What’s the Difference Between ONU and ONT?

Many users may have the question: are ONU and ONT the same thing? So, do you know the difference between ONU and ONT? ONU means Optical Network Unit, and ONT represents Optical Network Terminal. ONT and ONU can be regarded as connecting with the users’ side. But in different FTTX applications, ONT and ONU are a bit different.


Before knowing the difference between ONU and ONT, you should understand what ONU and ONT are.


Concept of ONU and ONT


ONU means Optical Network Unit, and ONT represents Optical Network Unit. They refer to users’ side equipment in FTTH communication links. ONT is an ITU-T terminology, whereas ONU is an IEEE term.


In general, ONU&ONT has different ports, including the PON port, network port, CATV port, audio port, and WIFI port. PON port is used to receive data from OLT, the network port is connected with the terminal equipment such as TV and router, and the wifi port is connected with the terminal devices such as computers and phones.


Difference Between ONU and ONT


ONU and ONT can be a bit different in different FTTX scenarios, but before knowing the difference, you should be familiar with some technical terms.


  • FTTH: Fiber to the home, also called FTTP (fiber to the premises), is the usage of optical fiber from a central location directly to individual buildings, including households and apartments.
  • FTTB: Fiber to the building is an access network that uses a mix of fiber. The fiber cable goes from a point to the entry of buildings, homes, offices, or other spaces.


It is known to all that PON consists of OLT (Optical Line Terminal), ONU (Optical Network Unit), and ODN (Optical Distribution Network).




In FTTH, ONU is an optical device connected with ODN. ONT is linked to the users’ side.


A fiber-optic modem will be installed when the fiber comes to the home. The optical cat is connected to both ODN and the users’ end, so at this time, ONU and ONT can be the same thing.




In FTTB, ONU is located outside the residence, and the device linked with ODN cannot be connected to the users’ side. So ONU is different from ONT.


When the fiber enters the home, ONU can be connected to many network cables, and users are connected to the ONU through a switch and other devices. At this time, ONU may have many ONTs, so they are slightly different.




In conclusion, an ONU transforms optical signals into electric signals through a fiber cable and handles different data to send them to OLT; an ONT is just a box directly connected to TVs, computers, or phones.


ONT is located on the users’ side, and there may be other networks when ONU finally reaches the users’ end.


You can regard an ONT as an ONU with one port to make it easier to understand.


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