WO2018138736A2

WO2018138736A2 - Optical fiber draw assembly and fabricated optical fiber thereof

Info

Publication number: WO2018138736A2
Application number: PCT/IN2018/050037
Authority: WO
Inventors: Anand KUMAR PANDEY; Munige Srinivas REDDY; Sankalp SELOT
Original assignee: Sterlite Technologies Limited
Priority date: 2017-01-27
Filing date: 2018-01-24
Publication date: 2018-08-02
Also published as: WO2018138736A3; CA3070060A1

Abstract

The present disclosure provides an optical fiber draw assembly (100). The optical fiber draw assembly (100) includes a central core rod (102). The central core rod (102) includes a core region (103) longitudinally extending in a vertical direction. The central core rod (102) further includes a first cladding region (105). The optical fiber draw assembly (100) further includes a fluorine-doped tube (104) longitudinally extending from a first end (114) to a second end (116) in the vertical direction. The optical fiber draw assembly (100) further includes a hollow clad cylinder (106). The core rod assembly (118) is sheathed inside the hollow clad cylinder (106). The central core rod (102) and the fluorine-doped tube (104) collectively form the core rod assembly (118). The geometrical center of the core rod assembly (118) and the geometrical center of the hollow clad cylinder (106) coincide.

Description

OPTICAL FIBER DRAW ASSEMBLY AND FABRICATED OPTICAL FIBER

THEREOF TECHNICAL FIELD

[001] The present invention relates to the field of optical communication technology and, in particular, relates to an optical fiber draw assembly and the method of manufacturing the bend-insensitive optical fiber. The present application is based on, and claims priority from an Indian Application Number 201721003135 filed on 27th January 2017 the disclosure of which is hereby incorporated by reference herein.

BACKGROUND

[002] Over the years, optical fibers have been extensively used for fiber-to-the-premises (FTTx) applications. One such optical fiber is a bend-insensitive optical fiber. These bend-insensitive optical fibers must have good bending performance and optical characteristics compatible with G.657 standards. Various optical fiber designs solutions and manufacturing methods are employed to fabricate these bend-insensitive optical fibers. One of the optical fiber design solution is a trench-assisted cladding fiber design. The optical fiber having trench-assisted cladding fiber design includes a core region and a depressed cladding region. The depressed cladding region includes a trench region and a cladding region. In addition, the depressed cladding region enhances the light confinement and reduces losses due to bending. Moreover, the depressed cladding region is formed by doping a central core rod with a refractive index lowering element like fluorine. Traditionally, these trench-assisted cladding fibers are manufactured by an online rod-in-cylinder (RIC) approach. The online rod-in-cylinder approach utilizes a preform assembly from which these trench-assisted cladding fibers are drawn.

[003] These optical fiber designs and manufacturing methods are trade-offs. These trench- assisted cladding fiber designs bear fabrication and bend range constraints. Moreover, these trench-assisted cladding fibers are difficult to manufacture due to the difficulty in critical balancing of various optical characteristics and bending resistance performances. In addition, the preform assembly is not efficiently utilized in the online rod-in-cylinder approach due to increased attenuation as observed towards the top side of the preform assembly. The incomplete utilization of the preform assembly results in high manufacturing cost of these optical fibers. [004] In light of the above stated discussion, there is a need for an optical fiber draw assembly from which an optical fiber can be drawn that overcomes the above stated disadvantages and provides ease in manufacturing.

OBJECT OF THE DISCLOSURE

[005] A primary object of the present disclosure is to provide an optical fiber preform assembly to draw an optical fiber of desired properties.

[006] Another object of the present disclosure is to draw an optical fiber with low attenuation.

[007] Another object of the present disclosure is to draw a bend-insensitive optical fiber.

[008] Yet another object of the present disclosure is to draw a bend-insensitive optical fiber that features optical characteristics well below the standard limit recommended by the ITU-T.

[009] Yet another object of the present disclosure is to draw the optical fiber that features low sensitivity to bend conditions and handling.

[010] Yet another object of the present disclosure is to provide a method to manufacture bend-insensitive optical fiber with low attenuation.

[011] Yet another object of the present disclosure is to draw the bend-insensitive optical fiber with reduced manufacturing cost.

SUMMARY

[012] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[013] In an aspect, an optical fiber draw assembly is provided. The optical fiber draw assembly includes a central core rod longitudinally extending from a first end to a second end in a vertical direction. The central core rod includes a core region longitudinally extending in the vertical direction. The central core rod further includes a first cladding region longitudinally extending in the vertical direction. The optical fiber draw assembly further includes a fluorine-doped tube longitudinally extending from the first end to the second end in the vertical direction. The optical fiber draw assembly further includes a hollow clad cylinder. The core rod assembly is sheathed inside the hollow clad cylinder. The first end and the second end are associated with the optical fiber draw assembly. The first end is positioned vertically above the second end. The central core rod has a diameter d2. The core region has a diameter dl. The core region has an index of refraction delta- 1. The core region and the first cladding region collectively form the central core rod. The fluorine-doped tube has an inner diameter d3. The fluorine-doped tube has an outer diameter d4. The fluorine-doped tube has a thickness tl. The fluorine- doped tube has an index of refraction delta-2. The central core rod is placed inside the fluorine-doped tube. The central core rod and the fluorine-doped tube collectively form a core rod assembly. The core rod assembly has a geometrical center. The hollow clad cylinder has a geometrical center. The geometrical center of the core rod assembly and the geometrical center of the hollow clad cylinder coincide with each other in the optical fiber draw assembly. The hollow clad cylinder has an inner diameter d5. The hollow clad cylinder has an outer diameter d6. The core rod assembly and the hollow clad cylinder collectively form an optical fiber preform assembly. The optical fiber preform is fabricated at two different set of values for a plurality of parameters. A first set of values for the plurality of parameters corresponds to a 199 millimeters to 205 millimeters process of the optical fiber draw assembly. The plurality of parameters for the first set of values comprises the central core rod diameter d2, the core region diameter dl, the fluorine-doped tube inner diameter d3, the fluorine-doped tube outer diameter d4, the fluorine-doped tube thickness tl, the hollow clad cylinder inner diameter d5, the hollow clad cylinder outer diameter d6, the index of refraction delta- 1 for core region and the index of refraction delta-2 for fluorine-doped tube. For the first set of values, the central core rod diameter d2 is in the range of about 31.5 millimeters to 32.5 millimeters, the core region diameter dl is in the range of about 12.31 millimeters to 12.8 millimeters, the fluorine-doped tube inner diameter d3 is in the range of about 33.5 ± 0.7 millimeters, the fluorine-doped tube outer diameter d4 is in the range of about 49.5 ± 0.7 millimeters and 53.5 ± 0.7 millimeters, the fluorine-doped tube thickness tl is in the range of about 8 millimeters and 10 millimeters, the hollow clad cylinder inner diameter d5 is in the range of about 51.4 ± 0.7 millimeters and 54.5 ± 0.7 millimeters, the hollow clad cylinder outer diameter d6 is in the range of about 201 ± 2 millimeters, the index of refraction delta- 1 for core region is in the range of about 0.35 and 0.37, the index of refraction delta-2 for fluorine-doped tube is in the range of about -0.27 and -0.33. A second set of values for a plurality of parameters corresponds to a 215 ± 3 millimeters process of the optical fiber draw assembly, wherein the plurality of parameters for the second set of values comprises the central core rod diameter d2, the core region diameter dl, the fluorine-doped tube inner diameter d3, the fluorine-doped tube outer diameter d4, the fluorine-doped tube thickness tl, the hollow clad cylinder inner diameter d5, the hollow clad cylinder outer diameter d6, the index of refraction delta- 1 for the core region, the index of refraction delta-2 for the fluorine-doped tube. For the second set of values, the central core rod diameter d2 is in the range of about 34.4 ± 0.25 millimeters, the core region diameter dl is in the range of about 13.23 millimeters to 13.76 millimeters, the fluorine-doped tube inner diameter d3 is in the range of about 35.9 ± 0.7 millimeters, the fluorine-doped tube outer diameter d4 is in the range of about 54.5 ± 0.7 millimeters and 57.3 ± 0.7 millimeters, the fluorine-doped tube thickness tl is in the range of about 9.3 millimeters and 10.7 millimeters, the hollow clad cylinder inner diameter d5 is in the range of about 55.3 ± 0.7 millimeters and 58.1 ± 0.7 millimeters, the hollow clad cylinder outer diameter d6 is in the range of about 215 ± 2.5 millimeters, the index of refraction delta- 1 of the core region is in the range of about 0.35 and 0.37, the index of refraction delta-2 of the fluorine-doped tube is in the range of about -0.27 and -0.33.

[014] In an embodiment of the present disclosure, the optical fiber draw assembly includes a holding tube. The central core rod is coupled to the holding tube at the first end of the optical fiber draw assembly.

[015] In an embodiment of the present disclosure, the optical fiber draw assembly includes a handling tube. The hollow clad cylinder is coupled to the handling tube at the first end of the optical fiber draw assembly.

[016] In an embodiment of the present disclosure, the optical fiber draw assembly includes a spacer. The spacer is placed between the core rod assembly and the holding tube. In an embodiment of the present disclosure, the spacer is a solid spacer. In another embodiment of the present disclosure the spacer is a slotted spacer.

[017] In an embodiment of the present disclosure, an optical fiber is drawn from the optical fiber draw assembly. The optical fiber has a core region, wherein the core region has an alpha parameter, wherein the alpha parameter is in a range of about 6 and 7.5 for the optical fiber drawn in both the processes corresponds to 199 millimeters to 205 millimeters and 215 ± 3 millimeters.

[018] In an embodiment of the present disclosure, the central core rod is treated with an etching process, wherein the etching process shed a thickness t2 from the central core rod. The thickness t2 is about 0.5 millimeters in both the processes correspond to 199 millimeters to 205 millimeters and 215 ± 3 millimeters.

[019] In an embodiment of the present disclosure, the fluorine-doped tube is treated with an etching process, wherein the etching process shed the thickness t3 from the fluorine- doped tube. The thickness t3 is about 30 microns in both the processes corresponds to

199 millimeters to 205 millimeters and 215 ± 3 millimeters.

[020] In an embodiment of the present disclosure, the optical fiber drawn has a bare diameter of about 125 micrometer.

[021] In an embodiment of the present disclosure, the optical fiber draw assembly has a cladding to core ratio d2/dl measured before the etching process. The cladding to core ratio d2/dl is in a range of about 2.5 and 2.6 in both the processes corresponds to 199 millimeters to 205 millimeters and 215 ± 3 millimeters.

[022] In an embodiment of the present disclosure, the optical fiber draw is in the range of about 7000 fiber kilometer - 8000 fiber kilometer in both the processes corresponds to

199 millimeters to 205 millimeters and 215 ± 3 millimeters.

[023] In an embodiment of the present disclosure, the optical fiber drawn meets the requirements of ITU-T G.657 A2/B2.

[024] Other aspects and example embodiments are provided in the drawings and the detailed description that follows.

BRIEF DESCRIPTION OF THE FIGURES

[025] 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:

[026] FIG. 1 illustrates a schematic diagram of the optical fiber draw assembly utilizing online RIC method, in accordance with an embodiment of the present disclosure.

[027] FIG. 2 illustrates a cross-sectional view of an optical fiber, in accordance with an embodiment of the present disclosure. [028] FIG. 3 illustrates a refractive index profile of the drawn optical fiber, in accordance with an embodiment of the present disclosure.

[029] FIG 4 illustrates a draw length - attenuation profile of the drawn optical fiber, in accordance with an embodiment of the present disclosure.

[030] FIG 5 illustrates a draw length - OH loss profile of the drawn optical fiber, in accordance with an embodiment of the present disclosure.

[031] It should be noted that the accompanying figures are intended to present illustrations of exemplary embodiments 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

[032] Reference will now be made in detail to selected embodiments of the present disclosure in conjunction with accompanying figures. The embodiments described herein are not intended to limit the scope of the disclosure, and the present disclosure should not be construed as limited to the embodiments 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 embodiments 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.

[033] It should be noted that the terms "first", "second", and the like, herein do not denote any order, 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.

[034] FIG. 1 illustrates a schematic diagram of an optical fiber draw assembly 100 using online rod-in-cylinder (RIC) method, in accordance with an embodiment of the present disclosure. In general, RIC process refers to a manufacturing process of a large-sized fiber preform by inserting a core rod assembly into a large tube after processing the core rod assembly and the large tube. The optical fiber draw assembly 100 is utilized to yield optical fiber 700 of desired characteristics. The optical fiber draw assembly 100 includes a plurality of components. The plurality of components includes a central core rod 102, a fluorine-doped tube 104, a hollow clad cylinder 106, a spacer 108, a holding tube 110 and a handling tube 112. The plurality of components is utilized together to yield the optical fiber 200. Furthermore, the central core rod 102 includes the core region 204 and the first cladding region 206.

[035] In an embodiment of the present disclosure, the central core rod 102 is longitudinally extended from a first end 114 to a second end 116 in a vertical direction. The first end 114 and the second end 116 are associated with the optical fiber draw assembly 100. The central core rod 102 has a diameter d2 (as shown in fig. 1). In addition, the central core rod 102 is coupled to the holding tube 110 at the first end 114. In an embodiment of the present disclosure, the first end 114 is vertically above the second end 116. Moreover, the central core rod 102 is present inside the fluorine-doped tube 104. In an embodiment of the present disclosure the central core rod 102 undergoes etching process. In general, etching of a tube refers to reducing diameter of the tube with the facilitation of a suitable etching process. In an embodiment of the present disclosure, the etching has reduced from 40 hours to 5 hours in case of continuous etching. The central core rod 102 has the etching thickness of t2. The central core rod 102 includes a core region 103 and a first cladding region 105. The core region 103 is longitudinally extended in the vertical direction. The core region has a diameter dl (as shown in fig. 1). The core region 103 has an index of refraction delta- 1. The refractive index or index of refraction of a material is a dimensionless number that describes how light propagates through that medium. In an embodiment of the present disclosure, the fluorine-doped tube 104 is extended longitudinally from the first end 114 to the second end 116. The fluorine-doped tube 104 has an inner diameter d3 and an outer diameter d4 (as shown in fig. 1). The fluorine-doped tube 104 has a thickness tl. The fluorine-doped tube 104 has an index of refraction delta2. In an embodiment of the present disclosure, the fluorine- doped tube 104 undergoes etching process. The fluorine-doped tube 104 has an etching thickness of t3. In addition, the fluorine-doped tube 104 includes the trench region 208. The central core rod 102 is present inside the fluorine-doped tube 104 at a pre-defined radial distance to optimize the plurality of optical parameters. The central core rod 102 and the fluorine-doped tube 104 together form the core rod assembly 118.

] Further, the core rod assembly 118 and the hollow clad cylinder 106 are assembled to obtain an optical fiber preform assembly 120. The core rod assembly 118 is sheathed in the hollow clad cylinder 106 in such a way that a geometrical center of the core rod assembly 118 coincides with a geometrical center of the hollow clad cylinder 106. The hollow clad cylinder 106 has an inner diameter d5 and an outer diameter d6 (as shown in fig. 1). In an embodiment of the present disclosure, the hollow clad cylinder 106 is coupled to the handling tube 112 at the first end 114 of the optical fiber draw assembly 100. In an embodiment of the present disclosure, the spacer 108 is placed between the core rod assembly 118 and the holding tube 110. [037] In an embodiment of the present disclosure, the optical fiber draw assembly 100 fabricates an optical fiber preform having a cladding by core ratio. The cladding by core ratio is measured before etching. In an embodiment of the present disclosure the cladding by core ratio before etching is d2/dl.

[038] The optical fiber 200 (described in detail below in the patent application) is manufactured by placing the fluorine-doped tube 104 radially between the central core rod 102 and the hollow clad cylinder 106. The fluorine-doped tube 104 is placed such that the trench region 208 is formed in the refractive index profile of the optical fiber 200. In an embodiment of the present disclosure, the fluorine-doped tube 104 is placed at an optimized radial distance from the central core rod 102 to obtain the cladding-to-core ratio of 2.4 - 2.8. Further, the optical fiber preform assembly 120 is heated vertically in a furnace. During heating, the optical fiber preform assembly 120 collapses in the furnace and yield the optical fiber 200 from the second end 116 of the optical fiber draw assembly 100. In another embodiment of the present disclosure, once the optical fiber preform assembly 120 collapses, the optical fiber preform assembly 120 is withdrawn from the furnace and later re -heated to yield optical fiber 200. The optical fiber 200 that is yield has a core region. The yielded optical fiber 200 has a bare fiber diameter db_are- In general, bare fiber refers to a glass fiber without a coating layer inside. The bare fiber refers to an optical fiber that has just left furnace and is remaining intact.

[039] The optical fiber preform is fabricated at two different set of values for a plurality of parameters. The two different set of values includes a first set of values and a second set of values. The first set of values corresponds to a 199 millimeters to 205 millimeters process of the optical fiber draw assembly 100. The second set of values corresponds to a 215 ± 3 millimeters process of the optical fiber draw assembly 100. In an embodiment of the present disclosure, the optical fiber preform is manufactured at any suitable set of values. The first set of values is defined for a plurality of parameters. The plurality of parameters for the first set of values includes the diameter dl of the core region 103 of the central core rod 102, the diameter d2 of the central core rod 102, the inner diameter d3 of the fluorine-doped tube 104 and the outer diameter d4 of the fluorine-doped tube 104. Further, the plurality of parameters includes the inner diameter d5 of the hollow clad cylinder 106, the outer diameter d6 of the hollow clad cylinder 106, the diameter dbare of the target bare optical fiber 200. Furthermore, the plurality of parameters includes the thickness tl of the fluorine-doped tube 104, the thickness t2 of the central core rod 102 etching, the thickness t3 of the fluorine-doped tube 104 etching, the index of refraction delta- 1 of the core region 103 of the central core rod 102, the index of refraction delta-2 of the fluorine-doped tube 104, the cladding to core ratio d2/dl of the optical fiber preform and the alpha of the core region 103 of the central core rod 102. In an embodiment of the present disclosure, the first set of values is defined by any other suitable parameters if the like.

[040] In a first example, the plurality of parameters of the first set of values corresponding to the 199 millimeters to 205 millimeters process of the optical fiber draw assembly 100 is as described in the paragraph. The diameter dl of the core region 103 of the central core rod 102 is about 12.31 millimeters. The diameter d2 of the central core rod 102 is in a range of about 31.5 millimeters to 32.5 millimeters. The inner diameter d3 of the fluorine-doped tube 104 is in a range of about 33.5 ± 0.7 millimeters. The outer diameter d4 of the fluorine-doped tube 104 is in a range of about 49.5 ± 0.7 millimeters. Further, the inner diameter d5 of the hollow clad cylinder 106 is in a range about 51.4 ± 0.7 millimeters. The outer diameter d6 of the hollow clad cylinder 106 is in a range about 201 ± 2.0 millimeters. The diameter d are of the target bare optical fiber 200 is about 125 micrometer. Furthermore, the thickness tl of the fluorine-doped tube 104 is about 8 millimeters. The thickness t2 of the central core rod 102 etching is about 0.5 millimeters. The thickness t3 of the fluorine-doped tube 104 etching is about 30 microns. The index of refraction delta- 1 of the core region 103 of the central core rod 102 is in a range of about 0.35 to 0.37. The cladding to core ratio d2/dl of the optical fiber preform is about 2.6. The index of refraction delta-2 of the fluorine-doped tube 104 is in a range of about - 0.27 to -0.33. The alpha of the core region of the optical fiber 200 is in a range of about 6.0 to 7.5. In an embodiment of the present disclosure, the plurality of parameters of the first set of values may have any suitable value in the first example.

[041] In a second example, the plurality of parameters of the first set of values corresponding to the 199 millimeters to 205 millimeters process of the optical fiber draw assembly 100 is as described in the paragraph. The diameter dl of the core region 103 of the central core rod 102 is about 12.8 millimeters. The diameter d2 of the central core rod 102 is in a range of about 31.5 millimeters to 32.5 millimeters. The inner diameter d3 of the fluorine-doped tube 104 is in a range of about 33.5 ± 0.7 millimeters. The outer diameter d4 of the fluorine-doped tube 104 is in a range of about 49.5 ± 0.7 millimeters. Further, the inner diameter d5 of the hollow clad cylinder 106 is in a range about 51.4 ± 0.7 millimeters. The outer diameter d6 of the hollow clad cylinder 106 is in a range about 201 ± 2.0 millimeters. The diameter d are of the target bare optical fiber 200 is about 125 micrometer. Furthermore, the thickness tl of the fluorine-doped tube 104 is about 8 millimeters. The thickness t2 of the central core rod 102 etching is about 0.5 millimeters. The thickness t3 of the fluorine-doped tube 104 etching is about 30 microns. The index of refraction delta- 1 of the core region 103 is in a range of about 0.35 to 0.37. The cladding to core ratio d2/dl of the optical fiber preform is about 2.5. The index of refraction delta-2 of the fluorine-doped tube 104 is in a range of about -0.27 to -0.33. The alpha of the core region of the optical fiber 200 is in a range of about 6.0 to 7.5. In an embodiment of the present disclosure, the plurality of parameters of the first set of values may have any suitable value in the second example.

] In a third example, the plurality of parameters of the first set of values corresponding to the 199 millimeters to 205 millimeters process of the optical fiber draw assembly 100 is as described in the paragraph. The diameter dl of the core region 103 of the central core rod 102 is about 12.31 millimeters. The diameter d2 of the central core rod 102 is in a range of about 31.5 millimeters to 32.5 millimeters. The inner diameter d3 of the fluorine-doped tube 104 is in a range of about 33.5 ± 0.7 millimeters. The outer diameter d4 of the fluorine-doped tube 104 is in a range of about 53.5 ± 0.7 millimeters. Further, the inner diameter d5 of the hollow clad cylinder 106 is in a range about 54.5 ± 0.7 millimeters. The outer diameter d6 of the hollow clad cylinder 106 is in a range about 201 ± 2.0 millimeters. The diameter d are of the target bare optical fiber 200 is about 125 micrometer. Furthermore, the thickness tl of the fluorine-doped tube 104 is about 10 millimeters. The thickness t2 of the central core rod 102 etching is about 0.5 millimeters. The thickness t3 of the fluorine-doped tube 104 etching is about 30 microns. The index of refraction delta- 1 of the core region 103 of the central core rod 102 is in a range of about 0.35 to 0.37. The cladding to core ratio d2/dl of the optical fiber preform is about 2.6. The index of refraction delta-2 of the fluorine-doped tube 104 is in a range of about - 0.27 to -0.33. The alpha of the core region 103 of the central core rod 102 is in a range of about 6.0 to 7.5. In an embodiment of the present disclosure, the plurality of parameters of the first set of values may have any suitable value in the third example.

[043] In a fourth example, the plurality of parameters of the first set of values corresponding to the 199 millimeters to 205 millimeters process of the optical fiber draw assembly 100 is as described in the paragraph. The diameter dl of the core region 103 of the central core rod 102 is about 12.8 millimeters. The diameter d2 of the central core rod 102 is in a range of about 31.5 millimeters to 32.5 millimeters. The inner diameter d3 of the fluorine-doped tube 104 is in a range of about 33.5 ± 0.7 millimeters. The outer diameter d4 of the fluorine-doped tube 104 is in a range of about 53.5 ± 0.7 millimeters. Further, the inner diameter d5 of the hollow clad cylinder 106 is in a range about 54.5 ± 0.7 millimeters. The outer diameter d6 of the hollow clad cylinder 106 is in a range about 201 ± 2.0 millimeters. The diameter d are of the target bare optical fiber 200 is about 125 micrometer. Furthermore, the thickness tl of the fluorine-doped tube 104 is about 10 millimeters. The thickness t2 of the central core rod 102 etching is about 0.5 millimeters. The thickness t3 of the fluorine-doped tube 104 etching is about 30 microns. The index of refraction delta- 1 of the core region 103 of the central core rod 102 is in a range of about 0.35 to 0.37. The cladding to core ratio d2/dl of the optical fiber preform is about 2.5. The index of refraction delta-2 of the fluorine-doped tube 104 is in a range of about -0.27 to -0.33. The alpha of the core region 103 of the central core rod 102 is in a range of about 6.0 to 7.5. In an embodiment of the present disclosure, the plurality of parameters of the first set of values may have any suitable value in the fourth example.

[044] The second set of values is defined for a plurality of parameters of the optical fiber draw assembly 100. The plurality of parameters for the second set of values includes the diameter dl of the core region 103 of the central core rod 102, the diameter d2 of the core rod, the inner diameter d3 of the fluorine-doped tube and the outer diameter d4 of the fluorine-doped tube. Further, the plurality of parameters includes the inner diameter d5 of the hollow clad cylinder, the outer diameter d6 of the hollow clad cylinder, the diameter d are of the target bare fiber. In general, bare fiber refers to a glass fiber without a coating layer inside. The bare fiber refers to an optical fiber that has just left furnace and is remaining intact. Furthermore, the plurality of parameters includes the thickness tl of the fluorine-doped tube, the thickness t2 of the core rod etching, the thickness t3 of the fluorine-doped tube etching, the index of refraction delta- 1 of the core, the index of refraction delta-2 of the fluorine-doped tube, the cladding to core ratio d2/dl of the optical fiber preform and the alpha of the core. In an embodiment of the present disclosure, the second set of values is defined by any other suitable parameters if the like.

[045] In a fifth example, the plurality of parameters of the second set of values corresponding to the 215 ± 3 millimeters process of the optical fiber draw assembly 100 is as described in the paragraph. The diameter dl of the core region 103 of the central core rod 102 is about 13.23 millimeters. The diameter d2 of the central core rod 102 is in a range of about 34.4 ± 0.25 millimeters. The inner diameter d3 of the fluorine-doped tube 104 is in a range of about 35.9 ± 0.7 millimeters. The outer diameter d4 of the fluorine-doped tube 104 is in a range of about 54.5 ± 0.7 millimeters. Further, the inner diameter d5 of the hollow clad cylinder 106 is in a range about 55.3 ± 0.7 millimeters. The outer diameter d6 of the hollow clad cylinder 106 is in a range about 215 ± 2.5 millimeters. The diameter d are of the target bare optical fiber 200 is about 125 micrometer. Furthermore, the thickness tl of the fluorine-doped tube 104 is about 9.3 millimeters. The thickness t2 of the central core rod 102 etching is about 0.5 millimeters. The thickness t3 of the fluorine-doped tube 104 etching is about 30 microns. The index of refraction delta- 1 of the core region 103 of the central core rod 102 is in a range of about 0.35 to 0.37. The cladding to core ratio d2/dl of the optical fiber preform is about 2.6. The index of refraction delta-2 of the fluorine-doped tube 104 is in a range of about - 0.27 to -0.33. The alpha of the core region 103 of the central core rod 102 is in a range of about 6.0 to 7.5. In an embodiment of the present disclosure, the plurality of parameters of the second set of values may have any suitable value in the first example.

[046] In a sixth example, the plurality of parameters of the second set of values corresponding to the 215 ± 3 millimeters process of the optical fiber draw assembly 100 is as described in the paragraph. The diameter dl of the core region 103 is about 13.76 millimeters. The diameter d2 of the central core rod 102 is in a range of about 34.4 ± 0.25 millimeters. The inner diameter d3 of the fluorine-doped tube 104 is in a range of about 35.9 ± 0.7 millimeters. The outer diameter d4 of the fluorine-doped tube 104 is in a range of about 54.5 ± 0.7 millimeters. Further, the inner diameter d5 of the hollow clad cylinder 106 is in a range about 55.25 ± 0.7 millimeters. The outer diameter d6 of the hollow clad cylinder 106 is in a range about 215 ± 2.5 millimeters. The diameter d are of the target bare optical fiber 200 is about 125 micrometer. Furthermore, the thickness tl of the fluorine-doped tube 104 is about 10.5 millimeters. The thickness t2 of the central core rod 102 etching is about 0.5 millimeters. The thickness t3 of the fluorine-doped tube 104 etching is about 30 microns. The index of refraction delta- 1 of the core region 103 is in a range of about 0.35 to 0.37. The cladding to core ratio d2/dl of the optical fiber preform is about 2.5. The index of refraction delta-2 of the fluorine-doped tube 104 is in a range of about -0.27 to -0.33. The alpha of the core region 103 of the central core rod 102 is in a range of about 6.0 to 7.5. In an embodiment of the present disclosure, the plurality of parameters of the second set of values may have any suitable value in the second example.

] In a seventh example, the plurality of parameters of the second set of values corresponding to the 215 ± 3 millimeters process of the optical fiber draw assembly 100 is as described in the paragraph. The diameter dl of the core region 103 of the central core rod 102 is about 13.23 millimeters. The diameter d2 of the central core rod 102 is in a range of about 34.4 ± 0.25 millimeters. The inner diameter d3 of the fluorine-doped tube 104 is in a range of about 35.9 ± 0.7 millimeters. The outer diameter d4 of the fluorine-doped tube 104 is in a range of about 57.3 ± 0.7 millimeters. Further, the inner diameter d5 of the hollow clad cylinder 106 is in a range about 58.05 ± 0.7 millimeters. The outer diameter d6 of the hollow clad cylinder 106 is in a range about 215 ± 2.5 millimeters. The diameter d are of the target bare optical fiber 200 is about 125 micrometer. Furthermore, the thickness tl of the fluorine-doped tube 104 is about 10.7 millimeters. The thickness t2 of the central core rod 102 etching is about 0.5 millimeters. The thickness t3 of the fluorine-doped tube 104 etching is about 30 microns. The index of refraction delta- 1 of the core region 103 is in a range of about 0.35 to 0.37. The cladding to core ratio d2/dl of the optical fiber preform is about 2.6. The index of refraction delta-2 of the fluorine-doped tube 104 is in a range of about -0.27 to -0.33. The alpha of the core region 103 of the central core rod 102 is in a range of about 6.0 to 7.5. In an embodiment of the present disclosure, the plurality of parameters of the second set of values may have any suitable value in the third example. [048] In an eighth example, the plurality of parameters of the second set of values corresponding to the 215 ± 3 millimeters process of the optical fiber draw assembly 100 is as described in the paragraph. The diameter dl of the core region 103 of the central core rod 102 is about 13.76 millimeters. The diameter d2 of the central core rod 102 is in a range of about 34.4 ± 0.25 millimeters. The inner diameter d3 of the fluorine-doped tube 104 is in a range of about 35.9 ± 0.7 millimeters. The outer diameter d4 of the fluorine-doped tube 104 is in a range of about 57.3 ± 0.7 millimeters. Further, the inner diameter d5 of the hollow clad cylinder 106 is in a range about 58.1 ± 0.7 millimeters. The outer diameter d6 of the hollow clad cylinder 106 is in a range about 215 ± 2.5 millimeters. The diameter d are of the target bare optical fiber 200 is about 125 micrometer. Furthermore, the thickness tl of the fluorine-doped tube 104 is about 9.5 millimeters. The thickness t2 of the central core rod 102 etching is about 0.5 millimeters. The thickness t3 of the fluorine-doped tube 104 etching is about 30 microns. The index of refraction delta- 1 of the core region 103 of the central core rod 102 is in a range of about 0.35 to 0.37. The cladding to core ratio d2/dl of the optical fiber preform is about 2.5. The index of refraction delta-2 of the fluorine-doped tube 104 is in a range of about - 0.27 to -0.33. The alpha of the core region 103 of the central core rod 102 is in a range of about 6.0 to 7.5. In an embodiment of the present disclosure, the plurality of parameters of the second set of values may have any suitable value in the fourth example.

[049] A person skilled in the art will understand and appreciate that 30 microns etching of fluorine-doped tubes and 0.5millimeters etching of central core rods are typical number. In practice, this may be limited by machines accuracy to repeat results as etching rates change with concentration of etching agent.

[050] In an embodiment of the present disclosure, the central core rod 102 and fluorine- doped tube 104 undergoes the purging process. In general, purging of optical fiber refers to an act of removing contents or contaminating particles from hollow core of the optical fiber. This process is also called drying process. In an embodiment of the present disclosure, N₂ and Air is used to dry the central core rod 102 and fluorine-doped tube 104. In this process, the central core rod 102 and fluorine-doped tube 104 is kept in a sealed box. N₂ and Air is allowed to enter from one side of the box and exit from the other. In this manner, a positive pressure is maintained inside the sealed box. In an embodiment of the present disclosure, N₂ and Air is used at high temperature to accelerate the drying process. This process helps to remove moisture from the central core rod 102 surface and fluorine-doped tube 104 surface accumulated due to previous step of etching. The purging is crucial in optical fibers to remove contaminants from the optical fibers. The purging of the optical fiber improves performance of the optical fiber. The purging improves transmission characteristics of the optical fiber. The purging time for the central core rod 102 and fluorine-doped tube 104 is in the range of 4 hours to 24 hours. In an embodiment of the present disclosure, the optical fiber 200 has any suitable purging time.

[051] FIG. 2 illustrates a cross-sectional view of a drawn optical fiber 200, in accordance with an embodiment of the present disclosure. The drawn optical fiber 200 is a fiber used for transmitting information as light pulses from one end to another. The drawn optical fiber 200 is a thin strand of glass capable of transmitting optical signals. In addition, the drawn optical fiber 200 allows transmission of information in the form of optical signals over long distances. In an embodiment of the present disclosure, the drawn optical fiber 200 is a bend insensitive optical fiber. In general, the bend insensitive optical fiber is defined as an optical fiber which shows low sensitivity to bending. In an embodiment of the present disclosure, the drawn optical fiber 200 is a trench-assisted cladding fiber.

[052] The drawn optical fiber 200 complies with specific telecommunication standards.

The telecommunication standards are defined by International Telecommunication Union-Telecommunication (hereinafter "ITU-T"). In an embodiment of the present disclosure, the drawn optical fiber 200 is compliant with G.657 recommendation standard set by the ITU-T. In another embodiment of the present disclosure, the optical fiber 200 is compliant with G.652 recommendation standard set by the ITU-T. Furthermore, the ITU-T G.657 recommendation describes a geometrical, mechanical and transmission characteristics of a single mode optical fiber (the drawn optical fiber 200).

[053] Going further, the optical fiber 200 has a specific design. The specific design is obtained by modifying or changing the refractive index profile of the drawn optical fiber 200. In addition, the term "refractive index profile," as used herein, is the relationship between the refractive index or the relative refractive index and the radius of the fiber. In addition, the refractive index profile illustrates a change in the refractive index of the optical fiber 200 with an increase in the radius of the optical fiber 200. Also, the refractive index profile is maintained as per a desired level based on a concentration of dopants used for the production of the optical fiber 200. In general, "dopant" is defined as a trace impurity element added to change the optical properties of the optical fiber. Further, the refractive index profile is modified based on regulation of a plurality of parameters. The plurality of parameters is associated with the refractive index profile of the optical fiber 200. In an embodiment of the present disclosure, the plurality of parameters is optimized by changing a concentration of one or more dopants. The one or more dopants include but may not be limited to fluorine, germanium dioxide, phosphorous pentoxide and aluminum trioxide.

[054] The plurality of parameters includes a delta parameter, an alpha parameter, a core radius, a depressed trench's width in refractive index profile and a cladding-to-core ratio. The alpha parameter is a non-dimensional parameter that is indicative of the shape of the refractive index profile. The alpha parameter is numerically calculated through an equation given by

/ _\ a 0.5

n\ ) - n_max [ i_ 2A(r/dfl/2) ]

Here n is the refractive index at radial parameter 'r'. In addition, the radial parameter 'r' has a pre-defined value that lies in a range of about 0 to dfl/2. Furthermore, nmax is the maximum value of refractive index of the core region, dfl/2 is the radius of core (as shown in fig. 2) and delta-i (Δ is the percentage of normalized index difference defined as:

Ai= [(ni)² - (n_min)²]/2 (ni)²%

[055] In general, the delta-i parameter is the normalized index difference in percentage of the \ ^h region, where nmin is the minimum value of the refractive index. In addition, nmin is the refractive index of an inner clad of the optical fiber, ni is the maximum refractive index of the i"¹ region. For trench region (r = df2/2 to r= df3/2), therefore ¾ in this case will be the refractive index of fluorine tube.

[056] In general, the delta parameter is the normalized index difference in percentage, where nmin is the minimum value of the refractive index. In addition, nmin is the refractive index of an inner clad of the optical fiber. Further, the change in the alpha parameter results in a change in the bending losses. In general, the term "bending losses" refers to a plurality of losses during propagation of optical signal due to bending. In an embodiment of the present disclosure, an increase in the alpha parameter results in a decrease in the bending losses.

[057] The core radius is a radius of the core region of the drawn optical fiber 200. In addition, the depressed trench's width in the refractive index profile refers to the horizontal width of a trench region indicated in the refractive index profile of the drawn optical fiber 200 (discussed below in detailed description of FIG. 3). The depressed trench region is positioned around a central core rod 102 of the drawn optical fiber 200. Further, the cladding-to-core ratio (D/d ratio) is defined as a ratio of a diameter of the central core rod to a diameter of a core region present inside the core rod. Here, "D" represents the diameter of the central core rod and "d" represents the diameter of the core region.

[058] Going further, the ITU-T G.657 standard defines a plurality of optical characteristics associated with the optical fiber 200. The plurality of parameters associated with the optical fiber 200 is optimized for achieving the plurality of optical characteristics in a pre-defined range. In an embodiment of the present disclosure, the plurality of optical characteristics is achieved in the pre-defined range by altering the concentration of the one or more dopants. The plurality of optical characteristics include but may not be limited to an attenuation, zero dispersion wavelength, zero dispersion slope, cable cutoff wavelength, mode field diameter, bending losses and effective area.

[059] In general, the attenuation is a loss of optical power as light travels inside the core region of the drawn optical fiber 200. The attenuation in the drawn optical fiber 200 is based on a plurality of factors. The plurality of factors includes but may not be limited to absorption, scattering, bending losses and the like. Moreover, the absorption and the scattering of the light in the drawn optical fiber 200 are intrinsic in nature. Also, the attenuation due to the bending losses of the drawn optical fiber 200 is extrinsic in nature. Further, the zero dispersion wavelength (hereinafter as "ZD wavelength") is a wavelength at which the value of dispersion coefficient is zero. In general, ZD wavelength is the wavelength at which material dispersion and waveguide dispersion cancel one another.

[060] The dispersion slope of the drawn optical fiber 200 is the rate of change of dispersion with respect to the wavelength. In addition, the zero dispersion slope related to the drawn optical fiber 200 is the slope at zero dispersion wavelength. The mode field diameter (hereinafter as "MFD") of the drawn optical fiber 200 is a section of fiber where most of the light energy travels. In general, MFD defines a section or area of the drawn optical fiber 200 in which the optical signals travel. The MFD is an expression of distribution of the optical power. The effective area of the drawn optical fiber 200 corresponds to an optical effective area at a wavelength of 1550 nm. The drawn optical fiber 200 transmits a single mode of optical signal above a pre-defined cutoff wavelength known as cable cutoff wavelength. In general, cutoff wavelength is defined as the wavelength above which any given mode cannot propagate.

[061] Going further, drawn the optical fiber 200 is made up of a plurality of regions of transparent material generally distributed with axial symmetry around a central longitudinal axis 202a of the optical fiber 200. The skilled artisan will appreciate that the central longitudinal axis 202a is not a physical feature; rather, it is a reference line at a geometrical center of the drawn optical fiber 200. The drawn optical fiber 200 includes a fiber core region 204, a fiber first cladding region 206, a fiber trench region 208 and a fiber second cladding region 210. In addition, the fiber core region 204, the fiber first cladding region 206, the fiber trench region 208 and the fiber second cladding region 210 are concentrically arranged.

[062] The plurality of regions associated with the drawn optical fiber 200 is defined by index of refraction which need not be constant within each region. The index of refraction of the fiber core region 204 varies with the alpha parameter (as stated in above paragraph). In an embodiment of the present disclosure, the index of refraction of the fiber core region 204 is nl and the index of refraction of the fiber first cladding region 206 is n2. In an embodiment of the present disclosure, the index of refraction of the fiber trench region 208 is n3 and the index of refraction of the fiber second cladding region 210 is n4.

[063] The fiber core region 204 is defined as a region around the central longitudinal axis

202a of the drawn optical fiber 200. In general, the fiber core region 204 is defined as the region around the central longitudinal axis 202a of the drawn optical fiber 200 through which light transmits. The fiber core region 204 is extended radially outside from the geometrical center of the drawn optical fiber 200. Also, the fiber core region 204 has a pre-defined fiber core diameter. The fiber core diameter associated with the central core rod 102 is selected to obtain the plurality of optical characteristics in the predefined range. The core diameter associated with the fiber core region 204 is denoted by "dfl" (as shown in fig. 2).

[064] Further, the fiber first cladding region 206 circumferentially surrounds the fiber core region 204 of the drawn optical fiber 200. In an embodiment of the present disclosure, the index of refraction n(x) of the fiber core region 204 is higher than the index of refraction n2 of the fiber first cladding region 206. Moreover, the fiber core region 204 and the fiber first cladding region 206 together form the central core rod. In general "central core rod" refers to a pre fabricated part of the drawn optical fiber 200. In addition, the central core rod includes the fiber core region 204 and the fiber first cladding region 206.

[065] Furthermore, the central core rod 102 associated with the drawn optical fiber 200 has a pre-defined rod diameter. The rod diameter associated with the central core rod 102 is selected to obtain the plurality of optical characteristics in the pre-defined range. The pre-defined rod diameter is denoted by "d2" (as shown in FIG. 1). Furthermore, a predefined value of cladding-to-core ratio is required to obtain improved values of the plurality of optical characteristics.

[066] A plurality of manufacturing techniques is adopted for manufacturing the central core rod. The manufacturing of the central core rod associated with the optical fiber 200 is performed by diffusing a pre-defined concentration of dopants in a pre-defined pattern. In an embodiment of the present disclosure, germanium dioxide and fluorine are used as dopants. The plurality of manufacturing techniques includes but may not be limited to modified chemical vapor deposition (MCVD), outside vapor deposition (OVD) and vapor axial deposition (VAD).

[067] Further, the central core rod is surrounded by the fiber trench region 208. In general, "trench region" refers to a depressed cladding region of low index of refraction. The index of refraction n3 of the fiber trench region 208 is lower than the index of refraction n2 of the fiber first cladding region 206. In an embodiment of the present disclosure, the fiber trench region 208 is obtained by over-cladding the central core rod with a fluorine doped jacket tube and controlling the amount of fluorine. In another embodiment of the present disclosure, the fiber trench region 208 is obtained by introducing one or more holes in the fiber first cladding region 206. Moreover, the fiber trench region 208 is extended radially outwards between the fiber first cladding region 206 and the fiber second cladding region 210 of the drawn optical fiber 200. The diameter associated with the fiber trench region 208 is denoted by "df3" (as shown in FIG. 2).

[068] The central core rod and the fiber trench region 208 together form a core rod assembly (as shown in FIG. 1). In general "core rod assembly" refers to a prefabricated part of the drawn optical fiber 200 which includes the fiber core region 204, the fiber first cladding region 206 and the fiber trench region 208. The fiber trench region 208 of the drawn optical fiber 200 is defined based on one or more trench specifications. The one or more trench specification includes but may not be limited to the trench width and trench depth. Moreover, the plurality of optical characteristics of the drawn optical fiber 200 is modified and improved based on the optimization of the one or more trench specifications. For example, increase in the value of depressed trench's width of the drawn optical fiber 200 results in a decrease in the bending losses.

[069] Going further, the fiber trench region 208 is surrounded by the fiber second cladding region 210. The fiber second cladding region 210 concentrically surrounds the fiber trench region 208. In an embodiment of the present disclosure, the index of refraction n4 of the fiber second cladding region 210 is higher than the index of refraction n3 of the fiber trench region 208. In an embodiment of the present disclosure, the fiber second cladding region 210 extends radially outward from the fiber trench region 208. The diameter associated with the fiber second cladding region 210 is denoted by "df4" (as shown in FIG. 1). The second fiber cladding region 210 is formed by over-cladding the core rod assembly with a hollow clad cylinder in the presence of heat. In an embodiment of the present disclosure, the hollow clad cylinder is a quartz glass cylinder. Moreover, the hollow clad cylinder has a pre-defined longitudinal length. In an embodiment of the present disclosure, the pre-defined longitudinal length of the hollow clad cylinder is 3m. Also, the hollow clad cylinder has a pre-defined cross-sectional diameter. In an embodiment of the present disclosure, the pre-defined cross-sectional diameter of the hollow clad cylinder lies in a range of about 195 millimeters to 220 millimeters. [070] The core rod assembly and the hollow clad cylinder together form an optical preform assembly. In general, the optical fiber preform assembly is a large cylindrical body of glass having a core structure and a cladding structure. In addition, the optical preform assembly refers to a rod through which the drawn optical fiber 200 of required diameter and length is drawn.

[071] The optical fiber preform assembly is manufactured by adopting a plurality of preform yielding techniques. The plurality of preform manufacturing techniques includes but may not be limited to rod-in-tube method (hereinafter as "RIT") and rod-in-cylinder method (hereinafter as "RIC"). In an embodiment of the present disclosure, the optical fiber preform assembly is manufactured by utilizing the RIC method. In RIC method, the optical fiber preform is manufactured by inserting the core rod assembly inside the hollow clad cylinder. In an embodiment of the present disclosure, the optical fiber preform assembly obtained from the RIC method is directly drawn to yield the optical fiber 200. In another embodiment of the present disclosure, the optical fiber preform assembly obtained from the RIC method is stretched to form a plurality of solid preform rods of smaller diameter. The plurality of solid preform rods are further drawn to yield optical fiber 200.

[072] FIG. 3 illustrates the refractive index profile 300 of the optical fiber 200 along a transverse axis 202b, in accordance with an embodiment of the present disclosure. In an embodiment of the present disclosure, the transverse axis 202b passes through the geometrical center of the drawn optical fiber 200 and is perpendicular to the central longitudinal axis 202a of the drawn optical fiber 200. The skilled artisan will appreciate that the transverse axis 202b (shown in FIG. 2) is not a physical feature; rather, it is a reference line at a geometrical center of the drawn optical fiber 200. It may be noted that to explain a graphical appearance of the refractive index profile 300, references will be made to the structural elements of the optical fiber 200.

[073] The refractive index profile 300 illustrates a relationship between the refractive index of the drawn optical fiber 200 and the radius of the optical fiber 200 (as stated above in the detailed description of the FIG. 2). The refractive index profile 300 describes a graphical plot of a variation of refractive index of each region as a function of radius measured from the central longitudinal axis 202a. In an embodiment of the present disclosure, the graphical plot refractive index profile 300 is shown along the transverse axis 202b.

[074] In an embodiment of the present disclosure, the refractive index is shown on ordinate axis or y-axis and the radius of the drawn optical fiber 200 is shown on abscissa or x-axis. The refractive index on the ordinate axis is represented in the form of the delta parameter (as shown in FIG. 3). Further, the graphical plot of the refractive index profile 300 corresponds to the fiber core region 204, the fiber first cladding region 206, the fiber trench region 208 and the fiber second cladding region 210 of the drawn optical fiber 200. Each refractive index value corresponding to each region is plotted against radius of each region. Further, the refractive index profile 300 is plotted against a first pre-defined diameter dl of fiber draw assembly 100, a second pre-defined diameter d2 of fiber draw assembly 100, a third pre-defined diameter d3 of fiber draw assembly 100, a fourth predefined diameter d4 of fiber draw assembly 100, a fifth predefined diameter d5 of fiber draw assembly 100 and sixth predefined diameter d6 of fiber draw assembly 100 on the transverse axis 202b. The fiber core region 204 extends from an origin associated with the graphical plot to the first pre-defined radius dl/2 of fiber draw assembly 100. The diameter of the fiber core region 204 of the optical fiber 200 after it is drawn from the optical fiber draw assembly 100 is dfl (as shown in fig. 2). The fiber first cladding region 206 extends from the first pre-defined radius dl/2 of the fiber draw assembly 100 to the second pre-defined radius d2/2 fiber draw assembly 100. The diameter of the fiber first cladding region 206 of the optical fiber 100 after it is drawn from the optical fiber draw assembly 100 is df2 (as shown in fig. 2). The fiber trench region 208 extends from the second pre-defined radius d2/2 to the third pre-defined radius d4/2. The diameter of the fiber trench region 208 of the optical fiber 100 after it is drawn from the optical fiber draw assembly 100 is df3 (as shown in fig. 2). In addition, the second fiber cladding region 210 extends from the third pre-defined radius d4/2 to the fourth pre-defined radius d6/2. The diameter of the fiber first cladding region 210 of the optical fiber 100 after it is drawn from the optical fiber draw assembly 100 is df4 (as shown in fig. 2).

[075] Going further, the refractive index profile 300 is formed by controlling the plurality of optical parameters (as discussed above in detailed description of FIG. 2) associated with the drawn optical fiber 200. In an embodiment of the present disclosure, the plurality of optical parameters is controlled to obtain the plurality of optical characteristics (as discussed above in detailed description of FIG. 2) in the desired range. In an embodiment of the present disclosure, the alpha parameter, the cladding-to-core ratio and the delta parameters are controlled to obtain the refractive index profile 300.

[076] The shape of the refractive index profile 300 is maintained by optimizing and controlling the alpha parameter (as discussed above in detailed description of FIG. 2). In an embodiment of the present disclosure, the alpha parameter for the refractive index profile 300 of the drawn optical fiber 200 lies in a range of 6 and 7.5. Further, the drawn optical fiber 200 has a pre-defined value of the cladding-to-core ratio (as discussed above in detailed description of FIG. 2). In an embodiment of the present disclosure, the predefined value of cladding-to-core ratio lies in a range of 2.4 - 2.8.

[077] The delta parameter is optimized and controlled to minimize the bending losses and obtain the optical fiber 200 of desired properties. The delta parameter associated with the fiber core region 204 of the drawn optical fiber 200 is denoted by deltal (Δ1) (as shown in FIG. 3). Also, the delta parameter associated with the trench region 208 of the optical fiber 200 is denoted by delta2 (Δ2) (as shown in FIG. 3). Moreover, the delta parameter delta- 1(Δ1) associated with the fiber core region 204 of the drawn optical fiber 200 is positive. In addition, the delta parameter delta-2 (Δ2) associated with the fiber trench region 208 of the drawn optical fiber 200 is negative. In an embodiment of the present disclosure, the delta parameter associated with the fiber trench region 208 lies in a predefined range of about -0.27 and -0.33. Further, the refractive index profile 300 has a pre-defined value of depressed trench's width associated with the fiber trench region 208. In an embodiment of the present disclosure, the value of the depressed trench's width associated with the fiber trench region 208 lies in a pre-defined range of about 4 microns to 7 microns.

[078] On optimizing and controlling the plurality of optical parameters associated with the drawn optical fiber 200 standard values of the plurality of optical characteristics is achieved. In an embodiment of the present disclosure, the plurality of parameters is controlled to minimize the attenuation and bending losses. In addition, the plurality of parameters is controlled to achieve MFD, ZD wavelength and fiber cutoff wavelength within the standard values range. The standard values of the plurality of optical characteristics are decided based on ITU-T G.657 recommendation. The MFD (as discussed above in detailed description of FIG. 2) of the drawn optical fiber 200 obtained has a pre-defined standard value. In an embodiment of the present disclosure, the predefined standard value of MFD lies in a range of about 8.2 μπι to 9 μηι. The ZD wavelength (as discussed above in detailed description of FIG. 2) of the drawn optical fiber 200 obtained has a pre-defined standard value. In an embodiment of the present disclosure, the pre-defined standard value of ZD wavelength lies in a range of about 1300 nm to 1324 nm. Furthermore, the bending losses (as stated above in detailed description of FIG. 2) associated with the drawn optical fiber 200 has a pre-defined standard value. In an embodiment of the present disclosure, the pre-defined standard value of bending losses at 15 mm diameter bend is in a range of about 0.2 dB/turn and 0.5 dB/turn for the wavelength of 1550 nanometers. Moreover, the cable cutoff wavelength (as described above in detailed description of FIG. 2) has a pre-defined value less than 1260 nanometers.

[079] The below mentioned examples corresponds to the properties and characteristics of the drawn optical fiber 200 form the optical fiber draw assembly 100.

[080] In example 1, the drawn optical fiber 200 with the alpha parameter value of 6.0 is explained. The cladding-to-core value for the drawn optical fiber 200 was set to be approximately 2.5 in case 1 and approximately 2.6 in case 2 respectively. For case 1, the maximum value of delta parameter was found to be 0.37. In addition, the minimum value of delta parameter for case 1 was found to be 0.35. For case 1 and delta parameter 0.37 the MFD value was observed to be 8.4 μπι and the fiber cutoff wavelength was observed to be 1270 nm. Also, the ZD wavelength was observed to be 1318 nm and the bending loss at 15 mm diameter bend was observed to be 0.045 dB / turn for 1550 nm. For case 1 and delta parameter 0.35 the MFD value was observed to be 8.6 μπι and the fiber cutoff wavelength was observed to be 1230 nm. Also, the ZD wavelength was observed to be 1320 nm and the bending loss at 15 mm diameter bend was observed to be 0.045 dB / turn for 1550 nm. For case 2, the maximum value of delta parameter was found to be 0.37. In addition, the minimum value of delta parameter for case 2 was found to be 0.35. For case 2 and delta parameter 0.37 the MFD value was observed to be 8.45 μπι and the fiber cutoff wavelength was observed to be 1280 nm. Also, the ZD wavelength was observed to be 1319 nm and the bending loss at 15 mm diameter bend was observed to be 0.037 dB / turn for 1550 nm. For case 2 and delta parameter 0.35, the MFD value was observed to be 8.45 μπι and the fiber cutoff wavelength was observed to be 1240 nm. Also, the ZD wavelength was observed to be 1321 nm and the bending loss at 15 mm diameter bend was observed to be 0.037 dB / turn for 1550 nm.

[081] In example 2, the drawn optical fiber 200 with the alpha parameter value of 7.5 is explained. The cladding-to-core value for the drawn optical fiber 200 was set to be approximately 2.5 in case 3 and approximately 2.6 in case 4 respectively. For case 3, the maximum value of delta parameter was found to be 0.37. In addition, the minimum value of delta parameter for case 3 was found to be 0.35. For case 3 and delta parameter 0.37 the MFD value was observed to be 8.6 μπι and the fiber cutoff wavelength was observed to be 1280 nm. Also, the ZD wavelength was observed to be 1313 nm and the bending loss at 15 mm diameter bend was observed to be 0.025 dB / turn for 1550 nm. For case 3 and delta parameter 0.35 the MFD value was observed to be 8.65 μπι and the fiber cutoff wavelength was observed to be 1240 nm. Also, the ZD wavelength was observed to be 1316 nm and the bending loss at 15 mm diameter bend was observed to be 0.025 dB / turn for 1550 nm. For case 4, the maximum value of delta parameter was found to be 0.37. In addition, the minimum value of delta parameter for case 4 was found to be 0.35. For case 4 and delta parameter 0.37 the MFD value was observed to be 8.45 μπι and the fiber cutoff wavelength was observed to be 1290 nm. Also, the ZD wavelength was observed to be 1314 nm and the bending loss at 15 mm diameter bend was observed to be 0.02 dB / turn for 1550 nm. For case 4 and delta parameter 0.35 the MFD value was observed to be 8.45 μπι and the fiber cutoff wavelength was observed to be 1250 nm. Also, the ZD wavelength was observed to be 1317 nm and the bending loss at 15 mm diameter bend was observed to be 0.02 dB / turn for 1550 nm. Kindly verify the above stated values associated with Example 2.

[082] FIG 4 illustrates a draw length - attenuation profile of the drawn optical fiber 200, in accordance with an embodiment of the present disclosure. The curve 402 in the profile 400 corresponds to the standard specification. The curve 404 in the profile 400 corresponds to the offline RIC process for the drawn optical fiber 200. The curve 406 in the profile 400 corresponds to the online RIC process for the drawn optical fiber 200. In an embodiment of the present disclosure the draw length of the drawn optical fiber 200 is in the range of about 7000 fiber kilometer - 8000 fiber kilometer.

[083] FIG 5 illustrates a draw length - OH loss profile of the drawn optical fiber 200, in accordance with an embodiment of the present disclosure. The curve 502 represents the draw length - OH loss of theprofile500 corresponds to the standard specification. The curve 504 represents the draw length - OH loss of theprofile500 corresponds to the offline RIC process for the drawn optical fiber 200. The curve 506 represents the draw length - OH loss of theprofile500 corresponds to the online RIC process for the drawn optical fiber 200.

[084] Going further, the present disclosure provides numerous advantages over the prior art. The present disclosure provides an optical fiber draw assembly to draw a bend- insensitive optical fiber having the plurality of optical characteristics well below the standard limit recommended by ITU-T. The present disclosure provides the optical fiber draw assembly to draw a bend-insensitive optical fiber with low attenuation and anti- bending properties. In addition, the present disclosure provides the optical fiber draw assembly to draw the optical fiber possessing excellent bending performance along with improved optical characteristics following the ITU-T G.657 recommendations. Furthermore, the optical fiber drawn has low sensitivity to environment and handling. Moreover, the method of manufacturing the optical fiber involves a complete utilization of the optical preform assembly without attenuation failures which increases the optical fiber yielding and lowers the cost of production.

[085] The foregoing descriptions of specific embodiments 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 embodiments 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 embodiments 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.

] While several possible embodiments 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 embodiment should not be limited by any of the above- described exemplary embodiments.

Claims

STATEMENT OF CLAIMS We claim:

1. An optical fiber draw assembly (100) comprising: a central core rod (102) longitudinally extending from a first end (114) to a second end (116) in a vertical direction, wherein the first end (114) and the second end (116) are associated with the optical fiber draw assembly (100), wherein the first end (114) is positioned vertically above the second end (116), wherein the central core rod (102) has a diameter d2, wherein the central core rod (102) comprising: a core region (103) longitudinally extending in the vertical direction, wherein the core region (103) has a diameter dl, wherein the core region (103) has an index of refraction delta- 1 ; and a first cladding region (105) longitudinally extending in the vertical direction, wherein the core region (103) and the first cladding region (105) collectively forms the central core rod (102); a fluorine-doped tube (104) longitudinally extending from the first end (114) to the second end (116) in the vertical direction, wherein the fluorine-doped tube (104) has an inner diameter d3, wherein the fluorine-doped tube (104) has an outer diameter d4, wherein the fluorine-doped tube (104) has a thickness tl, wherein the fluorine-doped tube (104) has an index of refraction delta-2, wherein the central core rod (102) is placed inside the fluorine-doped tube (104) and wherein the central core rod (102) and the fluorine-doped tube (104) collectively forms a core rod assembly (118); and

a hollow clad cylinder (106), wherein the hollow clad cylinder (106) has an inner diameter d5, wherein the hollow clad cylinder (106) has an outer diameter d6, wherein the core rod assembly (118) is sheathed inside the hollow clad cylinder (106), wherein the core rod assembly (118) has a geometrical center, wherein the hollow clad cylinder (106) has a geometrical center, wherein the geometrical center of the core rod assembly (118) and the geometrical center of the hollow clad cylinder (106) coincides with each other in the optical fiber draw assembly (100), wherein the core rod assembly (118) and the hollow clad cylinder (106) collectively forms an optical fiber preform assembly (120), wherein an optical fiber preform is fabricated at two different set of values for a plurality of parameters, wherein a first set of values for the plurality of parameters corresponds to a 199 millimeters to 205 millimeters process of the optical fiber draw assembly (100), wherein the plurality of parameters for the first set of values comprises the central core rod (102) diameter d2, the core region (103) diameter dl, the fluorine- doped tube (104) inner diameter d3, the fluorine-doped tube (104) outer diameter d4,the fluorine-doped tube (104) thickness tl,the hollow clad cylinder (106) inner diameter d5, the hollow clad cylinder (106) outer diameter d6,the index of refraction delta- 1 for core region (103), the index of refraction delta-2 for fluorine-doped tube (104),

wherein for the first set of values, the central core rod (102) diameter d2 is in the range of about 31.5 millimeters to 32.5 millimeters, the core region (103) diameter dl is in the range of about 12.31 millimeters to 12.8 millimeters, the fluorine-doped tube (104) inner diameter d3 is in the range of about 33.5 ± 0.7 millimeters, the fluorine-doped tube (104) outer diameter d4 is in the range of about 49.5 ± 0.7 millimeters and 53.5 ± 0.7 millimeters, the fluorine-doped tube (104) thickness tl is in the range of about 8millimeters and lOmillimeters, the hollow clad cylinder (106) inner diameter d5 is in the range of about 51.4 ± 0.7 millimeters and 54.5 ± 0.7 millimeters, the hollow clad cylinder (106) outer diameter d6 is in the range of about 201 ± 2 millimeters, the index of refraction delta- 1 for core region (103) is in the range of about 0.35 and 0.37, the index of refraction delta-2 for fluorine-doped tube (104) is in the range of about -0.27 and -0.33, wherein a second set of values for a plurality of parameters corresponds to a 215 ± 3 millimeters process of the optical fiber draw assembly (100), wherein the plurality of parameters for the second set of values comprises the central core rod (102) diameter d2, the core region (103) diameter dl, the fluorine-doped tube (104) inner diameter d3, the fluorine-doped tube (104) outer diameter d4,the fluorine-doped tube (104) thickness tl, the hollow clad cylinder (106) inner diameter d5, the hollow clad cylinder (106) outer diameter d6, the index of refraction delta-1 for the core region (103), the index of refraction delta-2 for the fluorine-doped tube (104), and wherein for the second set of values, the central core rod (102) diameter d2 is in the range of about 34.4 ± 0.25 millimeters, the core region (103) diameter dl is in the range of about 13.23 millimeters to 13.76 millimeters, the fluorine-doped tube (104) inner diameter d3 is in the range of about 35.9 ± 0.7 millimeters, the fluorine-doped tube (104) outer diameter d4 is in the range of about 54.5 ± 0.7 millimeters and 57.3 ± 0.7 millimeters, the fluorine-doped tube (104) thickness tl is in the range of about 9.3 millimeters and 10.7 millimeters, the hollow clad cylinder (106) inner diameter d5 is in the range of about 55.3 ± 0.7 millimeters and 58.1 ± 0.7 millimeters, the hollow clad cylinder (106) outer diameter d6 is in the range of about 215 ± 2.5 millimeters, the index of refraction delta-1 of the core region (103) is in the range of about 0.35 and 0.37, the index of refraction delta-2 of the fluorine-doped tube (104) is in the range of about -0.27 and -0.33.

2. The optical fiber draw assembly (100) as claimed in claim 1, wherein the optical fiber draw assembly (100) comprising a holding tube (110), wherein the central core rod (102) is coupled to the holding tube (110) at the first end (114) of the optical fiber draw assembly (100).

3. The optical fiber draw assembly (100) as claimed in claim 1, wherein the optical fiber draw assembly comprising a handling tube (112), wherein the hollow clad cylinder (106) is coupled to the handling tube (112) at the first end (114) of the optical fiber draw assembly (100).

4. The optical fiber draw assembly (100) as claimed in claim 1, wherein the optical fiber draw assembly (100) comprising a spacer (108), wherein the spacer (108) is placed between the core rod assembly (118) and the holding tube (110), wherein the spacer (108) is a solid spacer, wherein the spacer (108) is a slotted spacer.

5. The optical fiber draw assembly (100) as claimed in claim 1, wherein an optical fiber (200) is drawn from the optical fiber draw assembly (100), wherein the optical fiber (200) has a core region (204), wherein the core region (204) has an alpha parameter, wherein the alpha parameter is in a range of about 6 and 7.5 for the optical fiber (200) drawn in both the processes corresponds to 199 millimeters to 205 millimeters and 215 ± 3 millimeters.

6. The optical fiber draw assembly (100) as claimed in claim 1, wherein the central core rod (102) is treated with an etching process, wherein the etching process shed a thickness t2 from the central core rod (102), wherein the thickness t2 is about 0.5 millimeters in both the processes corresponds to 199 millimeters to 205 millimeters and 215 ± 3 millimeters.

7. The optical fiber draw assembly (100) as claimed in claim 1, wherein the fluorine-doped tube (104) is treated with an etching process, wherein the etching process shed the thickness t3 from the fluorine-doped tube (104), wherein the thickness t3 is about 30 microns in both the processes corresponds to 199 millimeters to 205 millimeters and 215 ± 3 millimeters.

8. The optical fiber draw assembly (100) as claimed in claim 1, wherein the optical fiber (200) drawn has a bare diameter of about 125 micrometre.

9. The optical fiber draw assembly (100) as claimed in claim 1, wherein the optical fiber draw assembly (100) has a cladding to core ratio d2/dl measured before the etching process, wherein the cladding to core ratio d2/dl is in a range of about 2.5 and 2.6 in both the processes corresponds to 199 millimeters to 205 millimeters and 215 ± 3 millimeters.

10. The optical fiber draw assembly (100) as claimed in claim 1, wherein the optical fiber (200) draw is in the range of about 7000 fiber kilometer - 8000 fiber kilometer in both the processes corresponds to 199 millimeters to 205 millimeters and 215 ± 3 millimeters.