Optical Network Unit
Encyclopedia
An optical network unit is a device that transforms incoming optical signals into electronics
at a customer's premises in order to provide telecommunications services over an optical fiber
network.
(PON) protocol, and adapts PON PDUs
to subscriber service interfaces. In some contexts, an ONU implies a multiple subscriber device. An optical network terminal (ONT) is a special case of an ONU that serves a single subscriber.
.
An ONU is used in combination with an optical line terminal (OLT).
An ONU system consists of a closure that is a metallic or non-metallic enclosure that provides physical and environmental protection for the active electronic, optoelectronics, and passive optical components it houses. It terminates optical fibers from the ODN and processes the signals to and from the Customer Premises Equipment (CPE). It is the NE that provides the tariffed telecommunications as well as video service interfaces for multiple residential and small business customers.
Services on the customer side of the ONU are communicated over metallic twisted pairs and coaxial cable drops (in the future, possibly fiber cable or wireless) to a Network Interface (NI) where they are handed off to the customer’s network (usually, inside wiring). Depending on the deployment strategy, the ONU closure may provide one or more of the following additional features:
Primary power for ONUs is derived from either an external DC or an external AC power source. Back-up power for ONUs can either be derived from an external power source or be internal to the ONU closure and be provided by the FITL system supplier. Primary power and external back-up power can be delivered to ONUs over either copper twisted pairs or coaxial cable facilities. These cable facilities are commonly referred to as the TSC.
Deployment of an ONU system requires access to the fiber distribution cable, TSC, and metallic customer drop wires. When access to these cables is provided internal to the ONU closure (i.e., by looping each cable through the closure), it is necessary that the ONU closure also provide splicing and storage facilities for each of these cables.
Telcordia GR-950, Generic Requirements for Optical Network Unit (ONU) Closures and ONU Systems, contains complete proposed specifications for the ONU closures and systems.
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
at a customer's premises in order to provide telecommunications services over an optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
network.
Definition
An ONU is a generic term denoting a device that terminates any one of the endpoints of a fiber to the premises network, implements a passive optical networkPassive optical network
A passive optical network is a point-to-multipoint, fiber to the premises network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises, typically 16-128. A PON consists of an optical line terminal at the service provider's central...
(PON) protocol, and adapts PON PDUs
Protocol data unit
In telecommunications, the term protocol data unit has the following meanings:#Information that is delivered as a unit among peer entities of a network and that may contain control information, address information, or data....
to subscriber service interfaces. In some contexts, an ONU implies a multiple subscriber device. An optical network terminal (ONT) is a special case of an ONU that serves a single subscriber.
Usage
ONU provides the subscribers with broadband Internet accessBroadband Internet access
Broadband Internet access, often shortened to just "broadband", is a high data rate, low-latency connection to the Internet— typically contrasted with dial-up access using a 56 kbit/s modem or satellite Internet with inherently high latency....
.
An ONU is used in combination with an optical line terminal (OLT).
Optical Network Unit (ONU) Closure
An ONU closure is a mechanical compartment that houses the ONU equipment. The outer closure faces the outside environment and provides physical, mechanical, and environmental protection for cable (fiber and copper) components or equipment housed within it.An ONU system consists of a closure that is a metallic or non-metallic enclosure that provides physical and environmental protection for the active electronic, optoelectronics, and passive optical components it houses. It terminates optical fibers from the ODN and processes the signals to and from the Customer Premises Equipment (CPE). It is the NE that provides the tariffed telecommunications as well as video service interfaces for multiple residential and small business customers.
Services on the customer side of the ONU are communicated over metallic twisted pairs and coaxial cable drops (in the future, possibly fiber cable or wireless) to a Network Interface (NI) where they are handed off to the customer’s network (usually, inside wiring). Depending on the deployment strategy, the ONU closure may provide one or more of the following additional features:
- Access to the fiber distribution cable
- Management of slack fiber and fiber splices
- Access to the Telephone Support Cable (TSC) for the purpose of powering the ONU
- Prevention of unauthorized entry.
Primary power for ONUs is derived from either an external DC or an external AC power source. Back-up power for ONUs can either be derived from an external power source or be internal to the ONU closure and be provided by the FITL system supplier. Primary power and external back-up power can be delivered to ONUs over either copper twisted pairs or coaxial cable facilities. These cable facilities are commonly referred to as the TSC.
Deployment of an ONU system requires access to the fiber distribution cable, TSC, and metallic customer drop wires. When access to these cables is provided internal to the ONU closure (i.e., by looping each cable through the closure), it is necessary that the ONU closure also provide splicing and storage facilities for each of these cables.
Telcordia GR-950, Generic Requirements for Optical Network Unit (ONU) Closures and ONU Systems, contains complete proposed specifications for the ONU closures and systems.