Fiber optic closure, also known as fiber optic splicing closures, is a device used to provide space and protection for fiber optic cables spliced together. The fiber optic closure connects and stores optical fibers safely either in the outside plant or indoor buildings. It can provide protection for the fiber joint and the fiber cables since they have excellent mechanical strength and strong out shell, which ensures the joints are not damaged by the hostile environment.

1. Horizontal Design

The horizontal design is the most common option, probably because it is so versatile. This type of box is fairly flat or cylindrical in shape. It can be mounted aerially or buried underground. A horizontal closure can have various capacities, with some much higher than others. A standard, normal-capacity closure can have several splice trays, which have their own differing capacities for the number of cables they can handle. Of course, higher-capacity closures can fit many more. Common numbers for tray capacities include 12 and 24. Though designs and dimensions can vary, most horizontal boxes will follow similar specifications.

However it looks, a horizontal box needs to be waterproof, dustproof and have good resistance to compression. If attached to a pole or hung from wiring, these closures need to be held firmly in place, to avoid damage from weather and wind.

2. Vertical Design

This design has a domed shape and is intended for buried applications, though you can use many of them above-ground as well. These closures can again take on several different configurations and capacities, with high-capacity versions and variations in the number of trays. They can also vary in the number of inlet and outlet ports available, to match the cable capacity. Reentry may or may not be critical, depending on the closure's placement, but some boxes are designed for easier re-entry than others.

Again, the vertical designs need to retain protection from the elements. Seals and waterproof technology are especially important. These are often used underground, where those dangers are prevalent and can pose serious risks to the cabling inside. Keeping insects and dirt out is particularly important for underground closures.

3. Hybrid Fiber Enclosure

The hybrid fiber enclosure is capable of securing network fiber regardless of weather, temperature, or location making it the most versatile of the enclosures. This flexibility allows for wall, aerial, or cell installations. In addition, a compact design allows for pedestal mounting and below-grade applications. 

Given the variety of potential mounting locations for the hybrid fiber enclosure, it is designed to IP68 rating and can withstand dust, dirt, sand, and is water-resistant.