequently Asked Questions
What is FTTP?
FTTP means fibre to the premises. The fibre optic line reaches the home or business instead of stopping at a cabinet or neighborhood node.
What is the difference between GPON and XGS-PON?
GPON is a widely used passive optical network technology offering 2.5 Gbps downstream shared capacity. XGS-PON is a newer 10G symmetric system that supports multi-gigabit plans and can often be deployed on the same physical fibre infrastructure.
Does fibre always mean symmetric speed?
No. Fibre can support symmetric speeds very well, but the plan and provider policy determine whether upload equals download.