What Is A Passive Optical Network (PON)?

Passive optical networks (PONs) are a type of telecommunications network designed to take advantage of the inherent diversity of traffic in network communications. PONs are often used in residential, business and enterprise settings, as they can provide high bandwidth and reliability with economy of deployment due to their sharing of bandwidth between users. Knowing the basics of PON technology is essential for anyone considering implementing this type of network.

Here we take a closer look at what PONs are and how they work. We will also discuss the benefits of using this technology and explore some of the PON systems available on the market today.

Passive Optical Network 101

A Passive Optical Network (PON) is a network that delivers high-speed broadband internet and other services to subscribers via a simplified fiber-optic network. Telecommunications providers typically use PON networks to deliver fiber-to-the-building (FTTB) services due to its simplicity of topology and lack of field equipment to be maintained. In a PON system, a single optical fiber serves multiple subscribers, with each subscriber connected via optical splitters and network units. Up to 32 subscribers can be connected to a single fiber link versus 32 separate fiber links for an active switched optical network.  Each subscriber can then have a nearly unlimited number of data ports connected, subject only to bandwidth limitations on the incoming link.

This architecture reduces the amount of expensive active equipment required to be deployed compared to traditional point-to-point, or switched fiber-optic networks. PON systems typically use wavelengths of 1310nm for upload traffic and 1490nm or 1550nm for download traffic. The most common type of PON system is an Ethernet PON (EPON), which uses Ethernet protocols for data transport.

Other types of PONs include Asynchronous Transfer Mode (ATM) PONs (APONs), which was the first PON standard and has completely been replaced.  Broadband PON (BPONs) were the second deployment of PON technology and have also mostly been updated with GPON technology today.

Gigabit-Capable PON Systems (GPONs) are the predominate technology today. While GPONs offer higher data rates, they are also more expensive to deploy and maintain. GPONS typically employ ATM for voice and Ethernet for data transport.  GPON speeds have progressed from the initial 1 Gigabit per second (Gbps) to 10 Gbps and now even 40 and 100 Gbps speeds are available. 

How Does A Passive Optical Network Work?

A PON is comprised of three main components:  An optical line terminal (OLT), optical splitters, and many optical network units (ONUs). The OLT is usually located at the network’s headend, while the ONUs are typically deployed at the customer or user premises. The optical splitter is used to divide the optical signal from the OLT into several individual signals running on separate fibers, which are then sent to the ONUs.

Each ONU can serve multiple customers; however typically each customer will have a dedicated unit within their premises. PONs are typically deployed in point-to-multipoint architectures, meaning that each OLT will serve multiple ONUs. This makes PONs well suited for large-scale deployments, such as service provider networks in dense urban areas, or large campus-wide systems.  Even large office building deployments can benefit from the economies of PON networks, provided the number of users justifies the cost of the OLT, which is the primary cost driver of the system.  PONs have many advantages over other access technologies, including high bandwidth efficiency and low cost.

Traditional Network vs. Passive Optical Network

Traditional Network

Most networks consist of a combination of active and passive components. Active components, such as network switches and routers, direct traffic and require a power source. Passive components, such as fiber-optic cable or copper wire, provide a path for signals but do not require power. In small networks, with only a few devices, active components’ power requirements and heat output can be negligible.

However, in large networks with hundreds or thousands of devices, the cost of the active components, primarily the network switches, becomes very significant, as does the amount of space they require and the power they consume.  The heat output of active components can also be a significant concern in large actively switched networks, requiring air-conditioned data cabling rooms. One way to reduce the heat output of a network is to use more passive components. 

Traditional active networks also require more data closet space throughout the system, including Main Distribution Frames (MDFs) and Intermediate Distribution Frames (IDFs).  This data closet space consumes potential leasable floor area, reducing the revenue potential of the building or driving up the amount of square footage required in the building.

Passive Optical Network

On the other hand, a PON delivers fast internet speeds to users and uses a single strand of optical fiber to connect a service provider’s network to multiple subscribers, typically 32 per fiber strand. The main advantage of using a PON is that it can provide high-speed Internet service to multiple users simultaneously without the need for costly and complex active network infrastructure.  There are no active network switches required to distribute the optical signal to multiple users downstream of the OLT device.  PONs offer several other advantages over traditional networks, including lower maintenance costs, potentially higher security, and easier scalability. As the demand for high-speed Internet connectivity continues to grow, PONs will likely become the preferred choice for Internet service providers (ISPs) and their customers.  The success of the Verizon Fios system, which was the first large scale deployment of PON technology in the United States in 2004, demonstrates the economies of scale that a PON network provides over conventional switched networks.  

Benefits of PON

Cheaper to Deploy at Scale

One of the main benefits of using a PON is that it is cheaper to deploy than other types of networks when dealing with large scale network installations. This system uses a single fiber-optic cable to connect multiple subscribers and uses the passive splitters to distribute fiber closer to the user.  By comparison, other network topologies require multiple copper cables and/or individual switched fibers to connect each subscriber or user to the central points of distribution, located in the IDFs throughout a building. PONs require less hardware than other types of networks and can be a more cost-effective option; however only at scale.  The key driving factor in determining the cost/benefit of deploying a PON is balancing the cost of the OLT device, which can be very expensive, with the number of traditional active network switches required to accomplish the same distribution of the data signals.

Uses Existing Fiber-Optic

Another significant benefit of PONs is that it can use existing fiber-optic infrastructure. PONs can be deployed quickly and easily without requiring new fiber-optic cables. They also offer high bandwidth and low latency, making them ideal for video conferencing and streaming media applications. In addition, PON networks are highly scalable and can be easily expanded to meet future demands. As a result, PONs are an increasingly popular choice for businesses and organizations looking to upgrade their existing network infrastructure.

Faster Speeds

PONs, specifically GPONs, also offer faster speeds. With a PON, data can be transmitted at up to 100 Gbps, significantly faster than the traditional networks. In addition, the network is also less susceptible to interference, making it a more reliable option for users who want a consistently high-speed connection.

Plenty of Upgrade Paths

A PON is an excellent investment for the future of your building because it offers many upgrade paths. As technology improves, the system can easily upgrade to support higher data transmission rates and new services without replacing the cabling.  Changing the speed of the network involves changing the OLT and ONU equipment using shorter wavelength (higher data speed) lasers.

PONs also support wavelength-division multiplexing (WDM), which allows multiple services to be carried over a single fiber. This makes them an ideal solution for buildings that need to support various applications on a single network. In addition, a PON is highly scalable and can be easily expanded to support more users or services as needed.

Bottom Line

PONs are becoming increasingly popular due to their many benefits. We hope this blog has helped you better understand what PON is and how it would benefit your building

PONs are just one facet of the telecommunications landscape. They can be faster, more reliable, and easier to manage than traditional systems. If you’re looking for a telecommunications upgrade for your business or building, talk to our team today about getting a passive optical network.

Our team at Schnackel Engineers can help you get set up with the most reliable, latest, and greatest technology so you can stay connected and productive.