Device for furcating fiber optic cables

A fiber optic cable assembly is provided. The cable assembly includes a housing, a plurality of furcation tubes, and a bundled cable. The housing has an opening at a first end and a plurality of channels at a second end. The furcation tubes are aligned with corresponding channels. One end of the bundled cable extends into an interior space of the housing through the opening. The bundled cable has a cable jacket and cable filaments. A first portion of the cable filaments extends beyond the end of the cable jacket in the interior space. A plurality of optic fibers is disposed in the bundled cable and the housing, and a molding compound is disposed around the furcation unit. Individual optic fibers are in individual furcation tubes and movable to slide longitudinally relative to the housing.

TECHNICAL FIELD

The present application relates to devices, assemblies, and methods for furcating fiber optic cables.

BACKGROUND

Fiber optic cables are frequently used for interconnecting computer systems (e.g., servers) because these cables can simultaneously carry a large amount of data without excessive transmission loss. A trunkline is a type of fiber optic cable that typically includes multiple optic fibers and strength filaments (e.g., Kevlar yarns) arranged lengthwise and encased in a protective jacket (e.g., plastic or metal tubing). At each end of the trunkline, the optic fibers are furcated into individual cables that terminate at individual connectors.

One conventional technique for furcating the trunkline uses heat-shrink tubing and epoxy.FIG. 1, for example, illustrates a prior art furcated cable100having a furcation unit101with a heat-shrink tube102encasing an epoxy104, a trunkline106connected to one end of the furcation unit101, and furcation tubes112projecting from the other end of the furcation unit101. The trunkline106includes a cable jacket113encasing portions of optic fibers108and cable filaments110. Each furcation tube112includes a tube jacket116encasing tube filaments114and one of the optic fibers108. The heat-shrink tube102overlaps both the trunkline106and the furcation tubes112to enclose a portion of the optic fibers108and filaments110,114. The epoxy104rigidly binds the enclosed optic fibers108and filaments110,114inside the heat-shrink tube102. Each optic fiber108extends from the trunkline106, through the epoxy104, and out from the furcation tubes112.

There are a number of drawbacks associated with the cable100described above. First, the furcation tubes112can occupy a considerable amount of space inside the heat-shrink tube102such that the heat-shrink tube102may not be able to accommodate a large number of furcation tubes. Furthermore, the optic fibers108can easily be damaged during installation, manufacturing, and other handling processes. For example, installing the furcated cable100typically includes pulling on the cable jacket113to draw the trunkline106through cable trays, conduits, and other channelways. The furcation unit101transmits the pulling force directly to the optic fibers108because the epoxy104rigidly binds the optic fibers108to the cable jacket113. The transmitted force can damage the fragile optic fibers108.

Another conventional technique for furcating the trunkline uses insertion-type connectors, such as the UniCam® MTP® connectors manufactured by Corning Cable Systems of Hickory, N.C. One drawback associated with this type of connectors is insertion loss. For example, a 10-gigabit system today typically has a transmission-loss budget of about 2.8 dB. An insertion-type connector typically incurs approximately 0.5 dB to 1.0 dB transmission loss at each junction. As a result, using three insertion-type connectors can potentially exceed the transmission loss budget.

DETAILED DESCRIPTION

The present disclosure describes devices, assemblies, and methods for furcating a fiber optic cable. The term “fiber optic” means any strand capable of transmitting optic signals. Suitable fiber optic materials include optically transmissive glass or plastic threads. It will be appreciated that several of the details set forth below are provided to describe the following embodiments in a manner sufficient to enable a person skilled in the relevant art to make and use the disclosed embodiments. Several of the details and advantages described below, however, may not be necessary to practice certain embodiments of the invention. Additionally, the invention can include other embodiments that are within the scope of the claims but are not described in detail with respect toFIGS. 2-10.

One aspect is directed toward a fiber optic cable assembly including a housing having a first end, a second end, and an interior space between the two ends. The housing has an opening at the first end and a plurality of channels at the second end. The fiber optic cable assembly also includes a plurality of furcation tubes aligned with corresponding channels and a bundled cable having cable filaments in a cable jacket. One end of the bundled cable extends into the interior space through the opening. The cable filaments include a first portion extending beyond the end of the cable jacket in the interior space and a second portion extending through the opening to be external to the housing and/or the cable jacket. The fiber optic cable assembly further includes a plurality of optic fibers movable to slide longitudinally relative to the bundled cable, the housing, and individual furcation tubes. A molding compound is positioned around the furcation unit.

Another aspect is directed toward a fiber optic cable assembly including a furcation unit having a head with a plurality of channels, a base having an opening and an anchor, and a cover coupled to the base and the head to define an interior space. The fiber optic cable assembly also includes a bundled cable having cable filaments inside a cable jacket. A portion of the cable filaments extend beyond the cable jacket, around the anchor, and out of the interior space via the opening. The fiber optic cable assembly further includes a plurality of furcation tubes corresponding to individual channels and a plurality of optic fibers slidably disposed in the bundled cable, the base, individual channels, and the furcation tubes.

Another aspect is directed toward a fiber optic cable assembly including a furcation unit having a first end, a second end, and an interior space. A bundled cable having a cable jacket and cable filaments is disposed at the first end of the furcation unit. A molding compound secures the cable filaments to the furcation unit. The fiber optic cable assembly also includes a plurality of optic fibers extending through the bundled cable and the furcation unit to project from the second end of the furcation unit. The optic fibers are slidably movable in a longitudinal direction relative to the furcation unit and the bundled cable.

A further aspect is directed toward a method of furcating a bundled cable into a plurality of furcation tubes. The bundled cable has a cable jacket enclosing a plurality of optic fibers and cable filaments. The method includes removing the cable jacket to partially expose the optic fibers and cable filaments, disposing each of the optic fibers inside one of the furcation tubes by extending the optic fibers from the bundled cable through the furcation unit, and engaging the cable jacket to the furcation unit by disposing the cable filaments proximate to an anchor inside the furcation unit.

FIG. 2Ais a partially exploded isometric view andFIG. 3is a top view of a furcated cable200in accordance with an embodiment of the invention. The furcated cable200can include a bundled cable202(e.g., a trunkline), furcation tubes204, and a furcation unit206in between the bundled cable202and the furcation tubes204. The furcated cable200can further include a plurality of optic fibers208that are slidably disposed in the bundled cable202, the furcation unit206, and the furcation tubes204such that the optic fibers208can move in a longitudinal direction.

The bundled cable202can include a cable jacket212encasing cable filaments210and portions of the optic fibers208. The optic fibers208and the cable filaments210can extend beyond one end of the cable jacket212proximate to the furcation unit206. The cable jacket212can be constructed from plastic, metals, metal alloys, fiberglass, or other suitable materials. The cable filaments210can include strength fibers constructed from Kevlar, Nylon, polyester, or other suitable materials. The optic fibers208can include single-mode fibers, multi-mode fibers, index-graded fibers, or a combination of these types of optic fibers. The bundled cable202can optionally include other components including, for example, insulating layers (e.g., a plastic sheath), strengthening devices to support the cable jacket212(e.g., metal rings or plastic strips), and signal transmission devices (e.g., waveguides, repeaters, etc.).

Individual furcation tubes204can include a tube jacket214, a buffer tube218slidably disposed inside the tube jacket214, and tube filaments216between the tube jacket214and the buffer tubes218. The tube filaments216at least partially surround a corresponding buffer tube218. The buffer tube218and tube filaments216can also extend beyond one end of the tube jacket214proximate to the furcation unit206. One optic fiber208is inside one buffer tube218. The tube jackets214and buffer tubes218can be constructed from plastic, metals, metal alloys, fiberglass, or other suitable materials. The tube filaments216can include strength fibers constructed from Kevlar, nylon, polyester, or other suitable materials.

The furcation unit206can include a housing207or other enclosure having a head220, a base222, and a cover224that form an interior space226. The housing207has a first end209aproximate to the bundled cable202and a second end209bproximate to the furcation tubes204. The head220can be a generally rectangular structure having channels228configured to receive the buffer tubes218, a slot221configured to receive the base222and/or the cover224. The head220can be constructed from plastic (e.g., polycarbonate, polyurethane, etc.), metal, wood, or other suitable materials. In other embodiments, the head220can be circular or another shape. Various embodiments of the head220are described in more detail below with reference toFIGS. 4 and 5.

In the embodiment shown inFIGS. 2 and 3, the buffer tubes218extend through the channels228and into the interior space226of the housing207. In another embodiment, the buffer tubes218can extend partially into the channels228but not into the interior space226. In another embodiment, individual buffer tubes218can encase one of the optic fibers208and be slidably disposed in the bundled cable202, the housing207, and one of the furcation tubes204. In a further embodiment, the buffer tubes218can be omitted, and the optic fibers208extend through the channels228to be disposed inside the tube jackets214as shown inFIG. 2B.

The cover224can include features (e.g., channels, notches, holes, etc.) to correspond to the base222and the head220. The cover224can be constructed from plastic, metal, wood, or other suitable materials. In the embodiment shown inFIG. 2, the cover224cooperates with the base222to form an opening238for the cable jacket212at the first end209aof the housing207. In other embodiments, the base222or the cover224can include the opening238.

The base222can include a first end230proximate to the bundled cable202, a second end232proximate to the head220, a first side wall234, a second side wall236, and a bottom wall237extending between the first and second ends230,232. The first end230can include the opening238for receiving the bundled cable202. The second end232of the base222can be configured to correspond with the head220. For example, the second end232of the base222can include features including, channels, notches, holes, etc., for interfacing with the head220. The base222can be constructed from plastic, metal, wood, or other suitable materials.

In the embodiment shown inFIGS. 2 and 3, the opening238has a diameter larger than the outer diameter of the cable jacket212. As a result, the bundled cable202can extend into the interior space226of the housing207through the opening238. In another embodiment, the opening238can have a diameter slightly smaller than the outer diameter of the cable jacket212such that the second end232stops the cable jacket212from extending into the interior space226of the furcation unit206.

The base222further includes a first anchor240and a second anchor242spaced apart from each other and near the first end230. In one embodiment, the first and second anchors240,242are formed integrally with the base222. For example, in the embodiment shown inFIG. 2, the anchors240,242are hollow columns with curved surfaces facing the second end232. The anchors240,242can extend from the bottom wall237of the base222and have oval-shaped channels. In other embodiments, the anchors240,242can be solid structures fixedly attached to the bottom wall237of the base222. For example, the first and second anchors240,242can be generally cylindrical tubes fixedly attached to the bottom wall237of the base222using techniques including, for example, welding, friction fitting, mechanical fastening, etc.

The first and second anchors240,242can define a primary channel244between the inner facing walls of the anchors240,242. The first anchor240and the first side wall234can define a first outer channel246, and the second anchor242and the second side wall236can define a second outer channel248. The optic fibers208extend through the primary channel244to the buffer tubes218. The optic fibers208are not fixed to the bundled cable202, the housing207, or the buffer tubes218, and thus the optic fibers208can slide longitudinally relative to these components. The cable filaments210can include a first portion210ain the interior space and a second portion210bexternal to the housing207and/or the cable jacket212. The first portion210aof the cable filaments210is positioned in the primary channel244and the first and second outer channels246,248to wrap around the faces of the first and second anchors240,242that face the second end232. The second portion210bof the cable filaments210extends through the opening238to be external to the housing207and/or the cable jacket212. In other embodiments, the cable filaments210can be positioned in only one of the outer channels246,248.

The furcated cable200can further include at least one layer of molding (e.g., an epoxy205) enclosing the furcation unit206. The epoxy205can firmly attach the second portion210bof the cable filaments210to the furcation unit206and/or the cable jacket212. In one embodiment, appropriate molding pressure is applied such that the epoxy205does not penetrate into the interior space226of the furcation unit206via the channels228and/or the opening238. As a result, the interior space226of the furcation unit206is substantially free of the epoxy205or any other adhesives such that the optic fibers208can slide longitudinally relative to the cable bundle202and the furcation unit206. In another embodiment, the epoxy205can penetrate partially into the interior space226via the channels218and/or the opening238but not contact the optic fibers208. In either embodiment, the optic fibers208can slide longitudinally in the interior space226of the furcation unit206.

One expected advantage of several embodiments of the furcated cable200is the reduced risk of damaging the optic fibers208during handling processes because the furcation unit206can isolate tensile forces from the optic fibers208. For example, when tension is applied to the cable jacket212during pulling (as indicated by arrow A), the epoxy205transmits the tension from the cable filaments210to the furcation unit206via the anchors240,242. The optic fibers208, however, are not fixed to the furcation unit206and can slide longitudinally inside the housing207relative to the cable jacket212, furcation tubes204, and the furcation unit206. As a result, the cable jacket212and the furcation unit206bear substantially all of the tensile forces applied to the cable jacket212. Consequently, the risk of damaging the fragile optic fibers208can be reduced.

Another expected advantage of several embodiments is the ability to arrange a large number (e.g., 24) of furcation tubes in an organized fashion. In one embodiment, the channels228at the head220are organized into an array that has wiring designations (e.g., pin-out markings) to easily organize a large number of furcation tubes. Several embodiments of the furcation unit206can also reduce transmission loss through the furcated cable200. Unlike in insertion-type connectors, the optic fibers208of the furcated cable200are continuous, i.e., not spliced in the furcation unit206. As a result, the furcation unit206does not incur any appreciable insertion loss caused by splices.

The furcated cable200can have many additional embodiments with different and/or additional features without detracting from the operation of the furcated cable200. For example, the head220, the base222, and/or the cover224of the furcation unit206can be formed as a unitary structure before assembly. In another example, the furcated cable200can include a heat-shrink tube covering the cable filaments210external to the cable jacket212before the epoxy205is applied. The furcated cable200can also include an adhesive between the furcation tubes204and the head220for additional structural integrity. In further embodiments, the furcated cable200can include fasteners including, for example, mechanical fasteners, compression fittings, etc., to assemble the furcation unit206, the bundled cable202, and the furcation tubes204into a furcated cable.

FIG. 4is a partial top view of the furcation unit206ofFIGS. 2 and 3illustrating the head220in more detail. In the illustrated embodiment, only one furcation tube204is shown for clarity. The channels228can extend from a first face215to a second face217of the head220. The channels228can have a diameter larger than the outer diameter of the buffer tube218but smaller than the inner diameter of the tube jacket214. As a result, the buffer tubes218extend through the channels228, but the tube jackets214and the tube filaments216butt up against the first face215. The tube jacket214and the tube filaments216, therefore, do not pass into the interior space226. After assembly, the epoxy205can firmly attach the tube filaments216to the tube jacket214and/or the furcation unit206.

FIG. 5is an alternative example of the furcation unit206ofFIG. 4in accordance with one embodiment of the invention. This alternative example and other alternatives described herein are substantially similar to previously described examples, and common acts and structures are identified by the same reference numbers. Only significant differences in operation and structure are described below. In this example, the furcation unit206includes a head300having first channels302and second channels304. A first channel302corresponds to and is in communication with a second channel304. The first channel302can have a diameter larger than the outer diameter of the tube jacket214. The second channel304can have a diameter smaller than the inner diameter of the tube jacket214but larger than the outer diameter of the buffer tube218. As a result, the tube jacket214and a portion of the tube filaments216can at least partially extend into the first channel302but not pass through the second channel304. Instead, only the buffer tube218extends through the second channel304and into the interior space226. In one embodiment, the head300includes an adhesive disposed in the first channels302to firmly engage the tube jacket214to the head300. In another embodiment, the furcation tube204can engage the head300by friction, mechanical fastening, or other suitable means.

D. Assembly Process

FIGS. 6-9are partial isometric views of a furcation unit during stages in an assembly process in accordance with one embodiment of the invention. During assembly, a portion of the tube jacket214can be removed from each of the furcation tubes204to expose a desired length (e.g., two inches) of the buffer tube218and the tube filaments216. The exposed buffer tube218can then be inserted through one of the channels228at the head220of the furcation unit206. As illustrated inFIG. 6, each channel228receives one buffer tube218and prevents the exposed tube filaments216and the tube jackets214from extending through the channels228.

A portion of the cable jacket212can be removed to expose a desired length of the optic fibers208and the cable filaments210. As illustrated inFIG. 7, each of the optic fibers208is inserted in one of the corresponding buffer tubes218extending from the head220via the primary channel244and the internal space226of the furcation unit206. A first portion211of the exposed cable filaments210can be wrapped around the first anchor240and extended beyond the opening238to be external to the cable jacket212. A second portion213of the exposed cable filaments210can be wrapped around the second anchor242and extended beyond the opening238to be external to the cable jacket212. The cable filaments210external to the cable jacket212can be at least partially aligned with the bundled cable202. Then the base222can be inserted into the head220. The cover portion can then be combined with the head220and the base222to form the furcation unit206as illustrated inFIG. 8.

As illustrated inFIG. 9, in one embodiment, a heat-shrink tube252can be disposed at least partially over the furcation unit206and the bundled cable202. The heat-shrink tube252can at least partially fasten the cable filaments210to the cable jacket212before heat molding. In the embodiment shown inFIG. 9, a portion of the cable filaments210extends from the heat-shrink tube252to cover a portion of the furcation unit206. In other embodiments the heat-shrink tube252can substantially completely cover the cable filaments210external to the cable jacket212. The epoxy205can then be disposed over the furcation unit206and at least a portion of the bundled cable202and the furcation tubes204. In one embodiment, at least one layer of epoxy205can be disposed. In another embodiment, other means of assembly can be used including, for example, mechanical fasteners, compression fittings, etc.

FIGS. 10-14are partial isometric views of a furcation unit during stages in an alternative assembly process in accordance with another embodiment of the invention. During assembly, a first template223acan be placed adjacent to the head220. As illustrated inFIG. 10, the first template223ais a generally rectangular block having apertures (not shown) corresponding to the channels228to allow the buffer tubes218to extend through. The first template223acan be constructed from plastic, metal, wood, or any suitable material with sufficient rigidity. Then, the buffer tubes218can be partially exposed from the tube jackets214and inserted through the channels228at the head220of the furcation unit206.

As illustrated inFIG. 11, a second template223bsimilar to the first template223acan then be placed spaced apart from the head220. The second template223bincludes apertures229to allow the tube jackets214to extend through the second template223b. A molding compound225(e.g., an epoxy) can be disposed between the first and second templates223a-bto fasten the tube jackets214but not the buffer tubes218to the head220. A portion of the molding compound225is removed for clarity. Then, the buffer tubes218are withdrawn from the tube jackets214, and the first and second templates223a-bare removed to form a subassembly201as illustrated inFIG. 12.

A portion of the cable jacket212can be removed to expose a desired length of the optic fibers208and the cable filaments210. As illustrated inFIG. 13, each of the optic fibers208is inserted in one of the channels228via the primary channel244and the internal space226of the furcation unit206. A first portion211of the exposed cable filaments210can be wrapped around the first anchor240and extended beyond the opening238to be external to the cable jacket212. A second portion213of the exposed cable filaments210can be wrapped around the second anchor242and extended beyond the opening238to be external to the cable jacket212. The cable filaments210external to the cable jacket212can be at least partially aligned with the bundled cable202. Then the base222can be inserted into the subassembly201. The cover portion can then be combined with the subassembly201and the base222to form the furcation unit206as illustrated inFIG. 14. Optionally, the heat-shrink tube252can be disposed at least partially over the furcation unit206and the bundled cable202as described above with reference toFIG. 9. Then, the epoxy205can then be disposed over the furcation unit206, the subassembly201, at least a portion of the bundled cable202and the furcation tubes204.

E. Other Example of Furcation Unit

FIG. 15is an alternative example of the furcation unit206ofFIG. 4in accordance with another embodiment of the invention. In the illustrated embodiment, the cover224has been removed for clarity. In this example, the base222includes a cable seat402positioned proximate to the opening238and configured to support the bundled cable202(FIG. 2). The base222further includes an anchor404proximate to the opening238. The anchor404can have a generally elongated shape and be spaced apart from the first side wall234to define a primary channel406. The second side wall236and the cable seat402can define a secondary channel408. During assembly, the cable filaments210can pass through the channels406,408and extend beyond the opening238to be external to the furcation unit206.

The furcation unit206can further include an end portion410opposite the head220. The end portion410can be either releasably or fixedly attached to the base222. The end portion410can be constructed from plastic, metals, metal alloys, fiberglass, or other suitable materials. In the illustrated embodiment, the end portion410includes a generally rectangular structure having a hollow center for receiving the second end232of the base222. In other embodiments, the end portion410can include other shapes and/or configurations including, for example, a ring-shaped structure, a square-shaped structure, etc.

Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of “including, but not limited to.” Words using the singular or plural number also include the plural or singular number, respectively. When the claims use the word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

The above detailed descriptions of embodiments of the invention are not intended to be exhaustive or to limit the invention to the precise form disclosed above. Although specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, when steps are presented in a given order, alternative embodiments may perform steps in a different order. The various embodiments described herein can be combined to provide further embodiments.

In general, the terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification, unless the above detailed description explicitly defines such terms. Although certain aspects of the invention are presented below in certain claim forms, the inventors contemplate the various aspects of the invention in any number of claim forms. Accordingly, the inventors reserve the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the invention.