Due to the limited length of the fiber optic cable and the need for branching of the fiber optic cable on the transmission line, the fiber optic splice closure is produced. Fiber optic splice closure is an important part of the optical distribution network (ODN), which is distributed between the optical port of the optical line terminal (OLT) of the passive optical network (PON) equipment and the optical port of the optical network unit (ONU). Provides safe wiring, easy-to-manage combing space for optical cable splicing, branching, conversion, and diversion, and protects the splice closures. At present, there are many different styles and sizes of fiber optic splice closures on the market, and their suitable applications are also different.
According to the external structure can be divided into horizontal types and dome types (also called vertical types).
Horizontal Fiber Optic Splice Closure
Horizontal fiber optic splice closure is a flat column structure, often used for overhead and buried. Input and output locations are on both sides. That is, enter from port A and exit from port B. This type of structure is more used on trunk lines.
The characteristics of horizontal fiber optic splice closure：
Mechanical gel seal, linear design, suitable for various applications such as overhead, pipeline, and direct burial.
There are at least two fiber optic cable inlets at each end, and split cable accessories are available for selection.
Suitable for all types of fiber optic. Such as layered stranded fiber optic cable, central beam tube cable or skeleton fiber optic cable.
The page-turning fusion splicing tray is convenient to find the optical path and perform cutting, and there are various styles of page-turning fusion splicing trays to choose from.
The valve and ground wire can be added to meet the requirements of the trunk network.
The optical fiber fusion splicing tray is used for optical fiber fusion and branching; the cover can be turned over and the tray can be stacked, which is extremely convenient to expand the capacity, install and use.
Fiber Dome Enclosure/Fiber Optic Vertical Splice Closure
Fiber optic vertical splice closure is mainly designed for laying fiber optic cables in overhead and tunnels.
Fiber optic vertical splice closure is upgraded from horizontal fiber optic splice closure. Fibre optic vertical splice closure the input and output are in the same bottom. Compared with horizontal fiber optic splice closure, Fiber optic vertical splice closure is often “application on accessing layer”.
In terms of sealing process, there are only two parts of fiber optic splice closure that need to be waterproofed:
- The fold of the two parts of the upper and lower covers of fiber optic splice closure
- The line optical cable enters the introduction part of the fiber optic splice closure
Therefore, the moisture-proof effect of fiber optic vertical splice closure in the line is better. Fiber dome enclosure also named fiber optic vertical splice closure, as the name suggests, fiber dome enclosure needs to be installed vertically for maximum waterproof performance. In underground applications, a higher or additional sealing structure is required to ensure its waterproof performance.
The characteristics of fiber dome enclosure：
- It has flip splice trays hinged at one end, which is convenient for installation and future maintenance management.
- Its page-turning fusion splicing tray can protect the bending radius of optical fibers, and can accommodate large circles or small circles according to actual needs.
- Each fusion splicing tray does not affect each other, which avoids the increase of loss caused by the knot of the transition tube.
- Fibers can be switched between trays for added flexibility.
- Mechanical seal and heat shrink seal are combined. Housing and base are sealed with O-ring seals. The fiber optic cable and base are sealed with heat-shrinkable tubing. The casing can be opened repeatedly for many times.
- The locking device is fixed with a clamp, which is convenient for repeated opening, and it only takes a few seconds to open and lock.
- Compatible with the installation of optical passive components such as optical splitters.
Where is Fiber Optic Enclosure Located?
Aerial fiber optic splice closures
The installation method of Aerial fiber optic splice closures is generally strand and pole mountings.
All-Dielectric Self-Supporting (ADSS) cable requires stronger aerial fiber optic splice closures.
Self-supporting aerial cables are designed for convenient, economical one-step installation. More consideration is the economical aerial fiber optic splice closures.
Direct Burial Fiber Splice Closure
Compared with the Aerial type, the direct burial fiber optic cable is buried under the soil freezes. In order not to be damaged by wind and snow. The requirements for the mechanical properties of fiber optic splice closure are more stringent. Need higher moisture resistance, corrosion resistance, compression resistance. Fiber optic vertical splice closure is generally not used. Directly buried optical fibers cannot be removed and replaced, so more choices are heat shrinkable fiber optic splice closure, which does not need to be reopened and has better sealing performance.
Common types of fiber optic splice closure for pipelines: Aerial, pole, wall, direct buried， Below grade（manhole，pipeline）.
Fiber Optic Splice Closure is Available in Several Different Capacities
The number of splice trays inside the fiber optic splice closure determines the capacity of the fiber optic splice closure. The greater the number, the greater the volume of fiber optic splice closure required.
The number of optical cables that various fiber optic splice closures can accommodate is limited, and we should strictly abide by their specifications when using them.
The selection of the number of cores is based on the actual number of end users. In principle, how many cores should be allocated for several users.
Most fiber optic splice closures can accommodate 24 fiber optic connectors, and the 12-core fiber optic splice closure is the most commonly used fiber optic splice closure in fiber optic networks. hello-signal also provides a higher capacity fiber optic splice closure that can accommodate 32 fiber optic connectors. The model of fiber optic splice closure is determined according to the type of optical fiber, hello-signal can provide you with various fiber optic splice closure models to meet your needs.
The splice tray can store fiber optic connectors and remaining fibers in order. The length of the remaining fibers should not be less than 1 meter, and the labyrinth of the remaining fiber optic splice closure should not be less than 35mm. Among them, the storage tray can have up to four layers, and the capacity is large, and the storage tray can be adjusted according to the number of cores connected by the optical fiber.
Common fiber optic splice closure with the following capacities are: 24 core splice closure, 48 core splice closure, 72 core splice closure and 96 core splice closure.
Take this horizontal 96 core fiber optic splice closure from hello-signal as an example, Be equipped with 3 splice trays (each capacity is 32 cores), 6 ports, the fiber optic splice closure can accommodate and protect up to 96 fibers. The horizontal fiber splicing tray is used for optical fiber fusion and branching; the cover can be turned over and the trays can be stacked, which is extremely convenient to expand capacity, install and use.
The hello-signal responds to the needs of different customers, and also provides higher capacity FOC, such as: 144 core splice closure and 288 core splice closure. Take this cap-type 288 core splice closure as an example. It has 12 splice trays and 5 ports. The fiber optic splice closure can accommodate and protect up to 288 optical fibers. The fiber optic vertical splice closure is a page-turning splice tray, which can protect the bending radius of the optical fiber, and can accommodate a large circle or a small circle according to actual needs.
The capacity required by the splice closure determines the number of stacks of the splice trays. The stacking type of the splice trays must meet the requirements for snapping the optical fiber connectors into the splice unit and checking and maintaining them. Every two splicing discs are superimposed, and the six holes on the rubber folds can be clamped to three convex twists on the upper and lower discs respectively; four rubber folds, two at the symmetrical positions on both sides of the disc, If five splicing disks are stacked, according to the above method, fasten the second-layer disk with the third-layer disk, the third-layer disk with the fourth-layer disk, the fourth-layer disk with the fifth-layer disk, and so on, the five disks will be stably superimposed. When it is necessary to check or maintain the welding condition of a certain layer of disks, just remove the two folded sheets that are fastened on the upper layer of the single side of the disk, and the welding disk can be opened like a book page.
If the fibers are not spliced correctly, the splice tray inside the fiber optic splice closure cannot hold enough fibers. Typically, ribbon or mechanical joints are larger in size, which can result in a loss of capacity in the enclosed tray. Proper fitting configuration can avoid installation problems and help improve performance. Therefore, the type of splice closure should be considered when choosing a fiber optic splice closure.
According to The Sealing Form, There are Heat Shrink Seal Type and Mechanical Seal Type
The sealing element is used for sealing between the fiber optic splice closure itself and the fiber optic splice closure and the optical fiber protective cover. FOC has two optional sealing methods: mechanical seal and heat shrink seal.
Heat shrinkable fiber optic splice closure refers to the use of heat shrinkable tubes to achieve the sealing between the optical fibers in the box and the optical fibers outside the box.
Method: Use tubular polyolefin heat shrinkable material coated with hot melt adhesive on the inner wall to be heated and sealed.
- Main advantages: good sealing performance.
- Main disadvantage: repeated opening is inconvenient.
The mechanical seal fiber optic splice closure achieves sealing by compressing the sealing ring between the optical fiber in the box and the optical fiber outside the box.
Method: Mechanically densified using adhesives, vulcanized rubber, non-vulcanized self-adhesive rubber, paste encapsulation mixture, etc.
- Main advantage: easy sealing. The sealing ring can be replaced at any time, and the use and maintenance of the mechanically sealed optical cable splice box is more flexible.
- Main disadvantage: the sealing performance is slightly lower than the heat shrinkable sealing type.
The sealing of the FOC can also be a combination of the two methods.
According to The Fiber Connection Method, It Can be Divided into Direct Connection and Branch Connection
The internal connection methods are divided into two types: direct connection and branch connection.
Direct connection is to connect two optical fibers with the same number of cores together.
The branch connection is to separate a large-core-count fiber and connect more than one small-core-count fiber correspondingly or cross-connect multiple fibers with each other.
The main network is generally in the direct mode, and the access layer is mainly in the branch mode.
Direct splicing uses a mechanical splice, which mechanically snaps off the fibers to be butted and aligns the cores through the concentricity of the splice. For branch connection, a fusion splicer is used to thermally splic the optical fibers to be connected together, and they are fixed and protected by heat shrinkable sleeves.