When you spot GPON or XGS-PON in a provider’s offer, it refers to the type of passive optical network that brings the internet to you. An ordinary user does not choose this technology (the provider does), but it pays to understand what the acronyms mean and why upload is usually lower than download. Let us explain it simply and straight.

What a passive optical network (PON) is

PON (Passive Optical Network) is the way a provider distributes fibre to its customers. A single optical fibre from the exchange is split among several subscribers through a passive splitter. The word “passive” is the key here - the splitter needs no power, it only divides the light into several fibres.

The network has three main parts:

  • OLT (Optical Line Terminal) - the unit in the provider’s exchange where the network begins.
  • Splitter - the passive splitter that divides one fibre into several.
  • ONT/ONU (Optical Network Terminal) - the end unit in your home where the fibre plugs in.

A typical split ratio is 1:32 to 1:64 (sometimes up to 1:128). That means 32 to 64 households share one fibre from the exchange. To understand how fibre physically reaches you, read our article on the FTTH fibre connection.

Why the capacity is shared

This is the most important thing to grasp. The capacity of a PON network is shared among all subscribers on one fibre. It is the opposite of a dedicated link (point-to-point, active Ethernet AON), where each customer has their own separate line all the way to the exchange.

In practice this usually does not matter - the provider plans the capacity so that everyone gets what their contract promises. But it is the principle that explains why fibre can reach so many households at a reasonable price. For more on what actually affects your speed, see our article on internet speed.

GPON: the most widespread standard

GPON (Gigabit PON, standard ITU-T G.984) is today the most used provider technology for fibre to the home. It offers:

  • 2.488 Gbit/s downstream (download)
  • 1.244 Gbit/s upstream (upload)

It is therefore asymmetrical - the upload is lower than the download. For most households that makes sense, because you typically download more than you send. If you see GPON in an offer, you are getting a proven and widely deployed standard.

EPON: the Ethernet route

EPON (Ethernet PON, standard IEEE 802.3ah) is built on Ethernet, which makes it cheaper. It offers 1 Gbit/s symmetrically (the same up and down). It is widespread mainly in Asia, and there is a faster variant, 10G-EPON. In Europe you will meet it less often than GPON.

Some end units are so-called XPON or combo ONT devices - a universal unit that handles both GPON and EPON and detects on its own which one the provider uses.

XG-PON and XGS-PON: the ten-gigabit generation

When ordinary gigabits are not enough, the faster standards step in:

  • XG-PON (standard G.987): 10 Gbit/s down / 2.5 Gbit/s up, still asymmetrical.
  • XGS-PON (standard G.9807.1): 10 Gbit/s symmetrically. The letter S stands for “symmetrical” - the same speed up and down. This is the current direction for faster connections.

XGS-PON is what to look for in newer and faster offers. You will appreciate the symmetrical upload when backing up to the cloud, on video calls or when working from home.

NG-PON2: the future with multiple wavelengths

NG-PON2 (standard G.989) goes even further - it can use several light wavelengths at once and so deliver up to 40 Gbit/s aggregate. For now this is more of a deployment for providers and larger sites than for the ordinary home.

Passive optical networks compared

StandardDownloadUploadSymmetryStandard
EPON1 Gbit/s1 Gbit/ssymmetricalIEEE 802.3ah
GPON2.5 Gbit/s1.25 Gbit/sasymmetricalITU-T G.984
XG-PON10 Gbit/s2.5 Gbit/sasymmetricalG.987
XGS-PON10 Gbit/s10 Gbit/ssymmetricalG.9807.1
NG-PON2~40 Gbit/s aggregatemultiple wavelengths-G.989

What to take away

The PON technology is chosen for you by the provider, while you pick the speed and the price. But once you know what the acronyms mean, they stop being a mystery. GPON is the proven standard for most homes, XGS-PON is the faster, symmetrical future. The asymmetry (lower upload) is not a fault but a feature of the technology. And the fact that fibre is shared is the reason it can reach so many people. If the fibres themselves interest you, see our article on types of optical cable.

Not sure which offer is worth it, or looking at fibre for a more remote area? Get in touch and we will advise, or design and set up the network in your home.

This article is part of our Computer networks overview.