What is a ONT/ONU, and how does it work?
This is the first in a series of articles about ONU/ONT and PON technology. Check out our other post, " Do I need a router if I have an ONT/ONU?
What is ONT/ONU?
ONT is an interface between the Internet Service Provider (ISP) and the end user of fiber Internet. It’s an integral part of the fiber optic internet system because it converts optical signals into information your computing devices can digest. In other words, it works as a modem if you get your broadband Internet through Fiber to the Premises (FTTP).
Most of the time, homes and offices already have coax cables installed. In that case, a cable modem and router are the best fit. Otherwise, you must install expensive fiber cabling, ONT, and fiber routers to access an optical fiber internet connection.
ONT requires electrical power to operate and plugs directly into any existing AC electrical outlet in your facility. It converts incoming high-speed optical signals into electrical signals that your TV, telephone, and internet can comprehend.
What is the Difference Between ONT & ONU?
In FTTX network, some devices that are necessary to complete the fiber to the home (FTTH) link. One of which is the ONT/ONU. ONT refer as Optical Network Terminal. ONU refer as Optical Network Unit.
An ONT and an ONU is actually the same thing. ONT and ONU both refer to the consumer end equipment in an optical fiber to the home (FTTH) communication link. But if you want to get technical, there is one difference and that is that ONT is an ITU-T term, whereas ONU is an IEEE term. ITU-T and IEEE are two different telecommunication standards.
But you can think of an ONT and ONU as the same thing.
ONT and ONU
In the FTTX application, 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.
What is the purpose of an ONT/ONU?
On a FTTX network, the ONT/ONU is located at your premise (residential or commercial). The purpose of this device is to use optical fiber to connect to the passive optical network (PON) and communicate with your Internet service provider to get an Internet connection.
How an ONT/ONU works?
ONU converts optical signals transmitted via fibers to electrical signals. These electrical signals are then sent to individual subscribers. In general, there is a distance or other access network between ONU and end user's premises. Furthermore, ONU can send, aggregate, and groom different types of data coming from the customer and send it upstream to the OLT. Grooming is the process that optimizes and reorganizes the data stream so it would be delivered more efficiently. OLT supports bandwidth allocation that allows making smooth delivery of data float to the OLT, which usually arrives in bursts from the customer. ONU could be connected by various methods and cable types, like twisted-pair copper wire, coaxial cable, optical fiber, or through Wi-Fi.
What to Look for in an ONT/ONU?
GPON or EPON dual mode
4xGE+1x2.5GE+2VoIP+WiFi6 6000mbps+2USB
Fully compatible with IEEE 802.3AH Standard and ITU-U G.984
Supports a maximum transmission distance of 20KM
Dynamic bandwidth allocation (DBA) support
Supports automatic ONU discovery, remote software upgrade
Supports power dying gasp
Supports Telnet，WEB/CLI，OMCI/OAM，TR069 management mode
Support PPPoE/DHCP Server/IPTV/VoIP/NAT
Support 802.1Q vlan，Cos，Qos for priority of service
Supports Wi‐Fi 802.11n/ b/g/ac technology standards
Pots function support SIP protocol
Do I need a router if I have an ONT?
It depens on different application scenarios as below,:
1) In the FTTB application scenario, the PON system is connected to ONT of SFU (Single Family Unit) / Multi-Dwelling Unit (MDU) /Multi-Tenant Unit (MTU). The ONT (ONU) Ethernet port is required to connect to the router for dialing up to access network.
2) In FTTH and FTTO application scenarios. The PON system connects to the ONT of HGU (Home Gateway Unit) and SBU (Single Business Unit). HGU/SUB (ONU+ROUTE) is a gateway device and supports routing, NAT, and WIFI. The connected PC and mobile terminal can directly access the Internet through the HGU without dialing up. So it doesn't need to be connected to the router for dialing up to access the network.
Conclusion:
Broadband optical fiber access is mainly based on the PON technology. The devices on the user side of the PON system are collectively referred to as ONUs without the specific forms of the devices.
An ONT can be regarded as an Optical Network Unit (ONU), but it is strictly a part of the ONU. The difference between the two is that ONT is an optical network terminal designed to connect end users; An ONU is an optical network unit, and there may be other networks between ONU to the end user . For example, the ONU can coonect gateway devices such as xDSL or Ethernet switches, and then access the network user.
The ONT is usually located in the user's home and connects to various devices accessing network downward and to the Internet via optical fiber upwards.
