Ruggedized microcable for inside plant applications

Abstract

Fiber optic microcables and cable assemblies are provided. A microcable includes a central inner jacket formed from a flame retardant material, and a plurality of optical fibers disposed within the inner jacket, wherein a total number of optical fibers in the fiber optic microcable is greater than or equal to 145. The microcable further includes a plurality of first strength members disposed within the inner jacket, an outer jacket surrounding the central inner jacket, the outer jacket formed from a flame retardant material, and a plurality of second strength members disposed between the outer jacket and the central inner jacket, a fiber density of the cable is between about 3.1 fibers per square millimeter and about 8.38 fibers per square millimeter.

Description

RUGGEDIZED MICROCABLE FOR INSIDE PLANT APPLICATIONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Patent Application Serial No. 63 / 582,673 filed on September 14, 2023, the disclosure of which is incorporated by reference herein in its entirety.FIELD

[0002] The present disclosure relates generally to fiber optic cable, and more particularly to fiber optic microcables having improved characteristics such as weight, diameter, flame test rating, fiber density, bend radius, etc.BACKGROUND

[0003] Optical fiber cables are utilized in building / campus local area networks, central offices, data centers and other premises where high bandwidth data transfer is required. These cables can be deployed in both overhead and raised floor cable pathways, along with terminations into data cabinets. As data transfer requirements have increased, the number of fibers to support these demands has driven the development of high fiber density products. High density microcables along with multi-fiber connectivity have been instrumental in supporting the increasing demands for high bandwidth data transfer.

[0004] Known distribution cables are typically sub-unitized and include a central strength member. However, while many such distribution cables are useful and provide the desired performance characteristics, improvements in distribution cable design are desired. For example, increased flexibility and fiber density are desired to provide improved installation and optical transmission capabilities. However, the ruggedness and relatively small overall size of the cables must desirably be maintained.

[0005] Accordingly, improved fiber optic microcables are desired in the art. In particular, fiber optic microcables which provide improved characteristics such as weight, diameter, flame test rating, fiber density, bend radius, etc. would be advantageous.BRIEF DESCRIPTION

[0006] Aspects and advantages of the present disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the technology.

[0007] In accordance with one embodiment, a fiber optic microcable is provided. The microcable includes a central inner jacket formed from a flame retardant material, and a plurality of optical fibers disposed within the inner jacket, wherein a total number of optical fibers in the fiber optic microcable is greater than or equal to 145. The microcable further includes a plurality of first strength members disposed within the inner jacket, an outer jacket surrounding the central inner jacket, the outer jacket formed from a flame retardant material, and a plurality of second strength members disposed between the outer jacket and the central inner jacket, a fiber density of the cable is between about 3.1 fibers per square millimeter and about 8.38 fibers per square millimeter.

[0008] In accordance with another embodiment, a cable assembly is provided. The cable assembly includes a microcable. The microcable includes a central inner jacket formed from a flame retardant material, and a plurality of optical fibers disposed within the inner jacket, wherein a total number of optical fibers in the fiber optic microcable is greater than or equal to 145. The microcable further includes a plurality of first strength members disposed within the inner jacket, an outer jacket surrounding the central inner jacket, the outer jacket formed from a flame retardant material, and a plurality of second strength members disposed between the outer jacket and the central inner jacket, a fiber density of the cable is between about 3.1 fibers per square millimeter and about 8.38 fibers per square millimeter. The cable assembly further includes a plurality of connectors, each of the plurality of connectors terminated to one or more optical fibers of the plurality of optical fibers .

[0009] These and other features, aspects and advantages of the present disclosure will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the technology and, together with the description, serve to explain the principles of the technology.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A full and enabling disclosure of the present application, including the best mode of making and using the present systems and methods, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0011] FIG. 1 is a cross-sectional view of a fiber optic microcable in accordance with embodiments of the present disclosure;

[0012] FIG. 2 is a cross-sectional view of an optical fiber for use with a fiber optic microcable in accordance with embodiments of the present disclosure;

[0013] FIG. 3 is a top view of a plurality of optical fibers utilized in a fiber optic microcable in accordance with some embodiments of the present disclosure; and

[0014] FIG. 4 is a top view of a plurality of optical fibers utilized in a fiber optic microcable in accordance with other embodiments of the present disclosure.

[0015] FIG. 5 is a perspective view of a fiber optic bundle for use with a fiber optic microcable in accordance with embodiments of the present disclosure; and

[0016] FIG. 6 is a schematic view of a cable assembly which utilizes a fiber optic microcable in accordance with embodiments of the present disclosure.DETAILED DESCRIPTION

[0017] Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, each example is provided by way of explanation, rather than limitation of, the technology. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present technology without departing from the scope or spirit of the claimed technology. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims andtheir equivalents. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the disclosure.

[0018] As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. The terms “coupled,” “fixed,” “attached to,” and the like refer to both direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching through one or more intermediate components or features, unless otherwise specified herein. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive- or and not to an exclusive- or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0019] Terms of approximation, such as “about,” “generally,” “approximately,” or “substantially,” include values within ten percent greater or less than the stated value. When used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction. For example, “generally vertical” includes directions within ten degrees of vertical in any direction, e.g., clockwise or counter-clockwise.

[0020] Benefits, other advantages, and solutions to problems are described below with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims.

[0021] In general, the present disclosure advantageously provide improved ruggedized microcables which may be utilized in, for example, inside plantapplications. Such cable may provide improved flexibility and fiber density relative to known cable designs while also maintaining desired ruggedness and size characteristics. Such cables may further provide improved characteristics such as weight, diameter, flame test rating, fiber density, and / or bend radius, etc. For example, in some embodiments, the present disclosure provides a reduced diameter, flexible, high fiber count microcable suitable for inside plant horizontal backbone applications. In other embodiments, the present disclosure provides a connectorized, reduced diameter, flexible high fiber count microcable in the form of a cable assembly.

[0022] Referring now to FIG. 1, a fiber optic microcable 10 in accordance with embodiments of the present disclosure is provided. Cable 10 includes an inner jacket 12, and a plurality of optical fibers 14 disposed within the inner jacket 12.Additionally, a plurality of first strength members 16 may be disposed within the inner jacket 12. An outer jacket 18 may surround the inner jacket 12, and a plurality of second strength members 20 may be disposed between the outer jacket 18 and the inner jacket 12. All of the optical fibers 14 utilized in the cable 10 may be disposed within the inner jacket 12, and no optical fibers 14 may be disposed between the inner jacket 12 and outer jacket 18.

[0023] In some embodiments, one or more ripcords 22 may be disposed between the inner jacket 12 and outer jacket 18 and / or within the inner jacket 12.

[0024] The inner jacket 12 is, as shown, a central inner jacket 12 which thus generally encompasses a center point of the cable 10 in a cross-sectional view. Further, as shown, only a single inner jacket 12 is utilized. In other words, only a single sub-unit, rather than multiple sub-units, is utilized in cable 10. All optical fibers 14 utilized in cable 10 are thus disposed within the inner jacket 12. The inner jacket 12 has a generally continuous tubular cross-sectional shape, as shown.

[0025] The inner jacket 12 may be formed from a flame retardant material, which may in exemplary embodiments be a thermoplastic or thermoset polymer. In exemplary embodiments, such flame retardant material may be a polyethylene (PE), a polyvinyl chloride (PVC), a polyvinylidene fluoride (PVDF), or other low smoke zero halogen material (which may for example include a polyolefin). In exemplary embodiments, the inner jacket 12, and thus the material utilized to form the innerjacket 12, may be suitable to achieve a riser-rated or plenum-rated flame rating. In exemplary embodiments, the central sub-unit, including the inner jacket 12 and material within, may have a National Fire Protection Association 70 (NFPA 70, National Electric Code, 2014 edition) flame rating of OFNR-LS (riser rated) or meet the FT4 requirements of Canadian Standards Association(CSA) Standard C22.2 No 232-09 (Sept 2009 revision) (riser-rated) (with, for example, a flame propagation characteristic of less than 12 feet.) In exemplary embodiments, the central sub-unit, including the inner jacket 12 and material within, may have a NFPA 70 NEC rating of OFNP or meet the FT6 requirements of CSA C22.2 No.232-09 plenum-rated) (with, for example, a flame propagation characteristic of less than 5 feet and having low smoke density).

[0026] The outer jacket 18 also has a generally continuous tubular cross-sectional shape, as shown. The outer jacket 18, which may be the outermost exterior layer of the cable 10, may be formed from a flame retardant material, which may in exemplary embodiments be a thermoplastic or thermoset polymer. In exemplary embodiments, such flame retardant material may be a polyethylene (PE), a polyvinyl chloride (PVC) ), a polyvinylidene fluoride (PVDF), or other low smoke zero halogen material (which may for example include a polyolefin). In exemplary embodiments, the cable 10, including the outer jacket 18 and material within may have NFPA 70 (NEC) flame rating of OFNR-LS (riser rated) or meet the FT4 requirements of CSA C22.2 No.232- 09 (riser-rated) (with, for example, a flame propagation characteristic of less than 12 feet.) In exemplary embodiments, cable , including the outer jacket 12 and material within, may have a US NEC rating of OFNP or or meet the FT6 requirements of CSA C22.2 No.232-09 (with, for example, a flame propagation characteristic of less than 5 feet and having low smoke density).

[0027] In some embodiments, the outer surface of the outer jacket 18 is generally smooth and cylindrical. In other embodiments, in a cross-sectional profile of the outer jacket 18 the outer surface may include a series of alternating protrusions and recesses to, for example, facilitate air jetting in microducts.

[0028] The inner jacket 12 and / or outer jacket 18 in exemplary embodiments are extruded. In some embodiments, the outer jacket 18 may be formed from the same material as the inner jacket 12. Alternatively, different materials may be utilized forthe inner jacket 12 and outer jacket 18. In some embodiments, the outer jacket 18 may include multiple sublayers, each of which includes a different material.

[0029] As discussed, first strength members 16 may be disposed within the inner jacket 12, and / or second strength members 20 may be disposed between the outer jacket 18 and inner jacket 12. In some embodiments, there are no first strength members 16 within the inner jacket 12 and all of the strength members in the cable 10 are second strength members 20 disposed between in the inner jacket 12 and the outer jacket 18. Alternatively, in some embodiments, there are no second strength members 20 disposed between in the inner jacket 12 and the outer jacket 18 and all of the strength members in the cable 10 are first strength members 16 disposed within the inner jacket 12. Alternatively, both first and second strength members 16, 20 may be utilized.

[0030] In exemplary embodiments, the first strength members 16 and second strength members 20 may be fibers or yarns, such as aramid fibers or yarns, or other suitable fibers or yams utilized for strength purposes, or for example fiberglass rovings or other suitable composite rovings having suitable tensile strength characteristics. It should be noted that, in exemplary embodiments as shown, no additional components or materials, aside from second strength members 20 and optional binders or ripcords, may be provided in the space between the outer jacket 18 and inner jacket 12. Such space may thus, for example, be free from gels, additional intervening jackets or other tubes, etc. Similarly, in exemplary embodiments as shown, no additional components or materials, aside from first strength members 16 and optical fibers 14 as discussed herein, may be provided within inner jacket 12.

[0031] In some embodiments, first strength members 16 may be generally loose, non-stranded members that extend through the inner jacket 12. Alternatively, first strength members 16 may be helically stranded about the optical fibers 14 (e.g. the bundles of optical fibers as discussed herein). In exemplary embodiments, the first strength members 16 may be helically stranded about all of the optical fibers 14 within the inner jacket 12, such that no optical fibers are outside of the first strength members 16.

[0032] In some embodiments, six yams may be utilized as first strength members 16. Alternatively, two, three, four, five, seven, eight, or more yarns may be utilized.Further, in exemplary embodiments, each yarn may have a weight between 600 denier and 2840 denier.

[0033] In some embodiments, second strength members 20 may be generally loose, non-stranded members that extend between the inner jacket 12 and outer jacket 18. Alternatively, second strength members 20 may be helically stranded about the inner jacket 12.

[0034] In some embodiments, the total weight of strength members (e.g. first and second strength members 16, 20) utilized in a cable 10 may be between 17,000 denier and 37,000 denier, such as between 20,000 denier and 35,000 denier, such as between 20,000 denier and 21,000 denier, such as between 34,000 denier and 35,000 denier, such as about 20,640 denier, such as about 34,080 denier (or the equivalent to any such denier if, for example, the first and second strength members 16, 20 are not all yarns).

[0035] Any suitable optical fibers 14 may be utilized in cable 10. In exemplary embodiments, the optical fibers 14 may be single mode optical fibers. In exemplary embodiments, the optical fibers 14 may have nominal (plus or minus 3 microns) outer diameters of 200 microns.

[0036] In some embodiments, the optical fibers 14 may have a nominal mode field diameter of between 8.6 microns and 9.4 microns @ 1310 nanometers (with tolerance of + / - 0.4 microns). In some embodiments, the optical fibers 14 may have a mode field diameter of 8.6 microns + / - 0.4.

[0037] In some embodiments, the optical fibers 14 may have a low macrobending loss design which is compliant with ITU-T G.657. Al or ITU-T G.657.A2 (Characteristics of a bending-loss insensitive single-mode optical fibre and cable, Rev 11 / 2016) and / or with ITU-T G.652.D (Characteristics of a singlemode optical fibre and cable, Rev 11 / 2016).

[0038] Examples of optical fibers 14 suitable for use in cables 10 in accordance with the present disclosure include Fujikura Futureguide™ SR-15e, Fujikura FutureGuide™-LWP plus-200, Fujikura Futureguide™ BIS-B, Fujikura Futureguide™ Ace, Coming® SMF-28® Ultra, and / or Corning® SMF-28® Contour optical fibers.

[0039] Referring now to FIG. 2, one embodiment of an optical fiber 14 for use in cables 10 in accordance with the present disclosure is provided. As shown, the optical fiber 14 includes a bare optical fiber 30, which is coated with a fiber coating 32. The bare optical fiber 30 is composed of a cladding and a core made of, for example, silica glass. The fiber coating 32 is made of, for example, an ultraviolet curing resin. The fiber coating 32 may have a single- or multi-layer structure. In a multi-layer structure, the outside of the ultraviolet curing resin layer may, for example, be further coated with a thermoplastic resin, a different ultraviolet curing resin, or the like. On the outer surface of the fiber coating 32, a predetermined marking 34 may be provided. Furthermore, the marking 34 may be coated with a translucent color layer 36.

[0040] The marking 34 may be provided at a predetermined distance interval in the longitudinal direction of the optical fiber 14. The markings 34 may be colored in opaque color such as white having a good light reflectivity and may be visible from the outside through the color layer 36. Alternatively, the markings 34 may be colored in translucent color. In such a case, the markings 34 may be colored in color darker than the color of the color layer 36 so as to be visible from the outside through the color layer 36. The color layers 36 of the optical fibers 14 which are part of an optical fiber ribbon (as described herein) may be colored in different colors.

[0041] In some embodiments, an outer diameter of the fiber coating 32 may be 185 microns (plus or minus 3 microns). In other embodiments, an outer diameter of the fiber coating 32 may be 193 microns (plus or minus 3 microns).

[0042] In some embodiments, the fiber coating 32 (such as, in multi-layer embodiments, each layer of the fiber coating 32) may have a Young’s modulus of between 0.5 MPa and 2000 MPa.

[0043] In exemplary embodiments, each optical fiber 14 of the plurality of optical fibers 14 in the cable 10 has been proof tested over the entire length of the fiber at a rate of between 100 kpsi and 200kpsi.

[0044] In some embodiments, as illustrated in FIG. 3, the optical fibers 14 may be loose optical fibers which are not ribbonized or otherwise bonded to each other. In alternative embodiments, the optical fibers 14 may be ribbonized to form one or more ribbons 40. For example, in some embodiments as illustrated in FIG. 4, the optical fibers 14 may be intermittently bonded to each other (via, for example, portions of theoutermost jacket or layer of the optical fibers 14), thus forming one or more ribbons 40. Such intermittent bonding may occur along the lengths of the optical fibers 14, thus leaving non-bonded gaps between neighboring optical fibers 14 as shown. Further, the bonded portions 42 of neighboring optical fibers 14 may be staggered along the lengths of the optical fibers 14 such that neighboring optical fibers 14 in a ribbon are bonded to each other at different locations along their lengths and the length of the ribbon 40. In some embodiments, pairs of neighboring fibers 14may be bonded together, either along their entire length or intermittently, and then these pairs of fibers may be intermittently bonded together with other pairs of neighboring fibers to form a flexible ribbon.

[0045] In some embodiments, the bonding portions 42 may be arranged in one or more diagonal patterns, as shown. Alternatively, other suitable patterns of bonding portions 42 may be utilized. In some embodiments, a length 41 between neighboring bonded portions 42 (as defined along a longitudinal axis of the ribbon 40) may be greater than a length 43 of each of the subject bonded portions 42. In exemplary embodiments, all lengths 41 in a ribbon 40 may be greater than all lengths 43. In some embodiments, a length 41 and / or all lengths 41 may be less than 150 millimeters.

[0046] In some embodiments, the optical fibers 14 in a ribbon 40 in accordance with the present disclosure may have a center-to-center spacing 45 between neighboring ribbons 40 of 200 microns (plus or minus 3 microns). Alternatively, the optical fibers 14 in a ribbon 40 in accordance with the present disclosure may have a center-to-center spacing 45 between neighboring ribbons 40 of 250 microns (plus or minus 3 microns).

[0047] A ribbon in accordance with the present disclosure may include two or more optical fibers 14, such in exemplary embodiments between two and twenty-four optical fibers 14, such as in exemplary embodiments eight, twelve, sixteen, or twenty- four optical fibers 14, or any range therebetween.

[0048] In exemplary embodiments, optical fibers 14 and ribbons 40 utilized in cables 10 in accordance with the present disclosure have relatively small attenuation characteristics. For example, in exemplary embodiments, optical fibers 14 utilized in cables 10 in accordance with the present disclosure have maximum fiber attenuationsof less than 0.35 dB / km at 1310 nanometers and less than 0.25 dB / km at 1550 nanometers. Such small attenuations are achieved via tight control of manufacturing tolerances related to, for example, colored fiber coating diameter, fiber position, fiber tension and ribbon tension during the ribbon bonding process to achieve low microbending loss.

[0049] Referring now to FIG. 5, in some embodiments, one or more loose fibers 14 or ribbons 40 in a cable 10 may be bundled together to form one or more fiber optic bundles 50. Each bundle 50 may include one or more loose fibers 14 and / or one or more ribbons 40. For example, in some exemplary embodiments, each bundle 50 may include between three and twelve ribbons 40, such as between four and twelve ribbons 40. Each bundle 50 may further include one or more bundling members 52 which are wound around an outer circumference of the loose fibers 14 or ribbons 40 in the bundle 50 generally. Such bundling can generally secure the fibers 14 and / or ribbons 40 together in a tight, space-efficient manner that allows for maximum fiber density while also allowing for easy and efficient mid-span access.

[0050] In exemplary embodiments, the bundling members 52 may be strings. Alternatively, other suitable materials may be utilized. In some embodiments, the bundling member(s) 52 of each bundle 50 may have a color, and that color may be different from the bundling member(s) 52 in all other bundles 50 of the cable 10. Thus, each bundle 50 can be easily identified by color in the cable 10.

[0051] In some embodiments, each bundle 50 may include only a single bundling member 52. Such first bundling member 52’ may be wound helically around the fibers 14 and / or ribbons 40 in the bundle 50. Alternatively, in some embodiments, each bundle 50 may further include a second bundling member 52. Such second bundling member 52” may be wound helically around the fibers 14 and / or ribbons 40 in the bundle 50. In exemplary embodiments, the second bundling member 52” may be wound in a direction opposite the first bundling member 52’.

[0052] In exemplary embodiments, the fibers 14 and / or ribbons 40 in cable 10 may have a lay length of greater than 50 millimeters. Additionally or alternatively, the fibers 14 and / or ribbons 40 may have a finished cable excess fiber length percentage (e.g. a length of the fibers 14 and / or ribbons 40 versus a length of the outerjacket 18) of between 0 and 0.5%. The fibers 14 and / or ribbons 40 may be helically or S-Z stranded, or may be pulled in straight.

[0053] In exemplary embodiments, cables 10 in accordance with the present disclosure may include relatively high fiber counts. A fiber count as used herein is the total number of fibers 14 utilized in the cable 10, whether in loose, ribbonized, and / or bundled form. In exemplary embodiments, the fiber count of a cable 10 in accordance with the present disclosure is greater than 144 fibers, such as greater than or equal to 145 fibers, such as between 145 fibers and 6912 fibers, such as between 145 fibers and 432 fibers, such as between 145 fibers and 288 fibers, such as between 289 fibers and 432 fibers, such as between 433 fibers and 576 fibers, such as between 577 fibers and 864 fibers, such as between 865 fibers and 1728 fibers, such as between 1729 fibers and 6912 fibers.

[0054] Referring again to FIG. 1, cables 10 in accordance with the present disclosure may advantageously have relatively high fiber densities and sub-unit fiber densities. As utilized herein, fiber density is the total number of optical fibers in a cable 10 divided by the cross-sectional area of the cable 10. The cross-sectional area may be calculated as pi times the square root of the maximum radius of the cable 10, and the maximum radius may be half of the maximum outer diameter 64 of the outer jacket 18. Sub-unit fiber density is the total number of optical fibers in a cable 10 divided by the cross-sectional area of the cable sub-unit defined by the inner jacket 12. The cross-sectional area may be calculated as pi times the square root of the maximum radius of the inner jacket 12, and the maximum radius may be half of the maximum outer diameter 60 of the inner jacket 12. Further, cables 10 in accordance with the present disclosure may have such relatively high fiber densities and sub-unit fiber densities while advantageously meeting the OFNR-LS / FT4, and / or OFNP / FT6 requirements as discussed herein. Meeting such requirements may require that maximum wall thicknesses 62, 66 of the inner jacket 12 and outer jacket 18, respectively, may be relatively high for relatively low maximum outer diameters 60, 64 of the inner jacket 12 and outer jacket 18, respectively, thus further illustrating the advantageously high fiber densities achieved in accordance with the present disclosure.

[0055] For example, in some embodiments, the inner jacket thickness 62 may be between about 0.5 millimeters and about 2.3 millimeters, such as between about 0.5 and about 0.7 millimeters, such as between about 0.8 and about 1.5 millimeters, such as between about 0.95 and about 1.05 millimeters, such as between about 1.05 and about 1.15 milllimeters, such as between about 1.3 millimeters and about 1.5 millimeters, such as between about 2.1 millimeters and about 2.3 millimeters, such as about 0.65 millimeters, such as about 1.0 millimeters, such as about 1.1 millimeters, such as about 1.4 millimeters, such as about 2.2 millimeters. Further, in some embodiments, the inner jacket thickness 62 may be between about 7 percent and about 14 percent of the central sub-unit (e.g. inner jacket) outer diameter 60. In some embodiments, the outer jacket thickness 66 may be between about 0.7 millimeters and about 3.7 millimeters, such as between about 1.15 millimeters and about 1.25 millimeters, such between about 1.35 millimeters and about 1.45 millimeters, such as between about 1.55 millimeters and about 1.65 millimeters, such as between about 3.5 millimeters and about 3.7 millimeters, such as about 1.2 millimeters, such as about 1.4 millimeters, such as about 1.6 millimeters, such as about 3.6 millimeters. Further, in some embodiments, the outer jacket thickness 66 may be between about 7 percent and about 17 percent of the outer diameter 64.

[0056] In some embodiments, the sub-unit fiber density may be between about 6.3 and about 11.3 fiber per square millimeter, such as between about 7.5 fibers per square millimeter and about 7.7 fibers per square millimeter, such as between about 8.25 fibers per square millimeter and about 9.0 fibers per square millimeter, such as between about 9.7 fibers per square millimeter and about 11.1 fibers per square millimeter. In some embodiments, the sub-unit fiber density may be between about 1.5 and about 2.4 times the fiber density of the cable 10, such as about 7.61 fibers per square millimeter, such as about 8.3 fibers per square millimeter, such as about 8.77 fibers per square millimeter, such as about 8.95 fibers per square millimeter, such as about 9.78 fibers per square millimeter, such as about 10.99 fibers per square millimeter.

[0057] In some embodiments, the fiber density may be between about 3.1 fibers per square millimeter and about 8.38 fibers per square millimeter (such as for cable 10 fiber counts between 145 fibers and 6912 fibers), such as between about 3.1 fibers persquare millimeter and about 5.6 fibers per square millimeter (such as for cable 10 fiber counts between 145 fibers and 432 fibers), such as between about 3.1 fibers per square millimeter and about 4.1 fibers per square millimeter (such as for cable 10 fiber counts between 145 fibers and 288 fibers), such as between about 4.0 fibers per square millimeter and about 4.5 fibers per square millimeter (such as for cable 10 fiber counts between 289 fibers and 432 fibers), such as between about 4.0 fibers per square millimeter and about 5.9 fibers per square millimeter (such as for cable 10 fiber counts between 433 fibers and 576 fibers), such as between about 4.5 fibers per square millimeter and about 6.6 fibers per square millimeter (such as for cable 10 fiber counts between 577 fibers and 864 fibers), such as between about 5.45 fibers per square millimeter and about 7.7 fibers per square millimeter (such as for cable 10 fiber counts between 865 fibers and 1728 fibers), such as between about 5.61 fibers per square millimeter and about 8.38 fibers per square millimeter (such as for cable 10 fiber counts between 1729 fibers and 6912 fibers), such as about 4.06 fibers per square millimeter, such as about 4.39 fibers per square millimeter, such as about 4.77 fibers per square millimeter, such as about 5.38 fibers per square millimeter, such as about 6.43 fibers per square millimeter, such as about 6.79 fibers per square millimeter.

[0058] Cables 10 in accordance with the present disclosure may further advantageously have relatively high sub-unit fill percentages. As utilized herein, the sub-unit fill percentage is the area within an inner diameter 61 of the inner jacket 12 that is filled (by for example, fibers 14 (which may be in the form of ribbons 40 or bundles 50) and / or first strength members 16) divided by the total area within the inner diameter 61, multiplied by 100. In some embodiments, the sub-unit fill percentage may be between about 42% and about 51%, such as between about 44% and about 49%, such as between about 44% and about 45.5%, such as between about 47% and about 49%, such as about 44.8%, such as about 45.1%, such as about 45.3%, such as about 45.7%, such as about 47.6%, such as about 48.7%.

[0059] In exemplary embodiments, the maximum outer diameter of the inner jacket 12 may be between about 6 millimeters and about 30 millimeters, such as between about 6.2 millimeters and about 6.6 millimeters, such as between about 8.3 millimeters and about 8.7 millimeters, such as between about 9.2 millimeters andabout 9.6 millimeters, such as between about 11 millimeters and about 11.4 millimeters, such as between about 14.8 millimeters and about 15.2 millimeters, such as between about 28.1 millimeters and about 28.5 millimeters, such as about 6.4 millimeters, such as about 8.5 millimeters, such as about 9.4 millimeters, such as about 11.2 millimeters, such as about 15.0 millimeters, such as about 28.3 millimeters.

[0060] In exemplary embodiments, the maximum outer diameter of the outer jacket 18 may be between about 9 millimeters and about 37 millimeters, such as between about 9.3 millimeters and about 9.7 millimeters, such as between about 11 millimeters and about 11.4 millimeters, such as between about 12.2 millimeters and about 12.6 millimeters, such as between about 14.1 millimeters and about 14.5 millimeters, such as between about 18.3 millimeters and about 18.7 millimeters, such as between about 35.8 millimeters and about 36.2 millimeters, such as about 9.5 millimeters, such as about 11.2 millimeters, such as about 12.4 millimeters, such as about 14.3 millimeters, such as about 18.5 millimeters, such as about 36.0 millimeters.

[0061] Table 1 below provides various dimensions for cables 10 in accordance with exemplary embodiments of the present disclosure:Table 1: Cable Dimensions

[0062] Cables 10 in accordance with the present disclosure may further advantageously meet one or more requirements of Telecordia GR-409 Generic Requirements for Indoor Fiber Optic Cable (GR-409 Issue 2, November 2008) for Horizontal Backbone Cable applications. In particular, such cables 10 may meet the GR-409 requirements for outer jacket shrinkage, compressive strength / resistance, tensile strength, temperature cycling, low-high temperature bend, impact resistance, cable twist, cyclic flexing, and / or cold impact. For example, in some embodiments, a cable 10 in accordance with the present disclosure may have a tensile strength of at least 150 pounds with a strain percentage of less than 0.200%. In some embodiments, a cable 10 in accordance with the present disclosure may exhibit an attenuation change of less than or equal to 0.30 dB, such as less than or equal to 0.003 dB, when subjected to 4 bends around a 7-inch diameter mandrel and with a 12.5 kg weight suspended at the end of the 4 wraps at both 0 °C and 70 °C. In some embodiments, a cable 10 in accordance with the present disclosure may exhibit an attenuation change of less than or equal to 0.003 dB when subjected to 25 cycles in a 180 degree arc (90 degrees clockwise and 90 degrees counterclockwise) with a 5 kg load attached to the end. The cable 10 may exhibit no visible cracks, tears, or other openings in the outer jacket thereof after such testing. In some embodiments, a cable 10 in accordance with the present disclosure may exhibit an attenuation change of less than or equal to 0.003 dB / f when subjected to a minimum of 10 cycles of being twisted 180 degrees clockwise and counter-clockwise. In some embodiments, a cable 10 in accordance with the present disclosure may exhibit an attenuation change of less than or equal to 0.20 dB, such as less than or equal to 0.115 dB, when subjected to a compressive load of at least 100 N / cm over a period of 10 minutes. The cable 10 may exhibit no visible cracks, tears, or other openings in the outer jacket thereof after such testing. In some embodiments, a cable 10 in accordance with the present disclosure may exhibit an attenuation change of less than or equal to 0.20 dB, such as less than or equal to 0.001 dB, when subjected to 2 impacts of 2.0 kg at 3 locations from a height of 150mm. In some embodiments, a cable 10 in accordance with the present disclosure may exhibit an attenuation change of less than or equal to 0.3dB / km at 1550 nm, such as less than or equal to 0.04 dB / km at 1550 nm, when subjected to extreme temperatures over 120 hours ranging from 0 °C to 70 °C including multiple exposurecycles at the extreme temperatures for 24 continuous hours within the 120 hours. The cable 10 may exhibit no visible cracks, tears, or other openings in the outer jacket thereof after such testing. In some embodiments, a cable 10 in accordance with the present disclosure may exhibit shrinkage of less than 5%, such as less than or equal to 2.00%, after being subjected to 110 °C temperature for two hours. In some embodiments, a cable 10 in accordance with the present disclosure may exhibit no visible cracks, tears, or other openings in the outer jacket thereof after preconditioning at -10 °C for four hours and then being subjected to an impact of a 2 kg load from a height of 150 mm.

[0063] Cables in accordance with the present disclosure may further advantageously meet the UL 1666 riser cables fire test standard. For example, in some embodiments, a cable 10 in accordance with the present disclosure may exhibit a maximum flame propagation of less than or equal to 12 feet, such as less than or equal to 4 feet, such as less than or equal to 3 feet six inches. Further, a cable 10 in accordance with the present disclosure may exhibit a maximum temperature of less than or equal to 850 °F, such as less than or equal to 363 °F, such as less than or equal to 353 °F.

[0064] With reference now to FIG. 6, the present disclosure is further directed to cable assemblies 100 which include cables 10. Such cable assemblies 100 may further include one or more connectors 110. Such connectors 110 may be terminated to one or both ends of one or more optical fibers 14 of a cable 10. Accordingly, such cable assemblies 100 may in exemplary embodiments be pre-terminated. The ends of the fibers 14 may further be furcated with furcation tubes 120 as required to facilitate such connector 110 terminations. Suitable connectors 110 for use with such cable assemblies 100 include, for example, single-fiber connectors, such as for example SC, LC, ST, MU or E2000 style connectors, or duplex or quad connectors such as SN, MDC, CS, or MTRJ connectors, and / or multi-fiber connectors, such as MPO, MTP, SN-MT, MMC, or MXC connectors.

[0065] Further aspects of the disclosure are provided by one or more of the following embodiments:

[0066] A microcable including a central inner jacket formed from a flame retardant material, and a plurality of optical fibers disposed within the inner jacket,wherein a total number of optical fibers in the fiber optic microcable is greater than or equal to 145. The microcable further includes a plurality of first strength members disposed within the inner jacket, an outer jacket surrounding the central inner jacket, the outer jacket formed from a flame retardant material, and a plurality of second strength members disposed between the outer jacket and the central inner jacket, a fiber density of the cable is between about 3.1 fibers per square millimeter and about 8.38 fibers per square millimeter.

[0067] A cable assembly including a microcable. The microcable includes a central inner jacket formed from a flame retardant material, and a plurality of optical fibers disposed within the inner jacket, wherein a total number of optical fibers in the fiber optic microcable is greater than or equal to 145. The microcable further includes a plurality of first strength members disposed within the inner jacket, an outer jacket surrounding the central inner jacket, the outer jacket formed from a flame retardant material, and a plurality of second strength members disposed between the outer jacket and the central inner jacket, a fiber density of the cable is between about 3.1 fibers per square millimeter and about 8.38 fibers per square millimeter. The cable assembly further includes a plurality of connectors, each of the plurality of connectors terminated to one or more optical fibers of the plurality of optical fibers.

[0068] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein a sub-unit fiber density of the cable is between about 6.3 and about 11.3 fiber per square millimeter.

[0069] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein a sub-unit fill percentage of the cable is between about 42% and about 51%.

[0070] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the first strength members and the second strength members include aramid fibers.

[0071] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the first and second strength members are stranded.

[0072] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the first strength members includearamid yams, and wherein each aramid yam has a weight between 600 denier and 2840 denier.

[0073] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein a total weight of the first strength members and second strength members is between 17,000 denier and 37,000 denier.

[0074] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the central inner jacket and outer jacket are each formed from one of a polyvinyl chloride or a low smoke zero halogen material.

[0075] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the total number of optical fibers in the fiber optic microcable is greater than or equal to 288.

[0076] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the plurality of optical fibers have nominal outer diameters of 200 microns.

[0077] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the plurality of optical fibers each have a maximum fiber attenuation of less than or equal to 0.35 dB / km at 1310 nanometers and less than or equal to 0.25 dB / km at 1550 nanometers.

[0078] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the optical fibers are ribbonized to form an intermittently-bonded ribbon.

[0079] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the optical fibers are bundled into one or more fiber optic bundles.

[0080] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the cable has a tensile strength of greater than or equal to 150 pounds.

[0081] The fiber optic microcable and / or cable assembly of any one or more embodiments shown or described herein, wherein the cable complies with at least one requirement of the Telecordia GR-409 Generic Requirements for Indoor Fiber Optic Cable (GR-409 Issue 2, November 2008) for Horizontal Backbone Cable applications.

[0082] This written description uses examples to disclose the present application, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

WHAT IS CLAIMED IS:

1. A fiber optic microcable, comprising: a central inner jacket formed from a flame retardant material; a plurality of optical fibers disposed within the inner jacket, wherein a total number of optical fibers in the fiber optic microcable is greater than or equal to 145; a plurality of first strength members disposed within the inner jacket; an outer jacket surrounding the central inner jacket, the outer jacket formed from a flame retardant material; and a plurality of second strength members disposed between the outer jacket and the central inner jacket, wherein a fiber density of the cable is between about 3.1 fibers per square millimeter and about 8.38 fibers per square millimeter.

2. The fiber optic microcable of claim 1, wherein a sub-unit fiber density of the cable is between about 6.3 and about 11.3 fiber per square millimeter.

3. The fiber optic microcable of claim 1, wherein a sub-unit fill percentage of the cable is between about 42% and about 51%.

4. The fiber optic microcable of claim 1, wherein the first strength members and the second strength members include aramid fibers.

5. The fiber optic microcable of claim 1, wherein the first strength members include aramid yarns, and wherein each aramid yarn has a weight between 600 denier and 2840 denier.

6. The fiber optic microcable of claim 1, wherein a total weight of the first strength members and second strength members is between 17,000 denier and 37,000 denier.

7. The fiber optic microcable of claim 1, wherein the central inner jacket and outer jacket are each formed from one of a polyvinyl chloride or a low smoke zero halogen material.

8. The fiber optic microcable of claim 1, wherein the total number of optical fibers in the fiber optic microcable is greater than or equal to 288.

9. The fiber optic microcable of claim 1, wherein the plurality of optical fibers have nominal outer diameters of 200 microns.

10. The fiber optic microcable of claim 1, wherein the plurality of optical fibers each have a maximum fiber attenuation of less than or equal to 0.35 dB / km at 1310 nanometers and less than or equal to 0.25 dB / km at 1550 nanometers.

11. The fiber optic microcable of claim 1, wherein the optical fibers are ribbonized to form an intermittently-bonded ribbon.

12. The fiber optic microcable of claim 1, wherein the optical fibers are bundled into one or more fiber optic bundles.

13. The fiber optic microcable of claim 1, wherein the cable has a tensile strength of greater than or equal to 150 pounds.

14. The fiber optic microcable of claim 1, wherein the cable complies with at least one requirement of the Telecordia GR-409 Generic Requirements for Indoor Fiber Optic Cable (GR-409 Issue 2, November 2008) for Horizontal Backbone Cable applications.

15. A cable assembly, comprising: a microcable, comprising: a central inner jacket formed from a flame retardant material; a plurality of optical fibers disposed within the inner jacket, wherein a total number of optical fibers in the fiber optic microcable is greater than or equal to 145; a plurality of first strength members disposed within the inner jacket; an outer jacket surrounding the central inner jacket, the outer jacket formed from a flame retardant material; and a plurality of second strength members disposed between the outer jacket and the central inner jacket, wherein a fiber density of the cable is between about 3.1 fibers per square millimeter and about 8.38 fibers per square millimeter; and a plurality of connectors, each of the plurality of connectors terminated to one or more optical fibers of the plurality of optical fibers.

16. The cable assembly of claim 15, wherein a sub-unit fiber density of the cable is between about 6.3 and about 11.3 fiber per square millimeter.

17. The cable assembly of claim 15, wherein a sub-unit fill percentage of the cable is between about 42% and about 51%.

18. The cable assembly of claim 15, wherein the plurality of optical fibers each have a maximum fiber attenuation of less than 0.4 dB / km at -40 degrees Celsius at 1310 nanometers and 1550 nanometers.

19. The cable assembly of claim 15, wherein the cable has a tensile strength of greater than or equal to 150 pounds.

20. The cable assembly of claim 15, wherein the cable complies with at least one requirement of the Telecordia GR-409 Generic Requirements for Indoor Fiber Optic Cable (GR-409 Issue 2, November 2008) for Horizontal Backbone Cable applications.

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