Also called fiber optic splice closures, these little boxes provide a protected area for the spliced sections to live, keeping them away from any hazards. Some of the dangers that face the fibers include pressure, extreme temperatures, insects and moisture. These closures provide both mechanical protection and environmental sealing, ensuring that spliced fibers are not affected by moisture. For protection against the outside plant environment and damage, splices require placement in a protective enclosure, usually called a splice closure. Along transmission routes—whether in access networks, metro networks, or backbone infrastructure—fiber cables must be joined, branched, repaired, or reserved for future expansion. But every one of. In any fiber optic network, the long-term reliability of signal transmission depends heavily on the integrity of its most vulnerable points: the splices. A Fiber Optic Closure, often referred to as a joint closure or splice enclosure, is an essential passive device engineered to protect these. A FOSC is a protective enclosure designed to house, organize, and environmentally seal optical fiber splices, providing mechanical protection, water resistance, and easy re-entry for maintenance.