The present invention is related to optical fiber cables with subunits and more particularly to optical fiber carrying subunits having jackets with improved mechanical properties. Optical fiber cables are used to transmit data over distance. Generally, large distribution cables that carry a multitude of optical fibers from a hub are sub-divided at network nodes into routable subunits. Described herein are jackets for routable subunits in which the jacket provides adequate flexibility, robustness, and safety features, among other qualities.
In one aspect, embodiments of the disclosure relate to an optical fiber cable including an outer jacket and a plurality of optical fiber carrying subunits. The outer jacket includes an inner surface and an outer surface that is an outermost surface of the optical fiber cable. A central bore extends within the inner surface in a longitudinal direction between first and second ends of the outer jacket. The plurality of optical fiber carrying subunits are located within the central bore, and each of the plurality of optical fiber carrying subunits includes a subunit jacket and a plurality of optical fibers. Each subunit jacket is located within the central bore and includes an inner surface and an outer surface. An inner bore extends within an inner surface of the subunit jacket in a longitudinal direction between first and second ends of the subunit jacket. The subunit jacket includes a first polymer composition including a low smoke, zero halogen material that has a storage modulus of no more than 2000 MPa at −20 (negative twenty) degrees Celsius. The plurality of optical fibers are located within the inner bore and extend in the longitudinal direction between the first and second ends of the subunit jacket.
In another aspect, embodiments of the disclosure relate to an optical fiber cable including an outer jacket and a plurality of optical fiber carrying subunits. The outer jacket includes an inner surface and an outer surface. The outer surface is an outermost surface of the optical fiber cable. A central bore extends within the inner surface in a longitudinal direction between first and second ends of the outer jacket. The plurality of optical fiber carrying subunits are located within the central bore, and each of the plurality of optical fiber carrying subunits includes a subunit jacket and a plurality of optical fibers. Each subunit jacket is located within the central bore. The subunit jacket includes an inner surface and an outer surface. An inner bore extends within an inner surface of the subunit jacket in a longitudinal direction between first and second ends of the subunit jacket. The subunit jacket includes a first polymer composition that includes a low smoke, zero halogen material having an elongation at break coefficient of at least 140%. The plurality of optical fibers are located within the inner bore and extend in the longitudinal direction between the first and second ends of the subunit jacket.
In yet another aspect, embodiments of the disclosure relate to a method of manufacturing an optical fiber cable. The includes unspooling a first optical fiber and extruding a first polymer composition around the first optical fiber to form a first subunit jacket. The first subunit jacket includes an inner surface and an outer surface. An inner bore extends within the inner surface in a longitudinal direction between first and second ends of the first subunit jacket. The first polymer composition includes a low smoke, zero halogen material. During extrusion, the first polymer composition of the first subunit jacket includes a drawdown ratio no more than 4. The method also includes unspooling a second optical fiber and extruding the first polymer composition around the second optical fiber to form a second subunit jacket. The second subunit jacket includes an inner surface and an outer surface. An inner bore extends within the inner surface in a longitudinal direction between first and second ends of the second subunit jacket. During extrusion, the first polymer composition of the second subunit jacket comprises a drawdown ratio no more than 4. The method also includes extruding a second polymer composition around the first subunit jacket and the second subunit jacket to form an outer jacket. The outer jacket includes an outer surface that is an outermost surface of the optical fiber cable
Additional features and advantages will be set forth in the detailed description that follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings.
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 understand the nature and character of the claims.
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 embodiment(s), and together with the description serve to explain principles and the operation of the various embodiments.
The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.
Referring generally to the figures, various embodiments of an optical fiber cable including subunits are shown. The subunit jackets discussed herein are formed from materials that provide a unique and difficult to achieve set of properties including, high burn resistance, low smoke production, flexibility, improved manufacturability and/or low thickness, that Applicant believes is not previously achieved in optical fiber subunit designs. Computer data center operators require increasingly high fiber density optical cables in order to meet their capacity needs while not overcrowding the trays used to run cables throughout the data center. To address this issue, Applicant has developed cables that use routable subunits. However, Applicant has found it difficult to obtain subunits with jackets that tolerate a high draw and thin wall manufacturing process, adhere to certain safety regulations (e.g., fire safety regulations), are sufficiently flexible, and do not exhibit unacceptable signal attenuation. Applicant has developed a variety of optical fiber cables with subunit jackets that are robust over a wide range of temperatures, flexible enough at room temperature to serve as a furcation leg, and can be used as a component in large stranded cables such as the 6912 IO cable without negatively impacting signal attenuation, all while achieving burn performance to satisfy various safety regulations.
The subunit jackets described herein provide several advantages over previous subunits. By eliminating the need to furcate the ribbons, workers installing the cables will be able to save significant time and labor. The improved flexibility at room temperatures, and colder, also reduces the likelihood of subunit jackets cracking when routing the subunits into an enclosure or splice cabinet in the field, and the adherence to safety regulations is requiring Applicant to use materials that are not typically used for as subunit jackets. The embodiments described herein allow for a wide range of installation and operation temperatures and reduce the likelihood of failures by allowing for the subunits and the ribbons within them to more easily move to low stress positions.
Disposed within the central bore 18 are a plurality of subunits 20. In various embodiments, the subunits 20 are helically wound (e.g., wound around each other, wound around one or more central strength element), which facilitates bending and coiling of the ribbon cable 10, e.g., enhancing the routability of the ribbon cable 10.
Referring to
The cable jacket 12 includes a plurality of strengthening members, shown as strengthening yarns 38, contained within the material of the cable jacket 12 between the inner surface 14 and the outer surface 16. In an embodiment, the ribbon cable 10 includes four strengthening yarns 38 disposed within the cable jacket 12 in two pairs that are equidistantly spaced around the cable jacket 12. In embodiments, the strengthening yarns 38 are textile yarns. Exemplary textile yarns suitable for use as the strengthening yarns include at least one of glass fibers, aramid fibers, cotton fibers, or carbon fibers, among others.
In various embodiments, jacket 12 is formed from a polymer material and in specific embodiments is formed from a polyolefin material. Exemplary polyolefins suitable for use in the jacket 12 include one or more of medium-density polyethylene (MDPE), high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and/or polypropylene (PP), amongst others. Exemplary thermoplastic elastomers suitable for use in the jacket 12 include one or more of ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), ethylene-octene (EO), ethylene-hexene (EH), ethylene-butene (EB), ethylene-vinyl acetate (EVA), and/or styrene-ethylene-butadiene-styrene (SEBS), amongst others.
In various embodiments, the cable jacket 12 includes an access feature 40, such as a ripcord or strip of polymer material that is dissimilar from the material of the cable jacket 12 (e.g., polypropylene strip in a predominantly polyethylene jacket). In embodiments, the ripcord is a yarn that includes at least one of a textile fiber (such as those listed above), liquid crystal polymer fibers, or PET polyester fibers, among others. In one embodiment, the ribbon cable 10 includes two access features 40 that are arranged diametrically within the cable jacket 12. In other embodiments, the ribbon cable 10 may include a single access feature 40 or more than two access features 40, such as up to four access features 40. The access features 40 may be positioned such that strengthening yarns 38 are evenly spaced around the access feature 40.
In the embodiment depicted in
In various embodiments, jacket 26 includes a first polymer composition comprising a low smoke, zero halogen (LSZH) material. In a specific embodiment, the first polymer composition that forms jacket 26 has a storage modulus of no more than 500 MPa at room temperature (e.g., about 20° C.) and no more than 4000 MPa at −20 (negative twenty) ° C., or more specifically no more than 200 MPa at room temperature and no more than 2000 MPa at −20 (negative twenty) ° C. In one embodiment, subunit jacket has a thickness between 0.15 mm and 0.45 mm, and more specifically between 0.2 mm and 0.35 mm. Applicant has determined that most low smoke, zero halogen materials that are too brittle and inflexible to provide easy to use, routable subunits. However, Applicant has identified LSZH materials with these storage modulus ranges and/or thickness ranges, allows for use of LSZH materials while still providing for a routable subunit that is resistant to cracking.
In embodiments, the subunit jacket 26 comprises a low smoke, zero halogen (LSZH) and/or flame retardant, non-corrosive (FRNC) composition. In certain embodiments, the subunit jacket 26 is comprised of a flame retardant additive dispersed, mixed, or otherwise distributed in a polymeric resin. In embodiments, the polymeric resin is a thermoplastic, and in a more specific embodiment, the thermoplastic is a polyolefin-based resin. Polymer resins that may be used for the subunit jacket 26 include a single polymer or a blend of polymers selected from the following non-limiting list: ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers, ethylene homopolymers (including but not limited to low density, medium density, and high density), linear low density polyethylene, very low density polyethylene, polyolefin elastomer copolymer, propylene homopolymer, polyethylene-polypropylene copolymer, butene- and octene branched copolymers, polyester copolymers, polyethylene terephthalates, polybutylene therephthalates, other polymeric terephthalates, and maleic anhydride-grafted versions of the polymers listed herein. In embodiments, the subunit jacket 26 includes at least one flame retardant additive. Exemplary flame retardant additives include aluminum trihydrate (ATH), magnesium hydroxide (MDH), ammonium polyphosphate (APP), pentaerythritol (PER), antimony oxides, zinc borates, boehmite, intumescent materials, and red phosphorous, among others.
In various embodiments, the subunit jacket 26 is formed from a first polymer material, and jacket 12 of cable 10 is formed from a different material. In one such embodiment, subunit jacket 26 is formed from a first LSZH halogen material, and jacket 12 is formed from a different LSZH halogen material.
In a specific embodiment, subunit jacket 26 has a limiting oxygen index (LOI) of 25 or greater (as measured according to ASTM D 2863 A) and/or a Peak Heat Release Rate (PHRR) of 300 kW/m2 or less. In a more specific embodiment, subunit jacket 26 has an LOI of 30 or more and/or a PHRR of 250 kW/m2 or less.
Referring to
Referring to
Referring to
Referring to Table 1 below, a table demonstrating the effect of the level of air pressure within a subunit jacket on signal attenuation is shown.
As shown in Table 1, Applicant has observed that creating a vacuum or increasing pressure between the subunit jacket and the optical fibers while forming the subunit jacket may negatively affect the signal attenuation of the subunit. As indicated in
Referring to
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.
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.
This application is a continuation application of International Application Number PCT/US2021/041517 filed on Jul. 14, 2021, which claims priority to U.S. Provisional Application Ser. No. 63/054,861 filed on Jul. 22, 2020, the content of each of which is relied upon and incorporated herein by reference in their entirety.
Number | Date | Country | |
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63054861 | Jul 2020 | US |
Number | Date | Country | |
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Parent | PCT/US21/41517 | Jul 2021 | US |
Child | 18098957 | US |