What is 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.

What is a Passive Optical Network (PON)?

Passive optical networking (PON), like active optical networking, uses fiber-optic cabling to provide Ethernet connectivity from a main data source to endpoints. While there are many subtle differences, a clear distinction between active optical networking and PON topology is PON’s use of a technique that distributes a single signal to multiple branches through unpowered devices called optical beam splitters.

How does a PON work?

A Passive Optical Networking system consists of an optical line terminal (OLT) at the communication company’s central office and several optical network units (ONUs) near end users. Typically, up to 32 ONUs can be connected to a single OLT. The word passive simply describes the fact that optical transmission has no power requirements or active electronic parts once the signal is transmitted across the network. This is in contrast to active optical networks, which require electrically powered switching hardware to pass cells or frames across the fiber cabling.

This image shows how redundant OLT hardware commonly sits in the telecommunications service provider’s central office. From there, fiber cabling is distributed up to 20 kilometers from the central office and is split into multiple ONUs using a passive optical splitter, which terminates the fiber connection close to the customer’s demarcation point. The ONU will then deliver a network handoff using copper or fiber Ethernet cables, making it easy for customers to connect to their existing local area networks (LANs).

Types of Passive Optical Networks (PON)

There are a few different types of PONs and terms to know:

• APON stands for asynchronous transfer mode (ATM) passive optical networks. APON was the first PON standard and was used for business applications. Unlike Ethernet or the Internet using variable packet sizes for data, APON uses fixed-sized cells.
• BPON stands for broadband passive optical network. BPON was similar to APON but it introduced the support of wavelength division multiplexing (WDM) which allows multiple ISPs to transmit on the same single fiber at different wavelengths.
• EPON stands for Ethernet passive optical network. EPON uses Ethernet packets instead of ATM cells. EPON also uses Internet Protocol (IP) to carry data, voice, and video data. It generally delivers 1G symmetrical bandwidth, which makes it a popular choice.
• GPON stands for Gigabit Ethernet passive optical network. GPON uses ATM for voice, Ethernet for data, and proprietary encapsulation for voice. It offers faster Gbps than EPON on downstream and upstream bandwidths. There are different variations of “GPON” that essentially enhance the downstream/upstream wavelength, speed, and overall transmission reach. These variations are things like XG-PON or XGS-PON.

What are the advantages of passive optical networks?

The passive nature of PONs gives them several advantages over active optical networks:

• Lower costs: PONs are simpler, with fewer components, unpowered splitters, and fewer fiber cables, so they tend to cost less to deploy and maintain.
• Energy efficiency: PONs are more energy efficient than active networks because they don’t require power to run and cool active components.
• Reliability: As PONs use fewer passive optical components, which are less prone to failure than powered switching equipment, PONs tend to be more reliable.
• Scalability: PONs are easy to scale by adding more optical network terminals (ONTs), while active networks are more likely to require infrastructure upgrades as they expand.

The limitations of PONs

The potential drawbacks of passive optical networks include the following:

• They require an extensive fiber deployment.
• Larger networks can become less efficient due to the amount of management traffic overhead being transported from the central office to individual customer ONUs.
• Unlike active-powered network technologies, PONs must adhere to strict transport distance limitations.

Common Passive Optical Network applications

• Residential broadband: ISPs usually use PONs to provide high-speed internet access to homes and residential buildings. That way, ISPs ensure the internet connection is reliable and can maintain various services, like video streaming or low-latency online gaming.
• Business connectivity: PONs are widely used in commercial settings to ensure businesses a high-quality and widely scalable internet connection. Usually, PONs satisfy the connectivity needs of retail stores, medium-sized businesses, and enterprise offices.
• Educational and institutional networks: PONs are perfectly suitable for educational institutions, governmental facilities, and health institutions because it’s a cost-efficient networks that can ensure effective data sharing, device connectivity, and smooth communication between various locations and departments.

Conclusion

As PON technology continues to improve, the strategic and economic advantages of PON deployment become more compelling. The challenges being addressed by designers of future generations include improved range capability and higher splitter ratios to reduce cable outlay even further. These improvements, combined with speeds now reaching 10 Gbps and soon to reach 50 Gbps and beyond, will help to continue the expansion of passive optical networks into the smart cities, universities, hospitals, and corporations that make up the connected world of tomorrow.