The present invention relates in general to the optical fiber unit (cable) for air blown installation or Drop cable for wall mount or aerial Installation and in particular, to a new protecting method for optical fiber by composition in which the optical fiber is integrated in FRP (Fiber Reinforced polymer) or (located in the cross section of (FRP).
Coated optical fibers are widely used in the communications field because of their ability to carry large amounts of information over long distances. As shown in
There have been two major categories of fiber optic shielding. In the first type, which is called Loose-Tube, as shown in
In the second type, which is called Tight-Buffer, as shown in
Using different elements in different parts of the cable, each of which has a separate role, such as aramid fibers, FRP as central strength member, moisture-proof tape, independent protective covers for each optical fiber in various types of Tight-Buffer cables, and protective tube with antifreeze gel in all types of Loose-Tube cables has drawbacks. These components do not fit perfectly together with geometric shapes, eventually the diameter of the final cable increases according to the required mechanical and temperature resistance, and this increase in diameter is also effective on the following factors:
The cost of goods related to cable installation is greatly increased in executive projects for the installation of optical cables such as ducts and micro ducts. Costs related to ground drilling, overwork and rehabilitation of drilled land increase due to the increase in duct diameter. The cost of municipal fines increases with increasing drilling width. Increasing the weight and volume of the cable as well as increasing the volume of excavation drastically reduces the speed of the operation. Due to the increase in the weight of the unit length and also the increase in the diameter of the cable, there is a great limitation regarding the number and capacity of aerial cables that can be installed on the transmission and lighting beams.
Due to the mentioned problems regarding the low number of optical fibers in optical cables in relation to the high diameter of the cable, a new subset of Tight-Buffer cables called ribbon cables was developed.
In Tight-Buffer cables, each fiber was covered separately with a polymer (plastic) coating as a separate optical fiber, but in Ribbon cables, as shown in
The optical fiber is grouped in the form of a regular cross-section, and a layer of ribbons is placed in the cable protection structure and protected by various elements such as waterproof tape 220, FRP 250, plastic regulatory structures 230, final outer jacket 240 and ripcord 260 for easy outer jacket separation. In this type of cable, a plurality of elements are provided to protect the optical fiber, which makes the production process very complicated and includes a large volume of the cross-section of the cable. The final weight of the optical cable is extremely high.
Ribbon cable design has reduced the cross-sectional area of optical cables to a very limited extent, but this design has faced limitations and shortcomings. Due to the limited and predetermined shape of each ribbon, in practice in single-strip cables, the geometric shape of the cable cross-section is not circular, and this deformation prevents the use of this cable in ducts or aerial installation. if the shape of the cross-section of the cable changes to a circle large space of the cable remains unused. Almost all the previous elements of Tight-Buffer cables such as plastic sheath, FRP, aramid fibers, and moisture-proof tape are also present in Ribbon cables, which eventually lead to an increase in cable diameter, price, and weight.
To protect the fibers from physical damage during installation and also to protect from the physical and chemical effects of the installation environment, it is conventional to apply protective coatings to the freshly drawn fibers part of the optical cable production process. The normal method of installation is direct cable installation in the ground or aerial installation that involves pulling the fibers along previously laid cable ducts with the aid of ropes in this method to avoid damage, it is necessary to cover jacket the fibers with an expensive material.
To avoid these problems, it has been proposed in EP0108590 to propel the fiber along a tubular pathway by the fluid drag of a gaseous medium passed through the pathway in the desired direction in advance. In other words, the fibers, usually in sheathed multiple bundles, are blown into place on a cushion of air. By using this technique, it is possible to “blow” optical fiber cable along micro ducts for long distances (several kilometers) without damage.
Fibers suitable for blowing require packaging which is cheaper and simpler than normal cable structure. A number of designs are known; in EP0521710A1, EP0296836A1, U.S. Pat. Nos. 5,555,335, 7,397,990, 7,623,748, 5,533,164. These patents disclose optical blowing cables try to fit more optical fibers in less space and provide more physical protection for them. In the first step the optical fibers are surrounded by UV-curable (silicone-acrylate) resin to protect the optical fiber, and after that, they use another type of UV-curable resin or thermoplastic polymer to cover, integrate, and make more protection in each layer and finally try to design a new structure that helps blowing performance.
Based on the listed prior art in the previous section and all other similar patents, the use of thermoplastic polymers and resin polymers as optical fiber protection alone, is not able to create a cable resistant to all mechanical pressures. The cable produced according to the third method, despite the reduction in diameter and increase in the density of optical fibers in the cross-sectional area, is too sensitive and non-resistant, and the operational implementation of such cables in executive projects faces many problems.
The present invention aims to provide enhanced mechanical protection for optical fibers in optical cable manufacturing. The process involves multiple stages, each contributing to the overall protection and durability of the optical fibers. In the initial stage, each optical fiber undergoes a coating process with UV-curable resin, a common practice in previous patents. This coating results in an outer diameter for each optical fiber ranging from 180 to 250 microns.
Moving to the second stage, a fiber-reinforced resin (FRP) is applied to all or part of the cross-section of the optical fiber. The curing of this FRP is achieved through a UV Pultrusion process. This innovative step introduces a composite material that surpasses the mechanical properties of conventional resin-only materials, providing superior protection for the optical fiber.
In the third and final stage, the composition created in the second stage is further safeguarded by covering it with plastic polymers such as PVC, Polyamide, Polyurethane, Polyethylene, or any other suitable plastic material. In this process, optical fibers initially receive a protective layer of colored UV-curable (silicone-acrylate) resin. Unlike conventional methods, at least one optical fiber is strategically placed on the cross-section or outer surface of an FRP cylindrical shape (or any other geometric or non-geometric shape) during the Pultrusion process. This ensures that all or part of the optical fiber's cross-section is embedded within the FRP cross-section.
Contrary to traditional practices involving just curable resin or thermoplastic polymer as second and third layer protection (EPFU), this innovation employs a method where 1 to 24 optical fibers are collectively covered with colored acrylic, colored silicone coating, or any other similar protective coating. These optical fibers are situated on the cross-section or outer surface of an FRP cross-section, created through the Pultrusion process.
The diameter of the FRP cylindrical shape can range in various diameters. Each FRP, housing the optical fibers, is termed an optical composite unit (OCU). These units are then coated with a plastic layer. The units can be coated with multilayers of thermoplastic polymer. Although some units may remain uncoated.
Multiple optical composite units can be arranged next to each other, forming an optical cable with varying capacities. Each optical composite unit's dimensions and cross-sectional shape can be tailored to any geometric or non-geometric form, ensuring the absence of empty spaces between units in the cable. The placement and number of optical fibers within each unit can be adjusted according to specific application requirements and mechanical resistance parameters.
In instances where optical fiber connections are necessary, the reinforced fiber can be separated, breaking the FRP structure. This action makes the optical fibers accessible for stripping and fusion processes.
Therefore, it is an object of the present invention to use fiber-reinforced resin polymer instead of resin or thermoplastic polymer alone or resin combined with particles to cover the optical fiber.
It is another object of the present invention to provide an improved structure for the optical fiber unit (cable) that is suitable for blowing and use as drop wire(cable) in the FTTX network and improved resistance to fiber break-out.
It is another object of the present invention that in comparison with conventional cables more optical fibers are placed in the same cross-section, thereby the density of optical fibers in the cross-section of the cable will be increased significantly and reduce the diameter of optical cables while maintaining a large capacity, which will reduce the cost of running optical cable installation projects many times over.
It is another object of the present invention that since a very high percentage of the cable cross-section is FRP, it provides higher protection for the optical fiber and greatly increases the parameters of mechanical strength, temperature resistance, and moisture resistance of the optical cable.
It is another object of the present invention to reduce the cost of producing fiber optic cable by reducing raw materials consumption, removal of many elements that are used in conventional cables, and reducing the number of production processes.
It is another object of the present invention to use fiber-reinforced UV-curable resin instead of thermoset resin and thereby, remove the need of special heat protection layer for optical fiber and increase the production speed significantly.
Embodiments herein will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the scope of the claims, wherein like designations denote like elements, and in which:
Fiber optic cables are normally produced with low fiber optical core density to cable cross-section ratio especially in low-capacity cable for 1 to 24 cores. These cables have high cable cross-section and high cable weight when a high mechanical performance for cable is required. These cables have a high-cost multi-stage and intensive production process, a high cost of installation based on the size of cable diameter, and a high cost of installation based on the weight and high volume of the cable.
To solve these problems the EPFU (Enhanced Performance Fiber Unit) optical cable was invented (
To achieve a perfect structure with high physical resistance parameters and a high fiber density, the present invention uses a type of raw material that simultaneously protects the optical fiber and creates a suitable mechanical strength for the cable. The present invention uses composite materials instead of the usual polymers that have low weight and very high mechanical strength. Location and geometric dimensions of different parts of the cable should be such that there is at least unusable space between the components of the cable. The production process should be simple so that the cable is fully produced in one stage of production. The structural components of each unit of the present invention comprise:
In this method, at least one optical fiber 3 in the first stage is located on the cross-section or outer surface of a cylindrical shape that is made of FRP composite (Fiber Reinforcement polymer) 2 in a way that all or part of the optical fibers 3 are placed in the cross-section of FRP cross-section.
According to
According to
The configuration of the FRP cross-section, along with the positioning of the optical fibers coated with silicone-acrylic resin within the FRP cross-section, is dictated by the forming mold. The FRP can assume a geometric or non-geometric cross-section in any desired shape. This flexibility allows for the alteration of the cross-section shape and dimensions, enabling the creation of varied mechanical characteristics for the optical fiber unit. The composite generated after the second stage of production is termed the Optical Composite Unit (OCU).
The optical composite unit (OCU) is coated with a layer of polymers like PVC, Polyamide, Polyurethane, Polyethylene, or any other thermoplastic by extrusion process. The thickness and type of polymer that is used are related to the mechanical properties that are needed for the optical fiber cable. The number of Optical Composite Units (OCUs) coated with polymer coating depends on the required capacity and mechanical characteristics of the produced optical fiber unit (cable). In most cases, just one OCU with thermoplastic polymer coating can be used as a simple and low-diameter micro-optical cable for air-blowing installation. When a portion of the cross-section of the coated optical fiber is positioned in the cross-sectional area of the FRP, the coated optical fibers can be manually peeled away from an element without fracturing the FRP structure. However, if the entire cross-section of the optical fiber is situated in the cross-sectional area of the FRP, it becomes necessary to fracture the FRP structure to access the optical fiber.
In contrast to traditional methods, at least one optical fiber is strategically placed on the cross-section or outer surface of a cylindrical shape FRP (or any other geometric or non-geometric shape) during the Pultrusion process. This placement ensures that all or part of the optical fiber's cross-section is embedded within the FRP cross-section.
Contrary to traditional practices involving individual plastic coverings for each optical fiber (Tight-Buffer), this innovation employs a method where 1 to 24 optical fibers are collectively covered with colored acrylic, colored silicone coating, or any other protective coating are situated on the cross-section or outer surface of an FRP cross-section, created through the Pultrusion process.
The diameter of the FRP cylindrical shape can be in various range. Each FRP, housing the optical fibers, is termed an optical composite unit (OCU). These units are then coated with a plastic layer with a thickness. Although some units may remain uncoated.
Multiple optical composite units can be arranged next to each other, forming an optical cable with varying capacities. Each optical composite unit's dimensions and cross-sectional shape can be tailored to any geometric or non-geometric form, ensuring the absence of empty spaces between units in the cable. The placement and number of optical fibers within each unit can be adjusted according to specific application requirements and mechanical resistance parameters.
The combination of FRP and fiber optics has a very similar homogeneity and physical composition. As a result of this integration, the force due to compression, bending, and tension is spread evenly over the cross-sectional area, and the length of the cable reduces its point effect to a minimum and ultimately leads to a lack of stress concentration at one point. Thereby, force is distributed at all levels of each optical composite unit. This will eventually lead to a very high increase in cable physical endurance.
In another embodiment to create optical cables with more capacities, 1 to 24 (or more) composite units are placed next to each other without the need for other physical reinforcing elements that are normally used in optical cables and finally covered with plastic with or without metal sheath.
A larger number of optical fibers compared to Tight-Buffer cables as well as Loose-Tube cables have been placed in the same cross-sectional area to significantly increase the density of optical fibers in the cross-sectional area of the cable. These cables reduce the diameter of optical cables while maintaining a large capacity, which will reduce the cost of running optical cable installation projects. The cable cross-section's substantial composition of Fiber-Reinforced Polymer (FRP), characterized by its outstanding physical properties often surpassing those of metals, yields superior advantages compared to other plastics utilized in Tight-Buffer and loose-tube configurations. The present invention provides more optical fiber in less diameter by the same mechanical property that is used in the traditional optical cables.
In the present invention, the coating significantly enhances the protection of the optical fiber and elevates the mechanical strength, temperature resistance, and moisture resistance parameters of the optical cable, resulting in the following benefits which have been approved by experimentations:
The current invention extends the range of air-blowing Fiber cable over long distances in both ground and aerial micro-ducts. The substantial FRP content in each composite unit, occupying a large percentage of the cable's total cross-section, endows the produced cable with exceptionally high elasticity, significantly enhancing the cable's ability to navigate through ducts and micro-ducts.
This cable manufacturing method reduces cable diameter by eliminating elements utilized in conventional cables to increase physical strength or resistance to water penetration. In this cable, the use of FRP wire covering units negates the need for a composite non-metallic intermediate element (FRP) to provide elastic properties and increase tensile strength. The cable achieves elasticity and tensile strength beyond conventional standards through the FRP-made wire covering units.
Elimination of the need for moisture-proof tape is another noteworthy aspect, as the impermeability of FRP to water obviates the necessity for additional measures. Given the high FRP percentage in the cable, tensile strength is predominantly provided by FRP, surpassing standard requirements, and rendering the addition of aramid fibers unnecessary.
The present invention significantly reduces the costs associated with optical cable installation operations. The reduction in cable diameter, and subsequently, the diameter of ground ducts used for cabling, leads to diminished transportation costs for cables and ducts, decreased drilling costs, and reduced expenses for the repair and reconstruction of drilled routes.
Furthermore, the invention reduces cable diameter and the number of elements within the cable, resulting in a substantial decrease in weight per length unit of cable. This reduction enhances the capacity of aerial ducts with high weight limits.
The invention increases the cable's blowing capabilities over much longer distances compared to conventional cables in aerial and ground ducts, thereby reducing network development and maintenance costs.
Additionally, the invention diminishes drilling volume, cable and duct weight, and the volume and space requirements of drilling and transportation equipment. Consequently, the reduced staff requirements for the executive group enable optical cable installation in busy roads and narrow passages.
Manufacturing cables utilizing optical composite units opens up a range of versatile applications:
The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
With respect to the above description, it is to be realized that the optimum relationships for the parts of the invention in regard to size, shape, form, materials, function, and manner of operation, assembly, and use are deemed readily apparent and obvious to those skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.
Number | Date | Country | Kind |
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PCT/IR2020/050023 | Jul 2020 | WO | international |
This application is a continuation-in-part of U.S. application Ser. No. 17/627,443 filed on Jan. 14, 2022. The application is incorporated herein by reference in its entirely.
Number | Date | Country | |
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Parent | 17627443 | Jan 2022 | US |
Child | 18639009 | US |