Description:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“OPTICAL FIBER CABLE WITH MULTIFIBRE TIGHT-BUFFERED UNIT”

APPLICANTS:

Name : Sterlite Technologies Limited

Nationality : Indian

Address : 15th & 16th Floor, Capital Cyberscape,
Sector – 59, Gurugram, Haryana 122102

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

FIELD OF INVENTION
[0001] The present invention relates to optical fibers, and more particularly to an optical fiber cable with multi-fibre tight-buffered unit.
BACKGROUND
[0002] Optical fiber refers to the technology and the medium for the transmission of data as light pulses along an ultrapure strand of glass, which is as thin as a human hair. For many years, optical fibers have been extensively used in high-performance and long-distance data and networking. An optical fiber cable generally has a cable core comprising one or more optical fibers and a sheath surrounding the cable core. Conventionally, optical fiber cables where more than one optical fiber are required in a single unit, the optical fibers are loosely enclosed in tubes such as buffer tube, micro-modules, and the like. Sleeved micro module buffer layer having a thickness of less than 100 micrometres (µm) is unable to protect the optical fibers from aerial environment condition in last mile connectivity cable. Moreover, gel locked micro-module cannot be used in last mile home connectivity cables due to safety concerns and the optical fibers housed in dry micro-module are not able to block the water penetration inside the module. The optical fibers housed inside the sleeved module are unable to be coupled with other cable components i.e., fiber retraction under maximum overhead environmental load which leads to unwanted fiber break.
[0003] A prior art reference “US2008285924A1” discloses about Fibers are embedded and surrounded by acrylate resins. Another prior art reference “EP2652536A2” discloses that optical fibers are embedded in acrylate resin. Yet another prior art reference “CN1259677A” discloses multiple single fiber TB units connected together by webs. However, none of the prior art reference discloses about structural limitations to reduce water ingression in the optical fiber cable.
[0004] Therefore, there is a need for an optical fiber cable that overcomes one or more limitation associated with the available optical fiber cables.
OBJECT OF INVENTION
[0005] The principal object of the embodiments herein is to provide an optical fiber cable with multi-fibre tight-buffered unit.
SUMMARY
[0006] In an aspect of the present disclosure, an optical fiber cable is disclosed. The optical fiber cable has a plurality of optical fibers. Further, the optical fiber cable has a thermoplastic layer extruded over the plurality of optical fibers to form an optical unit such that the thermoplastic layer contacts a surface area in a range of 50% to 95% of each optical fiber of the plurality of optical fibers. Furthermore, the optical fiber cable has a sheath that surrounds the optical unit.
[0007] These and other aspects of the embodiments 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, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF FIGURES
[0008] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0009] FIG. 1 illustrates a cross-sectional view of an optical fiber cable;
[0010] FIG. 2 illustrates a cross-sectional view of another optical fiber cable; and
[0011] FIG. 3 illustrates a cross-sectional view of yet another optical fiber cable.
[0012] 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 OF FIGURES
[0013] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term “or” as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0014] The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments 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.
[0015] The term “optical fiber” as used herein refers to a light guide that provides high-speed data transmission. The optical fiber has one or more glass core regions and one or more glass cladding regions. The light moving through the glass core regions of the optical fiber relies upon the principle of total internal reflection, where the glass core regions have a higher refractive index (n1) than the refractive index (n2) of the glass cladding region of the optical fiber.
[0016] The term “optical fiber cable” as used herein refers to a cable that encloses a plurality of optical fibers.
[0017] The term “extrusion” as used herein refers to a process used to create the objects with a fixed cross-sectional profile such as a rod or a cylindrical tube. A hot molten material such as thermoplastic is pushed through a die with the desired cross-section and cooled down to attain the required shape.
[0018] The term “empty space” as used herein refers to a cross-sectional area of non-solid space present inside an optical unit to optical unit’s cross-sectional are with outer diameter. Further, the empty space may be a free space created between the optical fibers due to the geometry and/or arrangement of the plurality of optical fibers.
[0019] The detailed description of the appended drawings is intended as a description of the currently preferred aspects of the present disclosure, and is not intended to represent the only form in which the present disclosure may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different aspects that are intended to be encompassed within the spirit and scope of the present disclosure.
[0020] 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.
[0021] FIG. 1 illustrates a cross-sectional view of an optical fiber cable 100. The optical fiber cable 100 may have a plurality of optical fibers 102 of which first through fourth optical fibers 102a-102d are shown, a thermoplastic layer 104, and a sheath 106. In some aspects of the present disclosure, the plurality of optical fibers 102 may have 3 optical fibers to 6 optical fibers. Aspects of the present disclosure are intended to include and/or otherwise cover any number of optical fibers in the plurality of optical fibers 102 with the range of 3 optical fibers to 6 optical fibers, without deviating from the scope of the present disclosure. The thermoplastic layer 104 may be extruded over the plurality of optical fibers 102 to form at least one optical unit 108 (hereinafter interchangeably referred to and designated as “a multifibre tight buffered (TB) unit 108” and “the optical unit 108”). As illustrated, the optical fiber cable 100 has the plurality of optical fibers 102 surrounded by the thermoplastic layer 104 such that the plurality of optical fibers 102 has substantially no empty space therebetween.
[0022] The thermoplastic layer 104 may contact a surface area in a range of 50% to 95% of each optical fiber of the plurality of optical fibers 102. In other words, the thermoplastic layer 104 may contact each optical fiber of the plurality of optical fibers 102 (i.e., the first through fourth optical fibers 102a-102d) such that the surface area of each optical fiber of the plurality of optical fibers 102 (i.e., the first through fourth optical fibers 102a-102d) in contact with the thermoplastic layer 104 is in a range of 50% to 95%. In an aspect of the present disclosure, when the plurality of optical fibers 102 has 3 optical fibers (i.e., the optical unit 108 is 3 fibers optical unit), the surface area of each optical fiber of the plurality of optical fibers 102 in contact with the thermoplastic layer 104 is greater than 70% and less than 95%. In another aspect of the present disclosure, when the plurality of optical fibers 102 has 4 optical fibers (i.e., the optical unit 108 is 4 fibers optical unit), the surface area of each optical fiber of the plurality of optical fibers 102 in contact with the thermoplastic layer 104 is greater than 60% and less than 95%. In yet another aspect of the present disclosure, when the plurality of optical fibers 102 has 6 optical fibers (i.e., the optical unit 108 is 6 fibers optical unit), the surface area of each optical fiber of the plurality of optical fibers 102 in contact with the thermoplastic layer 104 is greater than 50% and less than 95%. In some aspects of the present disclosure, the optical unit 108 may be free of any additional solid, liquid, and semi-solid material between the plurality of optical fibers 102 and the thermoplastic layer 104.
[0023] In some aspects of the present disclosure, the thermoplastic layer 104 may be made up of, but not limited to, nylon, Polyvinyl chloride (PVC), Thermoplastic Polyurethane(TPU), Low-Smoke Zero-Halogen (LSZH or LSOH), and the like. Aspects of the present disclosure are intended to include and/or otherwise cover any type of the thermoplastic material, without deviating from the scope of the present disclosure.
[0024] Specifically, the optical unit 108 that encloses the plurality of optical fibers 102 together may have a diameter in a range of 700 micrometres (µm) to 1000 µm. Preferably, the diameter of the optical unit 108 may be 900 µm. Specifically, the diameter of the optical unit 108 may be the a range of 700 µm to 1000 µm due to the reason that the optical unit 108 having a diameter of less than 700 µm and with minimum 3 optical fibers will have very less thickness of the material. In other words, the optical unit 108 with diameter of less than 700 µm may fail to produce required mechanical resistance to crush, impact, and abrasion. On the other hand, the optical unit 108 with a diameter of greater than 1000 µm will have space constrains in a low diameter FTTx cable design.
[0025] The optical unit 108 may have very less empty space therein. In some aspects of the present disclosure, where the empty space in the optical unit 108 may be in a range of 0.5% to 3%. Specifically, the empty space in the optical unit 108 may be in a range of 0.5% to 3% due to the reason that when the empty space in the optical unit 108 is less than 0.5%, the mechanical stability of the optical unit 108 may be distorted. On the other hand, when the empty space in the optical unit 108 is greater than 3%, the optical unit 108 will have extra space to penetrate water in operations and also may introduce mechanical instability in the multi fiber design of the optical fiber cable 100.
[0026] In some aspects of the present disclosure, the optical unit 108 may be adapted to provide mechanical protection to the plurality of optical fibers 102. Further, the optical unit 108 may be adapted to prevent water ingression as the optical unit 108 has very less empty space inside. Specifically, the surface area of each optical fiber of the plurality of optical fibers 102 in contact with the thermoplastic layer 104 is in the range of 50% to 95% as below 50%, the empty space inside the optical unit 108 will be higher, that may lead to water leak during water penetration test. On the other hand, when the surface area of each optical fiber of the plurality of optical fibers 102 in contact with the thermoplastic layer 104 is greater than 95%, a mechanical stability of the optical unit 108 will be distorted i.e. the reduction in bending performance of the fiber unit and increase in optical loss during handling. As illustrated, a maximum open ended surface area of the plurality of optical fibers 102 is covered by the thermoplastic material that is extruded on the plurality of optical fibers 102 such that the thermoplastic material enhances the mechanical protection to the plurality of optical fibers 102 by increasing a crush and impact resistance of the optical unit 108. Specifically, a thickness of the thermoplastic material over the plurality of optical fibers remains higher as compared that enhances environmental protections such that thermal cycling and ageing of the optical fiber cable 100.
[0027] In some aspects of the present disclosure, one or more optical fibers of the plurality of optical fibers 102 may be coated with a water blocking coating. For example, when the plurality of optical fibers 102 has four optical fibers i.e., the first through fourth optical fibers 102a-102d, the first optical fiber 102a (i.e., one optical fiber) may be coated with the water blocking coating. In another example, when the plurality of optical fibers 102 has four optical fibers i.e., the first through fourth optical fibers 102a-102d, the first and second optical fibers 102a and 102b (i.e., two optical fibers) may be coated with the water blocking coating. In yet another example, when the plurality of optical fibers 102 has four optical fibers i.e., the first through fourth optical fibers 102a-102d, the first through third optical fibers 102a-102c (i.e., three optical fibers) may be coated with the water blocking coating. In another example, when the plurality of optical fibers 102 has four optical fibers i.e., the first through fourth optical fibers 102a-102d, the first through fourth optical fibers 102a-102d (i.e., four optical fibers) may be coated with the water blocking coating. In some aspects of the present disclosure, one or more optical fibers of the plurality of optical fibers 102 may be without a water blocking coating. In some aspects of the present disclosure, to enhance a water blocking capability of the optical unit 108, at least one optical fiber of the plurality of optical fibers 102 may be covered with a water swellable coating.
[0028] The sheath 106 may surround the optical unit 108. Specifically, the sheath 106 may be an outermost layer of the optical fiber cable 100 that surrounds the optical unit 108 and may provide support, strength, and insulation to the optical fiber cable 100. Further, the sheath 106 may facilitate to reduce abrasion and to provide the optical fiber cable 100 with extra protection against external mechanical effects such as crushing. In some aspects of the present disclosure, the sheath 106 may be made up of a material a thermoplastic material such as, but not limited to, Polyethylene (PE) material, Low-Smoke Zero-Halogen (LSZH) material, Polyvinyl Chloride (PVC) material, polyamide (PA) material, and the like. Aspects of the present disclosure are intended to include and/or otherwise cover any type of the material for the sheath 106, known to a person having ordinary skill in the art, without deviating from the scope of the present disclosure.
[0029] In some aspects of the present disclosure, the optical fiber cable 100 may have one or more layers (not shown) disposed between the optical unit 108 and the sheath 106. In some aspects of the present disclosure, the one or more layers may be, but not limited to, water swellable yarns, thermoplastic layer (tube, inner sheath), water blocking tape (WBT), tensile yarn layer, armor layer (metal and/or dielectric), fire retardant tape, and the like. Aspects of the present disclosure are intended to include and/or otherwise cover any type of the one or more layers disposed between the optical unit 108 and the sheath 106 without deviating from the scope of the present disclosure.
[0030] In some aspects of the present disclosure, the optical fiber cable 100 may further have one or more ripcords (not shown) disposed between the optical unit 108 and the sheath 106. Specifically, the one or more ripcords may facilitate removal of the sheath 106 for accessing the optical unit 108 having the plurality of optical fibers 102 when the one or more ripcords are pulled to tear the sheath 106.
[0031] FIG. 2 illustrates a cross-sectional view of another optical fiber cable 200. The optical fiber cable 200 is substantially similar to the optical fiber cable 100 with like elements referenced with like reference numerals. However, the optical fiber cable 200 has different arrangement of the plurality of optical fibers 102 such that the plurality of optical fibers 102 surrounded by the thermoplastic layer 104 has an empty space 202 therebetween. As illustrated, the plurality of optical fibers 102 i.e., the first through fourth optical fibers 102a-102d may be disposed such that the first through fourth optical fibers 102a-102d defines the empty space 202 therebetween.
[0032] As discussed in reference to FIG. 1, the optical unit 108 may have very little empty space (i.e., the empty space 202) therein. In some aspects of the present disclosure, the empty space 202 in the optical unit 108 may be in the range of 0.5% to 3%. Specifically, the empty space 202 in the optical unit 108 may be in the range of 0.5% to 3% due to the reason that when the empty space 202 in the optical unit 108 is less than 0.5%, the mechanical stability of the optical unit 108 may be distorted. On the other hand, when the empty space 202 in the optical unit 108 is greater than 3%, the optical unit 108 will have extra space to penetrate water in operations and also may introduce mechanical instability in the multi fiber design of the optical fiber cable 200.
[0033] FIG. 3 illustrates a cross-sectional view of yet another optical fiber cable 300. The optical fiber cable 300 is substantially similar to the optical fiber cable 100 with like elements referenced with like reference numerals (to keep the illustration clear and concise, few reference numerals are not marked, however, it is to be understood that each reference numeral associated with each element of the optical fiber cable 100 is applicable to the optical fiber cable 300). However, the optical fiber cable 300 has first through fourth optical units 302a-302d. Specifically, each optical unit of the first through fourth optical units 302a-302d may be substantially similar to the at least one optical unit 108 of the optical fiber cable 100. Although FIG. 3 illustrates that the optical fiber cable 300 has four optical units (i.e., the first through fourth optical units 302a-302d), it will be apparent to a person skilled in the art that the scope of the present disclosure is not limited to it. In various other aspects, the optical fiber cable 300 may have any number of optical units, without deviating from the scope of the present disclosure. In such a scenario, each optical unit will be structurally and functionally similar to the optical fiber unit 108 of the optical fiber cable 100 as described above.
[0034] Thus, the optical fiber cable 100, 200, 300 of the present disclosure have the plurality of optical fibers 102, the thermoplastic layer 104, and the sheath 106. In some aspects of the present disclosure, the plurality of optical fibers 102 may have 3 optical fibers to 6 optical fibers. The thermoplastic layer 104 may be pressure extruded over the plurality of optical fibers 102 to form at least one optical unit 108. The optical unit 108 may be adapted to prevent water ingression as the optical unit 108 has very less empty space inside. Specifically, the surface area of each optical fiber of the plurality of optical fibers 102 in contact with the thermoplastic layer 104 may be in the range of 50% to 95%. Further, the optical unit 108 provides better mechanical load protection, better environmental protection, and is easy to manufacture, than micromodules.
[0035] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within scope of the embodiments as described herein.
[0036] 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:CLAIMS

We Claim:
1. An optical fiber cable (100, 200, 300) comprising:
a plurality of optical fibers (102);
a thermoplastic layer (104) extruded over the plurality of optical fibers (102) to form an optical unit (108) such that the thermoplastic layer (104) contacts a surface area in a range of 50% to 95% of each optical fiber of the plurality of optical fibers (102); and
a sheath (106) that surrounds the optical unit (108).
2. The optical fiber cable (100, 200, 300) of claim 1, where one or more optical fibers of the plurality of optical fibers (102) is coated with a water blocking coating (110).
3. The optical fiber cable (100, 200, 300) of claim 1, where the optical unit (108) has an outer diameter in a range of 700 micrometres (µm) to 1000 µm.
4. The optical fiber cable (100, 200, 300) of claim 1, where the plurality of optical fibers (102) has 3 optical fibers to 6 optical fibers.
5. The optical fiber cable (100, 200, 300) of claim 1, where the optical unit (108) is made up of a material selected from one of, nylon, Polyvinyl chloride (PVC), Thermoplastic Polyurethane(TPU), and Low-Smoke Zero-Halogen (LSZH or LSOH).
6. The optical fiber cable (100, 200, 300) of claim 1, further comprising one or more layers disposed between the sheath (106) and the optical unit (108).
7. The optical fiber cable (100, 200, 300) of claim 6, where the one or more layers is one of, water swellable yarns, thermoplastic layer (tube, inner sheath), water blocking tape (WBT), tensile yarn layer, armor layer (metal and/or dielectric), fire retardant tape, or a combination thereof.
8. The optical fiber cable (100, 200, 300) of claim 1, where the optical unit (108) is free of any additional solid, liquid, and semi-solid material between the plurality of optical fibers (102) and the thermoplastic layer (104).
9. The optical fiber cable (100, 200, 300) of claim 1, where the optical unit (108) has an empty space in a range of 0.5% to 3%.
10. The optical fiber cable (100, 200, 300) of claim 1, where, when (i) the optical unit (108) is 3 fibers optical unit, the surface area of each optical fiber of the plurality of optical fibers (102) in contact with the thermoplastic layer (104) is greater than 70% and less than 95%, (ii) the optical unit (108) is 4 fibers optical unit, the surface area of each optical fiber of the plurality of optical fibers (102) in contact with the thermoplastic layer (104) is greater than 60% and less than 95%, (iii) the optical unit (108) is 6 fibers optical unit, the surface area of each optical fiber of the plurality of optical fibers (102) in contact with the thermoplastic layer (104) is greater than 50% and less than 95%.