As light travels through the glass core of an optical fiber and is absorbed by the cladding as it passes through, this causes varying amounts of attenuation in the fiber optic cable. Light can also be scattered by fibers, causing it to be diffused before reaching its. In short, the terminal box is the last structured node of the Fiber Optic System before service touches the subscriber. A typical PON topology (GPON, XGS-PON, or 25G PON) flows OLT → fiber distribution hub → passive splitters → distribution/drop fibers → premises. It's measured in decibels per kilometer (dB/km), and it determines how far a signal can travel before it becomes too weak to read. Understanding it is crucial for anyone involved in data centers, telecommunications, or enterprise networking. Attenuation refers to the loss of light as it travels down the fiber.