Cable assembly

Abstract

To provide a cable assembly configured to be terminated to MT ferrules, which is flexible and minimizes micro-bending.SOLUTION: An optical cable assembly 100 comprises: (a) a plurality of fibers 101; (b) a connector 102; (c) at least a first flat ribbonized portion 103 comprising at least a first portion of the plurality of fibers, the first flat ribbonized portion being terminated to the connector; and (d) at least a first non-flat portion 104 comprising at least a second portion of the plurality of fibers.SELECTED DRAWING: Figure 1

Description

[[TECHNICAL FIELD]]

[0001] The present invention generally relates to optical circuits, and more specifically, to an optical circuit having a flexible portion. [[BACKGROUND ART]]

[0002] The applicant has discovered a significant drawback of conventional multi-fiber cable assemblies. The termination of conventional multi-fiber cable assemblies generally requires that a plurality of fibers be ribbonized to provide a flat portion for termination with a ferrule, for example, an MT ferrule. The problem with this approach is that the ribbonized portion of the cable assembly cannot bend in-plane and can only bend out-of-plane, which severely limits the flexibility of the ribbon cable. Furthermore, since the ribbonized portion tends to have low cross-sectional strength, it will roll up when heat-shrinkable fiber protection is added. This roll-up can increase insertion loss caused by micro-bending in the transition portion. The applicant has found that the ribbonized portion generally requires a minimum length of 2 inches to prevent this roll-up condition. Yet another disadvantage of ribbonized cables is that other protection methods, such as adding a protective furcation tubing, cannot be directly terminated to the MT ferrule without using a transition to ribbon fibers. [[SUMMARY OF THE INVENTION]] [[Problem to be Solved by the Invention]]

[0003] There is a need for a cable assembly configured to be terminated to an MT ferrule that is flexible and minimizes micro-bending. The present invention particularly satisfies this need.

[0004] The applicant has developed a method for constructing a fiber assembly that includes a ribboned section and a non-ribboned section, wherein the assembly can be easily connectorized in the ribboned section, and yet the non-ribboned section is axially bendable. More specifically, the non-ribboned section reconfigures the fibers of the ribboned section to eliminate the rigid planar alignment of the fibers, allowing the fibers to be freely bent in any direction. Such a method facilitates the implementation of full axial flex sections at any point along the length of a normally flat ribbon cable, or at any point along the legs extending from an optical circuit. Furthermore, by adding an outer sheath on the non-ribboned section, these flexed sections, which would normally expose fragile individual fibers, are protected. [Means for solving the problem]

[0005] In one embodiment, the present invention relates to an optical cable assembly comprising (a) a plurality of fibers, (b) a connector, (c) at least a first flattened ribbon portion comprising at least a first portion of the plurality of fibers and terminated at the connector, and (d) at least a first non-flat portion comprising at least a second portion of the plurality of fibers.

[0006] The present invention also relates to a method for fabricating an optical cable assembly. In one embodiment, the method includes (a) stripping at least a first portion of a flat ribbon cable and leaving at least a second portion of the cable unstripped, wherein at least the first portion forms at least one non-flat portion and at least the second portion forms at least one flat portion, the at least one flat portion being at the end of the cable and the at least one non-flat portion being inside the at least one flat portion of the cable; (b) terminating at least one flat portion with a connector; and (c) enclosing at least one non-flat portion with an sheath, wherein the fibers within at least one non-flat portion are free to move relative to each other. In another embodiment, the method includes (a) routing a plurality of fibers to a substrate, each of the plurality of fibers having two ends, each end extending from the substrate, and one or more ends of different fibers among the plurality of fibers being brought together by at least a first leg and a second leg, the first leg including the plurality of ends of different fibers; (b) ribboning at least the distal portion of the first leg such that the proximal portion of the first leg adjacent to the substrate is not ribboned; (c) connectorizing the distal portion of the first leg; and (d) sheathing at least the proximal portion of the first leg such that the fibers of the proximal portion of the first leg are free to move relative to each other and bend freely in any direction.

[0007] The method of the present invention has significant advantages. For example, this technique imparts flexibility to thin fiber sections simply by increasing the thickness of the portion requiring full-axial bending. In addition, this disclosure can be combined with the teachings of U.S. Patent Application No. 16 / 562,023, filed September 5, 2019, which describes how a mini-boot can be replaced by terminating a heat-shrinkable sheath (e.g., Versafit) directly onto the ferrule. More specifically, in one embodiment, the sheath is thin-walled, allowing for the application of an elliptical spring to the flat portion behind the MT ferrule.

[0008] In addition, based on this disclosure, the length of the flat section behind the MT ferrule can be shortened without having to endure the rolling effect on the ribbon, as is the case with conventional optical cables. Therefore, instead of requiring at least 2 inches behind the ferrule, the length of the flat section can be shortened to less than 1 inch from the MT ferrule surface.

[0009] Furthermore, this disclosure allows for variations in the configuration of the optical assembly. For example, in one embodiment, the optical assembly may include multiple circular portions or one long circular portion within a given flat length between the end flat portions for MT ferrule terminations. In other embodiments, fiber sheathing only needs to cover the transition portions that transition from flat to circular and back to flat. For example, if additional fiber protection is not required, the flat ribbon portions may remain uncovered, thus further reducing the thickness of these areas. Again, yet another embodiment will be apparent to those skilled in the art in light of this disclosure.

[0010] The present invention will be described below with reference to the attached drawings. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view of one embodiment of the cable assembly of the present invention. [Figure 2] This figure shows two cable assemblies of the present invention having multiple flat sections and non-flat sections. [Figure 3] This is a schematic diagram of the optical assembly of the present invention, which incorporates a flexible optical circuit. [Figure 4] This is a perspective view of the optical assembly of the present invention having multiple stacked rows. [Modes for carrying out the invention]

[0012] Referring to Figure 1, one embodiment of the optical cable assembly 100 of the present invention is shown. The optical cable assembly 100 includes a plurality of fibers 101, a connector 102, at least a first flattened ribbon portion 103 including at least a first portion of the plurality of fibers and terminated at the connector, and at least a first non-flat portion 104 including at least a second portion of the plurality of fibers. These features will be described below in more detail and in relation to selected alternative embodiments.

[0013] In one embodiment, the flat portion is ribboned. Ribbonization of fibers is well known and will not be discussed in detail herein. It will suffice to say that ribbonization of a fiber array typically involves aligning multiple fibers (e.g., 250 micron diameter fibers) in a direction aligned along a plane, and then applying a binder to hold the fibers in this relative position. Generally, fiber ribbonization is used to manage / control cable assemblies and / or to facilitate termination to connectors. As is known, to terminate a ribboned cable, the binder and fiber buffering sheath are stripped from a portion of the ribbon to expose the bare fibers (typically 125 micron in diameter), which are then secured to a ferrule.

[0014] In one embodiment, the ferrule is an MT type ferrule, but the fiber may be terminated with any known ferrule and / or optical connector, including, for example, an MPO connector for multi-fiber termination, or an LC or FC connector type connector for single-fiber termination.

[0015] In one embodiment, the flat portion includes at least one row of multiple fibers. The number of fibers in a row can vary. For example, in one embodiment, a row of fibers includes 12 fibers, which is a common configuration for MT ferrules, but it should be understood that a row can include any number of fibers that work in conjunction with the appropriate ferrule.

[0016] In one embodiment, the flat section includes two or more stacked rows of multiple fibers. For example, referring to Figure 4, a multi-row cable assembly 400 is shown. As shown, the cable assembly 400 includes a flat section 403 having two stacked rows of fibers 403a, 403b. The two rows of fibers are joined to form a non-flat section 404 of the cable assembly 400. Such embodiments may be preferred when the cable assembly is terminated by an MT ferrule having multiple rows of fibers, such as a 24-fiber MT ferrule having two rows of 12 fibers. (It should be noted that the multi-layer approach requires a longer setback from the end face of the MT ferrule (e.g., about 2 inches) to allow for the stripping of individual ribbon fibers.) Again, the present invention is not limited to any particular ferrule configuration with respect to the number of stacked rows or the number of fibers in each row.

[0017] In one embodiment, the cable assembly includes a second flat section 107, as shown in the cable assembly 100 of Figure 1. The second flat section may contain the same fibers as the plurality of fibers 101 in the first flat section, or it may contain a different selection of fibers than the plurality of fibers 101. For example, the cable assembly 100 may be configured to break out different groups of connectorized fibers. In the embodiment shown in Figure 1, the fiber group in the first flat section and the fiber group in the second flat section are the same.

[0018] In one embodiment, the second flat section is terminated to a second connector. Here again, the connector may be any known optical connector, such as an MT ferrule connector, such as an MPO connector. In embodiments where the optical assembly is used as a breakout and the fiber group of the second flat section is smaller than the fiber group of the first flat section, the second connector may be of a different size, or even a single-fiber connector such as an LC connector. For example, in such embodiments, the second connector may include a plurality of second connectors, each connected to a different subgroup of fibers within the fiber group of the first flat section. This will be apparent to those skilled in the art in light of the different connector configurations disclosed herein.

[0019] Although the flat section in Figure 1 is shown as being terminated by a connector, it is not necessary to terminate the flat section with a connector. For example, referring to Figure 2, an embodiment of a cable assembly 200 having multiple flat sections 203, 207, 223 is shown, where the flat section 223 is not terminated with a connector but is connected to the non-flat sections 224, 204 shown in Figure 2.

[0020] The flat sections can be formed in various ways. In one embodiment, as described above, a portion of several fibers are ribboned. Alternatively, instead of ribboning a portion of the fibers, the process may be started from a state where the entire cable is ribboned, and the binder may be stripped from a portion of the cable assembly so that the fibers can move freely relative to each other, thereby forming non-flat sections. Further other techniques will be apparent to those skilled in the art in light of this disclosure.

[0021] In one embodiment, the flat portion of the cable assembly in FIG. 1 is adjacent to a non-flat portion. As described above, the non-flat portion reconfigures the fibers from the flat portion to eliminate the inflexible planar alignment of the fibers, thereby allowing the fibers to bend freely in any direction. In one embodiment, the fibers are simply arranged as a bundle with no adhesion between them. The bundle can have various cross-sections, for example, substantially circular, annular, or even rectilinear, when the non-flat portion needs to pass through an orifice of a specific form factor.

[0022] As described above, the non-flat portion not only facilitates bending of the cable assembly in any direction, but also relieves stress in the cable assembly, eliminating the need to lengthen the flat portion to resist curling as described above. For example, in one embodiment, the non-flat portion allows the flat portion to be less than 2 inches from the end of the ferrule. Indeed, in one embodiment, the flat portion has a length of less than 1 inch. Again, those skilled in the art can optimize the length of the non-flat portion in light of the present disclosure.

[0023] In one embodiment, the cable assembly includes at least a second non-flat portion comprising at least a fourth portion of the plurality of fibers. For example, referring to FIG. 2, cable assembly 200 includes a plurality of non-flat portions 204, 224. In the embodiment of FIG. 2, since the entire plurality of fibers is included in each of the flat portion and the non-flat portion, the fiber groups in the flat portion and the circular portion are identical. Similarly, in FIG. 1, the fiber group in the flat portion is identical to the fiber group in non-flat portion 104. Like the embodiment of FIG. 2, in the embodiment of FIG. 1, all of the plurality of fibers are located in each flat portion and non-flat portion.

[0024] However, as mentioned above, other embodiments exist. For example, when the cable assembly is used as a fiber distribution fanout, different groups of a plurality of fibers can be found in different flat portions and non-flat portions of the cable assembly. This is particularly possible when the cable assembly incorporates an optical circuit, as described below.

[0025] In one embodiment, the fiber assembly is integrated with an optical circuit, and in a more detailed embodiment, with a flexible optical circuit. Such circuits are well known. Conventional flexible optical circuits include a flexible substrate having an adhesive surface, on which an optical fiber is routed and adhered, such that the fibers are arranged and held in place to maintain a minimum bend radius. Each length of fiber extends from the substrate. In many cases, fibers extending from the substrate are gathered at leg portions.

[0026] As is known, flexible optical circuits are useful in managing fibers to provide fiber harnesses and breakouts. As described in Applicant's co-pending U.S. Patent Application No. 16 / 562,023, stress exists in the fiber at locations where the fiber extends from the substrate. This stress can be relaxed using the teachings of the present invention. More specifically, in one embodiment, fibers extending from the substrate are gathered at the non-flat portion, thereby allowing bending to relax the stress.

[0027] In breakout, one fiber from a first group of fibers in a leg may be routed and gathered together with a different fiber from another group in a different leg, or the fiber may be a single fiber in a leg. Such routing patterns are known. Generally, fibers in a given leg are terminated by a common connector. Accordingly, the fiber groups between different connectors in the flexible optical circuit of FIG. 3 may vary.

[0028] Referring to Figure 3 for more details, a schematic diagram of one embodiment of the cable assembly 300 of the present invention, integrated with an optical circuit, is shown. As shown, the cable assembly 300 includes a substrate 330 on which a plurality of fibers 301 are bonded in a predetermined pattern. It should be understood that optical fibers can be laid in a variety of complex patterns and optical circuits. This is well known and will not be described in detail herein. For simplicity, Figure 3 shows a simple pattern with a relatively small number of fibers. In this particular embodiment, the cable assembly 300 defines a plurality of legs 331a to 331f, each containing a different group of a plurality of fibers 301, although any number of legs is possible in any configuration. Considering leg 331a in detail, a first group of fibers extends from the substrate 330 at a non-planar section 304, which then transitions to a planar section 303, where the planar section 303 terminates at a connector 302a. For simplicity, in this example, there are only four fibers in this group. Similarly, in leg 331b, a different second group of fibers extends from the substrate 330 through a non-planar section, which then transitions to a planar section, and the planar section terminates at connector 302b. The fibers terminated at connectors 302a and 302b are placed on the substrate 330, and connectors 308a to 308d reconnect the fibers to different groups. More specifically, the fibers of the first and second groups extend first through a non-planar section in leg 331c, which then transitions to a planar section, and the planar section terminates at connector 308a. In leg 331d, two fibers of the first group are coupled to one fiber of the second group and terminated at connector 308b. Similar to leg 331c, leg 331e contains fibers of the first and second groups. Leg 331f contains only a single fiber of the second group. Here again, the number of fibers, the number of legs, and the group of fibers in each leg can be configured infinitely in the optical circuit of the present invention.

[0029] An alternative embodiment of the above configuration involves incorporating a flexible optical circuit, where the non-linear pattern of the fiber is routed to a permanent substrate with adhesive, and the linear portion of the fiber is routed to a temporary substrate and masked before the application of a conformal coating. The masked area remains as a separate fiber. In one embodiment, a heat-shrinkable sheath such as Versafit may be added to these separate fibers to provide a desired full-axis bend within the flexible optical circuit.

[0030] In one embodiment, the sheath covers at least a portion of a plurality of fibers. More specifically, as shown in Figure 1, the sheath 109 encloses the fiber 101 to provide chemical and / or abrasion protection. In this particular embodiment, the sheath 109 encloses the fiber only at the non-flat portion 104. Alternatively, in the embodiment of Figure 2, the sheath encloses the entire length of the cable assembly 200. While these embodiments show the entire cable assembly enclosed in the sheath, other embodiments are possible. For example, in the embodiment of Figure 3, only the fibers extending from the substrate are enclosed in the sheath.

[0031] In one embodiment, the sheath around the ribbon cable also contacts the rear end of the ferrule to form a seal, which prevents epoxy or other adhesives from leaking out of the rear opening. Conversely, in the prior art, a boot is required that essentially seals the rear opening of the ferrule to prevent epoxy leakage. Thus, a major advantage of the sheathed ribbon cable of the claimed invention is not only the abrasion resistance / durability provided by the sheath, but also the simplification of ferrule termination by eliminating the need for a mini-boot. In one embodiment, the sheath is a heat-shrinkable material. In one embodiment, the heat-shrinkable sheath includes Versafit.

Claims

1. Multiple fibers, The first connector and The second connector, A first flattened ribbon portion (207) includes at least a first portion of the plurality of fibers and is terminated at the first connector, A second flattened ribbon portion (203) includes at least a third portion of the plurality of fibers and is terminated at the second connector, Non-flat portions (204, 224) including at least a second portion of the plurality of fibers, At least the heat-shrinkable outer covering on the non-flat portion and An optical cable assembly including, The non-flat portion (204, 224) includes at least a first non-flat portion (204) and a second non-flat portion (224), The aforementioned optical cable assembly is The plurality of fibers further include a flat portion (223) that is located between the first non-flat portion (204) and the second non-flat portion (224), connected to the first non-flat portion (204) and the second non-flat portion (224), and not terminated to a connector. Optical cable assembly.

2. The heat-shrinkable casing includes Versafit. The cable assembly according to claim 1.

3. The aforementioned connector is an MT connector. The cable assembly according to claim 1.

4. The flattened ribbon portion (207, 203) and / or the flat portion (223) includes at least one row of the plurality of fibers, The cable assembly according to claim 1.

5. The flattened ribbon portion (207, 203) and / or the flat portion (223) includes two or more stacked rows of the plurality of fibers, The cable assembly according to claim 4.

6. The non-flat portion (204, 224) includes the radial distribution of the plurality of fibers, The cable assembly according to claim 1.

7. The non-flat portion (204, 224) includes a circular portion, The cable assembly according to claim 1.

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