This small box is a fiber termination box. It is an end point of the optical cable extending to the user's home. The. What is a Fiber Optic Termination Box? A Fiber Optic Termination Box is a small enclosure located at the terminal end of the fiber where it enters your customer premises. Its function is primarily to splice, secure, and protect the optical fibers connecting the incoming drop cable to the pigtail or. To address these issues, the fiber termination box (FTB) — also known as the optical termination box or fiber distribution box — plays a crucial role in ensuring safe, structured, and efficient fiber connectivity at the network edge. As an important node in fiber optic access networks (such as FTTH) and backbone networks, it ensures efficient transmission.