SFU, HGU, SBU, MDU, MTU: A Quick Guide to ONU/ONT Differences

In PON systems, there are many key terms and devices, such as SFU (Single Family Unit), HGU (Home Gateway Unit), SBU (Small Business Unit), MDU (Multiple Dwelling Unit), and MTU (Multiple Tenant Unit). Understanding the differences between these devices is crucial for selecting the right communication equipment. This article will detail the functions and differences of these devices to help you choose the most suitable fiber network deployment solution.

What are the Differences between ONU and ONT?

Before diving into the details of these devices, it's important to understand the basic equipment of PON networks:

• Optical Line Terminal (OLT): Installed on the service provider's side, it manages and configures terminal devices, converts signals, and broadcasts data.

• Optical Network Unit/Termination (ONU/ONT): Installed on the user’s side, it converts optical signals to electrical signals, distributes signals, and returns data.

Why are there two names for the network terminal devices? First, it is important to clarify that both ONU and ONT are devices connected to the fiber optic network. Second, in a network system, the device that provides network access to home computers, TVs, and telephones is known as a network termination (NT).

In a fiber optic network, if the NT is directly connected to the fiber optic cable, converting optical signals to electrical signals to provide network access to the home. This terminal box is known as Optical Network Termination (ONT). In this case, each user has an independent fiber optic channel for high-speed data transmission.

However, in another network system, the fiber optic cable does not directly enter the home but rather terminates in a hallway, unit, or other public area. Now, multiple users share a single fiber optic cable, and the network is delivered to each home through Ethernet cables. In this scenario, the optical network box serves not as a terminal but as an intermediate device. This box shifted from a single "termination" to a shared "unit," thus becoming an Optical Network Unit (ONU).

Therefore, the difference between the two lies in their position within the network architecture. When each household has an independent fiber optic channel, the network terminal device is an ONT. However, when multiple users in an area share a single fiber optic cable, the fiber optic box (ONU) acts as an intermediate device. The ONU "aggregates" the needs of users in high-bandwidth areas on a large scale, using fewer fiber optic resources to serve more users. This allows for low-cost deployment and easier maintenance of large-scale optical networks.

It should be noted that, as ONU and ONT functionalities become more integrated, many manufacturers no longer distinguish between the two. Customers can choose the appropriate ONU/ONT based on their specific needs.

5 Types of ONUs/ONTs: SFU, HGU, SBU, MDU and MTU

ONU/ONT devices can come in various types. According to the standard documents of China Telecom suppliers and the most common ONU/ONT application scenarios, they primarily include five types:

3 Types of ONTs for Single-Optical User

• SFU Type: Single Family Unit(SFU) is mainly used for individual household users. It functions as a broadband access terminal, providing Ethernet/IP services, with optional support for CATV services. It has 1 or 4 Ethernet interfaces and can optionally support a CATV RF port. It is primarily used in FTTH scenarios and can be paired with a home gateway to offer enhanced service capabilities.

• HGU Type: The Home Gateway Unit (HGU) is also intended for individual household users and functions as a home gateway. It is also known as a GPON uplink home gateway. It provides internet access, IPTV, and VoIP services, supports ITMS remote management, and allows EMS to manage the physical and link layers of the PON interface remotely. It can optionally support CATV services and is mainly used in FTTH scenarios. HGU-2 is also known as an AP external PON uplink home gateway.

• SBU Type: Primarily used for individual business users and single offices within a company, supporting broadband access terminal functions. It provides Ethernet/IP services and TDM services, with optional support for VoIP services (integrated IAD). It has Ethernet interfaces and E1 interfaces, with optional support for POTS ports. Mainly used in FTTO (Fiber to the Office) scenarios.

2 Types of ONUs for Multi-Optical User

• MDU Type: This is designed for multiple residential users, providing Ethernet/IP services with optional support for VoIP services (built-in IAD) or CATV services. It has multiple (at least 8) user-side broadband interfaces, including Ethernet, ADSL2+, or VDSL2 interfaces, and can optionally support POTS and CATV RF ports. It is mainly used in FTTB/FTTC/FTTCab scenarios.

• MTU Type: Primarily used for multiple business users or multiple individual users within the same company, providing Ethernet/IP services and TDM services. It optionally supports VoIP services (integrated IAD). It features multiple Ethernet interfaces (at least 8) and E1 interfaces, with optional support for POTS ports. Mainly used in FTTBiz (Fiber to the Business) scenarios.

FS ONUs Introduction

FS has developed a series of ONU/ONT devices that support GPON/EPON dual-mode automatic switching. The following is an introduction to the representative ONU/ONT devices of FS:

Summary

In summary, the difference between ONU and ONT lies in their positions within the network architecture. However, as the deployment of optical networks becomes more widespread, the functionalities of ONU devices have become increasingly comprehensive. Many suppliers no longer distinguish between ONU and ONT, referring to all-optical network terminals simply as ONU devices. Users can still select from SFU, HGU, SBU, MDU, and MTU devices based on their specific needs or deploy passive optical networks according to the interfaces and functionalities of different ONU devices.