An Optical Network Unit (ONU) is a critical device used in fiber optic networks, particularly in Fiber to the Home (FTTH) and other Fiber-to-the-x (FTTx) architectures. It serves as the interface between the end-user’s premises and the Passive Optical Network (PON).
- Definition and Function
Conversion of Signals: The ONU converts optical signals transmitted over the fiber optic cable into electrical signals that can be used by the customer’s equipment, such as routers, computers, telephones, and television set-top boxes. It also converts electrical signals from the customer’s equipment back into optical signals for transmission to the Optical Line Terminal (OLT) at the service provider’s central office.
Data Transmission: The ONU receives data from the OLT and selectively processes it. It collects and buffers Ethernet data from the user and sends it to the OLT according to the allocated transmission window.
Triple-Play Services: ONUs support “triple-play” services, which include data, IPTV (interactive network television), and voice services (using Integrated Access Devices, IAD).
- Types of ONUs
Active ONU: Equipped with network monitoring capabilities, optical receivers, upstream optical transmitters, and multiple bridge amplifiers. Active ONUs are used in environments requiring high-quality VOIP audio, routing, and wireless access.
Passive ONU: Used in Gigabit Passive Optical Network (GPON) systems, passive ONUs terminate traffic from the OLT and provide broadband services such as internet, VoIP, and HDTV to users.
Features of ONU
Interfaces: ONUs typically have various interfaces, including network ports (RJ45), optical ports (SC/UPC or SC/APC), telephone ports (RJ11), TV ports (IPTV and CATV), and USB ports. Some ONUs also support Wi-Fi connectivity.
Remote Management: ONUs offer advanced remote management capabilities, including support for Operations, Administration, and Maintenance (OAM) functions.
High Sensitivity and Low Power Consumption: ONUs are designed to have high sensitivity for light reception and low optical power consumption, ensuring efficient operation.
- Usage Scenarios
Single-Family Unit (SFU) / Single-Business Unit (SBU): These ONUs connect to a single user and provide Ethernet and POTS interfaces for narrowband voice services.
Home Gateway Unit (HGU): Used in FTTH scenarios, HGUs provide multiple Ethernet interfaces, WLAN, and USB interfaces.
Multi-Dwelling Unit (MDU) / Multi-Tenant Unit (MTU): These ONUs serve multiple users in a building or complex, offering numerous Ethernet or DSL interfaces and POTS interfaces for voice services.
In a word, an ONU is a versatile and essential device in fiber optic networks, enabling high-speed broadband connectivity and supporting a range of services and applications.
Post time: Jun-07-2024