What is a Fiber Optic Splice Closure?

A Fiber Optic Splice Closure is a special device used to connect, protect and manage optical cables. It is usually used for operations such as splicing, branching, straight-through or reservation of optical cables. It plays a key role in optical fiber communication systems, ensuring the stable operation and long-term reliability of optical cables in various environments.

The main functions of Fiber Optic Splice Closurees
Optical cable connection: used to connect two or more optical cables to achieve continuous transmission of optical signals.

Mechanical protection: prevents the optical cable from being damaged by tension, bending or external forces at the connection.

Environmental protection: provides sealing properties such as waterproof, dustproof and moisture-proof to prevent moisture, dust, insects, etc. from entering the interior.

Residual fiber management: provides a fixed and sorting space for the remaining fibers after optical fiber splicing, which is convenient for maintenance and management.

Support and fixation: provides physical support for the optical cable to prevent loosening due to gravity or vibration.

Composition structure of Fiber Optic Splice Closure
Casing (joint box cover): usually made of metal or high-strength plastic, with good pressure resistance and corrosion resistance. The surface is designed with mounting holes, sealing grooves, etc. for easy installation and sealing.

Sealing components: commonly used are silicone gaskets, heat shrink tubing, O-rings, etc., used to achieve IP level protection (such as IP68).

Fixing devices: including clamps, brackets, bolts, etc., used to fix optical cables to prevent slippage.

Residual fiber collection tray: used to organize and fix the excess length of optical fiber for easy welding and maintenance.

Fusion module (optional): Some advanced models have built-in fusion splicers or heat shrink units for on-site welding operations.

Types of fiber splice closures
Depending on the usage scenario and functional requirements, fiber splice closures can be divided into the following types:

Type	Description	Applicable scenarios
Horizontal (in-line)	Cylindrical structure, suitable for straight-line fusion of two cables.	Commonly used for underground or overhead installation.
Vertical (dome)	Dome-shaped structure, suitable for multi-way branch connection.	Commonly used for FTTH networks.
Heat shrink type joint box	Sealing is achieved by heat shrink tubing, suitable for old installation.	Applicable to early fiber optic cable network transformation projects.
Mechanical seal type joint box	Sealing is achieved by gasket and clamp, which can be reused.	Modern mainstream choice, suitable for new projects.

Technical parameters of fiber optic splice closure

Parameters	Description
Waterproof level	Usually IP68, can work in water for a long time.
Dustproof level	IP55 or higher, suitable for outdoor environment.
Operating temperature range	-40°C to +85°C, adapt to extreme climate conditions.
Pressure bearing capacity	70 kPa to 106 kPa, suitable for direct burial or deep burial environment.
Material	Usually made of stainless steel, high-strength engineering plastics or composite materials.
Maximum number of cores supported	Depending on the model, it can support 2 cores to 120 cores.
Installation method	Support multiple laying methods such as overhead, pipeline, direct burial, etc.

Application scenarios of Fiber Optic Splice Closurees
FTTH (fiber to the home) network: used for fiber access in the last kilometer, connecting optical cables and user terminals.

FTTB (fiber to the building) network: used for fiber distribution inside buildings.

Urban optical cable network: used for connecting trunk optical cables with branch optical cables.

Power communication system: used for optical fiber communication connections in power towers, substations and other places.

Monitoring and security systems: used for optical fiber connections for video surveillance, intelligent transportation and other systems.

Submarine optical cables and long-distance communications: used for cross-ocean or cross-regional optical cable connections.

What are the common types of Fiber Optic Splice Closurees? What installation environments are they suitable for?
Horizontal (in-line) splice box

The horizontal (in-line) splice box is a common optical cable connection device, usually cylindrical or rectangular in structure, with multiple fusion modules or fixed slots inside. Its main structures include:

Casing: usually made of metal or high-strength plastic, with good pressure resistance and corrosion resistance.

Fusion module: used for optical fiber fusion splicing, with a fusion tray, heat shrink tube or cold splice module inside.

Fixing fixture: used to fix the optical cable to prevent the optical cable from sliding or shifting during the connection process.

Sealing components: such as silicone gaskets, O-rings, etc., used to achieve waterproof and dustproof.

Residual fiber collection tray: used to organize and fix the excess length of optical fiber for easy fusion and maintenance.

Horizontal joint box is suitable for the following installation environments:
Underground direct burial installation: used for optical cable connection under urban roads or in green belts.
Pipeline laying: used for direct connection of optical cables in underground pipelines.
Overhead installation: used for direct connection of optical cables on poles.
Indoor wiring: used for direct connection of optical cables inside buildings.

Installation method of horizontal (in-line) joint box
Direct burial installation: bury the joint box directly underground, suitable for rural or remote areas.
Pipeline installation: put the joint box into the pipeline, suitable for urban underground optical cable network.
Overhead installation: fixed on the pole by hooks or brackets, suitable for trunk optical cable connections in cities or suburbs.

The structural design of the horizontal (in-line) junction box is relatively simple. The internal components include fusion modules, fixing fixtures, sealing components and residual fiber collection trays, etc. The overall layout is clear and easy to install and maintain. This structure makes it very suitable for single-point connection scenarios.

such as straight-through connection of trunk optical cables, which can effectively reduce branching losses and improve the stability of optical signal transmission. In addition, due to its simple structure and low cost, it is more economical than other types of junction boxes and is suitable for projects with limited budgets. At the same time, the installation process of the horizontal junction box does not require complex tools, is easy to operate, and is suitable for rapid construction, especially for temporary or emergency optical cable connection needs.

Although the horizontal junction box is suitable for single-point connection and trunk optical cable straight-through, its structure only supports "one in and one out" or "one in and one out and then branching", which is not suitable for multi-way branching connection, especially in high-density scenarios such as data centers and smart buildings.

In addition, its internal space is limited, the utilization rate is low, and the scalability is poor, which makes it difficult to meet the needs of the continuous development of the optical cable network. Therefore, when choosing the type of joint box, it is necessary to make reasonable planning based on actual needs.

Vertical (dome-type) joint box
The vertical (dome-type) joint box is a device suitable for multi-way branch connection. It is usually dome-shaped or hemispherical in structure, with a large internal space, which can accommodate the branch connection of multiple optical cables. Its main structure includes:

Casing: usually made of metal or high-strength plastic, with good pressure resistance and corrosion resistance.

Fusion module: There are multiple fusion trays or branch ports inside, such as 1 input/4 output, 1 input/6 output, etc.

Rotary fusion tray: It is convenient for the connection and management of multiple optical cables.

Sealing components: such as silicone gaskets, O-rings, etc., used to achieve waterproof and dustproof.

Residual fiber collection tray: used to organize and fix the excess length of optical fiber, which is convenient for fusion and maintenance.

Vertical junction boxes are widely used in the following scenarios:
FTTH (Fiber to the Home) network: used to connect the last mile access between the trunk optical cable and the user terminal.
Building internal wiring: used to connect the trunk optical cable in the building with the branch optical cable of each floor or unit.
Indoor/outdoor hybrid installation: suitable for optical cable branch connection in existing building renovation or new construction projects.
High-density access points: such as data centers, smart buildings, urban optical cable networks, etc.

Installation method of vertical (dome) junction box
Indoor installation: used for optical cable branch connection inside the building.
Outdoor installation: used for outdoor optical cable branch connection, such as FTTH access point.
Hybrid installation: suitable for optical cable branch connection in existing building renovation or new construction projects.

Vertical (dome) junction box supports multi-channel branch connection, suitable for high-density optical cable access scenarios, such as 1 input/4 output, 1 input/6 output and other configurations. Its internal space is large, which is convenient for optical cable arrangement and residual fiber management, and is suitable for high-density access points such as residential areas and office buildings. At the same time, this type of joint box is flexible to install and can support multiple laying methods such as overhead, pipeline, and direct burial.

However, its structure is relatively complex, and installation and maintenance require certain skills. The cost is also slightly higher than other types, and it has certain requirements for the installation environment, which is not suitable for temporary construction.

Heat shrinkable joint box
The heat shrinkable joint box is a device that is sealed by heat shrink tube or heat shrink sleeve. It is usually designed in a miniaturized manner and is suitable for the connection of a small number of optical cables. Its main structure includes:

Housing: usually made of plastic or metal, with a simple structure.

Fusion module: There is a fusion tray or cold connection module inside for optical fiber fusion.

Heat shrink tube: It shrinks by heating to form a tight waterproof seal.

Fixed clamp: used to fix the optical cable to prevent sliding.

Residual fiber collection tray: used to organize and fix the excess length of optical fiber for easy fusion and maintenance.

The heat shrinkable joint box is suitable for the following scenarios:
Early optical cable network transformation project: used for the connection and upgrade of old optical cables.
Temporary or emergency installation: such as temporary construction, temporary communication lines, etc.
Small access points: such as small base stations, temporary monitoring points, etc.
Projects with limited budgets: Suitable for projects with high cost requirements.

Installation methods of heat shrinkable joint boxes
Quick installation: Sealing is achieved by heating and shrinking the heat shrink tube, which is suitable for quick construction.
Miniaturized installation: Suitable for scenarios with limited space, such as small access points.
Temporary installation: Suitable for temporary construction or emergency communication lines.

The heat shrinkable joint box is easy to install, does not require complex tools, and is suitable for quick installation, especially for projects with limited budgets. It achieves good waterproof performance through shrinking the heat shrink tube, has strong sealing, and can effectively protect the internal optical fiber from environmental factors.

In addition, this type of joint box is suitable for the connection of a small number of optical cables, suitable for small access points or temporary construction scenarios. However, the heat shrinkable joint box cannot be reused, and it cannot be opened again once the heat shrink is completed, which limits its application in scenarios that require frequent disassembly and assembly. At the same time, heat shrink materials have a short lifespan, are prone to aging, and are only suitable for the connection of a small number of optical cables, not suitable for multi-channel branching or high-density access requirements.

Mechanically sealed joint box
The mechanically sealed joint box is a device that uses gaskets, O-rings, sealing gaskets and other mechanical methods to achieve sealing. It is usually modular in design and suitable for a variety of optical cable connection scenarios. Its main structures include:

Casing: usually made of metal or high-strength plastic, with good pressure resistance and corrosion resistance.

Fusion module: There are multiple fusion trays or branch ports inside, such as 1 input/4 output, 1 input/6 output, etc.

Sealing components: such as silicone gaskets, O-rings, sealing gaskets, etc., used to achieve waterproof and dustproof.

Fixing fixture: used to fix the optical cable to prevent sliding.

Residual fiber collection tray: used to organize and fix the excess length of optical fiber for easy fusion and maintenance.

Mechanically sealed joint boxes are suitable for the following scenarios:
New projects: suitable for modern communication network construction, such as FTTH, FTTB, etc.
High-density access scenarios: such as data centers, smart buildings, urban optical cable networks, etc.
Multiple laying methods: Support multiple installation methods such as overhead, pipeline, and direct burial.
Scenarios that require frequent disassembly and assembly: such as data centers, base stations, and other scenarios that require frequent maintenance.

Installation method of mechanical seal type joint box
New project: Suitable for modern communication network construction, such as FTTH, FTTB, etc.
High-density access scenarios: such as data centers, smart buildings, urban optical cable networks, etc.
Multiple laying methods: Support multiple installation methods such as overhead, pipeline, and direct burial.
Frequent disassembly and assembly scenarios: Suitable for scenarios that require frequent maintenance, such as data centers, base stations, etc.

Mechanical seal type joint box has the characteristics of reusability and replaceable seals, which is suitable for scenarios that require frequent disassembly and assembly, such as data center or base station maintenance. Its mechanical seal structure is more durable and has a longer service life than the heat shrink type, and is highly adaptable, suitable for various environments and optical cable types. In addition, this type of joint box is flexible to install and supports multiple laying methods such as overhead, pipeline, and direct burial to meet the needs of different scenarios.

However, its installation is relatively complex and requires professional tools and personnel with certain technical skills. The cost is also relatively high, and there are certain requirements for the installation environment. It is necessary to ensure that the seals are installed in place to avoid water seepage problems.

What kind of protection does the waterproof rating of the fiber optic splice closure (such as IP68) provide?
The waterproof rating of the fiber optic splice closure (such as IP68) can provide the following protection:

Complete dustproof: The first number "6" of the IP68 rating means that the device can completely prevent the entry of solid objects with a diameter greater than 1mm, that is, it can block all dust particles and ensure that the internal components are not disturbed by dust.

High waterproof performance: The second number "8" of the IP68 rating means that the device can be immersed in water for a certain period of time, usually 1 meter deep for more than 30 minutes, and even in some cases up to 1.5 meters deep. This protection capability enables the fiber optic splice closure to maintain stable operation in harsh water environments.

Suitable for outdoor and harsh environments: IP68 waterproof splice closures can effectively resist the influence of environmental factors such as rain, moisture, and water splashes, and are suitable for outdoor, mine, tunnel, underground and other environments with heavy water or dust. For example, in FTTH (fiber to the home) networks, IP68 waterproof splice closures can ensure the stability and reliability of fiber optic connections.

Good sealing: IP68 waterproof grade junction boxes usually adopt effective sealing measures, such as O-rings, gaskets and sealing adhesives, to prevent moisture and other particles from entering the housing. This design ensures that the equipment will not fail due to the influence of the external environment during long-term use.

Corrosion resistance and aging resistance: IP68 waterproof grade junction boxes are usually made of high-quality materials, such as aluminum alloy, plastic and ABS plastic, which have good corrosion resistance and aging resistance, and can extend the service life of the equipment.

Suitable for a variety of installation methods: IP68 waterproof grade junction boxes are not only suitable for overhead installation, but also for pipeline laying and direct burial installation, which can meet the installation requirements in different environments.

How does the sealing performance of the optical fiber junction box ensure reliability in long-term use?
The sealing performance of the optical fiber junction box is one of the key factors to ensure its long-term reliability. In order to ensure that the sealing performance remains stable in long-term use, a variety of technical means and materials are usually used to achieve effective waterproof, dustproof and moisture-proof protection. Here are some common sealing technologies and how they ensure long-term reliability:

Mechanical seal: Mechanical seal is the most widely used sealing method. It is achieved by tightly fixing the cover of the splice box to the shell using components such as silicone gaskets, O-rings, and stainless steel screws. This sealing method has good repeated opening and closing performance and is suitable for scenarios that require frequent maintenance. In addition, the mechanical seal structure is not easy to age during long-term use, and can effectively prevent moisture and dust from entering the splice box, thereby protecting the fiber optic connector from environmental influences.

Heat shrink seal: Heat shrink seal is to shrink the heat shrink tube or heat shrink sleeve around the optical cable to form a tight sealing layer. This method is suitable for connecting a small number of optical cables, especially in early optical cable network reconstruction projects. Heat shrink materials can fit tightly to the cable sheath after heating, providing good waterproof performance. However, heat shrink seals are not reusable and cannot be opened again once the heat shrink is completed, so they are more suitable for one-time installation scenarios.

Elastomeric rubber seal: Elastomeric rubber sealing materials (such as TPE gel) have good flexibility and resilience, and can fill all gaps inside the splice box to form a seamless seal. This material can be evenly distributed when under pressure to ensure the sealing effect. In addition, the elastomeric rubber sealing material also has the characteristics of anti-aging and corrosion resistance, and can be used for a long time in harsh environments.

Silicone sealing: Silicone sealing material is a newer sealing technology with excellent temperature resistance and chemical stability, and can adapt to a wide range of environmental conditions. Silicone sealing material is formed in a mold at one time, so that the joint surface of the junction box is seamless, thus providing reliable sealing performance. In addition, silicone sealing material can also cover a wider range of cable diameters and adapt to optical cables of different specifications.

Double sealing design: In some high-end or special application junction boxes, a double sealing design is adopted, that is, a layer of heat shrink or elastomer sealing is added on the basis of mechanical sealing to further improve the sealing performance. This design can effectively cope with the sealing challenges in complex environments and ensure that the junction box will not fail due to changes in the external environment during long-term use.

Compatibility and durability of sealing materials: In order to ensure the long-term reliability of sealing performance, the sealing material used in the junction box must be compatible with the optical cable material and have good aging and corrosion resistance. For example, the YD/T 814.x series of standards clearly stipulates the physical, chemical properties and compatibility requirements of the joint box materials to ensure that the sealing materials will not deteriorate due to environmental factors (such as moisture, salt spray, ultraviolet rays, etc.).

Construction process and installation specifications: In addition to the materials themselves, construction process and installation specifications are also important factors affecting the sealing performance. For example, during the installation process, it should be ensured that the sealing ring is evenly placed in the sealing groove and the screws are tightened without leaving any gaps. In addition, the polishing of the optical cable sheath should also be carried out to ensure that the sealing tape or sealing ring can be tightly combined with the surface of the optical cable, thereby improving the sealing effect.

What are the special applications of optical fiber joint boxes in FTTH networks?
Optical fiber joint boxes have many special applications in FTTH (fiber to the home) networks, which are mainly reflected in the following aspects:

Connection and distribution functions: In FTTH networks, optical fiber joint boxes are used to connect trunk optical cables with user access optical cables to achieve optical fiber fusion, fiber splitting and distribution. For example, the fiber optic cable splitter box (box) can complete the connection between the distribution cable and the user cable outdoors or indoors, and supports multi-level splitting solutions. In addition, the Fiber Optic Splice Closure also supports the fixation, fusion and residual fiber management of optical fibers to ensure the stability and reliability of optical fiber connections.

Protective connection: The Fiber Optic Splice Closure provides mechanical protection and environmental sealing for the optical fiber connection to prevent external factors such as moisture and dust from damaging the optical fiber.

For example, the Fiber Optic Splice Closure with IP65 protection level can effectively resist the influence of environmental factors such as rain and humidity, and is suitable for scenes with heavy water or dust in outdoor, mine, tunnel and other environments. In addition, the sealing performance of the splice box is achieved by mechanical sealing, heat shrink sealing and other methods to ensure long-term reliability.

Flexible installation method: The Fiber Optic Splice Closure supports a variety of installation methods, including wall-mounted, pole-mounted and rack-mounted installation, suitable for different application scenarios.

For example, the FTTH socket panel can be flipped for easy maintenance and installation, suitable for indoor and outdoor use. In addition, the Fiber Optic Splice Closure can also be installed on poles or buildings to provide stable protection for optical fiber connections.

Support multiple connection methods: The Fiber Optic Splice Closure supports multiple connection methods, including fusion splicing, cold splicing, and on-site connection. For example, the Fiber Optic Splice Closure is equipped with pre-polished pins and mechanical connectors. No fiber optic splicer or polishing is required. The fiber optic link can be docked through simple connection tools. In addition, the Fiber Optic Splice Closure also supports adapter interfaces such as SC and LC, which are suitable for different types of fiber optic connection needs.

Strong adaptability: The Fiber Optic Splice Closure is suitable for various environmental conditions, including harsh environments such as high temperature, high humidity, and strong wind.

For example, the operating temperature range of the Fiber Optic Splice Closure is usually between -40°C and +85°C, which can adapt to extreme climatic conditions. In addition, the Fiber Optic Splice Closure also has good corrosion resistance and anti-aging properties, which can extend the service life of the equipment.

Support high-density access: In the FTTH network, the Fiber Optic Splice Closure supports high-density access needs, such as 1 input/4 output, 1 input/6 output and other configurations. This type of splice box is suitable for high-density access points such as residential areas and office buildings to meet users' needs for fiber optic access.

Easy maintenance and management: The design of the Fiber Optic Splice Closure is easy to maintain and manage. For example, the internal structure of the Fiber Optic Splice Closure is reasonably designed, which is convenient for the arrangement and fixation of optical fibers and reduces optical fiber loss. In addition, the installation process of the Fiber Optic Splice Closure is simple, does not require complex tools, and is suitable for rapid construction.

What are the installation methods of the Fiber Optic Splice Closure?
There are many ways to install the Fiber Optic Splice Closure, and the specific choice depends on the laying method of the optical cable and the actual environmental requirements. The following are several common installation methods and their detailed descriptions:

Overhead installation: Overhead installation is to fix the Fiber Optic Splice Closure on a pole or bracket, which is suitable for trunk optical cable connections in cities or suburbs. Racks, screws and other accessories are required during installation to ensure that the splice box is stable. This installation method is suitable for scenarios where ground interference needs to be reduced, such as access points in FTTH networks.

Pipeline installation: In pipeline laying, the Fiber Optic Splice Closure is usually installed in the manhole or handhole of the pipeline to protect the optical cable from the external environment. During installation, the splice box needs to be placed at a higher position in the manhole to prevent water from soaking, and the splice box needs to be fixed with a bracket to ensure that the remaining cable of the optical cable is coiled in an "O" ring and fixed with a tie wire.

Direct burial installation: Direct burial installation is to bury the Fiber Optic Splice Closure directly underground, which is suitable for rural or underdeveloped areas. When installing, you need to select the appropriate inlet and outlet pipes according to the diameter of the optical cable, and ensure that the sealing treatment is in place to prevent moisture and soil pressure from damaging the optical cable.

Wall-mounted installation: Wall-mounted installation is suitable for optical cable connections indoors or inside buildings, and is usually used for terminal access in FTTH networks. You can choose to hang on the wall or hold the pole when installing. The shell material of the splice box is mostly high-quality carbon steel with surface spraying treatment, which has good corrosion resistance and mechanical strength.

Rack-mounted installation: Rack-mounted installation is suitable for scenes that require frequent maintenance, such as data centers and base stations. The splice box can be installed in a standard rack for easy management and maintenance. Special fixing accessories must be used during installation to ensure that the splice box is stable in the rack.

Repeated opening installation: Some high-end splice boxes support repeated opening and closing, which is suitable for scenes that require frequent maintenance. When installing, you only need to loosen the hexagon socket screws to open the splice box. It is easy to operate and suitable for a variety of connection methods such as cold connection and hot melt.

Heat shrink seal installation: Heat shrink seal is an installation method that achieves sealing by shrinking the heat shrink tube, which is suitable for connecting a small number of optical cables. During installation, the heat shrink tube needs to be put on the optical fiber, and after heating, it is tightly combined with the optical fiber to form good waterproof performance.

Mechanical seal installation: Mechanical seals are sealed by using components such as O-rings and gaskets, which are suitable for scenarios that require multiple disassembly and assembly. During installation, ensure that the sealing ring is evenly placed in the sealing groove and tighten the screws to prevent water seepage.