Claims:CLAIMS
We Claim:
1. An optical fiber cable (100) comprising:
a plurality of sleeves (104a-104f), wherein each of the plurality of sleeves (104a-104f) comprises a plurality of optical fibers (106):
one or more layers surrounding the plurality of sleeves (104a-104f), wherein the one or more layers comprising an aramid yarn binder layer and an outer sheathing layer, wherein the aramid yarn binder layer comprises a lay length in a range of 20 millimeters to 200 millimeters.

2. The optical fiber cable (100) as claimed in claim 1, wherein the plurality of sleeves (104a-104f) are stranded around a central strength member (102), and wherein each of the plurality of sleeves (104a-104f) comprises twelve optical fibers (106).

3. The optical fiber cable (100) as claimed in claim 1, wherein the outer sheathing layer is made up of a high density polyethylene (HDPE) material.

4. The optical fiber cable (100) as claimed in claim 1, wherein the optical fiber cable (100) comprises 24 sleeves (104a-104f) and 288 optical fibers (106).

5. The optical fiber cable (100) as claimed in claim 1, comprises a plurality of yarn threads (108) dispersed between each of the plurality of sleeves (104a-104f).
6. The optical fiber cable (100) as claimed in claim 1, comprises a water blocking tape layer for preventing ingression of water.

7. The optical fiber cable (100) as recited in claim 1, comprises one or more polyester made ripcords (116) for facilitating stripping of the outer sheathing layer.

8. The optical fiber cable (100) as claimed in claim 1, wherein the outer sheathing layer comprises a thickness in a range of 0.5 millimeter to 1 millimeter.

9. The optical fiber cable (100) as claimed in claim 1, wherein a lay length of the plurality of sleeves (104a-104f) is in a range of 60 millimeters to 600 millimeters.

10. The optical fiber cable (100) as claimed in claim 1, wherein each of the plurality of sleeves (104a-104f) is removed by bare hands or fingers.

11. The optical fiber cable (100) as claimed in claim 2, wherein the central strength member (102) is made up of a fiber reinforced plastic (FRP).

Dated: this 1st Day of October 2019
Signature:
Arun Kishore Narasani Patent Agent – IN/PA 1049

, Description:TECHNICAL FIELD
[0001] The present disclosure relates to the field of optical fiber cable and, in particular, relates to an optical fiber cable with a small diameter. The present application is patent of addition based on, and claims priority from an Indian Application Number 2209/MUM/2015 filed on 9th June, 2015, the disclosure of which is hereby incorporated by reference herein.

BACKGROUND
[0002] In the present scenario, optical fiber cables have secured an important position in building network of modern communication systems across the world. Conventionally, the optical fiber cables are installed by pulling the cables through the ducts. The ducts are usually made of polyethylene. Pulling the optical fiber cables requires a large amount of force to overcome the friction in the ducts which may damage the cables. Hence, an alternate technique of installation known as cable jetting is used for installation in which the optical fiber cable is blown through a duct, while simultaneously pushing the optical fiber cable into the duct. Micro-ducts are used for better utilization of the volume available in the standard ducts. The micro-ducts are small ducts which are designed to provide low-friction paths for placing the optical fiber cables. The micro-ducts have a diameter ranging from typically 3 to 18 millimeters and are bundled together in large or standard ducts.

[0003] A variety of conventional optical fiber cables exist in market that can be installed in micro-ducts. The conventional optical fiber cables include a central strength member with optical fibers stranded around it. These cables are specifically used to achieve higher fiber density. Moreover, the higher fiber density is fully attainable with an optical fiber cable that includes sleeves. The sleeves are loose buffered tubes and enclose one or more optical fibers. These sleeves are bunched together and housed in the optical fiber cable. In order to fit the optical fiber cable in a micro-duct, the optical fiber cable must have a small diameter.

[0004] The major drawback of the conventional type of cable design is that the sleeves may get damaged during the extrusion of the outer jacket on the stranded core due to the high shrinkage value of the polyester material.

[0005] In light of the foregoing discussion, there exists a need for an optical fiber cable which overcomes the above cited drawbacks of conventionally known optical fiber cables.

OBJECT OF THE DISCLOSURE
[0006] A primary object of the disclosure is to provide an optical fiber cable that is easy to install in micro-ducts.

[0007] Another object of the present disclosure is to provide an optical fiber cable that has a binder element made of high-strengthening binder yarns to prevent damage of sleeves in the optical fiber cable.

[0008] Yet another object of the present disclosure is to perform sheathing and stranding of the sleeves in tandem.

[0009] Yet another object of the present disclosure is to retain the lay length of the optical fiber cable.

[0010] Yet another object of the present disclosure is to prevent sticking of binding layer made of aramid yarn to a sheathing layer.

[0011] Yet another object of the present disclosure is to use the high strengthening aramid yarn as binder elements and strength members.

SUMMARY
[0012] In an aspect of the present disclosure, the present disclosure provides an optical fiber cable. The optical fiber cable comprising a plurality of sleeves, wherein each of the plurality of sleeves comprises a plurality of optical fibers, one or more layers surrounding the plurality of sleeves, wherein the one or more layers comprising an aramid yarn binder layer and an outer sheathing layer, wherein the aramid yarn binder layer comprises a lay length in a range of 20 millimeters to 200 millimeters.

[0013] In an embodiment, the plurality of sleeves are stranded around a central strength member, and each of the plurality of sleeves comprises twelve optical fibers.

[0014] In an embodiment, the outer sheathing layer is made up of a high density polyethylene (HDPE) material.

[0015] In an embodiment, the optical fiber cable comprises 24 sleeves and 288 optical fibers.

[0016] In an embodiment, the optical fiber cable comprises a plurality of yarn threads dispersed between each of the plurality of sleeves.
[0017] In an embodiment, the optical fiber cable comprises a water blocking tape layer for preventing ingression of water.

[0018] In an embodiment, the optical fiber cable comprises one or more polyester made ripcords for facilitating stripping of the outer sheathing layer.

[0019] In an embodiment, the outer sheathing layer comprises a thickness in a range of 0.5 millimeter to 1 millimeter.

[0020] In an embodiment, a lay length of the plurality of sleeves are in a range of 60 millimeters to 600 millimeters.

[0021] In an embodiment, each of the plurality of sleeves are removed by bare hands or fingers.

[0022] In an embodiment, the central strength member is made up of a fiber reinforced plastic (FRP).

STATEMENT OF THE DISCLOSURE
[0023] The present disclosure relates to optical fiber cable. The optical fiber cable includes a central strength member substantially along a longitudinal axis of the optical fiber cable. Further, the optical fiber cable includes a plurality of sleeves stranded around the central strength member. Furthermore, the optical fiber cable includes a first layer that surrounds the plurality of sleeves. Moreover, the optical fiber cable includes a second layer. The second layer surrounds the first layer. In addition, the optical fiber cable includes a third layer. The third layer surrounds the second layer. Further, each of the plurality of sleeves encloses a plurality of optical fibers. The plurality of sleeves is stranded around the central strength member to form a stranded core. The lay length of the plurality of sleeves is in a range of 60 millimeters-600 millimeters. Moreover, the first layer has one or more yarns. In addition, the first layer has a minimum thickness of 0.1 millimeter and the lay length of the first layer is in a range of 20 millimeters-200 millimeters. The lay length of the first layer is more than equal to one third of the lay length of the plurality of sleeve. Furthermore, the first layer acts as a binding element and a strength member for the plurality of sleeves. The one or more yarns are helically wound around the stranded core for binding each of the plurality of sleeves around the central strength member. Further, the one or more yarns prevent a tendency of opening up of the plurality of sleeves after a pre-defined number of turns due to reverse oscillations. Moreover, the second layer is placed to prevent ingression of water inside the plurality of sleeves. In addition, the second layer prevents sticking of the first layer and the third layer at a pre-determined range of temperature in a range of 160 OC-230 OC.

BRIEF DESCRIPTION OF FIGURES
[0024] Having thus described the disclosure in general terms, reference will now be made to the accompanying figures, wherein:

[0025] FIG. 1A illustrates a cross sectional view of an optical fiber cable, in accordance with various embodiments of the present disclosure; and

[0026] FIG. 1B illustrates a perspective view of the optical fiber cable of FIG. 1A, in accordance with various embodiments of the present disclosure.

[0027] It should be noted that the accompanying figures are intended to present illustrations of exemplary embodiments of the present disclosure. These figures are not intended to limit the scope of the present disclosure. It should also be noted that accompanying figures are not necessarily drawn to scale.

DETAILED DESCRIPTION
[0028] Reference will now be made in detail to selected embodiments of the present disclosure in conjunction with accompanying figures. The embodiments described herein are not intended to limit the scope of the disclosure, and the present disclosure should not be construed as limited to the embodiments described. This disclosure may be embodied in different forms without departing from the scope and spirit of the disclosure. It should be understood that the accompanying figures are intended and provided to illustrate embodiments of the disclosure described below and are not necessarily drawn to scale. In the drawings, like numbers refer to like elements throughout, and thicknesses and dimensions of some components may be exaggerated for providing better clarity and ease of understanding.

[0029] It should be noted that the terms "first", "second", and the like, herein do not denote any order, ranking, quantity, or importance, but rather are used to distinguish one element from another. Further, the terms "a" and "an" herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

[0030] FIG. 1A illustrates a cross sectional view of an optical fiber cable 100, in accordance with various embodiments of the present disclosure. Moreover, the optical fiber cable 100 has a small diameter to facilitate deployment in micro-ducts and closed narrow locations.

[0031] The optical fiber cable 100 includes a central strength member 102, a plurality of sleeves 104a-104f, a plurality of optical fibers 106, a plurality of yarn threads 108 and a first layer 110 (as seen in FIG. 1A in conjunction with the perspective view of the optical fiber cable 100 provided in FIG. 1B). Further, the optical fiber cable 100 includes a second layer 112, a third layer 114 and a rip cord 116. The central strength member 102 provides support to the plurality of sleeves 104a-104f. In addition, the central strength member 102 is substantially present along a longitudinal axis of the optical fiber cable 100. In an embodiment of the present disclosure, the central strength members 102 is made of a fiber reinforced plastic (hereinafter “FRP”). In another embodiment of the present disclosure, the central strength member is made of steel. In yet another embodiment of the present disclosure, the central strength member 102 is made of any suitable material. Examples of the suitable material include but may not be limited to copper, aramid yarn and fiber glass.

[0032] Further, the central strength member 102 is characterized by a diameter measured along the cross section. In an embodiment of the present disclosure, the diameter of the central strength member 102 is about 1.40 millimeters. In another embodiment of the present disclosure, the diameter of the central strength member 102 is about 2.80 millimeters. Moreover, the central strength member 102 may be coated. The central strength member 102 is coated when diameter of the optical fiber cable 100 is greater than 3 millimeters. Moreover, the central strength member 102 is coated to provide a cushion effect to the plurality of sleeves 104a-104f for consistent mechanical performance during installation and service. In addition, a coating made of Ethyl acrylic acid is placed around the central strength member 102. The central strength member 102 is prevents buckling of the optical fiber cable 100.

[0033] Moreover, the central strength member 102 is of circular cross-section. The cross section of the central strength member runs along the longitudinal axis of the optical fiber cable 100. The central strength member 102 provides robustness and tensile strength to the optical fiber cable 100. Further, the central strength member 102 is surrounded by the plurality of sleeves 104a-104f. The plurality of sleeves 104a-104f covers the plurality of optical fibers 106. Each of the plurality of sleeves 104a-104f is a tube for encapsulating the plurality of optical fibers 106. The plurality of sleeves 104a-104f provides support and protection to each of the plurality of optical fibers 106 against crush, bend and stretch.

[0034] In addition, the plurality of sleeves 104a-104f provides protects the plurality of optical fibers 106 and prevents ingression of water inside. In an embodiment of the present disclosure, the plurality of sleeves 104a-104f is made of thermoplastic co-polyester elastomer (hereinafter “TPE”). In another embodiment of the present disclosure, the plurality of sleeves 104a-104f is made of low smoke zero halogen (hereinafter “LSZH”) material. In yet another embodiment of the present disclosure, the plurality of sleeves 104a-104f is made of any other suitable material. The plurality of sleeves provides mechanical isolation, physical damage protection and identification of each of the plurality of fibers 106. In addition, each of the plurality of sleeves 104a-104f may be tear off by bare hands/fingers. The tear off of the plurality of sleeves 104a-104f by bare fingers facilitates easy access of each of the plurality of optical fibers 106.

[0035] Further, each sleeve of the plurality of sleeves 104a-104f has an inner diameter and an outer diameter. In an embodiment of the present disclosure, each sleeve of the plurality of sleeves 104a-104f has the outer diameter of about 1.3 millimeters and the inner diameter of about 1.05 millimeters. In addition, each sleeve of the plurality of sleeves 104a-104f encloses the plurality of optical fibers 106. Each of the plurality of optical fibers 106 is a standard ITU-T G.652D silica optical fiber. In an embodiment of the present disclosure, each sleeve of the plurality of sleeves 104a-104f includes 12 optical fibers. In another embodiment of the present disclosure, each sleeve of the plurality of sleeves 104a-104f includes more or less than 12 optical fibers. Further, the optical fiber cable 100 includes 12 fibers per sleeve. In addition, each of the plurality of sleeves 104a-104f may be a loose tube.

[0036] In addition, the plurality of optical fibers 106 in each sleeve may vary depending on the cable requirements. In an example, each sleeve of the plurality of sleeves 104a-104f carries 12 optical fibers 106. Moreover, the optical fiber cable 100 includes 6 sleeves 104a-104f, thereby making a total of 72 optical fibers 106 in the optical fiber cable 100. In another example, each sleeve of the plurality of sleeves 104a-104f carries 12 optical fibers. Moreover, the optical fiber cable 100 includes 24 sleeves, thereby making a total of 288 optical fibers in the optical fiber cable 100. The plurality of sleeves 104a-104f is stranded around the central strength member 102 to form a stranded core. In an embodiment of the present disclosure, the stranding of plurality of sleeves 104a-104f is helically stranded around the central strength member 102. The helical stranding is turning of each of the plurality of sleeves around the central strength member periodically in a pre-defined direction. The pre-defined direction is at least one of a clockwise direction and an anticlockwise direction. In another embodiment of the present disclosure, the plurality of sleeves 104a-104f is S-Z stranded around the central strength member 102. The binding is performed to retain lay length of the stranded plurality of sleeves and uniform stress distribution along length of the optical fiber cable 100.

[0037] Furthermore, the stranding of the plurality of sleeves 104a-104f is performed in order to provide the lay length. In general, the lay length is a longitudinal distance along length of the central strength member 102 required for one sleeve 104 to go all the way around the central strength member 102. The lay length of the plurality of sleeves 104a-104f is in a range of 60 millimeters–600 millimeters. Moreover, the S-Z fashion of stranding is a form of stranding of the plurality of sleeves 104a-104f. The plurality of sleeves 104a-104f are wound around the central strength member 102 in sections with a first direction of winding in S-shape alternating with sections with a second direction of winding in Z-shape. The first direction is the clockwise direction and the second direction is the anticlockwise direction. In addition, the S-Z stranding allows uniform distribution of the stress across all the plurality of sleeves 104a-104f.

[0038] The S-Z stranding may have any number of turns between the S-shape and the Z-shape. In an embodiment of the present disclosure, the number of turns is in a range of 3-5. In another embodiment of the present disclosure, the number of turns may be more or less than 5. Moreover, the SZ stranding of the plurality of sleeves 104a-104f facilitates mid-span operation for easy access of the plurality of optical fibers 106. Further, the plurality of yarn threads 108 is dispersed between each of the plurality of sleeves 104a-104f. The plurality of yarn threads facilitates absorption of water and moisture. Each of the plurality of yarn threads 108 prevents ingression of the water inside the optical fiber cable 100. The plurality of yarn threads 108 is made of a super absorbent polymer (hereafter “SAP”) coated polyester threads. In general, SAP is a polymer that absorbs and retains extremely large amounts of any liquid relative to their own mass. Examples of SAP materials include but may not be limited to polyacrylamide copolymer, ethylene maleic anhydride copolymer, cross-linked carboxymethyl cellulose, polyvinyl alcohol copolymers, cross-linked polyethylene oxide and starch grafted copolymer of polyacrylonitrile. In an embodiment of the present disclosure, the optical fiber cable 100 may have any number of yarn threads. In another embodiment of the present disclosure, the optical fiber cable has 3 yarn threads 108. In yet another embodiment of the present disclosure, the optical fiber cable 100 has more or less than 3 yarn threads 108.

[0039] Further, the first layer 110 surrounds the stranded plurality of sleeves 104a-104f. The first layer 110 act as a binding element and a strength member for the stranded plurality of sleeves 104a-104f. Moreover, the first layer 110 helically surrounds the stranded core of the plurality of sleeves 104a-104f. The first layer 110 binds the plurality of sleeves 104a-104f around the central strength member 102. The S-Z stranded plurality of sleeves 104 opens up after a certain number of turns due to reverse oscillations. The first layer 110 is used as the binding element to bind the stranded plurality of sleeves 104 to prevent the opening up of the S-Z stranded plurality of sleeves 104a-104f. Moreover, the first layer 110 provides retention in the lay length of the optical fiber cable 100. The first layer is made of a high strengthening aramid yarn.

[0040] The first layer 110 is a binding element for the stranded plurality of sleeves 104a-104f. The first layer has one or more yarns. In an embodiment of the present disclosure, number of yarn is 1. In another embodiment of the present disclosure, number of yarn is more or less than 1. Further, the first layer 110 has a thickness and the lay length. The pre-defined thickness of the first layer has a minimum value of 0.1 millimeter. The lay length of the first layer 110 is in a range of 20 millimeters-200 millimeters. In addition, the lay length of the first layer 110 is more than equal to one third of the lay length of the plurality of sleeves 104a-104f. Furthermore, the first layer 110 is surrounded by the second layer 112. In an embodiment of the present disclosure, the second layer 112 is a water blocking tape. In another embodiment of the present disclosure, the second layer 112 is a yarn layer. The second layer 112 prevents ingression of the water inside the optical fiber cable 100. Accordingly, the second layer prevents exposure of the plurality of sleeves 104a-104f and the plurality of optical fibers 106 to hydroxyl ions. In addition, the second layer 112 has a coating of the SAP material.

[0041] Further, the second layer 112 is characterized by width and thickness. In an embodiment of the present disclosure, the width of the second layer 112 is about 18 millimeters. In another embodiment of the present disclosure, the width of the second layer 112 is about 30 millimeters. In an embodiment of the present disclosure, the thickness of the second layer 112 is about 0.3 millimeters. In another embodiment of the present disclosure, the thickness of the second layer is more or less than 0.3 millimeter. Moreover, the third layer 114 surrounds the second layer 112. The third layer 114 layer interacts directly with ambient environment. In addition, the third layer is a sheathing layer. The third layer 114 protects the optical fiber cable 100 against the crush, the bend and tensile stress along the length of the optical fiber cable 100.

[0042] In addition, the third layer 114 with shrinkage during negative temperature conditions results in an increase in length of the plurality of sleeves 104a-104f present inside the optical fiber cable 100. In general, after the suitable material for the third layer 114 is extruded over the stranded core of the optical fiber cable 100. The suitable material passes through a water trough to quench relatively hot third layer 114. When the suitable material cools during the quenching process, the shrinkage of the third layer 114 may occur. The shrinkage of the third layer 114 may result in an undulated stranded core with undesirable compressive axial stress and/or strains. The increase in the length of the plurality of sleeves 104a-104f results in micro and macro bends inside each of the plurality of optical fibers 106. The micro and the macro bends inside each of the plurality of optical fibers 106 results in higher attenuation in the optical fiber cable 100. Moreover, the central strength member 102 acts as anti-buckling element and prevents the third layer 114 from the shrinkage during the negative temperature conditions.

[0043] In an embodiment of the present disclosure, the third layer 114 is made of a high density poly-ethylene material (hereinafter “HDPE”). In another embodiment of the present disclosure, the third layer 114 is made of a medium density poly-ethylene material (hereinafter “MDPE”). In yet another embodiment of the present disclosure, the third layer 114 is made of any suitable material. In an embodiment, the third layer 114 has a thickness of about 0.5 millimeters. In another embodiment of the present disclosure, the third layer 114 has the thickness of about 1 millimeter. In yet another embodiment of the present disclosure, the third layer 114 has thickness more or less than 1 millimeter.

[0044] Moreover, the second layer 112 is placed underneath the third layer 114. In addition, the second layer 112 prevents sticking of the first layer 110 and the third layer 114 at a pre-determined range of temperature. The pre-determined range of temperature is 160 OC to 230 OC.

[0045] Further, the first rip cord 116 is positioned at an interface of the second layer 112 and the third layer 114. The rip cord 116 extends longitudinally between the third layer 114 and the second layer 112. The extension of the rip cord 116 longitudinally along the length of the optical fiber cable 100 facilitates stripping of the third layer 114. In an embodiment of the present disclosure, the rip cord 116 is made of a polyester material and the rip cord 116 has circular cross-section. In another embodiment of the present disclosure, the rip cord 116 is made of any suitable material.

[0046] In an embodiment of the present disclosure, a plurality of rip cords is positioned along the length of the optical fiber cable 100. In another embodiment of the present disclosure, the optical fiber cable 100 has no rip cord. Further, the optical fiber cable 100 may have any dimension based on dimensions of individual layers in the structure of the optical fiber cable 100. In an embodiment of the present disclosure, the diameter of the stranded core is about 4.1 millimeter and the optical fiber cable 100 has the diameter of about 5.1 millimeters. In another embodiment of the present disclosure, the diameter of the stranded core is about 5.5 millimeters. The stranded core includes 9 sleeves stranded around the central strength member 102. In yet another embodiment of the present disclosure, the diameter of the stranded core is about 7.6 millimeters and the optical fiber cable 100 has the diameter of about 9.9 millimeters. In addition, the stranded core includes 15 plurality of sleeves stranded around the central strength member 102. In addition, the optical fiber cable 100 has the diameter of 5.1 millimeter.

[0047] Further, it may be noted that in FIG. 1A and FIG. 1B, the optical fiber cable 100 includes six sleeves 104a-104f; however, those skilled in the art would appreciate that more or less number of sleeves are included in the optical fiber cable 100. Moreover, it may be noted that in FIG. 1A, the optical fiber cable 100 includes one yarn thread; however, those skilled in the art would appreciated that more number of yarn threads are present in the optical fiber cable 100.

[0048] The optical fiber cable has several advantages over the prior art. The handling of optical fiber cable during the installation process does not require special tools to peel off the sleeves. The sleeves can be peeled off using fingers. The sleeves require less amount of gel which reduces messiness and clean up time during the installation process. Therefore, the optical fiber cable requires less time for installation. The arrangement of the first layer, the water blocking tape and the third layer in the optical fiber cable prevents the sticking of the first layer and a third layer. The sleeves are very delicate due to small thickness. During extrusion of the third layer on the stranded core, the sleeves along with the binding element are subjected to compression forces. If there is significant shrinkage of the binding element, the sleeves may get damaged resulting in higher signal losses of the optical fiber cable. The high-strengthening binder yarns such as aramid yarns are preferred as binding elements over the polyester-based yarns, as they have a lower shrinkage value compared to the polyester-based yarns.

[0049] Therefore, depression of the sleeves that occurs due to shrinking of binder yarns can be minimized. The optical fiber cable is mostly suitable for blowing in to micro-ducts. The optical fiber cable requires relatively low tensile strength compared to regular micro-duct cables as less pulling is involved.

[0050] The foregoing descriptions of pre-defined embodiments of the present technology have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present technology to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present technology and its practical application, to thereby enable others skilled in the art to best utilize the present technology and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present technology.