It is called fiber optic splice closure, or fiber splicing closure. 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. They come in various types like SC, LC, ST, and MTP, each designed for specific. It is of high mechanical strength, good sealing, anti corrosion by the electrified alloy shell, with sealing of sealant ring and silica gel.