What is an ONT and what is it for in your fiber connection

If your operator installs the router and you don’t worry about it and don’t change it again, it’s possible that you haven’t even wondered what an ONT is, why there are two devices in some installations or which is which. But it is convenient that we know what an ONT is, how it differs from the router, what we must take into account when changing it or why it must be compatible. Interesting concepts related to your fiber installation and that you should know, even in a basic way.

It is becoming more and more common that there is only one device in your fiber installation compared to the two that we found before, but it is important that you know how to differentiate the router from the ONT or that you know what it is for, what its mission is and why its importance.

What is ONT?

ONT stands for Optical Network Terminal. In other words, the ONT is in charge of converting the optical signal of the fiber cable into a digital signal, allowing it to be sent through Ethernet cables or via wireless from your router to connect via WiFi. The ONT converts the signal which is then interpreted by the router. It is a device that connects the fiber optic cable of your installation, it is the device that connects your home network with the operator and then gives the connection to the router that will be in charge of distributing it.

There are also other concepts that are related and that we must know, such as CTO. CTO is a device that is responsible for aggregating all the optical signals of an ONT. CTO is the optical terminal box that is usually installed on the outside of the building and where the fibers of the outdoor network are connected to the homes. They are generally boxes that are placed on the façade and that function as a sharing point if there are many neighbors in a building, for example.

ONT distribution
ONT Distribution

That is, a device placed outside your building or your home and that is responsible for “gathering” the signal of several clients to the operator. Interconnect different equipment using the GPON design that you can see in the image below and with an ONT for each neighbor, user, client.

In most cases the ONT is part of the router you have, it is not different and it is inside the same device. But not always. Other times, no. For example, in neutral routers or routers that you buy voluntarily (not those from operators) we do not usually have the integrated ONT and this second device needs to exist. Some operators have also had two devices for years, although it is less and less common and today it is normal for it to be integrated into it. In cases where it is not included, you will see that there are two devices or devices in your installation and that one and the other are connected through an Ethernet cable and both connected to the current. Both must be connected to each other and connected to the light.

How do we know what is the router and the ONT?

It’s simple. Both are devices with an Ethernet cable and connected to the current, but they are totally different in terms of switches on the back and generally in the lights that we can see on or off. The ONT generally has one LAN port, one port for optical cable, and one port for power connection. And nothing more. Also, less LED indicator lights: we will usually see the power on and off, PON, LOS and LAN.

Router with ONT

They are smaller and simpler devices or devices but the main difference will be the fiber optic cable that connects to one and not the other. The fiber optic cable will go from the wall outlet to the ONT. An Ethernet cable runs from the ONT to the router. And it’s easy to tell the difference between the two, so we won’t have any problem knowing which is which when we have a connection error and follow the technician’s instructions. In case we have only one device we will see that it is connected directly to the router, as is logical.

Which is better: router with ONT or without ONT?

Is a router that has the ONT incorporated or that does not have it better? Most operator routers already integrate the ONT, although for a time it was common for us to have two devices and many people were not clear why one or the other. Both, as we have explained before, connected with an Ethernet cable.

The fact that the ONT is integrated into the router allows us to have two devices connected to the current instead of one, with the advantage that this entails at the level of space, but also at the level of energy consumption or at the level of cables in the same small space, to have everything organized. It can also lead to confusion in users who do not understand the subject correctly and have a problem with the router, although they are easy to differentiate with the instructions of a technician.

Router with ONT

But not having an integrated ONT also has advantages : we will not be able to use the router we want as the main unit without our network connection going through the operator’s router. If we buy a neutral router without ONT we need an ONT. If it is external, simply remove the one we have and connect the ONT to the new one. But if it is inside the operator’s apparatus it is usually something more complicated. Although generally we will not have any problem if we convert the operator’s router as an ONT simply with the mission of converting the signal. And an independent router as the main router, connected to the first one and fulfilling its function.

Of course, we must take into account a series of aspects when changing the router. If you do not use the ONT of your operator, you cannot identify yourself unless we get the SIP and GPON keys from it, something that is not always easy. That is why the most appropriate thing is that we use the ONT that it already offers regardless of whether you use a neutral router connected to it.

So which one is better? Generally, it is more recommended that a router already have the ONT integrated and this is what the main operators do with the most recent models, with sufficient performance for most users and without the need to buy a new router in the vast majority of cases.

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