Optical line termination
Encyclopedia
An optical line termination (OLT), also called an optical line terminal, is a device which serves as the service provider endpoint of a passive optical network
. It provides two main functions:
Passive 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...
. It provides two main functions:
- to perform conversion between the electrical signals used by the service provider's equipment and the fiber optic signals used by the passive optical network.
- to coordinate the multiplexingMultiplexingThe multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
between the conversion devices on the other end of that network (called either optical network terminals or optical network unitOptical Network UnitAn 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.-Definition:...
s).
Features
OLTs include the following features:- A downstream frame processing means for receiving and churning an asynchronous transfer modeAsynchronous Transfer ModeAsynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
cell to generate a downstream frame, and converting a parallel data of the downstream frame into a serial data thereof. - A wavelength division multiplexing means for performing an electro/optical conversion of the serial data of the downstream frame and performing a wavelength division multiplexing thereof.
- A upstream frame processing means for extracting data from the wavelength division multiplexing means, searching an overhead field, delineating a slot boundary, and processing a physical layer operations administration and maintenance (PLOAM) cell and a divided slot separately.
- A control signal generation means for performing a media access controlMedia Access ControlThe media access control data communication protocol sub-layer, also known as the medium access control, is a sublayer of the data link layer specified in the seven-layer OSI model , and in the four-layer TCP/IP model...
(MAC) protocol and generating variables and timing signals used for the downstream frame processing means and the upstream frame processing means. - A control means for controlling the downstream frame processing means and the upstream frame processing means by using the variables and the timing signals from the control signal generation means.