Description:TECHNICAL FIELD
[1] The present disclosure relates to the field of optical fibers and, in
particular, relates to an apparatus to manufacture an optical fiber and a glass
preform and a method thereof.
BACKGROUND
[2] Optical fibers are widely used in optical cables. Optical fibers are usually
drawn from a glass preform, which is a cylindrical body made up of glass.
Conventional glass preform manufacturing techniques have low deposition
efficiency, which leads to loss in capturing of silica soot particles. Furthermore,
manufacturing time is on the higher side (for example more than 15 hours).
[3] While there are number of ways to manufacture glass preform. For
example, the reference US5169421A discloses manufacturing of a silica glass
optical preform using an extrusion apparatus. The extrusion apparatus has a
ring-shaped die that is expanded and contracted by means of hydraulic pressure
for varying the outlet diameter and subsequently varying the diameter of the silica
glass optical preform. The reference JPH0680436A discloses manufacturing of a
porous optical fiber preform by an extrusion apparatus. The extrusion apparatus
uses a plastic material for the formation of a cladding layer on the outer portion of
the glass core. The reference US5314520A discloses a method for manufacturing
optical fiber preform that requires a porous preform to produce an optical fiber
exerting high mechanical strength, can be efficiently manufactured without
generating bubbles.
[4] Furthermore, conventional techniques/apparatus/methods of
manufacturing optical fiber and glass preform are very costly and cannot exhibit
any kind of dimensional variation for the optical fiber and glass preform being
manufactured. This increases the cost of production of optical fiber. Along-with
this, maintenance cost associated with the conventional apparatus is high.
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[5] In light of the above stated discussion, there is a need for an efficient and
effective apparatus and method to manufacture optical fibers and glass preforms
that overcomes the above stated disadvantages.
SUMMARY
[6] In an aspect of the present disclosure an extrusion apparatus to
manufacture a soot preform is disclosed. The extrusion apparatus has a feed
hopper adapted to hold and feed silica slurry. The extrusion apparatus further has
a barrel that is disposed beneath the feed hopper and adapted to receive the silica
slurry such that the silica slurry is pushed within the barrel. The extrusion
apparatus further has an iris frame such that the iris frame is provided with a
plurality of vanes. Each vane of the plurality of vanes is adapted to move in a
radial direction of the iris frame to create a central orifice. The central orifice is
adapted to exhibit, upon movement of each vane of the plurality of vanes, a
variable diameter such that variation in the diameter of the central orifice controls
a diameter of the soot preform. The extrusion apparatus further has a drying
furnace that is disposed beneath the iris frame and adapted to eliminate moisture
(i.e., physisorbed moisture) present in the soot preform to produce a dried soot
preform. The extrusion apparatus further has a debinding furnace that is coupled
to the drying furnace and adapted to eliminate one or more stabilized binders from
the dried soot preform to produce a green body. The debinding furnace is also
adapted to eliminate majority of chemisorbed moisture from the soot preform. The
dried soot preform, or the green body is sintered to obtain a glass preform such
that the optical fiber is drawn from the glass preform.
[7] In another aspect of the present disclosure a method to manufacture an
optical fiber is disclosed. The optical fiber may be manufactured by an extrusion
apparatus. The method has a step of forming a soot preform by using the extrusion
apparatus. The method further has a step of preparing silica slurry by mixing one
or more solvents, one or more binders, one or more additives, and silica particles.
The method further has a step of pushing, by way of one or more screws disposed
within a barrel, the silica slurry from an inlet end to an outlet end of the barrel.
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The method further has a step of extruding, by way of a die header such that the
silica slurry is cladded on a core rod to form the soot preform. The die header has
an iris frame to vary a diameter of the soot preform. The method further has a step
of drying, by way of a drying furnace, the soot preform for eliminating
physisorbed moisture present in the soot preform to produce a dried soot preform.
The method further has a step of debinding, by way of a debinding furnace, the
dried soot preform for eliminating the one or more stabilized binders along with
one or more additives from the soot preform such that upon debinding, a green
body is produced. The method further has a step of sintering, by way of a sinter
furnace, the dried soot preform or the green body to obtain a glass preform. The
method further has a step of drawing, by way of a draw furnace, the glass preform
to manufacture the optical fiber.
BRIEF DESCRIPTION OF DRAWINGS
[8] Having thus described the disclosure in general terms, reference will now
be made to the accompanying figures, wherein:
[9] FIG. 1A illustrates an extrusion apparatus for manufacturing a soot
preform.
[10] FIG. 1B illustrates an optical fiber manufacturing apparatus.
[11] FIG. 1C illustrates a representation of manufacturing of a plurality of soot
preforms in a continuous process.
[12] FIG. 2A illustrates a side view of another extrusion apparatus for
manufacturing a soot preform.
[13] FIG. 2B illustrates a front view of the extrusion apparatus of FIG. 2A for
manufacturing the soot preform.
[14] FIG. 3 illustrates an iris frame of the extrusion apparatus of FIG. 1A and
FIG. 2.
[15] FIG. 4 illustrates working of the iris frame of FIG. 3.
[16] FIG. 5 illustrates a flow-chart of a method for manufacturing an optical
fiber.
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[17] FIG. 6 illustrates a flow-chart of a method for manufacturing a multilayer
preform.
[18] FIG. 7 illustrates a flow-chart of a method for manufacturing a hollow
cylinder preform.
[19] FIG. 8 illustrates a flow-chart of a method for manufacturing a multicore
rod preform.
[20] FIG. 9 illustrates a flow-chart of a method for manufacturing a hollow clad
tube.
[21] 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.
DEFINITIONS
[22] 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
one or more glass cores and a glass cladding. The light moving through the one or
more glass cores of the optical fiber relies upon the principle of total internal
reflection, where the one or more glass core has a higher refractive index than the
refractive index of the cladding of the optical fiber.
[23] The term “core” of an optical fiber as used herein is referred to as the one
or more cylindrical structure present in the center or in a predefined lattice of the
optical fiber, that is configured to guide the light rays inside the optical fiber.
[24] 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.
[25] The term “glass preform” as used herein refers to a solid cylindrical body
made up 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.
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[26] The term “draw furnace” as used herein is referred to as a
high-temperature chamber used for melting the glass preform and drawing the
optical fiber. To start the drawing, the glass preform is lowered into the furnace
chamber. Generally, the drawing region is heated to about 1,900° C, where the
glass softens and elongates with a teardrop-shaped drip pulling the optical fiber
downward.
[27] The term “conical portion” as used herein referred to as a bottom point of
the glass preform which is melted for pulling the bare optical fiber form that
point.
[28] The term “sintering furnace” as used herein referred to as a chamber used
to convert a green body extruded from an extrusion apparatus to a glass preform.
The temperature of the sintering furnace is maintained at 1200-1600 degree
Celsius. The density of the green body lies in a range of 0.4 gram per
cubic-centimeter (g/cc) to 0.9 g/cc and the density of the glass preform lies in a
range of 2.19 g/cc to 2.20 g/cc.
[29] The term “double extrusion” as used herein refers to a process that
requires difference in radial compositions (inner and outer radial compositions)
throughout a preform or a rod. To facilitate double extrusion, an inner region with
an inner radial composition is firstly extruded and then dried to form the preform
or the rod. The preform or the rod is then used as bait for further extrusion of
layers over it.
[30] The term “discharge pressure” as used herein refers to amount of pressure
that is exerted by each screw of the one or more screws to push the silica slurry
towards the outlet end of the barrel.
[31] The term “channel” as used herein refers to perpendicular distance
between two adjacent threads of each screw of the one or more screws.
[32] The term “continuous process” as used herein may refer to non-stop
production of a plurality of soot preforms.
[33] The term “multiple layers” as used herein refers to one or more layers that
are extruded on the core rod.
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DETAILED DESCRIPTION
[34] 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.
[35] Moreover, although the following description contains many specifics for
the purposes of illustration, anyone skilled in the art will appreciate that many
variations and/or alterations to said details are within the scope of the present
technology. Similarly, although many of the features of the present technology are
described in terms of each other, or in conjunction with each other, one skilled in
the art will appreciate that many of these features can be provided independently
of other features. Accordingly, this description of the present technology is set
forth without any loss of generality to, and without imposing limitations upon, the
present technology.
[36] FIG. 1A illustrates an extrusion apparatus 100 for manufacturing a soot
preform 130. Specifically, the extrusion apparatus 100 may be a horizontal
extrusion apparatus 100. The horizontal extrusion apparatus 100 may manufacture
the soot preform 130, from which a glass preform 138 (as shown later in FIG. 1B)
is obtained to manufacture an optical fiber 142 (as shown later in FIG. 1B).
Specifically, the horizontal extrusion apparatus 100 may be adapted to
manufacture the soot preform 130 by an extrusion process. In some aspects of the
present disclosure, the extrusion process may be one of, direct extrusion and
indirect extrusion. The soot preform 130 may be manufactured from a silica slurry
102. The silica slurry 102 may be prepared from silica particles. The silica
particles may be known as silicon dioxide (SiO2) particles. The silica particles
may be mixed with one or more solvents and one or more binders in a container
(not shown). The silica particles may be mixed with the one or more solvents, one
or more binders, and one or more additives to prepare the silica slurry 102. The
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one or more additives may be stabilizers, dispersant, and/or polymerizing
initiators.
[37] The horizontal extrusion apparatus 100 may have a feed-hopper 104, a
barrel 106, one or more screws 108 (i.e., 108a and 108b), a plurality of heaters
110 of which first through nth heaters (here n is an integer) 110a-110n are shown,
a core rod holder 112, a die header 114, an iris frame 116, a drying furnace 118, a
gas tank 120, and a debinding furnace 122. The barrel 106 of the horizontal
extrusion apparatus 100 may be arranged along a X-X direction (i.e., a horizontal
direction) of a direction index as shown in FIG. 1A.
[38] The feed-hopper 104 may be adapted to hold the silica slurry 102. The
feed-hopper 104 may be further adapted to feed the silica slurry 102 to the barrel
106. Specifically, the silica slurry 102 may be fed into the barrel 106 under the
action of gravity. In other words, the silica slurry 102 may fall from the
feed-hopper 104 under the effect of gravity. In some aspects of the present
disclosure, the feed-hopper 104 may have a conical shape.
[39] The barrel 106 may have an inlet end 106a and an outlet end 106b. The
barrel 106 may be disposed beneath the feed-hopper 104. Specifically, the inlet
end 106a may be disposed beneath the feed-hopper 104 such that the barrel 106
receives the silica slurry from the feed-hopper 104.
[40] The one or more screws 108a and 108b may be disposed within the barrel
106. Aspects of the present disclosure are intended to include and/or otherwise
cover any number of screws without deviating from the scope of the present
disclosure. The one or more screws 108a and 108b may be adapted to rotate
within the barrel 106. Specifically, the one or more screws 108a and 108b may be
adapted to rotate within the barrel 106 by way of a motor 109. The one or more
screws 108a and 108b, upon rotation, may be further adapted to properly mix the
one or more solvents and the one or more binders in the silica slurry 102.
Furthermore, the one or more screws 108a and 108b, upon rotation may be
adapted to provide thrust to the silica slurry 102 that may push the silica slurry
102 towards the die header 114. Specifically, the one or more screws 108a and
108b, upon rotation, may push the silica slurry 102 towards the outlet end 106b
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such that the silica slurry 102 ejects out from the barrel 106. Furthermore, the one
or more screws 108a and 108b may force the silica slurry 102 to shear against
walls of the barrel 106 thereby developing heat due to viscous dissipation.
[41] In some aspects of the present disclosure, each screw of the one or more
screws 108a and 108b may be a helical screw. The one or more screws 108a and
108b may be moved in one of, a clockwise direction and a counter-clockwise
direction. In some exemplary aspects of the present disclosure, each screw of the
one or more screws 108a and 108b may rotate in the clockwise direction and
according to right-hand cork screw rule, the one or more screws 108a and 108b
may push the silica slurry 102 towards the outlet end 106b of the barrel 106.
[42] In some exemplary aspects of the present disclosure, the one or more
screws may be a pair of screws i.e., 108a and 108b. The pair of screws 108 and
108b may facilitate proper mixing of the silica slurry 102 and may leave lesser
number of dead spaces present in the silica slurry 102.
[43] In some aspects of the present disclosure, expression for discharge
pressure associated to each screw of the one or more screws may be
?? = p ?? ??3 ?? (?????? T)2
(12??µ)
or
?? = 0.02163 ?? ??3??
(??µ)
where: -
P is pressure flow
D is diameter of each screw of the one or more screws 108a and 108b;
H is depth of a channel of each screw of the one or more screws 108a and 108b;
p is discharging pressure;
L is length of metering section of each screw of the one or more screws 108a and
108b;
µ is coefficient of viscosity; and
T is angle of helix of each screw of the one or more screws 108a and 108b.
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[44] The first through nth heaters 110a-110n may be disposed at a periphery of
the barrel 106. Aspects of the present disclosure are intended to include and/or
otherwise cover any number of heaters without deviating from the scope of the
present disclosure. The first through nth heaters 110a-110n may be adapted to
provide heat to the silica slurry 102 that may be present in the barrel 106. The first
through nth heaters 110a-110n may initiate polymerization of the silica slurry 102
that facilitates the one or more binders to provide ample flexibility to soot
structure of the silica slurry 102. The polymerization of the silica slurry 102 may
provide ample flexibility and prevent packing of the soot structure. Furthermore,
the first through nth heaters 110a-110n may prevent too much packing of the soot
structure, which may allow a gas, if any, to vent out from the soot structure and
thereby eliminating cracks in the soot preform 130 (i.e., a clad soot). The first
through nth heaters 110a-110n may provide a temperature that may lie in a range
between 700 to 800 degrees Celsius to facilitate efficient polymerization of the
silica slurry 102.
[45] The die header 114 may be coupled to the barrel 106. The die header 114
may have a core rod holder 114a. The core rod 128 may be inserted into the die
header 114 from the top of the die header 114. The core rod 128 may be held in
the core rod holder 114a. The die header 114 may be adapted to push the core rod
128. The core rod 128 may be placed at a center of the die header 114. The core
rod 128 may form back-bone/supporting structure of the soot preform 130. The
core rod holder 112 may be adapted to feed the core rod 128 in the die header 114.
The core rod holder 112 may further be adapted to move the core rod 128 towards
the iris frame 116. The die header 114 may further be adapted to receive the silica
slurry 102 from the outlet end 106b of the barrel 106. Specifically, the silica slurry
102 may be cladded on an outer surface of the core rod 128 to form the soot
preform 130. The die header 114 may be designed such that the die header 114
co-extrudes the core rod 128. The speed of feeding the core rod 128 may
synchronize with the speed of extrusion of the clad soot. The synchronization in
the speed of feeding the core rod 128 and the speed of extrusion of the clad soot
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eliminates stresses in the optical fiber 142 and may ensure proper cladding of the
clad soot materials over the core rod 128.
[46] The iris frame 116 may be disposed underneath the die header 114. The
iris frame 116 may be adapted to form a conical portion 134 at an end of the soot
preform 130. Specifically, the iris frame 116 may be adapted to form the conical
portion 134 having a desired length and a slope at the end of the soot preform 130.
For example, the iris frame 116 may be adapted to form the conical portion 134 at
the bottom end of the soot preform 130.
[47] The drying furnace 118 may be disposed beneath the iris frame 116. The
drying furnace 118 may have a first inlet 118a and a first outlet 118b. The drying
furnace 118 may be adapted to eliminate moisture that is present in the soot
preform 130 to produce a dried soot preform 132.
[48] The gas tank 120 may have a second inlet 120a, a second outlet 120b, and
a vent 120c. The drying furnace 118 may be coupled to the gas tank 120.
Specifically, the first inlet 118a of the drying furnace 118 may be coupled to the
second outlet 120b of the gas tank 120. The second inlet 120a may be adapted to
allow air to enter into the gas tank 120. In some examples, the second inlet 120a
may be adapted to allow the air having temperature of about 25o Celsius. The gas
tank 120 may be adapted to mix the air with a gas to produce a hot gas. The
second outlet 120b may be adapted to exit the hot gas. In some examples, the hot
gas may have a temperature of about 60 o Celsius. The first inlet 118a may
therefore, facilitate the hot gas to enter to the drying furnace 118. The hot gas may
come in contact with the soot preform 130 such that the heat provided by the hot
gas eliminates the moisture from the soot preform 130 in the drying furnace
118.The debinding furnace 122 may be coupled to the drying furnace 118. The
debinding furnace 122 may have a third inlet 122a and a third outlet 122b. The
third outlet 122b may be coupled to the vent 120c. The third inlet 122a may be
adapted to allow air to enter into the debinding furnace 122. The gas tank 120 may
have a fourth outlet 122c. The fourth outlet 122c may be coupled to the vent 120c
to purge out debinded gases. The debinding furnace 122 may be adapted to
eliminate the one or more stabilized binders from the dried soot preform 132. The
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debinding furnace 122 may further be adapted to eliminate majority of
chemisorbed OH molecules (i.e., chemisorbed moisture) from the dried soot
preform 132. Specifically, the soot preform 130 or the dried soot preform 132 may
be treated for about 1 to 3 hours in the debinding furnace 122 at a temperature
range of about 800o Celsius to 1200o Celsius. The third outlet 122b may be
adapted to exit the debinded gases from the debinding furnace 122. The
de-binding furnace 122 may be, upon removal of the one or more binders, adapted
to produce a green body 136. In some aspects of the present disclosure, the soot
preform 130 may be manufactured in semi-continuous batch process (hereinafter
referred to as “batch process”). The batch process may require manufacturing of
the soot preform 130 such that the soot preform 130 may be removed from the
horizontal extrusion apparatus 100. The soot preform 130 may then undergo
drying by way of the drying furnace 118 and debinding by way of the debinding
furnace 122 in order to manufacture the glass preform 138 and then optical fiber
142.
[49] FIG. 1B illustrates an optical fiber manufacturing apparatus 101. The
optical fiber manufacturing apparatus 101 may have a sinter furnace 124, a draw
furnace 126, and a cooling tube 140. The optical fiber manufacturing apparatus
101 may be adapted to manufacture the optical fiber 142. Specifically, the dried
soot preform 132 or the green body 136 may be transferred to the sinter furnace
124 for manufacturing the optical fiber 142.
[50] The dried soot preform or the green body 136 may be transferred to the
sinter furnace 124. The sinter furnace 124 may be adapted to sinter the dried soot
preform or the green body 136 to obtain the glass preform 138. Specifically, while
sintering, the sinter furnace 124 may be adapted to close pores in the soot preform
130.
[51] The glass preform 138 may be transferred to the draw furnace 126. The
draw furnace 126 may be adapted to draw the optical fiber 142. Specifically, to
draw the optical fiber 142 from the glass preform 138, the conical portion 134 of
the glass preform 138 may be softened in presence of one or more gases.
Furthermore, the conical portion 134 of the glass preform 138 may be melted at
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high temperature (generally between 1800 oC to 2200 oC) to draw the optical fiber
142.
[52] In some aspects of the present disclosure, the glass preform 138 may be
doped with one or more suitable dopants to manufacture the optical fiber 142.
Specifically, a bare optical fiber may be drawn out from the glass preform 138 in
the draw furnace 126. The bare optical fiber may be defined as a type of optical
fiber without coating. The bare optical fiber may be gradually cooled in one or
more stages in an annealing furnace (not shown). The annealing furnace may be
adapted to cool the bare optical fiber (for example the temperature of the bare
optical fiber may be lowered down to 450oC). The bare optical fiber may further
be cooled in a cooling tube 140 that may be positioned below the annealing
furnace. The cooling tube 140 may use one or more cooling gases to cool down
the bare optical fiber. The one or more cooling gases may be adapted to bring the
temperature of the bare optical fiber to 50oC.
[53] The cooling tube 140 may be coupled to the draw furnace 126.
Specifically, the cooling tube 140 may be disposed below the draw furnace 126.
The cooling tube 140 may be adapted to cool the optical fiber 142, while the
optical fiber 142 is drawn from the draw furnace 126. Specifically, one or more
coolants may flow through the cooling tube 140 such that the one or more
coolants cools the optical fiber 142.
[54] FIG. 1C illustrates a representation 103 of manufacturing of a plurality of
soot preforms 130a-130n in a continuous process. Specifically, the plurality of
soot preforms 130a-130n may be manufactured in the continuous process, by way
of the horizontal extrusion apparatus 100. In some aspects of the present
disclosure, the plurality of soot preforms 130a-130n may be manufactured in the
continuous process by the one of, the horizontal extrusion apparatus 100 and the
vertical extrusion apparatus 200. In the continuous process, while manufacturing
of a first soot preform 130a of the plurality of soot preforms 130a-130n, the iris
frame 116 may close. The iris frame 116, upon manufacturing of a second soot
preform 130b of the plurality of soot preforms 130a-130n, may gradually open.
The plurality of soot preforms 130a-130n may be removed from the horizontal
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extrusion apparatus 100. The plurality of soot preforms 130-130n, upon removal
from the horizontal extrusion apparatus 100, may undergo drying by way of the
drying furnace 118. The plurality of soot preforms 130a-130n, upon drying, may
undergo debinding by way of the debinding furnace 122 in order to manufacture
the green body 136. For example, during manufacturing of the first soot preform
130a of the plurality of soot preforms 130a-130n, the iris frame 116 may form the
conical portion 134 at a left end of the first soot preform 130a. To form the
conical portion 134 at the left end of the first soot preform 130a, the iris frame 116
may gradually open. Further, the iris frame 116 may be adapted to form the
conical portion 134 at a right end of the first soot preform 130a. To form the
conical portion 134 at the right end of the first soot preform 130a, the iris frame
116 may gradually close. Furthermore, the iris frame 116 may be adapted to form
the conical portion 134 at a left end of the second soot preform 130b of the
plurality of soot preforms 130a-130n. To form the conical portion 134 at the left
end of the second soot preform 130b, the iris frame 116 may gradually open. In
this way, the iris frame 116 may gradually close and open in order to form the
conical portion 134 at a left and a right end of each soot preform of the plurality
of soot preforms 130a-130n.
[55] FIG. 2A illustrates a side view (X-Y plane) of another extrusion apparatus
200 for manufacturing the soot preform 130. Specifically, the extrusion apparatus
200 may be a vertical extrusion apparatus 200. The vertical extrusion apparatus
200 may manufacture the soot preform 130, from which the glass preform 138 is
obtained to manufacture the optical fiber 142. In some aspects of the present
disclosure, the extrusion process may be one of, direct extrusion and indirect
extrusion. The soot preform 130 may be manufactured from a silica slurry 102.
The silica slurry 102 may be prepared from silica particles. The silica particles
may be known as silicon dioxide (SiO2) particles. The silica particles may be
mixed with one or more solvents, one or more binders, and one or more additives
in a container (not shown). The silica particles may be mixed with the one or more
solvents and one or more binders to prepare the silica slurry 102.
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[56] The vertical extrusion apparatus 200 may have the feed-hopper 104, the
barrel 106, the one or more screws 108 of which first and second screws 108a-
108b are shown, the plurality of heaters 110 of which first through nth heaters
(here n is an integer) 110a-110n are shown, the die header 114, the iris frame 116,
the drying furnace 118, the gas tank 120, the debinding furnace 122. The barrel
106 of the vertical extrusion apparatus 200 may be arranged along a Y-Y direction
(i.e., a vertical direction) of a direction index of FIG. 2.
[57] The feed-hopper 104 may be adapted to hold the silica slurry 102. The
feed-hopper 104 may be further adapted to feed the silica slurry 102 to the barrel
106. Specifically, the silica slurry 102 may be fed into the barrel 106 under the
action of gravity. In other words, the silica slurry 102 may fall from the
feed-hopper 104 under the effect of system external forces (i.e., natural gravity or
vibrations or pressure from backward systems). In some aspects of the present
disclosure, the feed-hopper 104 may have a conical shape.
[58] The barrel 106 may have the inlet end 106a and the outlet end 106b. The
barrel 106 may be disposed beneath the feed-hopper 104. Specifically, the inlet
end 106a may be disposed beneath the feed-hopper 104 such that the barrel 106
receives the silica slurry from the feed-hopper 104.
[59] The one or more screws 108a and 108b may be disposed within the barrel
106. Aspects of the present disclosure are intended to include and/or otherwise
cover any number of screws. The one or more screws 108a and 108b may be
adapted to rotate within the barrel 106. Specifically, the one or more screws 108a
and 108b may be adapted to rotate within the barrel 106 by way of a motor 109.
The one or more screws 108a and 108b, upon rotation, may further be adapted to
properly mix the one or more solvents and the one or more binders in the silica
slurry 102. Furthermore, the one or more screws 108a and 108b, upon rotation
may be adapted to provide thrust to the silica slurry 102 that may push the silica
slurry 102 towards the die header 114. Specifically, the one or more screws 108a
and 108b, upon rotation, may push the silica slurry 102 towards the outlet end
106b such that the silica slurry 102 ejects out from the barrel 106. Furthermore,
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the one or more screws 108a and 108b may force the silica slurry 102 to shear
against walls of the barrel 106 thereby developing heat due to viscous dissipation.
[60] In some aspects of the present disclosure, each screw of the one or more
screws 108a and 108b may be the helical screw. The one or more screws 108a and
108b may be moved in one of, the clockwise direction and the counter-clockwise
direction. In some exemplary aspects of the present disclosure, each screw of the
one or more screws 108a and 108b may rotate in the clockwise direction and
according to right-hand cork screw rule, the one or more screws 108a and 108b
may push the silica slurry 102 towards the outlet end 106b of the barrel 106.
[61] In some exemplary aspects of the present disclosure, the one or more
screws may be the pair of screws i.e., 108a and 108b. The pair of screws 108 and
108b may facilitate proper mixing of the silica slurry 102 and may leave lesser
number of dead spaces present in the silica slurry 102. Since, residence time of the
silica slurry 102 in the vertical extrusion apparatus 200 may be lesser as compared
to the horizontal extrusion apparatus 100, therefore, the pair of screws are
advantageous for the vertical extrusion apparatus 200.
[62] In some aspects of the present disclosure, expression for discharge
pressure associated to each screw of the one or more screws may be
?? = p ?? ??3 ?? (?????? T)2
(12??µ)
Or, ?? = 0.02163 ?? ??3 ??
(??µ)
where: -
P is pressure flow
D is diameter of each screw of the one or more screws 108a and 108b;
H is depth of a channel of each screw of the one or more screws 108a and 108b;
p is discharge pressure;
L is length of metering section of each screw of the one or more screws 108a and
108b;
µ is coefficient of viscosity; and
16/41
T is angle of helix of each screw of the one or more screws 108a and 108b.
[63] The first through nth heaters 110a-110n may be disposed at the periphery
of the barrel 106. The first through nth heaters 110a-110n may be adapted to
provide heat to the silica slurry 102 that may be present in the barrel 106. The first
through nth heaters 110a-110n may initiate polymerization of the silica slurry 102
that facilitates the one or more binders to provide ample flexibility to soot
structure of the silica slurry 102. Furthermore, the first through nth heaters
110a-110n may prevent too much packing of the soot structure, which may allow
the gas, if any, to vent out from the soot structure and thereby eliminating cracks
in the soot preform 130 (i.e., a clad soot). The first through nth heaters 110a-110n
may provide the sufficient temperature (for example, that may lie in a range of
700 to 800 degrees Celsius) to facilitate efficient polymerization or reconstruction
of the silica slurry 102 based on the one or more binders along with the other
additives.
[64] The die header 114 may be coupled to the barrel 106. The die header 114
may have a core rod holder 114a. The core rod 128 may be inserted into the die
header 114 through the bottom of die header 114. The core rod 128 may be held in
the core rod holder 114a. The die header 114 may be adapted to push the core rod
128. The core rod 128 may be placed at a center of the die header 114. The core
rod 128 may form back-bone/supporting structure of the soot preform 130. The
die header 114 may further be adapted to receive the silica slurry 102 from the
outlet end 106b of the barrel 106. Specifically, the silica slurry 102 may be
cladded on the core rod 128 to form the soot preform 130. The die header 114
may be designed such that the die header 114 co-extrudes the core rod 128. The
speed of feeding the core rod 128 may synchronize with the speed of extrusion of
the clad soot. The synchronization in the speed of feeding the core rod 128 and the
speed of extrusion of the clad soot eliminates stresses in the optical fiber 142 and
ensures proper adherence of the clad soot over the core rod 128.
[65] The iris frame 116 may be disposed underneath the die header 114. The
iris frame 116 may not be aligned on a same axis as of the barrel 106. Specifically,
the iris frame 116 may be disposed or aligned offset from the axis of the barrel
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106 (as can be clearly seen through FIG. 2C). The iris frame 116 may be adapted
to form the conical portion 134 at the end of the soot preform 130. The conical
portion 134 may prevent splitting of the soot preform 130. Specifically, the iris
frame 116 may be adapted to form the conical portion 134 having the desired
length and the slope at the end of the soot preform 130. For example, the iris
frame 116 may be adapted to form the conical portion 134 at the bottom end of
the soot preform 130.
[66] The drying furnace 118 may be disposed beneath the iris frame 116. The
drying furnace 118 may have the first inlet 118a and the first outlet 118b. The
drying furnace 118 may be adapted to eliminate moisture that is present in the
soot preform 130 to produce the dried soot preform 132.
[67] The gas tank 120 may have the second inlet 120a, the second outlet 120b,
and the vent 120c. The drying furnace 118 may be coupled to the gas tank 120.
Specifically, the first inlet 118a of the drying furnace 118 may be coupled to the
second outlet 120b of the gas tank 120. The second inlet 120a may be adapted to
allow air to enter into the gas tank 120. In some examples, the second inlet 120a
may be adapted to allow the air having temperature of about 25o Celsius. The gas
tank 120 may be adapted to mix the air with the incoming gas from de-binding
furnace through 120c gas to produce the hot gas required for drying. The second
outlet 120b may be adapted to exit the hot gas. In some examples, the hot gas may
have a temperature range of about 60-100 o Celsius. The first inlet 118a may
therefore, facilitate the hot gas to enter to the drying furnace 118. The hot gas may
come in contact with the soot preform 130 such that the heat provided by the hot
gas eliminates the moisture from the soot preform 130 in the drying furnace 118.
[68] The debinding furnace 122 may be coupled to the drying furnace 118. The
debinding furnace 122 may have the third inlet 122a and the third outlet 122b.
The third outlet 122b may be coupled to the vent 120c. The third inlet 122a may
be adapted to allow air to enter into the debinding furnace 122. The debinding
furnace 122 may be adapted to eliminate the one or more binders along with the
one or more additives from the soot preform 130. The debinding furnace 122 may
further be adapted to eliminate chemisorbed OH molecules (i.e., chemisorbed
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moisture) from the soot preform 130. Specifically, the soot preform 130 may be
treated for about 1 to 3 hours in the debinding furnace 122 at the temperature
range of about 800o Celsius to 1200 o Celsius. The gas tank 120 may have a fourth
outlet 122c. The fourth outlet 122c may be coupled to the vent 120c to purge out
the debinded gases. The debinding furnace 122 may be, upon removal of the one
or more binders and the one or more additives, adapted to produce the green body
136. The green body 136 may be transferred to the optical fiber manufacturing
apparatus 101 to manufacture the optical fiber 142 (as explained hereinabove in
context to FIG. 1A).
[69] In some aspects of the present disclosure, the drying furnace 118 and the
debinding furnace 122 may not form the part of the horizontal extrusion apparatus
100 and the vertical extrusion apparatus 200. In such a scenario, the soot preform
130 may be obtained from the horizontal and vertical extrusion apparatuses 100
and 200 such that the soot preform 130 is then transferred to the drying furnace
118. The drying furnace 118 may be adapted to eliminate moisture from the soot
preform and the debinding furnace 122 may be adapted to eliminate the one or
more binders and the one or more additives from the soot preform 130 to produce
the green body 136.
[70] In some aspects of the present disclosure, the soot preform 130 may be
manufactured in semi-continuous batch process (hereinafter referred to as “batch
process”). The batch process may require manufacturing of the soot preform 130
such that the soot preform 130 may be removed from the vertical extrusion
apparatus 200.
[71] In some preferred aspects of the present disclosure, to manufacture the
optical fiber 142, the horizontal extrusion apparatus 100 may be preferred over the
vertical extrusion apparatus 200.
[72] In some aspects of the present disclosure, 70% of total amount of the silica
particles may have a size of about 16 microns and remaining amount of silica
particles of the total amount of the silica particles may have a size that may be
smaller than 16 microns.
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[73] In some aspects of the present disclosure, the one or more solvents may be
organic solvents. In some other aspects of the present disclosure, the one or more
solvents may be inorganic solvents. In some other aspects of the present
disclosure, the one or more solvents may be water-based solvents. In some other
aspects of the present disclosure, the one or more solvents may be alcohol-based
solvents. In some other aspects of the present disclosure, the one or more solvents
may be ketone-based solvents. In some other aspects of the present disclosure, the
one or more solvents may have a quantity that may lie in a range of about 10% to
30% with respect to the amount of silica particles.
[74] In some aspects of the present disclosure, the one or more binders and the
one or more additives may be organic binders. In some other aspects of the
present disclosure, the one or more binders and the one or more additives may be
added in a range of about 0.1% to 5% with respect to amount of the silica
particles. In some other aspects of the present disclosure, the one or more binders
may include but not limited to, polypropylene carbonate, polyvinyl alcohol,
polystyrene, camphor, gelatin-based agar, and may include other stabilizing agents
like the dispersant, polymerizing initiator, plasticizer and the like. Aspects of the
present disclosure are intended to include and/or otherwise cover any kind of
known and later developed stabilized binder. In some other aspects of the present
disclosure, the one or more binders may be monomers in order to form a cage-like
structure of the silica slurry 102. In some other aspects of the present disclosure,
the polymeric units (such as hydrocolloids) may undergo new cage like structure
using hydrogen bonds. The cage-like structure of the silica slurry 102 may
facilitate to adhere the silica particles into soot such that the one or more binders
may bind the silica particles to provide the soot preform 130 of desired shape and
size.
[75] In some aspects of the present disclosure, the silica slurry 102 may be a
combination of the one or more solvents, silica particles, and the one or more
binders.
[76] In some exemplary aspects of the present disclosure, loading of silica
particles in the silica slurry 102 may lie in a range from about 40% to 80%. The
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one or more binders may be agar gel may lie in a range from about 1% to 3%. The
remaining amount of the silica slurry 102 may be water (i.e., solvent). The amount
of solvent may lie in a range of 17% to 59%.
[77] In some aspects of the present disclosure, the drying furnace 118 may be
provided with a heating element (not shown) that raises temperature of the gas
such that the gas eliminates the moisture present in the soot preform 130.
[78] In some aspects of the present disclosure, one or more dispersants may be
added in the silica slurry 102 to stabilize the silica slurry 102.
[79] In some aspects of the present disclosure, the iris frame 116 may be used
to extrude pure silica core rods (i.e., by double extrusion) and a core preform (i.e.,
by double extrusion).
[80] FIG. 2B illustrates a front view (Y-Z plane) of the extrusion apparatus 200
of FIG. 2A for manufacturing the soot preform 130.. Specifically, FIG. 2B
illustrates the front view of the vertical extrusion apparatus 200. The vertical
extrusion apparatus 200 may further have a barrel extension tube 202. The barrel
extension tube 202 may have a first end 202a and a second end 202b. The first
end 202a of the extension tube 202 may be coupled to the outlet end 106b of the
barrel 106. The second end 202b of the extension tube 202 may be coupled to the
die header 114. The barrel extension tube 202 may be adapted to allow passage of
the silica slurry 102 from the barrel 106 to the die header 114. Specifically, the
silica slurry 102 may be pushed from the outlet end 106b to the first end 202a
such that the silica slurry 102 enters the barrel extension tube 202 from the first
end 202a. The silica slurry 102 may further be pushed within the barrel extension
tube 202. The silica slurry 102 may reach up to the second end 202b such that the
silica slurry 102 enters the die header 114 from the second end 202b. As the die
header 114 and the iris frame 116 is disposed or aligned offset from the axis of the
barrel 106, the core rod 128 may be continuously pushed down using the core rod
holder 112 which ensures continuous manufacturing of the soot preform 130.
[81] FIG. 3 illustrates an iris frame 116 of the extrusion apparatus of FIG. 1A
and FIG. 2. The iris frame 116 may include a plurality of vanes 302 of which first
through sixth vanes 302a-302f are shown. The iris frame 116 may further include
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an outside rim 304. The iris frame 116 may be coupled to a microcontroller (not
shown). The microcontroller may be a programmable logic controller (PLC). Each
vane of the first through sixth vanes 302a-302f may be adapted to move in a radial
direction of the iris frame 116. Specifically, the movement of each vane of the
first through sixth vanes 302a-302f may be controlled by the microcontroller.
Upon movement of each vane of the first through sixth vanes 302a-302f, a central
orifice 306 may be created such that the central orifice 306 may become narrower
or wider. Specifically, each vane of the first through sixth vanes 302a-302f may
extend such that upon extension, the central orifice 306 may become narrower,
i.e., a diameter of the central orifice 306 may be reduced. Each vane of the first
through sixth vanes 302a-302f may retract such that upon retraction, the central
orifice 306 may become wider, i.e., the diameter of the central orifice 306 may be
increased. Therefore, upon movement of each vane of the first through sixth vanes
302a-302f, the iris frame 116 may be adapted to control or adjust the diameter of
the central orifice 306 in order to control or adjust the diameter of the soot
preform 130. Upon retraction, each vane of the first through sixth vanes
302a-302f may slide into the outside rim 304 such that a portion of each vane of
the first through sixth vanes 302a-302f is accommodated in the outside rim 304.
The iris frame 116 may be adapted to form the conical portion 134 at the end of
the soot preform 130. Specifically, variation in the diameter of the central orifice
306 may facilitate the iris frame 116 to adjust or vary dimensions of the conical
portion 134 i.e., to form the conical portion 134 of the desired length and the slope
at the beginning and end of the soot preform 130. Furthermore, the variation in the
diameter of the central orifice 306 may facilitate the iris frame 116 to control
dimensions of the soot preform 130. In order to control dimensions of the soot
preform 130 and the conical portion 134, a user may set required values of
dimensions of the soot preform 130 and the conical portion 134 such that
microcontroller actuates an iris motor (not shown). Upon actuation, the iris motor
may be adapted to, based on the required values of dimensions set by the user,
control variation in the diameter of the central orifice 306 that may further control
the dimensions of the soot preform 130 and the conical portion 134. For example,
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the iris frame 116 may be adapted to continuously vary the diameter of the soot
preform 130 that may lie in range of 35 mm to 350 mm with a deviation of + 1
mm.
[82] In some aspects of the present disclosure, each vane of the first through
sixth vanes 302a-302f may be made up of metal. In some other aspects of the
present disclosure, each vane of the first through sixth vanes 302a-302f may have
smooth surface finish. The smooth surface finish of each vane of the first through
sixth vanes 302a-302f may eliminate any irregularity in the surface of the soot
preform 130.
[83] FIG. 4 illustrates working of the iris frame 116 of FIG. 3. Specifically,
FIG. 4 illustrates increase in diameter of the central orifice 306. The diameter of
the central orifice 306 of the iris frame 116 may be increased from an initial
diameter (that allows insertion of the core rod 128) to a final diameter (i.e.,
diameter of the soot preform 130, which is an outer diameter of the clad soot).
[84] FIG. 5 illustrates a flow-chart of a method 500 for manufacturing the
optical fiber 142. Specifically, FIG. 5 shows the method 500 for manufacturing
the soot preform 130 by the one of, the horizontal extrusion apparatus 100 and the
vertical extrusion apparatus 200 (hereinafter collectively referred to and
designated as “the extrusion apparatus 100 and 200”) and then manufacturing the
optical fiber 142. The method 500 may employ following steps to manufacture the
optical fiber 142.
[85] At step 502, silica slurry 102 may be prepared. Specifically, the silica
particles may be mixed with the one or more solvents, the one or more binders,
and the one or more additives in the container (not shown). The silica particles
may be mixed with the one or more solvents and the one or more binders to
prepare the silica slurry 102. In some aspects of the present disclosure, the
extrusion apparatus 100 and 200 may convert the silica slurry 102 into a
semi-solid silica slurry.
[86] In some aspects of the present disclosure, 70% of silica particles from total
amount of the silica particles may have dimension greater than 16 microns and
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30% of silica particles from total amount of the silica particles may have
dimension smaller than 16 microns.
[87] In some aspects of the present disclosure, the one or more solvents may be
organic solvents. In some other aspects of the present disclosure, the one or more
solvents may be inorganic solvents. In some other aspects of the present
disclosure, the one or more solvents may be water-based solvents. In some other
aspects of the present disclosure, the one or more solvents may be alcohol-based
solvents. In some other aspects of the present disclosure, the one or more solvents
may be ketone-based solvents. In some other aspects of the present disclosure, the
one or more solvents may have a quantity that may lie in a range of about 10% to
30% with respect to the amount of silica particles.
[88] In some aspects of the present disclosure, the one or more binders may be
organic binders. In some other aspects of the present disclosure, the one or more
binders may be added in a range of about 0.1% to 5% with respect to amount of
the silica particles. In some other aspects of the present disclosure, the one or
more binders may include but not limited to, polypropylene carbonate, polyvinyl
alcohol, polystyrene, camphor, gelatin-based agar, and may include other
stabilizing agents like the dispersant, polymerizing initiator, plasticizer, and the
like. Aspects of the present disclosure are intended to include and/or otherwise
cover any kind of known and later developed stabilized binder. In some other
aspects of the present disclosure, the one or more binders (such as hydrocolloids)
may be monomers in order to form a cage-like structure of the silica slurry 102. In
some other aspects of the present disclosure, the polymeric units may undergo
new cage like structure using hydrogen bonds. The cage-like structure of the silica
slurry 102 may facilitate to adhere the silica particles into soot such that the one or
more binders may bind the silica particles to provide the soot preform 130 of
desired shape and size.
[89] In some aspects of the present disclosure, the silica slurry 102 may have
silica particles that may lie in a range of 40% to 80%, the one or more binders that
may lie in range of 1% to 3%, and the one or more solvents that may lie in range
of 17% to 59%.
24/41
[90] At step 504, the silica slurry 102 may be transferred to the feed-hopper
104.
[91] At step 506, from the feed-hopper 104, the silica slurry 102 may be fed to
the barrel 106. Specifically, the silica slurry 102 may be fed to the inlet end 106a
of the barrel 106 under the action of gravity. In other words, the silica slurry 102
may fall from the feed-hopper 104 under the effect of system external forces (i.e.,
natural gravity or vibrations or pressure from backward systems).
[92] At step 508, the extrusion apparatus 100 and 200 by way of the barrel 106,
may push the silica slurry 102. Specifically, the silica slurry 102 may be pushed
by way of the one or more screws 108a and 108b that may be disposed within the
barrel 106. The one or more screws 108a and 108b may be adapted to rotate
within the barrel 106. The one or more screws 108a and 108b, upon rotation, may
be adapted to push the silica slurry 102 from the inlet end 106a towards the outlet
end 106b of the barrel 106. From the outlet end 106b of the barrel 106, the silica
slurry 102 may be pushed towards the die header 114, upon rotation of the one or
more screws 108a and 108b.
[93] In some aspects of the present disclosure, the extrusion apparatus 100 and
200, by way of the one or more screws 108a and 108b may be adapted to mix the
silica slurry 102. In some aspects of the present disclosure, the extrusion apparatus
100 and 200 may be adapted to convert the silica slurry 102 into a semi-solid
silica slurry.
[94] At step 510, the extrusion apparatus 100 and 200 by way of the die header
114, may extrude the core rod 128. The die header 114 may further be adapted to
receive the silica slurry 102 from the outlet end 106b of the barrel 106.
Specifically, the silica slurry 102 may be cladded on the core rod 128 to form the
soot preform 130.
[95] At step 512, the extrusion apparatus 100 and 200, by way of the die header
114, may coat the clad soot over the core rod 128. Specifically, the die header 114
may be designed such that the die header 114 co-extrudes the core rod 128 to
obtain the soot preform 130. The speed of feeding the core rod 128 may
synchronize with the speed of extrusion of the clad soot. The synchronization in
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the speed of feeding the core rod 128 and the speed of extrusion of the clad soot
eliminates stresses in the soot preform 130 and ensures proper cladding of the soot
over the core rod 128.
[96] At step 514, the extrusion apparatus 100 and 200, by way of the iris frame
116, may form the conical portion 134 at the end of the soot preform 130.
Specifically, the iris frame 116 may be adapted to form the conical portion 134
having a desired length and a slope at the end of the soot preform 130. For
example, the iris frame 116 may be adapted to form the conical portion 134 at the
top and bottom end of the soot preform 130.
[97] At step 516, by way of the drying furnace 118, the soot preform 130 may
be dried to produce a dried soot preform 132. Specifically, the drying furnace 118
may be adapted to eliminate physisorbed moisture that is present in the soot
preform 130. In some aspects of the present disclosure, the drying furnace 118
may be coupled to the extrusion apparatus 100 and 200. In some aspects of the
present disclosure, the drying furnace 118 may not be coupled to the extrusion
apparatus 100 and 200.
[98] At step 518, by way of the debinding furnace 122, may eliminate the one
or more stabilized binders along with other one or more additives from the dried
soot preform 132 may be eliminated. Specifically, the debinding furnace 122 may
further be adapted to eliminate remaining physisorbed and most of the
chemisorbed OH molecules (i.e., chemisorbed moisture) from the dried soot
preform 132. Furthermore, the soot preform 130 or the dried soot preform 132
may be treated for about 1 to 3 hours in the debinding furnace 122 at a
temperature range of about 800o Celsius to 1200o Celsius. The fourth outlet 122c
may be adapted to exit debinded gases from the debinding furnace 122. The
debinding furnace 122 may be, upon removal of the one or more binders, adapted
to produce the green body 136. In an aspect of the present disclosure, the dried
soot preform 132 may be transferred to the debinding furnace 122 when debinding
of the dried soot preform 132 is required. In some aspects of the present
disclosure, the debinding furnace 122 may be coupled to the extrusion apparatus
26/41
100 and 200. In some aspects of the present disclosure, the debinding furnace 122
may not be coupled to the extrusion apparatus 100 and 200.
[99] At step 520, by way of the sinter furnace 124, the dried soot preform 132
or the green body 136 may be sintered to obtain the glass preform 138 from the
dried soot preform 132 or the green body 136. Specifically, while sintering, the
sinter furnace 124 may be adapted to close pores in the soot preform 130. In an
aspect of the present disclosure, the dried soot preform 132 may be directly
transferred to the sinter furnace 124 when debinding of the dried soot preform 132
is not required.
[100] At step 522, by way of the draw furnace 126, may draw the glass preform
138 to manufacture the optical fiber 142. Specifically, to draw the optical fiber
142 from the glass preform 138. Furthermore, the conical portion 134 may be
melted at high temperature to draw the optical fiber 142.
[101] Furthermore, to extrude the clad soot, the steps from 502 to 508 may be
repeated. Upon, pushing the silica slurry 102 towards the die header 114, the clad
soot may be extruded. Specifically, the silica slurry 102 may eject out from the die
header 114 to form the clad soot. FIG. 6 illustrates a flow-chart of a method 600
for manufacturing a multilayer preform. Specifically, FIG. 6 shows the method
600 for manufacturing the multilayer preform by the one of, the horizontal
extrusion apparatus 100 and the vertical extrusion apparatus 200 (hereinafter
collectively referred to and designated as “the extrusion apparatus 100 and 200”).
The extrusion apparatus 100 and 200 may employ following steps to manufacture
the multilayer preform.
[102] At step 602, the silica slurry 102 may be prepared. Specifically, the silica
particles may be mixed with the one or more solvents, the one or more binders,
and the one or more additives in the container (not shown). The silica particles
may be mixed with the one or more solvents and the one or more binders to
prepare the silica slurry 102.
[103] At step 604, the silica slurry 102 may be transferred to the feed-hopper
104.
27/41
[104] At step 606, from the feed-hopper 104, the silica slurry 102 may be fed to
the barrel 106. Specifically, the silica slurry 102 may be fed to the inlet end 106a
of the barrel 106 under the action of gravity. In other words, the silica slurry 102
may fall from the feed-hopper 104 under the effect of system external forces (i.e.,
natural gravity or vibrations or pressure from backward systems).
[105] At step 608, the extrusion apparatus 100 and 200, by way of the barrel
106, may push the silica slurry 102. Specifically, the silica slurry 102 may be
pushed by way of the one or more screws 108a and 108b that may be disposed
within the barrel 106. The one or more screws 108a and 108b may be adapted to
rotate within the barrel 106. The one or more screws 108a and 108b, upon
rotation, may be adapted to push the silica slurry 102 towards the outlet end 106b
of the barrel 106. From the outlet end 106b of the barrel 106, the silica slurry 102
may be pushed towards the die header 114, upon rotation of the one or more
screws 108a and 108b.
[106] At step 610, the extrusion apparatus 100 and 200, by way of the die header
114, may extrude the core rod 128. The die header 114 may further be adapted to
receive the silica slurry 102 from the outlet end 106b of the barrel 106.
Specifically, the silica slurry 102 may be cladded on the core rod 128.
Furthermore, the die header 114 may be adapted to extrude a layer over the core
rod 128. The die header 114 may therefore be adapted to extrude multiple layers
on the core rod 128 i.e., multiple layered core rod. The multiple layered core rod
128 may then be used to form the multilayer preform.
[107] At step 612, the extrusion apparatus 100 and 200, by way of the die header
114, may coat the clad soot over the core rod 128. The die header 114 may further
be adapted to coat the clad soot over the outermost layer from the multiple layers
that may be coated on the core rod 128. Specifically, the die header 114 may be
designed such that the die header 114 co-extrudes the core rod 128 to obtain the
multilayer preform. The speed of feeding the layer over the core rod 128 may
synchronize with the speed of extrusion of the clad soot. The synchronization in
the speed of feeding the layer over the core rod 128 and the speed of extrusion of
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the clad soot eliminates stresses in the multilayer preform and ensures proper
deposition of the clad soot over the core rod 128.
[108] At step 614, the extrusion apparatus 100 and 200, by way of the iris frame
116, may form the conical portion 134 at the end of the multilayer preform.
Specifically, the iris frame 116 may be adapted to form the conical portion 134
having a desired length and a slope at the end of the multilayer preform. For
example, the iris frame 116 may be adapted to form the conical portion 134 at the
bottom end of the multilayer preform.
[109] At step 616, the extrusion apparatus 100 and 200, by way of the drying
furnace 118, may dry the multilayer preform. Specifically, the drying furnace 118
may be adapted to eliminate physisorbed moisture that is present in the multilayer
preform.
[110] At step 618, the extrusion apparatus 100 and 200, by way of the debinding
furnace 122, may eliminate the one or more binders along with other one or more
additives from the multilayer preform. Specifically, the debinding furnace 122
may further be adapted to eliminate chemisorbed OH molecules (i.e., chemisorbed
moisture) from the multilayer preform. Furthermore, the multilayer preform may
be treated for about 1 to 3 hours in the debinding furnace 122 at a temperature
range of about 800o Celsius to 1200 o Celsius. The fourth outlet 122c may be
adapted to exit the debinded gases from the debinding furnace 122. The debinding
furnace 122 may be, upon removal of the one or more binders, adapted to produce
the green body 136.
[111] At step 620, by way of the sinter furnace 124, may sinter the green body
136 to obtain the multilayer preform from the green body 136. Specifically, while
sintering, the sinter furnace 124 may be adapted to close pores in the multilayer
preform.
[112] At step 622, by way of the draw furnace 126, may draw the multilayer
preform to manufacture the optical fiber 142. Specifically, to draw the optical
fiber 142 from the multilayer preform 132, the conical portion 134 may be
softened in presence of one or more gases. Furthermore, the conical portion 134
may be melted at high temperature to draw the optical fiber 142.
29/41
[113] In some aspects of the present disclosure, different kinds of dopants (such
as Fluorine, P2O5) and powders may be added in silica particles to prepare
respective slurries such that the respective slurries form the multilayer preform.
[114] Furthermore, to extrude the clad soot, the steps from 602 to 608 may be
repeated. Upon pushing the silica slurry 102 towards the die header 114, the clad
soot may be extruded. Specifically, the silica slurry 102 may eject out from the die
header 114 to form the clad soot and deposit over the core rod 128.
[115] FIG. 7 illustrates a flow-chart of a method 700 for manufacturing a hollow
cylinder preform. Specifically, FIG. 7 shows the method 700 for manufacturing
the hollow cylinder preform by the one of, the horizontal extrusion apparatus 100
and the vertical extrusion apparatus 200 (hereinafter collectively referred to and
designated as “the extrusion apparatus 100 and 200”). The extrusion apparatus
100 and 200 may employ following steps to manufacture the hollow cylinder
preform.
[116] At step 702, the silica slurry 102 may be prepared. Specifically, the silica
particles may be mixed with the one or more solvents, the one or more binders,
and the one or more additives in the container (not shown). The silica particles
may be mixed with the one or more solvents, the one or more binders, and the one
or more additives to prepare the silica slurry 102.
[117] At step 704, the silica slurry 102 may be transferred to the feed-hopper
104.
[118] At step 706, from the feed-hopper 104, the silica slurry 102 may be fed to
the barrel 106. Specifically, the silica slurry 102 may be fed to the inlet end 106a
of the barrel 106 under the action of gravity. In other words, the silica slurry 102
may fall from the feed-hopper 104 under the effect of gravity.
[119] At step 708, the extrusion apparatus 100 and 200, by way of the barrel
106, may push the silica slurry 102. Specifically, the silica slurry 102 may be
pushed by way of the one or more screws 108a and 108b that may be disposed
within the barrel 106. The one or more screws 108a and 108b may be adapted to
rotate within the barrel 106. The one or more screws 108a and 108b, upon
rotation, may be adapted to push the silica slurry 102 towards the outlet end 106b
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of the barrel 106. From the outlet end 106b of the barrel 106, the silica slurry 102
may be pushed towards the die header 114, upon rotation of the one or more
screws 108a and 108b.
[120] At step 710, the extrusion apparatus 100 and 200, by way of the die header
114, may deposit the silica slurry 102, while manufacturing the hollow cylinder
preform. Specifically, the silica slurry 102 may be cladded through an annular
passage around an obstruction in the die header 114. The obstruction may be the
core rod 128. In some examples, the obstruction may be a mandrel that may be
used instead of the core rod 128.
[121] At step 712, the extrusion apparatus 100 and 200, by way of the die header
114, may extrude a hollow cylinder. Specifically, the silica slurry 102 may eject
out from the die header 114 to form the hollow cylinder.
[122] At step 714, the extrusion apparatus 100 and 200, by way of the drying
furnace 118, may dry the hollow cylinder. Specifically, the drying furnace 118
may be adapted to eliminate moisture that is present in the hollow cylinder.
[123] At step 716, the extrusion apparatus 100 and 200, by way of the debinding
furnace 122, may eliminate the one or more binders (for example stabilized
binders) from the hollow cylinder. Specifically, the debinding furnace 122 may
further be adapted to eliminate chemisorbed OH molecules (i.e., chemisorbed
moisture) from the hollow cylinder. Furthermore, the hollow cylinder may be
treated for about 1 to 3 hours in the debinding furnace 122 at a temperature range
of about 800o Celsius to 1200 o Celsius. The third outlet 122b may be adapted to
exit the debinded gases from the debinding furnace 122. The debinding furnace
122 may be, upon removal of the one or more binders from the hollow cylinder,
adapted to produce the green body 136.
[124] At step 718, by way of the sinter furnace 124, may sinter the green body
136 to obtain the hollow cylinder preform. Specifically, while sintering, the sinter
furnace 124 may be adapted to close pores in the hollow cylinder preform.
[125] At step 720, inserting, by way of rod in cylinder (RIC) process, the core
rod 128 in the hollow cylinder to obtain the glass preform 138. The glass preform
138 may further be used to draw the optical fiber 142 from the draw furnace 126.
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[126] In some aspects of the present disclosure, to manufacture the hollow
cylinder preform, an obstruction at the center of the die header 114 may guide the
silica slurry 102 through the annular passage around the obstruction.
[127] FIG. 8 illustrates a flow-chart of a method 800 for manufacturing a
multicore rod preform. Specifically, FIG. 8 shows the method 800 for
manufacturing the multicore rod preform by the one of, the horizontal extrusion
apparatus 100 and the vertical extrusion apparatus 200 (hereinafter collectively
referred to and designated as “the extrusion apparatus 100 and 200”). The
extrusion apparatus 100 and 200 may employ following steps to manufacture the
multicore rod preform.
[128] At step 802, the silica slurry 102 may be prepared. Specifically, the silica
particles may be mixed with the one or more solvents, the one or more binders,
and the one or more additives in the container (not shown). The silica particles
may be mixed with the one or more solvents and the one or more binders to
prepare the silica slurry 102.
[129] At step 804, the silica slurry 102 may be transferred to the feed-hopper
104.
[130] At step 806, from the feed-hopper 104, the silica slurry 102 may be fed to
the barrel 106. Specifically, the silica slurry 102 may be fed to the inlet end 106a
of the barrel 106 under the action of gravity. In other words, the silica slurry 102
may fall from the feed-hopper 104 under the effect of gravity.
[131] At step 808, the extrusion apparatus 100 and 200, by way of the barrel
106, may push the silica slurry 102. Specifically, the silica slurry 102 may be
pushed by way of the one or more screws 108a and 108b that may be disposed
within the barrel 106. The one or more screws 108a and 108b may be adapted to
rotate within the barrel 106. The one or more screws 108a and 108b, upon
rotation, may be adapted to push the silica slurry 102 towards the outlet end 106b
of the barrel 106. From the outlet end 106b of the barrel 106, the silica slurry 102
may be pushed towards the die header 114, upon rotation of the one or more
screws 108a and 108b.
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[132] At step 810, the extrusion apparatus 100 and 200, by way of the die header
114, may deploy multiple obstructions at the outlet of the die header 114.
Specifically, the die header 114 may be adapted to deploy multiple obstructions at
the outlet of the die header 114 as per required pitch i.e., core to core spacing.
[133] At step 812, the extrusion apparatus 100 and 200, may push the silica
slurry through the die header 114 to produce cylinder with multiple holes having a
standard pitch circle diameter (PCD).
[134] At step 814, the extrusion apparatus 100 and 200, by way of the iris frame
116, may form the conical portion 134 at an end of the cylinder with multiple
holes. Specifically, the iris frame 116 may be adapted to form the conical portion
134 having a desired length and a slope at the end of the cylinder with multiple
holes. For example, the iris frame 116 may be adapted to form the conical portion
134 at the bottom end of the cylinder with multiple holes.
[135] At step 816, the extrusion apparatus 100 and 200, by way of the drying
furnace 118, may dry the cylinder with multiple holes. Specifically, the drying
furnace 118 may be adapted to eliminate moisture that is present in the cylinder
with multiple holes.
[136] At step 818, the extrusion apparatus 100 and 200, by way of the debinding
furnace 122, may eliminate the one or more binders (for example stabilized
binders) from the cylinder with multiple holes to produce the green body 136.
Specifically, the debinding furnace 122 may be adapted to eliminate chemisorbed
OH molecules (i.e., chemisorbed moisture) from the cylinder with multiple holes.
Furthermore, the cylinder with multiple holes may be treated for about 1 to 3
hours in the debinding furnace 122 at a temperature range of about 800 o Celsius
to 1200 o Celsius. The third outlet 122b may be adapted to exit the debinded gases
from the debinding furnace 122. The debinding furnace 122 may be, upon
removal of the one or more binders, adapted to produce the green body 136.
[137] At step 820, by way of the sinter furnace 124, may sinter the green body
136 to obtain a glass cylinder with multiple holes. Specifically, while sintering,
the sinter furnace 124 may be adapted to close pores in the green body 136 to
obtain the glass cylinder with multiple holes.
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[138] At step 822, inserting, by way of rod in cylinder (RIC) process, multiple
core rods in the glass cylinder to obtain the glass preform 138. The glass preform
138 may further be used to manufacture the multicore rod preform.
[139] FIG. 9 illustrates a flow-chart of a method 900 for manufacturing a hollow
clad tube (hollow preform). Specifically, FIG. 9 shows the method 900 for
manufacturing the hollow clad tube by the one of, the horizontal extrusion
apparatus 100 and the vertical extrusion apparatus 200 (hereinafter collectively
referred to and designated as “the extrusion apparatus 100 and 200”). The
extrusion apparatus 100 and 200 may employ following steps to manufacture the
hollow preform.
[140] At step 902, the silica slurry 102 may be prepared. Specifically, the silica
particles may be mixed with the one or more solvents, the one or more binders,
and the one or more additives in the container (not shown). The silica particles
may be mixed with the one or more solvents, the one or more binders, and the one
or more additives to prepare the silica slurry 102.
[141] At step 904, the silica slurry 102 may be transferred to the feed-hopper
104.
[142] At step 906, from the feed-hopper 104, the silica slurry 102 may be fed to
the barrel 106. Specifically, the silica slurry 102 may be fed to the inlet end 106a
of the barrel 106 under the action of gravity. In other words, the silica slurry 102
may fall from the feed-hopper 104 under the effect of gravity.
[143] At step 908, the extrusion apparatus 100 and 200, by way of the barrel
106, may push the silica slurry 102. Specifically, the silica slurry 102 may be
pushed by way of the one or more screws 108a and 108b that may be disposed
within the barrel 106. The one or more screws 108a and 108b may be adapted to
rotate within the barrel 106. The one or more screws 108a and 108b, upon
rotation, may be adapted to push the silica slurry 102 towards the outlet end 106b
of the barrel 106. From the outlet end 106b of the barrel 106, the silica slurry 102
may be pushed towards the die header 114, upon rotation of the one or more
screws 108a and 108b.
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[144] At step 910, the extrusion apparatus 100 and 200, by way of the die header
114, may extrude the hollow clad tube (glass tube). The silica slurry 102 may
eject out from the die header 114 to form the glass tube. Specifically, to form the
hollow clad tube, a solid cylindrical obstruction may be provided in the center of
the die header 114, that facilitates the die header 114 to extrude the hollow clad
tube. In some aspects of the present disclosure, multiple solid cylindrical
obstruction may be provided to form the hollow clad tube with multiple holes in
which multiple core rods can be inserted to obtain a multicore glass preform.
[145] At step 912, the extrusion apparatus 100 and 200, by way of the die header
114, may coat the clad soot over the glass tube.
[146] At step 914, the extrusion apparatus 100 and 200, by way of the drying
furnace 118, may dry a hollow clad tube soot. Specifically, the drying furnace 118
may be adapted to eliminate moisture that is present in the hollow clad tube soot.
[147] At step 916, the extrusion apparatus 100 and 200, by way of the debinding
furnace 122, may eliminate the one or more binders (for example stabilized
binders) from the hollow clad tube soot. Specifically, the debinding furnace 122
may further be adapted to eliminate chemisorbed OH molecules (i.e., chemisorbed
moisture) from the hollow clad tube soot. Furthermore, the hollow clad tube soot
may be treated for about 1 to 3 hours in the debinding furnace 122 at a
temperature range of about 800o Celsius to 1200 o Celsius. The third outlet 122b
may be adapted to exit the debinded gases from the debinding furnace 122. The
debinding furnace 122 may be, upon removal of the one or more binders from the
hollow clad tube soot, adapted to produce the green body 136.
[148] At step 918, the extrusion apparatus 100 and 200, by way of the sinter
furnace 124, may sinter the green body 136 to obtain the hollow clad tube.
[149] Thus, the extrusion apparatus 100 and 200, of the present disclosure
reduces wastage and increases deposition efficiency from 50% to 90%. The
extrusion apparatus 100 and 200 manufactures the optical fiber 142, without
producing any combustible gas. Surface cracking of the soot preform 130 is
reduced. Further, the extrusion apparatus 100 and 200 reduces the scrap, which
avoids wastage of raw material while producing the conical portion 134. For
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example, the reduction in wastage is from 20% to 10% or even less. The extrusion
apparatus 100 and 200 is used to manufacture a variety of articles, for example,
handle rods, core preforms, core rods, multicore preforms, and clad preforms. The
iris frame 116 of the extrusion apparatus 100 and 200 facilitates in manufacturing
of both, the core rods and a clad deposition on a cladding using a single extrusion
apparatus.
[150] 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:We Claim(s):
1. A method (500) for manufacturing an optical fiber (142) the method (500)
comprising:
forming a soot preform (130) using an extrusion apparatus (100, 200),
comprising:
preparing (502) silica slurry (102) by mixing one or more solvents,
one or more binders, one or more additives, and silica particles;
pushing (508), by way of one or more screws (108) disposed within
a barrel (106), the silica slurry (102) from an inlet end (106a) to an
outlet end (106b) of the barrel (106); and
extruding (510), by way of a die header (114) such that the silica
slurry (102) is cladded on a core rod (128) to form the soot preform
(130), wherein the die header (114) comprises an iris frame (116) to
vary a diameter of the soot preform (130);
drying (516), by way of a drying furnace (118), the soot preform (130) for
eliminating physisorbed moisture present in the soot preform (130), such that
upon drying a dried soot preform (132) is produced;
sintering (520), by way of a sinter furnace (124), the dried soot preform
(132) to obtain a glass preform (138); and
drawing (522), by way of a draw furnace (126), the glass preform (138) to
manufacture the optical fiber (142).
2. The method as claimed in claim 1, comprising debinding (518), by way of a
debinding furnace (122), the dried soot preform (132) for eliminating the one
or more stabilized binders along with one or more additives from the dried soot
preform (132) such that upon debinding, a green body (136) is produced; and
sintering, sintering (520), by way of a sinter furnace (124), the green body
(136) to obtain the glass preform (138).
3. The method (500) as claimed in claim 1, wherein, to form a conical portion
(134) at an end of the soot preform (130) by the iris frame (116), the method
(500) comprising moving a plurality of vanes (302) in a radial direction of the
iris frame (116) to control a diameter of a central orifice (306) that controls the
diameter of the soot preform (130), wherein the diameter of the central orifice
(306) is varied in a range of 35 millimeters (mm) to 350 mm.
4. The method (500) as claimed in claim 1, wherein (i) 70% of silica particles of
the silica particles have dimension greater than 16 microns and (ii) 30% of
silica particles of the silica particles have dimension smaller than 16 microns.
5. The method (500) as claimed in claim 1, wherein the one or more solvents lie
in a range of 10% to 30% with respect to the silica particles, wherein the one
or more solvents are one of, water-based solvents, alcohol-based solvents, and
keto-based solvents.
6. The method (500) as claimed in claim 1, wherein the one or more binders lie
in a range of 0.01% to 5% with respect to the silica particles, wherein each
binder of the one or more binders is one of, a polypropylene carbonate, a
polyvinyl alcohol, a polystyrene, a camphor, a gelatin-based agar, and a
stabilizing agent such as dispersant, polymerizing initiator, and plasticizer.
7. The method (500) as claimed in claim 1, wherein the silica slurry (102)
comprises the silica particles that lie in a range of 40% to 80%, the one or
more binders that lie in a range of 1% to 3%, and the one or more solvents that
lie in a range of 17% to 59%.
8. The method (500) as claimed in claim 1, wherein a diameter of the soot
preform (130) is varied in a range of 35 mm to 350 mm with a deviation of +1
mm.
9. The method (500) as claimed in claim 1, comprising mixing, by way of the
one or more screws (108), the silica slurry (102).
10. The method (500) as claimed in claim 1, comprising converting, by way of the
extrusion apparatus (100, 200) the silica slurry (102) into a semi-solid silica
slurry.
11. An extrusion apparatus (100, 200) to manufacture a soot preform (130), the
extrusion apparatus (100, 200) comprising:
a feed-hopper (104) adapted to feed silica slurry (102);
a barrel (106) that is disposed beneath the feed-hopper (104) and adapted
to receive the silica slurry (102), wherein the silica slurry (102) is pushed
within the barrel (106);
a die header (114) to extrude the silica slurry (102) such that the silica
slurry (102) is cladded on a core rod (128) to form the soot preform (130),
wherein the die header (114) comprises an iris frame (116); and
the iris frame (116) comprising:
a plurality of vanes (302) such that each vane of the plurality of vanes
(302) is adapted to move in a radial direction of the iris frame (116),
wherein upon movement of each vane of the plurality of vanes (302), a
central orifice (306) is created that exhibits a variable diameter, wherein
variation in the diameter of the central orifice (306) controls a diameter of
the soot preform (130).
12. The extrusion apparatus (100, 200) of claim 10, comprising one or more
screws (108) that are disposed within the barrel (106) such that the one or
more screws (108) are adapted to mix the silica slurry and push the silica
slurry towards the iris frame (116).
13. The extrusion apparatus (100, 200) of claim 10, comprising a drying furnace
(118) that is disposed beneath the iris frame (116) and adapted to eliminate physisorbed moisture present in the soot preform (130) to produce a dried soot
preform (132); and
a debinding furnace (122) that is coupled to the drying furnace (118) and
adapted to eliminate one or more stabilized binders and other one or more
additives from the dried soot preform (132) to produce a green body (136),
wherein a glass preform (138) is obtained from the green body (136) such that
an optical fiber (142) is drawn from the glass preform (138).