What is ONU?

ONU is Optical Network Unit optical network unit. The ONU has two functions: it selectively receives the broadcast sent by the OLT, and if it needs to receive the data, it needs to respond to the OLT; it collects and caches the Ethernet data that the user needs to send, and sends it to the OLT according to the allocated sending window. Send the cached data.

The access methods of ONUs in different deployments of FTTx networks are also different. For example, FTTC (Fiber To The Curb): the ONU is placed in the central computer room of the community; FTTB (Fiber To The Building): the ONU is placed in the junction box of the corridor; FTTH (Fiber To The Building) To The Home): The ONU is placed in the home user.

ONU equipment consists of core functional circuits, common units such as power supply and management, and communication interfaces. The core functional blocks of the ONU include user and service multiplexing functions, transmission multiplexing functions, and ODN interface functions.

The user and service multiplexing function includes assembling information from each user, distributing the information to be transmitted to each user, and connecting a single service interface function; the transmission multiplexing function includes analyzing the signal from the ODN and extracting the part belonging to the ONU and reasonable The information to be sent to the ODN is arranged locally; the ODN interface function provides a series of optical physical interface functions, including optical/electrical and electrical/optical conversion.

If each ONU uses more than one fiber to connect to the ODN, then there is more than one physical interface. The ONU service function block provides user-side functions.

It includes providing user service interface and adapting user information to the form of 64kbit/s or n×64kbit/s; this function block can serve one or several users, and can provide signaling conversion function according to its physical interface.

ONU general function block provides power supply function and system operation, management and maintenance (OAM) function. The power supply function includes AC to DC or DC to AC. The power supply mode is local power supply or remote power supply. Several ONUs can share a power supply, and the ONU should work normally when powered by a backup power supply.