Passive Optical LAN (POL) Testing | Solutions

Description

What is a passive optical network or PON?

A PON is a fiber-optic network where signals are transmitted from a central office (head-end or hub) to the end user without needing electrically powered equipment along the way. This “passive” characteristic reduces both operational complexity and power requirements. Depending on where the PON terminates, these networks can fall into the fiber-to-the-home (FTTH) category—part of the broader FTTx architecture—which supports point-to-point or point-to-multipoint connections. Point-to-multipoint is particularly cost-efficient since it connects multiple subscribers (e.g., 32 or more) to a single feeder fiber through a fiber distribution hub.

PON challenges

The demand for high-speed broadband services is pushing communications service providers (CSPs) to enhance FTTH networks using next-generation PON technologies to deliver gigabit speeds. However, these upgrades often overlay legacy PON. As a result, network complexity rises, which creates new challenges for field technicians tasked with testing, monitoring, and maintaining service quality.

One of the most significant challenges is maintaining network performance and service continuity, especially as networks grow in scale and complexity. Fault localization across extended fiber paths, especially in high-subscriber-density environments, becomes increasingly difficult. Additionally, ensuring optimal performance requires 24/7 monitoring for proactive identification of issues such as fiber cuts, signal degradation, and other physical layer faults.

To address these challenges, CSPs and field technicians require solutions capable of real-time monitoring, fault detection, and proactive network management.

Key challenges when testing PON

Measuring upstream and downstream power

Testing data from the optical network terminal (ONT) can be challenging. Upstream signals from the ONT are only active when receiving a downstream signal from the optical line terminal (OLT). As a result, measuring power flow in both directions requires specialized equipment.

Testing multiple wavelengths

While legacy GPON utilizes only one downstream and one upstream wavelength, next-generation PON introduces multiple technologies on the same fiber, complicating the testing process. Traditional power meters, which lack wavelength filtering capabilities, cannot separate the two different technologies (e.g., XGS-PON and 10G-EPON) used on the fiber.

Real-time fault detection and resolution

As networks expand, identifying and resolving issues in real time becomes critical. Physical layer faults, such as fiber breaks or connector issues, can significantly impact service delivery. Without continuous network visibility, these issues can lead to prolonged downtime and subscriber dissatisfaction.

What are the next-generation PON technologies?

EPON and GPON

EPON (Ethernet PON) and GPON (Gigabit PON) are widely deployed standards in legacy PON networks. They support typical FTTH applications, offering up to 1 Gbit/s (EPON) or 2.5 Gbit/s (GPON) downstream. GPON is generally preferred in high-speed Internet delivery due to its support for higher data rates.

XG-PON and XGS-PON

XG-PON is a 10 Gbit/s-capable technology designed for high-demand users. It uses asymmetric speeds, typically with 10 Gbit/s downstream and 2.5 Gbit/s upstream. XGS-PON (X Gigabit Symmetric Passive Optical Network), an evolution of XG-PON, supports symmetric 10 Gbit/s speeds in both directions. This makes XGS-PON particularly advantageous for business users, remote work, and high-definition video streaming, as it meets growing demands for high upload speeds.

10G-EPON

10G-EPON offers a symmetrical data rate of 10 Gbit/s, widely used in commercial and residential applications where high bandwidth is essential. Its performance in multi-tenant and densely populated urban environments has contributed to its adoption in markets needing robust scalability and flexibility.

NG-PON2

NG-PON2, which hasn’t seen much deployment in the field, combines WDM-PON with time-division multiplexing (TDM) to increase both speed and user capacity. NG-PON2’s wavelength division multiplexing (WDM) enables multiple wavelengths to be transmitted simultaneously so CSPs can serve many more users while reducing the need for additional infrastructure.

The future of high-bandwidth PON technologies

25G-PON, is it a thing and who uses it?

25G (25 Gigabit) PON is emerging as a mid-term solution for high-speed network requirements, mainly driven by demand from data centers, enterprise users, and CSPs preparing for next-generation applications. It offers downstream speeds of 25 Gbit/s and is ideal for markets needing faster broadband, particularly in densely populated urban areas where high user density demands greater bandwidth. It is also well suited for fiber deep architectures supporting 5G cell sites, as it can handle the increased data flow from 5G backhaul and midhaul networks.

Early adopters include large-scale CSPs worldwide where 25G PON is being tested and deployed as a solution to bridge current demand gaps and prepare for the growth of Internet of Things (IoT), smart cities and 5G-related applications.

Is it too early to talk about 50G PON?

As the next step in PON evolution, 50G PON is being developed to support ultra-high bandwidth needs, with applications in massive Internet of Things (IoT), AR/VR streaming, and high-density environments. 50G PON, which is currently in trial and standardization phases, is expected to be widely deployed in smart city frameworks, ultra-dense metro networks, and high-demand enterprise zones. It’s also being tested for its capability to handle 5G/6G backhaul with low latency, enabling the bandwidth needed to support real-time data-intensive applications like autonomous vehicle systems, telemedicine, and large-scale video analytics.

Telecom giants, particularly in East Asia and North America, are piloting 50G PON in specific environments, such as smart city projects, high-capacity industrial parks and multi-gigabit FTTH initiatives. This technology is especially critical for regions planning for the next phase of digital transformation and for operators looking to sustain the data demands of 5G and future 6G networks.

Testing and monitoring solutions for PON networks

As PON networks advance, CSPs need testing and monitoring solutions tailored for both legacy and next-generation PON environments. The following solutions address the challenges faced by CSPs in maintaining service quality and reliability during different phases of deployment.

Build and operation

EXFO’s remote fiber test monitoring (RFTM) solution is a game changer for CSPs, providing 24/7 monitoring of fiber networks. By integrating RFTM with an advanced optical time domain reflectometer (OTDR), CSPs can proactively identify and locate faults, such as fiber cuts or excessive attenuation, across large-scale PON deployments.

This real-time monitoring capability significantly reduces mean time to repair (MTTR) by enabling rapid fault detection and precise localization without requiring field technicians to physically inspect the network. RFTM ensures that service interruptions are minimized, maintaining subscriber satisfaction while reducing operational costs

Construction and maintenance

The FTBx-730D OTDR is specifically engineered for testing PON networks, making it ideal for technicians handling both construction (dark fiber 1310/1550 nm) and troubleshooting (live fiber 1650 nm) in fiber-to-the-home (FTTH) environments. With high dynamic range, the FTBx-730D accurately tests through splitters, ensuring reliable detection of faults across complex, multi-layered PON architectures.

Activation

The EX1 is a pocket-sized tester that validates bandwidth speed up to full-line-rate Gigabit Ethernet, emulates GPON ONT, fully tests residential WiFi and monitors both residential and business quality of experience.

The EX10 is designed for precise multigigabit testing in PON networks. It provides essential performance metrics such as speed, latency, and service quality over Ethernet connections. With 10G testing capabilities, the EX10 is well suited for validating high-speed residential and business services in XGS-PON networks, which deliver 10 Gbps symmetrical bandwidth. This enables technicians to verify that service level agreements (SLAs) for upload and download speeds, as well as latency, are being achieved. As a result, end users experience optimal connectivity for high-bandwidth applications such as streaming, video conferencing, and remote work. The PPM-350D is designed for the most complex PON networks, supporting multiple standards such as EPON, GPON, XG-PON, XGS-PON, 10G-EPON, and NG-PON2. The unit is equipped with pass-through capabilities, which enable simultaneous testing of upstream and downstream signals, even in the presence of keep-alive burst signals. The PPM-350D offers advanced wavelength discrimination, allowing technicians to pinpoint the power levels of each individual wavelength.

The PPM1 is a more compact and highly portable solution ideal for simpler PON installations and day-to-day field-testing tasks. The PPM1 is compatible with multiple services, including GPON, EPON, XGS-PON and 10G-EPON technologies. Its wavelength-selective design allows it to measure up to two downstream signals simultaneously, assessing power level for rapid and reliable service activation.

Activation and maintenance

The Optical Explorer (OX1) provides essential fiber testing capabilities, such as insertion loss and optical return loss (ORL) measurements, that enable frontline technicians to troubleshoot from the customer location up to the splitter in case of low power/no power. The PPM model for maintenance included in the OX1 PRO includes an inline dual-band power checker ideal for FTTx service activation of GPON, EPON, XGS-PON, 10GE EPON networks.

The above solutions are all part of the EXFO Exchange ecosystem, a cloud-hosted solution for sharing test results and ensuring compliance. Having a connected ecosystem optimizes processes through centralized data and job management, so field technicians and managers get real-time visibility and can complete their jobs faster.

How to choose a PON tester

You need the right PON tester to handle the varying complexities of today’s networks. Two must-have features to look for are automatic detection of PON technology in use and built-in threshold settings to minimize human error. EXFO’s patented PON-aware™ technology automates these processes, offering technicians the visibility and precision needed to maintain high standards of quality in complex PON environments.

When selecting portable PON testing tools, consider the unique requirements of the network and the complexity of the deployment. While the PPM1 is ideal for basic power measurements in traditional PONs, the PPM-350D offers advanced capabilities for wavelength-specific testing in next-gen environments. For fiber verification and troubleshooting outside active PON measurements, the Optical Explorer (OX1) is a go-to tool for quick and accurate results.

Once activated, CSPs must be able to confirm that their XGS-PON deployments meet promised performance levels, so selecting a tool that can provide accurate measurements for advanced gigabit services, such as the EX10, is key in delivering reliable, high-quality service to subscribers.

EXFO’s PON-optimized OTDRs provide the performance and flexibility to meet the demands of modern PON networks, ensuring reliable service delivery and enabling efficient network growth. Whether testing through splitters or troubleshooting live networks, these tools offer the precision and ease of use that technicians need to excel in PON environments.

By integrating EXFO’s RFTM and other advanced solutions, CSPs can ensure their PON networks meet the growing demands of gigabit connectivity, minimize downtime, and optimize operational efficiency.

Want to learn more?

EXFO offers an FTTH PON Testing course that features construction, activation and troubleshooting tips to give your technicians a leg up in the field. Get full details here and contact us for more information.