Membrane material formed from stripe of immiscible polymers for finger peelable optical fiber subunit

Abstract

Provided are embodiments of a membrane of an optical fiber subunit. The optical fiber subunit includes a first section formed of a first polymer composition and at least one second section formed of a second polymer composition. The first polymer composition includes a first thermoplastic polymer. The second polymer composition includes a blend of the first thermoplastic polymer and a second thermoplastic polymer that is immiscible with the first thermoplastic polymer. The at least one second section and the first section define an outer perimeter of an outer surface of the membrane. The at least one second section extends from 5% to 85% around the perimeter.

Description

Attorney Docket No. HI24-111PCTMEMBRANE MATERIAL FORMED FROM STRIPE OF IMMISCIBLE POLYMERS FOR FINGER PEELABLE OPTICAL FIBER SUBUNITCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of U.S. Provisional Application No. 63 / 699,292, filed on September 26, 2024, the content of which is relied upon and incorporated herein by reference in its entirety.BACKGROUND OF THE DISCLOSURE

[0002] The present disclosure generally relates to optical fiber cables and in particular to a subunit having a membrane with a stripe of immiscible polymers for peelability and subunit identification.

[0003] In general, an optical fiber cable needs to carry more optical fibers in order to transmit more optical data, and in order to carry more optical fibers, the size of the optical fiber cable conventionally needed to be increased. The increased size is at least partially the result of free space considerations to avoid macro- and micro- bending attenuation losses. For existing installations, size limitations and duct congestion limit the size of optical fiber cables that can be used without the requirement for significant retrofitting. Thus, it may be desirable to provide optical fiber cables having a higher fiber density (i.e., more fibers per cross-sectional area of the cable) without increasing the cable diameter such that the high fiber density cables can be used in existing ducts. Notwithstanding the desire for increased fiber density, organization and access to the optical fibers needs to be maintained. Conventional buffer tubes provide organization but are also thick and take up substantial space, decreasing fiber density and potentially making access difficult.SUMMARY OF THE DISCLOSURE

[0004] In a first aspect, embodiments of the present disclosure relate to a membrane of an optical fiber subunit. The optical fiber subunit comprises a first section comprising a first polymer composition and at least one second section comprising a second polymer composition. The first polymer composition comprises a first thermoplastic polymer. The second polymer composition comprises a blend of the first thermoplastic polymer and a second thermoplastic polymer that is immiscible with the first thermoplastic polymer. The at least one second section and the first section define an outer perimeter of an outer surfaceAttorney Docket No. HI24-111PCT of the membrane. The at least one second section extends from 5% to 85% around the perimeter.

[0005] In a second aspect, embodiments of the present disclosure relate to a routable base unit. The routable base unit includes a plurality of optical fibers and the membrane according to the first aspect in which the membrane surrounds the plurality of optical fibers. The membrane has a thickness of 100 pm or less.

[0006] In a third aspect, embodiments of the present disclosure relate to an optical fiber cable. The optical fiber cable comprises a cable jacket comprising an inner surface and an outer surface. The inner surface defines a central bore extending along a longitudinal axis of the optical fiber cable, and the outer surface defines an outermost surface of the optical fiber cable. A plurality of routable base units (RBU) disposed within the central bore. Each RBU of the plurality of RBU comprises a plurality of optical fibers and a membrane surrounding the plurality of optical fibers. The membrane has a thickness of 100 pm or less. The membrane comprises at least one stripe of a first polymer composition within a second polymer composition. The at least one stripe of the first polymer composition is configured to peel apart from the second polymer composition at an average peel strength as measured transverse to an extrusion direction of the membrane of 4 N or less.

[0007] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0008] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments. In the drawings:

[0010] FIG. 1 depicts a cross-sectional view of a high fiber density optical fiberAttorney Docket No. HI24-111PCT cable, according to exemplary embodiments;

[0011] FIG. 2 is a schematic depiction of a membrane of an optical fiber subunit having a first section and a second section that extends through a thickness of the membrane, according to exemplary embodiments;

[0012] FIG. 3 is a schematic depiction of a membrane of an optical fiber subunit having a first section and a second section that extends only partially through the thickness of the membrane, according to exemplary embodiments;

[0013] FIG. 4 is flow diagram of a method for preparing a membrane of an optical fiber subunit, according to an exemplary embodiment;

[0014] FIG. 5 is a photograph of membranes having varying amounts of the second section extruded together with the first section, according to an exemplary embodiment; and

[0015] FIG. 6 is a photograph depicting membranes with stripes of differently colored materials, according to an exemplary embodiment.DETAILED DESCRIPTION

[0016] Embodiments of the present disclosure relate to an optical fiber subunit having a membrane that surrounds optical fibers in which the membrane is configured to provide enhanced accessibility and subunit identification. Optical fiber cables organize components into various structures using, for example, jackets, tubes, membranes, or binders. To access the components within those structures, often specialized tools are required, and accessing the structures can damage the components within. According to embodiments of the present disclosure, a membrane of a subunit includes at least one stripe of membrane material that provides at least one of enhanced peelability of the membrane or a color-based marking for identification. As will be discussed more fully below, the membrane can include more than one stripe, include stripes of different widths, or include stripes that partially or fully extend through a thickness of the membrane, amongst other possibilities. In this way, the properties of the membrane can be tailored to achieve a specific level of membrane peelability (and thus subunit accessibility) and / or an expandable color-coding scheme for subunit identification in cable cores with a wide range of optical fibers.

[0017] In this regard, the stripe of material in the membrane may be a different color and / or composition than the rest of the material of the membrane. Certain embodiments ofAttorney Docket No. HI24-111PCT the present disclosure utilize a blend of immiscible polymers that form co-continuous phases to establish tear paths for the membrane. These and other aspects and advantages of the disclosed subunit membrane will be described in greater detail below and in relation to the accompanying figures. These exemplary embodiments are provided by way of illustration, and not by way of limitation.

[0018] FIG. 1 depicts an example embodiment of a high fiber density optical fiber cable 10. The optical fiber cable 10 includes a cable jacket 12 having an inner surface 14 and an outer surface 16. The inner surface 14 of the optical fiber cable 10 defines a central bore 18 that extends along a longitudinal axis of the optical fiber cable 10. Disposed within the central bore 18 of the optical fiber cable 10 is cable core 20 including a plurality of subunits referred to herein as routable base units (RBU) 22. The RBU 22 each include a plurality of optical fibers 24 surrounded by a membrane 26. The membrane 26 is a thin and flexible sheath that allows for the RBU 22 to be reconfigured into a variety of different shapes. In this way, the RBU 22 can be densely packed within the cable core 20 by changing shape, e.g., flattening out, bunching up, or bending, as necessary to fill space within the cable core 20.

[0019] In one or more embodiments, the interior surface of the membrane 26 defines an interior cross-sectional area of the RBU 22. The portion of this interior cross-sectional area that is not occupied by the optical fibers 24 is referred to as “free space.” In one or more embodiments, each RBU 22 comprises a free space of 50% or less, 40% or less, 30% or less, or 25% or less. The low free space within the RBU 22 contributes to the high fiber density of the optical fiber cable 10. In one or more embodiments, the RBU 22 may also include a water-blocking material, such as a water-blocking gel, super-absorbent powders, or water-blocking yarn.

[0020] In one or more embodiments, the RBU 22 may be stranded (such as SZ- stranded) in the cable core 20 in embodiments. The stranding enhances the ability to bend the cable while minimizing tensile and contractive forces within any of the fibers. During cable bending, the optical fibers 24 must be able to shift position, moving longitudinally to relieve those forces so as not to cause attenuation or break the optical fibers 24. Because the membranes 26 and cable core 20 do not provide free space for the optical fibers 24 to increase fiber density by design, the RBU 22 may be configured to move relative to each other in certain embodiments by using solid or gel lubricants, such as talc, or using waterabsorbing powders.Attorney Docket No. HI24-111PCT

[0021] Thus, in one or more embodiments, the optical fiber cable 10 may consist essentially of the cable jacket 12 surrounding a plurality of RBU 22. Other components that do not affect the basic and novel characteristics of the optical fiber cable 10 that may be included are, for example, a binder 28 provided between the plurality of RBU 22 and the cable jacket 12, water blocking material (e.g., tapes and powders), lubricants, frictionenhancing materials, and access features (e.g., ripcords or preferential tear features, such as a strip of dissimilar polymer in the cable jacket 12). In one or more embodiments, armor layers and strength elements are excluded from the construction of the optical fiber cable 10.

[0022] In one or more embodiments, the thickness of the membrane 26 is 100 pm or less, 90 pm or less, 80 pm or less, 70 pm or less, 60 pm or less, 50 pm or less, or 40 pm or less. In one or more embodiments, the thickness of the membrane 26 is 10 pm or more, 20 pm or more, 30 pm or more, or 35 pm or more. In one or more embodiments, the thickness of the membrane 26 is from 10 pm to 100 pm, in particular from 10 pm to 60 pm, and most particularly from 25 pm to 50 pm.

[0023] In one or more embodiments, the membrane 26 groups from two to one hundred forty-four in particular from eight to ninety-six, and particularly from twelve to twenty-four, optical fibers 24 into an RBU 22.

[0024] In one or more embodiments, the RBU 22 are surrounded by a binder 28. In one or more embodiments, the binder 28 is a thin film jacket having a thickness between 40 pm and 150 pm. In one or more embodiments, the binder 28 is provided to prevent sticking between the RBU 22 and the cable jacket 12, and thus, in one or more embodiments, the material of the binder 28 is selected to prevent sticking to both the RBU 22 and the cable jacket 12. Advantageously, using a thin the binder 28 having a thickness in the disclosed thickness range reduces the thermal load of the binder 28 on the RBU 22 during extrusion of the binder 28.

[0025] In one or more embodiments, the cable jacket 12 has a thickness between the inner surface 14 and the outer surface 16 in a range from 0.5 mm to 1 mm. In particular embodiments, the cable jacket 12 has a thickness that is from 8% to 10% of the outer diameter of the optical fiber cable 10 (as measured at the outer surface 16 of the cable jacket 12). In one or more embodiments, the cable jacket 12 is made from a polyethylene material (such as high density polyethylene (HDPE)), a low-smoke zero halogen (LSZH) polymer, a filled polyethylene, a flame retardant (FR) polymer, or a urethane polymer, amongst otherAttorney Docket No. HI24-111PCT possibilities.

[0026] In one or more embodiments, the cable jacket 12 includes tactile locator features 30. In the embodiment depicted, the tactile locator features 30 comprise diametrically arranged depressions defined by the outer surface 16 of the cable jacket 12. However, in one or more other embodiments, the tactile locator features 30 comprise diametrically arranged bumps defined by the outer surface 16 of the cable jacket 12. The tactile locator features 30 assist a user in opening the cable 10 by guiding the user to the location of access features 32. In the embodiment of the optical fiber cable 10, the access features 32 are strips of dissimilar polymer embedded in the polymer of the cable jacket 12. For example, the cable jacket 12 may substantially comprise polyethylene, and the dissimilar polymer of the access feature 32 may be polypropylene. The immiscibility of polyethylene cable jacket 12 and the polypropylene access features 32 prevents a strong bond from forming between the cable jacket 12 and the access features 32, allowing for a user to tear through the cable jacket 12 in the region of the access features 32. Further, once opened at the access features 32, the cable jacket 12 can be split along its length along the access features 32.

[0027] In one or more embodiments, the optical fiber cable 10 includes from 48 to 864 optical fibers 24, or from 96 to 576 optical fibers 24, or from 144 to 288 optical fibers 24. In one or more embodiments, the optical fiber cable 10 has a fiber density of at least 7.5 fibers / mm2. The fiber density is measured based on the number of optical fibers 24 per cross-sectional area of the optical fiber cable 10 as measured from the outer surface 16. In one or more embodiments, the fiber density is at least 8 fibers / mm2, at least 8.5 fibers / mm2, at least 9 fibers / mm2, at least 9.5 fibers / mm2, at least 10 fibers / mm2, at least 10.5 fibers / mm2, at least 11 fibers / mm2, at least 11.5 fibers / mm2, or at least 12 fibers / mm2. In one or more embodiments, the fiber density may be up to 17 fibers / mm2. Further, in one or more embodiments, the outer diameter of the optical fiber cable 10 as measured at the outer surface 16 is 9 mm or less, 8.5 mm or less, 8 mm or less, 7.5 mm or less, 7 mm or less, 6.75 mm or less, 6.5 mm or less, 6.25 mm or less, 6 mm or less, 5.75 mm or less, 5.5 mm or less, 5.25 mm or less, or 5 mm or less. Further, in one or more embodiments, the outer diameter of the optical fiber cable 10 as measured from the outer surface 16 is at least 2 mm.

[0028] In one or more embodiments, the optical fiber cable 10 has a cumulative fiber filling coefficient of at least 50%, at least 60%, at least 65%, or at least 70%. In one or more embodiments, the optical fiber cable 10 has a cumulative fiber filling coefficient of upAttorney Docket No. HI24-111PCT to 85%. As used herein, the term “cumulative fiber filling coefficient” of an optical-fiber cable 10 refers to the ratio of the sum of the cross-sectional areas of all of the optical fibers 24 within the optical -fiber cable 10 versus the inner cross-sectional area of the optical -fiber cable 10 (i.e., defined by the inner surface 14 of the cable jacket 12 or inner surface of binder 28, if included). The cross-sectional area of each optical fiber 24 is determined based on an outer surface of the optical fiber 24.

[0029] In one or more embodiments, the optical fiber cable 10 comprises a free space of at most 50%, at most 42.5%, at most 30%, or at most 25%. In one or more embodiments, the free space of the optical fiber cable 10 is at least 15%. As used herein, the free space is the inverse of cumulative fiber filling coefficient (i.e., 100% - cumulative fiber filling coefficient).

[0030] According to embodiments of the present disclosure, the RBU 22 comprise a membrane 26 that is (1) colored in such as manner as to provide subunit organization and identification and (2) configured to be finger-peelable without damaging the optical fibers 24 within the RBU 22. With respect to subunit organization and identification, the optical fiber cable industry has widely adopted a color-coding scheme that is based on twelve colors: blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, and aqua. Such a color code is used for optical fibers within the optical fiber cable and also for subunits. Issues arise, however, where the optical fiber cable contains more than twelve of the components where the color code is to be used, especially subunits. Subunits are generally formed form extruded polymers, and conventional methods of distinguishing between multiple sets of twelve optical fibers, such as ring-marking, do not readily lend themselves to subunits without substantial modification to the subunit processing line. Moreover, techniques such as ring-marking do not address the additional issue of creating a finger-peelable subunit jacket.

[0031] To address the issue of providing a finger peelable membrane 26 for the RBU 22 of the optical fiber cable 10, Applicant developed a blend of immiscible or partially miscible polymers for the membrane 26 as disclosed in PCT Application No. PCT / US2024 / 030488, filed on May 22, 2024, and titled “MEMBRANE MATERIAL HAVING IMMISCIBLE POLYMERS FOR USE IN OPTICAL FIBER CABLE STRUCTURES,” the contents of which are incorporated herein in their entirety by reference thereto. As disclosed there, the average peel strength of the membrane 26 as measured transverse to the extrusion direction is 4 N or less, 3 N or less, 2 N or less, 1.5 N or less, or 1Attorney Docket No. HI24-111PCT N or less, such as in a range from 0.25 N to 4 N, for example. In one or more embodiments, the optical fiber cable 10 may include a cable core 20 having twelve RBU (referred to therein as “lumens”) 22 having membranes 26 of the type described in PCT Application No. PCT / US2024 / 030488, color-coded according to the conventional twelve color scheme identified above.

[0032] Instead of the membranes 26 as disclosed in PCT Application No. PCT / US2024 / 030488, or in addition to such membranes 26 where there are more than twelve RBU 22 within the cable core 20, the presently disclosed membrane 26 for at least some of the RBU 22 in the cable core 20 is comprised of a first membrane material having at least one stripe of a second membrane material extending continuously or discontinuously along the length thereof. As will be discussed more fully below, the stripe of the second membrane material is a single polymer or blend of immiscible polymers including at least one polymer contained in the first membrane material in which the first membrane material may be a single polymer or a different blend of immiscible polymers. In this way, the at least one stripe of the second membrane material can be used as a tear path for peeling the membrane 26 apart. Further, the at least one stripe of the second membrane material can be a different color than the first membrane material in order to provide identification of subunits with the optical fiber cable 10. As such, the membrane 26 according to embodiments of the present disclosure meets the objectives of providing color-based subunit organization and identification and ease of accessibility without damaging the optical fibers 24 within the RBU 22.

[0033] FIG. 2 is a schematic representation of a membrane 26 according to the present disclosure including a first section 40 of a first membrane material with at least one second section 42 of a second membrane material. Together the first section 40 and the at least one second section 42 define an entirety of the outer perimeter of the membrane 26 (depicted in FIG. 2 as an outer circumference of a circular membrane 26). In one or more embodiments, the at least one second section 42 comprises one, two, or three second sections 42. In one or more embodiments, the at least one second section 42 (whether an individual second section 42 or multiple second sections 42) extends from 5% to 85%, in particular 20% to 30%, around the outer perimeter of the membrane 26.

[0034] In one or more embodiments, such as shown as FIG. 2, the at least one second section 42 extends through the entire thickness of the membrane 26 from an outer surface 44 of the membrane 26 to an inner surface 46 of the membrane 26. However, in oneAttorney Docket No. HI24-111PCT or more other embodiments, such as shown in FIG. 3, the at least one second section 42 does not extend through the entire thickness of the membrane 26. For example, in one or more embodiments, the at least one second section 42 extends from the outer surface 44 toward the inner surface 46 up to 20%, 50%, or 80% of the thickness of the membrane 26.

[0035] As shown in FIGS. 2 and 3, the at least one second section 42 forms at least one interface 48 with the first section 40. As shown in FIG. 2, each of the at least one second sections 42 that extends through the thickness of the membrane 26 will form two interfaces 48 with the first section 40, and as shown in FIG. 3, each of the at least one second sections 42 forms one continuous interface 48 with the first section 40. The level of bonding at the interfaces 48 can be controlled through the selection of the materials for the first section 40 and the at least one second section 42.

[0036] In one or more embodiments, the first section 40 comprises a first polymer composition and the at least one second section 42 comprises a second polymer composition. In one or more embodiments, the first polymer composition comprises a single polymer or a first blend of polymers having a primary polymer (i.e., a polymer present in the most amount within the first blend) and one or more ancillary polymers. In one or more embodiments, the second polymer composition comprises a second blend of polymers comprising from 5% to 95% by weight, in particular 15% to 80% by weight, of the single polymer or of the primary polymer. If the first polymer composition is the first blend of polymers, then the second polymer composition may instead be a single polymer that is the primary polymer of the first blend of polymers.

[0037] In one or more embodiments in which the first polymer composition is a single polymer, the single polymer is a thermoplastic polymer and is not particularly limited in terms of molecular weight and distributions. The thermoplastic polymer may be homopolymer, heteropolymer, or copolymer. In general, the thermoplastic polymer can be selected from among a polyolefin, polyvinylchloride, polystyrene, acrylonitrile butadiene styrene, styrene-acrylonitrile, styrene-ethylene-butylene-styrene, and a technical thermoplastic. In one or more embodiments, the polyolefin is a polyethylene (very low density, linear low density, low density, medium density, high density, or ultrahigh molecular weight), a polypropylene (isotactic, syndiotactic, or atactic), or a polyolefin-based thermoplastic elastomer (such as ethylene vinyl acetate, ethylene butyl acrylate, ethylene methyl acrylate, thermoplastic olefin elastomer, ethylene-propylene rubber, or ethylene propylene diene monomer rubber). In one or more embodiments, the technicalAttorney Docket No. HI24-111PCT thermoplastic is a polyester (such as polybutylene terephthalate, polyethylene terephthalate, polycarbonate, poly methyl methacrylate, or polyoxymethylene), a polyether (such as polyphenylene ether or poly(p-phenylene oxide)), a polyamide (such as polyamide 6, polyamide 12, polyamide 6.6, polyamide 4.6, or polyamide 11), polyacetal, a polysulfone (such as polyethersulfone, polysulfone, or polyphenylene sulfide), a polyimide, or a polyketone.

[0038] In one or more embodiments in which the first polymer composition is a first blend of polymers, the first blend includes two or more partially miscible or immiscible polymers selected from the thermoplastic polymers listed above in relation to the single polymer.

[0039] In one or more such embodiments, the second blend of polymers includes the primary polymer of the first blend of polymers but is otherwise different from the first blend of polymers. For example, the second blend of polymers may include different ancillary polymers than the first blend of polymers, or the second blend of polymers may include the same polymers but in different amounts (e.g., having one of the ancillary polymers of the first blend as the primary polymer of the second blend). The second blend of polymers also includes two or more partially miscible or immiscible polymers from the thermoplastic polymers listed above in relation to the single polymer. Further, as mentioned, the second polymer composition may be a single polymer if the first polymer composition is the first blend of polymers; in which case, the second polymer composition will be the primary polymer of the first blend of polymers.

[0040] By including the single polymer or the primary polymer of the first polymer composition in the second polymer composition, a customizable level of compatibility between the first section 40 and the at least one second section 42 is provided at the interface 48. That is, by incorporating more of the single polymer or primary polymer in the second blend of polymers, the second section 42 will have greater compatibility with the first section 40, and by incorporating less of the single polymer or primary polymer in the second blend of polymers, the second section 42 will have lesser compatibility with the first section 40. Higher compatibility will lead to a stronger adhesion between the first section 40 and the second section 42 at the interface 48, providing more robust mechanical properties, and lower compatibility will lead to weaker adhesion between the first section 40 and the second section 42 at the interface 48, providing enhanced peelability. In this way, the membrane 26 can be configured to withstand forces associated with cable processingAttorney Docket No. HI24-111PCT and installation without breaking while also remaining finger-peelable when access to the optical fibers is desired.

[0041] With respect to the embodiment shown in FIG. 2, the membrane 26 can be ruptured by peeling the at least one second section 42 from the first section 40. Because, in the embodiment of FIG. 2, the second section 42 extends through the thickness of the membrane 26, removing the second section 42 directly provides access to the interior of the membrane 26. With respect to the embodiment shown in FIG. 3, removal of the second section 42 creates a thin region of the first section 40, reducing the effort needed to tear the first section 40 to access the interior of the membrane 26. In one or more embodiments, the average peel strength of the membrane 26 as measured transverse to the extrusion direction to separate the at least one second section 42 from the first section 40 is 4 N or less, 3 N or less, 2 N or less, or 1 N or less, such as in a range from 0.25 N to 4 N, in particular in a range from 1 N to 2.5 N, for example.

[0042] In both of the cases of FIG. 2 and FIG. 3, the at least one second section 42 may include a colorant that makes the at least one second section 42 visually distinguishable from the first section 40. For example, the at least one second section 42 may form one or more visually distinguishable stripes that extend continuously or discontinuously along a length of the membrane 26. In one or more embodiments, the stripes extend continuously straight along the length of the membrane 26, discontinuously in straight segments along the length of the membrane, or continuously or discontinuously in curved, wavy, or spiral lines or segments along the length of the membrane 26.

[0043] In one or more other embodiments, the at least one second section 42 may be the same color as the first section 40. As discussed above, the first twelve RBU of an optical fiber cable may be solidly colored according to the twelve color scheme discussed above, and following sets of twelve subunits may include an increasing number of stripes to distinguish from previous sets of twelve subunits. In such a cable, the first twelve subunits may include membranes 26 having a second section 42 within the first section 40 primarily to provide access to the interior of the membrane 26. As mentioned, such membranes 26 may be used instead of the membranes of PCT Application No. PCT / US2024 / 030488 .

[0044] In one or more embodiments, the first and second polymer compositions of the membrane 26 include less than 10% of fillers. In one or more embodiments, the first and second polymer compositions do not include any fillers besides colorants. In one orAttorney Docket No. HI24-111PCT more embodiments, the colorant can be added through a color batch. In one or more embodiments, the membrane material includes color batch in an amount in a range from 1 wt% to 5 wt%, in particular about 3 wt%. Further, in one or more embodiments, the membrane 26 can included colored stripes of the first polymer composition and of the second polymer composition. The second polymer composition defining the second section 42 creates a peel feature, but where two or more stripes are desired to provide identification of the membrane 26, one of the color identification stripes can be formed using the first polymer composition (containing a different colorant than the rest of the first polymer composition) because a second peel feature is not needed.

[0045] Having described the optical fiber cable 10 and embodiments of a membrane 26, embodiments of a method 100 for manufacturing an optical fiber cable 10 including a plurality of RBU 22 will be described in relation to the flow diagram of FIG. 4. In one or more embodiments, the method 100 involves a first step 101 of coextruding a membrane 26 having the first section 40 and the at least one second section 42. Advantageously, blending of the polymers of the second polymer composition may be performed through dry blending pellets of one thermoplastic polymer (that is the same as the single polymer or primary polymer of the first thermoplastic polymer composition) with pellets of another thermoplastic polymer. That is, no further compounding steps are required to blend the immiscible polymers. Further, in one or more embodiments, the blending (including dry blending) may involve three or more thermoplastic polymers. Thereafter, the second polymer composition is co-extruded with the first polymer composition to form the first section 40 and the at least one second section 42 of the membrane 26.

[0046] In one or more embodiments, for a twelve-fiber RBU 22, the membrane 26 may be extruded around the optical fibers 24 while the optical fibers 24 are in a 3 x 4 rectangular or offset rectangular arrangement or a 2 x 6 rectangular or parallelogram arrangement. In these initial configurations, the RBU 22 may be able to more easily shift to the various space-saving configurations, such as those shown in FIG. 1, to provide a high fiber density optical fiber cable 10.

[0047] In one or more embodiments of the method 100, the RBU 22 are formed into a cable core 20 in a second step 102. In embodiments, the RBU 22 extend straight along the longitudinal axis of the optical fiber cable 10 in the cable core 20, and in other embodiments, the RBU 22 are stranded (e.g., S-stranded, Z-stranded, or SZ-stranded) along the longitudinal axis in the cable core 20.Attorney Docket No. HI24-111PCT

[0048] In one or more embodiments of the method 100, the binder 28 is optionally extruded around a plurality of RBU 22 in a third step 103. In a fourth step 104 of the method 100, a cable jacket 12 is then extruded around the RBU 22 or binder 28, as the case may be. During extrusion of the cable jacket 12, the access feature 32 and the tactile locator features 30 may be formed in the cable jacket 12 through the use of specially-configured extrusion die-heads. A vacuum may be pulled during extrusion of the cable jacket 12, which squeezes the cable jacket 12 down around the RBU 22. Additionally or alternatively, the cable jacket 12 can be made thicker, which results in greater shrinkage during cooling, compressing the RBU 22. Advantageously, by compressing the cable jacket 12 around the RBU 22, the individual RBU 22 may be manufactured with a higher than desired free space, and the force of the cable jacket 12 on the RBU 22 in the cable core 20 can reconfigure the RBU 22 into shapes with lower free space within the optical fiber cable 10.

[0049] EXPERIMENTAL EXAMPLES

[0050] As shown in FIG. 5, membranes 26 were extruded with a white material and a blue material. The membranes 26 each included a first section 40 that was a blend of polypropylene (PP) and high density polyethylene (HDPE) at a ratio of 85% / 15% by weight. Thus, the polymer composition of the first section 40 differed from the polymer composition of the second section 42 by color. The amount of blue material was varied from 0% of the perimeter of the membrane 26 (i.e., no second section 42, providing a white membrane) to 100% of the perimeter of the membrane 26 (i.e., no first section, providing a blue membrane). Strips of blue material covering 10%, 15%, 20%, 25%, 35%, 40%, 50%, and 75% of the perimeter of the membrane 26 were produced, and as shown in FIG. 5, the sections of white are visually distinguishable and well-defined relative to the sections of blue.

[0051] FIG. 6 provides a table of color / stripe combinations demonstrating the versatility of the membrane 26 according to the present disclosure. Again, each of the first section 40 and the second section 42 comprised a blend of PP / HDPE at a weight ratio of 85 / 15. In top entry of the table, a white (WH) second section 42 spanning 5% of the perimeter of the membrane 26 is provided within an orange (OR) first section 40. In the second entry of the table, a black (BK) second section 42 spanning 30% of the perimeter of the membrane 26 is provided within an orange (OR) first section 40. In the third entry of the table, a green (GR) second section 42 spanning 5% of the perimeter of the membrane 26 is provided within a green (GR) first section 40. Thus, this membrane 26 is substantially aAttorney Docket No. HI24-111PCT solid color having strip of material to provide access to the interior of the membrane 26. In the fourth entry of the table, a black (BK) second section 42 spanning 30% of the perimeter of the membrane 26 is provided within a green (GR) first section 40. In the fifth entry of the table, a solid brown (BR) membrane is shown for color comparison purposes, and in the bottom entry of the table, a black (BK) second section 42 spanning 30% of the perimeter of the membrane is provided in a brown (BR) first section 40. As compared to the fifth entry having a single brown membrane material (no stripe), the other entries each include stripe of a second material that is continuously bonded to the rest of the membrane. That is, there is no visual indication of cracking or separation at the interface between the first section and second section. Additionally, for the entries with a second section having a different color than the first section, the second section is visually distinguishable with sharp contrast at the interfaces.

[0052] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. In addition, as used herein, the article "a" is intended to include one or more than one component or element, and is not intended to be construed as meaning only one.

[0053] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosed embodiments. Since modifications, combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the embodiments may occur to persons skilled in the art, the disclosed embodiments should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

Attorney Docket No. HI24-111PCTWhat is claimed is:

1. A membrane of an optical fiber subunit, comprising a first section comprising a first polymer composition; at least one second section comprising a second polymer composition; wherein the first polymer composition comprises a first thermoplastic polymer; wherein the second polymer composition comprises a blend of the first thermoplastic polymer and a second thermoplastic polymer that is immiscible with the first thermoplastic polymer; wherein the at least one second section and the first section define an outer perimeter of an outer surface of the membrane; and wherein the at least one second section extends from 5% to 85% around the perimeter.

2. The membrane of claim 1, wherein the first polymer composition comprises only one polymer, the one polymer being the first thermoplastic polymer.

3. The membrane of claim 1, wherein the first polymer composition comprises a blend of polymers comprising the first thermoplastic polymer and at least one other thermoplastic polymer and wherein each of the at least one other thermoplastic polymer is present in an amount less than the first thermoplastic polymer.

4. The membrane of claim 1, wherein the membrane comprises the outer surface and an inner surface and wherein the at least one second section extends through a thickness of the membrane from the outer surface to the inner surface.

5. The membrane of claim 1, wherein the at least one second section extends only partially through a thickness of the membrane.

6. The membrane of claim 1, wherein the first section is a different color from the at least one second section.

7. The membrane of claim 1, wherein the first section is a same color as the at least one second section.Attorney Docket No. HI24-111PCT8. The membrane of claim 1, wherein the at least one second section extends from 20% to 20% around the perimeter.

9. The membrane of claim 1, wherein an average peel strength of the membrane as measured transverse to an extrusion direction of the membrane to separate the at least one second section from the first section is 4 N or less.10 The membrane of claim 1, wherein the first thermoplastic polymer is a polyolefin, polyvinylchloride, polystyrene, acrylonitrile butadiene styrene, styrene-acrylonitrile, styrene-ethylene-butylene-styrene, or a technical thermoplastic.

11. The membrane of claim 1, wherein the second polymer composition comprises from 5% to 80% by weight of the first thermoplastic polymer.

12. The membrane of claim 1, wherein the membrane comprises a thickness between the outer surface and an inner surface, the thickness being in a range of 10 pm to 60 pm.

13. A routable base unit, comprising: a plurality of optical fibers; and the membrane according to claim 1, the membrane surrounding the plurality of optical fibers; wherein the membrane has a thickness of 100 pm or less.

14. An optical fiber cable, comprising: a cable jacket comprising an inner surface and an outer surface, the inner surface defining a central bore extending along a longitudinal axis of the optical fiber cable and the outer surface defining an outermost surface of the optical fiber cable; and a plurality of routable base units (RBU) disposed within the central bore; wherein each RBU of the plurality of RBU comprises: a plurality of optical fibers; and a membrane surrounding the plurality of optical fibers, the membrane having a thickness of 100 pm or less; andAttorney Docket No. HI24-111PCT wherein the membrane comprises at least one stripe of a first polymer composition within a second polymer composition; wherein the at least one stripe of the first polymer composition is configured to peel apart from the second polymer composition at an average peel strength as measured transverse to an extrusion direction of the membrane of 4 N or less.

15. The optical fiber cable of claim 14, wherein the at least one stripe of the first polymer composition is differently colored than the second polymer composition.

16. The optical fiber cable of claim 14, wherein the at least one stripe of the first polymer composition has a same color as the second polymer composition.

17. The optical fiber cable of claim 14, wherein the first polymer composition comprises a first thermoplastic polymer; and wherein the second polymer composition comprises a blend of the first thermoplastic polymer and a second thermoplastic polymer that is immiscible with the first thermoplastic polymer.

18. The optical fiber cable of claim 17, wherein the second polymer composition comprises from 5% to 80% by weight of the first thermoplastic polymer.

19. The optical fiber cable of claim 17, wherein the first polymer composition comprises only one polymer, the one polymer being the first thermoplastic polymer.

20. The optical fiber cable of claim 17, wherein the first polymer composition comprises a blend of polymers comprising the first thermoplastic polymer and at least one other thermoplastic polymer and wherein each of the at least one other thermoplastic polymer is present in an amount less than the first thermoplastic polymer.

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