JP7848801B2 - Optical fiber manufacturing apparatus and optical fiber manufacturing method - Google Patents

Description

This disclosure relates to an optical fiber manufacturing apparatus and an optical fiber manufacturing method.
This application claims priority under Japanese application No. 2021-110795, filed on 2 July 2021, and incorporates all the provisions of the said Japanese application.

Patent Document 1 discloses an optical fiber drawing device that actively dampens vibrations of the optical fiber preform by attaching a dummy preform to the optical fiber preform along with the optical fiber preform to the drawing tower and controlling a vibration damping device based on the vibration of the dummy preform.

Japanese Patent Application Publication No. 2004-161499

An optical fiber manufacturing apparatus according to one embodiment for achieving the above objective is:
Line drawing tower and
Mounted on the aforementioned wire drawing tower is a wire drawing furnace for heating and melting optical fiber preforms to spin optical fibers,
The wiring tower is equipped with a mechanism that applies a second moment to the wiring tower, which is in the opposite direction to the direction of action of the first moment applied to the wiring tower by the optical fiber base material,
The imparting mechanism can reduce the second moment as the optical fiber base material becomes smaller.

Furthermore, a method for manufacturing optical fibers according to one embodiment for achieving the above objective is:
The process involves heating and melting the optical fiber preform in a drawing furnace mounted on a drawing tower to spin the optical fiber, and
The method includes the step of applying a second moment to the drawing tower that is in the opposite direction to the direction of action of the first moment applied to the drawing tower by the optical fiber preform, while decreasing the second moment as the optical fiber preform becomes smaller.

Figure 1 is a schematic diagram of the optical fiber manufacturing apparatus according to the first embodiment, showing the situation immediately after the start of the wire drawing process. Figure 2 is a schematic diagram of the optical fiber manufacturing apparatus according to the first embodiment, showing the state after some time has passed since the start of the wire drawing process. Figure 3 is a graph showing the relationship between the weight of the optical fiber preform and the magnitude of the first moment. Figure 4 is a schematic diagram of the optical fiber manufacturing apparatus according to the second embodiment.

[Issues this disclosure aims to address]
Incidentally, the fiber drawing tower can flex due to factors such as the weight of the base material. If the fiber drawing tower flexes, there is a risk that the actual path of the glass fiber will deviate from its planned path. Therefore, in the manufacturing of optical fibers, it is important to suppress the flexing of the fiber drawing tower to prevent a discrepancy between the actual and planned paths.

This disclosure aims to provide an optical fiber manufacturing apparatus and optical fiber manufacturing method capable of suppressing the deflection of a cable drawing tower.

[Effects of this disclosure]
According to this disclosure, it is possible to provide an optical fiber manufacturing apparatus and an optical fiber manufacturing method that can suppress the deflection of the wire drawing tower.

(Description of the embodiments of this disclosure)
First, the embodiments of this disclosure will be listed and described.
An optical fiber manufacturing apparatus according to one aspect of this disclosure is:
(1) Line drawing tower and,
Mounted on the aforementioned wire drawing tower is a wire drawing furnace for heating and melting optical fiber preforms to spin optical fibers,
The wiring tower is equipped with a mechanism that applies a second moment to the wiring tower, which is in the opposite direction to the direction of action of the first moment applied to the wiring tower by the optical fiber base material,
The imparting mechanism can reduce the second moment as the optical fiber base material becomes smaller.
In this configuration, the moment-applying mechanism applies a second moment to the drawing tower that is in the opposite direction to the direction of action of the first moment applied to the drawing tower by the optical fiber preform. Furthermore, since the moment-applying mechanism can decrease the second moment as the size of the optical fiber preform decreases, the deflection of the drawing tower can be suppressed with the optical fiber manufacturing apparatus according to the above configuration.

Furthermore, in an optical fiber manufacturing apparatus according to one aspect of this disclosure,
(2) The granting mechanism comprises a moving mechanism that can move in a predetermined direction, and a weighted body supported by the moving mechanism,
The center of gravity of the aforementioned weighted body moves either towards or away from the center of the line-drawing tower as the moving mechanism moves.
In this configuration, the center of gravity of the weight body in the attachment mechanism moves either towards or away from the center of the line-drawing tower as the movement mechanism moves. Therefore, for example, by moving the movement mechanism in response to the change in the first moment over time, the second moment can be changed over time by the movement of the movement mechanism.

Furthermore, in an optical fiber manufacturing apparatus according to one aspect of this disclosure,
(3) The line marking tower is equipped with a grounding portion that makes contact with the surface on which the line marking tower is placed,
The center of gravity of the aforementioned weight is located outside the outer circumference of the contact area when viewed from above.
This configuration allows for the effective application of a second moment to the line-drawing tower.

Furthermore, in an optical fiber manufacturing apparatus according to one aspect of this disclosure,
(4) The height of the position at which the application mechanism applies the second moment to the wire drawing tower is 0.8 times or more the height of the wire drawing furnace.
If the height of the position where the application mechanism applies the second moment to the wire drawing tower is less than 0.8 times the height of the wire drawing furnace, the second moment cannot be effectively applied to the wire drawing tower, and therefore the first moment cannot be effectively offset by the second moment. For this reason, it is preferable that the height of the position where the application mechanism applies the second moment to the wire drawing tower be 0.8 times or more the height of the wire drawing furnace.

Furthermore, in an optical fiber manufacturing apparatus according to one aspect of this disclosure,
(5) The height of the wire drawing furnace is 12m or more.
The higher the height of the wire drawing furnace, the larger the first moment becomes, thus increasing the effect of applying a second moment to the wire drawing tower. This disclosure is particularly suitable when the height of the wire drawing furnace is 12 m or more.

Furthermore, the optical fiber manufacturing method according to one aspect of this disclosure is:
(6) A step of heating and melting the optical fiber preform in a drawing furnace mounted on a drawing tower to spin an optical fiber,
The method includes the step of applying a second moment to the drawing tower that is in the opposite direction to the direction of action of the first moment applied to the drawing tower by the optical fiber preform, while decreasing the second moment as the optical fiber preform becomes smaller.
With this configuration, a second moment is applied to the drawing tower that is in the opposite direction to the first moment applied to the drawing tower by the optical fiber base material, and this second moment decreases as the base material size decreases, thereby suppressing the deflection of the drawing tower.

Furthermore, the optical fiber manufacturing method according to one aspect of this disclosure is:
(7) The second moment is reduced by moving the center of gravity of the heavy object toward or toward the center of the line drawing tower.
In this configuration, the center of gravity of the mass moves either towards or away from the center of the line-drawing tower, thus allowing the second moment to be changed over time.

Furthermore, the optical fiber manufacturing method according to one aspect of this disclosure is:
(8) In a top view, the center of gravity of the weight is moved outside the outer circumference of the ground contact portion of the line drawing tower.
This configuration allows for the effective application of a second moment to the line-drawing tower.

Furthermore, the optical fiber manufacturing method according to one aspect of this disclosure is:
(9) The second moment is applied to the wire drawing tower at a height of 0.8 times or more the height of the wire drawing furnace.
If the height at which the second moment is applied to the wire drawing tower is less than 0.8 times the height of the wire drawing furnace, the second moment cannot be effectively applied to the wire drawing tower, and therefore the first moment cannot be effectively offset by the second moment. For this reason, it is preferable to apply the second moment to the wire drawing tower at a height of 0.8 times or more the height of the wire drawing furnace.

Furthermore, the optical fiber manufacturing method according to one aspect of this disclosure is:
(10) Spinning the optical fiber for 1,000 km or more from one base material while reducing the second moment.
The longer the fiber length of the spun optical fiber, the larger the optical fiber matrix becomes, and the larger the first moment. Therefore, the longer the fiber length of the spun optical fiber, the greater the need to apply a second moment to the fiber drawing tower, and this disclosure is particularly suitable when spinning optical fibers with a fiber length of 1000 km or more.

(Details of the embodiments of this disclosure)
Specific examples of optical fiber manufacturing apparatus according to embodiments of this disclosure are described below with reference to the drawings. However, this disclosure is not limited to these examples and is intended to include all changes within the meaning and scope of the claims as indicated by the claims.

(First Embodiment)
The optical fiber manufacturing apparatus 1 according to this embodiment will be described with reference to Figure 1. Figure 1 is a schematic configuration diagram illustrating the optical fiber manufacturing apparatus 1. Figure 1 illustrates the situation immediately after the start of the wire drawing process.

As illustrated in Figure 1, the optical fiber manufacturing apparatus 1 comprises a wire drawing tower 2, a chuck 3, a control unit 4, a wire drawing furnace 5, an outer diameter measuring instrument 8, a forced cooling device 9, a coating device 10, a direct-down roller 11, a winding device 12, a bonding mechanism 13, and a capstan device 14. For the sake of explanation in this embodiment, the left-right direction in Figure 1 is referred to as the X-axis direction, the direction perpendicular to the X-axis direction in the horizontal direction is referred to as the Y-axis direction, and the height direction of the wire drawing tower 2 (up-down direction in Figure 1) is referred to as the Z-axis direction, with the center position of the wire drawing tower 2 being the zero point of each axis.

The optical fiber manufacturing apparatus 1 is equipped with a chuck 3 on the upper part of the wire drawing tower 2 for gripping the support rod 6a of the optical fiber preform 6. The chuck 3 is cantilevered to the wire drawing tower 2 by a chuck support part 3a.

The line marking tower 2 can be placed, for example, inside a building. The line marking tower 2 is equipped with a grounding portion 21 that makes contact with the floor surface F of the building (an example of the surface on which the line marking tower 2 is placed). Preferably, the line marking tower 2 is built independently on a foundation, without being connected to any surrounding buildings or the like.

The chuck 3 is movable horizontally (in the X-axis and Y-axis directions). This allows the chuck 3 to adjust the gripping position of the support rod 6a of the optical fiber preform 6 horizontally. Furthermore, the chuck support portion 3a is slid vertically (in the Z-axis direction) by a sliding portion 3b provided vertically along the top of the drawing tower 2. This allows the chuck support portion 3a to be slid downward after the support rod 6a has been gripped by the chuck 3, thereby housing the optical fiber preform 6 inside the drawing furnace 5.

The control unit 4 controls the optical fiber manufacturing apparatus 1. For example, the control unit 4 controls the horizontal movement of the chuck 3 to adjust the gripping position (gripping position) of the support rod 6a of the optical fiber preform 6 in the horizontal direction. The control unit 4 also measures or calculates the weight of the optical fiber preform 6. This weight may be measured with a weighing scale or calculated from the diameter and length of the optical fiber preform 6. For example, the control unit 4 can calculate the weight of the optical fiber preform 6 by inputting the numerical values of the diameter and length of the optical fiber preform 6 to be drawn by the worker using a touch panel or the like (not shown), or by sensing the diameter and length of the optical fiber preform 6 with a sensor (not shown). Based on the calculated weight of the optical fiber preform 6, the control unit 4 calculates the moment acting on the drawing tower 2 and the amount of deflection of the drawing tower 2.

The fiber drawing furnace 5 is supported at the top of the fiber drawing tower 2. The height H of the fiber drawing furnace 5 (i.e., the height H from the floor F to the center of the fiber drawing furnace 5 (the midpoint between the upper and lower ends of the fiber drawing furnace 5)) is 12 m or more. The fiber drawing furnace 5 is equipped with a heater, which heats the optical fiber preform 6 housed inside. The optical fiber preform 6 heated and melted in the fiber drawing furnace 5 has its tip exposed and is drawn as an optical fiber 7.

The optical fiber preform 6 is made of, for example, silica-based glass. The optical fiber preform 6 has a predetermined weight.

The outer diameter measuring instrument 8 is, for example, a laser beam measuring instrument installed below the wire drawing furnace 5. The outer diameter measuring instrument 8 measures the outer diameter of the optical fiber 7. During wire drawing, the outer diameter measuring instrument 8 generates a control signal to control the drive of the capstan device 14, for example, so that the outer diameter value of the optical fiber 7 measured by the outer diameter measuring instrument 8 falls within a predetermined range, and transmits the said control signal to the capstan device 14.

The forced cooling device 9 has an insertion hole through which the high-temperature optical fiber 7, drawn in the drawing furnace 5, is passed. The forced cooling device 9 forcibly cools the optical fiber 7 inserted through the insertion hole by supplying cooling gas into the device 9.

The coating device 10 coats the optical fiber 7, which has been cooled by the forced cooling device 9, with resin. If the resin is an ultraviolet-curing resin, an ultraviolet irradiation device may be provided below the coating device 10 to irradiate the optical fiber 7 with ultraviolet light and cure the resin. After the resin has cured, the optical fiber 7 passes through the roller 11 and the capstan device 14 and is wound onto the winding device 12 with constant tension. The capstan device 14 is controlled based on a control signal from the outer diameter measuring instrument 8, thereby obtaining an optical fiber 7 with a predetermined glass outer diameter.

Incidentally, since the chuck 3 is cantilevered to the drawing tower 2, when the optical fiber base material 6 is supported by the chuck 3, a first moment M1 is applied to the drawing tower 2. At this time, the control unit 4 calculates the first moment M1 based on the following equation (1), using the weight G1 of the optical fiber base material 6 and the distance D1 from the center of the optical fiber base material 6 to the center line CR of the drawing tower 2 (A is a constant). M1 = G1 * D1 + A ... Equation (1)

When a first moment M1 is applied to the wire drawing tower 2, the wire drawing tower 2 bends. When the wire drawing tower 2 bends, the chuck 3 and the optical fiber base material 6 tilt in the lower left direction in Figure 1. When the chuck 3 and the optical fiber base material 6 tilt, the position through which the drawn optical fiber 7 passes shifts from the position of the aligned pass line, and as a result, there is a risk that the optical fiber 7 will come into contact with the forced cooling device 9, etc., causing a break in the wire.

Therefore, the inventor considered methods to solve the above problem and came to the conclusion that the deflection of the drawing tower 2 could be suppressed by applying a second moment M2 to the drawing tower 2 to counteract the first moment M1. Accordingly, the optical fiber manufacturing apparatus 1 according to this embodiment is equipped with a mechanism 13 that can apply a second moment M2 to the drawing tower 2.

The imparting mechanism 13 is located in the X-axis, opposite to the optical fiber base material 6 with respect to the center line CR of the drawing tower 2. The imparting mechanism 13 imparts a second moment M2 to the drawing tower 2 in the opposite direction to the direction of action of the first moment M1 imparted to the drawing tower 2 by the optical fiber base material 6. The imparting mechanism 13 comprises a plate-shaped part 131, a moving mechanism 132, and a weight body 133.

The plate-like portion 131 is, for example, a roughly rectangular flat plate member extending horizontally (in the direction of the X-axis and Y-axis). Preferably, the height h of the plate-like portion 131 (i.e., the height h from the floor surface F to the lower end of the plate-like portion 131) is 0.8 times or more the height H of the drawing furnace 5.

The moving mechanism 132 moves on the plate-shaped portion 131 in a predetermined direction, for example, towards or away from the center of the line drawing tower 2. The center of the line drawing tower 2 is, for example, the center position P of the three axes (X-axis, Y-axis, and Z-axis) of the line drawing tower 2 (the position of the zero point described above). In this embodiment, the moving mechanism 132 moves in the direction of the X-axis. The moving mechanism 132 is electrically connected to the control unit 4, for example, and moves based on instruction signals from the control unit 4. However, the movement of the moving mechanism 132 can also be achieved by means other than such electrical control. For example, the moving mechanism 132 may be moved to a desired position by mechanical control, or it may be moved to a desired position manually by an operator. Furthermore, the moving mechanism 132 may move continuously, or it may move intermittently at predetermined time intervals.

The weight 133 is, for example, a counterweight having a predetermined weight. The weight of the weight 133 can be arbitrarily set by the operator. The weight 133 is supported by the moving mechanism 132. Therefore, when the moving mechanism 132 moves, the weight 133 moves in accordance with the movement of the moving mechanism 132. As a result, the center of gravity 133a of the weight 133 moves in either the direction of the X axis (left-right direction in Figure 1) as the moving mechanism 132 moves. In other words, the center of gravity 133a of the weight 133 moves either towards or away from the center (position P) of the line drawing tower 2. Note that, during line drawing, the center of gravity 133a of the weight 133 is located outside the outer circumference of the ground contact portion 21 when viewed from above. In other words, during line drawing, the center of gravity 133a of the weight 133 is located outside the inner region V of the line drawing tower 2 when viewed from above.

The second moment M2 provided by the imparting mechanism 13 with this configuration is calculated by the control unit 4 based on the following equation (2), using the total weight G2, which is the sum of the weight of the moving mechanism 132 and the weight of the weight body 133, and the distance D2 from the center of gravity 133a of the combined weight body (moving mechanism 132 and weight body 133) to the center line CR of the line drawing tower 2 (where B is a constant): M2 = G2 * D2 + B ... Equation (2)

Next, with reference to Figures 1 and 2, a method for manufacturing optical fibers according to an embodiment of this disclosure will be described. Figure 2 illustrates the situation after some time has elapsed since the start of the wire drawing process. The optical fiber manufacturing method of this embodiment is a method for manufacturing optical fibers 7 by performing the following suspension process and wire drawing process using the optical fiber manufacturing apparatus 1 illustrated in Figures 1 and 2.

(hanging process)
The chuck support part 3a is slid upward by the sliding part 3b, and the support rod 6a of the optical fiber preform 6 used for drawing is gripped by the chuck 3. After the support rod 6a is gripped by the chuck 3, the chuck support part 3a is slid downward, and the optical fiber preform 6 is suspended and housed inside the drawing furnace 5.

(Drawing process)
The optical fiber preform 6 housed inside the drawing furnace 5 is heated by a heater. By heating the tip of the optical fiber preform 6 to a predetermined temperature (for example, 2000°C), the optical fiber preform 6 is melted, and the glass mass at the tip is pulled off to create the lead. Subsequently, drawing is performed while gradually reducing the diameter of the glass. As the drawing progresses, the chuck support part 3a is gradually slid downward, so that the optical fiber 7 is drawn from the tip of the optical fiber preform 6.

In the optical fiber manufacturing apparatus 1, before drawing the optical fiber, it is necessary to align the positions of the chuck 3 and the roller 11 directly below it, the central axes of the drawing furnace 5, the forced cooling device 9, the coating device 10, etc., and to align the pass line through which the drawn optical fiber 7 will pass. This pass line alignment is usually performed without suspending the optical fiber base material 6.

However, for the reasons mentioned above, when the optical fiber base material 6 is suspended, the position through which the drawn optical fiber 7 passes will deviate from the position of the aligned pass line. As a result, there is a risk that the optical fiber 7 may come into contact with the forced cooling device 9, etc., causing a break in the optical fiber.

Furthermore, as illustrated in Figure 2, the optical fiber preform 6 becomes smaller as the drawing progresses, so the weight of the optical fiber preform 6 decreases as the drawing progresses. As illustrated in Figure 3, the weight of the optical fiber preform 6 and the magnitude of the first moment M1 are linearly proportional. Therefore, the first moment M1 decreases as the drawing progresses. For this reason, the inventor realized that in order to suppress the deflection of the drawing tower 2, it is effective to apply a second moment M2 in accordance with the first moment M1, and to change the second moment M2 in accordance with the change in the first moment M1.

Therefore, the inventor came up with the idea of reducing the second moment M2 in accordance with the decrease in the weight of the optical fiber base material 6 by moving the moving mechanism 132 that supports the weight body 133.

In the state illustrated in Figure 1, the control unit 4 calculates the first moment M1, calculates the distance D2 at which the first moment M1 and the second moment M2 are equal, and moves the moving mechanism 132 to the position corresponding to the distance D2.

As the line drawing progresses, the state illustrated in Figure 2 is reached. In the state illustrated in Figure 2, the control unit 4 calculates the first moment m1. The first moment m1 is calculated based on the following equation (3), using the weight g1 of the optical fiber base material 6 and the distance D1 from the optical fiber base material 6 to the center line CR of the line drawing tower 2. Note that weight g1 is less than weight G1. m1 = g1 * D1 + A ... Equation (3)

The control unit 4 calculates the first moment m1, calculates the distance d2 at which the first moment m1 and the second moment m2 are equal, and moves the moving mechanism 132 to the position corresponding to the distance d2. The second moment m2 is calculated based on equation (4), using the total weight G2, which is the sum of the weight of the moving mechanism 132 and the weight of the weight body 133, and the distance d2 from the center of gravity 133a of the combined weight body of the moving mechanism 132 and weight body 133 to the center line CR of the line drawing tower 2. m2 = G2 * d2 + B ... Equation (4)

Since weight g1 is less than weight G1, the first moment m1 is less than the first moment M1. Therefore, the second moment m2 must be less than the second moment M2, and the distance d2 becomes shorter than the distance D2. In other words, as the weight of the optical fiber base material 6 decreases, the moving mechanism 132 approaches the center (position P) of the wire drawing tower 2.

In this way, the application mechanism 13 can reduce the second moment M2 as the weight of the optical fiber base material 6 decreases. The application mechanism 13 may continuously reduce the second moment M2, or it may intermittently reduce the second moment M2 at predetermined time intervals. This control is continued until the entire effective portion of the optical fiber base material 6 is drawn.

Further line drawing is performed, and when the entire effective portion of the optical fiber preform 6 is lined, the line drawing is completed. In this embodiment of the optical fiber manufacturing method, a large optical fiber preform 6 is used, and more than 1,000 km of optical fiber 7 is spun from one optical fiber preform 6.

As described above, in the optical fiber manufacturing apparatus 1 and optical fiber manufacturing method according to this embodiment, the imparting mechanism 13 imparts second moments M2 and m2 to the drawing tower 2 in the opposite direction to the direction of action of the first moments M1 and m1. Furthermore, the imparting mechanism 13 decreases the second moment M2 as the optical fiber base material 6 decreases. Therefore, according to the optical fiber manufacturing apparatus 1 and optical fiber manufacturing method according to this embodiment, the deflection of the drawing tower 2 can be suppressed.

In this embodiment, as the center of gravity 133a moves closer to the center (position P) of the line-drawing tower 2 as the moving mechanism 132 moves, the second moment M2 can be reduced over time by the movement of the moving mechanism 132.

If the center of gravity 133a is located inside the outer circumference of the grounding portion 21 when viewed from above, it is not possible to obtain sufficient distance from the weighted body 133 to the center line CR, and therefore, it is not possible to effectively apply the second moments M2 and m2 to the wire drawing tower 2. However, in this embodiment, the center of gravity 133a of the weighted body 133 is located outside the outer circumference of the grounding portion 21 when viewed from above. Therefore, according to the optical fiber manufacturing apparatus 1 and optical fiber manufacturing method of this embodiment, it is possible to effectively apply the second moments M2 and m2 to the wire drawing tower 2.

(Second Embodiment)
Next, with reference to Figure 4, the optical fiber manufacturing apparatus 1A according to this embodiment will be described. In the description of the optical fiber manufacturing apparatus 1A, components similar to those in the optical fiber manufacturing apparatus 1 according to the first embodiment will be denoted by the same reference numerals and described accordingly, and their descriptions will be omitted as appropriate.

Figure 4 is a schematic diagram of the optical fiber manufacturing apparatus 1A. Optical fiber manufacturing apparatus 1A differs from optical fiber manufacturing apparatus 1 in that it further includes a chuck 30, a wire drawing furnace 50, an outer diameter measuring instrument 80, a forced cooling device 90, a coating device 100, a direct roller 110, a winding device 120, and a capstan device 140. Optical fiber manufacturing apparatus 1A also differs from optical fiber manufacturing apparatus 1 in that the application mechanism 13 can move the weight body 133 not only to the right side of the wire drawing tower 2 in Figure 4, but also to the left side of the wire drawing tower 2. Thus, optical fiber manufacturing apparatus 1A is an optical fiber manufacturing apparatus having two wire drawing lines for one wire drawing tower. In this embodiment, the control unit 4 controls the horizontal movement of the chuck 30 to adjust the gripping position (gripping position) of the support rod 60a of the optical fiber preform 60 in the horizontal direction. The control unit 4 also measures or calculates the weight of the optical fiber preform 60.

Chuck 30 may have the same configuration as chuck 3. Also, the configuration from the drawing furnace 50 to the capstan device 140 may be the same as the configuration from the drawing furnace 5 to the capstan device 14. However, in the state shown in Figure 4 of this embodiment, the weight G3 of the optical fiber preform 60 is less than the weight G1 of the optical fiber preform 6.

The chuck 30 comprises a chuck support 30a with the same configuration as the chuck support 3a, and a slide 30b with the same configuration as the slide 3b. The chuck 30 grips the support rod 60a of the optical fiber preform 60, which has the same configuration as the optical fiber preform 6. Since the optical fiber preform 60 has a predetermined weight, when the optical fiber preform 60 is supported by the chuck 30, a third moment M3 is applied to the drawing tower 2 in the opposite direction to the action of the first moment M1. The third moment M3 is calculated based on the weight G3 of the optical fiber preform 60 and the distance D3 from the optical fiber preform 60 to the center line CR of the drawing tower 2, using the following equation (5) (where C is a constant): M3 = G3 * D3 + C ... Equation (5)

Since the weight G3 of the optical fiber preform 60 is less than the weight G1 of the optical fiber preform 6, the third moment M3 is less than the first moment M1. Therefore, in this embodiment as well, the chuck 3 and the optical fiber preform 6 tilt in the lower left direction in Figure 1, and as a result, the wire drawing tower 2 bends.

The control unit 4 calculates a distance D4 that satisfies the following equation (6), and moves the moving mechanism 132 of the application mechanism 13 to the position corresponding to the distance D4. Note that distance D4 is the distance from the center of gravity (center of gravity 133a) of the combined weight of the moving mechanism 132 and the weight body 133 to the center line CR of the line drawing tower 2. M1 - M3 = M2 = G2 * D4 + B ... Equation (6)

When the moving mechanism 132 moves to a position corresponding to distance D4, the first moment M1 becomes equal to the sum of the second moment M2 and the third moment M3, thus making the deflection of the wire drawing tower 2 approximately zero. In this way, even if the present disclosure is applied to an optical fiber manufacturing apparatus 1A having two wire drawing lines for one wire drawing tower, the same effects as in the first embodiment can be obtained.

Next, examples of this embodiment will be described. However, this disclosure is not limited to the following embodiments.

Under various conditions that differed from each other, optical fibers 7 were spun using the optical fiber manufacturing apparatus 1 according to this embodiment, and the positional displacement of the drawing furnace 5 and the pass line, as well as the frequency of breakage, were compared at the start and end of drawing.

Tables 1 and 2 show the positional displacement of the wire drawing furnace 5 and the pass line, as well as the frequency of wire breakage, at the start and end of wire drawing under various conditions. Note that for the positional displacement of the wire drawing furnace 5 at the start and end of wire drawing, a displacement of 3.0 mm or less is considered good, and a displacement exceeding 3.0 mm is considered poor. Therefore, the good range for the displacement of the wire drawing furnace 5 is 3.0 mm or less. For the positional displacement of the pass line at the start and end of wire drawing, a displacement of 0.3 mm or less is considered good, and a displacement exceeding 0.3 mm is considered poor. Therefore, the good range for the displacement of the pass line is 0.3 mm or less. For the frequency of wire breakage, a rate of 0.1 cases/1000 km or less is considered good, and a rate exceeding 0.1 cases/1000 km is considered poor. Therefore, the good range for the frequency of wire breakage is 0.1 cases/1000 km or less. The evaluation is based on a comprehensive assessment of these factors and expressed in three stages: A, B, and C. A indicates good performance, B indicates relatively good performance, and C indicates poor performance. The initial position of the moving mechanism 132 is the distance D2 from the center of gravity 133a to the center line CR of the wire drawing tower 2, and the final position of the moving mechanism 132 is the distance d2 from the center of gravity 133a to the center line CR of the wire drawing tower 2. The fiber length is the length of the optical fiber 7 spun from a single optical fiber matrix 6.

First, let's explain Experimental Example 1 and Experimental Example 2. In Experimental Example 1, both the distance D2 at the start of line drawing and the distance d2 at the end of line drawing are 750 mm. In other words, in Experimental Example 1, the moving mechanism 132 is not moved during the line drawing process. On the other hand, in Experimental Example 2, the distance D2 at the start of line drawing is 1304 mm, but the distance d2 at the end of line drawing is 754 mm. In other words, in Experimental Example 2, the moving mechanism 132 is moved to approach the center (position P) of the line drawing tower 2 during the line drawing process. Other parameters are the same in Experimental Example 1 and Experimental Example 2.

In Experimental Example 1, the misalignment of the drawing furnace 5 at the start of drawing, the misalignment of the pass line at the start of drawing, and the frequency of wire breakage all deviated from the acceptable range, resulting in a rating of C. On the other hand, in Experimental Example 2, the misalignment of the drawing furnace 5 and the pass line at the start and end of drawing, as well as the frequency of wire breakage, were all within the acceptable range, resulting in a rating of A. From Experimental Examples 1 and 2, it was confirmed that moving the moving mechanism 132 closer to the center (position P) of the drawing tower 2 during the drawing process can reduce the misalignment of the drawing furnace 5, the misalignment of the pass line, and the frequency of wire breakage.

Next, we will describe Experimental Examples 3 to 5. In Experimental Examples 3 to 5, the height h of the plate-like section 131 is different in each case. Also, in Experimental Examples 3 to 5, although the weights of the weighted bodies are different in each case, they are kept approximately the same. The initial position and final position of the moving mechanism 132 are different in each case. Other parameters are the same in Experimental Examples 3 to 5. In all of Experimental Examples 3 to 5, the moving mechanism 132 is moved to approach the center (position P) of the line drawing tower 2 during the line drawing process. As shown in Table 1, the height h of the plate-like section 131 in Experimental Example 3 is 15.0 m, which is lower than 0.8 times the height H of the line drawing furnace 5, i.e., 16.8 m. On the other hand, the height h of the plate-like section 131 in Experimental Examples 4 to 5 is 18.0 m and 18.5 m, respectively, which is higher than 0.8 times the height H of the line drawing furnace 5, i.e., 16.8 m.

In Experimental Example 3, although the position of the moving body was controlled by changing it to the maximum extent, the positional displacement of the line drawing furnace 5 at the start and end of line drawing was within the good range, but the positional displacement of the pass line and the frequency of disconnections at the start and end of line drawing deviated from the good range. In particular, the frequency of disconnections deviated significantly from the good range, so it was evaluated as C. In Experimental Example 4, although the positional displacement of the line drawing furnace 5 at the start and end of line drawing and the positional displacement of the pass line at the end of line drawing were within the good range, the positional displacement of the pass line at the start of line drawing deviated slightly from the good range, and the frequency of disconnections deviated from the good range, so it was evaluated as B. On the other hand, in Experimental Example 5, the positional displacement of the line drawing furnace 5 at the start and end of line drawing, the positional displacement of the pass line, and the frequency of disconnections were all within the good range, so it was evaluated as A. Thus, from these examples, it was confirmed that when the height h of the plate-like portion 131 is less than 0.8 times the height H of the drawing furnace 5, the second moments M2 and m2 are not effectively applied to the drawing tower 2. In other words, it was confirmed that it is preferable for the height h of the plate-like portion 131 to be 0.8 times or more the height H of the drawing furnace 5.

Next, we will describe Experimental Examples 6 to 10. As shown in Tables 1 and 2, in Experimental Examples 6 to 10, the height H of the position of the line drawing furnace 5, the height h of the position of the plate-like part 131, the initial position of the moving mechanism 132, and the final position of the moving mechanism 132 are all different, but the other parameters are the same. Also, in Experimental Examples 6 to 7 and 9, the moving mechanism 132 is not moved during the line drawing process, but in Experimental Examples 8 and 10, the moving mechanism 132 is moved to approach the center (position P) of the line drawing tower 2 during the line drawing process. Furthermore, the height H of the position of the line drawing furnace 5 in Experimental Example 6 is 10.5 m, i.e., less than 12.0 m, whereas the height H of the position of the line drawing furnace 5 in Experimental Examples 7 to 10 is 12.0 m or more.

In Experimental Example 6, the positional displacement of the drawing furnace 5, the positional displacement of the pass line, and the frequency of wire breakage at the start and end of drawing were all within the good range, so the evaluation was set to A. On the other hand, in Experimental Examples 7 and 9, where the height H of the position of the drawing furnace 5 is higher than in Experimental Example 6, the positional displacement of the drawing furnace 5, the positional displacement of the pass line, and the frequency of wire breakage at the start of drawing deviated from the good range, so the evaluation was set to C. In particular, in Experimental Example 9, where the height H of the position of the drawing furnace 5 is the highest, the amount of positional displacement of the drawing furnace 5 and the pass line at the start of drawing was the largest, and the frequency of wire breakage was also the highest. From this, it was confirmed that the positional displacement of the drawing furnace 5, the positional displacement of the pass line, and the frequency of wire breakage at the start of drawing increase as the height H of the position of the drawing furnace 5 increases. Furthermore, in Experimental Example 6, since the positional displacement of the drawing furnace 5 and the positional displacement of the pass line were already within the good range at the start of drawing, it was confirmed that there was no need to move the moving mechanism 132 during the drawing process.

On the other hand, in Experimental Example 8, where only the initial position and final position of the moving mechanism 132 differ from Experimental Example 7, and in Experimental Example 10, where only the initial position and final position of the moving mechanism 132 differ from Experimental Example 9, the positional displacement of the wire drawing furnace 5 and the pass line, as well as the frequency of wire breakage, at the start and end of wire drawing were all within a good range, so the evaluation was set to A. The higher the height H of the position of the wire drawing furnace 5, the more effectively the first moment M1 is applied to the wire drawing tower 2. From these examples, it was confirmed that applying this disclosure is useful when the height H of the position of the wire drawing furnace 5 is 12 m or more.

Next, we will describe Experimental Examples 11 to 13. As shown in Table 2, although the initial position of the moving mechanism 132, the final position of the moving mechanism 132, the length of the optical fiber base material 6, and the fiber length are all different, the other parameters are the same. Also, in Experimental Examples 11 and 12, the moving mechanism 132 is not moved during the line drawing process, but in Experimental Example 13, the moving mechanism 132 is moved to approach the center (position P) of the line drawing tower 2 during the line drawing process. Furthermore, the fiber length in Experimental Example 11 is 788 km, or less than 1000 km, while the fiber length in Experimental Examples 12 and 13 is 1002 km, or more than 1000 km.

In Experimental Example 11, the misalignment of the drawing furnace 5, the misalignment of the pass line, and the frequency of disconnections at the start and end of drawing were all within the acceptable range, so the evaluation was set to A. On the other hand, in Experimental Example 12, which had a longer fiber length than Experimental Example 11, the misalignment of the drawing furnace 5, the misalignment of the pass line, and the frequency of disconnections at the start of drawing deviated from the acceptable range, so the evaluation was set to C. Therefore, it was confirmed that the misalignment of the drawing furnace 5, the misalignment of the pass line, and the frequency of disconnections at the start of drawing increased with increasing fiber length. Furthermore, in Experimental Example 11, since the misalignment of the drawing furnace 5 and the misalignment of the pass line were already within the acceptable range at the start of drawing, it was confirmed that there was no need to move the moving mechanism 132 during the drawing process.

On the other hand, in Experimental Example 13, where only the initial position and final position of the moving mechanism 132 differed from Experimental Example 12, the positional displacement of the drawing furnace 5 and the pass line at the start and end of drawing, as well as the frequency of disconnection, were all within a good range, so the evaluation was set to A. The longer the fiber length of the spun optical fiber 7, the larger the optical fiber preform 6 becomes, and the larger the first moment M1 becomes. However, from these examples, it was confirmed that applying this disclosure is useful when the fiber length is 1000 km or more.

Although this disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of this disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the embodiments described above and can be changed to a number, position, shape, etc. that is suitable for carrying out this disclosure.

In the second embodiment, the optical fiber manufacturing apparatus 1A is configured to include only the control unit 4, but it may also include a control unit 40 having the same hardware configuration as the control unit 4.

In the above embodiment, the center of gravity 133a approaches the center (position P) of the wire drawing tower 2 as the moving mechanism 132 moves, but it may also move away from the center of the wire drawing tower 2. For example, when the wire drawing of the effective portion of the optical fiber preform 6 is completed and a new optical fiber preform 6 is to be attached, it is preferable to move the center of gravity 133a away from the center of the wire drawing tower 2.

In the above embodiment, the moving mechanism 132 moves in the direction of the X axis, but it may also move in the direction of the Y axis or the Z axis.

Furthermore, in the above embodiment, the second moment of the applying mechanism 13 is controlled by the movement of the moving mechanism 132, but the second moment may also be controlled by changing the weight of the applying mechanism 13. For example, a liquid or the like may be placed in the container of the applying mechanism 13, and the weight of the applying mechanism 13 may be changed by gradually discharging the liquid from the container as the line drawing progresses.

In the embodiments described above, an optical fiber manufacturing apparatus having one or two drawing lines per drawing tower was used, but this disclosure is also applicable to optical fiber manufacturing apparatus having three or more drawing lines per drawing tower.

Although the above embodiment was described using a wire drawing furnace, this disclosure is also applicable to resistance furnaces, induction heating furnaces, and the like.

1, 1A: Optical fiber manufacturing apparatus 2: Wire drawing tower 3, 30: Chuck 3a, 30a: Chuck support part 3b, 30b: Slide part 4, 40: Control unit 5, 50: Wire drawing furnace 6, 60: Optical fiber base material 6a, 60a: Support rod 7: Optical fiber 8, 80: Outer diameter measuring instrument 9, 90: Forced cooling device 10, 100: Coating device 11, 110: Direct roller 12, 120: Winding device 13: Application mechanism 14, 140: Capstan device 21: Grounding part 131: Plate-shaped part 132: Moving mechanism 133: Weight body 133a: Center of gravity CR: Centerline D1, D2, D3, d2: Distance F: Floor surface H, h: Height M1, m1: First moment M2, m2: Second moment M3: Third moment P: Position V: Area

Claims (10)

Line drawing tower and
Mounted on the aforementioned wire drawing tower is a wire drawing furnace for heating and melting optical fiber preforms to spin optical fibers,
The wiring tower is equipped with a mechanism that applies a second moment to the wiring tower, which is in the opposite direction to the direction of action of the first moment applied to the wiring tower by the optical fiber base material,
The imparting mechanism is an optical fiber manufacturing apparatus that can reduce the second moment as the optical fiber preform becomes smaller. The granting mechanism comprises a moving mechanism that can move in a predetermined direction, and a weighted body supported by the moving mechanism.
The optical fiber manufacturing apparatus according to claim 1, wherein the center of gravity of the weight moves in a direction toward or toward the center of the wire drawing tower as the moving mechanism moves. The aforementioned line-drawing tower is equipped with a grounding portion that makes contact with the surface on which the line-drawing tower is placed.
The optical fiber manufacturing apparatus according to claim 2, wherein the center of gravity of the weight is located outside the outer circumference of the grounding portion when viewed from above. The optical fiber manufacturing apparatus according to any one of claims 1 to 3, wherein the height of the position where the imparting mechanism imparts the second moment to the drawing tower is 0.8 times or more the height of the position of the drawing furnace. The optical fiber manufacturing apparatus according to any one of claims 1 to 3 , wherein the height of the position of the wire drawing furnace is 12 m or more. The process involves heating and melting the optical fiber preform in a drawing furnace mounted on a drawing tower to spin the optical fiber, and
A method for manufacturing an optical fiber, comprising the step of applying a second moment to the drawing tower that is in the opposite direction to the direction of action of the first moment applied to the drawing tower by the optical fiber preform, while decreasing the second moment as the optical fiber preform becomes smaller. The optical fiber manufacturing method according to claim 6, wherein the second moment is reduced by moving the center of gravity of the weight towards or away from the center of the line drawing tower. The optical fiber manufacturing method according to claim 7, wherein, in a top view, the center of gravity of the weight is moved outside the outer circumference of the ground contact portion of the wire drawing tower. The optical fiber manufacturing method according to any one of claims 6 to 8, wherein the second moment is applied to the drawing tower at a height of 0.8 times or more the height of the drawing furnace. A method for manufacturing optical fibers according to any one of claims 6 to 8 , wherein the optical fiber is spun to a length of 1,000 km or more from a single optical fiber matrix while reducing the second moment.