U.S. patent application number 09/233816 was filed with the patent office on 2002-01-17 for fiber optic draw furnace featuring a fiber optic preform heating and fiber drawing programmable logic controller.
Invention is credited to UHM, DANIEL D..
Application Number | 20020005052 09/233816 |
Document ID | / |
Family ID | 22878808 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020005052 |
Kind Code |
A1 |
UHM, DANIEL D. |
January 17, 2002 |
FIBER OPTIC DRAW FURNACE FEATURING A FIBER OPTIC PREFORM HEATING
AND FIBER DRAWING PROGRAMMABLE LOGIC CONTROLLER
Abstract
The present invention provides a fiber optic draw furnace having
a fiber optic heating and draw control system that controls the
heating of a fiber optic preform which is partially melted by a
furnace and the drawing of an optical fiber from the fiber optic
preform by a fiber drawing device. The fiber optic heating and draw
control system features a fiber optic heating and drawing device
controller that responds to a furnace power consumption control
signal from a fiber optic preform heating device in the furnace,
for providing a furnace heating control signal to the fiber optic
preform heating device in the furnace and a fiber tension draw
control signal to the fiber drawing device to maintain a desired
fiber draw tension on the optical fiber. In one embodiment, the
fiber optic heating and drawing device controller is a programmable
logic controller. One advantage of the present invention is that it
eliminates the need for an optical pyrometer port, which results in
a symmetrical temperature profile around the circumference of the
preform and also helps eliminate induced stresses that can cause
defects in an optical fiber.
Inventors: |
UHM, DANIEL D.; (CORNELIUS,
NC) |
Correspondence
Address: |
WARE FRESSOLA VAN DER SLUYS &
ADOLPHSON, LLP
BRADFORD GREEN BUILDING 5
755 MAIN STREET, P O BOX 224
MONROE
CT
06468
US
|
Family ID: |
22878808 |
Appl. No.: |
09/233816 |
Filed: |
January 20, 1999 |
Current U.S.
Class: |
65/486 ;
65/488 |
Current CPC
Class: |
C03B 37/0253 20130101;
C03B 2205/72 20130101; C03B 2205/40 20130101 |
Class at
Publication: |
65/486 ;
65/488 |
International
Class: |
C03B 037/07 |
Claims
What is claimed is:
1. A furnace (10) for heating a fiber optic preform (12) inside a
furnace heating chamber (14) and drawing an optical fiber (F),
comprising: fiber optic preform heating means (16), responsive to a
fiber optic preform heating control signal, for heating the fiber
optic preform (12), and for further providing a fiber optic preform
heating feedback signal; fiber tension sensing means (18),
responsive to a tension of the optical fiber (F), for providing a
sensed fiber tension signal; fiber drawing means (20), responsive
to a fiber drawing control signal, for drawing the optical fiber
(F); and fiber optic preform heating and fiber drawing controller
means (22), responsive to the fiber optic preform heating feedback
signal, and further responsive to the sensed fiber tension signal,
for providing the fiber optic preform heating control signal to the
fiber optic preform heating means (16) to control the heating of
the fiber optic preform (12), and for providing the fiber drawing
control signal to the fiber drawing means (20) to control the
drawing of the optical fiber (F); whereby the fiber optic preform
heating and fiber drawing controller means (22) controls fiber draw
tension of the fiber optic preform (12) independent of the
temperature of the furnace (10).
2. A furnace (10) according to claim 1, wherein the fiber optic
preform heating and fiber drawing controller means (22) is a
programmable logic controller.
3. A furnace (10) according to claim 1, wherein the fiber tension
sensing means (18) is a non-contact fiber tension device that
responds to the tension of the optical fiber (F), for providing a
non-contact sensed fiber tension signal to the fiber optic preform
heating and fiber drawing controller means (22).
4. A furnace (10) according to claim 1, wherein the fiber optic
preform heating feedback signal from the fiber optic preform
heating means (16) is a furnace power consumption feedback signal
that feeds information about the furnace power consumption of the
furnace (10) back to the fiber optic preform heating and fiber
drawing controller means (22).
5. A furnace (10) according to claim 4, wherein the furnace power
consumption feedback signal includes information about a sensed
measurement of voltage and amperage of electrical energy used to
heat the furnace (10).
6. A furnace (10) for heating a fiber optic preform (12) inside a
furnace heating chamber (14) and drawing an optical fiber (F),
having fiber optic preform heating means (16) for heating the fiber
optic preform (12), having non-contact fiber tension sensing means
(18) for providing a non-contact sensed fiber tension signal, and
also having a fiber drawing means (20) for drawing the optical
fiber (F), characterized in that the furnace (10) comprises a fiber
optic preform heating and fiber drawing programmable logic
controller (22) that responds to a fiber optic preform heating
furnace power consumption feedback signal from the fiber optic
preform heating means (16), and further responds to a sensed fiber
tension signal from the non-contact fiber tension sensing means
(18), for providing a fiber optic preform heating control signal to
the fiber optic preform heating means (16) to control the heating
of the fiber optic preform (12), and for providing a fiber drawing
control signal to the fiber drawing means (20) to control the
drawing of the optical fiber (F); whereby the fiber optic preform
heating and fiber drawing controller means (22) controls fiber draw
tension of the fiber optic preform (12) without the need for
sensing the temperature of the furnace (10).
7. A furnace (10) according to claim 6, wherein the furnace power
consumption feedback signal includes information about a sensed
measurement of voltage and amperage of electrical energy used to
heat the furnace (10).
8. A fiber optic heating and draw control system for a furnace (10)
for controlling the continuous heating of a fiber optic preform
(12) that is partially melted by a furnace and the continuous
drawing of an optical fiber from the fiber optic preform (12) by a
fiber drawing device (20), characterized in that the fiber optic
heating and draw control system comprises a fiber optic heating and
drawing device controller (22) that responds to a furnace power
consumption control signal (24) from a fiber optic preform heating
device (16) in the furnace (10), for providing a furnace heating
control signal (26) to the fiber optic preform heating device (16)
in the furnace (10) and a fiber tension draw control signal (30) to
the fiber drawing device (20) to maintain a desired fiber draw
tension on the optical fiber (F).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a fiber optical fiber draw
furnace for drawing optical fiber from a preform.
[0003] 2. Description of Related Art
[0004] Known fiber optic draw furnaces control the draw of the
optical fiber from the preform by monitoring various parameters,
including among others fiber tension, fiber diameter, fiber
velocity and furnace temperature. For example, see U.S. Pat. Nos.
5,079,433; 5,228,893 and 5,316,562.
[0005] Existing graphite resistance fiber optic draw furnace
control methods utilize temperature feedback based on optical
measurement using a pyrometer to control furnace temperature. The
pyrometer requires a sight "port" that is essentially a cylindrical
hole through the insulation material.
[0006] The use of the sight port results in several disadvantages
including among other things uneven heating of the preform
(temperature profile not uniform due to heat sink created by
pyrometer port), accelerated graphite erosion (heating element,
furnace insulation, etc.), and improper alignment and calibration
of the pyrometer for proper furnace control feedback. Induced
stresses created by a non-uniform thermal profile can result in
optical and physical defects in the drawn fiber such as elevated
attenuation loss, fiber curl, etc.
[0007] Another disadvantage of using a site port is that it will
darken over time due to the frequent condensation of material on
the transparent wall which blocks the light flux to be measured, as
described in U.S. Pat. No. 4,317,666, column 1, lines 36-43.
[0008] Yet another disadvantage is that induced stresses are
created by the non-uniform thermal profile of the preform which
result in optical and physical defects in the drawn fiber such as
elevated attenuation loss and fiber curl.
SUMMARY OF THE INVENTION
[0009] The present invention provides a fiber optic draw furnace
having a fiber optic heating and draw control system that controls
the heating of a fiber optic preform which is partially melted by a
furnace and the drawing of an optical fiber from the fiber optic
preform by a fiber drawing device.
[0010] The fiber optic heating and draw control system features a
fiber optic heating and drawing device controller that responds to
a furnace power consumption control signal from a fiber optic
preform heating device in the furnace, for providing a furnace
heating control signal to the fiber optic preform heating device in
the furnace and a fiber tension draw control signal to the fiber
drawing device to maintain a desired fiber draw tension on the
optical fiber.
[0011] In one embodiment, the fiber optic heating and drawing
device controller is a programmable logic controller.
[0012] The fiber optic preform heating feedback signal from the
fiber optic preform heating device is a furnace power consumption
feedback signal that feeds information about the power consumption
of the furnace back to the fiber optic preform heating and fiber
drawing controller.
[0013] The furnace power consumption feedback signal includes
information about a sensed measurement of voltage and amperage of
electrical energy used to heat the furnace.
[0014] One advantage of the present invention is that it eliminates
the need for an optical pyrometer port, which results in a
symmetrical temperature profile around the circumference of the
preform and also helps eliminate induced stresses that can cause
defects in an optical fiber.
[0015] Another advantage is that the overall furnace life is
increased, reducing operating costs, because graphite erosion is
reduced. Reducing graphite erosion results in a cleaner furnace
(dramatically reduces graphite dust and particulate generation) and
increased furnace stability and longevity. This results in a
cleaner furnace having significantly less graphite dust and
particulate generation while increasing furnace stability and
longevity. A clean furnace is essential for the manufacturing of
high strength optical fiber.
[0016] The present invention may be more clearly understood from
the following description of a specific and preferred embodiment
read in conjunction with the accompanying detailed drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0017] FIG. 1 is a schematic view of a fiber optic draw furnace
that is the subject matter of the present invention.
DETAILED DESCRIPTION OF THE BEST MODE OF THE INVENTION
[0018] FIG. 1 shows a fiber optic draw furnace generally indicated
as 10 for drawing an optical fiber F from a molten preform 12. The
fiber optic draw furnace 10 includes a furnace heating chamber 14,
a fiber optic preform heating device 16, a fiber tension sensing
means 18, a fiber drawing means 20, and a fiber optic preform
heating and fiber drawing controller means 22. In one embodiment,
the fiber optic draw furnace 10 may be an optical graphite furnace,
although the scope of the invention is not intended to be limited
to any particular type of furnace.
[0019] The furnace heating chamber 14 houses the fiber optic
preform heating device 16, which continuously heats and partially
melts the molten preform 12. The fiber drawing means 20 draws the
optical fiber F from the molten preform 12 as a melting glass.
[0020] In operation, the fiber optic preform heating means 16
responds to a fiber optic preform heating control signal along line
22a from the fiber optic preform heating and fiber drawing
controller means 22, for heating the molten preform 12, and
provides a fiber optic preform heating feedback signal along line
16a back to the fiber optic preform heating and fiber drawing
controller means 22. The preform heating device 16 is known in the
art, and the scope of the invention is not intended to be limited
to any particular type thereof. The preform heating device 16 may
be of the graphite resistance type, although other forms of heating
devices are clearly intended to be within the scope of the present
invention.
[0021] As fiber optic preform 12 begins melting, the optical fiber
F is formed. The optical fiber F passes a fiber tension sensing
means 18, which senses a fiber tension. The fiber tension sensing
means 18 responds to a tension sensed in the optical fiber F, for
providing a sensed fiber tension signal along line 18a to the fiber
optic preform heating and fiber drawing controller means 22. The
fiber tension sensing means 18 is known in the art, and may include
a non-contact type. Embodiments are also envisioned in which the
fiber tension sensing means 18 is a contact type, which are also
known in the art, although the scope of the invention is not
intended to be limited to any particular way of sensing fiber
tension.
[0022] The fiber drawing means 20 responds to a fiber drawing
control signal along line 22b from the fiber optic preform heating
and fiber drawing controller means 22, for drawing the optical
fiber F. The fiber drawing means 20 is known in the art, and the
scope of the invention is not intended to be limited to any
particular type thereof. The fiber drawing means 20 is also known
in the art as a capstan. The drawing device 20 may sometimes be
downstream of other devices, such as a fiber coating applicator
(not shown), which are not a part of the present invention shown
and described herein.
[0023] The fiber optic preform heating and fiber drawing controller
means 22 responds to the fiber optic preform heating feedback
signal along line 16a from the preform heating device 16, and
further responds to the sensed fiber tension signal along line 18a
from the fiber tension sensing means 18, for providing the fiber
optic preform heating control signal along line 22a to the fiber
optic preform heating means 16 to control the heating of the fiber
optic preform 12, and also for providing the fiber drawing control
signal along line 22b to the fiber drawing means 20 to control the
drawing of the optical fiber (F). The fiber optic preform heating
and drawing controller means 22 may be a programmable logic
controller (PLC), or a microprocessor-based architecture for
running a fiber optic preform heating and drawing controller
program. In operation, the programmable logic controller 22
maintains desired draw tension by controlling the preform heating
device 16 and the draw capstan 20. The scope of the invention is
intended to cover embodiments using hardware, software or a
combination thereof.
[0024] In operation, the fiber optic preform heating feedback
signal along line 16a from the fiber optic preform heating means
(16) is a furnace power consumption feedback signal that feeds
information about the power consumption of the furnace (10) back to
the fiber optic preform heating and fiber drawing controller means
(22). The furnace power consumption feedback signal includes
information about a sensed measurement of voltage and amperage of
electrical energy used to heat the furnace (10).
[0025] In effect, the present invention uses power control instead
of temperature control to predict the melting rate of the fiber
optic preform 12. The power control relies on the principal of
power feedback using a preform heating feedback signal 24 to
control fiber optic draw tension. The power in the form of current
and voltage consumed by the fiber optic preform heating element 16
is fed back to the programmable logic controller 22 in the process
control loop. As a result, the fiber optic draw tension is
controlled without the need for sensing the furnace temperature.
The power control can also be accomplished by measuring consumption
of any type of energy used to heat the fiber optic preform 12,
whether it be electric or otherwise.
[0026] As those skilled in the art will recognize, the invention is
not necessarily limited to the specific embodiments described
herein, and the inventive concept may be implemented in additional
ways, all in accordance with the claims below.
* * * * *