Fiber optic closure is a device used to connect and protect optical fibers, providing optical cables with functions such as wiring, fusion, fiber storage, and protection. Fiber optic splice closures have been widely used in various fields such as communication, network systems . Fiber optic closures protect and organize cable splices, ensuring long-term stability in both outdoor and indoor networks. It can provide protection for. This guide is written to provide a complete and engineering-oriented understanding of fiber optic splice closures—from basic concepts and classifications to structural logic and practical deployment considerations.