What is ONU?

ONU, or optical network unit, is a terminal device in a fiber-optic access network that can provide users with a variety of service interfaces. The network side of ONU is connected to the fiber-optic interface, and the user side is connected to the electrical interface, so it can achieve bidirectional conversion between optical and electrical signals. In addition, ONU can also complete tasks such as analog-to-digital conversion (D/A and A/D) of voice signals, signal multiplexing and processing, and equipment management and maintenance.

Functional features of ONU

• Three-network integration support: providing data, IPTV (interactive network television), VOIP (voice communication through integrated access equipment) and other services.
• Downlink broadcast data reception: receiving broadcast data sent by OLT (optical line terminal).
• Data caching and sending: collecting and caching Ethernet data that users need to send, and sending it to OLT according to the allocated sending time slot.
• Rich remote management capabilities: supporting OAM (operation and maintenance) functions, providing efficient remote management capabilities.

Advantages of ONU

• High-speed connection: efficiently converting optical signals in the fiber-optic network into electrical signals, providing ultra-fast Internet access for terminal devices.
• Scalability: Supports a variety of deployment scenarios from single homes to multi-user buildings, suitable for network needs of different sizes.
• Cost-effective: By terminating the fiber connection at the user end, the need for additional infrastructure is reduced, thereby reducing the cost of service providers and users.
• Flexibility: Compatible with a variety of FTTx architectures (such as FTTH, FTTB, etc.) to meet diverse deployment needs.
• Improved network efficiency: Improve overall network efficiency through two-way data transmission and stable signal quality management.
• User experience optimization: Provides low-latency, stable connections, especially suitable for high-bandwidth applications such as video streaming, online games and remote office.

Types of ONU

Depending on the specific application scenario, ONU can usually be divided into the following categories:

• SFU (user-oriented terminal unit): Provides basic network connection for a single home or office.
• HGU (home gateway unit): Integrated routing, WiFi and other multi-functional devices, suitable for home network use.
• SBU (service boundary unit): Serves as a demarcation point between the service provider network and the user end, mostly used in FTTH (fiber to the home) deployment.
• MDU (Multi-Dwelling Unit): Provides shared network access for multi-user environments such as apartment buildings and office buildings.
• MTU (Maximum Transmission Unit): Refers to a specific limit on the size of data packets in the network to ensure efficient data transmission.
• Depending on the actual environment, such as a single family, a multi-user building, or the need to optimize data performance, the appropriate ONU device type can be selected.

Position of ONU in FTTx architecture

According to the different positions of ONU in the fiber access network, FTTx access methods can be divided into the following categories:

• FTTC (Fiber to the Curb): ONU is placed in the central computer room of the community.
• FTTB (Fiber to the Building): ONU is set in the wiring box in the corridor.
• FTTN (Fiber to the Node): ONU is located at the access point.
• FTTH (Fiber to the Home): ONU is installed in the house of the home user.