The present invention relates to the field of optical fiber, and more
particularly to an optical fiber cable with specifically designed strength members enhancing the preferential bending.
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 optical fiber communication technology using a variety of optical fiber cables. In addition, the optical fiber cables are widely used for communication to meet the increasing demands. Further, installation of the optical fiber cables at a rapid pace becomes essential. The optical fiber cables consist of a number of optical fibers. The optical fibers may or may not be enclosed inside buffer tubes. The number of buffer tubes or optical fibers constitutes a core of the optical fiber cable. In addition, the core may be surrounded by one or more layers surrounded by a sheath. The sheath protects the optical fiber cable against any mechanical breakage. Further, the sheath may be embedded with strength members. The strength members provide mechanical stability to the optical fiber cable.
[0003] Some of the optical fiber cables employ dissimilar embedded strength
members. The dissimilar embedded strength members are needed to provide the required mechanical tensile strength to the fiber as well as to maintain the lower breaking load of the cable. However, the dissimilar strength members embedded in the jacket are not good to provide uniform bending stiffness.

[0004] There are a few patent applications/patents that provide cables with
multiple embedded strength members. In an example, a patent application JP2012203199A discloses a cable consisting of a centrally located plastic tube containing optical fibers and tensile members embedded in the jacket of the cable. In another example, a patent US6546176B2 discloses an optical fiber cable which includes a buffer tube containing at least one optical fiber and reinforced by at least two substantially radially incompressible longitudinal strength members. In yet another example, a patent US7330621B2 discloses optical fiber assemblies with one or more strength members embedded in the sheath. However, the above stated examples do not talk about dissimilar strength members with large bending capacity.
[0005] In the light of above stated discussion, there is a need of optical fiber
cable having specific embedded strength members.
OBJECT OF THE DISCLOSURE
[0006] A primary objective of the present disclosure is to provide a flexible
optical fiber with the plurality of strength members.
[0007] Another objective of the present disclosure is to lower the cable
bending radius without disturbing the optical quality of the fiber as well as the cable.
[0008] Another objective of the present disclosure is to provide easy coiling
and handling of the cable resulting in easy and reduced installation time of the cable.

[0009] Another objective of the present disclosure is to maximize the life of
the cable and the fiber with low breaking load of the cable.
SUMMARY
[0010] In an aspect, the present disclosure provides an optical fiber cable.
The optical fiber cable includes at least one optical fiber unit, a sheath and a plurality of strength members. The at least one optical fiber unit has atleast one fiber. The sheath encapsulates the at least one optical fiber unit. The plurality of strength members are embedded in the sheath. The optical fiber cable has a preferential bending ratio between 1-2.
STATEMENT
[0011] The present disclosure provides an optical fiber cable. The optical
fiber cable includes at least one optical fiber unit, a sheath and a plurality of strength members. The at least one optical fiber unit has atleast one fiber. The sheath encapsulates the at least one optical fiber unit. The plurality of strength members are embedded in the sheath. The optical fiber cable has a preferential bending ratio between 1-2.
BRIEF DESCRIPTION OF THE FIGURES
[0012] 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:

[0013] FIG. 1 illustrates a cross sectional view of an exemplary optical fiber
cable with dissimilar plurality of strength members, in accordance with various aspects of the present disclosure.
[0014] 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
[0015] In the following description, for purposes of explanation, numerous
specific details are set forth in order to provide a thorough understanding of the present technology. It will be apparent, however, to one skilled in the art that the present technology can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form only in order to avoid obscuring the present technology.
[0016] Reference in this specification to "one aspect" or "an 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 not other aspects.
[0017] 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. Although the following description provides an optical fiber cable, the shown cable construction method can be applied to any cable with loose tube and sheath.

[0018] 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.
[0019] FIG.l illustrates a cross sectional view of an exemplary optical fiber
cable 100, in accordance with various aspects of the present disclosure. The optical fiber cable 100 is used for telecommunication applications, data centers and the like. The optical fiber cable 100 includes atleast one optical fiber unit 102, atleast one fiber 104, a tight buffer layer 106 and a sheath 108. In addition, the optical fiber cable 100 includes a plurality of strength members 110a, 110b and 110c, atleast one water swellable element 112 and atleast one filling strength member (SM) 114.
[0020] In general, an optical fiber cable includes one or more fibers and carries
information in the form of data between two places using light technology. In an aspect, the optical fiber cable 100 is an all-dielectric communication cable. 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).
[0021] The optical fiber cable 100 includes the atleast one optical fiber unit
102. The atleast one optical fiber unit 102 includes the atleast one fiber 104. In addition, the atleast one optical fiber unit 102 includes the tight buffer layer 106. In an aspect, the atleast one fiber 104 extends longitudinally along a length of the optical fiber cable 100. The atleast one fiber 104 is a fiber used for transmitting information at light pulses from one end to another. Further, the atleast one fiber 104 is configured to transmit large amounts of information over long distances with relatively low attenuation. Furthermore, the atleast

one fiber 104 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 the atleast one fiber 104. In addition, the cladding region surrounds the core region.
[0022] The core region and the cladding region are formed along the central
longitudinal axis of each of the atleast one fiber 104. Moreover, the core region and the cladding region are formed during the manufacturing stage of the atleast one fiber 104. 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.
[0023] The optical fiber cable 100 includes the sheath 108. In an aspect, the
sheath 108 may be referred to as an outer jacket. The sheath 108 surrounds the atleast one optical fiber unit 102. In an aspect, the sheath 108 is a high density polyethylene (HDPE) jacket or any other material.
[0024] In an aspect, the thickness of the sheath 108 may vary. In an aspect,
the sheath 108 is black in color. In another aspect, the sheath 108 may be of any color. The sheath 108 layer interacts directly with ambient environment. In addition, the outer sheath 108 is a sheathing layer. The sheath 108 protects the optical fiber cable 100 against crush, bend and tensile stress along the length of the optical fiber cable 100.
[0025] The sheath 108 includes the plurality of strength members 110a, 110b
and 110c. The plurality of strength members 110a, 110b and 110c are dissimilar or similar in sizes. In an aspect of the present disclosure, the two

strength members 110a and 110b are 0.7mm in thickness or diameters. In addition, the third strength member 110c is 0.5mm in thickness or diameter.
[0026] In an aspect of the present disclosure, each of the plurality of strength
members 110a, 110b, 110c has a diameter between 0.4mm-0.8mm. In an aspect, the ratio of diameters of any two strength members of the plurality of strength members 110a, 110b, 110c is equals to or less than 2.
[0027] In an aspect, the placement and the size of the plurality of strength
members 110a, 110b and 110c affects the bending stiffness of the optical fiber cable 100. The bending stiffness is a measure of resistance of the optical fiber cable 100 to bend in a plane perpendicular to the longitudinal axis. The placement of the mentioned bending plane can be a set of combination based on the design of the cable which changes the bending stiffness value for each combination. The bending stiffness is calculated by referring a method E17B set forth by IEC 60794-1-2.
[0028] In general, the preferential bending ratio is the ratio of the maximum
and minimum value from the set of the calculated bending stiffness. The preferential bending ratio is the maximum range to which a cable may be bent without damaging the quality of fiber. .
[0029] In an aspect, the preferential bending ratio is less than 2 to achieve a
flexible and long life optical fiber cable 100. In another aspect, the preferential bending ratio may be of any other value. The preferential bending ratio equals to or below than 2 is calculated for the plurality of strength members 110a, 110b and 110c. The diameter within 0.4-0.8mm of the plurality of strength members 110a, 110b and 110c helps achieving a strain equal to or less than 20% of the fiber test proof strain at long-term load. In addition, the diameter

within 0.4-0.8mm helps achieving a strain equal to or less than 60% of the fiber proof test at maximum load.
[0030] The fiber proof test is a technique to ensure the minimum strength of
an optical fiber. In the fiber proof test, a predetermined load is applied on the fiber by tensile loading. The fiber breaks at weak points and the weak points are eliminated from the fiber. The fiber proof test guarantees a minimum strength level of the fiber for lifetime.
[0031] In an aspect, the cabled fiber strain is equal to or less than 20% of the
fiber proof test strain at long-term load. In addition, the cabled fiber strain is equal to or less than 60% of the fiber proof test strain at maximum load. Further, the life of the optical fiber cable 100 is more than 25 years when the optical fiber cable 100 falls under the above mentioned category. However, the life of the optical fiber cable 100 deteriorates when the optical fiber cable 100 does not fall under the category.
[0032] In general, the long-term load refers to the minimum load that acts
upon the cable after the cable is installed. The maximum load is the maximum load developed on the optical fiber cable 100 due to external forces after the optical fiber cable 100 is installed and during the installation of the optical fiber cable 100.
[0033] In an aspect, plurality of strength members 110a, 110b, 110c with the
dissimilar or similar diameters within 0.4-0.8mm helps in maintaining the breaking load of the optical fiber cable 100 between 1350-2000N. In another aspect, the breaking load of the optical fiber cable 100 may be of any other value. The breaking load of 1350-2000N is not achieved when the plurality of strength members 110a, 110b, 110c have diameters of any other value than the

above mentioned values (110a and 110b diameter). In an example, the plurality of strength members 110a, 110b, 110c may be aramid reinforcement plastic (ARP), fiber- reinforcement plastic (FRP) and the like.
[0034] In an aspect, the plurality of strength members 110a, 110b, 110c are
placed at 120 degrees with each other from the centre of the optical fiber cable 100. The 120 degrees placement allows even distribution of load among each three of the plurality of strength members 110a, 110b and 110c. In another aspect, the plurality of strength members 110a, 110b and 110c may be placed at any angle from the centre of the optical fiber cable 100.
[0035] The plurality of strength members 110a, 110b, 110c have an elastic
modulus greater than 45Gpa. In general, elastic modulus is a quantity that measures an object resistance to deformation upon application of stress. The elastic modulus is directly proportional to the stiffness of any material. In an aspect, a high elastic modulus is selected for the plurality of strength members 110a, 110b, 110c. The optical fiber cable 100 is all dielectric self supporting (ADSS), aerially suspended between poles. The optical fiber cable 100 uses the higher elastic modulus to support the cable without any metallic or conductive material. The above mentioned strain values are not achieved when the elastic modulus of the optical fiber cable 100 falls below 45Gpa.
[0036] In an aspect, the optical fiber cable 100 may be bent at a minimum
curvature of 7 times the cable outer diameter. The minimum curvature is directly proportional to the minimum bending radius. In addition, the minimum bending radius is directly proportional to the flexibility and handling of the optical fiber cable 100. In general, the minimum bend radius is the smallest allowed radius the cable is allowed to bend around and without impacting the optical performance of the cable.

[0037] In addition, the minimum bending radius is measured as the product of
cable outer diameter and cable multiplier. Further, the cable multipliers are determined by industry standards and vary depending on the cable type. However, the quality of the optical fiber cable 100 may be damaged when the cable multipliers are reduced below 7. In an example, a cable with 5mm outer diameter bends at 35mm of minimum radius without any damage. However, the same cable provides a minimum bend radius of 30mm at minimum curvature of 6 times the cable outer diameter may damage the quality of cable.
[0038] In an aspect, the optical fiber cable 100 includes the atleast one water
swellable element 112 between the optical fiber unit 102 and the sheath 108. In another aspect, the atleast one water swellable element 112 maybe placed at a different location. The atleast one water swellable element 112 prevents ingression of water in the stranded core of the optical fiber cable 100. In addition, the optical fiber cable 100 includes the filling strength member 114. The filling strength member 114 provides mechanical support to the optical fiber cable 100. The filling strength member 114 resists change in deformation of the optical fiber cable 100 upon stress application.
[0039] The foregoing descriptions of specific 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.
[0040] While several possible aspects of the invention have been described
above and illustrated in some cases, it should be interpreted and understood as to have been presented only by way of illustration and example, but not by limitation. Thus, the breadth and scope of a preferred aspect should not be limited by any of the above-described exemplary aspects.

CLAIMS

1. An optical fiber cable (100) comprising:
at least one optical fiber unit (102) having atleast one fiber (104);
a sheath (108) encapsulating the at least one optical fiber unit (102); and
a plurality of strength members (110a, 110b, 110c) embedded in the sheath (108), wherein the optical fiber cable (100) has a preferential bending ratio between 1-2.
2. The optical fiber cable (100) as claimed in claim 1, wherein the optical fiber cable (100) is an all-dielectric communication cable.
3. The optical fiber cable (100) as claimed in claim 1, wherein the plurality of strength member (110a, 110b, 110c) have an elastic modulus greater than 45GPa.
4. The optical fiber cable (100) as claimed in claim 1, further comprising atleast one water-swellable element (112) between the optical fiber unit (102) and the sheath (108).
5. The optical fiber cable (100) as claimed in claim 1, wherein a cabled fiber strain maybe equal to or less than 20% of fiber proof test strain at long-term load.

6. The optical fiber cable (100) as claimed in claim 1, wherein cabled fiber strain maybe equal to or less than 60% of fiber proof test strain at maximum load.
7. The optical fiber cable (100) as claimed in claim 1, further comprising at least three strength members (110a, 110b, 110c) such that at least one strength member has diameter different than other strength member.
8. The optical fiber cable (100) as claimed in claim 1, further comprising at least three strength members (110a, 110b, 110c) such that all strength members have same diameters.
9. The optical fiber cable (100) as claimed in claim 7, wherein each strength member of the plurality of strength members (110a, 110b, 110c) has a diameter between 0.4mm - 0.8mm.
10. The optical fiber cable (100) as claimed in claim 7, wherein a ratio of diameters of any two strength members of the plurality of strength members (110a, 110b, 110c) is equals to or less than 2.
11. The optical fiber cable (100) as claimed in claim 7, may be bent at a minimum curvature of 7 times the cable outer diameter.