Claims:CLAIMS
We claim:
1. A sheath (102) for use in an optical fiber cable (100) comprising:
one or more strength members (108) embedded in the sheath (102), wherein the one or more strength members are coated with a coating material having at least one of an ultraviolet (UV) curable water swellable resin composition and a layer of ethylene acrylic acid (EAA).

2. The sheath (102) as claimed in claim 1, wherein the UV curable water swellable resin composition includes, but not limited to, acrylic acid, phenyl bis(2,4,6-trimethylbenzoyl)-phosphine oxide and oxybis(methyl-2,1-ethanediyl) diacrylate.

3. The sheath (102) as claimed in claim 1, wherein the coating material applied over the one or more strength members (108) has a thickness of 50±10 microns.

4. The sheath (102) as claimed in claim 1, wherein the one or more strength members (108) are made of fiber reinforced plastic (FRP), aramid reinforced plastic (ARP) or any other suitable material.

5. The sheath (102) as claimed in claim 1 used in the optical fiber cable (100) that is capable of passing a water penetration test where -0.1 bar pressure water-head applied to a 3m cable sample kept for at least 24 hours.

6. The sheath (102) as claimed in claim 1, wherein the UV curable water swellable resin composition is applied directly on the one or more strength members (108) or above a thin layer of EAA.

7. The sheath (102) as claimed in claim 1, wherein the UV curable water swellable resin composition coated one or more strength members (108) are passed through one or more UV chambers to cure the UV curable water swellable resin composition.

8. An optical fiber cable (100) comprising:
a core including a plurality of optical fibers;
a sheath (102) enveloping the core; and
one or more strength members (108) embedded in the sheath (102), wherein the one or more strength members are coated with a coating material having at least one of an ultraviolet (UV) curable water swellable resin composition and a layer of ethylene acrylic acid (EAA);
wherein the optical fiber cable (100) passes water penetration test.

9. The optical fiber cable (100) as claimed in claim 8, wherein the UV curable water swellable resin composition includes, but not limited to, acrylic acid, phenyl bis(2,4,6-trimethylbenzoyl)-phosphine oxide and oxybis (methyl-2,1-ethanediyl) diacrylate.

10. The optical fiber cable (100) as claimed in claim 8, wherein the coating material applied over the one or more strength members (108) has a thickness of 50±10 microns.

11. The optical fiber cable (100) as claimed in claim 8, wherein the one or more strength members (108) embedded in the sheath (102) are made of fiber reinforced plastic (FRP), aramid reinforced plastic (ARP) or any other suitable material.

Description:TECHNICAL FIELD
[0001] The present invention relates to the field of optical communication technology and, in particular, relates to a ribbed and grooved cable. The present application is based on, and claims priority from an Indian Application Number 202011024930 filed on 13th June 2020 and an Indian Application Number 202011045978 filed on 22nd October 2020, the disclosure of which is hereby incorporated by reference herein.

BACKGROUND
[0002] With the technological and scientific advancements, various modern communication technologies have been introduced and employed. One of the most important modern communication technologies is optical fiber communication technology using a variety of optical fiber cables. The optical fiber cables are widely used for communication to meet the increasing demands of end-users. To meet the increasing demands, installation of the optical fiber cables at a rapid pace becomes essential. The optical fiber cables for telecommunication application are installed in ducts. The installation of the optical fiber cables in the ducts is mostly performed using a blowing method, wherein, the blowing method to install the optical fiber cables in the ducts is dependent on a plurality of factors. The plurality of factors includes mass of the optical fiber cable, friction, stiffness, and the like. The blowing method enables installation of the optical fiber cable using pressurized air combined with additional mechanical pushing force that is called as “blowing”.
[0003] In general, the blowing method is the process of installation of the optical fiber cable into a pre-installed duct. The blowing is performed by injecting pressurized air in inlet of the pre-installed duct before the optical fiber cable is pushed into the pre-installed duct. The pressurized air flows at high speed through the pre-installed duct and along the optical fiber cable. Also, pushing force is applied near the optical fiber cable inlet by a pushing device. The optical fiber cable includes uni-tube, multi-tube, unarmoured, armoured, micro duct cable, and the like. However, conventional structure of the optical fiber cable having a sheath with a smooth surface makes it inefficient to allow pressurized air to blow the optical fiber cable in the pre-installed duct. In addition, the conventional optical fiber cable resists the pushing force due to higher coefficient of friction. Further, the conventional optical fiber cable has higher number of contact points with the pre-installed duct. Furthermore, the conventional optical fiber cable has heavy weight.
[0004] Additionally, strength members are one of the important components of the optical fiber cable. The purpose of the strength members is to provide the optical fiber cable rigidity, bend resistance, mechanical strength and ease in blowing. A strength member can be installed either at a center of the optical fiber cable or embedded inside the sheath of the optical fiber cable. The strength member embedded inside the sheath is normally preferred over a central strength member for making a high density optical fiber cable as there is more space available in the center. After embedding the strength member in the sheath of the optical fiber cable, often water penetration occurs through the embedded strength member. The main reason is, during the embedding of the strength member inside the sheath, some clearance remains between the strength member and the sheath due to manufacturing tolerances. Generally, the water may penetrate even through a clearance of a few dozen microns. A water penetration test of the optical fiber cable is often carried out to assess the ability of the optical fiber cable to resist the water penetration in the optical fiber cable. Such water penetration assessments are necessary because water once penetrated through the clearance between the strength member and the sheath due to manufacturing tolerances, may travel to optical fiber junction boxes and may degrade optical properties of the components such as optical fibers. Also, water penetration through a length of the optical fiber cable further leads to degradation of other components of optical network.
[0005] For example, a prior-art reference WO2020075734A1 discloses an optical fiber cable having a plurality of ribs on the surface of the optical fiber cable for improved blowing performance, however the ribs are of same height.
[0006] In view of the aforementioned discussion and prior-art reference, there exists a need for an optical fiber cable that overcomes the above cited disadvantages. Accordingly, the present disclosure provides a ribbed and grooved cable having embedded strength member with water blocking coating.
[0007] Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge.

OBJECT OF THE DISCLOSURE
[0008] A primary object of the present disclosure is to provide a ribbed and grooved cable that reduces coefficient of friction between a cable sheath and a duct.
[0009] Another object of the present disclosure is to provide the ribbed and grooved cable having embedded strength member(s) in the cable sheath with a water blocking coating to provide mechanical strength and ease of blowing to the ribbed and grooved cable and to prevent water ingression inside the ribbed and grooved cable.
[0010] Another object of the present disclosure is to provide the ribbed and grooved cable that has inner grooves for reducing mass of the ribbed and grooved cable while increasing free space for optical fibers or ribbons in the ribbed and grooved cable.

SUMMARY
[0011] Accordingly, a sheath for use in an optical fiber cable and the optical fiber cable is disclosed, where one or more strength members are embedded in the sheath and the one or more strength members are coated with a coating material having at least one of an ultraviolet (UV) curable water swellable resin composition and a thick layer of ethylene acrylic acid (EAA). That is, the sheath envelops a core and the core includes a plurality of optical fibers. The plurality of optical fibers may be incorporated in the core as a plurality of loose tube optical fibers, a plurality of tight buffered optical fibers, a group or stack of optical fiber ribbons or the like. The UV curable water swellable resin composition includes, but not limited to, acrylic acid, phenyl bis(2,4,6-trimethylbenzoyl)-phosphine oxide and oxybis(methyl-2,1-ethanediyl) diacrylate. The coating material applied over the one or more strength members has a thickness of 50±10 microns. The one or more strength members are made of fiber reinforced plastic (FRP), aramid reinforced plastic (ARP) or any other suitable material. The sheath is used in the optical fiber cable that is capable of passing a water penetration test where -0.1 bar pressure water-head applied to a 3m cable sample kept for at least 24 hours. The UV curable water swellable resin composition is applied directly on the one or more strength members or above the layer of EAA. The UV curable water swellable resin composition coated one or more strength members are passed through one or more UV chambers to cure the UV curable water swellable resin composition.
[0012] These and other aspects herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the invention herein without departing from the spirit thereof.

BRIEF DESCRIPTION OF THE FIGURES
[0013] The invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the drawings. The invention herein will be better understood from the following description with reference to the drawings, in which:
[0014] FIG. 1 illustrates a design of a sheath of a cable having a plurality of ribs and a plurality of grooves on an external surface of the sheath and strength members embedded inside the sheath in a first configuration.
[0015] FIG. 2 illustrates the design of the sheath of the cable having the plurality of ribs and the plurality of grooves on the external surface of the sheath and strength members embedded inside the sheath in a second configuration.
[0016] FIG. 3 illustrates the design of the sheath of the cable with the plurality of ribs of different heights.
[0017] FIG. 4 illustrates the design of the sheath having a plurality of internal grooves, a plurality of external grooves, a plurality of internal ribs and a plurality of external ribs.
[0018] FIG. 5 illustrates the design of the sheath of the cable having embedded strength members placed below the plurality of ribs.
[0019] FIG. 6 illustrates the design of the sheath of the cable having the plurality of grooves and the plurality of ribs extruded in a linear manner along a length of the cable .
[0020] FIG. 7 illustrates the design of the sheath of the cable having the plurality of grooves and the plurality of ribs extruded helically along the length of the cable.
[0021] FIG. 8 illustrates the design of the sheath of the cable having the plurality of internal grooves, the plurality of external grooves, the plurality of internal ribs and the plurality of external ribs.
[0022] FIG. 9 illustrates a strength member of FIGS. 1 to 8 coated with a coating material.
[0023] FIG. 10 illustrates a water penetration test arrangement for the cable.

DETAILED DESCRIPTION
[0024] In the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be obvious to a person skilled in the art that the invention may be practiced with or without these specific details. In other instances, well known methods, procedures and components have not been described in details so as not to unnecessarily obscure aspects of the invention.
[0025] Furthermore, it will be clear that the invention is not limited to these alternatives only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art, without parting from the scope of the invention.
[0026] The accompanying drawings are used to help easily understand various technical features and it should be understood that the alternatives presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another.
[0027] FIG. 1 illustrates a design of a sheath of a cable 100. The cable 100 has a ribbed and grooved sheath and thus is termed as a ribbed and grooved cable. The cable 100 has a high blowing performance because number of contact points are reduced which further reduces coefficient of friction. The cable 100 includes a plurality of optical fibers (not shown) and the sheath 102 having a plurality of ribs 104 and a plurality of grooves 106. The plurality of optical fibers may be incorporated in the core as a plurality of loose tube optical fibers, a plurality of tight buffered optical fibers, a group or stack of optical fiber ribbons or the like. Herein, the ribs are a longitudinal protrusion formed on an outer/external surface of the sheath 102 and are parallel to an axis of the cable 100. Further, the grooves are formed between two consecutive ribs. The sheath 102 has a plurality of strength members 108 embedded into it.
[0028] The sheath 102 includes an inner surface and an outer surface. In general, sheath is an outer layer of a cable that protects the cable from environmental conditions. In addition, the environment conditions include but may not be limited to rainfall, sunlight, snowfall, and wind. The sheath 102 of the cable 100 encloses the plurality of optical fibers concentrically along a length of the optical fiber cable, wherein the sheath has an outer surface and an inner surface. The outer surface of the sheath 102 of the cable 100 includes the plurality of ribs 104 and the plurality of grooves 106. The plurality of ribs 104 and the plurality of grooves 106 are formed on the outer surface of the sheath 102, thus may be called as a plurality of external ribs and a plurality of external grooves throughout the disclosure. In an implementation, number of the plurality of ribs 104 is same as number of the plurality of grooves 106.
[0029] Each of the plurality of ribs 104 has a height in range of about 0.1 millimeter to 2 millimeters. Preferably, the plurality of ribs 104 has the height in range of about 0.1 millimeter to 1 millimeter for the sheath 102 having a thickness of up to 3.5 millimeters. For the height below 0.1mm, the ribs are difficult to manufacture and for the height beyond 1mm, the sheath may become mechanically weak because of removal of material. Alternatively, the height of the plurality of ribs 104 may vary. The plurality of ribs 104 has a width in range of about 0.4 millimeter to 20 millimeter. Preferably, the plurality of ribs 104 has the width in range of about 0.5 millimeter to 4 millimeter for the cable 100 having an outer diameter of up to 35 millimeter. For the width below 0.5mm, the ribs will be mechanically weak and beyond the width 4mm, the blowing performance may reduce. Alternatively, width of the plurality of ribs 104 may vary. In an implementation, number of the plurality of ribs 104 is 12. Alternatively, number of the plurality of ribs 104 may vary depending upon width of the plurality of ribs 104. In an implementation, number of grooves 106 is 12. Further, number of the plurality of grooves 106 may vary depending upon the width of the plurality of grooves 106 and the outer diameter of the cable. In an implementation, as shown in FIG. 1, a cross-sectional area of the sheath corresponding to 12 ribs and 12 grooves is about 44.45 millimeter square. Alternatively, area of the cable may vary depending upon internal diameter of the cable, external diameter of the cable, number of the plurality of ribs 104 and the plurality of grooves 106.
[0030] The cable 100 has deformation of about 0.59 millimeter under crushing load at 500 Newton per 100 millimeter. Alternatively, deformation of the cable 100 may vary. In addition, deformation of the cable 100 may vary depending upon a plurality of parameters. The plurality of parameters includes but may not be limited to number of the plurality of ribs 104 and the plurality of grooves 106, width and height of the plurality of ribs 104 and the plurality of grooves 106, inside and outside diameter of the cable 100, number of the plurality of strength members 108 in the sheath 102, and material grade of the cable 100.
[0031] The plurality of ribs 104 and the plurality of grooves 106 reduce coefficient of friction between the sheath 102 and a duct. The plurality of ribs 104 and the plurality of grooves 106 are arranged alternately to each other on the outer surface of the sheath 102. In an example, a groove of the plurality of grooves 106 is present on both sides of each rib of the plurality of ribs 104. In another example, a rib of the plurality of ribs 104 is present on both sides of each groove of the plurality of grooves 106. In an implementation, height of each of the plurality of ribs 104 is equal. Alternatively, depth of each of the plurality of grooves 106 is equal.
[0032] The cable 100 is installed into the duct using a blowing process. Further, the duct surrounds the cable 100. The blowing process to install the cable 100 in the duct is dependent on a plurality of factors. The plurality of factors includes mass of the cable 100, friction between the cable 100 and the duct, stiffness of the cable 100, and the like. Also, the blowing process enables installation of the cable 100 using pressurized air combined with a mechanical pushing force.
[0033] Further, the cable 100 includes the plurality of strength members 108. Furthermore, each of the plurality of strength members 108 is embedded in the sheath 102. Each of the plurality of strength elements 108 in the sheath 102 may be positioned differently. The plurality of strength members 108 enhances blowing performance of the cable 100 by increasing stiffness of the cable 100. Moreover, the plurality of strength members 108 provides tensile strength to the cable 100. In an implementation, number of the plurality of strength members 108 embedded in the sheath 102 of the cable 100 is in the range of 4 to 18. The number of strength members below 4 may lead to difficulties to achieve uniform stiffness in the cable 100. The number of strength members above 4 may lead over-stiffness in the cable. Alternatively, number of the plurality of strength members 108 may vary.
[0034] FIG. 2 illustrates the design of the sheath of the cable 100. In an implementation, number of the plurality of ribs 104 in the sheath 102 (of FIG. 2) is 18. Alternatively, number of the plurality of ribs 104 in the sheath 102 may vary. Further, number of the plurality of grooves 106 in the sheath 102 is 18. Alternatively, number of the plurality of grooves 106 may vary.
[0035] In an implementation, area of the cable 100 corresponding to 18 ribs and 18 grooves is about 44.28 millimeter square. Alternatively, area of the cable may vary depending upon internal diameter of the cable, external diameter of the cable, number of the plurality of ribs 104 and the plurality of grooves 106. The cable 100 has deformation of about 0.63 millimeter under crushing load at 500 Newton per 100 millimeter. Alternatively, deformation of the cable 100 may vary. In addition, deformation of the cable 100 may vary depending upon the plurality of parameters. The plurality of parameters includes but may not be limited to number of the plurality of ribs 104 and the plurality of grooves 106, width and height of the plurality of ribs 104 and the plurality of grooves 106, inside and outside diameter of the cable 100, number of the plurality of strength members 108 in the sheath 102, and material grade of the cable 100.
[0036] The plurality of ribs (i.e. the plurality of external ribs) 104 and the plurality of grooves (i.e. the plurality of external grooves) 106 (of FIG. 2) are arranged alternately to each other on the outer surface of the sheath 102. In an example, a groove of the plurality of grooves 106 is present on both sides of each rib of the plurality of ribs 104. In another example, a rib of the plurality of ribs 104 is present on both sides of each groove of the plurality of grooves 106. In an implementation, height of each of the plurality of ribs 104 is equal. Further, depth of each of the plurality of grooves 106 is equal. The plurality of ribs 104 and the plurality of grooves 106 may have any suitable shape including but not limited to arc, rectangular, square, triangular, trapezoidal etc.
[0037] FIG. 3 illustrates the design of the sheath of the cable 100. The plurality of ribs 104 includes a first type of ribs and a second type of ribs. Each rib of the first type of ribs has large size. Each rib of the second type of ribs has smaller size as compared to the first type of ribs. In an implementation, height of the first type of ribs (i.e. a first height) is larger than height of the second type of ribs (i.e. a second height). In an example, during installation of the cable 100 into a duct, only the first type of ribs touches the duct. In addition, the second type of ribs does not touch the duct due to small size of the second type of ribs.
[0038] Further, number of the first type of ribs is equal to the number of second type of ribs. The first type of ribs and the second type of ribs are arranged alternately to each other. The alternate arrangement of the first type of ribs and the second type of ribs reduces weight of the cable 100. In addition, the alternate arrangement of the first type of ribs and the second type of ribs reduces friction in the cable 100. In an implementation, number of the first type of ribs is 6. Alternatively, number of the first type of ribs may vary. Further, number of the second type of ribs is 6. Alternatively, number of the second type of ribs may vary. Alternatively, number of the plurality of ribs 104 (first type of ribs and second type of ribs) is 12. Alternatively, number of the plurality of ribs 104 may vary.
[0039] Further, in an implementation as shown in FIG. 3, area of the cable 100 corresponding to 12 ribs is about 43.66 millimeter square. Alternatively, area of the cable 100 may vary depending upon internal diameter of the cable, external diameter of the cable, number of the plurality of ribs 104. The cable 100 has deformation of about 0.59 millimeter under crushing load at 500 Newton per 100 millimeter. Alternatively, deformation of the cable 100 may vary. In addition, deformation of the cable 100 may vary depending upon the plurality of parameters. The plurality of parameters includes but may not be limited to number of the plurality of ribs 104 and the plurality of grooves 106, width and height of the plurality of ribs 104 and the plurality of grooves 106, inside and outside diameter of the cable 100, number of the plurality of strength members 108 in the sheath 102, and material grade of the cable 100.
[0040] FIG. 4 illustrates the design of the sheath of the cable 100. The cable 100 includes the sheath 102. The sheath 102 has the plurality of ribs 104, the plurality of grooves 106, and the plurality of strength members 108. The plurality of ribs 104 is formed on the outer surface of the sheath 102 and may be referred to as the plurality of external ribs while referring to FIG. 4. Further, the sheath 102 includes a plurality of internal ribs 104a formed on an internal surface of the sheath 102. In an implementation, number of the plurality of ribs 104 on the outer surface of the sheath 102 of the cable 100 is 12. Alternatively, number of the plurality of ribs 104 on the outer surface of the sheath 102 of the cable 100 may vary. Each of the plurality of ribs 104 has height of about 0.5 millimeter. Alternatively, height of the plurality of ribs 104 may vary.
[0041] The sheath 102 includes the plurality of grooves 106. The plurality of grooves 106 is also called as the plurality of external grooves while referring to FIG. 4. Further, the sheath 102 includes a plurality of internal grooves 106a formed on an inner/internal surface of the sheath 102. The plurality of internal grooves 106a reduce mass of the cable 100. In addition, the plurality of internal grooves 106a increase free space for optical fibers or ribbons in the cable 100. The plurality of external grooves 106 is formed on the outer surface of the sheath 102. In an implementation, number of the plurality of internal grooves 106a on the inner surface of the sheath 102 is 6. Alternatively, number of the plurality of internal grooves 106a on the inner surface of the sheath 102 may vary. The plurality of internal grooves 106a has a depth of about 0.5 millimeter. Alternatively, the depth of the plurality of internal grooves 106a may vary. In an implementation, number of the plurality of external grooves 106 on the outer surface of the sheath 102 is 12. Alternatively, number of the plurality of external grooves 106 on the outer of the sheath 102 may vary.
[0042] Further, area of the cable 100 corresponding to 12 external ribs and 6 internal grooves is about 41.05 millimeter square. Alternatively, area of the cable may vary depending upon internal diameter of the cable, external diameter of the cable, number of the plurality of ribs 104. The cable 100 has deformation of about 1.80 millimeter under crushing load at 500 Newton per 100 millimeter. Alternatively, deformation of the cable 100 may vary. In addition, deformation of the cable 100 may vary depending upon the plurality of parameters. The plurality of parameters includes but may not be limited to number of the plurality of ribs 104 and number of the plurality of internal grooves 106a and the plurality of external grooves 106, width and height of the plurality of ribs 104 and the plurality of grooves 106, inside and outside diameter of the cable 100, number of the plurality of strength members 108 in the sheath 102, and material grade of the cable 100.
[0043] FIG. 5 illustrates the design of the sheath of the cable 100, wherein the plurality of ribs 104 includes a first type of ribs and a second type of ribs. Each rib of the first type of ribs has large size. Each rib of the second type of ribs has a smaller size as compared to the first type of ribs. Further, height of the first type of ribs (i.e. the first height) is larger than height of the second type of ribs (i.e. the second height).
[0044] In an implementation, number of the first type of ribs is equal to the number of second type of ribs. The first type of ribs and the second type of ribs are arranged alternately to each other. The alternate arrangement of the first type of ribs and the second type of ribs reduce weight of the cable 100. In addition, the alternate arrangement of the first type of ribs and the second type of ribs reduces friction in the cable 100. In an example, number of the first type of ribs is 9. Alternatively, number of the first type of ribs may vary. Further, number of the second type of ribs is 9. Alternatively, number of the second type of ribs may vary.
[0045] Herein, number of the plurality of ribs 104 (first type of ribs and second type of ribs) is 18. Alternatively, number of the plurality of ribs 104 may vary. Further, number of the plurality of grooves 106 in the cable 100 is 18. Alternatively, number of the plurality of grooves 106 may vary.
[0046] Further, area of the cable 100 corresponding to 18 ribs is about 42.17 millimeter square. Alternatively, area of the cable 100 may vary depending upon internal diameter of the cable, external diameter of the cable, number of the plurality of ribs 104. The cable 100 has deformation of about 0.45 millimeter under crushing load at 500 Newton per 100 millimeter. Alternatively, deformation of the cable 100 may vary. In addition, deformation of the cable 100 may vary depending upon the plurality of parameters. The plurality of parameters includes but may not be limited to number of the plurality of ribs 104 and number of internal grooves of the plurality of grooves 106, width and height of the plurality of ribs 104 and the plurality of grooves 106, inside and outside diameter of the cable 100, number of the plurality of strength members 108 in the sheath 102, and material grade of the cable 100. The plurality of ribs 104 and the plurality of grooves 106 of the cable 100 (of FIG. 5) are arranged alternately to each other on the outer surface of the sheath 102.
[0047] In an example, height of the first type of ribs of the cable 100 i.e. the first height is 0.5 millimeter. In addition, height of the second type of ribs of the cable 100 i.e. the second height is 0.25 millimeter. In another example, height of the first type of ribs (i.e. the first height) of the cable 100 may vary. In addition, height of the second type of ribs (i.e. the second height) of the cable 100 may vary.
[0048] The alternate arrangement of the first type of ribs and the second type of ribs enables high crushing performance. In addition, the first type of ribs support the second type of ribs when a fixed crush load is applied on the cable 100 that enables high crushing performance as compared to the similar design of cable where all the ribs having equal height. Further, number of the first type of ribs and the second type of ribs is an odd number. Furthermore, the odd number of the first type of ribs and the second type of ribs ensures that each of the first type of ribs is diametrically opposite to corresponding rib of the second type of ribs. Moreover, the odd number of the first type of ribs and the second type of ribs eliminates dependency on orientation of the fixed crush load on the cable 100.
[0049] In an example, the sheath 102 having more number of the first type of ribs (large sized ribs) has small lateral deformations. Adjacent ribs provide support to cross section of the cable 100 when the cable starts to deform and take an elliptical shape. In another example, the sheath 102 have less number of plurality of ribs 104. The plurality of ribs 104 are more spaced out in the sheath 102 due to less number of plurality of ribs 104. In addition, the sheath 102 with less number of plurality of ribs 104 does not provide support to cross section of the cable 100 even at low forces.
[0050] The plurality of ribs 104 and the plurality of grooves 106 are extruded longitudinally along length of the cable 100 (as shown in FIG. 6). Alternatively, the plurality of ribs 104 and the plurality of grooves 106 are extruded helically along length of the cable 100 (as shown in FIG. 7). Alternatively, the plurality of ribs 104 and the plurality of grooves 106 are extruded in SZ fashion. Alternatively, the plurality of ribs 104 and the plurality of grooves 106 may be extruded in any suitable shape.
[0051] FIG. 8 illustrates the design of the sheath of the cable 100. The cable 100 includes the sheath 102. The sheath 102 includes the plurality of ribs 104 on the external surface of the sheath (referred to as the plurality of external ribs 104 with reference to FIG. 8), the plurality of grooves 106 on the external surface of the sheath (referred to as the plurality of external grooves 106 with reference to FIG. 8), the plurality of internal ribs 104a, the plurality of internal grooves 106a and the plurality of strength members 108. The plurality of ribs 104 includes the first type of ribs and the second type of ribs. Each rib of the first type of ribs has large size. Each rib of the second type of ribs has a smaller size as compared to the first type of ribs. Further, height of each of the first type of ribs (i.e. the first height) is larger than height of each of the second type of ribs (i.e. the second height)..
[0052] Further, number of the first type of ribs is equal to the number of second type of ribs. The first type of ribs and the second type of ribs are arranged alternately to each other. The alternate arrangement of the first type of ribs and the second type of ribs reduces weight of the cable 100. In addition, the alternate arrangement of the first type of ribs and the second type of ribs reduces friction in the cable 100. Further, number of the first type of ribs is 6. Alternatively, number of the first type of ribs may vary. Furthermore, number of the second type of ribs is 6. Alternatively, number of the second type of ribs may vary. In an implementation, number of the plurality of ribs 104 (first type of ribs and second type of ribs) is 12. Alternatively, number of the plurality of ribs 104 may vary.
[0053] The cable 100 includes the plurality of grooves 106. In addition, the plurality of grooves 106 corresponds to the internal grooves. The plurality of ribs 104 surrounds the plurality of grooves 106. The plurality of grooves 106 (the internal grooves) are formed on the inner surface of the sheath 102. Further, number of the internal grooves on the inner surface of the sheath 102 is 6. Alternatively, number of the internal grooves on the inner surface of the sheath 102 may vary.
[0054] In the sheath with the ribs of different heights, the outer diameter upto 13mm and a sheath thickness upto 2.5mm, the first height may be in a range of 0.2-1.0 millimeter (mm) and the second height may be in the range of 0.1-0.5 millimeter. Preferably, the first height may be in the range of 0.1-0.5 millimeter and the second height may be in the range of 0.2-1.0 millimeter. Below the first height of 0.1mm, the ribs will be difficult to manufacture and above the first heigh of 0.5mm, the sheath may become mechanically weak. Further, the plurality of ribs 104 may have a width in the range of 0.8-6.5 millimeter. Below the width of 0.8mm, the ribs will be mechanically weak and beyond the width of 6.5mm, the blowing performance will be affected. Furthermore, the plurality of grooves 106 may have a width in the range of 0.8-6.5 millimeter.
[0055] The alternate arrangement of the first type of ribs and the second type of ribs enables high crushing performance. The first type of ribs support the second type of ribs when a fixed crush load is applied on the cable 100 that enables high crushing performance as compared to the similar design of cable where all the ribs having equal height.
[0056] In an implementation, number of the first type of ribs and the second type of ribs is an odd number. The odd number of the first type of ribs and the second type of ribs ensures that each of the first type of ribs is diametrically opposite to corresponding rib of the second type of ribs. Moreover, the odd number of the first type of ribs and the second type of ribs eliminates dependency on orientation of the fixed crush load on the cable 100.
[0057] Referring to FIGs. 1 through 8, the sheath 102 and the plurality of external ribs 104 may be made of same material such as polyvinylchloride, polyethylene (such as High Density Poly Ethylene (HDPE), Medium Density Poly Ethylene, and Low Density Poly Ethylene), polyurethane, thermoplastic rubber/elastomer, thermoplastic chlorinated polyethylene, thermoset polyolefins or combination thereof. Alternatively, the sheath 102 and the plurality of external ribs 104 may be made of different materials. The plurality of external ribs 104 and the plurality of external grooves 106 are one or more of a rectangular shape, rectangular shape with rounded edges, a pointy triangle shape, a curve-type shape or other suitable shape. Further, the plurality of external ribs 104 has a height (first height or second height or both) in a range of 0.1-2.0 millimeters, the plurality of external ribs 104 has a width in a range of 0.4-20 millimeters and the plurality of external grooves 106 has a width in a range of 0.4-20 millimeters. Furthermore, the optical fiber cable 100 has a diameter in a range of 11 to 13 millimeters, wherein the optical fiber cable has a blowing of more than 1100 meters in the duct with an inner diameter of 14 millimeters and an outer diameter of 18 millimeters. The plurality of internal grooves have the depth in the range of 0.1-1.0 millimeter and the width in the range of 1.2-2.5 millimeters.
[0058] The present disclosure provides various advantages over the prior art. The cable of the present disclosure includes the plurality of ribs and the plurality of grooves that reduces mass of the cable. Further, the cable has plurality of internal grooves formed on the inner surface of the sheath that increases free space for optical fibers or ribbons in the cable. The cable has large and irregular surface area that increases drag force of the cable. The increase in drag force enhances blowing performance of the cable. In addition, the plurality of ribs and the plurality of grooves reduces coefficient of friction between the sheath and the duct. Further, the cable has better crushing behaviour due to different sizes of the plurality of ribs that are arranged alternately to each other.
[0059] The cable 100 includes one or more strength members 108. FIG. 9 illustrates the one or more strength members of FIGS. 1 to 8 coated with a coating material. The one or more strength members 108 are embedded in the sheath 102. The one or more strength members 108 may have a circular shape or any other suitable shape. The one or more strength members 108 are coated with the coating material having at least one of an ultraviolet (UV) curable water swellable resin composition (or resin) and a thick layer of ethylene acrylic acid (EAA) to prevent water ingression in the cable 100 as without the coating material, the water may seep through the one or more strength members 108 embedded in the sheath 102.
[0060] During coating process, the thick layer of EAA 202 may be coated on the one or more strength members 108 before embedding in the sheath 102. The EAA provides a good adhesion between the one or more strength members 108 and the sheath 102 to further prevent from water ingression. Alternatively, the UV curable water swellable resin composition 202 is coated on the one or more strength members 108 and cured before embedding in the sheath 102. In case, the resin composition comes in contact with water, it swells and blocks the way for water to avoid penetration in core of the cable 100. Typically, the core includes the plurality of optical fibers. The plurality of optical fibers may incorporated in the core as a plurality of loose tube optical fibers, a plurality of tight buffered optical fibers, a group or stack of optical fiber ribbons or the like., which is enclosed by the sheath 102. The UV curable water swellable resin composition can include, but not limited to, acrylic acid, phenyl bis(2,4,6-trimethylbenzoyl)-phosphine oxide and oxybis(methyl-2,1-ethanediyl) diacrylate.
[0061] In an implementation, the UV curable water swellable resin composition may be applied directly on the one or more strength members 108 or above a thin layer of EAA having a thickness of 25 ? 5 microns . The thin layer of EAA helps to achieve better adhesion of the one or more strength members with material of the sheath. Once, the UV curable water swellable resin composition is applied on the one or more strength members 108, the one or more strength members 108 are passed through one or more UV chambers to cure the UV curable water swellable resin composition.
[0062] The coating 202 may have a thickness, preferably, in a range of 40 microns to 60 microns as a thinner layer of the coating material may lead to water ingression. Also, a sheathing tool has strength member embedding holes that supports the coating thickness upto 50-60 microns. Beyond this, abrasion will occur the will further lead to waste creation. Alternatively, the thickness of the coating may vary. Further, the one or more strength members 108 may be made of fiber reinforced plastic (FRP), aramid reinforced plastic (ARP) or any other suitable material. Once the one or more strength members 108 are embedded in the sheath 102, the cable 100 may pass water penetration test. In a test, -0.1 bar pressure water-head was applied to a 3m cable sample kept for at least 24 hours. In another test, the sample was pre-soaked in a bucket of water to a depth of 100 mm ± 10 mm for 10 min before the test. In yet another test, the cable sample 302 of 3 meters was taken and a watertight seal 304 was applied to allow a 1m (H) of water-head 306 to be applied for 24 hours as shown in FIG. 10.
[0063] It will be apparent to those skilled in the art that other alternatives of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention. While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific aspect, method, and examples herein. The invention should therefore not be limited by the above described alternative, method, and examples, but by all aspects and methods within the scope of the invention. It is intended that the specification and examples be considered as exemplary, with the true scope of the invention being indicated by the claims.
[0064] Conditional language used herein, such as, among others, "can," "may," "might," "may," “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain alternatives include, while other alternatives do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more alternatives or that one or more alternatives necessarily include logic for deciding, with or without other input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular alternative. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list.
[0065] Disjunctive language such as the phrase “at least one of X, Y, Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain alternatives require at least one of X, at least one of Y, or at least one of Z to each be present.
[0066] While the detailed description has shown, described, and pointed out novel features as applied to various alternatives, it can be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the scope of the disclosure. As can be recognized, certain alternatives described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others.