PON standard evolution

Hello, everyone!

Today I want to show you the PON standard evolution. The first standards were APON and BPON, today we use GPON/10G PON and EPON/10G EPON, and we are talking about new technology for the future – 40G TWDM PON, 100 GPON, and 100G EPON.

Figure 1. Evolution of PON standards

The optical network offers amazing possibilities. Bandwidth is practically unlimited. It allows the transfer of a huge amount of information. The effect of electromagnetic interference does not exist. Old technologies that use copper cables have many problems (various types of noise, crosstalk, power supply of active components, etc.) and require big maintenance. In addition to these problems, these systems cannot provide enough speed for the growing needs of humanity.

First, optical networks can be divided into two main groups:

• Passive networks. This network does not contain active elements, such as optical amplifiers, repeaters, optical switches, etc. It contains components such as optical cables, optical connectors, optical splitters, WDM components, etc. We use passive optical networks for access networks.

  
  

• Active networks. In this group, the network has active components, such as optical amplifiers, optical repeaters, or optical switches. These types of networks can distribute signals over long distances and therefore require signal amplification. You need to consider the location of the active component, as well as its power supply.

There are three different topologies for access optical networks:

• Full star topology with P2P connections. In this network, each user has their own fiber. In this way, users get a very reliable network that provides all the bandwidth for each user.

  
  

• Active star topology with P2P bonds. In this type of topology, each user is connected to a local optical switch. This optical switch is connected to the access node by a trunk fiber. The trunk fiber optic is shared by multiple users.

• PON - Passive optical networks. This is a very popular technology and it is widespread. There are many different PON technologies: APON, BPON, GPON, EPON, etc. PON is a P2MP network, one fiber can be distributed to 32, 64, 128, or 254 customers. All of these technologies are so-called TDM PON (Time Division Multiplexing).

Figure 2. PON – Passive Optical Network

The PON technologies are defined by ITU-T:

• APON (G.983)

• BPON (G.983)

• GPON (G.984)

• 10G PON or XG(S) PON (G.987)

• 40G TWDM PON

• 100G PON (25G/10G, 25G/25G, Nx25G (100G)/25G)

PON technologies specified by IEEE:

• EPON (802.3 ah),

• 10G EPON (802.3 av)

• 100G EPON (25G/10G, 25G/25G, Nx25G (100G)/25G)

Figure 3. The spectrum of GPON, XG(S) PON, and TWDM PON

All these technologies consist of OLT (Optical Line Terminal), ODN (Optical Distribution Network), and ONU (Optical Network Unit).  In figure 2, we can see the architecture of the PON. The maximum distance between OLT and ONUs is about 20km, with a maximum split of 64. All of this technology use only one fiber for communication, with different wavelength for upstream and downstream. As we can see in figure 3, we can implement two technology with one ODN, because these systems use different wavelengths.

Today, GPON and GEPON technology are actual technology, while XG(S) PON and 10G EPON technologies are used only in a few countries (China, Korea, Japan, etc.). Other next-generation technologies are still in development, while APON and BPON are no longer used.

At the end of this article, I will give you a table with the main characteristics of actual and old PON technologies.

Thank you!