Title of Invention

A PRODUCTION METHOD FOR A POROUS PREFORM

Abstract A method for producing a porous preform comprising measuring the surface temperature distribution at the end of the core soot preform, and (1) maintaining the surface temperature Tc at the center point on the end of the core soot preform in the range of 500 to 1000°C, and preferably in the range of 600 to 950°C, and maintaining the difference Tm-Tc between the maximum surface temperature Tm at the end of the core soot preform and the surface temperature Tc at the center point on the end of the core soot preform in the range of 5 to 45°C, and/or (2) maintaining the ratio R of the area in which the surface temperature at the end of the core soot preform is higher than the surface temperature Tc at the center point on the end of the core soot preform in the range of 5 to 30%.
Full Text

BACKGROUND OF THE INVENTION
1 FIELD OF THE INVENTION
The present invention relates to an improved VAD process that enables uniform
deposition of glass microparticles, even when producing a large porous glass preform
2 DESCRIPTION OF THE RELATED ART
The production of a porous preform used to make silicate optical fiber can be
carried out by a variety of methods One well-known example from among these
methods is the VAD method In the VAD method, glass microparticles synthesized by a
core burner are deposited to the end of a vertically supported mandrel as the mandrel is
rotated, and the core soot preform that will form the optical fiber core is developed into a
rod form At the same time, glass microparticles synthesized by the cladding burner are
deposited on the periphery of the core soot preform to form the cladding soot preform that
comprises part or all of the cladding In this way, a porous preform is made The
thus-obtained porous preform is then subjected to high temperature heating, undergoing
dehydration and consolidation to form a transparent glass preform This glass
transparent preform is then drawn to produce the optical fiber
In order to synthesize glass microparticles in the core and cladding burners, raw
material gases such as silicon tetrachloride (SiCl4) and germanium tetrachloride (GeCl4),
fuel gases such as hydrogen, supporting gases such as oxygen to augment burning, and
inert gases such as argon, are supplied In addition, in order to provide the optical fiber
with a refractive index profile, a different composition of raw material gases is supplied to
the core and cladding burners respectively Namely, a dopant such as GeO2 is doped at a
specific concentration to the core portion, thereby providing the optical fiber with a
refractive index profile
In addition, in order to apply a specific refractive index profile to an optical fiber,


a dopant like GeO2 is applied to the core, and further, the surface temperature of the coie
soot preform is appropriately controlled to add a specific amount of dopant This is
because, depending on the dopant employed, the doping efficiency, 1 e , the dopant
incorporated into the core soot preform, can vary greatly according to the surface
temperature of the core soot preform
Therefore, for example, radiation thermometers are placed around the core soot
preform and the core soot preform surface temperature distribution is measured Based
on these measured values, heating conditions such as the amount of fuel gas supplied to
the core burner and the relative positioning of the core burner and the core soot preform,
and the surface temperature of the core soot preform is controlled, so that the dopant is
incorporated at the desired concentration distribution
In addition, to facilitate measurement, the temperature is generally measured by
placing the radiation thermometers around the lateral direction of the core soot preform
For example, it is disclosed that there is an appropriate core soot preform surface
temperature range when doping GeO2 in the VAD method, in The Transaction of the
Institute of Electronics and Communication Engineers, Vol J65-C, No 4, p 292-299,
April, 1982
However, there has been a trend in recent years toward increasing the dimensions
of the porous preform so that optical fiber production costs can be reduced On the other
hand, as the dimensions of the porous preform increase, the outer diameter of the core soot
preform increases As a result, whereas previously the temperature distribution at the
ends of the core soot preform had been roughly constant when depositing the glass
microparticles, variations in temperature that are not negligible arise around the core soot
preform ends due to the larger diameter of the core soot preform
The areas at the core soot preform ends are the most center-positioned regions in
the refractive index profile that forms the optical fiber In order to obtain the desired
characteristics, it is necessary to control the temperature of the surface where the core soot
preform is deposited in this area especially However, when the temperature variations
in this area become large in the core soot preform, this temperature distribution cannot be


suitably controlled, so that the concentration of the dopant is not uniform As a result,
there is increased variation in the optical fiber characteristics, so that an optical fiber with
stable characteristics cannot be produced When the temperature variation in this area
becomes large, the adhesion and deposition of the glass microparticles becomes
non-uniform along the radial direction, generating a rugged surface in the core soot
preform (referred to as "rugged soot preform" in this specification) As a result, it is not
possible to continue producing the porous preform
BRIEF SUMMARY OF THE INVENTION
The present invention was conceived in view of the above-described
circumstances and has as its objective the provision of a method for producing a porous
preform in which a dopant can be stably doped to the core soot preform and rugged soot
preform can be prevented
The aforementioned problems are resolved by a method for producing a porous
preform in which the core soot preform is formed by depositing glass microparticles,
synthesized by flame hydrolysis or thermal oxidation of raw material gases expelled from
the core burner, onto the end of the mandrel, while at the same time forming the cladding
soot preform by depositing glass microparticles, synthesized by flame hydrolysis or
thermal oxidation of raw material gases expelled from the cladding burner, around the
core soot preform, wherein the surface temperature distribution at the end of the core soot
preform is measured and the heating conditions by the core burner arc set so that the
temperature Tc at the center point of the end of the core soot preform is in the range of
500 to 1000°C, and more preferably in the range of 600 to 950°C, and that the difference
Tm-Tc between the maximum surface temperature Tm at the core soot preform end and
the surface temperature Tc at the center of the core soot preform end is in the range of 5 to
45°C
The aforementioned problems are also resolved by a method for producing a
porous preform in which the core soot preform is formed by depositing glass
microparticles, synthesized by flame hydrolysis or thermal oxidation of raw mateiial gases


expelled from the core burner, onto the end of the mandrel, while at the same time forming
the cladding soot preform by depositing glass microparticles, synthesized by flame
hydrolysis or thermal oxidation of raw matenal gases expelled from the cladding burner,
around the core soot preform. in the area at said core soot preform end where the
angle formed by a line extending vertically from the soot preform surface and a line
extending in the normal line direction is 55° or less, the proportion R of the area in which
the surface temperature is higher than the surface temperature Tc at the center point of
said core soot preform end is maintained in the range of 5 to 30%
In this type of porous preform production method, it is desirable to control the
heating conditions in the core burner so that the surface temperature at the end of the core
soot preform is in the above-described range
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic structural view showing an example of the manufacturing
device employed to execute the method of the present invention for producing a porous
preform
Figure 2 is a cross-sectional diagram for explaining the radiating angle
Figure 3 is a view showing one example of the surface temperature distribution at
the end of the core soot preform
Figure 4 is a partial schematic view showing an example of the manufacturing
device employed to execute the method of the present invention for producing a porous
preform as seen from below
Figure 5 is a lateral view for explaining the method for determining the end of the
core soot preform
Figure 6 is a graph showing an example of the relationship between Tc and A
variation
Figure 7 is a graph showing an example of the relationship between Tm-Tc and A
variation
Figure 8 is a graph showing an example of the relationship between R and A


variation
PREFERRED EMBODIMENTS OF THE INVENTION
The present invention will now be explained in greater detail based on preferred
embodiments thereof Figure 1 shows an example of a manufacturing device for
executing the porous preform production method of the present invention
In Figure 1, reference numeral 1 indicates a mandrel The Mandrel 1 hangs
vertically inside a chamber 2, and can be rotated and moved up and down by a driving
means (not shown in the figures)
A core burner 3 and a cladding burner 4 are disposed inside the chamber 2
Only one cladding burner 4 is shown in Figure 1, however, it is acceptable to provide a
plurality of these as well The core burner 3 and the cladding burner 4 are designed to
synthesize glass microparticles from fuel gases such as hydrogen and supporting gases
like oxygen and material gases such as SiCl4 and GeCl4 that are supplied from a gas
supply source (not shown in the figures)
The glass microparticles synthesized by the core burner 3 are deposited to the end
of the mandrel 1 that is hanging vertically downward, forming a the core soot preform 5a
The glass microparticles that are synthesized by the cladding burner 4 are deposited
around the outer periphery of the core soot preform 5a to form a cladding soot preform 5c
The soot preform 5 consisting of the core soot preform 5a and the cladding soot preform
5c develops in the axial direction to ultimately form the porous preform
The flow of fuel and raw material gases supplied to the core burner 3 can be
adjusted using a flow adjusting device (not shown in the figures) The core burner 3 can
move in a horizontal or vertical direction through a moving means (not shown in the
figures)
First and second radiation thermometers 6a and 6b are provided to the side of and
directly below the core soot preform 5a, respectively First and second radiation
thermometers 6a and 6b are connected to an image processing data recording device 7
The heating conditions for the core burner 3 can be adjusted based on the surface


temperature distribution at the end 5b and the side surface of the core soot preform 5a that
is measured by the first and the second radiation thermometers 6a and 6b
In these preferred embodiments, the surface temperatuie distribution at the end 5b
of the core soot preform 5a is measured using the manufacturing device shown in Figure 1
and the heating conditions that the core soot preform 5a is subjected to by the core burner
3 are determined based on these measured values
The reason for providing the second radiation thermometer 6b vertically below
the core soot preform 5a is as follows
As discussed above, as the outer diameter of the core soot preform 5a increases,
temperature variations that cannot be ignored begin to occur at the surface of the core soot
preform end 5b However, for the reasons below, it is not possible to ascertain this
temperature variation at the core soot preform end 5b using just the first radiation
thermometer 6a
It is known that in general, the emissivity at the surface of an object depends on
the direction of radiation In other words, as shown in Figure 2, for infrared radiation
radiated from the surface of an object M, when the radiating angle ϕ is defined as the
angle formed by the direction of the radiation and a line normal to the surface of the object
M, then emissivity is roughly constant when ϕ is 55° or less in the case of a porous glass
preform However, when the radiating angle ϕ exceeds 55°, emissivity decreases
remarkably, so that it is not possible to obtain an accurate measurement of temperature at
radiation thermometer 6 (6a and 6b)
Accordingly, in the case where the surface temperature at the end 5 b of the core
soot preform 5a is measured by placing the first radiation thermometer 6a only at the side
of the core soot preform 5 a as in the conventional art, the measurement of the surface
temperature distribution at the end 5b of the core soot preform 5a becomes less precise
since the radiating angle ϕ is large with respect to the first radiation thermometer 6a As
a result, heating conditions are not accurately controlled To solve this problem, the
second radiation thermometer 6b is provided vertically below soot preform 5
In order to determine the extent to which the positions of first and second

ladiation thermometers 6a and 6b affect the measurement of the surface temperature at the
end 5b of the core soot preform 5a, the present inventors measured the surface temperature
distribution at the end 5b of the core soot preform 5a using the first and the second
radiation thermometers 6a and 6b m the manufacturing device shown in Figure 1 As a
result, an approximately 200°C or greater difference was discovered between the
measured value at the first radiation thermometer 6a positioned at the side of the core soot
preform 5a and second radiation thermometer 6b positioned vertically below the core soot
preform 5a
Accordingly, it was considered that the surface temperature distribution at the end
5b of the core soot preform 5a could be accurately measured by placing the second
radiation thermometer 6b vertically below the core soot preform 5 a
An example of the method for adjusting the heating conditions by the core burner
3 based on the measured values of the surface temperature distribution will now be
explained
Figure 3 is an example of the surface temperature distribution at the end 5b of the
core soot preform 5a that was measured using second radiation thermometer 6b In this
example, the center point c on the end 5 b of the core soot preform 5 a shown in Figure 1
corresponds to the center of the surface temperature distribution In the example shown
in Figure 2, the temperature at the position m where the temperature increases, is denoted
as Tm As the distance from this point increases, the surface temperature drops, so that
an isothermal line is described that is centered on m
When adjusting the heating conditions by the core burner 3 based on the surface
temperature distribution at the end 5b of the core soot preform 5a, a method may be
proposed which satisfies conditions such as
(1) the surface temperature Tc at the center point c on the end 5b of the core soot
preform 5a is in the range of 500 to 1000°C, and preferably in the range of 600 to 950°C,
and the difference Tm-Tc between the maximum surface temperature Tm at the end 5b of
the core soot preform 5a and the surface temperature Tc at the center point c on the end 5b
of the core soot preform 5a is m the range of 5 to 45°C, and


(2) the ratio R of the area in which the surface temperature at the end 5b of the core
soot pieform 5a is higher than the surface temperature Tc at the center point c on the end
5b of the core soot preform 5a is in the range of 5 to 30%
By using any of these conditions, a dopant such as GeO2 can be stably doped
In particular, it is preferable to adjust the heating conditions so as to satisfy all these
conditions
When these conditions arc not satisfied, the dopant cannot be stably doped. Accordingly,
this is not desirable as there is a large amount of variation along the longitudinal direction
of the refractive index profile of the porous preform, and rugged soot preform occurs
As described above, the amount of a dopant such as GeO2 that is doped will vary
according to the surface temperature of the core soot preform 5a in the doped area In
particular, when the surface temperature exceeds 1000°C, the vapor pressure of the GeO2
increases, so that the amount doped to the core soot preform 5a becomes extiemely
unstable Further, the bulk density of the core soot preform 5a increases, so that the
subsequent dehydrating process tends to be insufficient
In the area at the end 5b of the core soot preform 5a, the center c of the end 5b of
the core soot preform 5a is the same as the center of a rotation of the mandrel 1 When
the center c of the core soot preform end and position m, where the temperature is
maximal, coincide, positional variations arising from rotation do not occur Thus, local
concentration of the dopant can readily increase Under these circumstances, the
concentration of the dopant can vary dramatically in the area around the center of the core
soot preform end 5b For this reason, even slight variations in pioduction conditions
caused by a disturbance of some sort can result in rapid changes in the concentration of the
dopant
On the other hand, the amount of glass microparticles deposited on the core soot
preform 5a also depends on the surface temperatuie of the core soot preform 5a When
the tempeiature is high, the space surrounding the glass microparticles is small, while
when the temperature is low, the space around the glass microparticles is larger In other


words, the bulk density and the volume of the glass microparticles deposited varies
depending on temperature variations For this reason, when the temperature gradient
becomes too large in the radial direction of rotation at the end 5b of the core soot preform
5a, the volume of adhered glass microparticles becomes non-uniform in the radial
direction, resulting in rugged soot preform
Examples of the heating conditions in the core burner 3 that are applied to the
core soot preform 5a include the flow volume of fuel gases such as hydrogen and
supporting gases such as oxygen, and the relative positioning of the core burner 3 and the
end 5 b of the core soot preform 5 a
If heating conditions such as these are preset using test runs prior to producing the actual
product, then these conditions can be adjusted prior to manufacture of the product so that
the porous preform can be produced with these conditions held constant during production
As a result, these conditions do not have to be controlled or varied during production, so
that production is facilitated
It is also acceptable to employ a suitable control device to control the heating
conditions by suitably varying them during operation
In addition, it is also acceptable to first produce a porous preform by holding the heating
conditions constant, and then, when the surface temperature conditions at the core soot
preform 5 a seem likely to exceed the above-prescribed limits, to then begin controlling the
heating conditions That is, under these circumstances, the heating conditions can be
suitably varied so as to maintain the above-defined range, so that glass microparticles can
be continuously deposited
The following method is available as a method for adjusting the relative
positioning of the end 5 b of the core soot preform 5 a and the core burner 4 For example,
Figure 4 shows the manufacturing device in Figure 1 as seen from below As shown in
Figuie 4, the heating conditions at the core burner 3 can be varied by moving the core
burner 3 in the horizontal direction In addition, by raising or lowering the mandrel 1,
the heating conditions at the core burner 3 can be adjusted
In addition, the core burner 3 can be moved perpendicularly up or down, or can be


moved toward or away from the core soot preform 5 a
The wavelength measured at the first and the second radiation thermometers 6a
and 6b will depend on the type of radiation thermometer employed Accordingly, there
are no particular restrictions applied to the wavelength Provided that the surface
temperature distribution at the core soot preform 5a can be measured with good accuracy,
then the measurement can be conducted using the wavelengths employed in the usual
radiation thermometer For example, a 3 0 to 5 3 urn band may be adopted in order to
eliminate absorption by the moisture vapor in the air or flame emitted from the core burner
j>
In this embodiment, the end 5b of the core soot preform 5a is the area on the core
soot preform 5 a in which the radiation angel ϕ with respect to the second radiation
thermometer 6b positioned perpendicularly below the core soot preform 5a is 55° or less
As a result of this design, the surface temperature distribution at the end 5b of the core
soot preform 5a can be measured by the second radiation thermometer 6b, thereby further
simplifying the device design
In this case, as shown in Figure 5, since second radiation thermometer 6b is
located perpendicularly below the core soot preform 5a, radiating angle ϕ at an optional
point P on the surface of the core soot preform 5a is equal to angle 6 formed between the
tangential and horizontal planes at point P Accordingly, when determining the end 5b of
the core soot preform 5a, the contour of the end 5b of the core soot preform 5a is
measured using a CCD camera from the side of the core soot preform 5a, and the end 5b
can be determined using image processing of the measured contour
As in the case of the conventional art, a porous preform formed according to this
embodiment can be formed into an optical fiber by drawing after heating and
transparent-vitrifying
Next, the present invention will be explained using examples A porous preform
was produced using the manufacturing device shown in Figure 1
The wavelength measured by the first and the second radiation thermometers 6a
and 6b, was in the range of 3 0 to 5 3 µm A multi-pipe bumei having supply ports for


hydrogen, oxygen and argon provided in stratification around the supply ports for the raw
material gases were employed as the core burner 3 The flow rates of oxygen gas, SiCl4,
GeCl4, and argon were 21 liters/minute, 1 8 liters/minute, 0 12 hters/minute, and 8 2
liters/minute, respectively
The flow rate of hydrogen gas supplied to the core burner 3 was varied in the
range of 19 to 37 liters/minute Heating conditions of the soot preform end 5b were
varied by moving the core burner 3 and the core soot preform 5a relative to one another
By varying the heating conditions of the core burner 3, the relative position
coordinates of point m with respect to point c in the surface temperature distribution
shown in Figure 3 was varied in the range of 0 to 1 8 mm for the X coordinate and -2 2 to
-0 2 mm for the Y coordinate
Glass microparticles were deposited under these respective conditions, to produce
a plurality of porous prefomis with a diameter of 200 mm and a length of 700 mm Then,
the porous preforms were heated to form the transparent glass preforms In order to
investigate the variation along the longitudinal direction of the specific refractive index
difference A for these transparent glass preforms, 12 measurement points were set at equal
intervals along the longitudinal direction using a preform analyzer, the specific refractive
index difference A was measured and the variations in these measurements were
calculated
Figure 6 is a graph showing an example of the relationship between A variation
and Tc when Tc is varied
Figure 7 is a graph showing an example of the relationship between Tm-Tc and A
variation when Tm-Tc is varied
Figure 8 is a graph showing an example of the relationship between R and A
variation when R is vaned
In Figures 6 to 8, the mark [♦] indicates cases where a porous preform could be
produced in which no rugged soot preform occurred, and indicates the value of the A
variation shown on the vertical axis The mark [•] indicates cases where rugged soot
preform occurred When rugged soot preform occurred, production of the porous


pieform was halted, and the A variation of the transparent glass preform was not
measuied
As is clear from these results, when 500°C ≤ Tc ≤ 1000°C, 5°C ≤ Tm-Tc ≤ 45°C,
and 5% ≤ R ≤ 30%, ∆ variation could be held to a small value of 0 05% or less and it was
possible to prevent rugged soot preform from occurring
In addition, glass microparticle deposition was carried out from the beginning after
setting the heatmg conditions at the core soot preform end so that 500°C ≤ Tc ≤ 1000°C,
5°C s Tm-Tc ≤ 45°C, and 5% ≤ R ≤ 30%, to fonn a porous preform having a diameter of
200 mm and a length of 700 mm As a result, a porous preform could be produced in
which the A variation in the specific refractive index difference over the entire length was
small, and the occurrence of rugged soot preform could be prevented
Of course when there occurs a concern that the values of Tc, Tm-Tc, and R
during deposition of the glass microparticals may have deviated outside the ranges of
500°C ≤ Tc ≤ 1000°C, 5°C ≤ Tm-Tc ≤ 45°C, and 5% ≤ R ≤ 30%, it is acceptable to
continue to deposit the glass microparticles by controlling and suitably varying the heatmg
conditions at the core soot preform end so as to maintain the above-prescribed range It
goes without saying that in this case as well, excellent results can be obtained
As explained above, as a result of the production method of the present invention
for a porous preform, it is possible to control variations in characteristics along the length
of the fiber minimum, so that a superior optical fiber can be produced In addition,
rugged soot preform can be prevented and productivity can be improved


WE CLAIM :
1. A production method for a porous preform in which a core soot preform is formed by
depositing glass microparticles, synthesized by flame hydrolysis or therml oxidation of
raw material gases expelled from a core burner, onto the end of a mandrel, while at the
same time forming a cladding soot preform by depositing glass microparticles,
synthesized by flame hydrolysis or thermal oxidation of raw material gases expelled from
a cladding burner, around said core soot preiorm, wherein
the surface temperature Tc at the center point of the end of said core soot preform
is in the range of 500 to 1000°C, and
the difference Tm-Tc between the maximum the surface temperature Tm at said
core soot preform end and the surface temperature Tc at the center of said core soot
preform end is in the range of 5 to 45°C.
2. A production method for a porous preform in which a core soot preform is formed by
depositing glass microparticles, synthesized by flame hydrolysis or thermal oxidation of
raw material gases expelled from a core burner, onto the end of a mandrel, while at the
same time forming a cladding soot preform by depositing glass microparticles,
synthesized by flame hydrolysis or thermal oxidation of raw material gases expelled from
a cladding burner, around said core soot preform, wherein,
in the area at said core soot preform end where the angle formed by a line
extending vertically from the soot preform surface and a line extending in the normal line
direction is 55° or less, the proportion R of the area in which the surface temperature is
hight than the surface temperature Tc at the center point of said core soot preform end is
maintained in the range of 5 to 30%.
3. A production method for a porous preform according to claim 1 or 2, wherein heating
conditions of the soot preform end by the core burner are controlled.

4. A process for producing a porous glass preform, substantially as herein
described, particularly with reference to the accompanying drawing.




PRODUCTION PROCESS FOR POROUS GLASS PREFORM
ABSTRACT


A method for producing a porous preform comprising measuring the surface
temperature distribution at the end of the core soot preform, and (1) maintaining the
surface temperature Tc at the center point on the end of the core soot preform in the range
of 500 to 1000°C, and preferably in the range of 600 to 950°C, and maintaining the
difference Tm-Tc between the maximum surface temperature Tm at the end of the core
soot preform and the surface temperature Tc at the center point on the end of the core soot
preform in the range of 5 to 45°C, and/or (2) maintaining the ratio R of the area in which
the surface temperature at the end of the core soot preform is higher than the surface
temperature Tc at the center point on the end of the core soot preform in the range of 5 to
30%.

Documents:

701-CAL-2002-(22-11-2012)-CORRESPONDENCE.pdf

701-CAL-2002-ABSTRACT.pdf

701-CAL-2002-ASSIGNMENT.pdf

701-CAL-2002-CLAIMS.pdf

701-CAL-2002-CORRESPONDENCE.pdf

701-CAL-2002-CORRESPONDENCE1.1.pdf

701-CAL-2002-DESCRIPTION (COMPLETE).pdf

701-CAL-2002-EXAMINATION REPORT.pdf

701-CAL-2002-FORM 1.pdf

701-CAL-2002-FORM 18.pdf

701-CAL-2002-FORM 2.pdf

701-CAL-2002-FORM 3.pdf

701-CAL-2002-FORM 5.pdf

701-CAL-2002-GPA.pdf

701-CAL-2002-GRANTED-ABSTRACT.pdf

701-CAL-2002-GRANTED-CLAIMS.pdf

701-CAL-2002-GRANTED-DESCRIPTION (COMPLETE).pdf

701-CAL-2002-GRANTED-FORM 1.pdf

701-CAL-2002-GRANTED-FORM 2.pdf

701-CAL-2002-GRANTED-FORM 3.pdf

701-CAL-2002-GRANTED-FORM 5.pdf

701-CAL-2002-GRANTED-LETTER PATENT.pdf

701-CAL-2002-GRANTED-SPECIFICATION-COMPLETE.pdf

701-CAL-2002-OTHERS.pdf

701-CAL-2002-PETITION UNDER RULE 137.pdf

701-CAL-2002-PRIORITY DOCUMENT.pdf

701-CAL-2002-REPLY TO EXAMINATION REPORT.pdf

701-CAL-2002-SPECIFICATION.pdf

701-CAL-2002-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf


Patent Number 255614
Indian Patent Application Number 701/CAL/2002
PG Journal Number 11/2013
Publication Date 15-Mar-2013
Grant Date 08-Mar-2013
Date of Filing 16-Dec-2002
Name of Patentee FUJIKURA LTD
Applicant Address 5-1, KIBA 1-CHOME, KOHTOH-KU, TOKYO, JAPAN
Inventors:
# Inventor's Name Inventor's Address
1 GOTOH TAKAKAZU C/O FUJIKURA LTD, SAKURA WORKS 1440, MUTSUZAKI, SAKURA-SHI CHIBA-KEN, JAPAN
2 HORIKOSHI MASAHIRO C/O FUJIKURA LTD, SAKURA WORKS 1440, MUTSUZAKI, SAKURA-SHI CHIBA-KEN, JAPAN
PCT International Classification Number C03B 37/018
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2002-068997 2002-03-13 Japan
2 2002-268787 2002-09-13 Japan