Description:TECHNICAL FIELD
[1] The present disclosure relates generally to optical fibers, and, more
particularly, to a method for drawing an optical fiber that have tight tolerances for
long-term diameter variation and short-term diameter variation of the optical fiber.
BACKGROUND
[2] Inert gases are commonly used in the process of drawing an optical fiber.
In this process, a preform having a core and cladding materials is heated in a
furnace and then drawn into a long, thin optical fiber. During the drawing process,
the preform is heated to a high temperature so that it softens and can be drawn
into an optical fiber. However, the high temperature can also cause unwanted
chemical reactions and impurities in the glass material. To prevent this, one or
more inert gases are used. A few inert gases with low atomic number can be more
buoyant and easier to handle, while being expensive. Other inert gases may be
less buoyant but cheaper for large scale commercial production. The choice of
which gas to use may depend on factors such as cost, availability, and the specific
requirements of the manufacturing process.
[3] While there are number of ways to control diameter variation of an optical
fiber. For example, US20010047667A1 discloses a fiber drawing method that
maintains a constant diameter of the optical fiber even in the presence of preform
irregularities by adjusting the flow rate of Argon and Helium near the heated part
of the preform. US7197898B2 discloses a diameter-controlled optical fiber
drawing process that maintains a constant diameter of the optical fiber by
measuring the diameter of the uncoated fiber and the preform before melting and
adjusting the drawing speed and preform feed speed accordingly. CN105271706B
discloses a fiber drawing equipment that uses high-pressure argon gas to replace
high-cost helium inside the furnace, reducing fiber diameter variation.
US5073179A discloses a drawing process for producing an optical fiber from a
preform and controlling fiber diameter during the drawing process by measuring
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the diameter of the uncoated fiber and adjusting drawing rate and temperature
accordingly.
[4] The prior art references fall short of effectively address the problem of
long-term diameter variation and short-term diameter variation of the optical fiber.
Thus, there is a need of a technology that overcomes the above stated
disadvantages of conventional methods.
OBJECTIVE OF THE DISCLOSURE
[5] A primary object of the present disclosure is to provide a method for
drawing an optical fiber.
[6] Another object of the present disclosure is to provide a method that
facilitate in reducing a short-term Bare Fiber Diameter (BFD) variation of a bare
optical fiber during optical fiber drawing process.
[7] Another object of the present disclosure is to provide a method that
facilitate in reducing a long-term BFD variation of the bare optical fiber during
optical fiber drawing process.
SUMMARY
[8] In an aspect of the present disclosure, a method for drawing a bare optical
fiber from a cylindrical glass preform in a furnace chamber is disclosed. The
method having steps of (i) inserting the cylindrical glass preform near a first end
of the furnace chamber, (ii) melting the cylindrical glass preform in presence of
first inert gas and second inert gases inside the furnace chamber to draw the bare
optical fiber such that the first inert gas and the second inert gas are in a
predefined ratio. The predefined ratio of volume of the first inert gas and the
second inert gas is in a range of 0.3 to 5, and (iii) cooling the bare optical fiber
such that a short-term Bare Fiber Diameter (BFD) variation of the bare optical
fiber is less than 0.1 micrometers (µm) from a mean diameter of the bare optical
fiber.
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[9] In another aspect of the present disclosure, a method for drawing a bare
optical fiber from a cylindrical glass preform in a furnace chamber is disclosed.
The method having steps of (i) inserting the cylindrical glass preform near a first
end of the furnace chamber at a predefined feed speed, (ii) adjusting the
predefined feed speed based on capstan speed of a capstan in one or more steps
such that each step is less than 0.3 Millimetre Per Minute (mmpm), (iii) melting
the cylindrical glass preform in presence of first inert gas and second inert gases
inside the furnace chamber to draw the bare optical fiber, and (iv) cooling the bare
optical fiber such that a mean diameter of the bare optical fiber is maintained at a
predefined diameter.
[10] These and other aspects herein will be better appreciated and understood
when considered in conjunction with the following description and the
accompanying drawing. It should be understood, however, that the following
descriptions are given by way of illustration and not of limitation. Many changes
and modifications may be made within the scope of the invention herein without
departing from the spirit thereof.
BRIEF DESCRIPTION OF DRAWINGS
[11] The following detailed description of the preferred aspects of the present
disclosure will be better understood when read in conjunction with the appended
drawings. The present disclosure is illustrated by way of example, and not limited
by the accompanying figures, in which like references indicate similar elements.
[12] FIG. 1A illustrates a cross-sectional view of an apparatus.
[13] FIG. 1B illustrates a block diagram of a system.
[14] FIG. 2 illustrates an optical fiber drawing process in presence of a first
inert gas and a second inert gas.
[15] FIG. 3A illustrates a graph that represents a short-term variation and a
long-term variation of a Bare Fiber Diameter (BFD) of a bare optical fiber.
[16] FIG. 3B illustrates a graph that represents the long-term variation of the
BFD of the bare optical fiber.
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[17] FIG. 3C illustrates a graph that represents the short-term variation of the
BFD of the bare optical fiber.
[18] FIG. 4 illustrates a flowchart of a process of drawing a bare optical fiber
during the short-term variation of the BFD.
[19] FIG. 5 illustrates a flowchart of a process of drawing a bare optical fiber
during the long-term variation of the BFD.
[20] FIG. 6 illustrates another flowchart of a process of drawing the bare
optical fiber during the short-term and long-term diameter variation of the BFD.
[21] FIG. 7 illustrates a gas flow diagram for injecting the first and second inert
gases (such as Helium (He) and Argon (Ar), respectively) inside a furnace
chamber of the apparatus of FIG. 1A.
DETAILED DESCRIPTION
[22] 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.
[23] Furthermore, it will be clear that the invention is not limited to these
alternatives only. Numerous modifications, changes, variations, substitutions and
equivalents will be apparent to those skilled in the art, without parting from the
scope of the invention.
[24] The accompanying drawing is used to help easily understand various
technical features and it should be understood that the alternatives presented
herein are not limited by the accompanying drawing. 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
drawing. 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.
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[25] The proposed invention provides a method for drawing a bare optical fiber,
where a short-term Bare Fiber Diameter (BFD) variation and a long-term BFD
variation of the bare optical fiber is controlled within ±0.1 micrometres (µm)
band.
Definitions:
[26] As used herein the term “optical fiber” is referred to as a light guiding
medium that provides high-speed data transmission. The optical fiber comprises a
core and a cladding. The light moving through the core of the optical fiber relies
upon the principle of total internal reflection, where the core has a higher
refractive index than the refractive index of the cladding of the optical fiber.
[27] The term “bare optical fiber” as used herein is referred to as a type of
optical fiber without any coating or cladding.
[28] The term “core” of an optical fiber as used herein is referred to as the inner
most cylindrical structure present in the center of the optical fiber, that is
configured to guide the light rays inside the optical fiber.
[29] The term “cladding” of an optical fiber as used herein is referred to as one
or more layered structure covering the core of an optical fiber from the outside,
that is configured to possess a lower refractive index than the refractive index of
the core to facilitate total internal reflection of light rays inside the optical fiber.
Further, the cladding of the optical fiber may include an inner cladding layer
coupled to the outer surface of the core of the optical fiber and an outer cladding
layer coupled to the inner cladding from the outside.
[30] The term “cylindrical glass preform” as used herein is referred to as a
rod/solid body of glass that is melted and drawn to form an optical fiber. The
cylindrical glass preform is designed to have the desired refractive index profile
for the optical fiber.
[31] The term “furnace chamber” as used herein is referred to as a
high-temperature chamber used for melting the cylindrical glass preform and
drawing the optical fiber. To start the drawing, the cylindrical glass preform is
lowered into the furnace chamber. Generally, the drawing region is heated to
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about 1,900° C, where the glass softens and elongates with a teardrop-shaped drip
pulling the optical fiber downward.
[32] The term “neckdown region” as used herein referred to as a bottom point
of the cylindrical glass preform which is formed after melting the cylindrical glass
preform for pulling the bare optical fiber form that point.
[33] The term "inert gas” as used herein is referred to as a gas that does not
undergo chemical reactions under normal conditions. In this method, a first inert
gas (such as Helium (He)) and a second inert gas (such as Argon (Ar)) are used in
a predefined ratio to create an atmosphere inside the furnace chamber for the
melting process. The inert gas is passed inside the furnace with a pressure slightly
above atmospheric pressure with a major purpose to prevent the atmospheric air
entry into the furnace chamber.
[34] The term “predefined ratio” as used herein referred to as a specific ratio of
the volume of the first inert and second inert gases (for example Helium (He) and
Argon (Ar) respectively) that is chosen before the process begins. The predefined
ratio in this method of the present disclosure is in the range of 0.3 to 5.
[35] The term “short-term Bare Fiber Diameter (BFD) variation” as used herein
is referred to as a measure of the tolerance level of the diameter of the bare optical
fiber. The short-term BFD variation is defined as a very rapid and random
occurrence of diameter variation of the bare optical fiber within small time scales.
The method of the present disclosure aims to keep the BFD variation less than 0.1
micrometers (µm) from the mean diameter of the bare optical fiber to ensure
consistent performance.
[36] The term “long-term Bare Fiber Diameter (BFD) variation” as used herein
is referred to as a slow variation in the diameter of the optical fiber that occurs at a
periodic interval at longer time scales. The long-term BFD variation in bare
optical fiber is caused by frequent and higher variation in feed speed.
[37] The term “cooling” as used herein is referred to as a process of lowering
the temperature of the bare optical fiber after it has been drawn. This is necessary
to stabilize the optical fiber's structure and properties.
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[38] FIG. 1A illustrates a cross-sectional view of an apparatus 100. The
apparatus 100 may be configured to control a Bare Fiber Diameter (BFD)
variation during an optical fiber draw process. Specifically, the apparatus 100 may
be configured to control the BFD variation within ±0.1 µm from the mean
diameter of the bare optical fiber 118 while melting a cylindrical glass preform
102 in presence of first and second inert gases and by changing a feed speed by a
small amount based on a change in a capstan speed to control the BFD variation.
In some aspects of the present disclosure, the cylindrical glass preform 102 may
be made up of very high purity (5N) chemicals that results into best quality of
optical fibers. Specifically, the cylindrical glass preform 102 may be utilized to
make the optical fibers that can potentially transmit data at high speed.
[39] As illustrated, the apparatus 100 may have a furnace chamber 104, a
handle holder 106, and a handle 108. Specifically, the handle 108 may have a
proximal end 108a and a distal end 108b such the cylindrical glass preform 102 is
attached to the proximal end 108a of the handle 108. Further, the handle 108 may
be held by way of the handle holder 106. Specifically, the handle holder 106 may
be adapted to hold the handle 108 through the distal end 108b of the handle 108.
As used herein the term “proximal end 108a” refers to an end that is towards the
furnace 104. As used herein the term “distal end 108b” refers to an end that points
away from the furnace 104. In some aspects of the present disclosure, the handle
holder 106 and the handle 108 may be made up of material such as, but not
limited to glass, metal, and the like. Aspects of the present disclosure are intended
to include and/or otherwise cover any type of the material for the handle holder
106 and the handle 108, including known, related and later developed materials,
without deviating from the scope of the present disclosure.
[40] The furnace chamber 104 may have first end 104a and a second end 104b.
The furnace chamber 104 may have a first cylindrical portion 110a, a second
cylindrical portion 110b, a third cylindrical portion 110c, and a taper portion 112.
In some aspects of the present disclosure, the first cylindrical portion 110a and the
second cylindrical portion 110b may have a first diameter and a second diameter,
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respectively, such that the first diameter of the first cylindrical portion 110a is
smaller than the second diameter of the second cylindrical portion 110b.
[41] The first cylindrical portion 110a and the taper portion 112 may be
towards the first end 104a and the second 104b, respectively. In some aspects of
the present disclosure, the taper portion 112 may facilitate in properly directing
flow of gases towards a heated portion (i.e., a neck down region 102a of the
cylindrical glass preform 102) during the optical fiber draw process. The term
“neck down region” as used herein refers to a point of the cylindrical glass
preform 102 which is formed after melting the cylindrical glass preform 102 for
pulling the bare optical fiber 118 form that point. The furnace chamber 104 may
be a hollow chamber that may be adapted to accept the cylindrical glass preform
102. As illustrated, the cylindrical glass preform 102 may be inserted through the
first cylindrical portion 110a into the second cylindrical portion 110b of the
furnace chamber 104 from the first end 104a of the furnace chamber 104. The
furnace chamber 104 may have a top plate 114 that may be disposed along a
periphery of the first cylindrical portion 110a near the first end 104a of the furnace
chamber 104. Specifically, the top plate 114 may extend outwards from an outer
surface along the periphery of the first cylindrical portion 110a of the furnace
chamber 104. Similarly, the furnace chamber 104 may have a bottom plate 116
that may be disposed along a periphery of the taper portion 112 near an interface
of the taper portion 112 and the third cylindrical portion 110c of the furnace
chamber 104. Specifically, the bottom plate 116 may extend outwards from an
outer surface along the periphery of the taper portion 112 of the furnace chamber
104. In some aspects of the present disclosure, the top plate 114 and the bottom
plate 116 may be adapted to facilitate in control of a diameter of a bare optical
fiber 118 drawn from the cylindrical glass preform 102.
[42] The furnace chamber 104 may further have a plurality of seals 120 of
which a first seal 120a and a second seal 120b are shown. Specifically, the first
seal 120a and the second seal 120b may be disposed along an inner surface of the
first cylindrical portion 110a. The first seal 120a and the second seal 120b may be
adapted to seal the cylindrical glass preform 102 within the furnace chamber 104.
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As illustrated, the plurality of seals 120 may form a plurality of sealing chambers
122 of which first and second sealing chambers 122a and 122b are shown.
Specifically, the first seal 120a and the second seal 120b may form the first and
second sealing chambers 122a and 122b. Specifically, the first sealing chamber
122a may be defined between the first seal 120a and the second seal 120b.
Similarly, the second sealing chamber 122b may be defined between the second
seal 120b and an inner space of the furnace chamber 104. Although FIG. 1A
illustrates that the plurality of seals 120 includes two seals (i.e., the first and
second seals 120a and 120b) and the plurality of sealing chambers 122 includes
two sealing chambers (i.e., the first and second sealing chambers 122a and 122b),
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 plurality of seals 120
and the plurality of sealing chambers 122 may include more than two seals and
sealing members, respectively, without deviating from the scope of the present
disclosure. In such a scenario, each seal and each sealing member is adapted to
perform one or more operations in a manner similar to the operations of the first
and second seals 120a and 120b and the first and second sealing chambers 122a
and 122b, respectively, as described above. Specifically, while melting the
cylindrical glass preform 102 inside the furnace chamber 104, a positive pressure
may be maintained in the furnace chamber 104. The cylindrical glass preform 102
may be melted in presence of the first inert gas and the second inert gas. Further,
to maintain the positive pressure in the furnace chamber 104, a constant total
volume of the first inert gas and the second inert gas may be provided in the
furnace chamber 104. The constant total volume may be defined as a sum of
volume of the first inert gas and the second inert gas. In some aspects of the
present disclosure, the first inert gas may be defined by a fist atomic number and
the second inert gas may be defined by a second atomic number, wherein the
second atomic number is at least 5 times the first atomic number. In some aspect
of the present disclosure, the first atomic number of first inert gas is 2 and the
second atomic number of the second inert gas is 18. In one of the non-limiting
example of the present disclosure, the first inert gas may be Helium (He) and the
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second inert gas may be Argon (Ar). In some aspects of the present disclosure, the
constant total volume of the first inert gas and the second inert gas may be less
than 17 Standard litre per second per cubic metre. In some aspects of the present
disclosure, the constant total volume of the first inert gas and the second inert gas
may be in a range of 1.7 to 17 Standard litre per second per cubic metre. In some
aspects of the present disclosure, the constant total volume of the first inert gas
and the second inert gas may be 32 +/-17% Standard Litre Per Minute (slpm). The
total volume of the first and second inert gases may be maintained to the constant
value to control the bare fiber diameter (BFD) variation.
[43] The furnace chamber 104 may further have a plurality of inlet ports
124a-124n disposed along the periphery of the second cylindrical portion 110b
near an interface of the first and second cylindrical portions 110a and 110b.
Specifically, the plurality of inlet ports 124a-124n may be through holes that may
be adapted to allow inflow gases (e.g., the first and second inert gases) inside the
furnace chamber 104. In some aspects of the present disclosure, a diameter of
each inlet port of the plurality of inlet ports 124a-124n may be similar. In some
aspects of the present disclosure, a diameter associated with the plurality of inlet
ports 124a-124n may be different.
[44] In some aspects of the present disclosure, the first inert gas may be defined
by a first atomic number and the second inert gas may be defined by a second
atomic number such that the second atomic number may be at least 5 times the
first atomic number. In some aspects of the present disclosure, the first atomic
number may be 2 and the second atomic number may be 18. In a non-limiting
example of the present disclosure, the first and second inert gases may be Helium
(He) and Argon (Ar), respectively. Specifically, the first inert gas and the second
inert gas inside the furnace chamber 104 may facilitate to achieve a control in
variation of the BFD of the bare optical fiber 118 drawn from the cylindrical glass
preform 102 within a certain band. Generally, change in flows of gases alters a
bandwidth of the BFD variation. Thus, the first and second inert gases are passed
inside the furnace chamber 104 with a pressure that is slightly above atmospheric
pressure with a major purpose to prevent atmospheric air entry into the furnace
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chamber 104 to create inert atmosphere inside the furnace chamber 104 because
when the inert atmosphere is not present in the furnace chamber 104, a heating
element of the furnace chamber 104 that is made up of graphite (as discussed in
detail later) may start generating carbon dioxide and carbon monoxide. Generally,
nitrogen may also be injected as an inert gas inside the furnace chamber 104.
However, kinematic viscosity of nitrogen is less than that of He and Ar, thus a
tendency of forming turbulence inside the furnace chamber 104 is high while
using nitrogen as compared to Helium (He) and Argon (Ar), therefore Helium
(He) and Argon (Ar) may be used inside the furnace chamber 104.
[45] The first inert gas and the second inert gas may be provided inside the
furnace chamber 104 in a predefined ratio. The predefined ratio may be in a range
of 0.3 to 5. The predefined ratio is defined as a ratio of volume of the first inert
gas (e.g., He) to volume of second inert gas (e.g., Ar). Specifically, the predefined
ratio of the first and second inert gases may be maintained between that range of
0.3 to 5 to avoid (i) a short-term variation in BFD of the bare optical fiber 118, (ii)
a turbulent flow of the inert gases, and (iii) gases eddies formation near the
neckdown region 102a of the cylindrical glass preform 102. The term “short-term
variation” as used herein may be defined as a very rapid and random occurrence
of the BFD variation within small time scales. The short-term variation in the
BFD is caused by gas turbulence inside the furnace chamber 104. The short-term
variation in BFD may be avoided by maintaining the predefined ratio of volume
of the first inert gas and the second inert gas inside the furnace chamber 104
within the predefined ratio of 0.3 to 5. Specifically, when other inert gases and/or
incorrect amount of the first and second inert gases are injected inside the furnace
chamber 104, the gas flows near the neck down region becomes laminar to
turbulent because of diverging pathway near the neckdown region 102a of the
cylindrical glass preform 102. Thus, the predefined ratio of the first inert gas and
the second inert gas may be maintained between 0.3 to 5 to avoid both the
turbulent flow of the first inert gas and the second inert gas and formation of gases
eddies near the neckdown region 102a of the cylindrical glass preform 102.
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[46] Further, the predefined ratio of the first and second inert gases may be
maintained between 0.3 to 5 across a length of the cylindrical glass preform 102
irrespective of any irregularity in the cylindrical glass preform 102. In some
aspects of the present disclosure, the predefined ratio of volume of the first and
second inert gases may be greater than 1. Furthermore, as a quantity of the first
inert gas (e.g., Helium (He)) is higher than a quantity of the second inert gas (e.g.,
Argon (Ar)), therefore a total gas flow may have to be kept as minimum to
provide proper sealing (i.e., to avoid leakage of gases) as well as to reduce cost of
the first inert gas. To keep the total gas flow minimum, the furnace chamber 104
has the plurality of seals 120 (as discussed above) and the plurality of sealing
chambers 122 (as discussed above). In some aspects of the present disclosure, the
first sealing chamber 122a may be provided with an inert gas (e.g., Argon (Ar),
Helium (He)) to minimize the total gas flow which is sufficient to prevent entry of
the atmospheric air inside the furnace chamber 104. In some aspects of the present
disclosure, the first inert gas and the second inert gas may be injected inside the
furnace chamber 104 due to the fact that there is a large amount of graphite
member in the furnace chamber 104. In some aspects of the present disclosure, the
first inert gas (i.e., Helium (He)) injected into the furnace chamber 104 may have
a density of 0.17 Kilograms/Meter3 (Kg/m3) and the second inert gas (i.e., Argon
(Ar)) injected into the furnace chamber 104 may have a density of 1.7 Kg/m3 such
that the density of the second inert gas (i.e., Argon (Ar)) may be 10 times higher
than the density of the first inert gas (i.e., Helium (He)). In some aspects of the
present disclosure, the first inert gas (i.e., Helium (He)) injected into the furnace
chamber 104 may have a kinematic viscosity of 12.35 x 10-5 Nsm/kg and the
second inert gas (i.e., Argon (Ar)) may have a kinematic viscosity of 1.42 * 10-5
Nsm/kg.
[47] The furnace chamber 104 may be a susceptor that may be made up of a
conductive metal material. Specifically, the second cylindrical portion 110b and
the taper portion 112 of the furnace chamber 104 may be made up of the
conductive metal material and may be used to transfer heat to the cylindrical glass
preform 102. Preferably, the second cylindrical portion 110b and the taper portion
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112 of the furnace chamber 104 may be made up of graphite. Specifically, the
cylindrical glass preform 102 may be heated by virtue of radiation provided by the
heated graphite susceptor (i.e., the second cylindrical portion 110b and the taper
portion 112 of the furnace chamber 104). As illustrated, the apparatus 100 further
has an induction coil 126 that may be coiled around the second cylindrical portion
110b and the conical section 112. Specifically, the induction coil 126 may be
adapted to inductively heat the second cylindrical portion 110b and the taper
portion 112 of the furnace chamber 104 such that the heat is further transferred to
the cylindrical glass preform 102 held within the furnace chamber 104.
[48] The third cylindrical portion 110c may be an extension tube that may
extend from the taper portion 112. Specifically, the third cylindrical portion 110c
may have a third diameter that may be smaller than the first and second diameters
of the first and second cylindrical portions 110a and 110b, respectively.
[49] FIG. 1B illustrates a block diagram of a system 130. The system 130 may
have the apparatus 100 (as discussed in FIG. 1A), an annealing furnace 132, a
fiber cooling apparatus 134, a coating apparatus 136, an Ultraviolet (UC) curing
apparatus 138, a capstan 140, a dancer pulley 142, a take-up spool 144, a diameter
sensor 146, and a controller 148.
[50] In some aspects of the present disclosure, the annealing furnace 132 may
be adapted to receive the bare optical fiber 118 drawn from the cylindrical glass
preform 102. Further, the annealing furnace 132 may facilitate to slowly cool the
bare optical fiber 118 drawn from the cylindrical glass preform 102 in one or more
annealing stages. Specifically, the annealing furnace 132 may be adapted to lower
an attenuation of the bare optical fiber 118 by lowering an effective temperature
during the optical fiber draw process. In some aspects of the present disclosure,
the attenuation of the optical fiber 152 may be less than 0.324 Decibels (dB) at a
wavelength of 1310 nanometres (nm).
[51] Further, the fiber cooling apparatus 134 may be disposed adjacent to the
annealing furnace 132 such that the fiber cooling apparatus 134 receives the bare
optical fiber 118 that is annealed by the annealing furnace 132. The fiber cooling
apparatus 134 may be configured to cool down the bare optical fiber 118 after the
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annealing process while the bare optical fiber 118 is being drawn through contact
with one or more cooling fluid and/or air in the fiber cooling apparatus 134.
[52] The coating apparatus 136 may be disposed adjacent to the fiber cooling
apparatus 134. Specifically, the coating apparatus 136 may have one or more
coating sub-systems such that the bare optical fiber 118 drawn from the
cylindrical glass preform 102 passes through the one or more coating sub-systems
to coat the bare optical fiber 118 with one or more primary coating materials and
one or more secondary coating materials to generate a coated optical fiber 150.
The one or more primary coating materials and the one or more secondary coating
materials may protect a surface of very thin bare optical fiber (generally, with a
cross section diameter of 125 µm) to improve strength of the bare optical fiber
118, which is excellent in terms of heat resistance, cold resistance, and
demonstrates stable function over a wide temperature range. The one or more
secondary coating materials may be a coloured secondary coating material.
[53] The UV curing apparatus 138 may be disposed adjacent to the coating
apparatus 136 and adapted to cure the coated optical fiber 150 using UV radiation
to obtain an optical fiber 152 and further may colour code the coated optical fiber
150 to protect the optical fiber 152 against cracks and make the optical fiber 152
especially resistant to abrasion and scratches. In some aspects of the present
disclosure a diameter of the optical fiber 152 may be in a range of 150 µm to 250
µm.
[54] The capstan 140 may be disposed adjacent to the UV curing apparatus 138
and adapted to pull the bare optical fiber 118 from a bottom of the cylindrical
glass preform 102 in the furnace chamber 104. In some aspects of the present
disclosure, the capstan 140 may be a flexible belt partially wounded over a flat
pulley that moves and/or pulls a continuous optical fiber (i.e., the bare optical
fiber 118) all the way from the cylindrical glass preform 102. In some aspects of
the present disclosure, the capstan 140 can control a diameter of the optical fiber
by adjusting a capstan speed. Specifically, a draw capstan design has a direct
impact on the resulting fiber quality. Also, the capstan speed plays a significant
role in controlling the BFD variation (specifically a long-term BFD variation).
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The capstan speed may be varied in a very short range to achieve a lower BFD
variation. The BFD during the optical fiber draw process may vary in a different
manner in different time periods. Specifically, the BFD may vary as a long-term
variation. The term “long-term variation” as used herein may be defined as a slow
variation in the BFD that occurs at a periodic interval at longer time scales. The
long-term variation in the BFD may be caused by frequent and higher variation in
the feed speed. Thus, the long-term variation in the BFD may be avoided by
varying the feed speed by a small amount based on a measured diameter of the
bare optical fiber 118 and a change in the capstan speed. The feed speed may be
varied by 0.3 mmpm based on the measured diameter of the bare optical fiber 118
and a change in the capstan speed. Preferably, the feed speed may be varied in one
or more steps such that each step is less than 0.3 mmpm. Specifically, the feed
speed and the capstan speed may be related as mass and/or volume of the
cylindrical glass preform 102 being pulled by the capstan 140 in the form of the
bare optical fiber 118 is conserved by a feed rate of the cylindrical glass preform
102. Thus, the mass and/or volume of the cylindrical glass preform 102 being
pulled may be equal to the mass and/or volume of the cylindrical glass preform
102 being fed inside the furnace chamber 104. When the capstan speed is
increased and/or decreased to control the BFD variation, subsequently the feed
speed may be increased and/or decreased to provide enough of the cylindrical
glass preform 102 material inside the furnace chamber 104 to maintain a
predefined diameter of the bare optical fiber 118 in range during further optical
fiber draw process. Preferably the predefined diameter of the bare optical fiber
118 may be less than or equal to 125+0.1.
[55] The dancer pulley 142 may be disposed adjacent to the capstan 140. In
some aspects of the present disclosure, the dancer pulley 142 may be adapted to
produce a desired winding tension of the optical fibre 152 on the take-up spool
144. In some aspects of the present disclosure, the dancer pulley 142 may have
two pulleys (not shown), one behind the other on a common shaft (not shown).
The optical fiber 152 may be fed first to the rear pulley, then back up to the idler
pulley, back down to the front dancer pulley and up to the take-up spool 144.
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[56] The diameter sensor 146 may be configured to sense signals representing
an outer diameter of the bare optical fiber 118 drawn from the cylindrical glass
preform 102. In some aspects of the present disclosure, the diameter sensor 146
may be a single point sensor that can sense the diameter of the bare optical fiber
118 drawn from the cylindrical glass preform 102 when a centre of the bare
optical fiber 118 drawn from the cylindrical glass preform 102 is known. In some
aspects of the present disclosure, the controller 148 may communicate with
different sensor such as a sensor to measure the capstan speed (not shown), the
diameter sensor 146 of the bare optical fiber 118, and the feed speed. The
controller 148 may store a look-up table that includes multiple values of change in
the feed speed corresponding to different values of change in the capstan speed
(i.e., capstan slope value). The term “capstan slope value” as used herein refers to
a change in previous capstan speed and a new adjusted capstan speed. Preferably,
the capstan slope value may be equal to zero in ideal condition. In other words,
the diameter sensor 146 may be communicatively coupled with the controller 148
such that the controller 148 upon receiving the sensed signals from the diameter
sensor 146 may determine a numerical value of the diameter. Further, the
controller 148 may be communicatively coupled with the capstan 140 such that
the controller 148 controls the capstan speed based on the determined diameter of
the bare optical fiber 118.
[57] In some aspects of the present disclosure, the controller 148 may be, but
are not limited to, an application-specific integrated circuit (ASIC) processor, a
reduced instruction set computing (RISC) processor, a complex instruction set
computing (CISC) processor, a field-programmable gate array (FPGA), a
Programmable Logic Control unit (PLC), and the like. Aspects of the present
disclosure are intended to include or otherwise cover any type of the controller
148 including known, related art, and/or later developed technologies known to a
person of ordinary skill in the art, without deviating from the scope of the present
disclosure.
[58] In operation, the cylindrical glass preform 102 may be hung at the first end
104a of the furnace chamber 104 and inserted inside the furnace chamber 104 at a
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predefined feed speed. The term “feed speed” as used herein refers to a rate at
which the cylindrical glass preform 102 is fed downward into the furnace chamber
104. Specifically, the feed speed may be determined using the below equation:
???????? ?????????? = ?????????? ???????? ??????????*(?????????? ????????????????)2
(?????????????? ????????????????)2
[59] However, due to irregularities in a diameter of the cylindrical glass
preform 102 all along an axial length, the feed speed may be variable. In some
aspects of the present disclosure, the diameter of the cylindrical glass preform 102
may vary from ±12 millimetres (mm) or more. Therefore, to have a continous feed
for same capstan speed, the feed speed may be changed multiple times during the
optical fiber draw method and/or process based on a change in the capstan speed
and based on maximum possible fluctuation in the diameter of the cylindrical
glass preform 102.
[60] Moreover, most of the time, the feed speed of the cylindrical glass preform
102 inside the furnace chamber 104 is either much more than what is required and
much less than what is required which results in rapid change in the feed speed
that may alter a mean value of diameter (generally, 125 micrometres (µm)) and
may results in long-term variation in the mean diameter with time period greater
than 10 seconds or more (not limited to this time). Therefore, to avoid these rapid
changes in the feed speed, the feed speed may be varied by a small amount or
with small step values such that that the feed speed does not overshoot and/or
undershoot the required mass of the cylindrical glass preform 102 inside the
furnace chamber 104 and the mean diameter may be maintained as near to 125 µm
(preferably 125+0.1). Further, the BFD variation of the bare optical fiber 118 may
be less than 0.1 micrometers (µm) (i.e., less than +/-0.1 µm) from the mean
diameter of the bare optical fiber 118. In some aspects of the present disclosure,
the BFD of the bare optical fiber 118 may be greater than 125 µm or less than 125
µm (for example 80 µm, 100 µm, 110 µm). In some aspects of the present
disclosure, the mean diameter of the bare optical fiber 118 may be in a range of 80
to 125 µm. Specifically, the cylindrical glass preform 102 may be inserted inside
the furnace chamber 104 at a predefined feed speed. In some aspect of the present
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disclosure, the predefined feed speed may have a deviation of less than 0.3 mmpm
(Millimetre Per Minute) from the mean value of the predefined feed speed for
maintaining the mean diameter (i.e., 125 µm (preferably 125+0.1)) of the bare
optical fiber 118. In other words, the deviation from the mean value of the
predefined feed speed may be less than 0.3 mmpm for maintaining the mean
diameter of the bare optical fiber 118.
[61] Further, the cylindrical glass preform 102 may be melted by way of the
radiations provided by the induction coil 126 until glass from the cylindrical glass
preform 102 flows under a low pulling tension. The capstan 140 (i.e., a draw
capstan) pulls the bare optical fiber 118 from the bottom of the cylindrical glass
preform 102 in the furnace chamber 104, while the cylindrical glass preform 102
feed drive above the furnace chamber 104 maintains material flow equilibrium
through the furnace chamber 104. The bare optical fiber 118 is further cooled (by
way of the fiber cooling apparatus 134), coated in protective polymers (by way of
the coating apparatus 136), cured under ultraviolet lights (by way of the UV
curing apparatus 138), and wound onto the take-up spool 144.
[62] FIG. 2 illustrates the optical fiber drawing method 200 in presence of the
first inert gas and the second inert gas. The method 200 involves drawing the bare
optical fiber 118 from a cylindrical glass preform 102 in a furnace chamber 104.
The method has the following steps:
[63] At step 202, the cylindrical glass preform 102 may be inserted inside the
furnace chamber 104 of the apparatus 100.
[64] At step 204, the first inert gas and second inert gas (such as Helium (He)
and Argon (Ar)) may be injected inside the furnace chamber 104 of the apparatus
100.
[65] At step 206, the cylindrical glass preform 102 may be melted by way of
the radiations provided by the induction coil 126 of the apparatus 100 until glass
from the cylindrical glass preform 102 flows under a low pulling tension. The
cylindrical glass preform 102 may be melted in the presence of a first inert gas
and a second inert gas inside the furnace chamber 104 such that the first and
second inert gases are in a predefined ratio. The first inert gas is defined by a first
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atomic number (for example He), and the second inert gas is defined by a second
atomic number (for example Ar). The second atomic number is at least 5 times the
first atomic number, and the predefined ratio of the volume of the first inert gas
and the second inert gas is in a range of 0.3 to 5.
[66] At step 208, the bare optical fiber 118 may be drawn from the cylindrical
glass preform 102 by way of the capstan 140 (i.e., a draw capstan) that pulls the
bare optical fiber 118 from the bottom of the cylindrical glass preform 102 in the
furnace chamber 104.
[67] At step, 210, the bare optical fiber 118 may be cooled in a cooling
apparatus 134 to ensure that the Bare Fiber Diameter (BFD) variation of the bare
optical fiber 118 is less than 0.1 µm from a mean diameter of the bare optical fiber
118.
[68] At step 212, the bare optical fiber 118 may be coated with one or more
coating layers such as a primary coating layers and a secondary coating layers.
[69] At step 214, an optical fiber 152 may be manufactured using the above
method such that the ratio of inert gases used during the melting process and the
cooling process are effectively controlled to ensure that the bare optical fiber 118
has the desired diameter and minimal variation in the diameter. Specifically, the
bare optical fiber 118 has a BFD with a tolerance of 0.1 microns.
[70] FIG. 3A illustrates a graph 300 that represents the short-term variation and
the long-term variation of the BFD. The graph 300 is a Bare Fiber Diameter
(BFD) versus time graph such that an x-axis of the graph 300 represents values of
time (in seconds), and a y-axis of the graph 300 represents values the BFD.
Specifically, the graph 300 may represent the short-term variation and the
long-term variation of the BFD that is recorded for 11 minutes (i.e., 660 seconds).
The graph 300 has a curve 302 that represents a superimposition of the long-term
variations of the BFD about the mean diameter of the bare optical fiber 118 and
the short-term variations of the BFD about the mean diameter of the bare optical
fiber 118 based on real time data of the BFD of the bare optical fiber 118. The
graph 300 has a curve 302 that represents the superimposition of the long-term
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variations and the short-term variations of the BFD of the bare optical fiber 118
recorded for 11 minutes (i.e., 660 seconds).
[71] FIG. 3B illustrates a graph 304 that represents the long-term variation of
the BFD of the bare optical fiber 118. Specifically, the graph 304 may represent
the long-term variation (i.e., greater than 10 seconds) of the BFD of the bare
optical fiber 118 filtered out from the graph 300 of FIG. 3A. The graph 304 is a
BFD versus time graph such that an x-axis of the graph 304 represents values of
time (in seconds), and a y-axis of the graph 304 represents value of the BFD.
Specifically, the graph 304 may represent the long-term variation of the BFD that
is recorded for 11 minutes (i.e., 660 seconds). As illustrated, the graph 304 has a
curve 306 that represents the long-term variations of the BFD about the mean
diameter of the bare optical fiber 118 based on real time data of the BFD of the
bare optical fiber 118.
[72] FIG. 3C illustrates a graph 308 that represents the short-term variation of
the BFD of the bare optical fiber 118. Specifically, the graph 308 may represent
the short-term variation (i.e., less than 10 seconds) of the BFD of the bare optical
fiber 118 filtered out from the graph 300 of FIG. 3A. The graph 308 is a BFD
versus time graph such that an x-axis of the graph 308 represents values of time
(in seconds), and a y-axis of the graph 308 represents values the BFD.
Specifically, the graph 308 may represent the short-term variation of the BFD that
is recorded for 11 minutes (i.e., 660 seconds). As illustrated, the graph 308 has a
curve 310 that represents the short-term variations of the BFD about the mean
diameter of the bare optical fiber 118 based on real time data of the BFD of the
bare optical fiber 118.
[73] FIG. 4 illustrates a flowchart of a method 400 of drawing the bare optical
fiber 118 during the short-term variation of the BFD.
[74] At step 402, a cylindrical glass preform 102 may be melted inside the
furnace chamber 104 of the apparatus 100 in presence of the first inert gas (e.g.,
He) and the second inert gas (e.g., Ar). The first inert gas and the second inert gas
may be injected inside the furnace chamber 104 of the apparatus 100. Specifically,
the predefined ratio of the first inert gas and the second inert gas may be
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maintained between 0.3 to 5 to avoid the short-term variation in the BFD of the
bare optical fiber 118 and to avoid (i) the turbulent flow of the first inert gas and
the second inert gas and (ii) formation of gases eddies near the neckdown region
102a of the cylindrical glass preform 102. The cylindrical glass preform 102 may
be melted by way of the radiations provided by the induction coil 126 of the
apparatus 100 until glass from the cylindrical glass preform 102 flows under a low
pulling tension.
[75] At step 404, the bare optical fiber 118 may be drawn from the cylindrical
glass preform 102 by way of the capstan 140 (i.e., a draw capstan) that pulls the
bare optical fiber 118 from the bottom (i.e., neckdown region 102a) of the
cylindrical glass preform 102 in the furnace chamber 104.
[76] At step 406, the bare optical fiber 118 may be cooled in a fiber cooling
apparatus 134. Specifically, the Bare Fiber Diameter (BFD) variation of the bare
optical fiber 118 is less than 0.1 micrometers (µm) from a mean diameter of the
bare optical fiber 118. The mean diameter of the bare optical fiber 118 may be
maintained at a predefined diameter. In some aspects of the present disclosure the
predefined diameter may be less than or equal to 125 µm (preferably 125+0.1).
[77] FIG. 5 illustrates a flowchart of a method 500 of drawing the bare optical
fiber 118 during the long-term variation of the BFD.
[78] At step 502, the cylindrical glass preform 102 may be inserted inside the
furnace chamber 104 of the apparatus 100. Specifically, the cylindrical glass
preform 102 may be inserted inside the furnace chamber 104 at a predefined feed
speed. In some aspect of the present disclosure, the predefined feed speed may
have a deviation of is less than 0.3 mmpm (Millimetre Per Minute) from the mean
value of the predefined feed speed (generally between 1 mmpm to 5 mmpm) for
maintaining the mean diameter of the bare optical fiber 118 at a predefined
diameter.
[79] At step 504, the predefined feed speed may be adjusted based on a capstan
speed of the capstan 140 (i.e., a draw capstan) in one or more steps such that each
step is less than 0.3 mmpm.
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[80] At step 506, the cylindrical glass preform 102 may be melted in presence
of the first inert gas (e.g., Helium (He)) and the second inert gas (e.g., Argon (Ar))
inside the furnace chamber 104 of the apparatus 100. Specifically, the predefined
ratio of volume of the first inert gas and second inert gas may be maintained
between 0.3 to 5 to avoid the variation in the BFD of the bare optical fiber 118
and to avoid (i) the turbulent flow of the first inert gas and the second inert gas
and (ii) formation of gases eddies near the neckdown region 102a of the
cylindrical glass preform 102.
[81] At step 508, the bare optical fiber 118 may be drawn from the cylindrical
glass preform 102 by way of the capstan 140 (i.e., a draw capstan) that pulls the
bare optical fiber 118 from the bottom (i.e., neckdown region 102a) of the
cylindrical glass preform 102 in the furnace chamber 104. the cylindrical glass
preform 102 may be melted by way of the radiations provided by the induction
coil 126 of the apparatus 100 until glass from the cylindrical glass preform 102
flows under a low pulling tension.
[82] At step 510, the the bare optical fiber 118 may be cooled in a fiber cooling
apparatus 134. Specifically, the Bare Fiber Diameter (BFD) variation of the bare
optical fiber 118 is less than 0.1 micrometers (µm) from a mean diameter of the
bare optical fiber 118. The mean diameter of the bare optical fiber 118 may be
maintained at the predefined diameter. In some aspects of the present disclosure
the predefined diameter may be less than or equal to 125 µm (preferably 125+0.1).
[83] FIG. 6 illustrates another flowchart of a method 600 of drawing the bare
optical fiber 118 during the short-term and the long-term diameter variation of the
BFD.
[84] At step 602, the cylindrical glass preform 102 may be inserted inside the
furnace chamber 104 of the apparatus 100. Specifically, the cylindrical glass
preform 102 may be inserted inside the furnace chamber 104 at a predefined feed
speed. In some aspects of the present disclosure, the predefined feed speed may
have a deviation of less than 0.3 mmpm (Millimetre Per Minute) from the mean
value of the predefined feed speed for maintaining the mean diameter of the bare
optical fiber 118.
23/30
[85] At step 604, the cylindrical glass preform 102 may be melted by way of
the radiations provided by the induction coil 126 of the apparatus 100 until glass
from the cylindrical glass preform 102 flows under a low pulling tension. The
cylindrical glass preform 102 may be melted in presence of the first inert gas
(such as He) and the second inert gas (such as Ar) inside the furnace chamber 104
of the apparatus 100 to draw the bare optical fiber 118. Specifically, the
predefined ratio of volume of the first inert gas and second inert gas may be
maintained between 0.3 to 5 to control the short-term variation in the BFD and to
avoid (i) the turbulent flow of the first inert gas and the second inert gas and (ii)
formation of gases eddies near the neckdown region 102a of the cylindrical glass
preform 102.
[86] At step 606, the bare optical fiber 118 may be cooled in a fiber cooling
apparatus 134. Specifically, the Bare Fiber Diameter (BFD) variation of the bare
optical fiber 118 is less than 0.1 micrometers (µm) from the mean diameter of the
bare optical fiber 118. The mean diameter of the bare optical fiber 118 may be
maintained at the predefined diameter. In some aspects of the present disclosure
the predefined diameter may be less than or equal to 125 µm (preferably 125+0.1).
[87] At step 608, the diameter of the bare optical fiber 118 (i.e., the BFD) and
the capstan speed of the capstan 140 may be measured by way of the controller
148.
[88] At step 610, the capstan speed may be adjusted based on the measured
diameter of the bare optical fiber 118 (i.e., the BFD) by way of the controller 148.
[89] At step 612, the predefined feed speed may be adjusted by way of the
controller 148 to a small amount based on the adjusted capstan speed.
Specifically, the predefined feed speed may be adjusted based on the adjusted
capstan speed in one or more steps such that such that each step is less than 0.3
mmpm to control the long-term BFD variation of the bare optical fiber 118.
[90] FIG. 7 illustrates a gas flow diagram 700 for injecting the first inert gas
and the second inert gas inside the furnace chamber 104. As illustrated, the first
and second inert gases (such as Helium (He) and Argon (Ar)) may be injected
inside the furnace chamber 104 by way of first and second gas injection apparatus
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702 and 704, respectively. The first gas injection apparatus 702 may have a first
regulator 706, a first solenoid valve 708, and a first mass flow controller 710.
Similarly, the second gas injection apparatus 702 may have a second regulator
712, a second solenoid valve 714, a gas manifold 716, and a second mass flow
controller 718. In an aspect of the present disclosure the first inert gas and the
second inert gas are injected inside the furnace chamber 104 via the inlet ports
124a-124n of the furnace chamber 104 as shown in Fig. 1A.
[91] Thus, the apparatus 100, the system 130, and the method 200, 400, 500,
600 of the present disclosure facilitate in reducing the short-term and long-term
BFD variation of the bare optical fiber 118. Further, the apparatus 100, the system
130, and the method 200, 400, 500, 600 of the present disclosure may facilitate in
minimizing a fiber rejection due to the variations in the BFD.
[92] Specifically, upon maintaining both the predefined ratio of volume of the
first inert gas and the second inert gas in a range of 0.3 to 5, and the effective
management and control of predefined speed, the variations in the BFD may be
controlled within + 0.1 µm band which minimizes the fiber rejection due to the
variations in the BFD. Further, the BFD variation of the bare optical fiber 118
with tighter tolerance i.e., + 0.1 µm band is essentially required for
connectorization. Further, upon effectively controlling the above discussed
parameters such as the inert gases ratio and predefined feed speed may control
sudden spikes in BFD during fiber draw process. Furthermore, the BFD variation
of the bare optical fiber 118 with tighter tolerance i.e., + 0.1 µm band is required
to control small angle scattering (SAS) at a core-cladding interface of the bare
optical fiber 118, which occurs due to continuous axial variation in cladding
diameter of the bare optical fiber 118.
[93] While various aspects of the present disclosure have been illustrated and
described, it will be clear that the present disclosure is not limited to these aspects
only. Numerous modifications, changes, variations, substitutions, and equivalents
will be apparent to those skilled in the art, without departing from the spirit and
scope of the present disclosure, as described in the claims. Further, unless stated
otherwise, terms such as “first” and “second” are used to arbitrarily distinguish
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between the elements such terms describe. Thus, these terms are not necessarily
intended to indicate temporal or other prioritization of such elements.
[94]
, Claims:I/We claim:
1. A method (200, 400, 500, 600) for drawing a bare optical fiber (118) from
a cylindrical glass preform (102) in a furnace chamber (104), the method (200,
400, 500, 600) comprising:
melting the cylindrical glass preform (102) in presence of a first inert gas
and a second inert gas inside the furnace chamber (104) to draw the bare optical
fiber (118) such that the first inert gas and the second inert gas are in a predefined
ratio, wherein the first inert gas is defined by a first atomic number and the second
inert gas is defined by a second atomic number, wherein the second atomic
number is at least 5 times the first atomic number, wherein the predefined ratio of
volume of the first inert gas and the second inert gas is in a range of 0.3 to 5; and
cooling the bare optical fiber (118), wherein a short-term Bare Fiber
Diameter (BFD) variation of the bare optical fiber (118) is less than 0.1
micrometers (µm) from a mean diameter of the bare optical fiber (118).
2. The method (200, 400, 500, 600) of claim 1 further comprising inserting
the cylindrical glass preform (102) in the furnace chamber (104) at a predefined
feed speed, wherein a deviation from a mean value of the predefined feed speed is
less than 0.3 Millimetre Per Minute (mmpm) for maintaining the mean diameter
of the bare optical fiber (118) at a predefined diameter, whereby controlling a
long-term diameter variation of the bare optical fiber (118).
3. The method (200, 400, 500, 600) of claim 1 further comprising:
measuring the BFD of the bare optical fiber (118) and a capstan speed of a
capstan (140) that pulls the bare optical fiber (118) from the cylindrical glass
preform (102); and
adjusting the capstan speed based on the measured BFD.
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4. The method (200, 400, 500, 600) of claim 2 further comprising adjusting
the predefined feed speed based on a capstan speed in one or more steps such that
each step is less than 0.3 mmpm.
5. A method (200, 400, 500, 600) for drawing a bare optical fiber (118) from
a cylindrical glass preform (102) in a furnace chamber (104), the method (200,
400, 500, 600) comprising:
inserting the cylindrical glass preform (102) in the furnace chamber (104)
at a predefined feed speed;
adjusting the predefined feed speed based on a capstan speed in one or
more steps such that each step is less than 0.3 mmpm;
melting the cylindrical glass preform (102) in presence of a first inert gas
and a second inert gas inside the furnace chamber (104) to draw the bare optical
fiber (118); and
cooling the bare optical fiber (118), wherein a mean diameter of the bare
optical fiber (118) is maintained at a predefined diameter.
6. The method (200, 400, 500, 600) of claim 5, wherein the first inert gas and
the second inert gas are in a predefined ratio, wherein the predefined ratio of
volume of the first inert gas and the second inert gas is in a range of 0.3 to 5,
wherein a Bare Fiber Diameter (BFD) variation of the bare optical fiber (118) is
less than 0.1 micrometers (µm) from a mean diameter of the bare optical fiber
(118).
7. The method (200, 400, 500, 600) of claim 5 further comprising:
measuring the BFD of the bare optical fiber (118) and the capstan speed of
a capstan (140) that pulls the bare optical fiber (118) from the cylindrical glass
preform (102); and
adjusting the capstan speed based on the measured BFD.
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8. The method (200, 400, 500, 600) of claim 5, wherein a deviation from a
mean value of the predefined feed speed is less than 0.3 Millimetre Per Minute
(mmpm).
9. An optical fiber (152) is manufactured using the method (200, 400, 500,
600) of any of the above claims such that the bare optical fiber (118) has a BFD of
the predefined diameter with a tolerance of 0.1 microns.
10. The method (200, 400, 500, 600) of any of the above claims, wherein a
constant total volume of the first inert gas and the second inert gas is maintained
in the furnace chamber (104), wherein the constant total volume of the first and
second inert gases is less than 17 Standard litre per second per cubic metre,
wherein the constant total volume is sum of volume of the first inert gas and the
second inert gas.
11. The method (200, 400, 500, 600) of any of the above claims, wherein the
first atomic number is 2 and the second atomic number is 18.
12. The method (200, 400, 500, 600) of any of the above claims, wherein an
attenuation of the optical fiber (152) is less than 0.324 Decibels (dB) at a
wavelength of 1310 nanometres (nm).