An optical line terminal, abbreviated as OLT, is a virtual end-point device that can be connected to the front-end (transmission convergence layer) switch with a network cable and can be converted into optical signals. It is also interconnected with the splitter at the user’s end with a single optical fiber to achieve the control, management, and range of the user’s end equipment ONU.
The function of OLT
The passive optical network (PON) is composed of an optical line terminal (OLT) at the service’s central hub and optical network units (ONUs) or optical network terminals (ONTs) at the users’ side. OLT plays an essential role in PON in FTTx.
- The OLT is connected to a cable switch at the coverage level and converted to an optical signal.
- The OLT connects to the optical splitter on the customer terminal via optical fiber and coordinates the conversion device on ONTs at the customers’ premises.
- It controls, manages, and measures the distance to customer terminal equipment, e.g., ONUs.
- It is one of the devices to connect to the access network. It can achieve service access through the SNI port.
- The OLT helps control the flow of both upstream and downstream data.
The composition of OLT
The OLT hardware usually consists of three major parts: backplane, main control board, and single boards. The backplane is mainly used to connect multiple OLT single boards and the main control board. In general, an OLT is designed in the form of 4 single boards, which means 4 ports or 20 single boards (i.e. 20 PON ports).
The advantage of OLT
- The OLT allows users to manage everything on the network. With OLT, users can easily configure the terminal equipment like ONU so that ONU can also be easy to manage.
- Users can also pass VLAN to ONU via OLT, and they will finally get a secure network.
Types of OLT
As the passive optical network can be divided into APON, BPON, EPON, and GPON. OLT can also be classified into APON OLT, BPON, OLT, EPON OLT, and GPON OLT. In general, EPON OLT and GPON OLT are more common than the former two OLTs.
EPON OLT is a multi-service provider endpoint that can support both IP and TDM services.
So, how many ports are in EPON OLT? There are OLT EPON 4 pon, 8 pon EPON OLT, and EPON OLT 16 pon on the market. These OLTs are flexible, convenient, and easy to deploy, popular for many scenarios.
GPON OLT has two flow directions: upstream and downstream. It can control the data of ODN in both directions.
In general, GPON OLT is usually divided into the following types according to different ports: GPON OLT 4 port, GPON OLT 8 port, MINI OLT GPON, and 16 port GPON OLT. Each OLT port can be connected to up to128 ONUs.
The application of OLT
Combined with different ONUs, OLT devices can be applied in various access networks in FTTx scenarios. It will be deployed according to different services and users’ needs.
