AU2011100839A4 - A flexible stranded optical fiber cable - Google Patents

Abstract

A FLEXIBLE STRANDED OPTICAL FIBER CABLE Described herein is a flexible stranded optical fiber cable for use in the field of s communications. The cable including a cable core and an outer sheath (4) surrounding the cable core. The cable core includes a central strength member (2) and one or more communication units (1) arranged in a stranded configuration surrounding the central strength member. The central strength member (2) is flexible. (FIG. 1)

Description

- 1 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR AN INNOVATION PATENT ORIGINAL Name of Applicants: Yangtze Optical Fibre and Cable Company Ltd. Actual Inventors: Feng Chen and Zhuang Xiong and Dingfang Xu and Zhongping Luo and Zheng Xu Address for Service is: SHELSTON IP 60 Margaret Street Telephone No: (02) 9777 1111 SYDNEY NSW 2000 Facsimile No. (02) 9241 4666 CCN: 3710000352 Attorney Code: SW Invention Title: A FLEXIBLE STRANDED OPTICAL FIBER CABLE The following statement is a full description of this invention, including the best method of performing it known to us: File: 70542AUP00 2 A FLEXIBLE STRANDED OPTICAL FIBER CABLE FIELD OF THE INVENTION [0001] The present invention relates to optical cables and in particular to a flexible stranded optical fiber cable used in the field of communications. [0002] While some embodiments described herein have particular reference to that application, it will be appreciated that the invention is not limited to such a field of use, and is applicable in broader contexts. BACKGROUND [0003] Any discussion of the background art throughout the specification should in no way be considered as an admission that such art is widely known or forms part of common general knowledge in the field. [0004] In the field of optical communication transmission, optical fiber cables are widely used to protect and bundle optical fibers. A known type of optical fiber cable includes a number of optical fibers or optical fiber bundles circumferentially stranded or threaded within the cable. Such cables are generally referred to as stranded optical fiber cables. Existing stranded optical fiber cables primarily consists of a central strength member, a number of stranded communication units, each including a number of optical fibers, and an outer sheath that covers the cable core. The central strength member is generally formed of a rigid material such as steel wire, fiberglass reinforced plastic rods or aramid fiber reinforced rods etc. [0005] For directly buried optical cables, the surrounding environment can change quickly after deployment. For example, the excavated pit can be subject to subsidence and/or uplifting. Such motion of the environment can result in bending of the optical cables, thereby forcing the rigid central strength member to exert lateral pressure onto the communication units in the cable. This, in turn, can result in shears, folds or fractures in the optical fibers. If the exerted pressure is sufficiently great, the communication unit will ultimately break, requiring an expensive process of excavation and cable repairs.

3 [0006] To reduce the occurrence of the above-described problem, steel wires can be wound in the outer sheath of the cable for extra strength. However, the use of steel wire is unsuitable in areas where lightning strikes are common, or in other areas where metal elements cannot be used, such as in or near bodies of water. SUMMARY OF THE INVENTION [0007] It is an object of the present invention, in at least a preferred embodiment, to solve the above-mentioned problem by providing a flexible stranded optical fiber cable, which has high strength and flexibility and is suitable for use in lightning prone areas and other areas generally unsuitable for metals. [0008] It is also an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. [0009] To address the above problem, according to one aspect of the present invention there is provided a flexible stranded optical fiber cable for use in the field of communications, including a cable core and an outer sheath surrounding said cable core, said cable core including: a central strength member; and one or more communication units arranged in a stranded configuration within said core about said central strength member; wherein said central strength member is a flexible central strength member. [0010] The flexible central strength member is preferably made of chemical fiber yam or chemical fiber rope. The chemical fiber yarn or chemical fiber rope is preferably surrounded by a coating layer. [0011] The one or more communication units preferably include a loose tube and an optical fiber unit located within said loose tube, said optical fiber unit preferably including one or more optical fibers, optical fiber bundles, optical fiber ribbons or tight buffered fibers, or combinations thereof. [0012] Further, the optical fiber cable preferably includes a filling unit stranded together with the communication units. The optical fiber cable preferably includes a waterproof material filled in the space between the stranded communication units and 4 the space between the communication units and the outer sheath. The waterproof material can be one or more oily substances, waterproof powder, waterproof yams, water proof rope and waterproof tapes, or combinations thereof. [0013] Preferably, a layer of chemical fiber yarn, chemical ribbon or chemical fiber rope is placed between the outer sheath and the cable core. [0014] The optical fiber cable preferably includes a protective sheath which surrounds the outer sheath and a layer of chemical fiber yarn, chemical fiber ribbon or chemical fiber rope is placed between the protective sheath and the outer sheath. [0015] The chemical fiber yarn, chemical fiber ribbon or chemical fiber rope is preferably made of or woven with aramid yam, fiberglass yarn, polyester yarn, PE fiber yarn or other chemical fibre yarn. [0016] Reference throughout this specification to "one embodiment", "some embodiments" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment", "in some embodiments" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. [0017] As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third", etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. [0018] In the claims below and the description herein, any one of the terms comprising, comprised of or which comprises is an open term that means including at least the elements/features that follow, but not excluding others. Thus, the term comprising, when used in the claims, should not be interpreted as being limitative to the means or elements or steps listed thereafter. For example, the scope of the expression a device comprising A and B should not be limited to devices consisting 5 only of elements A and B. Any one of the terms including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising. BRIEF DESCRIPTION OF THE DRAWINGS [0019] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIG. I is a radial cross-section of a flexible stranded optical fiber cable according to a first embodiment of the present invention; FIG. 2 is a radial cross-section of a flexible stranded optical fiber cable according to a second embodiment of the present invention; and FIG. 3 is a radial cross-section of the flexible central strength member of the present invention. DETAILED DESCRIPTION [0020] Described herein is a flexible stranded optical fiber cable for use in the field of communications. Referring initially to Figs I and 3, there is illustrated a first embodiment optical fiber cable including a cable core and an outer sheath 4 surrounding the cable core. As shown in Fig. 1, the cable core includes a flexible central strength member 2 and a plurality of communication units 1 arranged in a stranded configuration surrounding the central strength member. Each communication unit 1 includes a loose tube enclosing an optical fiber unit. Each optical fiber unit includes one or more individual optical fibers, optical fiber bundles, optical fiber ribbons or tight buffered fibers. Each loose tube loosely covers a corresponding optical fiber unit to protect the unit and allow movement of the unit relative to the tube. [0021] Referring specifically to Fig. 3, the flexible central strength member 2 includes a central region 8 formed of aramid yarn or aramid rope and a protective coating layer 9.

6 [0022] Depending upon the practical situation, it is possible to add a filling unit 6 stranded together with the communication units within the core of the cable, as shown in Fig. 1. [0023] The specific stranded arrangement of communication units within the core of the cable defines spaces between the communication units and between the outer sheath and communication units, as shown in Fig. 1. This space can be filled with waterproof compound or waterproof yarn to protect the communication units from water damage. The waterproof material can be one or more of a filling compound, oily substance, waterproof powder, waterproof yam, water proof rope and waterproof tape. [0024] A layer 3 of aramid yarn, aramid ribbon or aramid rope is disposed between the outer sheath 4 and the cable core to enhance the tensile strength of the cable. The chemical fiber rope and ribbon is preferably formed by weaving of the fiber yam. Alternatively, the yam may be formed of fiberglass yam, polyester yam, PE fiber yam or other chemical fiber. [0025] Referring now to Fig. 2 there is illustrated a second embodiment flexible stranded optical fiber cable. In this embodiment, the outer sheath 4 is surrounded by a protective sheath 7 for additional protection of the optical fibers. Furthermore, in this embodiment, a layer 5 of aramid yam, aramid ribbon or aramid rope is disposed between the protective sheath and outer sheath to further enhance the tensile strength of the cable. However, it will be appreciated that, in other embodiments, the protective sheath 7 can be placed directly around the outer sheath 4 without the need for layer 5. [0026] It will be appreciated that the disclosure above provides a flexible stranded optical fiber cable, which has high strength and flexibility and is suitable for use in lightning prone areas and other areas generally unsuitable for metals. [0027] Advantages of the present invention, in at least some preferred embodiments, include: 1 . The central strength member in the cable core is a flexible central strength member, which possesses high strength and good flexibility and can effectively avoid lateral pressure and damage to the communication units This flexibility also makes the directly buried optical fiber cables adaptable to changes in the surrounding soil environment.

7 2. The cable is further strengthened by the addition of layers of chemical fiber yarn placed between the outer sheath and the cable core, and between the outer sheath and the surrounding protective sheath. 3. No metallic elements are used in the cable, making it suitable for use in lightning prone areas and other areas generally unsuitable for metals. [0028] It should be appreciated that in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, Fig., or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this invention. [0029] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination. [0030] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. [0031] Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention.

Claims (10)

1. A flexible stranded optical fiber cable for use in the field of communications, including a cable core and an outer sheath surrounding said cable core, said cable core including: a central strength member; and one or more communication units arranged in a stranded configuration within core about said central strength member; wherein said central strength member is a flexible central strength member.

2. A flexible stranded optical fiber cable according to claim I wherein said flexible central strength member is made of chemical fiber yarn or chemical fiber rope.

3. A flexible stranded optical fiber cable according to claim 2 wherein the chemical fiber yarn or chemical fiber rope is surrounded by a coating layer.

4. A flexible stranded optical fiber cable according to claim I or claim 2 wherein said one or more communication unit includes a loose tube and an optical fiber unit located within said loose tube, said optical fiber unit including one or more optical fibers, optical fiber bundles, optical fiber ribbons or tight buffered fibers, or combinations thereof.

5. A flexible stranded optical fiber cable according to claim 1 or claim 2 including a filling unit stranded together with said communication units, and a waterproof material filled in the space between said stranded communication units and the space between said communication units and said outer sheath.

6. A flexible stranded optical fiber cable according to claim I wherein chemical fiber yarn, chemical ribbon or chemical fiber rope is placed between said outer sheath and said cable core.

7. A flexible stranded optical fiber cable according to claim I including a protective sheath which surrounds the outer sheath and chemical fiber yarn, chemical fiber ribbon or chemical fiber rope is placed between the protective sheath and the outer sheath. 9

8. A flexible stranded optical fiber cable according to claim 2 wherein said chemical fiber yarn or chemical fiber rope is made of or woven with aramid yarn, fibreglass yarn, polyester yarn or PE fiber yarn.

9. A flexible stranded optical fiber cable according to claim 6 or claim 7 wherein said chemical fiber yarn, chemical fiber ribbon or chemical fiber rope is made of or woven with aramid yarn, fibreglass yarn, polyester yarn or PE fiber yarn.

10. A flexible stranded optical fiber cable substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings.