ONT (Optical Network Terminal) and ONU (Optical Network Unit) are both devices used in fiber-optic communication networks, particularly in the context of passive optical networks (PONs). While they share similar functions, there is a distinction between the two: 

1. ONT (Optical Network Terminal):

• Location: ONT is typically located at the customer's premises, such as a home or business.

• Function: The ONT is responsible for terminating the optical signal from the service provider's network and converting it into electrical signals that can be used by customer premises equipment (CPE) like routers, computers, and other network devices.

• Interfaces: ONTs often provide various interfaces, such as Ethernet ports, voice ports (for VoIP), and other connectivity options for delivering broadband services.

2. ONU (Optical Network Unit):

• Location: ONU is a more generic term and can refer to a device located at various points in the network, including both customer premises and distribution points in the network.

• Function: Similar to ONT, ONU is responsible for terminating the optical signal and converting it into electrical signals. It can serve various roles, including connecting to multiple customer premises or serving as an aggregation point for multiple ONUs.

• Interfaces: The interfaces provided by an ONU can vary based on its specific role. ONUs serving multiple customers may have multiple user ports and uplink ports to connect to higher-level aggregation nodes in the network.

In summary, while ONT specifically refers to the device located at the customer's premises, ONU is a more general term that can refer to optical network units at different locations within the overall network architecture, including customer premises and distribution points. Both ONT and ONU play crucial roles in the deployment of PONs and the delivery of fiber-optic-based broadband services to end-users.