Differences between ONT and ONU, HGU and SFU

When it comes to user-side devices in FTTx and PON technology, we always see or hear of words of ONT ONU SFU and HGU, what does these words mean and what are the differences? You will get the answer and be clear after reading below article.

To begin with, we want to briefly introduce PON (Passive Optical Network). PON is a kind of single-fiber bidirectional optical access network with a point to multi-point (P2MP) structure with a typical tree-type topology. The system composed of OLT (Optical Line Terminal), ONU (Optical Network Unit) and ONT (Optical Network Terminal), and ODN (Optical Distribution Network) which provides a transmission channel, is what we call the PON system.

ONT and ONU

In the application of optical access, mainly are FTTH, FTTO and FTTB, there are different user-side devices in different applications. It is single user at user-side in FTTH and FTTO, which is ONT; and it is multi-user sharing in FTTB, which is ONU.

1, ONT Type

ONT also be called optical modem, can be classified into SFU (Single family unit) and HGU (Home gateway unit) and SBU (Single business unit)

1.1 SFU

SFU ONT only supports the OMCI management domain. PPTP is what SFU uses and reports, while VEIP is not available. The processing mode of OMCI configured data flow is different from that of RG flow. For OMCI data flow, there is a one-to-one mapping between the GEM port on the WAN side and the UNI port on the LAN side. All data packets can pass through without MAC address learning or forwarding. Wireless interfaces are not allowed in OMCI.

SFU ONT was used in early time, since weak remote management function, now are rare used.

1.2, HGU

HGU ONT, a home gateway with an uplink interface of the PON, is designed for the single family unit, which is similar to SFU ONT. Compared to SFU ONT, HGU ONT integrates below advantages:

• HGU ONT like Huawei EG8145V5 or EG8141A5, belongs to gateway device for family inner network, while SFU is a transparent device, no gateway function, normally it needs work with a router.

• HGU ONT is a Layer 3 device, supports routing mode and NAT; SFU is a layer 2 device, same as a L2 switch.
• TR-069 remote management and EMS local and remote management of physical layer and link layer related to PON interface are supported by HGU ONT
• HGU ONT are easier for large-scale operation and maintenance management

HGU and SFU ONT function comparison

ONT Type	SFU	HGU
Bridging/Routing	Bridging/L2	Bridging/Routing/L3
WAN configuration	Not support	Support
TR069	Not support	Support
NAT	Not support	Support
WiFi	Not support	Support

1.3, SBU

SBU ONT mainly used in FTTO access, with Ethernet port, some are with E1, fixed POTS or with WiFi. Compare to SFU and HGU, SBU ONT has better electrical protection, higher stability, commonly applied to outdoor environment, such as video surveillance and other occasions.

2. ONU types

ONU includes MDU ONU MDU (Multi-DwellingUnit) MTU (Multi-TenantUnit).

MDU is used to connect multiple residential users in FTTB mode, and it provides at least four user-side ports, and 8/16 and 24 FE or FE+POTS ports, such as Huawei MA5626.

MTU is used to connect multiple enterprise users or terminals in the same enterprise in FTTB. In addition to Ethernet ports, fixed POTS ports, maybe also E1 interfaces. MTU has better electrical protection performance and higher stability.  With the popularity of FTTO, the application of MTU is less and less.

Conclusion:

Broadband optical access mainly uses PON technology. The user-side devices in a PON system can be collectively called ONU if the specific forms of user-side devices are not identified. Below picture may make you understand it more clearly.