What are the differences in the roles of industrial grade ONUs and OLTs?

Optical Access Network (OAN) refers to the use of optical fibers as the main transmission medium to achieve the information transmission function of the access network. Connected to business nodes through optical line terminals (OLT) and connected to users through optical network units (industrial grade ONUs). Fiber optic access, the network includes remote devices – optical network units and local devices – optical line terminals, which are connected through transmission equipment. The main components of the system are OLT and remote industrial grade ONU. They complete the conversion of signaling protocols from Service Node Interface (SNI) to User Network Interface (UNI) throughout the entire access network. The access device itself also has networking capabilities and can form various forms of network topology structures. At the same time, the access device also has local maintenance and remote centralized monitoring functions, forming a maintenance and management network through transparent optical transmission, and incorporating it into the unified management of the network management center through corresponding network management protocols.

The role of OLT is to provide an interface between the access network and the local switch, and to communicate with the optical network unit of the user end through optical transmission. It completely separates the switching function of the switch from user access. The optical line terminal provides maintenance and monitoring for itself and the user end. It can be placed directly with the local switch at the exchange end or set up at the remote end.

The function of that industrial grade ONU is to provide user side interfaces for access networks. It can connect to various user terminals and has photoelectric conversion function as well as corresponding maintenance and monitoring functions. The main function of ONU is to terminate optical fibers from OLT, process optical signals, and provide business interfaces for multiple small businesses, business users, and residential users. The network end of an industrial grade ONU is an optical interface, while its user end is an electrical interface. Therefore, ONU has optical/electrical and electrical/optical conversion functions. It also has digital/analog and analog-to-digital conversion functions for dialogue sounds. ONU is usually placed close to the user, and its location has great flexibility.

OAN is divided into two categories based on system allocation: active optical network (AON) and passive optical network (PON).