Outdoor Optical Fiber Joint Box With Sealed Splice Closure For Optical Cable Connection
As a core device for ensuring the safety of optical cable connections in optical fiber communication networks, optical fiber joint boxes play an irreplaceable role as "guardians" in the optical signal transmission chain. They not only need to ensure the physical safety of optical fiber joints but also guarantee the stable transmission of optical signals in complex environments. Their parameter characteristics cover multiple dimensions from basic capacity to complex environmental adaptability, with each parameter directly affecting the applicable scenarios and operational performance of the device. The following provides a comprehensive and in-depth analysis of their parameter characteristics from multiple key perspectives.
Capacity Specifications: Meeting Diverse Network Connection Needs
Capacity specification is one of the most fundamental and important parameters of optical fiber joint boxes, directly defined by the number of fiber cores the device can accommodate, serving as the core indicator for measuring the device's carrying capacity. Against the backdrop of the rapid development of current optical fiber networks, different scales of communication networks have significantly varying capacity requirements for optical fiber joint boxes, thus forming a rich and diverse system of capacity specifications in the market.
Common basic capacity specifications include 12-core, 24-core, 48-core, and 96-core, which are widely used in small and medium-sized network scenarios such as urban access networks, campus networks, and enterprise intranets. For example, in fiber-to-the-home projects in residential communities, 24-core and 48-core joint boxes are commonly used to meet the fiber connection needs of multiple households. For large backbone networks, data center interconnections, and other scenarios, joint boxes with larger capacities are required, leading to the emergence of 144-core, 288-core, and even higher-capacity products. The GPJ09-5602 optical cable joint box launched by Changfei Optical Fiber can accommodate up to 144 cores for stranded fibers and an impressive 432 cores for ribbon fibers, fully meeting the high-density connection needs of large-scale networks.
The design of capacity specifications is not a simple accumulation of numbers but is closely related to the type of optical fiber. There are obvious differences in capacity calculation and layout methods between stranded fibers and ribbon fibers. Stranded fibers take a single optical fiber as the basic unit, with each fiber individually fixed and protected by a fiber fusion tray inside the joint box; while ribbon fibers integrate multiple fibers into a single ribbon unit, with common specifications such as 12 cores/ribbon and 24 cores/ribbon. Therefore, the capacity calculation of ribbon fiber joint boxes is usually determined by multiplying the number of ribbons by the number of cores per ribbon. For example, a 288-core ribbon fiber joint box can accommodate 24 ribbons of 12-core ribbon fibers or 12 ribbons of 24-core ribbon fibers. This differentiated capacity design enables joint boxes to flexibly adapt to the connection needs of different types of optical cables, enhancing the versatility and practicality of the device.
With the continuous expansion of optical fiber networks, modular capacity design has become an important development trend in modern optical fiber joint boxes. Many manufacturers have launched joint box products that support capacity upgrading by adding fiber fusion trays or expansion modules. For instance, the expandable joint box from Zhongtian Technology has a basic configuration of 48 cores and can be easily upgraded to 96 cores or even 144 cores by adding expansion modules, greatly reducing the cost of replacing equipment during network expansion and extending the device's service life.
Size Specifications: Adapting to Diverse Installation Environments
The size specifications of optical fiber joint boxes are closely related to their installation location, capacity, and structural type, showing rich diversity to ensure that the device can achieve stable installation and efficient operation in various complex physical spaces.
Rack-mounted joint boxes are mainly used in places requiring centralized management such as equipment rooms and data centers, with their sizes strictly following standardized designs. The 19-inch rack-mounted joint box is a mainstream product in the market, with a fixed width of 19 inches (approximately 482.6mm). This size is compatible with the globally communication equipment rack standards, enabling installation alongside servers, switches, routers, and other devices in standard racks, realizing centralized management and unified cabling of equipment. Their height varies according to capacity, including 1U (44.45mm), 2U, 3U, etc. For example, 24-core rack-mounted joint boxes usually adopt a 1U height design, occupying small space and suitable for high-density installation; while 96-core and 144-core rack-mounted joint boxes require 2U or 3U heights to accommodate more fiber fusion components and fiber management structures. To improve space utilization, some manufacturers have launched 23-inch wide rack-mounted joint boxes, with the width increased to 23 inches (approximately 584.2mm), capable of accommodating more fiber cores at the same height, meeting the high-density connection needs of large data centers.
Wall-mounted joint boxes are suitable for installation on vertical surfaces such as walls and columns, with their size design focusing more on space adaptability. Such joint boxes are usually labeled with specific length, width, and height values. For example, the TD-BG-48 wall-mounted joint box from Tongding Interconnection has dimensions of 520×320×150mm, and its compact design allows easy installation in narrow spaces such as building walls and sides. Wall-mounted joint boxes can be divided into horizontal and vertical types. Horizontal boxes have a larger length-diameter ratio, such as the SPFC-PH-24M-4/4E horizontal optical cable joint box from Hong'an Communication, with dimensions of 470×240×120mm, suitable for horizontal wall installation; vertical boxes have larger dimensions in the height direction, such as the 300×200×400mm vertical wall-mounted box, suitable for vertical column installation, better adapting to different spatial layouts.
Underground buried joint boxes are mainly used in underground pipeline or direct burial scenarios, with their size design needing to balance protective performance and underground space adaptability. Such products mostly adopt cylindrical or square structures. Cylindrical joint boxes usually have a diameter ranging from 150mm to 300mm and a height (length) ranging from 300mm to 600mm. For example, the GJS-7001 cap-type buried joint box from Changfei Optical Fiber has dimensions of 435×190mm (height × width), which can match the inner diameter of underground pipelines for easy installation and laying. Square buried boxes focus more on pressure resistance, with sizes mostly 350×350×200mm, 500×400×250mm, etc. Their flat design can reduce burial depth, lower construction difficulty, and enhance the pressure resistance of the device.
The sizes of joint boxes for special environments are custom-designed according to specific scenario requirements. For example, joint boxes used for submarine optical cables have larger shell sizes and significantly increased wall thickness to withstand huge deep-sea pressure, with diameters up to over 500mm and lengths exceeding 1000mm; while joint boxes used in narrow spaces such as mines and tunnels adopt miniaturized designs, with some products having sizes controlled within 200×150×100mm to adapt to installation in confined spaces.
Structural Types: Balancing Protection and Operational Convenience
The structural type of optical fiber joint boxes directly affects their protective performance, maintenance convenience, and applicable scenarios. Currently, there are three main types in the market: closed, open, and hybrid structures, each with unique design features and application advantages.
The closed structure is the first choice for harsh outdoor environments, with its core design concept of blocking the intrusion of external environmental factors through a structure. Closed joint boxes usually adopt an integral sealing design, with shells made of high-strength materials, combined with rubber sealing rings, sealants, and other sealing materials to form multiple sealing protections. This structure can effectively block the intrusion of dust, moisture, humidity, corrosive gases, and other external factors, protecting internal fiber connection components from damage and ensuring stable transmission of optical signals. For example, the closed optical cable joint box from Changfei Optical Fiber adopts advanced mechanical sealing technology, with a protection level of IP68, capable of being immersed in water at a depth of 2 meters for a long time without water ingress, suitable for various harsh environments such as outdoor overhead, underground burial, and underwater. The disadvantage of the closed structure is that maintenance operations are relatively complex, requiring special tools to open the shell, thus being more suitable for scenarios with high protection requirements and low maintenance frequency.
The open structure focuses more on operational convenience, facilitating construction personnel to perform fiber fusion, patching, testing, and other operations on internal fibers. Open joint boxes usually adopt a reversible or detachable cover design, allowing the device to be opened without special tools. Construction personnel can intuitively see the layout and connection status of internal fibers, greatly improving construction and maintenance efficiency. This structure is usually suitable for relatively stable indoor environments such as equipment rooms, data centers, and rooms, where there is little dust, low humidity, small temperature changes, and relatively low requirements for sealing performance. For example, the open optical fiber joint box launched by Huawei adopts a modular design, with internal fiber fusion trays that can be flexibly pulled out, facilitating fiber fusion and management, and is favored by equipment room maintenance personnel. The disadvantage of the open structure is that its protective performance is relatively weak, unable to effectively block the intrusion of external dust and moisture, thus not suitable for outdoor or harsh environments.
The hybrid structure is a new structural design emerging in recent years, integrating the advantages of closed and open structures, improving operational convenience while ensuring certain protective performance. Hybrid joint boxes usually adopt a double-layer structure, with an outer closed protective shell providing basic dust and water protection; and an inner open operation cavity facilitating fiber fusion and management. When maintenance operations are needed, only the outer protective shell needs to be opened to operate on internal fibers without disassembling the entire device. This structure is suitable for scenarios with certain protection requirements but frequent maintenance needs, such as optical cross-connect cabinets beside urban roads and community optical distribution boxes.
Installation Methods: Adapting to Different Scenario Requirements
There are various installation methods for optical fiber joint boxes, with different installation methods suitable for different scenarios. Their design needs to fully consider the characteristics and requirements of the installation environment to ensure stable operation and maintenance convenience of the device.
Wall-mounted installation is a common installation method, suitable for installation on vertical surfaces such as walls and columns. Wall-mounted joint boxes are usually designed with mounting holes or brackets on the back, fixed to walls or columns with expansion screws, bolts, and other fasteners. This installation method has the advantages of space saving, flexible installation location, and convenient maintenance, and is often used in scenarios such as internal rooms of buildings, corridor walls, and external pole sides. For example, in fiber-to-the-home projects in residential communities, wall-mounted joint boxes are usually installed on corridor walls to facilitate fiber distribution and connection. To improve installation stability, the mounting brackets of wall-mounted joint boxes are usually made of high-strength steel, capable of bearing the weight of the device and the tension of optical cables, preventing the device from loosening or falling off.
Rack-mounted installation is mainly applicable to standard 19-inch or 23-inch racks and is the most commonly used installation method in equipment rooms and data centers. Rack-mounted joint boxes are designed with standard rack mounting ears on both sides, which can accurately match the guide rails on the rack and be fixed to the rack with screws. This installation method facilitates centralized management and unified cabling of equipment, enabling it to form an organic whole with other communication equipment, improving the utilization rate and management efficiency of equipment room space. During installation, it is necessary to reasonably plan the rack space according to the height (U number) of the device to ensure sufficient heat dissipation gaps between devices, avoiding performance impact due to poor heat dissipation. Rack-mounted joint boxes are usually designed with front and rear doors or covers, facilitating operation and maintenance while providing dust protection.
Underground buried installation is suitable for underground pipeline or direct burial scenarios, which places extremely high requirements on the protective performance of joint boxes. Underground buried joint boxes need to have good waterproof, moisture-proof, pressure-resistant, and corrosion-resistant properties to withstand underground pressure, moisture, and corrosive substances in the soil. During installation, it is usually necessary to first excavate a foundation pit or lay underground pipelines, then place the joint box in it, and fill the surrounding area with sand, gravel, or concrete for fixation and protection. Some underground buried joint boxes are also designed with anti-theft functions, using special locks or fixing methods to prevent device theft. For example, the underground buried optical cable joint box from Changfei Optical Fiber is made of high-strength engineering plastics, with a shell thickness of more than 10mm, capable of withstanding a pressure of more than 2000N, suitable for urban underground communication pipe networks, highway underground optical cables, and other scenarios.
Overhead installation is suitable for connecting outdoor overhead optical cables, usually fixing the joint box to high places such as telephone poles and iron towers through hoops, brackets, and other devices. Overhead joint boxes need to have good wind resistance, earthquake resistance, and ultraviolet resistance to withstand the impact of natural factors such as wind, sunlight, rain, and temperature changes outdoors. During installation, it is necessary to consider the tension and sag of the optical cable to ensure a firm and reliable connection between the joint box and the optical cable, avoiding impact on connection performance due to cable swing caused by wind force. The installation height of overhead joint boxes is usually above 3 meters, facilitating cable laying and preventing man-made damage. For example, the overhead optical cable joint box from Fiberhome Communication is made of weather-resistant materials, capable of normal operation within a temperature range of -40℃ to +60℃, suitable for various outdoor overhead scenarios such as mountainous areas, plains, and coastal areas.
Environmental Adaptability: Ensuring Stable Operation in Complex Environments
The environmental adaptability of optical fiber joint boxes is a key indicator for measuring their ability to operate stably in various harsh environments, mainly including parameters such as operating temperature range, storage temperature range, protection level, and atmospheric pressure adaptation range.
The operating temperature range directly determines the applicability of the joint box in different climatic regions. The optical fibers, fusion components, sealing materials, etc., inside the optical fiber joint box are sensitive to temperature changes, and excessively high or low temperatures will affect the performance and service life of the device. Currently, the operating temperature range of mainstream optical fiber joint boxes in the market is usually -40℃ to +60℃, which can adapt to the low winter temperatures in cold northern regions and high summer temperatures in hot southern regions of China. The operating temperature range of joint boxes for some special environments is wider, such as those used in polar or desert regions, which can work at temperatures as low as -55℃ or as high as +85℃. This benefits from their use of high and low-temperature resistant materials such as special engineering plastics and high-temperature resistant rubber, as well as reasonable structural design, reducing the impact of temperature changes on internal components.
The storage temperature range is related to the performance stability of the device during transportation and storage. The storage temperature range of optical fiber joint boxes is usually wider than the operating temperature range, generally -40℃ to +70℃. Within this temperature range, even if the device is not used for a long time, its internal materials will not undergo obvious aging or performance degradation, ensuring that the device can work normally when put into use. This is particularly important for long-distance transportation and long-term storage of the device, especially during transportation in cold or hot regions, which can avoid device damage caused by extreme temperature changes.
The protection level is an important indicator for measuring the dust and water resistance of the joint box, usually expressed by the IP (Ingress Protection) rating. The IP rating consists of two numbers, with the first number representing the dust protection level and the second number representing the water resistance level. Common protection levels for optical fiber joint boxes are IP65, IP67, and IP68. IP65 means complete protection against the intrusion of foreign objects and resistance to low-pressure water spraying; IP67 means complete protection against the intrusion of foreign objects and being immersible in water at a depth of 1 meter for 30 minutes without water ingress; IP68 means complete protection against the intrusion of foreign objects and being immersible in water at a certain depth for a long time without water ingress. For example, some optical cable joint boxes from Changfei Optical Fiber have a protection level of IP68, capable of being used for a long time at a water depth of 2 meters, suitable for areas with high groundwater levels or underwater optical cable connection scenarios. The achievement of high protection levels benefits from advanced sealing technologies such as multi-layer rubber sealing rings, mechanical sealing structures, and heat-shrinkable sealing sleeves, which can effectively block the intrusion of moisture and dust.
The atmospheric pressure adaptation range ensures the normal operation of optical fiber joint boxes in environments with different altitudes. Atmospheric pressure decreases with increasing altitude, which may cause a pressure difference between the inside and outside of the joint box, affecting sealing performance. Mainstream optical fiber joint boxes can usually adapt to an atmospheric pressure range of 70kPa to 106kPa, covering areas from sea level to an altitude of about 3000 meters, meeting the needs of most regions in China. For high-altitude areas (such as the Qinghai-Tibet Plateau above 3000 meters above sea level), specially designed high-altitude joint boxes are required. These products can balance the pressure difference between the inside and outside through special structural designs such as pressure balance valves, ensuring sealing performance and operational stability in low-pressure environments.
Materials and Processes: Determining Device Performance and Service Life
The materials and processes of optical fiber joint boxes directly affect their mechanical properties, protective performance, and service life, serving as the core guarantee of device quality.
The selection of shell materials needs to comprehensively consider mechanical strength, corrosion resistance, weather resistance, and cost. Currently, common shell materials in the market mainly include reinforced plastics and metals. Reinforced plastics such as ABS engineering plastics, polycarbonate (PC), and glass fiber-reinforced polypropylene have the advantages of light weight, corrosion resistance, good insulation performance, and relatively low cost, and are widely used in optical fiber joint boxes in general environments. For example, many joint box products from Hong'an Communication are made of ABS engineering plastics, with impact strength reaching over 20kJ/m² after being reinforced with glass fibers, meeting the needs of conventional installation and use. Metal materials such as aluminum alloys and stainless steels have higher mechanical strength and impact resistance, and excellent anti-electromagnetic interference performance, and are often used in scenarios with high protection requirements such as wild, mountainous, and coastal harsh environments. Aluminum alloy materials can effectively improve their corrosion resistance through surface anodizing treatment; stainless steel materials have natural corrosion resistance, suitable for environments with high salt spray concentrations such as seaside areas. For example, some metal shell joint boxes from Changfei Optical Fiber are made of 304 stainless steel, with salt spray resistance reaching more than 5000 hours, capable of long-term stable use in coastal areas.
Sealing technology is a key process for ensuring the protective performance of optical fiber joint boxes, currently mainly including rubber sealing, heat-shrinkable sealing, and mechanical sealing methods. Rubber sealing is the most commonly used sealing method, achieving sealing by arranging rubber sealing rings at the joints of the shell and using the pressure from bolts or buckles to elastically deform the sealing rings. Rubber sealing rings are usually made of ethylene-propylene-diene monomer (EPDM) or silicone rubber, with good high and low-temperature resistance, aging resistance, and elasticity. Heat-shrinkable sealing forms a seal by heating the heat-shrinkable sleeve to make it shrink and tightly wrap around the connection between the optical cable and the joint box. Heat-shrinkable sealing has the advantages of good sealing performance and simple operation, suitable for sealing various types of optical cables. Mechanical sealing is an advanced sealing method that achieves sealing through pressure generated by mechanical structures. Some joint boxes adopt re-openable mechanical sealing structures, facilitating maintenance and reuse, and effectively reducing maintenance costs. For example, the optical cable joint box from Fiberhome Communication adopts patented mechanical sealing technology, which can be re-opened more than 50 times, and the sealing performance can still maintain the IP68 level.
Internal structural processes are also crucial for device performance. Optical fiber joint boxes usually contain components such as fiber fusion trays, winding posts, and adapter mounting plates, and the processing technology and assembly accuracy of these components directly affect the management and protection effect of optical fibers. The fiber fusion tray is a key component for storing fiber fusion points, and its surface is usually manufactured using precision injection molding technology to ensure that the bending radius of the optical fiber meets the standard (generally not less than 30mm), avoiding signal loss caused by excessive bending. The design of winding posts needs to be smooth and rounded to prevent optical fibers from being scratched during winding. The adapter mounting plate needs to ensure the installation accuracy of adapters, ensuring accurate docking of optical fiber connectors and reducing insertion loss. Many manufacturers adopt modular assembly processes, pre-assembling internal components into modules, improving production efficiency and assembly accuracy, and facilitating later maintenance and upgrading.
Surface treatment processes can improve the weather resistance and aesthetics of optical fiber joint boxes. For plastic shells, surface spraying or electroplating processes are usually used to improve their ultraviolet resistance and anti-aging performance; for metal shells, anodizing, electroplating, painting, and other processes are used to improve their corrosion resistance and decoration. For example, after anodizing treatment, the surface of the aluminum alloy shell joint box forms a dense oxide film, which not only improves corrosion resistance but also has good insulation performance.
Mechanical Properties: Resisting External Physical Impacts
Optical fiber joint boxes are subject to various external forces during installation, transportation, and use, so they must have good mechanical properties to protect internal optical fibers from damage and ensure connection stability.
Crush resistance is an important indicator for measuring the joint box's ability to resist external extrusion. During installation and use, joint boxes may be subject to external extrusion forces such as soil pressure, vehicle rolling, and heavy object stacking. If the crush resistance is poor, it may cause internal fiber breakage or increased signal loss. Mainstream optical fiber joint boxes can withstand pressures above 2000N/100mm, and some underground buried joint boxes have even higher crush resistance, up to more than 3000N/100mm. For example, during the crush test of the optical cable joint box from Changfei Optical Fiber, it can withstand a pressure of 2000N for 1 minute, with the additional loss of internal fibers not exceeding 0.1dB, ensuring stable signal transmission under pressure. This benefits from its sturdy shell design and internal reinforcement structure, with the shell made of high-strength materials and internal reinforcing ribs or support structures arranged to effectively disperse external forces and protect internal fibers.
Optical cable tensile performance is a key indicator for ensuring the firmness of the connection between the joint box and the optical cable. During cable laying and use, the joint box may be subject to axial tension. If the tensile performance is poor, it may cause the connection between the joint box and the cable to loosen, or even internal fibers to break. Optical fiber joint boxes can usually withstand an axial tension of not less than 800N, and some high-strength joint boxes have tensile performance of more than 1500N. This is achieved by arranging cable fixing devices inside the joint box, such as cable strength member fixing seats and cable clamping devices, which can evenly distribute the tension of the cable to the joint box shell, avoiding tension transmission to internal fibers. For example, the optical cable joint box from Zhongtian Technology uses a double-screw clamping device to fix the cable, which can effectively withstand an axial tension of 1000N, ensuring connection firmness.
Optical cable bending performance measures the ability of the joint box to adapt to cable bending changes. During cable laying and use, the cables at both ends of the joint box may bend. If the bending performance is poor, it may cause excessive fiber bending and signal loss. Optical fiber joint boxes can usually withstand a bending test of 10 cycles with a bending tension of 150N and a bending angle of ±45°, with the additional loss of internal fibers not exceeding 0.1dB after the test. This benefits from the reasonable internal fiber routing design and cable introduction structure of the joint box. The cable introduction part usually adopts an arc transition design to avoid stress concentration when the cable is bent. At the same time, the management of internal fiber slack is also important, and appropriate slack can buffer the tension generated when the cable is bent, protecting the fiber from damage.
Impact resistance measures the ability of the joint box to resist external impacts. During transportation, installation, and use, the joint box may be subject to impacts such as collisions and drops. Poor impact resistance may cause shell and internal component damage. Optical fiber joint boxes can usually withstand an impact test with an energy of 10J, with no shell and normal internal fiber connection after the test. This benefits from their use of high-strength materials and reasonable structural design, with the shell usually designed with reinforcing ribs and corners adopting rounded transitions to disperse impact energy and reduce local stress concentration.
Electrical Performance and Service Life: Ensuring Long-term Reliable Operation
Although optical fiber joint boxes are mainly used for optical signal transmission, their electrical performance needs to be considered in some scenarios, and the service life of the device is also an important indicator for measuring its economy and reliability.
Withstand voltage strength is an important electrical performance of optical fiber joint boxes, representing the device's ability to resist voltage impacts. In some special scenarios, such as fiber and power lines sharing poles and being close to high-voltage substations, the joint box may be affected by induced voltage or lightning overvoltage. Joint boxes with certain withstand voltage performance can prevent high-voltage breakdown, protecting internal fibers and equipment safety. Some optical fiber joint boxes have a withstand voltage strength of up to 15kV (DC) or more. During the withstand voltage test, a DC voltage of 15kV is applied for 1 minute without breakdown or arcing. This is achieved by arranging insulation isolation structures and grounding devices inside the joint box, with the selection of insulation materials and the design of insulation distances meeting relevant standard requirements.
Insulation resistance is also an important electrical performance indicator, representing the insulation ability between the joint box shell and internal metal components. The insulation resistance of optical fiber joint boxes is usually not less than 1000MΩ (measured under 500V DC). Good insulation performance can prevent electric leakage and electric shock accidents, ensuring safe operation of the device. This mainly depends on the insulation performance of the shell material and the design of the internal insulation structure. Reinforced plastic shells themselves have good insulation performance, while metal shells need to achieve insulation through internal insulation gaskets or coatings.
The service life of optical fiber joint boxes is mainly determined by material aging life and structural life, usually measured by material aging life. Due to the difficulty and high cost of replacing joint boxes after installation, high requirements are placed on their service life. Currently, the material aging life of mainstream optical fiber joint boxes in the market is generally more than 20 years, and some high-quality products have a service life of up to 25 or even 30 years. This benefits from their use of anti-aging materials and advanced manufacturing processes, with shell materials usually added with antioxidants, ultraviolet absorbers, and other additives to delay material aging; internal rubber sealing rings, adhesives, etc., also use products with good anti-aging performance. For example, the optical cable joint box from Changfei Optical Fiber has passed strict accelerated aging tests, and after 1000 hours of testing in an environment of 70℃ high temperature and 95% relative humidity, various performance indicators still meet the requirements, and its actual service life is estimated to be more than 25 years. The long-life design reduces the cost and workload of frequent equipment replacement, ensures long-term reliable operation of the optical fiber network, and provides a strong guarantee for the stability of the communication network.
