The present disclosure relates to the field of optical fibre cable and, in
particular, relates to an optical fibre cable with elongated strength members and manufacturing method thereof.
BACKGROUND
[0002] Over the last few decades, the need for laying overhead cables has
increased rapidly due to the advancement in optical networks. The overhead cables are laid to reduce load on pipeline resources and reduce cost of laying cables. The overhead cables include optical fiber cables used for aerial applications, thus known as aerial drop optical fiber cables. The aerial drop optical fiber cables are typically used for fiber to the home application. The aerial drop optical fiber cables are compact in structure and has a layer stranded structure.
[0003] The aerial drop optical fiber cables include multiple numbers of tubes
with each tube having multiple number of optical fibers. In addition, the aerial drop optical fiber cables need to have a pre-defined break load in order to be installed aerially complying with the safety standards. So, a proper choice of cable components is very crucial for developing these cables. These cables include strength members which may be embedded inside a sheath of the cables. However, the conventional embedded strength members i.e. dielectric strength members have an elongation at break of greater than 2% which may be dangerous.
[0004] There are a few prior art references which talk about drop cables with
metallic strength members embedded. One such reference WO2019128473A1 discloses a high-density compression-resistant fiber bundle cable for a data

center comprising a micro-bundle fiber provided with a plurality of optical fibers, an aramid layer on an outer side of the optical fiber, a sheath layer coated on the outer portion of the aramid layer, and three non-metallic reinforcing members embedded in the sheath layer. The three non-metallic reinforcing members form a triangle. Another such reference CNl 10824644A discloses an optical fiber bundle self-supporting aerial optical cable which comprises a cable core and an outer sheath for coating the cable core. A metal reinforcing piece is embedded in the outer sheath, and the elongation of the metal reinforcing piece is consistent with that of the outer sheath. Yet another reference CNl 11580233 A discloses an optical fiber cable comprising a cable core and an outer sheath and is characterized in that the cable core is formed by twisting optical fiber bundles. However, the above cited references talk about drop cables with embedded strength members but not of pre-elongation of strength members.
[0005] In light of the above-stated discussion, there exists a need for an optical
fibre cable for aerial application with elongated strength members with pre-defined break load that overcomes the above cited drawbacks of the conventional optical fibre cable.
OBJECT OF THE DISCLOSURE
[0006] A primary object of the present disclosure is to provide an optical fibre
cable for aerial applications.
[0007] Another object of the present disclosure is to provide the optical fiber
cable for aerial application with elongated strength members with pre-defined break load.

[0008] Yet another object of the present disclosure is to provide the optical
fiber cable with strength members that break more safely when an external load is applied.
SUMMARY
[0009] In an aspect, the present disclosure provides an optical fibre cable and
a method to manufacture the optical fiber cable. The optical fibre cable includes one or more tubes, a sheath and one or more strength members. Each of the one or more tubes encloses at least one optical fiber. The sheath surrounds the one or more tubes. The one or more strength members are embedded in the sheath. The one more strength members are in a pre-elongated configuration. The one or more strength members are elongated by 0.02% - 0.1% in the pre-elongated configuration.
STATEMENT OF THE DISCLOSURE
[0010] The present disclosure provides an optical fibre cable and a method to
manufacture the optical fiber cable. The optical fibre cable includes one or more tubes, a sheath and one or more strength members. Each of the one or more tubes encloses at least one optical fiber. The sheath surrounds the one or more tubes. The one or more strength members are embedded in the sheath. The one more strength members are in a pre-elongated configuration. The one or more strength members are elongated by 0.02% - 0.1% in the pre-elongated configuration.

BRIEF DESCRIPTION OF THE FIGURES
[0011] Having thus described the invention in general terms, reference will
now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
[0012] FIG. 1 illustrates an optical fibre cable for aerial applications, in
accordance with an aspect of the present disclosure;
[0013] FIG. 2 illustrates another optical fiber cable for aerial applications, in
accordance with another aspect of the present disclosure; and
[0014] FIG. 3 illustrates yet another optical fiber cable for aerial applications,
in accordance with yet another aspect of the present disclosure.
[0015] It should be noted that the accompanying figures are intended to
present illustrations of exemplary aspects 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
[0016] Reference in this specification to "one aspect" means that a particular
feature, structure, or characteristic described in connection with the aspect is included in at least one aspect of the present technology. The appearance of the phrase "in one aspect" in various places in the specification are not necessarily all referring to the same aspect, nor are separate or alternative aspects mutually exclusive of other aspects. Moreover, various features are described which may be exhibited by some aspects and not by others. Similarly, various requirements are described which may be requirements for some aspects but no other aspects.
[0017] Reference will now be made in detail to selected aspects of the present
disclosure in conjunction with accompanying figures. The aspects described herein are not intended to limit the scope of the disclosure, and the present disclosure should not be construed as limited to the aspects 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 aspects 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.
[0018] Moreover, although the following description contains many specifics
for the purposes of illustration, anyone skilled in the art will appreciate that many variations and/or alterations to said details are within the scope of the present technology. Similarly, although many of the features of the present technology are described in terms of each other, or in conjunction with each other, one skilled in the art will appreciate that many of these features can be provided independently of other features. Accordingly, this description of the

present technology is set forth without any loss of generality to, and without imposing limitations upon, the present technology.
[0019] 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.
[0020] FIG. 1 illustrates an optical fibre cable 100 for aerial applications, in
accordance with an aspect of the present disclosure. FIG. 2 illustrates another optical fiber cable 200 for aerial applications, in accordance with another aspect of the present disclosure. FIG. 3 illustrates yet another optical fiber cable 300 for aerial applications, in accordance with yet another aspect of the present disclosure. The optical fiber cable 100 is used for telecommunication applications and networking applications. The optical fiber cable 100 can be installed aerially and used for fiber to the home applications (FTTH). The optical fiber cable 100 adopts a layer stranded optical cable structure. The layer stranded optical cable structure includes optical fibers enclosed inside loose tubes and a water absorbing or blocking compound filled inside the loose tubes.
[0021] The optical fiber cable 100 is a work safe optical fiber cable. In
addition, the optical fiber cable 100 has a pre-defined breaking load. The pre-defined breaking load is needed in order for the optical fiber cable 100 to be installed aerially and comply with safety standards. The optical fiber cable 100 includes strength members that break more safely when an external load is applied. The optical fiber cable 100 includes elements which have properties different from elements made of conventional materials. The properties of the elements of the optical fiber cable 100 are changed in order for the optical fiber cable 100 to be installed aerially and possess the pre-defined breaking load. The

breaking load is defined as tension steadily applied on an element which is just sufficient to break or rupture the element.
[0022] The optical fiber cable 100 has a reduced diameter suitable for aerial
drop applications. The optical fibre cable 100 includes one or more tubes 104, a sheath 106 and one or more strength members 108. Each of the one or more tubes 104 encloses at least one optical fiber 102. In an aspect of the present disclosure, the optical fiber cable 100 includes a first layer 110. In general, an optical fiber cable includes a plurality of fibers and carries information in the form of data between two places using light technology. The optical fiber cable 100 is a cable used for carrying light over long distances. Furthermore, the optical fiber cable 100 may simply be used to transmit optical signals (which may carry sensor data or communication data).
[0023] The at least one optical fiber 102 extends longitudinally along a length
of the optical fiber cable 100. In an aspect, the optical fiber cable 100 includes a plurality of optical fibers. The at least one optical fiber 102 is a fiber used for transmitting information as light pulses from one end to another. In addition, the at least one optical fiber 102 is a thin strand of glass or plastic capable of transmitting optical signals. Also, the at least one optical fiber 102 is configured to transmit large amounts of information over long distances with relatively low attenuation. Further, the at least one optical fiber 102 includes a core region and a cladding region. The core region is an inner part of an optical fiber and the cladding section is an outer part of the optical fiber. Moreover, the core region is defined by a central longitudinal axis of each of the at least one optical fiber 102. In addition, the cladding region surrounds the core region.
[0024] The core region and the cladding region are formed along the central
longitudinal axis of the at least one optical fiber 102. Moreover, the core region and the cladding region are formed during the manufacturing stage of the at

least one optical fiber 102. The core region has a refractive index which is greater than a refractive index of the cladding region. In an aspect, the core region has a higher refractive index than the cladding region.
[0025] In an aspect of the present disclosure, the at least one optical fiber 102
has a diameter of about 160 - 250 um. In another aspect, the diameter of the at least one optical fiber 102 may vary. In an aspect, the at least one optical fiber 102 is a single mode fiber. In another aspect, the at least one optical fiber 102 is a multimode fiber. In an aspect, the at least one optical fiber 102 is at least one of loose fibers, flat ribbon, corrugated ribbon and Intermittently Bonded Ribbon. In an aspect, the at least one optical fiber 102 is a ribbon such that adjacent optical fibers in the ribbon are intermittently connected along length.
[0026] The optical fiber cable 100 includes the one or more tubes 104. Each
of the one or more tubes 104 encloses the at least one optical fiber 102. In an example, each of the one or more tubes 104 encloses 12 optical fibers. The one or more tubes 104 may enclose any number of optical fibers. In an aspect, the at least one optical fiber 102 in the optical fiber cable 100 is greater than equal to 72. In another aspect, a number of the at least one optical fiber 102 in the optical fiber cable 100 may vary. In an aspect, each of the one or more tubes 104 surrounds the at least one optical fiber 102. The one or more tubes 104 covers the at least one optical fiber 102. The one or more tubes 104 include one of loose tubes, buffer tubes, tight buffered tubes and the like. Each of the one or more tubes 104 is a tube for encapsulating the at least one optical fiber 102. The one or more tubes 104 provide support and protection to the at least one optical fiber 102 against crush, bend and stretch. In addition, the one or more tubes 104 protect the at least one optical fiber 102 and prevent ingression of water inside.

[0027] Further, the one or more tubes 104 provide mechanical isolation,
physical damage protection and identification of each of the at least one optical fiber 102. In an aspect, the one or more tubes 104 provide a single layer core construction.
[0028] In an aspect, the optical fiber cable 100 includes a single tube (as shown
in FIG. 1). In an aspect, the optical fiber cable 100 includes three tubes (as shown in FIG. 2). In another aspect, the optical fiber cable 100 includes eight tubes (as shown in FIG. 3). The one or more tubes 104 are stranded around each other. In an aspect, the stranding is S-Z stranding. The one or more tubes 104 are wound around each other in sections with a first direction of winding in an S-shape alternating with the sections with a second direction of winding in a Z-shape. The first direction is a clockwise direction and the second direction is an anticlockwise direction. The SZ stranding of the one or more tubes 104 is performed in order to maintain a uniform lay length, mid-spanning and achieve higher production speeds as compared to helical stranding. In general, the lay length is a longitudinal distance along the length of the optical fiber cable 100 required for the one or more tubes 104 to go all the way around each other. In addition, the S-Z stranding allows uniform distribution of the stress across the one or more tubes 104. The S-Z stranding may have any number of turns between the S-shape and the Z-shape.
[0029] In an aspect of the present disclosure, the one or more tubes 104 are
made of low smoke zero halogen (LSZH) material. In another aspect of the present disclosure, the one or more tubes 104 may be made of any other suitable material. The cross section of the one or more tubes 104 is circular in shape. In an aspect of the present disclosure, the cross section of the one or more tubes 104 may be of any suitable shape. In an aspect of the present disclosure, the one or more tubes 104 have a uniform structure and dimensions. The one or more tubes 104 have a thickness. In an aspect of the present disclosure, the thickness of one or more tubes 104 is equal. In an aspect of the present

disclosure, the thickness of one or more tubes 104 is about 0.1- 0.25 millimetre. In another aspect of the present disclosure, the thickness of the one or more tubes 104 may vary.
[0030] Furthermore, the one or more tubes 104 have an inner diameter and an
outer diameter. In an aspect of the present disclosure, the inner diameter and the outer diameter of the one or more tubes 104 is fixed. In an aspect of the present disclosure, the inner diameter of the one or more tubes 104 is about 0.9 - 1.35 millimetres. In another aspect of the present disclosure, the inner diameter of the one or more tubes 104 may vary. In an aspect of the present disclosure, the outer diameter of each of the one or more tubes 104 is about 1.1 -1.5 millimetres. In another aspect of the present disclosure, the outer diameter of the one or more tubes 104 may vary.
[0031] The optical fiber cable 100 includes the sheath 106. The sheath 106
encapsulates the one or more tubes 104. In an aspect, the sheath 106 encapsulates one or more layers surrounding the one or more tubes 104 (explained below). In an aspect of the present disclosure, the sheath 106 is made of one of UV proof black medium density polyethylene material and UV proof black high density polyethylene material. In general, medium density polyethylene is a thermoplastic material produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts. In another aspect of the present disclosure, the sheath 106 may be made of any other suitable material. The sheath 106 protects the optical fiber cable 100 from harsh environment and harmful UV rays. In addition, the sheath 106 has the inherent ability to resist crushes, kinks and tensile stress. In an aspect of the present disclosure, the sheath 106 has a thickness of about 1.2 - 1.8 millimetre^_In another aspect of the present disclosure, the sheath 106 may have any suitable thickness.
[0032] The optical fiber cable 100 includes the one or more strength members
108. The one or more strength members 108 are embedded in the sheath 106.

In an aspect, the one or more strength members 108 lies substantially along a longitudinal axis of the optical fiber cable 100. In another aspect, the one or more strength members 108 may not lie along the longitudinal axis. In addition, the one or more strength members 108 provide tensile strength and stiffness to the optical fiber cable 100.
[0033] The one more strength members 108 are in a pre-elongated
configuration. The one or more strength members 108 are elongated by 0.02% - 0.1% in the pre-elongated configuration. The pre-elongation is optimized so that the one or more strength members 108 are in a safe elongated/stretched state and can achieve the elongation at break more rapidly during an external break load. The pre-elongated strength members break more safely in-case an external load is applied. In an aspect, each of the one or more strength members 108 is stranded metallic wires. In an aspect, the stranded metallic wires are made of steel. In an aspect, the metallic wires are made of brass plated steel wires.
[0034] In an aspect, the one or more strength members 108 are embedded at a
tension of 1.5-8 kgf In another aspect, the one or more strength members 108 may be embedded at any suitable value of tension. The tension value of 1.5 -8 kgf helps achieve optimized pre-elongation in the embedded one or more strength members 108.
[0035] In an aspect, the one or more strength members 108 has an elongation
at break less than or equal to 2%. The elongation at break is a measurement of how much a material can be stretched before it breaks. Elongation at break is also called "fracture strain" or "tensile elongation at break". In addition, elongation at break is the percentage increase in length that material will achieve before breaking and a measurement of an amount a material will plastically and elastically deform up to fracture. The material's final length is compared with its original length to determine the percent elongation.

[0036] In an aspect of the present disclosure, the one or more strength
members 108 have an average surface roughness of lum to 5um. The average surface roughness in the range of lum to 5um is selected so that the adhesion between a material of the one or more strength members 108 and the sheath 106 material is good. Surface roughness is defined as irregularities which are inherent in the production process and quantified by deviations in direction of a normal vector of a real surface from its ideal form. If the deviations are large, the surface is rough and if the deviations are small, the surface is smooth.
[0037] Further, the one or more strength members 108 are characterized by a
diameter. In an aspect, the one or more strength members 108 have a diameter of about 0.3 - 0.7 mm. In another aspect, the diameter of the one or more strength members 108 may vary. In an aspect, each of the one or more strength members 108 is two or more stranded metal wires. In another aspect, number of metallic wires in the one or more strength members 108 are 3. In yet another aspect, the number of metallic wires in the one or more strength members 108 may be more or less than 3. In an aspect, the number of strength members 108 are two. In another aspect, the number of strength members 108 may vary.
[0038] The optical fiber cable 100 includes the one or more layers. In an
aspect, the one or more layers include the first layer 110. However, the one or more layers may include more number of layers. In an aspect, the one or more layers include a single buffer tube that is unitube surrounding the at least one optical fiber 102. In an aspect, the first layer 110 is made of binder yarns. The binder yarn is used for binding a core of the optical fiber cable 100. In an aspect of the present disclosure, the binder yarn is an aramid yarn. In another aspect of the present disclosure, the binder yarn is made of any other suitable material. In an aspect, the optical fiber cable 100 may include layers such as Water Blocking Tape, Water Swellable Yarns and fire retardant tape. In another

aspect, the optical fiber cable 100 may include more layers in addition or in place of the first layer 110.
[0039] In an aspect, the optical fiber cable 100 includes a water blocking gel
112. The water blocking gel 112 is filled inside the one or more tubes 104. In an aspect of the present disclosure, the water blocking gel 112 is a thixotropic gel. The thixotropic gel prevents ingression of water inside each of the one or more tubes 104 and provides a cushioning to the optical fibers. In an aspect, the one or more tubes 104 may be loose tubes, buffer tubes and tight buffered tubes.
[0040] In an aspect, the optical fiber cable 100 may or may not include a
ripcord. In an aspect, the ripcord is disposed inside the sheath 106. The ripcord may lie substantially along the longitudinal axis of the optical fiber cable 100. The ripcord enables tearing of the sheath 106 to facilitate access to the one or more tubes 104. In an aspect of the present disclosure, the ripcord may be made of a polyester material. In another aspect of the present disclosure, the ripcord may be made of any other suitable material. The ripcord has a circular cross-section.
[0041] The optical fiber cable 100 may have a suitable diameter. In an aspect
of the present disclosure, the diameter of the optical fiber cable 100 is about 5 -8 millimetres^ In an aspect, the optical fiber cable 100 has a tensile break load of less than 2100 N. The aerial drop cables exert force on poles on which the drop cables are clamped whenever any external load is applied on the drop cable. This leads to poles being broken and damaged which increases maintenance cost. The break load of less than 2100 N ensures that the poles do not get damaged.

[0042] The above mentioned information applies for the optical fiber cable
200 and the optical fiber cable 300.
[0043] The optical fiber cables 100, 200, 300 are manufactured according to a
method. The method includes a set of steps. The set of steps include a first step and a second step. The first step includes paying-off the one or more tubes 104 to form a core of the optical fiber cables 100, 200, 300. The one or more tubes 104 enclose at least one optical fiber 102. The second step includes extruding the sheath 106. The sheath 106 surrounds the one or more tubes 104. The one or more strength members 108 are embedded in the sheath 106 during extrusion. The one more strength members 108 are embedded under a tension of at least 1.5 kgf.
[0044] The foregoing descriptions of pre-defined aspects 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 aspects 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 aspects 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.

CLAIMS
We Claim:

1. An optical fiber cable (100, 200, 300) comprising:
one or more tubes (104), wherein the one or more tubes (100, 200, 300) encloses at least one optical fiber (102);
a sheath (106) surrounding the one or more tubes (104); and
one or more strength members (108) embedded in the sheath (106), wherein the one more strength members (108) are in a pre-elongated configuration, wherein the one or more strength members (108) are elongated by 0.02% - 0.1% in the pre-elongated configuration.
2. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the optical fiber cable (100, 200, 300) has a tensile break load of less than 2100N.
3. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein each of the one or more strength members (108) is two or more stranded metal wires.
4. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the one or more strength members (108) are embedded at a tension of 1.5-8 kgf

5. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the one or more strength members (108) has an elongation at break less than or equal to 2%.
6. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the one or more strength members (108) has an average surface roughness of lum to 5um.
7. A method of manufacturing an optical fiber cable (100, 200, 300) comprising:
paying-off one or more tubes (104) to form core of the optical fiber cable (100, 200, 300), wherein the one or more tubes (104) encloses at least one optical fiber (102);
extruding a sheath (106) surrounding the one or more tubes (104),
wherein one or more strength members (108) are embedded in the sheath (106) during extrusion, wherein the one more strength members (108) are embedded under a tension of greater than or equal to 1.5 kgfi.
8. The method as claimed in claim 7, wherein the one or more strength
members (108) are elongated by 0.02% - 0.1% under the tension.

9. The method as claimed in claim 7, wherein the optical fiber cable (100, 200, 300) has a tensile break load of less than 2100N.
10. The method as claimed in claim 7, wherein the one or more strength members (108) are stranded metal wires.
11. The method as claimed in claim 7, wherein the one or more strength members (108) are embedded at a tension of less than 8kgf
12. The method as claimed in claim 7, wherein the one or more strength members (108) has an elongation at break less than or equal to 2%.
13. The method as claimed in claim 7, wherein the one or more strength members (108) has an average surface roughness of lum to 5um.