What Is ONU Device ONU Working ONU Functions ONT FTTH



FTTH is a technology in which we deliver Data, Voice and video services to customer on the fiber network. So it is known as Fiber To The Home.  OLT , ONU, EDFA and Splitters are the main devices which we implement in our Headend or Central Office to deliver FTTH Triple play services to our subscribers.

So in this article we will cover ONU Device.

What Is ONU


ONU stands for Optical Network Unit. Sometimes it also known as ONT. ONT represents Optical Network Terminal. But there is no any major difference between ONU and ONT. Because ONT is term by IEEE while ONU is term by ITU-T.

So ONU is a small electronic device which is used in GPON (Gigabit Passive Optical Network) system. One side of ONU is connected with the PON (Passive Optical Network) while other side is connected with coaxial and Ethernet cable. Thus ONU have one optical port, coaxial port and RJ45 ports. One thing which we need to keep in mind here is that there are various kind of ONUs are available in the market. Some of them deliver only voice and internet while others deliver CATV, voice and internet.

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Working Of Optical Network Unit

A ONU is used to transform the optical signal into the electrical signals. So these electrical signals are sent to the subscribers to deliver the voice. Internet and video services

ONU perform the function of grooming. In this function ONU gets the data from the different subscribers and then reorganise this data. After doing this process the data is sent to the OLT in a more efficient way.

There are different kind of ONTs available which provides different interfaces like,

Digital Video

Analog Video

Ethernet Port

ATM Interface

Thus interfaces are available according to the need of customer.

ONU is a device mounted outside the customer house. It can be mounted in a section of building.  ONU should be designed like that it can handle temperature difference and as much as possible water resist too.

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ONU Closure

ONU closure is a box in which different ONUs are placed. This closure provides the protection to ONUs from environment.  It also provides the mechanical protection to ONUs and fiber cables.


ONU is a device used in GPON system to deliver the triple play services to subscribers like voice, broadband and catv also it upstream the data information from subscribers to OLT device which is installed in Central Office. via Passive Optical Network. So it plays an important role in GPON system. Optical Network Unit have various interfaces based upon need of subscribers.

Know More About What Is OLT

image credit: genewtech

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