Dual layer cable jacket for optical fiber cable providing increased bending stiffness and accessibility

Abstract

Provided are embodiments of an optical fiber cable. The optical fiber cable includes a cable jacket having an inner surface defining a central bore and an outer surface. A cable core including at least one optical fiber is disposed within the central bore. The cable jacket has an inner layer and an outer layer in which the inner layer extends from the inner surface to an interface between the inner layer and the outer layer and in which the outer layer extends from the outer surface to the interface. The outer layer is formed from a first polymer composition including a first polymer having a first flexural modulus, and the inner layer is formed from a second polymer composition including a second polymer having a second flexural modulus. The second flexural modulus is at least 1.5x greater than the first flexural modulus.

Description

Attorney Docket No.: HI24-123PCTDUAL LAYER CABLE JACKET FOR OPTICAL FIBER CABLE PROVIDING INCREASED BENDING STIFFNESS AND ACCESSIBILITYCROSS-REFERENCE TO RELATED APPLICATION

[0001] The application claims the benefit of priority of U.S. Patent Application No. 63 / 722,742, filed on November 20, 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 an optical fiber cable having a dual layer jacket that provides increased bending stiffness and accessibility.

[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. Further, the optical fiber cable should possess certain minimum mechanical standards to facility blowing or jetting the cable into such ducts.SUMMARY OF THE DISCLOSURE

[0004] In a first 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 cable core comprising at least one optical fiber is disposed within the central bore. The cable jacket comprises an inner layer and an outer layer in which the inner layer extends from the inner surface to an interface between the inner layer and the outer layer and in which the outer layer extends from the outer surface to the interface. The outer layerAttorney Docket No.: HI24-123PCT comprises a first polymer composition comprising a first polymer having a first flexural modulus, and the inner layer comprsises a second polymer composition comprising a second polymer having a second flexural modulus. The second flexural modulus is at least 1.5x greater than the first flexural modulus.

[0005] In a second aspect, embodiments of the present disclosure relate to a method of manufacturing an optical fiber cable. In the method, a cable jacket is co-extruded around a cable core. The cable core comprises at least one optical fiber, and the cable jacket comprises an inner layer and an outer layer. The outer layer comprises a first polymer composition comprising a first polymer having a first flexural modulus, and the inner layer comprises a second polymer composition comprising a second polymer having a second flexural modulus. The second flexural modulus is at least 1.5x greater than the first flexural modulus.

[0006] 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.

[0007] 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

[0008] 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:

[0009] FIG. 1 depicts a cross-sectional view of a high fiber density optical fiber cable having a dual layer jacket, according to exemplary embodiments;

[0010] FIG. 2 is a photograph of an optical fiber cable with a dual layer jacket constructed according to an embodiment of the present disclosure;

[0011] FIG. 3 is a photograph of the dual layer jacket of FIG. 2 being peeled from a cable core, according to an exemplary embodiment;Attorney Docket No.: HI24-123PCT

[0012] FIG. 4 is an arrangement for impact testing of the dual layer jacket, according to an exemplary embodiment; and

[0013] FIG. 5 is an arrangement for measuring compression resistance of the dual layer jacket, according to an exemplary embodiment.DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure relate to an optical fiber having a dual layer jacket comprising an inner layer of a high modulus material to increase the bending stiffness of the optical fiber cable. As will be discussed more fully below, certain high-density cable designs have sought to eliminate certain cable components, such as strength members, to provide more room in the cable core for optical fibers. However, the elimination of such components decreases the bending stiffness of the optical fiber cable, hampering the ability of the cable to be jetted into ducts. According to the present disclosure, the dual layer jacket for the optical fiber cable allows for the stiffness of the optical fiber cable to be increased while still avoiding the use of strength members. Additionally, the inner layer of the dual layer jacket is comprised of a blend of polymers that phase separate into elongated domains during extrusion, providing tear paths for accessing the cable core of the optical fiber cable. These and other aspects and advantages of the disclosed optical fiber cable with dual layer jacket 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.

[0015] 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 coreAttorney Docket No.: HI24-123PCT

[0016] 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 waterblocking yam.

[0017] 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.

[0018] 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 one or more ripcords. In one or more embodiments, armor layers and strength elements, such as fiber reinforced plastic rods, are excluded from the construction of the optical fiber cable 10.

[0019] 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.Attorney Docket No.: HI24-123PCT

[0020] 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.

[0021] 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 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.

[0022] 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.

[0023] 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 up 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.Attorney Docket No.: HI24-123PCT

[0024] 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).

[0025] According to embodiments of the present disclosure, the jacket 12 includes an outer layer 30 and an inner layer 32. The outer layer 30 is comprised of a first polymer composition, and the inner layer 32 is comprised of a second polymer composition.

[0026] In one or more embodiments, the first polymer composition of the outer layer 30 comprises a first polymer. In one or more embodiments, the first polymer has a flexural modulus in a range from about 0.5 GPa to about 2 GPa, in particular in a range from about 0.7 GPa to about 1.5 MPa. In one or more embodiments, the first polymer is a polyolefin, such as polyethylene (PE) (e.g., high, medium, or low density) or polypropylene (PP) (including impact grade), or a polyamide (PA), such as polyamide 12 (PA12), amongst other possibilities. For example, medium and high density PE have a flexural modulus in a range of about 0.7 GPa to about 1 GPa; PP copolymer has a flexural modulus in a range of about 1 GPa to about 1.4 GPa; PP homopolymer has a flexural modulus in a range of about 1.2 GPa to about 1.5 GPa; and impact grade PP has a flexural modulus in a range from about 0.6 to about 1 GPa.

[0027] In one or more embodiments, the second polymer composition of the inner layer 32 comprises at least one second polymer having a higher flexural modulus than the first polymer, such as a second polymer having a flexural modulus in a range from about 2 GPa to about 5 GPa, in particular in a range from about 2.2 GPa to about 3.5 GPa. In one or more embodiments, the flexural modulus of the second polymer is at least 1.5x, in particular 2x, and more particularly 3x, greater than the flexural modulus of the first polymer. In one or more embodiments, the second polymer comprises at least one of polystyrene (PS), polycarbonate (PC), polybutylene terephthalate (PBT), polyphenylene ether (PPE), or polyoxymethylene (POM), amongst other possibilities. For example, PS has a flexural modulus in a range of about 3 GPa to about 3.5 GPa, and PC has a flexural modulus in a range of about 2.2 GPa to about 2.5 GPa. While there may be many polymers that have a suitable flexural modulus to be the second polymer, such as various engineering thermoplastics and high performance plastics, the second polymer is preferably a commodity plastic, such as polystyrene, to avoid a substantial increase in the cost of the cable jacket 12.Attorney Docket No.: HI24-123PCT

[0028] The second polymer composition comprises not only the at least one second polymer but also, in one or more embodiments, a third polymer. In such embodiments, the third polymer is the same as the first polymer or is another similar polymer, such as another polyolefin. In one or more embodiments, the third polymer comprises PE (e.g., high, medium, or low density), PP (including impact grade), or PA (e.g., PA12), amongst other possibilities. In one or more embodiments, the third polymer is immiscible or only partially miscible with the second polymer.

[0029] Further, in one or more embodiments, the second polymer composition includes a compatibilizer, such as a polymer containing monomers of the first polymer and the second polymer. The compatibilizer may be used to improve adhesion between the outer layer 30 and the inner layer 32 so as to prevent separation of the layers. In one or more embodiments, the compatibilizer comprises at least one of styrene-ethylene-butylene- styrene (SEBS), styrene-butylene-styrene (SBS); styrene-acrylate-styrene (SAS), or styrene-acrylonitrile (SAN), amongst other possibilities.

[0030] According to one example, the first polymer composition comprises PE as the first polymer, and the second polymer composition comprises PS as the second polymer, PP as the third polymer, and SEBS as the compatibilizer.

[0031] In one or more embodiments, the first polymer composition includes only the first polymer as the polymer component of the composition. The first polymer composition may include other processing and performance additives, such as UV stabilizers, colorants, fillers, flame retardants, plasticizers, and antioxidants, for example. In one or more embodiments, the first polymer composition comprises up to 6 wt% of such additives with the balance of the first polymer composition being the first polymer.

[0032] In one or more embodiments, the second polymer composition comprises the at least one second polymer in an amount in a range from 40 wt% to 95 wt%, in particular in a range from 60 wt% to 90 wt%. In one or more embodiments, the second polymer composition comprises the third polymer in an amount in a range from 5 wt% to 60 wt%, in particular in a range from 10 wt% to 40 wt%. In one or more embodiments, the second polymer composition comprises the compatibilizer in an amount in a range from 3 wt% to 20 wt%, in particular in a range from 5 wt% to 10 wt%.

[0033] As with the first polymer composition, the second polymer composition may include other processing and performance additives, such as colorants, fillers, flameAttorney Docket No.: HI24-123PCT retardants, plasticizers, and antioxidants, for example. In one or more embodiments, the second polymer composition comprises up to 6 wt% of such additives with the balance of the second polymer composition being the second polymer, the third polymer, and the compatibilizer. In one or more embodiments, the second polymer composition comprises, in particular, a fiber filler material, such as glass fiber, to further enhance the mechanical properties of the inner layer 32.

[0034] In one or more embodiments, the jacket 12 comprises a total thickness TT of up to 3 mm, in particular in a range of 0.3 mm to 2.0 mm, and most particularly in a range of 0.4 mm to 0.8 mm, as measured between the inner surface 14 and the outer surface 16. In one or more embodiments, the jacket 12 comprises an interface 34 between the outer layer 30 and the inner layer 32. In one or more embodiments, the outer layer 30 comprises a first thickness Ti as measured between the outer surface 16 and the interface 34, and the inner layer 32 comprises a second thickness T2 as measured between the inner surface 14 and the interface 34. The first thickness Ti and the second thickness T2 together equal the total thickness TT (i.e., Ti + T2 = TT). In one or more embodiments, the second thickness T2 is greater than or equal to the first thickness Ti. In one or more embodiments, the second thickness T2 comprises from 50% to 90% of the total thickness TT, in particular from 70% to 90% of the total thickness TT.

[0035] As mentioned above, the inner layer 32 is formed from a polymer having a higher flexural modulus than the polymer of the outer layer 30. For cable jetting applications, the inner layer 32 increases the bending stiffness of the optical fiber cable 10, which improves the achievable jetting distance. In particular, embodiments of the optical fiber cable 10 do not include strength members, such as fiber-reinforced plastic rods or metal wires. Such strength members increase the stiffness of a cable construction, and elimination of those components reduces the cable stiffness, thereby also reducing the achievable jetting distance.

[0036] In this regard, Applicant tested several conventional cable designs according to IEC 60794-1-124 EDI Part 1-124: Generic specification - Basic optical cable test procedures - Mechanical test methods - Installation test for microduct cabling Method B (1645 m), and Applicant found that the achievable jetting distance directly relates to the bending stiffness of the optical fiber cable. For example, a cable having a bending stiffness of 8772 N / mm2was able to be jetted more than 1500 m, whereas a cable having a bending stiffness of 3327 N / mm2was only able to be jetted about 560 m.Attorney Docket No.: HI24-123PCT

[0037] In the optical fiber cable 10 according to the present disclosure, the increased bending stiffness provided by the inner layer 32 formed of a polymer having a higher flexural modulus than the polymer forming the outer layer 30 improves the jetting performance of the optical fiber cable 10. In one or more embodiments, the optical fiber cable 10 is able to be jetted a distance of at least 800 m, in particular at least 1000 m, when tested according to IEC 60794-1-124 EDI Part 1-124. Further, the level of increase in bending stiffness can be customized by varying the relative thicknesses of the inner layer 32 to the outer layer 30, by selecting the second polymer to have a greater flexural modulus, and / or by increasing the amount of second polymer in the inner layer 32.

[0038] By using the dual layer construction of the jacket 12, the layers 30, 32 are able to provide other desirable characteristics. In particular, the outer layer 30 may be selected to provide desired environmental resistance (e.g., UV and weather resistance) and low surface friction, enhancing cable jetting performance. Additionally, the combination of the second polymer and the third polymer in the inner layer 32 allows for peelability of the jacket 12 to provide access to the cable core 20. In particular, the immiscibility or partially miscibility of the third polymer and the second polymer creates elongated domains of the third polymer in the second polymer, creating phase separation interfaces between the elongated domains that act as tear paths when separating the cable jacket 12. If the outer layer 30 is sufficiently thin such that tearing of the cable jacket 12 amounts substantially to tearing the inner layer 32, the cable jacket 12 can easily be split and peeled apart by hand without requiring any special tooling. Advantageously, the cable jacket 12 can be split at any location around the circumference. Certain conventional cable jackets can only be split at specific locations of embedded access features, which are generally identified by tactile locator features (e.g., one or more ridges or grooves formed over or near the access feature). Because the cable jacket 12 can be split at any location around the circumference, such tactile locator features do not need to be formed in the cable jacket 12. Further, in one or more embodiments, the cable core 20 may include one or more ripcords 36, such as aramid strands, to facilitate tearing of the binder 28 along with the cable jacket 12.

[0039] In one or more embodiments, the cable jacket 12 can be fabricated by co-extruding the inner layer 32 and outer layer 30 around the cable core 20. Advantageously, co-extrusion does not require significant modification to a cable jacket processing line, and the components of the second polymer composition can be pre-compounded or dry blended for use in the co-extrusion process.Attorney Docket No.: HI24-123PCT

[0040] EXPERIMENTAL EXAMPLES

[0041] FIG. 2 is a photograph of an example optical fiber cable 10 prepared according to the present disclosure. As can be seen in FIG. 2, the optical fiber cable 10 includes the dual layer cable jacket 12 with the inner layer 32 and outer layer 30 around a cable core 20 having 144 optical fibers 24 in twelve RBUs 22. The outer layer 30 was high-density polyethylene (HDPE), and the inner layer 32 was a blend of HDPE and polystyrene (PS). The outer layer 30 included a black colorant, and the inner layer 32 did not include a colorant so that the layers could be distinguished. Within the inner layer, domains of the second polymer (PS) and the third polymer (HDPE) can be discerned. As discussed above, such phase separation of the second PS and HDPE creates elongated domains during extrusion that provide a tear path for the splitting and peeling of the cable jacket 12 from around the cable core. In that regard, FIG. 3 depicts the exposed cable core 20 and split jacket 12 for the cable shown in FIG. 2. After notching the jacket 12 to provide a tearing point, the cable jacket 12 was able to be split and peeled apart by hand.

[0042] Two optical fiber cables were prepared and subjected to impact testing according to IEC 60794-1 -2 -E4. The first cable had the dual layer construction as described above in relation to FIGS. 2 and 3 (HDPE outer layer 30, HDPE / PS inner layer 32), and the second cable included an outer layer 30 of HDPE and an inner layer 32 of HDPE, PS, and SEBS compatibilizer.

[0043] FIG. 4 depicts the arrangement 100 for impact testing. As can be seen, the testing arrangement 100 includes a base 102 upon which a cable sample 104 is positioned. A weight 106 is contained in a guide channel 108 over the sample 104. Disposed on the bottom of the weight 106 is a striking face 110 that is configured to contact the cable sample 104. The weight 106 is lifted by a cable 112 that is threaded over a free running pulley 114.

[0044] During testing, the cable 112 is pulled over the pulley to lift the weight 106 to a desired height within the guide channel 108. For the presently discussed testing, the weight 106 was 1200g, and the drop height was 31 cm. Testing was performed at room temperature and at -20 °C.

[0045] When tested, the first cable exhibited cracking during the room temperature test and failed during the low temperature test. For the second cable including the compatibilizer, the cable passed both the room temperature and low temperature impact testing. Thus, the use ofAttorney Docket No.: HI24-123PCT a compatibilizer in the second polymer composition of the inner layer 32 provides enhanced mechanical performance, especially with respect to impact forces.

[0046] Four additional cable samples were prepared and tested on a jetting track according to IEC 60794-1-124 EDI Part 1-124. Table 1, below, provides a summary of the cable jacket construction as well as the jetting performance.Table 1. Jetting Performance based on Cable Jacket Construction

[0047] As can be seen from Table 1, the first sample was a control sample in which the optical fiber cable included a conventional single layer of HDPE, and the outer diameter of the cable was 4.6 mm. The first sample was able to be jetted a distance of 556 m. The second sample included the dual layer jacket as discussed herein. The outer layer was HDPE, and the inner layer was a blend of polystyrene (PS), polyethylene (PE), and styrene- ethylene-butylene-styrene (SEBS). The second sample had the same outer diameter as the first sample of 4.6 mm. However, the stiffer cable jacket resulted in an increase in jetting distance by almost 300 m to 836 m.

[0048] The third sample also had a dual layer construction, but the PE in the inner layer was replaced with polypropylene (PP). Further, outer diameter of the cable was decreased from 4.6 mm to 4.52 mm by reducing the thickness of the cable jacket. Notwithstanding the decrease in jacket thickness, the third sample was able to be jetted even further than the second sample as a result of replacing the PE with PP. A fourth sample was prepared and had the same dual layer construction as the third sample, but the outer diameter of the cable was increased to 4.75 mm by increasing the thickness of the cable jacket. As can be seen Table 1, the increased thickness of the cable jacket provided a substantial increase in the jetting distance up to 1100 m. Thus, according to the present disclosure, the cable jacket can be customized to increase the jetting distance for a cable having the same or even a smallerAttorney Docket No.: HI24-123PCT outer diameter, or the jetting distance can be substantially increased with only a modest increase in jacket thickness.

[0049] Finally, three cable samples were subjected to radial compression force testing. FIG. 5 depicts the arrangement 200 for this testing. A sample cable 202 is positioned on a base surface 204 and compressed with a cylindrical pin 206. For the testing performed, the cylindrical pin 206 had a face diameter of 20 mm. The sample cable 202 was arranged so that the length of the sample cable 202 was compressed between the base surface 204 and the cylindrical pin 206. For the test, the sample was compressed to specific levels of deformation, namely 20% and 35% deformation. The average force to reach these deformation levels was registered. A cable jacket requiring a higher force to reach the specific level of deformation corresponds to an increased ability of the jacket to resist compressive loads that might occur during the cable installation. Accordingly, a higher average force is associated with better cable jetting performance.

[0050] Table 2, below, summarizes the average force to compress to 20% and 35% compression and the achievable jetting distance. The first sample had a single layer jacket comprised of HDPE. The second sample had an outer layer comprised of HDPE and an inner layer comprised of PE, PS, and SEBS. The third sample had an outer layer comprised of HDPE and an inner layer comprised of PP, PS, and SEBS. Each of the samples had an outer diameter of 4.6 mm.Table 2. Compression and Jetting Performance based on Cable Jacket Construction

[0051] From Table 2, it can be seen that the sample 1, which had an HDPE single layer jacket, had the lowest average force required to achieve the 20% and 35% compression deformation as well as the lowest jetting distance. The second sample having the inner layer of PE / PS / SEBS improved in both the average force to achieve 20% and 35% compression deformation as well as an increased jetting distance. The third sample increased in both average force to achieve 20% and 35% compression and jetting distance. In particular, asAttorney Docket No.: HI24-123PCT compared to the first sample, the average force to achieve 20% compression increased by 10 N, and the average force to achieve 35% compression increased by 62 N. Further, the achievable jetting distance almost doubled from 560 m to 1100 m.

[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.: HI24-123PCTWhat is claimed is:

1. 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; a cable core comprising at least one optical fiber disposed within the central bore; wherein the cable jacket comprises an inner layer and an outer layer, the inner layer extending from the inner surface to an interface between the inner layer and the outer layer and the outer layer extending from the outer surface to the interface; wherein the outer layer comprises a first polymer composition comprising a first polymer having a first flexural modulus; and wherein the inner layer comprises a second polymer composition comprising a second polymer having a second flexural modulus, the second flexural modulus being at least 1 ,5x greater than the first flexural modulus.

2. The optical fiber cable of claim 1, wherein the second polymer composition further comprises a third polymer and a compatibilizer, the compatibilizer being a polymer having monomers of the first polymer and of the second polymer.

3. The optical fiber cable of claim 2, wherein the third polymer is the same as the first polymer.

4. The optical fiber cable of claim 2, wherein the first polymer is a polyolefin and the third polymer is a polyolefin different from the polyolefin of the first polymer.

5. The optical fiber cable of claim 2, wherein the second polymer composition comprises the second polymer in an amount in a range from 40 wt% to 95 wt%, the third polymer in an amount in a range from 5 wt% to 60 wt%, and the compatibilizer in an amount in a range from 3 wt% to 20 wt%.

6. The optical fiber cable of claim 1, wherein the outer layer comprises a first thickness as measured between the outer surface and the interface and the inner layer comprises a second thickness between the interface and the inner surface, the first thickness and theAttorney Docket No.: HI24-123PCT second thickness together equaling a total thickness of the cable jacket and the second thickness being greater than or equal to the first thickness.

7. The optical fiber cable of claim 6, wherein the second thickness is from 50% to 90% of the total thickness.

8. The optical fiber cable of claim 1, wherein the first polymer comprises a polyethylene, a polypropylene, or a polyamide.

9. The optical fiber cable of claim 8, wherein the second polymer comprises a polystyrene, a polycarbonate, a polybutylene terephthalate, a polyphenylene ether, or a polyoxymethylene.

10. The optical fiber cable of claim 1, wherein the optical fiber cable does not comprise any fiber reinforced strength members or metal wires.

11. The optical fiber cable of claim 1, wherein the outer surface of the cable jacket does not define any tactile locator features to identify a location of an access feature.

12. The optical fiber cable of claim 1, configured to be jetted a distance of at least 800 m when tested according to IEC 60794-1-124 EDI Part 1-124.

13. A method of manufacturing an optical fiber cable, comprising: co-extruding a cable jacket around a cable core, the cable core comprising at least one optical fiber and the cable jacket comprising an inner layer and an outer layer; wherein the outer layer comprises a first polymer composition comprising a first polymer having a first flexural modulus; and wherein the inner layer comprises a second polymer composition comprising a second polymer having a second flexural modulus, the second flexural modulus being at least 1 ,5x greater than the first flexural modulus.

14. The method of claim 13, wherein the second polymer composition further comprises a third polymer and a compatibilizer, the compatibilizer being a polymer having monomers of the first polymer and of the second polymer.Attorney Docket No.: HI24-123PCT15. The method of claim 14, wherein the first polymer comprises a polyethylene, a polypropylene, or a polyamide.

16. The method of claim 15, wherein the second polymer comprises a polystyrene, a polycarbonate, a polybutylene terephthalate, a polyphenylene ether, or a polyoxymethylene.

17. The method of claim 16, wherein the compatibilizer comprises a styrene-ethylene- butylene-styrene, a styrene-butylene-styrene, a styrene-acrylate-styrene, or a styreneacrylonitrile.

18. The method of claim 17, wherein the third polymer comprises a polyethylene, a polypropylene, or a polyamide.

19. The method of claim 18, wherein the first polymer and the third polymer are the same.

20. The method of claim 18, wherein the first polymer and the third polymer are different.

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