Understanding PON ONU Ports and Its Application

Posted on Jun 11, 2024 by

The ONU, a key device in a PON (Passive Optical Network), converts optical signals into electrical ones for users. It comes with various ports to suit different needs. This article uses the FS ONU TA1910-4GVC-W as an example to explain these ports and their connections in detail.

 the port of FS ONU TA1910-4GVC-W           Figure 1: the port of FS ONU TA1910-4GVC-W

Essential Ports on PON ONUs

PON Port

The PON port is like the main gate on the ONU (Optical Network Unit), connecting it to the Optical Distribution Network (ODN). It's the main way for user devices to join the PON, linking them with the fiber optic network. Through this port, the ONU gets light signals from the OLT and sends back electrical signals, allowing signals to go both ways.

Users can hook up their devices to the main network through the PON port, getting access to fast, smooth network services. For example, businesses can link up to their company networks using this port, connecting to LANs, WANs, or cloud services for smooth data flow and communication.

the PON port of OLTFigure 2: the PON port of OLT

LAN Ports

The LAN port provides a wired network interface, typically an Ethernet interface. The ONU connects to user terminal devices, such as computers and routers, via network cables, enabling LAN access and usually supporting transmission speeds of 10/100/1000 Mbps. Its functions include supporting internet access for home or small office environments, providing a stable network connection, and supporting data exchange and network expansion.

Home users typically connect the ONU to a wireless router to achieve wireless network coverage throughout the house, while enterprise users may connect it to a switch to build a LAN, meeting the needs of multiple users in an office setting.

the LAN port of OLTFigure 3: the LAN port of OLT

Common Ports on PON ONUs

Apart from the necessary PON and LAN ports, FS ONUs also come with additional ports like telephone, USB, and RF ports to meet various customer needs. For instance, the FS ONU TA1910-4GVC-W, designed for single-family homes, includes a PON port connected to the OLT, along with 4 LAN ports, 2 telephone ports, 1 USB port, and 1 CATV RF port. These ports support services like VoIP, Ethernet, and cable TV. Next, we'll delve into these ports in detail.

TEL Ports

TEL ports, also known as POTS (Plain Old Telephone Service) ports, are interfaces used to connect traditional telephone devices. On an ONU (Optical Network Unit), the role of POTS ports is to facilitate the access and transmission of traditional telephone services. Specifically, POTS ports allow users to connect standard fixed telephone devices (such as traditional telephones) to the ONU and use VoIP (Voice over IP) technology to conduct voice communication over the internet.

Overall, the presence of POTS ports makes the ONU a comprehensive communication terminal that can provide high-speed internet access while also supporting traditional telephone services, thereby meeting the communication needs of different users.

the TEL port of OLTFigure 4: the TEL port of OLT

USB Port

The USB port meets diverse user needs by connecting various USB devices. Through the USB port, users can insert a USB flash drive containing upgrade files to perform offline software upgrades for the ONU device. Additionally, the USB port can be used for backing up and restoring the ONU's configuration files, facilitating maintenance and management. Moreover, in case of a failure in the primary fiber optic connection, the USB port can connect to a 4G or 5G USB modem to provide a backup internet connection, ensuring uninterrupted network access for home or enterprise users.

These functionalities make the ONU device more versatile and multifunctional, providing users with convenient network services and management solutions.

the USB port of OLTFigure 5: the USB port of OLT


The role of the CATV RF port on the ONU (Optical Network Unit) is to receive and transmit cable television signals, allowing users to enjoy high-definition television and high-speed internet services through the same device. Users can connect the CATV RF port to a television set or set-top box to achieve high-quality transmission of television signals and access multimedia content such as video-on-demand and interactive television.

The CATV RF port not only provides stable television signals but also integrates with other multimedia and internet services, offering an efficient and convenient comprehensive communication and entertainment solution for both home and enterprise users. This integration simplifies device management and provides convenient integrated services, particularly suitable for FTTH (Fiber-to-the-Home) and FTTB (Fiber-to-the-Building) environments.

the CATV RF port of OLTFigure 6: the CATV RF port of OLT


By configuring various types of ports, PON ONUs can flexibly address diverse access requirements, providing users with comprehensive network services. As an advanced solution provider, FS has been committed to delivering professional and reliable ONU products, catering to diverse user needs through flexible port configurations. Additionally, leveraging the full range of PON products and a dependable service team, FS is dedicated to offering comprehensive and flexible PON network solutions. For more information, please visit the FS PON Network.

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