• Fiber Optic Closure : It is a fiber enclosure that is either watertight or breathable, aimed at protecting optical fiber splices and connectors coming from different outside plant cables and offers a full protection to the optical fiber. From a construction standpoint, a fiber optic splice enclosure is composed of the enclosure shell ensuring weather protection, a fiber manager which allows routing and protection to buffer tubes, the bare optical fiber, and relevant splices and cable entries.
    • Butt closure: an optical splice enclosure which has all the cable ports on the same side.
    • In-line closure: a splice enclosure with a cable port on two opposite sides.
    • Breathable closure: fiber closure used above grade (pole/façade or strand mount). It offers the appropriate weather protection (rain, pressurized water, dust) while providing the possibility to eliminate internal condensation through venting ports. Breathable closures cannot be used below grade.
    • Gasket-sealing: enclosure is sealed watertight with gaskets.
    • Closure express port (aka oval port or midspan port) : allows an optical fiber cable to be sealed and strain-relieved without cutting the fiber and buffer tubes. It is used in applications where only a few fibers from a feeder cable will be spliced in the closure while other fibers and the relevant midspan will pass through the closure.


  • Single Circuit Management (SCM): type of optical fiber manager inside an optical fiber enclosure. SCMs are dedicated thin fiber splicing trays protecting a circuit 9a-pair or an element, and designed to offer a high grade of fiber protection and separation. Fibers are protected outside the tray and fiber routing is very flexible and adapted to specific engineering.


  • Rack: Vertical support for equipment typically with 1.75 inches of space between mounting holes. Standard rack sizes are 19 inches and 23 inches wide.
    • Rack Space: unit of measure of 1.75 inches for equipment space in a rack. Many housings are measured in rack space.


  • Housing: An enclosure for splicing or termination that protects optical components. Related Terms: Splice Housing, Connector Housing


  • Splicing: Joining of bare fiber ends to one another.
    • Single-fusion splice: fusion splice of two fibers together. The result is an optical continuity between these two fibers. The splice is protected inside a splice protection sleeve.
    • Mass fusion splice: splice of more than two optical fiber ribbons of the same size together. Typical mass fusion splices have four, eight, or 12 fibers, with 12 being the most common.
    • Splice trays (aka Smoove): container used to secure, organize, and protect spliced fibers.
  • Buffer: jacket cable that offers additional mechanical protection to the fiber optic. Generally, two options are available:
    • Tight buffers: directly in contact with the fiber optic.
    • Loose buffers: have a gel layer in between the polymer jacket and the fiber optic.