An Outdoor Optical Line Terminal (OLT) is a key component in fiber-optic communication networks, particularly in Fiber-to-the-Home (FTTH) or Fiber-to-the-Building (FTTB) deployments.
Then the uplink data is the data sent from the PON system to the uplink equipment such as Layer 3 switches, routers or BRAS, and the downlink data is the data sent from the PON system to the downstream user-side equipment.
A Small Capacity OLT shares fundamental functionality with larger OLTs but is designed for deployment in scenarios with lower subscriber density or where scalability demands are not as high.