Introduction to Fiber Optic Splice Closure
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Introduction to Fiber Optic Splice Closure

Posted on by FS.COM

In order to meet the stringent protection requirements of fiber optic splices, fiber optic splice closures, also called fiber splicing closures, are usually used to provide space for fiber optic cables to be spliced together. Fiber optic splice closures connect and store optical fibers safely either in the outside plant or indoor buildings. They can provide protection for the fiber joint and the fiber cables, since they have excellent mechanical strength and strong out shell, which ensure the joints not be damaged by the hostile environment.

Key Features of Fiber Optic Splice Closures

Fiber splice closures are made from special industrial grade, high tension plastic with a reliable moisture barrier. They are also optimized to resist aging of the material due to factors in the natural environment such as ultraviolet light.

 The box adds aging-resistant in imported high tensile construction plastic out-faster is made up of stainless steel
 Overlap structure in splicing tray is easy to install
 Suitable for ordinary fiber and ribbon fiber
 Perfect leak proofness
 Perfect and reliable sealing operations
 Fiber-bending radium guaranteed more than 40mm
 Full accessories for convenient operations
 Fiber optic splice closure can be used repeatedly
 For aerial, and direct buried applications

Types of Fiber Optic Splice Closure

According to the physical appearance, fiber optic splice closure can be classified into two major types: horizontal type and vertical type.

1) Horizontal type

Horizontal type fiber optic splice closure is like a flat or cylindrical case. It usually contains one or more fiber splice tray to provide space and protection for fiber optic splices. Fiber splice trays used in different fiber optic splice closures may have different designs and fiber counts. The following picture shows a 96-fiber horizontal fiber optic splice closure. It has two input ports and two output ports providing space for 96 fiber splices. There are four standard 24-fiber splice trays stacked together inside the fiber optic splice closure.

horizontal splice closure

Horizontal fiber optic splice closures are designed to be waterproof and dust proof. They have good adaptability and compression resistance, for they are commonly made of high tensile construction plastic. Horizontal optical closures are used more often than vertical fiber optic closures.

2) Vertical Type

Vertical fiber optic splice closure looks like a dome, thus they are also called dome fiber optic splice closure. They meet the same specification as the horizontal types and are designed for buried applications. Vertical fiber optic splice closures are made of excellent engineering plastics, they are with 1inlet/outlet ports, 2inlet/outlet ports, 3inlet/outlet ports types, fitting different fiber optic core numbers. The following shows a 24-fiber splice closure which has five entries providing up to 24 fiber optic splices in two 12-fiber splice trays. Different from the above one, the internal fiber splice tray here is suitable for the vertical design of the fiber splice closure.

vertical splice closure

Factors to Consider When Choosing Fiber Splice Closure

Cable Compatibility

A good fiber optic splice closure shall be capable of accepting any fiber optic cable as specified in the tender document. Thus, it is vital to figure out the cable compatibility before selecting the right closure type. The design of fiber optic splice closure changes with the application areas. Therefore, a fiber optic splice closure for aerial will have different design from that used for underground application.

Numbers of Cable Ports

Cable port is also known as the cable entrance capacity. The number of ports in a fiber optic splice closure reflects its capacity to handle the number of cables. The cable entrance capacity of a fiber optic splice closure refers to the number of ports available for terminating cable within the closure. The number of ports provided in a closure depends on factors such as the network capacity and number of cables employed in the network. Usually, in an attempt to reduce the physical size of high-capacity closures, smaller ports shall be utilized for branch cables and drop cables.

Termination System

Before choosing the splice closure type, the cable termination system should be designed to provide sufficient mechanical strength between the cable and closure to ensure its performance throughout the lifetime. The materials used for fiber optic splice closures shall also be capable of minimizing or negating the effects of relative motion between cable components, because the materials used in optical fibers are easy to thermal expansion and contraction.

Bonding & Grounding

Proper bonding and grounding of conductive elements of the optical network shall be provided for the safe deployment and operation of the network.


Aerial fiber optic closures may need to hang on the messenger wire depending on the network configuration. Or they may be attached to the pole. In both cases, extra hardware is required along with the closures. The hardware to attach and secure should be able to bear wear and tear and also environmental stresses.


FS.COM supplies fiber optic splice closures with different ports types, fittings and fiber optic core numbers. These splice closures are made of excellent engineering plastics and suitable for protecting optical fiber splices in straight through and branching applications, and can be used in aerial, duct and direct buried fiber optic cable projects. Fiber splice tray, fiber distribution box and fiber optic enclosure are also offered in conjunction with the splice closures, promoting a safe and well-managed environment for fiber optic splices. Custom service is available according to your requirements. For more details, please contact us via

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