Fiber Closure   devices are enclosures that contain and protect individual connectors in any fiber optic system, rather than fiber optic connections (splicing, joining, and mechanical splicing). Due to the fragility of the fiber and the potential need to upgrade the cable, quality enclosures are critical to a successful installation. But what is closed, what should you look for when choosing a seal? At its simplest, a closure connects a length of fiber optic cable to a cable of the same type of different length. This is sometimes referred to as an online closure or a track connection. The added functionality is provided by a branch (or branch) connector that divides the cable into two ongoing sections - the main cable and the side or branch cable. There is also the end of the path closure where the cable is broken down into separate components for customer or telecommunications connections. The earliest fiber closures were direct descendants of their copper cousins. The simplest structure (but not used!) is a wraparound heat shrink product that is usually only closed in the wire, but sometimes it is a branch joint. Although they are waterproof, they have little another benefit than low cost and often require skilled connections to apply them. With the widespread adoption of blown fiber and cable systems using multiple microtubule bundles, tube dispensing closures have become commonplace. As the name implies, these can create an online mini-track joint or, more commonly, branch each microtube to a different destination. Instead of the fiber connections occurring in the closure, the individual microtubes are connected together by a dedicated push-fit connector, which itself is designed to be waterproof. This allows the closure to have a simple design without the need for expensive seals and easy assembly on site.