The present disclosure relates to the field of optical fibre cable and, in
particular, relates to an optical fibre cable with multi layered tubes.
BACKGROUND
[0002] With the advancement of science and technology, various modern
technologies are being employed for communication purposes. One of the most important modern communication technologies is the optical fiber communication technology using a variety of optical fiber cables. These optical fiber cables include buffer tubes or loose tube for storing optical fibers. In some cables, there may be multiple layers of buffer tubes.
[0003] However, in the multi-layered buffer tube design, the buffer tubes
positioned in the innermost layer of the multiple layers are subject to higher stresses as compared to the buffer tubes in the outermost layers. This leads to crushing of the buffer tubes in the innermost layer. Currently, material used for the buffer tubes in the inner layers as well as the outer layers has a low young's modulus. Also, different buffer tube materials are used in inner layers and outer layers which lead to overdesigning of the optical fiber cables.
[0004] One such prior art which provides a solution is EP0833177A1. The
prior art discloses a cable with enhanced flexibility. The cable includes materials with a lower modulus which are positioned closer to the outer periphery of the cable than the materials with a higher modulus to enhance flexibility. This means that the sheath has a lower modulus than buffer tubes and the buffer tubes have lower modulus than CSM. However, there is no

mention of different young's modulus of buffer tubes in different layers made of same material.
[0005] In light of the above-stated discussion, there exists a need for an
optical fibre cable with buffer tubes of different modulus 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 with multiple layers of tubes.
[0007] Another object of the present disclosure is to provide the optical fiber
cable with better crush resistant tubes in inner layer.
[0008] Yet another object of the present disclosure is to avoid overdesigning
of the optical fiber cable by using tubes of same material.
SUMMARY
[0009] In an aspect, the present disclosure provides an optical fibre cable.
The optical fibre cable includes a plurality of tubes and a sheath. The sheath encapsulates the plurality of tubes. Each of the plurality of tubes has a plurality of optical fibers. At least one tube of the plurality of tubes has young's modulus that is different from other tubes. Each of the plurality of tubes is made of same base material. The plurality of tubes is arranged in multiple layers with each layer having tubes with different young's modulus.

STATEMENT OF THE DISCLOSURE
[0010] The present disclosure provides an optical fibre cable. The optical
fibre cable includes a plurality of tubes and a sheath. The sheath encapsulates the plurality of tubes. Each of the plurality of tubes has a plurality of optical fibers. At least one tube of the plurality of tubes has young's modulus that is different from other tubes. Each of the plurality of tubes has a same base material. The plurality of tubes is arranged in multiple layers with each layer having tubes with different young's modulus.
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 with multi-layered tube
design, in accordance with an aspect of the present disclosure;
[0013] FIG. 2 illustrates another optical fiber cable with the multi-layered
tube design, in accordance with another aspect of the present disclosure; and
[0014] FIG. 3 illustrates yet another optical fiber cable with the multi-
layered tube design, 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 cablelOO with multi-layered tube
design, in accordance with an aspect of the present disclosure. FIG. 2 illustrates another optical fiber cable 200 with the multi-layered tube design, in accordance with another aspect of the present disclosure. FIG. 3 illustrates yet another optical fiber cable 300 with the multi-layered tube design, in accordance with yet another aspect of the present disclosure. The optical fiber cable 100 is used for telecommunication applications, networking applications requiring a small and flexible construction. The optical fiber cable 100 can be installed in ducts, riser shafts, conduits, plenums and computer room floors.
[0021] The optical fiber cable 100 is a high fiber count optical fiber cable.
In addition, the optical fiber cable 100 is a multi-layered tube design cable. The multi-layered tube design refers to multiple layers of tubes positioned inside a core of the optical fiber cable 100. The optical fiber cable 100 includes a plurality of tubes 104 and a sheath 114. Each of the plurality of tubes 104 encloses a plurality of optical fibers 106. The sheath 114 encapsulates the plurality of tubes 104.
[0022] In an aspect, the optical fiber cable 100 includes a central strength
member 102. The central strength member 102 lies substantially along a longitudinal axis of the optical fiber cable 100. In an aspect of the present

disclosure, the central strength member 102 is made of fiber reinforced plastic. The fiber reinforced plastic is a composite material having a polymer matrix reinforced with glass fibers. In an example, the fiber reinforced plastics includes but may not be limited to glass fibers, carbon fibers, aramid fibers, basalt fibers and the like. In another aspect of the present disclosure, the central strength member 102 is made of any other suitable material. In an aspect of the present disclosure, the central strength member 102 may be coated with a layer of polyethylene. In another aspect of the present disclosure, the central strength member may be coated with any other suitable material. In yet another aspect of the present disclosure, the central strength member 102 may not be coated. The central strength member 102 has a circular cross-section.
[0023] The central strength member 102 provides physical strength to the
optical fiber cable 100 and resists over bending of the optical fiber cable 100. In addition, the central strength member 102 provides tensile strength to the optical fiber cable 100. The tensile strength corresponds to a resistance shown by the optical fiber cable 100 against longitudinal loads. The central strength member 102 is characterized by a diameter measured along the cross section. In an aspect of the present disclosure, the diameter of the central strength member 102 is about 1.5-6millimetres. In another aspect of the present disclosure, the diameter of the central strength member 102 may vary.
[0024] In an aspect, the plurality of tubes 104 includes a first plurality of
tubes and a second plurality of tubes. In an aspect, the first plurality of tubes of the plurality of tubes 104 is stranded around the central strength member 102 in a repetitive clockwise and anti-clockwise direction. In an aspect, the second plurality of tubes of the plurality of tubes 104 is stranded around the first plurality of tubes.

[0025] In an aspect, the optical fiber cable 100 includes a first layer of tubes
and a second layer of tubes (as shown in FIG. 1). In another aspect, the optical fiber cable 100 includes a first layer of tubes, a second layer of tubes and a third layer of tubes (as shown in FIG. 2 and FIG. 3). The first layer of tubes, the second layer of tubes and the third layer of tubes may be stranded in an S-Z fashion. The first layer of tubes wound around the central strength member 102 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 plurality of 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 central strength member 102 required for the plurality of tubes 104 to go all the way around the central strength member 102. In addition, the S-Z stranding allows uniform distribution of the stress across the plurality of tubes 104. The S-Z stranding may have any number of turns between the S-shape and the Z-shape.
[0026] Further, at least one tube of the plurality of tubes 104 has young's
modulus that is different from other tubes. In an aspect of the present disclosure, at least one tube of the plurality of tubes 104 has a young's modulus that is at least 30% more than young's modulus of the other tubes. In another aspect of the present disclosure, at least one tube of the plurality of tubes 104 has a young's modulus that is at least 50% more than young's modulus of the other tubes. The optical fiber cable 100 includes the plurality of tubes 104 of different young's modulus. The young's modulus (E) is a property of the material that tells how easily it can stretch and deform. The young's modulus (E) is defined as a ratio of tensile stress (o) to tensile strain (s), where stress is the amount of force applied per unit area (o = F/A) and strain is extension per unit length (s = dl/1).

[0027] In an aspect of the present disclosure, each of the plurality of tubes
104 is made of a first material. In an aspect of the present disclosure, the first material includes polypropylene, polybutylene terephthalate or a mixture of polycarbonate and polybutylene terephthalate. In another aspect of the present disclosure, the first material may be any other suitable material. In an aspect of the present disclosure, the plurality of tubes 104 is arranged in one or more inner layers and one or more outer layers. The tubes in one or more inner layers have an inner young's modulus. Each of the plurality of tubes 104 in the one or more outer layers has an outer young's modulus such that the inner young's modulus is greater than the outer young's modulus of each of the plurality of tubes 104 in the one or more outer layers.
[0028] The optical fiber cablelOO includes tubes of same raw material but
different grades such that the plurality of tubes 104 in the one or more inner layers have a higher young's modulus as compared to the plurality of tubes 104 in the one or more outer layers. The plurality of tubes 104 in the one or more inner layers and the one or more outer layers although made up of same base plastic material have different mechanical properties.
[0029] In an aspect of the present disclosure, the plurality of tubes 104 is
arranged in an innermost layer 108 and an outermost layer 110 (as shown in FIG. 1). The young's modulus of the innermost layer 108 is greater than the young's modulus of the outermost layer 110. In another aspect, the plurality of tubes 104 is arranged in the innermost layer 108, at least one intermediate layer 120 and the outermost layer 110 (as shown in FIG. 2and FIG. 3). In an aspect, the young's modulus of the innermost layer 108 is greater than the young's modulus of the intermediate layer 120 and outermost layerllO. In an aspect, the young's modulus of the at least one intermediate layer 120 is greater or equal to the young's modulus of the outermost layer 110.

[0030] In an aspect of the present disclosure, the plurality of tubes 110 is
arranged such that the young's modulus of the plurality of tubes 104 radially decreases from centre of the optical fiber cable 100 towards the sheath 114 of the optical fiber cable 100. In an aspect of the present disclosure, the young's modulus of the innermost layer 108 is greater than 2000 MPa. In an aspect of the present disclosure, the young's modulus of the at least one intermediate layer 120 is greater than 1200 MPa. In an aspect of the present disclosure, the young's modulus of the outermost layer 110 is greater than 900 MPa.
[0031] The cross section of each of the plurality of tubes 104 is circular in
shape. In an aspect of the present disclosure, the cross section of each of the plurality of tubes 104 may be of any suitable shape. In an aspect of the present disclosure, each of the plurality of tubes 104 has a uniform structure and dimensions. In an aspect of the present disclosure, the innermost layer 108 includes 9 tubes. In another aspect of the present disclosure, the number of tubes inside the innermost layer 108 may vary. In an aspect of the present disclosure, the at least one intermediate layer 120 includes 12 tubes. In another aspect of the present disclosure, the number of tubes inside the at least one intermediate layer 120 may vary. In an aspect of the present disclosure, the outermost layer 110 includes 15 tubes. In another aspect of the present disclosure, the number of tubes inside the outermost layer 110 may vary.
[0032] Each of the plurality of tubes 104 has a thickness. In an aspect of the
present disclosure, the thickness of each of the plurality of tubes 104 is equal. In an aspect of the present disclosure, the thickness of each of the plurality of tubes 104 is about 0.15-0.8millimetre. In another aspect of the present disclosure, the thickness of each of the plurality of tubes 104 may vary.
[0033] Furthermore, each of the plurality of tubes 104 has an inner diameter
and an outer diameter. In an aspect of the present disclosure, the inner

diameter and the outer diameter of each of the plurality of tubes 104 is fixed. In an aspect of the present disclosure, the inner diameter of each of the plurality of tubes 104 is about 0.9 to 3 mm millimetres. In another aspect of the present disclosure, the inner diameter of each of the plurality of tubes 104 may vary. In an aspect of the present disclosure, the outer diameter of each of the plurality of tubes 104 is about 1.1 to 4.5 millimetres. In another aspect of the present disclosure, the outer diameter of each of the plurality of tubes 104 may vary.
[0034] Going further, each of the plurality of tubes 104 encloses a plurality
of optical fibers 106. In an aspect of the present disclosure, each of the plurality of tubes 104 encloses 12 optical fibers. Each of the plurality of tubes 104 is a tube for encapsulating the plurality of optical fibers 106. The plurality of tubes 104 provides support and protection to each of the plurality of optical fibers 106 against crush, bend and stretch. In addition, the plurality of tubes 104 protects the plurality of optical fibers 106. Further, each of the plurality of tubes 104 provides mechanical isolation, physical damage protection and identification of each of the plurality of optical fibers 106.
[0035] In an aspect of the present disclosure, each of the plurality of tubes
104 is filled with a gel. In an aspect of the present disclosure, the gel is a thixotropic gel. The thixotropic gel prevents ingression of water inside each of the plurality of tubes 104. In another aspect, each of the plurality of tubes 104 includes water swellable yarns. The water swellable yarns prevent ingression of water inside the plurality of tubes 104. In an aspect, the plurality of tubes 104 may be loose tubes, buffer tubes and tight buffered tubes.
[0036] In an aspect, the plurality of optical fibers 106 may be in the form of
loose fibers (as shown in FIG. 1, FIG. 2 and FIG. 3). In another aspect, the plurality of optical fibers 106 may be in the form of flat ribbons. In yet

another aspect, the plurality of optical fibers 106 may be in the form of rollable ribbons. In yet another aspect, the plurality of optical fibers 106 may be in the form of intermittently bonded ribbon. Further, each of the plurality of optical fibers 106 is a fiber used for transmitting information as light pulses from one end to another. In addition, each of the plurality of optical fibers 106 is a thin strand of glass capable of transmitting optical signals. Also, each of the plurality of optical fibers 106 is configured to transmit large amounts of information over long distances with relatively low attenuation. Further, each of the plurality of optical fibers 106 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 plurality of optical fibers 106. In addition, the cladding region surrounds the core region.
[0037] Each of the plurality of optical fibers 106 has a diameter of about
160um to 250.um In an aspect of the present disclosure, the diameter of each of the plurality of optical fibers 106 may vary. In an aspect of the present disclosure, each of the plurality of optical fibers 106 is a single mode fiber. In another aspect of the present disclosure, each of the plurality of optical fibers 106 is a multimode fiber.
[0038] In an aspect of the present disclosure, a number of the plurality of
optical fibers 106 in each of the plurality of tubes 104 is 12. In an aspect of the present disclosure, a number of the plurality of optical fibers 106 in each of the plurality of tubes 104 is 24. In an aspect of the present disclosure, a total number of the plurality of optical fibers 106 in the innermost layer 108 is 108 (9*12 = 108), when the number of tubes is 9. In another aspect of the present disclosure, the number of optical fibers and the number of tubes in the innermost layer 108 may vary. In an aspect of the present disclosure, a total number of the plurality of optical fibers 106 in the at least one intermediate

layer 120 is 144 (12*12 = 144), when the number of tubes is 12. In another aspect of the present disclosure, the number of optical fibers and the number of tubes in the at least one intermediate layer 120 may vary. In an aspect of the present disclosure, a total number of the plurality of optical fibers 106 in the outermost layer 110 is 180 (15*12 = 180), when the number of tubes is 15. In another aspect of the present disclosure, the number of optical fibers and the number of tubes in the outermost layer 108 may vary.
[0039] In an aspect, the optical fiber cable 100 has one or more layers of
binder yarns, strength yarns, WSY (water swellable yarns), WBT (water blocking tape), fire retardant tape, metal tape, cushioning layer and the like in between layers of the plurality of tubes (104) or in between the plurality of tubes (104) and the sheath (114). In an aspect, the optical fiber cable 100 includes a binding layer 112. The binding layer 112 is made of binder yarns. The binder yarn is used for binding of the core of the optical fiber cable 100. In an aspect of the present disclosure, the binder yam is a normal binder yam. In another aspect of the present disclosure, the binder yarn is a low shrinkage binder yam. In yet another aspect of the present disclosure, the binder yarn is a super low shrinkage binder yam. 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. The optical fiber cable 100 may include more layers in addition or in place of the binding layer 112.
[0040] The optical fiber cable 100 includes the sheath 114. The sheath 114
encapsulates the plurality of tubes 104. In an aspect, the sheath 114 encapsulates the one or more layers surrounding the plurality of tubes 104. In an aspect of the present disclosure, the sheath 114 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 114 may be made of any other suitable material. The sheath 114 protects the optical fiber cable 100 from harsh environment and harmful UV rays. In addition, the sheath 114 has the inherent ability to resist crushes, kinks and tensile stress. In an aspect of the present disclosure, the sheath 114 has a thickness of about 0.5 to 2.5 millimetre. In another aspect of the present disclosure, the sheath 114 may have any suitable thickness.
[0041] In an aspect, the optical fiber cable 100 includes a plurality of water
swellable yarns 116. The plurality of water swellable yarns 116 prevents ingression of water inside the core of the optical fiber cable 100. In addition, the water swellable yarns 116 prevent water penetration along the length of the optical fiber cable 100. The plurality of water swellable yarns 116 may be helically disposed around the central strength member 102. In an aspect of the present disclosure, the number of the plurality of water swellable yarns 116 is 3. In another aspect of the present disclosure, the number of the plurality of water swellable yarns 116 may vary.
[0042] In an aspect, the optical fiber cable 100 includes the ripcord 118. In
an aspect, the ripcord 118 is disposed inside the binding layer 120. The ripcord 118 lies substantially along the longitudinal axis of the optical fiber cable 100. The ripcord 118 enables tearing of the sheath 114 to facilitate access to the plurality of tubes 104. In an aspect of the present disclosure, the ripcord 118 is made of a polyester material. In another aspect of the present disclosure, the ripcord 118 is made of any other suitable material. The ripcord 118 has a circular cross-section. In an aspect of the present disclosure, the number of ripcords in the optical fiber cable 100 is 1. In another aspect of the present disclosure, the number of ripcords may vary.
[0043] The optical fiber cable 100 may have a suitable diameter. In an
embodiment of the present disclosure, the diameter of the optical fiber cable

100 is about 8 to 25 millimeters. The optical fiber cable 100 has better crush resistant tubes in the innermost layer 108. The use of same material with different grades helps avoid overdesigning of the optical fiber cable 100. The optical fiber cable 100 has reduced cost.
[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

What is claimed is:
1. An optical fiber cable (100, 200, 300) comprising:
a plurality of tubes (104), wherein each of the plurality of tubes (104) has a plurality of optical fibers (106), wherein at least one tube of the plurality of tubes (104) has young's modulus that is different from other tubes; and
a sheath (114) encapsulating the plurality of tubes (104).
2. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein each of the plurality of tubes (104) is made of a first material.
3. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein at least one tube of the plurality of tubes (104) has a young's modulus that is at least 30% more than young's modulus of the other tubes.
4. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the plurality of tubes (104) are arranged in one or more inner layers and one or more outer layers, wherein the one or more inner layers has an inner young's modulus, wherein each of the plurality of tubes (104) in the one or more outer layers has an outer young's modulus such that the inner young's modulus of inner layer tubes is greater than the outer young's modulus of each of the plurality of tubes (104) in the one or more outer layers.
5. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the plurality of tubes (104) is arranged in an innermost layer (108) and an outermost

layer (110), wherein young's modulus of the innermost layer (108) is greater than young's modulus of the outermost layer (110).
6. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the plurality of tubes (104) is arranged in an innermost layer (108), at least one intermediate layer (120) and an outermost layer (110), wherein young's modulus of the innermost layer (108) tubes is greater than young's modulus of the intermediate layer (12) and outermost layer (110) tubes, wherein young's modulus of the at least one intermediate layer (120) tubes is greater or equal to than young's modulus of the outermost layer (110) tubes.
7. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the plurality of tubes (110) is arranged such that young's modulus of the plurality of tubes (104) radially decreases from centre of the optical fiber cable (100, 200, 300) towards the sheath (114) of the optical fiber cable (100, 200, 300).
8. The optical fiber cable (100, 200, 300) as claimed in claim 1, further comprising a central strength member (102), wherein a first plurality of tubes of the plurality of tubes (104) is stranded around the central strength member (102) in a repetitive clockwise and anti-clockwise direction.
9. The optical fiber cable (100, 200, 300) as claimed in claim 1, further comprising a central strength member (102), wherein a first plurality of tubes of the plurality of tubes (104) is stranded around the central strength member (102) in a repetitive clockwise and anti-clockwise direction, wherein a second plurality of tubes of the plurality of tubes (104) is stranded around the first plurality of tubes.
10. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein the optical fiber cable (100, 200, 300) has one or more layers of binder yarns, strength yarns, WSY (water swellable yarns), WBT (water blocking tape), fire retardant

tape, metal tape, cushioning layer in between layers of the plurality of tubes (104) or in between the plurality of tubes (104) and the sheath (114).
11. The optical fiber cable (100, 200, 300) as claimed in claim 1, wherein at least one tube of the plurality of tubes (104) has a young's modulus that is at least 50% more than young's modulus of the other tubes.