Fiber-to-the-home (FTTH) is a system that installs fiber optics directly from a central point into individual buildings, such as homes and apartments. The deployment of FTTH has come a long way before customers adopted fiber instead of copper for broadband Internet access.
There are two basic paths for deploying high-speed FTTH networks: Active Optical Networks (AON) and Passive Optical Networks (PON).
So AON vs. PON networks: what’s the difference?
What is an AON network?
AON is a point-to-point network architecture in which each subscriber has its own fiber optic line that is terminated on an optical concentrator. An AON network includes electrical switching equipment, such as routers or switching aggregators, to manage signal distribution and provide directional signaling to specific customers.
Switches turn on and off in a variety of ways, directing input and output signals to the appropriate locations. The reliance of AON networks on Ethernet technology makes interoperability between providers easy. Subscribers can select hardware that provides the appropriate data transfer rate and scalability as their needs increase, without the need for network reorganization. However, AON networks require at least one switch aggregator per subscriber.
What is a PON network?
Unlike AON networks, PON is a point-to-multipoint network architecture that uses passive splitters to separate and collect optical signals. Fiber optic splitters allow PON networks to serve multiple users over a single fiber without the need to deploy separate fibers between the central office and the end users.
As the name suggests, PON networks do not include electrical switching equipment and share fiber bundles for parts of the network. Active equipment is only required at the source and receiver ends of the signal.
In a typical PON network, the PLC splitter is the core device. Fiber taps combine multiple optical signals into a single output, or fiber taps take a single optical input and distribute it to multiple individual outputs. These taps for PON are bi-directional. It should be clarified that fiber optic signals can be sent downstream from the central office, broadcasting to all subscribers. Signals from subscribers can be sent upstream and combined into a single fiber to communicate with the central office.
AON vs PON Networks: Differences and Options
Both PON and AON networks form the fiber optic backbone of FTTH systems, enabling individuals and businesses to access the Internet. Before choosing a PON or AON, it is necessary to clarify the differences between them.
When it comes to AON and PON networks, the main difference between them is the way the optical signal is distributed to each customer in an FTTH system. In an AON system, customers have a dedicated fiber bundle, which allows them to have dedicated bandwidth instead of sharing it with others. In a PON network, users share a portion of the network’s fiber bundle in the PON. As a result, people using PON may experience slower system performance because all users share the same bandwidth. If a problem occurs within a PON system, it can be difficult to find the root cause of the issue.
The largest ongoing expense in the network is the cost of powered equipment and maintenance. Compared to AON networks, which are active networks, PON networks require less maintenance of passive devices and do not require a power supply. Therefore, PON is cheaper than AON.
Coverage distance and applications
AON can cover distances of up to 90 kilometers, while PON is often limited by fiber optic cable lines up to 20 kilometers long. This means that PON users must be geographically closer to the source signal.
In addition, if it is related to a specific application or service, there are several other factors that need to be considered. For example, if RF and video services will be deployed, then PON is usually the only viable solution. However, if all services are based on Internet protocols, then PON or AON may be appropriate choices. If longer distances are involved and providing power and cooling to active components in the field may cause problems, then PON may be the best choice. Or, if the target customer is a commercial customer or the project involves multiple residential units, then an AON network may be more appropriate.
AON vs. PON networks: Which FTTH do you prefer?
When choosing between PON or AON, it is important to consider what services will be delivered over the network, the overall network topology, and who the primary customers are. Many operators have deployed a mix of both networks in different situations. However, as the need for network interoperability and scalability continues to grow, network architectures are trending towards allowing any fiber to be used interchangeably in PON or AON applications to meet future demands.