A Fiber Optic Termination Box is a small enclosure located at the terminal end of the fiber where it enters your customer premises. Serving. It is used in a terminal box to connect the optical fibers in the optical cable, and to connect the optical cable and the jumper through the terminal box coupler (adapter). Through termination box couplers (adapters), pigtails and patch cords are connected. A typical PON topology (GPON, XGS-PON, or 25G PON) flows OLT → fiber distribution hub → passive splitters → distribution/drop fibers → premises.