OLT, ONU,ODN,ONT,EPON,GEPON and PON

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Optical Line Terminal (OLT)

OLT (Optical Line Terminal) is the endpoint hardware device located at the central office in a Passive Optical Network (PON). The OLT contains a central processing unit, a gateway router, voice gateway uplink cards and passive optical network cards. The main functionality of the OLT is to adapt the incoming traffic (voice/data/video) from the metropolitan rings into the PON transport layer. It can transmit a data signal to users at 1490nm wavelength. That signal can serve up to 128 ONTs at a range of up to 12.5 miles by using Optical Splitters.

Functions

OLT is generally employed for terminal connected to the fiber backbone. An OLT has two primary functions:

  • Converting the standard signals use by a FiOS service provider to the frequency and framing used by the PON system;
  • Coordinating the multiplexing between the conversion devices on the optical network terminals (OLTs) located on the customers’ premises.

Optical Network Unit (ONU)

ONU converts optical signals transmitted via fiber to electrical signals. These electrical signals are then sent to individual subscribers. In general, there is a distance or other access network between ONU and end user’s premises. Furthermore, ONU can send, aggregate and groom different types of data coming from customer and send it upstream to the OLT. Grooming is the process that optimises and reorganises the data stream so it would be delivered more efficient. OLT supports bandwidth allocation that allows to make smooth delivery of data float to the OLT, that usually arrives in bursts from customer. ONU could be connected by various methods and cable types, like twisted-pair copper wire, coaxial cable, optical fiber or Wi-Fi.

Optical Network Terminal (ONT)

ONU converts optical signals transmitted via fiber to electrical signals. These electrical signals are then sent to individual subscribers. In general, there is a distance or other access network between ONU and end user’s premises. Furthermore, ONU can send, aggregate and groom different types of data coming from customer and send it upstream to the OLT. Grooming is the process that optimises and reorganises the data stream so it would be delivered more efficient. OLT supports bandwidth allocation that allows to make smooth delivery of data float to the OLT, that usually arrives in bursts from customer. ONU could be connected by various methods and cable types, like twisted-pair copper wire, coaxial cable, optical fiber or Wi-Fi.

Published by Zahid Hossain