The disclosure relates generally to bundled drop assemblies including optical fibers, and specifically to bundled drop assemblies in which subunits are annealed after being wound around an underlying central member or layer of subunits. Optical fibers are used to transmit data optically between various points in a network. Such optical fibers may be arranged in cables originating at data hubs, and the cables may include branches that drop at various locations to deliver data to nodes in the network. A variety of cable designs exist that provide such branching within a telecommunications network.
According to an aspect, embodiments of the disclosure relate to a bundled drop assembly. The bundled drop assembly includes a central member and a first layer of subunits wound around the central member in a bundled configuration. The first layer of subunits has at least one subunit containing at least one first optical fiber, and the first layer of subunits has a first maximum cross-sectional dimension in the bundled configuration. In an unrestrained configuration, the first layer of subunits has a second maximum cross-sectional dimension that is less than twice the first maximum cross-sectional dimension.
According to another aspect, embodiments of the disclosure relate to a method of preparing a bundled drop assembly. In the method, a first layer of subunits is wound around a central member into a bundled configuration. Each subunit of the first layer of subunits includes a first subunit jacket, and at least one subunit of the first layer of subunits contains an optical fiber disposed with the first subunit jacket. The first layer of subunits is annealed by heating each first subunit jacket to a temperature of at least 60° C.
According to a further aspect, embodiments of the disclosure relate to a bundled drop assembly that includes a central member, a first layer of subunits wound around the central member, and at least one further layer of subunits wound around the first layer of subunits. Each subunit of the first layer of subunits has a first subunit jacket, and at least one subunit of the first layer of subunits contains an optical fiber disposed within the first subunit jacket. Each subunit of the at least one further layer of subunits has a further subunit jacket, and at least one subunit of the at least one further layer of subunits contains an optical fiber disposed within the further subunit jacket. The at least one further layer of subunits is an outermost layer of the bundled drop assembly. One or both of the first subunit jackets or the further subunit jackets is annealed such that a residual unwinding force is less than 1000 g.
Additional features and advantages will be set forth in the detailed description that follows, and, in part, will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims.
The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and the operation of the various embodiments.
Referring generally to the figures, various embodiments of a bundled drop assembly having annealed subunits are provided. As will be discussed more fully below, the bundled drop assembly includes a central member around which at least one layer of subunits is wound, and upon forming the layer of subunits around the central member, the subunits are annealed to relieve the stress developed in the subunits during winding. In this way, the subunits do not spring apart from the central member when the bundled drop assembly is terminated or accessed at a midspan location. Further, the method of annealing the subunits eliminates any requirement of a binder wrap or glue to keep the subunits wound around the central member, and the annealed subunits can be wound at longer laylengths, which enhances the processing speed for producing a bundled drop assembly. Exemplary embodiments of the bundled drop assembly and method of manufacturing same will be described in greater detail below, and these exemplary embodiments are provided by way of illustration, and not by way of limitation.
In the embodiment depicted, the subunits 12 are optical fiber drop cables 18. As can be seen in
In the embodiment depicted, the subunits 12 include a layer 30 of strengthening yarns disposed around the buffer tube 20, and a subunit jacket 32 is provided around the layer 30 of strengthening yarns. In embodiments, the layer 30 of strengthening yarns may include a water-blocking feature, such as water blocking yarns or tape, or the strengthening yarns may be dusted with superabsorbent polymer powder. In embodiments, the layer 30 of strengthening yarns may include yarns of aramid, glass, cotton, or basalt, among others. The subunit jacket 32 includes an interior surface 34 and an exterior surface 36. In embodiments, the interior surface 34 is in contact with the layer 30 of strengthening yarns. Further, in embodiments, the exterior surface 36 is the outermost layer of the subunit optical fiber drop cable 18. In embodiments, the subunit jacket 32 is made of a low-shrink polymer composition containing a polyolefin, a thermoplastic elastomer, and a high-aspect ratio inorganic filler. Further, in certain embodiments, including the embodiment shown in
In the optical fiber drop cable 10, the subunits 12 are arranged in one or more layers around the central member 14. In the embodiment depicted, the subunits 12 are arranged in a first layer 40 and a second layer 42 around the central member 14. In the embodiment depicted, the first layer 40 is an inner layer, in particular the innermost layer, wrapped around the central member 14, and the second layer 42 is an outer layer, in particular the outermost layer, wrapped around the subunits 12 of the first layer 40.
In the embodiment depicted in
As can be seen in
Advantageously, because the subunits 12 are not surrounded by a cable jacket, dropping subunits 12 from the bundled drop assembly 10 is less time and labor intensive that opening a jacketed optical fiber cable at a splice or drop location. Instead, the subunits 12 are configured to drop from the bundled drop assembly 10 at various locations along the length of the bundled drop assembly 10. For the optical fiber drop cables 18, dropping off subunits 12 allows for delivery of optical signals through the optical fibers 28 to installations at the drop locations.
While the embodiment depicted shows only subunits 12 that are optical fiber drop cables 18, in other embodiments, the subunits 12 may be a mix of optical fiber drop cables 18, electrical conductor cables, and/or filler units. In embodiments, the electrical conductor cables include one or more wires contained in a subunit jacket configured to carry electrical current, and the electrical conductor cables can drop from the bundled drop assembly 10 at various locations to deliver electrical power to installations at the drop locations. In embodiments, the filler units are cords of solid or foamed polymeric material, which may be formed around one or more strengthening yarns. The filler units may be used to provide a complete layer of subunits 12 if not all subunit positions are needed for optical fiber drop cables 18 or electrical conductor cables. Additionally, in embodiments, the filler units may be provided along the bundled drop assembly 10 downstream of a drop location where an optical fiber drop cable 18 or electrical conductor cable drops off of the bundled drop assembly 10.
As shown in
Stranding of the subunits 12 around the central member 14 and around underlying layers 40, 42 of subunits 12 builds up viscoelastic energy into the subunits 12. In particular, Applicant has found that six subunits 12 having a diameter of 4.4 mm wrapped around a 5.0 mm diameter central member at a laylength to pitch circle ratio of fifteen will exhibit an unwinding force of 1900 g. Thus, for example at the end of the bundled drop assembly 10 or if the bundled drop assembly 10 is cut, the subunits 12 have a tendency to unwind, splaying outwardly from the bundled drop assembly. For example, if the bundled drop assembly 10 has a maximum outer dimension DB (shown in
In order to address the issue of residual winding stress in the subunits 12, Applicant has found that annealing the subunits 12 after they are wound into the bundled drop assembly 10 relieves all or a substantial portion of the winding stress.
After the first layer 40 of subunits 12 is wound and annealed, the bundled drop assembly 10 may be taken up on a reel as completed (i.e., the bundled drop assembly 10 may only contain a single layer of subunits 12). For the embodiment depicted in
After the second layer 42 of subunits 12 is wound and annealed, the bundled drop assembly 10 may be taken up on a reel as completed or for further winding of additional layers on a separate processing line. Further, the bundled drop assembly 10 may continue on the same processing line for winding of an additional layer of subunits 12. In either case, a further winding step 110-n is performed to add a further layer of subunits 12, and a further annealing step 120-n is performed to relieve the stress in the further layer of subunits 12. The winding 110-n and annealing 120-n steps are performed until the desired number of subunit layers are provided in the bundled drop assembly 10.
Advantageously, the annealed layers 40, 42 of subunits 12 substantially retain their bundled configuration without the use of binders, glues, or other retaining means. As compared to unannealed subunits that will unwind or straighten in an unrestrained configuration, the annealed subunits 12 according to the present disclosure will retain a corkscrew winding even if removed from the bundled drop assembly 10. Thus, for example, at the end of the bundled drop assembly 10 or at a cut location, the subunits 12 will not splay outwardly like the unannealed subunits. In embodiments, upon cutting the bundled drop assembly or at the end of the bundled drop assembly, the annealed subunits 12 will expand to a maximum cross-sectional dimension that is less than twice the maximum cross-sectional dimension DB in the bundled configuration, in particular less than 1.5×the maximum cross-sectional dimension DB in the bundled configuration, and more particularly less than 1.1×the maximum cross-sectional dimension DB in the bundled configuration. In certain embodiments, upon cutting the bundled drop assembly 10 or at the end of the bundled drop assembly 10, the annealed subunits 12 will not expand at all such that the maximum cross-sectional dimension in the unrestrained configuration substantially equals the pre-cut-maximum cross-sectional dimension DB in the bundled configuration.
Applicant found that, for a bundled drop assembly having the parameters described, the initial maximum cross-sectional dimension of 13.1 mm will expand to 61.5 mm when the predetermined distance 160 to the cut line 170 is 3 inches, to 108.7 mm when the predetermined distance 160 to the cut line 170 is 6 inches, to 154 mm when the predetermined distance 160 to the cut line 170 is 9 inches, and to 279.4 mm when the predetermined distance 160 to the cut line 170 is 12 inches. At around 12 inches, it is believed that the weight of the subunits affects the splaying of the subunits from the central member, leading to the large jump in maximum cross-sectional dimension.
Further, Applicant has found that a bundled drop assembly 10 having six annealed subunits 12 with diameters of 4.4 mm wrapped around a 5 mm diameter central member at a laylength to pitch circle ratio of fifteen will exhibit an unwinding force of less than 1000 g, more particularly less than half that of a comparable bundled drop assembly having unannealed subunits. In particular, Applicant found that the unwinding force was about 550 g. That is, annealing the subunits will lower the unwinding force by at least 50%, in particular by at least 50%, and most particularly by about 70%.
The bundled drop assembly 10 having annealed subunits as disclosed herein provides several advantages in processing, storage, and installation. In particular, by annealing the subunits 12, the subunits 12 will maintain their bundled configuration in the bundled drop assembly 10 without the need for binders or glue. Applying such binders or glue slows down the processing line speed, decreasing throughput. In contrast, the in-line heating apparatuses do not substantially slow down the processing line speed, and the annealing temperatures are sufficiently low that they do not significantly add to the processing cost. Further, the annealing allows for longer subunit laylengths, which increases processing speed. Additionally, the subunits 12 are able to remain in the bundled configuration without unwinding during storage. Similarly, during installation, the same concern of unwinding at an end of the cable or at a cut location is eliminated for a bundled drop assembly 10 having annealed subunits 12.
Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. In addition, as used herein, the article “a” is intended to include one or more than one component or element, and is not intended to be construed as meaning only one.
It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosed embodiments. Since modifications, combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the embodiments may occur to persons skilled in the art, the disclosed embodiments should be construed to include everything within the scope of the appended claims and their equivalents.
This application is a continuation of International Application No. PCT/US2022/013962 filed Jan. 27, 2022, which claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 63/146,783, filed on Feb. 8, 2021, the content of which is relied upon and incorporated herein by reference in its entirety.
Number | Date | Country | |
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63146783 | Feb 2021 | US |
Number | Date | Country | |
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Parent | PCT/US2022/013962 | Jan 2022 | US |
Child | 18229936 | US |