JP2005263545A - Method of manufacturing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical fiber with excellent production yield. <P>SOLUTION: A drawing speed is increased from an initial drawing speed V<SB>1</SB>toward a aimed drawing speed V<SB>3</SB>in a drawing increase step (time t<SB>1</SB>-t<SB>3</SB>) between an initial drawing step (time t<SB>0</SB>-t<SB>1</SB>) and a normal drawing step (after time t<SB>3</SB>) and a furnace temperature rises from a initial furnace temperature T<SB>1</SB>toward an aimed furnace temperature T<SB>3</SB>during the increase of the drawing speed. In the drawing speed increase step, an optical fiber preform is drawn to manufacture the optical fiber by keeping the drawing tension to an aimed drawing tension A<SB>3</SB>after a prescribed time t<SB>2</SB>in the middle of increase of the drawing speed is elapsed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing an optical fiber by heating, softening and drawing an optical fiber preform in a heating furnace.

  An optical fiber used as an optical transmission line in an optical communication system is manufactured by heating, softening, and drawing an optical fiber preform in a heating furnace (see, for example, Patent Document 1 and Patent Document 2). In the initial state of drawing of the optical fiber preform, the drawing speed (initial drawing speed) that is the traveling speed of the optical fiber obtained by drawing is slow, and the furnace temperature (initial furnace temperature) that is the temperature in the heating furnace. ) Is low. Thereafter, the furnace temperature is increased from the initial furnace temperature to the target furnace temperature, and thereafter, the drawing speed is increased from the initial drawing speed to the target drawing speed. After the time when the target drawing speed and the target furnace temperature are reached, the drawing speed and the furnace temperature are maintained as they are to obtain a steady state, and the optical fiber preform is drawn.

Here, the target furnace temperature during steady drawing is set based on the target drawing speed and target drawing force during steady drawing. That is, the drawing tension applied to the optical fiber during drawing affects the characteristics of the optical fiber (for example, cutoff wavelength and mode field diameter), so that an optical fiber having desired characteristics can be manufactured. As described above, the target line tension force at the time of steady drawing is appropriately set. Then, the target furnace temperature is appropriately set so that a desired target drawing speed and target drawing tension can be obtained.
JP-A-53-43540 Japanese Patent Laid-Open No. 2-80341

  By the way, the present inventor has found that the conventional optical fiber manufacturing method has the following problems. That is, in the initial state that is the initial drawing speed and the initial furnace temperature, the drawing tension is larger than the target drawing tension. However, after raising the furnace temperature from the initial furnace temperature to the target furnace temperature, the drawing speed is increased from the initial drawing speed to the target drawing speed. While the temperature is low (near the initial drawing speed), the furnace temperature becomes high (near the target furnace temperature), and the drawing tension becomes smaller than the target drawing tension. As the drawing speed is increased from the initial drawing speed to the target drawing speed, the drawing tension gradually increases. When the target drawing speed is reached, the drawing tension is approximately equal to the target drawing tension. Become.

  Thus, before the steady state of the target drawing speed and the target furnace temperature is reached, the drawing tension does not become a stable target drawing tension, and an optical fiber having desired characteristics cannot be obtained. Since the optical fiber portion not having the desired characteristics is discarded, the conventional optical fiber manufacturing method has a poor manufacturing yield when manufacturing the optical fiber from the optical fiber preform.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical fiber manufacturing method with excellent manufacturing yield.

An optical fiber manufacturing method according to the present invention is a method of manufacturing an optical fiber by heating, softening and drawing an optical fiber preform in a heating furnace, and (1) an initial drawing speed V ₁ and an initial furnace temperature T _1. and the initial drawing step of drawing the optical fiber preform under initial linear tensile initial condition of the force a _1, to increase the drawing speed to the target line drawing rate V ₃ from (2) initial line drawing rate V ₁ together, the drawing speed was from the initial furnace temperature T ₁ during the rise increases the target furnace temperature T ₃ to a furnace temperature, tensile line to the target line tension a ₃ in the following from the middle of a predetermined time in the drawing speed increases A step of increasing the drawing speed for drawing the optical fiber preform while maintaining the force, and (3) an optical fiber under steady conditions of the target drawing speed V ₃ , the target furnace temperature T ₃ and the target drawing tension A ₃ A steady drawing step of drawing the base material.

In this optical fiber manufacturing method, when the optical fiber preform is drawn and the optical fiber is manufactured, the initial drawing step, the drawing speed increasing step, and the steady drawing step are sequentially performed with time. In the initial drawing step, an optical fiber preform is drawn under the initial conditions of an initial drawing speed V ₁ , an initial furnace temperature T _1, and an initial drawing tension A ₁ , and an optical fiber is manufactured. In the steady drawing step, the optical fiber preform is drawn under the steady conditions of the target drawing speed V ₃ , the target furnace temperature T _3, and the target drawing tension A ₃ to manufacture an optical fiber. The initial drawing the linear velocity increases steps in between steps and the steady drawing step, together with the drawing speed to the target line drawing rate V ₃ from the initial line drawing rate V ₁ is increased, during the drawing speed increases furnace temperature is raised from an initial furnace temperature T ₁ to the target furnace temperature T _3. Furthermore, in this linear velocity rise step, the subsequent than the middle of a predetermined time of the drawing speed increases, the drawing tension to the target line tension A ₃ is maintained, optical fiber optical fiber preform is drawing is produced The

In the optical fiber manufacturing method according to the present invention, the drawing speed increasing step is performed based on (a) the initial drawing speed V ₁ , the initial furnace temperature T ₁ and the initial drawing tension A _1. An intermediate drawing speed V ₂ and an intermediate furnace temperature T ₂ that can be A ₃ are set to increase the drawing speed from the initial drawing speed V ₁ to the intermediate drawing speed V _2. while raising the furnace temperature from the initial furnace temperature T ₁ to an intermediate furnace temperature T ₂ in a first line speed increase step of drawing the optical fiber preform, the drawing tension to the force a ₃ tensile (b) target line maintaining, it causes the intermediate line drawing rate V ₂ increases the target line drawing rate V ₃ until the drawing speed, increase the furnace temperature from the intermediate furnace temperature T ₂ to the target furnace temperature T ₃ during the drawing speed increases And a second linear speed increasing step for drawing the optical fiber preform.

In this case, the linear speed increasing step between the initial drawing step and the steady drawing step is divided into a first linear speed increasing step and a second linear speed increasing step. In the first drawing speed increasing step, based on the initial drawing speed V ₁ , the initial furnace temperature T ₁ and the initial drawing tension force A ₁ , the intermediate drawing speed V _{2 at which the} drawing tension can become the target drawing tension A ₃ and set intermediate furnace temperature T _2, together with the drawing speed from the initial line drawing rate V ₁ to the middle line drawing rate V ₂ is increased, an intermediate furnace temperature from the initial furnace temperature T ₁ during the drawing speed increases T _The furnace temperature rises to 2. In the subsequent second drawing speed increasing step, the drawing speed increases from the intermediate drawing speed V ₂ to the target drawing speed V ₃ while maintaining the drawing tension at the target drawing tension A ₃ , and this drawing speed. furnace temperature from the intermediate furnace temperature T ₂ to the target furnace temperature T ₃ is increased during the increase.

In the optical fiber manufacturing method according to the present invention, the drawing tension is the tension of the coated optical fiber obtained by drawing the optical fiber preform and coating the resin, and after the predetermined time of the linear velocity increasing step and the steady line in pull step, by measuring the tension of the coated optical fiber, it is preferable to control the respective drawing speed and furnace temperature while maintaining the tension obtained by the measurement target line tension a _3.

In the optical fiber manufacturing method according to the present invention, the drawing tension is the tension of the glass fiber obtained by drawing the optical fiber preform, and after the predetermined time of the drawing speed increasing step and in the steady drawing step, by measuring the tension of the glass fibers, it is also suitable for controlling the respective drawing speed and furnace temperature while maintaining the tension obtained by the measurement target line tension a _3.

When the drawing tension is the tension of the glass fiber, the target drawing tension A ₃ is preferably in the range of 6.4 N / mm ^{2 to} 24.0 N / mm ² , and at this time, the optical fiber mother The core region of the material is preferably made of pure quartz glass.

Further, when the drawing tension is the tension of the glass fiber, the force _{A 3} Tensile target line is preferred in the range of ^{32N / mm 2 ~120N / mm 2} , the 40N / mm ² ~96N / mm 2 More preferably, it is in the range. Target line drawing rate V ₃ is preferred that at 1500 m / min or more, drawing tension of the variation range when with any line drawing rate of linear speed increase step and constant drawing step is 1000 m / min or more ( = (Maximum value-minimum value) / 2) is preferably 6.4 N / mm ² or less. In these cases, it is convenient when drawing an optical fiber preform having GeO ₂ added to the core region.

  According to the present invention, an optical fiber can be manufactured with a high yield.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram of an optical fiber manufacturing apparatus 1. In this optical fiber manufacturing apparatus 1, an optical fiber preform 2 containing quartz glass as a main component is inserted into a heating furnace 12 and sent downward by a delivery device 11. Glass fiber 3 is obtained by drawing gradually from the lower end of optical fiber preform 2 heated and melted by heating furnace 12. The glass fiber 3 is coated with a resin by passing through a coating die 13 containing a resin. The glass fiber 3 is cured by being irradiated with ultraviolet rays by an ultraviolet irradiation device 14, and is again coated with a resin. The resin is coated by passing through the die 15, and the resin is cured by being irradiated with ultraviolet rays by the ultraviolet irradiation device 16. The coated optical fiber 4 obtained by coating the glass fiber 3 with the resin in this way is wound up by the winding device 19 through the turn pulley 17 and the take-up device 18.

  An outer diameter measuring device 21 and a tension measuring device 22 are arranged between the heating furnace 12 and the coating die 13. Each of the outer diameter measuring device 21 and the tension measuring device 22 is optical, and the outer diameter measuring device 21 measures the outer diameter of the glass fiber 3, and the tension measuring device 22 measures the tension of the glass fiber 3.

  An outer diameter measuring device 23 is disposed between the ultraviolet irradiation device 16 and the turn pulley 17. The outer diameter measuring device 23 is also an optical type, and the outer diameter of the coated optical fiber 4 is measured by the outer diameter measuring device 23. Further, a tension measuring device 24 is disposed in the vicinity of the turn pulley 17. The tension measuring device 24 measures the tension applied to the turn pulley 17 by the coated optical fiber 4, thereby measuring the tension of the coated optical fiber 4.

  The results measured by the outer diameter measuring device 21, the tension measuring device 22, the outer diameter measuring device 23 and the tension measuring device 24 are notified to the control unit 25. The controller 25 controls the drawing speed, the furnace temperature of the heating furnace 12, and the drawing tension. The drawing speed is adjusted by the drawing device 18. Note that the drawing speed, the furnace temperature, and the drawing tension can not be controlled independently but influence each other.

FIG. 2 is a view for explaining an optical fiber manufacturing method according to the present embodiment. FIG. 4A shows a temporal change in the drawing speed, FIG. 4B shows a temporal change in the furnace temperature, and FIG. 4C shows a temporal change in the drawing tension. The optical fiber manufacturing method according to the present embodiment includes an initial drawing step (time t _{0 to} t ₁ ), a drawing speed increasing step (time t _{1 to} t ₃ ), and a steady drawing step (after time t ₃ ). The linear speed increasing step (time t _{1 to} t ₃ ) includes a first linear speed increasing step (time t _{1 to} t ₂ ) and a second linear speed increasing step (time t _{2 to} t ₃ ). The drawing speed, furnace temperature, and drawing tension described below are controlled by the control unit 25.

The initial drawing step (time t _{0 to} t ₁ ) is an initial step after the drawing is started. In this initial drawing step, the optical fiber preform 2 is drawn under the initial conditions of the initial drawing speed V ₁ , the initial furnace temperature T ₁ and the initial drawing tension A ₁ . Of these three parameters, the initial drawing speed V ₁ and the initial furnace temperature T ₁ are set appropriately, and the initial drawing tension A _{1 at} that time is measured by the tension measuring device 22 or the tension measuring device 24.

In the linear velocity rises step following the initial drawing step (time t ₁ ~t _3), together with increasing the drawing speed from the initial line drawing rate V ₁ to the target line drawing rate V _3, during the drawing speed increases from the initial furnace temperature T ₁ is raised the furnace temperature to the target furnace temperature T _3, to maintain the drawing tension to the target line tension a ₃ in the following from the middle of the time t ₂ of the drawing speed increases, the optical fiber The base material 2 is drawn. In this linear speed increasing step, the increase in the furnace temperature may be stepped as shown or may be continuous. Further, when the furnace temperature is raised stepwise, the rise width and time of each stage may be arbitrary.

In the steady drawing step (after time t ₃ ) following this drawing speed increasing step, the optical fiber preform 2 is moved under steady conditions of the target drawing speed V ₃ , the target furnace temperature T ₃ and the target drawing tension A _3. Draw a line.

The linear velocity increasing step (time t _{1 to} t ₃ ) will be described in more detail as follows.

In the first linear velocity increasing step (time t _{1 to} t ₂ ), the linear tensile force becomes the target linear tensile force A ₃ based on the initial linear drawing speed V ₁ , the initial furnace temperature T _1, and the initial linear tensile force A ₁ . The intermediate drawing speed V ₂ and the intermediate furnace temperature T ₂ to be obtained are set to increase the drawing speed from the initial drawing speed V ₁ to the intermediate drawing speed V _2, and the initial furnace is increased during this drawing speed increase. while raising the furnace temperature to an intermediate furnace temperature T ₂ from temperature T _1, to drawing the optical fiber preform 2.

For example, it is preferable that the minimum value of the drawing speed capable of controlling each coating diameter of the glass diameter and coated optical fiber 4 of the glass fiber 3 in a constant is set as an intermediate line drawing rate V _2. Then, the drawing tension in the intermediate line drawing rate V ₂ is a furnace temperature that can be a force A ₃ Tensile target line is set as an intermediate furnace temperature T _2. More specifically, the drawing tension when the drawing speed is changed to the intermediate drawing speed V ₂ is approximated by A ₁ · V ₂ / V ₁ , and this approximate value is equal to the target drawing tension A ₃ . the furnace temperature is changed from the initial furnace temperature T ₁ to an intermediate furnace temperature T ₂ so as to compensate for the difference. The relationship between the difference between the “difference between the initial furnace temperature T ₁ and the intermediate furnace temperature T ₂ ” and the tension to be compensated for is empirically determined in advance for the equipment. The intermediate furnace temperature T ₂ is set based on the relationship.

In the second linear speed increasing step (time t _{2 to} t ₃ ) following the first linear speed increasing step, the target drawing speed is changed from the intermediate drawing speed V ₂ while maintaining the drawing tension at the target drawing tension A _3. with increasing the drawing speed to V _3, while raising the furnace temperature from the intermediate furnace temperature T ₂ to the target furnace temperature T ₃ during the drawing speed increases and drawing the optical fiber preform 2.

The time t ₂ after the second line speed increase step and constant drawing step, while maintaining the tension line to the target line tensile force A ₃ forces and drawing the optical fiber preform 2. That is, since the drawing the optical fiber preform 2 while maintaining the drawing tension in the middle of the previous line speed increase step to the target line tension A ₃ which is a steady wire drawing conditions, in the second line speed rise step, An optical fiber having desired characteristics can be manufactured. Conventionally, an optical fiber having desired characteristics could not be manufactured while the linear velocity was increased. However, in this embodiment, this is possible and the manufacturing yield of the optical fiber is improved.

The drawing tension is the tension of the coated optical fiber 4, and the tension of the coated optical fiber 4 is measured by the tension measuring device 24 in the second linear velocity increasing step and the steady drawing step, and the tension obtained by this measurement is calculated. it is preferred to control the respective drawing speed and furnace temperature while maintaining the target line tension a _3.

In addition, the drawing tension is the tension of the glass fiber 3, and the tension measuring device 22 measures the tension of the glass fiber 3 in the second drawing speed increasing step and the steady drawing step, and the tension obtained by this measurement is obtained. to control the respective drawing speed and furnace temperature while maintaining the target line tension a ₃ is more preferable. Thus, by measuring the tension of the glass fiber 3 and controlling the drawing speed and the furnace temperature so as to make this tension a target value, the characteristics of the optical fiber obtained by drawing can be easily obtained. can do.

When the drawing tension is the tension of the glass fibers 3, the force _{A 3} Tensile target line is preferred in the range of ^{6.4N / mm 2 ~24.0N / mm 2} , In addition, the optical fiber preform 2 The core region is preferably made of pure quartz glass. When the optical fiber preform 2 is drawn under such conditions, a low-loss pure silica core optical fiber having desired characteristics can be obtained.

The line tension if the force is the tension of the glass fibers 3, the force _{A 3} Tensile target line is preferred in the range of ^{32N / mm 2 ~120N / mm 2} , 40N / mm 2 ~96N / mm 2 More preferably, it is in the range. In this case, it is convenient when drawing the optical fiber preform 2 in which GeO ₂ is added to the core region. In this case, it is preferable target line drawing rate V ₃ that is 1500 m / min or more, in this case, a large effect of improving the production yield of the optical fiber. Further, when the drawing speed is 1000 m / min or more, it is preferable that the fluctuation range of the drawing tension is 6.4 N / mm ² or less. In this case, an optical fiber having stable characteristics is obtained. be able to.

As specific numerical examples, for example, the initial drawing speed V ₁ is 100 m / min, the intermediate drawing speed V ₂ is 500 m / min, and the target drawing speed V ₃ is 1500 m / min. The initial furnace temperature T ₁ is 2000 ° C., the intermediate furnace temperature T ₂ is 2100 ° C., the target furnace temperature T ₃ is 2200 ° C., the initial line tensile force A ₁ is 32 N / mm ² , and the target line tensile force _{a 3} is 64N / mm ^2.

It is a schematic block diagram of an optical fiber manufacturing apparatus. It is a figure explaining the optical fiber manufacturing method concerning this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical fiber manufacturing apparatus, 2 ... Optical fiber base material, 3 ... Glass fiber, 4 ... Coated optical fiber, 11 ... Sending apparatus, 12 ... Heating furnace, 13 ... Coating die, 14 ... Ultraviolet irradiation apparatus, 15 ... Coating Dies, 16 ... ultraviolet irradiation device, 17 ... turn pulley, 18 ... take-up device, 19 ... winding device, 21 ... outer diameter measuring device, 22 ... tension measuring device, 23 ... outer diameter measuring device, 24 ... tension measuring device, 25. Control unit.

Claims (9)

A method of manufacturing an optical fiber by heating, softening and drawing an optical fiber preform in a heating furnace,
An initial drawing step of drawing the optical fiber preform under initial conditions of an initial drawing speed V ₁ , an initial furnace temperature T _1, and an initial drawing tension A ₁ ;
With increasing the drawing speed from the initial line drawing rate V ₁ to the target line drawing rate V _3, raising the furnace temperature to the target furnace temperature T ₃ from the initial furnace temperature T ₁ during the drawing speed increases, a linear velocity rises step of maintaining the drawing tension to the target line tension a _3, for drawing the optical fiber preform in the following from the middle of a predetermined time in the drawing speed increases,
A steady drawing step of drawing the optical fiber preform under steady conditions of the target drawing speed V ₃ , the target furnace temperature T _3, and the target drawing tension A ₃ ;
An optical fiber manufacturing method comprising: The linear speed increasing step includes:
Based on the initial drawing speed V ₁ , the initial furnace temperature T ₁ and the initial drawing tension A ₁ , the intermediate drawing speed V ₂ and the intermediate furnace temperature T at which the drawing tension can be the target drawing tension A _{3. 2} is set to increase the drawing speed from the initial drawing speed V ₁ to the intermediate drawing speed V _2, and the initial furnace temperature T ₁ to the intermediate furnace temperature T during the drawing speed increase. _A first linear velocity increasing step of drawing the optical fiber preform while increasing the furnace temperature to ₂ .
While maintaining the drawing tension to the target line tension A _3, wherein with the intermediate line drawing rate V ₂ to increase the drawing speed until said target wire drawing rate V _3, said intermediate between the drawing speed increases while raising the furnace temperature from the furnace temperature T ₂ to the target furnace temperature T _3, a second line speed increase step of drawing the optical fiber preform,
The optical fiber manufacturing method according to claim 1, comprising: The drawing tension is the tension of the coated optical fiber obtained by drawing the optical fiber preform and coating the resin,
In the predetermined time later, and the constant drawing step than the linear velocity rises step by measuring the tension of the coated optical fiber, while maintaining the tension obtained by the measurement to the target line tension A ₃ drawing Control each speed and furnace temperature,
The optical fiber manufacturing method according to claim 1. The drawing tension is the tension of the glass fiber obtained by drawing the optical fiber preform,
In the predetermined time later, and the constant drawing step than the linear velocity rises step, drawing speed by measuring the tension of the glass fiber, while maintaining the tension obtained by the measurement to the target line tension A ₃ And control the furnace temperature respectively
The optical fiber manufacturing method according to claim 1. Optical fiber manufacturing method according to claim 4, wherein the target line tension _{A 3} is characterized in that in the range of ^{6.4N / mm 2 ~24.0N / mm 2} .   6. The optical fiber manufacturing method according to claim 5, wherein the core region of the optical fiber preform is made of pure silica glass. Optical fiber manufacturing method according to claim 4, wherein the target line tension _{A 3} is characterized in that in the range of ^{32N / mm 2 ~120N / mm 2} . Optical fiber manufacturing method according to claim 7, wherein said the target line drawing rate V ₃ is 1500 m / min or more. 8. The method of manufacturing an optical fiber according to claim 7, wherein when the drawing speed is 1000 m / min or more, the fluctuation range of the drawing tension is 6.4 N / mm ² or less.

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