Passive Optical Networking (PON) utilizes fiber optic cabling to provide Ethernet connectivity from a central data source to endpoints. PON differs from active optical networking as it employs optical beam splitters to distribute a single signal to multiple branches without powered devices. Explore PON types, applications, architecture, and more in-depth.
What is PON?
PON, a passive optical network, adopts point-to-multipoint (P2MP) topology and optical splitters to distribute data from a single source to multiple user terminals. The term “passive” indicates that the fiber and splitting/combining components are unpowered.
Unlike active optical networks (AON), PONs require power only at the transmit and receive points. Once the signal is transmitted, optical transmission in PONs becomes unpowered, resulting in significant cost savings for the system.
How does a PON Work?
There are two main PON architectures: Gigabit PON (GPON) and Ethernet PON (EPON), offering data transfer speeds of 1 Gbps to 10 Gbps. PONs use point-to-multipoint links with splitters, enabling one fiber strand from an OLT to serve multiple subscribers, up to 128 locations.
To set up a PON, the service provider builds an optical fiber network connecting directly to clients and to an OLT in a central office or POP. The OLT converts Ethernet traffic into PON traffic.
Optical networks use light beams through fiber-optic cables. After leaving the OLT, data travels to a splitter near subscribers, replicating light wavelengths to ONUs/ONTs without electrical power, using mirrors and glass to refract light.
Different Types of PON
PON technology has progressed through various stages since the 1990s. Here’s an overview of the different PON technologies and their characteristics.
APON (155Mbps down / 155Mbps up)
Oldest PON technology, based on Asynchronous Transfer Mode (ATM) with dynamic bandwidth allocation.
BPON (622Mbps down / 155Mbps up)
Enhanced version of APON with 622Mbps transmission rate, offering dynamic bandwidth allocation, protection, and Ethernet access.
EPON (1.25G down / 1.25G up)
Seamlessly compatible with Ethernet equipment, supporting symmetrical upstream and downstream speeds of up to 1.25Gbps.
10G-EPON (10G down / 10G up, 10G down / 1.25G up)
Offers 10Gbps speeds in both symmetric and asymmetric configurations.
GPON (2.5G down / 2.5G up)
Gigabit Passive Optical Network with 2.5Gbps speed, using IP and ATM or GPON encapsulation method.
XG-PON (10G down / 2.5G up)
Faster variant of GPON with the same characteristics, still awaiting widespread deployment.
XGS-PON (10G down / 10G up)
Symmetric, high-bandwidth version of GPON, compatible with GPON on the same fiber.
NG-PON2 (10G down / 10G up, 10G down / 2.5G up)
Offers new features like wavelength mobility and channel bonding, coexisting with GPON, XG-PON, and XGS-PON.
25G-PON (25G down / 10G or 25G up)
Suitable for various applications, coexisting with 25GS-PON, G-PON, XG-PON, XGS-PON, and NG-PON2.
50G-PON (50G down / 10G or 25G or 50G up)
Next-generation standard with 50G downstream speed for real 10G services, 5G fronthaul, and residential services. Suppliers are developing necessary chips and products.
PON Components
Passive Optical Networks (PON) rely on essential components like the Optical Line Terminal (OLT), Optical Network Terminal (ONT), and Fiber Optic Splitter to efficiently deliver high-speed broadband services.
Optical Line Terminal (OLT)
Often referred to as OLT, it serves as the core of a PON, acting as the gateway and converting standard signals from the service provider to the PON system’s frequency and frame. The OLT also coordinates the multiplexing of data on Optical Network Terminals (ONTs). Due to its critical role, the price of OLTs is higher compared to ONTs. For instance, in GPON, the OLT costs $58.0, while the GPON ONT costs $36.0.
Optical Network Terminal (ONT)
Also known as ONU, the ONT is a specialized modem located at the end user’s premises. It performs the crucial task of converting optical signals into electrical signals, enabling broadband access for various devices like WiFi routers, TVs, desktops, etc. The ONT also sends aggregated and optimized data back to the OLT from the end users.
Fiber Optic Splitter
In PON networks, the fiber optic splitter plays a vital role in splitting one physical fiber network into multiple Point to Multi-Point (P2MP) connections. By connecting with the OLT and ONT, the fiber splitter can achieve various split ratios such as 1:2, 1:4, 1:8, 1:16, 1:32, and more, facilitating efficient data distribution within the PON architecture.
Benefits of PON
Passive Optical Network (PON) technology offers several key benefits that make it an attractive choice for various applications.
- Low Total Cost: PON’s cost-effectiveness arises from its use of a single fiber to serve multiple users in a point-to-multipoint configuration. This reduces infrastructure and material costs compared to active point-to-point systems.
- Reliable Performance: Leveraging fiber optic technology, PON networks deliver enhanced reliability. The smaller, lighter, and more flexible fiber optic cabling ensures seamless connectivity through homes and buildings, contributing to its reliability.
- Ease of Maintenance: PON networks exhibit robustness against electromagnetic interference and noise, maintaining signal integrity over planned distances. Clear identification of faults in PON elements, such as OLT, ONT, and Fiber Splitter, facilitates easier troubleshooting and maintenance.
- Efficient Power Use: The reduced power requirements of PON networks lead to fewer maintenance tasks and lower chances of powered equipment failures, contributing to overall efficiency.
- Flexible and Scalable: PON’s point-to-multipoint architecture provides exceptional flexibility and scalability. This adaptability makes it an ideal choice for businesses as their network needs evolve, offering support for changing bandwidth requirements.
Limitations of PON
Passive Optical Networks (PON) offer numerous benefits but also come with certain limitations. Consideration of these limitations helps optimize their deployment for various network requirements.
- Distance Limitation: PONs have a restricted range of 20 to 40 km, unlike active optical networks that can cover up to 120 km. This limitation may hinder their use in applications requiring longer distances.
- Diagnostic Challenge: Troubleshooting in PONs can be complex. Technicians may need to unplug the ONT (home equipment) for diagnostics, causing service disruptions. Additionally, faulty equipment in the PON can affect multiple clients.
- Time-consuming: Setting up PONs takes more time compared to point-to-point (P2P) active networks. The design and placement of splitters for an optimal system configuration require careful planning.
PON and FTTx Applications
PONs enable high broadband connections with optical fiber for the last mile of telecommunications. FTTx uses optical fiber for broadband delivery to various devices in the last mile.
Common FTTx configurations include:
- FTTH (fiber to the home): Optical fiber terminates inside an individual home or business.
- FTTP (fiber to the premises): May be used to describe optical cabling terminated at these places.
- FTTB (fiber to the building): Similar to FTTH, FTTB optic cabling stops at a building’s electrical room.
- FTTC (fiber to the curb): Cabling terminates within 300 yards of a subscriber’s premises.
- FTTN (fiber to the neighborhood): Optical cabling ends a few miles from a user’s premises.
PONs provide high bandwidth to end users, making optical networks essential for IT professionals to understand and develop critical skills with broad applications and industry demand.
PON-based POL: Future-Proof LAN Solution
Passive Optical Local Area Network (POL) is an innovative LAN networking solution based on Passive Optical Network (PON) technology. With fiber optic and point-to-multipoint architecture (P2MP), POL efficiently delivers TV, telephone, and Internet services to up to 32 users through a single central point (OLT). This future-proof and high-capacity optical LAN ensures seamless connectivity for indoor, campus, and mobile backhaul applications, covering up to 20 kilometers without the need for telecommunications rooms, switches, or frequent power sources.
FAQs about PON
Q: What is the maximum speed of PON?
A: The maximum speed of PON depends on the technology used. For example, GPON supports 2.5Gbps, while XGS-PON supports 10Gbps. Currently, the maximum speed is 50Gbps for 50G-PON.
Q: What is the difference between PON and GPON?
A: GPON is a specific type of passive optical network (PON) with a typical data rate of 2.5Gbps.
Q: Is an ONT required to have a power supply?
A: Yes, the ONT should remain powered for proper functionality, so it should not be turned off.
Q: How can I connect my PON ONT to the WIFI router?
A: Generally, you can link the ONT to the WIFI router using an Ethernet cable.
