The rapid development of metropolitan area network and access network will increase the demand for optical fiber. The ribbon optical cable will be widely used because of its high fiber integration and low laying cost. How is the central bundle tube type ribbon cable designed? What are the effects of process parameters on the performance of ribbon cable in the manufacturing process?
At present, the construction of optical fiber network is gradually turning from national backbone network to regional network and man access network. In optical fiber man and access network, due to the connection of many nodes, it is often necessary to lay large number of fiber optic cables. However, the ribbon optical cable has many advantages: the integration degree of the optical cable, that is, the same fiber core can make the optical cable structure smaller and occupy less routing resources; Reduce the cost of optical fiber fusion and improve the installation efficiency; due to the decrease of optical fiber cost, the cost of ribbon cable is reduced; with the progress of optical fiber belt and optical cable manufacturing technology, the fiber loss of ribbon cable is basically similar to that of ordinary bulk fiber cable; optical fiber ribbon has better mechanical performance than optical fiber.
In foreign countries, ribbon optical cable is widely used in long-distance trunk line of optical cable, while in metropolitan area network of large and medium-sized cities in China, ribbon optical cable is widely used. According to its structure, ribbon optical cable has central bundle tube type, layer stranded type and skeleton type structure. Due to its good lateral pressure resistance and bending performance, the central bundle tube type ribbon optical cable has the largest number of fiber cores per unit area, that is, the same size of the overall size of its fiber core number is the largest, stripping and access efficiency is high, which is widely used at home and abroad.
Design of central bundle tube ribbon optical cable
The design of ribbon optical cable is mainly based on the number of fiber core and the characteristics of application environment to carry out the structure design and material selection of optical cable, so that the cable has good mechanical and environmental performance in the life cycle. Ensure that the transmission performance of optical fiber remains unchanged during its laying and operation. The design of optical cable includes the design of optical fiber core, the design of strengthening unit of optical cable, the design of optical cable structure and the selection of optical cable material. Since the ribbon optical cable is more than the man and access network, the size of optical cable should be reduced as much as possible to make up for the limitation of urban optical cable routing resources (pipeline or overhead), that is, the optimized design of optical cable should make the number of optical fiber cores per unit cross-section area of optical cable be the largest, but at the same time, it can ensure that It is proved that the optical cable has good mechanical and environmental performance.
Design of optical cable core
The core of the central bundle tubular ribbon optical cable is the basis of the whole optical cable design, which mainly plays the role of protecting the optical fiber, Optical fiber jumper production equipment 。 When the fiber ribbon is subjected to side pressure, it can play a good buffer effect. The design mainly determines the cable core size according to the fiber belt size and core number, i.e. the inner diameter, thickness and outer diameter of the cable core, and verifies that the curvature radius of the optical fiber can not cause the increase of fiber loss according to the manufacturing pitch and control surplus length of the optical fiber belt in production
Optical fiber jumper production equipment
Among them: you see Parameters of OPGW optical cable 。 W-band width, n-fiber number, t-ribbon thickness, di-inner diameter of optical cable core tube
The thickness of the core tube of the optical cable can be selected from 0.7 mm to 1.5 mm according to the number of optical fiber belts. Therefore, the outer diameter of the core tube: do (2 * (0.7-1.5) + ((W2 + (NT) 2) / 0.8 -- (2)
According to formula (1) and (2), the width and overlapping thickness of the fiber ribbon arrangement (w * nt) should be equal to make the core tube size smallest and the fiber belt filling degree maximum. According to this, the type of optical fiber belt in the core tube can be selected. Generally, the number of optical fiber cores commonly used is 6 cores, 12 cores or 24 cores.
According to the above relationship, the relationship between the maximum inner diameter of the core tube and the total number of cores and the type of optical fiber ribbon can be obtained
The relationship between the maximum inner diameter of core tube and the total number of cores and the type of optical fiber ribbon
Design of optical fiber reinforced unit
The strengthening unit of optical cable can be divided into metal reinforcement and non-metallic reinforcement according to different application environment of optical cable. The mechanical tension of optical cable in the process of laying and application is mainly borne by the strengthening unit, so the design and calculation of reinforcement unit and the selection of reinforcement material are very important. Compare it Corning fiber jumper 。
The relationship between the strain of optical fiber and the length of optical fiber cable can be referred to in the figure below. Generally speaking, it is a reasonable range for the strain of optical cable to be between 0.3% and 0.4%, and that for optical fiber from 0.05% to 0.25%, while it is more reasonable to control the excess length under 0.15%.
Optical cable structure design
After determining the core tube and strengthening unit of the optical cable, the structure design of the optical cable can be carried out, including the selection and size determination of water blocking material, armor layer and sheath material. in fact Optical fiber jumper production equipment 。 There are two commonly used cable structures for central bundle tube type ribbon optical cable: one is to use two parallel strengthening units, which are more suitable for ribbon optical cables with less than 216 cores, including metal reinforcement and non-metallic reinforcement; the other is to adopt the stranded structure of reinforced unit, including metal and non-metallic reinforced stranding structure Corning Cable System 。 This kind of structure is often used in the optical cables with 216 cores or more, especially the non-metallic stranded structure layer, which not only plays an important role in the tension resistance of the optical cable, but also enhances the lateral pressure resistance of the cable core, and plays a good protection role for the optical fiber belt and core tube. The external flame retardant sheath can be laid in the same trench with power pipeline in man, which has a broad application prospect.
Structure comparison with layer twisted ribbon optical cable
The most important task of optical cable structure design is to ensure that the transmission performance of optical fiber is basically unchanged when external forces and environment change, that is, all optical cable structure design is focused on how to better protect optical fiber. For ribbon fiber optic cable, the corner fiber of ribbon fiber is the most vulnerable to external force and environmental changes For the central bundle tube type, no matter how many fiber cores, there are always four corner fibers in the fiber belt, while there are four edge angle fibers in each sleeve of the layer stranded optical cable. With the increase of the number of fiber cores, the edge angle fibers will increase. Therefore, the possibility of micro bending loss caused by compressive stress on these corner fibers in the process of casing stranding or laying is increased.
Compared with the layer stranded optical cable structure, the central bundle tube type ribbon cable has better lateral pressure resistance and bending performance because the fiber belt is located in the center of the optical cable. At the same time, it has the largest number of fiber cores per unit area, that is, high fiber integration, light weight, small structure size, capacity stripping, which can save routing resources and facilitate construction.
Technology and performance optimization of ribbon optical cable
The manufacturing process of ribbon optical cable is the concrete realization of optical cable design. Good manufacturing equipment and process tooling design must achieve the following main purposes: the process of fiber ribbon manufacturing increases the minimum loss; the fiber with appropriate excess length makes the optical cable have good mechanical properties; the cable has good temperature characteristics, namely high and low temperature performance.
The quality of optical cable comes from the manufacturing quality of the process rather than inspection. Therefore, the comprehensive performance of optical cable must be achieved through process optimization design, that is, it has good process additional loss, mechanical properties and temperature characteristics. In the manufacturing process of ribbon cable, the pay off tension and pitch of optical fiber belt, the temperature of filling ointment and the control of excess length of optical fiber belt are the key process parameters. Especially when the surplus length is produced by mechanical traction on the production line, the tension must be strictly optimized to control the fiber excess length. In practice, the process parameters can be optimized by orthogonal experimental design method, so as to achieve the purpose of optical cable performance optimization.
Central bundle tube type ribbon optical cable has high optical fiber integration and good comprehensive mechanical properties, especially lateral pressure resistance and bending performance. It is widely used in metropolitan area network and access network. In the design of central bundle tube ribbon cable, the design of cable core structure and the design and selection of strengthening unit are very important. There are two main structures of central bundle tube ribbon optical cable, and the selection of their structures is feasible It depends on the application environment and the number of optical fiber belts; the manufacturing process of optical cable has a great impact on the performance of optical cable. After the design of optical cable is determined, the manufacturing process of optical cable must be optimized in order to make the ribbon cable have good transmission performance, mechanical performance and environmental performance, that is, the optimized design of optical cable must be realized through optimized manufacturing process.