JP6573508B2 - Manufacturing method and manufacturing apparatus for optical fiber - Google Patents

Description

  The present invention relates to a method and an apparatus for manufacturing an optical fiber.

The optical fiber strand manufacturing process includes a drawing process in which a base material is melted and taken up by a heating furnace, and is wound after the resin is applied and cured around the glass portion. In the drawing process, drawing tension is an important parameter that affects the characteristics of the optical fiber.
This corresponds to the tensile tension applied to the optical fiber by pulling, and even in an optical fiber drawn by the same optical fiber preform, the optical characteristics are widely changed by changing the drawing tension. Are known.
Therefore, in order to manufacture an optical fiber strand stably, it is calculated | required that wire drawing force is controlled uniformly. In addition, a method has been proposed in which the change in optical characteristics in the longitudinal direction at the base material stage is reduced by changing the drawing tension using the change in optical characteristics due to the drawing tension (for example, Patent Document 1). , 2).

In order to make the drawing tension constant, it is necessary to accurately grasp the drawing tension at that time. Since it is the tension applied to the glass part that affects the optical characteristics of the glass part, it is necessary to accurately grasp the tension applied to the glass part of the optical fiber.
However, as described in Patent Document 2 as described below, it has been difficult to accurately and continuously measure the drawing tension applied to the glass portion (see paragraph 0020).
“In general, a contact tension meter is often used for the wire tension measuring device 22. The contact tension meter is advantageous in that it is inexpensive and has high measurement accuracy. In general, the tension cannot be measured while the good part is being manufactured.In addition to the contact tensiometer, circularly polarized light is irradiated from the side of the glass fiber 3. Although there is a method for measuring the magnitude of the drawing tension generated in the glass fiber 3 from the change in the polarization state, it is more expensive than the contact tension meter and the measurement accuracy is also lowered. Instead of measuring directly, the post-coating tension described below is often measured and the line tension is determined from this post-coating tension. "

In order to make the drawing tension constant, in general, a load cell or the like provided on the pulley is used when passing the optical fiber after coating (forming a coating layer) on the bare optical fiber through the pulley. In many cases, the tension is measured, and the manufacturing conditions are controlled so that the tension (post-coating tension) of the coated optical fiber is constant based on the measured value.
However, the post-coating tension includes the coating burden tension generated by the coating device, so when the post-coating tension is controlled to be constant, the linear tensile force applied to the glass part is not necessarily constant. It was hard to say.
For example, in order to keep the outer diameter of the optical fiber constant, a take-off speed (drawing speed) with a high response speed is often used, but it is known that the coating load tension changes due to a change in the drawing speed. Thus, fluctuations in the drawing speed led to longitudinal fluctuations in the optical characteristics of the optical fiber. Under such circumstances, there has been a demand for a manufacturing method and a manufacturing apparatus that can keep the drawing tension of the glass part constant.

Japanese Patent Laid-Open No. 8-217481 JP 2013-28508 A

  One aspect of the present invention has been made in view of the above circumstances, and in manufacturing an optical fiber, a light that can keep the drawing tension applied to the bare optical fiber before coating is accurately and constant. An object of the present invention is to provide a method and an apparatus for manufacturing a fiber strand.

One aspect of the present invention is a coating process in which an optical fiber preform is heated in a heating furnace to be melt-spun to form a bare optical fiber, and a coating layer is formed on the outer circumference of the bare optical fiber. A step of changing the direction of the bare optical fiber by a direction changer while floating the bare optical fiber with a fluid between the spinning step and the coating step, and the direction changer. The manufacturing method of the optical fiber which detects the floating position of the said bare optical fiber in and controls the manufacturing conditions of the said optical fiber based on the detected value of the said floating position is provided.
The controlled production condition may be a supply power for heating to the heating furnace in a spinning process.
The controlled manufacturing condition may be an entry speed of the optical fiber preform into the heating furnace.

One aspect of the present invention is a spinning unit that forms an optical fiber bare wire by melting and spinning an optical fiber preform in a heating furnace, a coating unit that provides a coating layer made of a resin on the outer periphery of the optical fiber bare wire, A direction changer that changes the direction of the bare optical fiber while floating the bare optical fiber with a fluid between the spinning part and the coating part, and a floating position of the bare optical fiber in the direction changer An apparatus for manufacturing an optical fiber is provided, which includes a position detection unit that detects the position of the optical fiber, and a control unit that controls manufacturing conditions of the optical fiber based on the detected value of the flying position.
The controlled production condition may be a supply power for heating to the heating furnace in a spinning process.
The controlled manufacturing condition may be an entry speed of the optical fiber preform into the heating furnace.

  One aspect of the present invention is a coating process in which an optical fiber preform is heated in a heating furnace to be melt-spun to form a bare optical fiber, and a coating layer is formed on the outer circumference of the bare optical fiber. A step of changing the direction of the bare optical fiber by a direction changer while floating the bare optical fiber with a fluid between the spinning step and the coating step, and the direction changer. And detecting the floating position of the bare optical fiber at, adjusting the flow rate of the fluid in the direction changer so that the floating position is constant based on the detected value of the floating position, and based on the flow rate Provided is a method of manufacturing an optical fiber, which controls manufacturing conditions of the optical fiber.

  One aspect of the present invention is a spinning unit that forms an optical fiber bare wire by melting and spinning an optical fiber preform in a heating furnace, a coating unit that provides a coating layer made of a resin on the outer periphery of the optical fiber bare wire, A direction changer that changes the direction of the bare optical fiber while floating the bare optical fiber with a fluid between the spinning part and the coating part, and a floating position of the bare optical fiber in the direction changer A position detection unit for detecting the flow rate, a flow rate regulator for adjusting the flow rate of the fluid in the direction changer so that the floating position is constant, and a manufacturing condition of the optical fiber is controlled based on the flow rate And an optical fiber manufacturing apparatus comprising a control unit.

According to one aspect of the present invention, the control unit controls the manufacturing conditions of the optical fiber based on the detected floating position of the bare optical fiber, thereby controlling the flying height of the bare optical fiber within a certain range. Since it can be maintained, the drawing tension applied to the bare optical fiber can be maintained within a certain range.
In one aspect of the present invention, since the manufacturing conditions are controlled based on the flying position of the glass portion (bare optical fiber), the optical fiber bare wire can be kept in a certain range regardless of the drawing speed. it can. In other words, since the drawing speed can be adjusted while keeping the drawing tension of the bare optical fiber in a certain range, the operation range of the process can be widened.
In addition, when the coating part is replaced for renewal or repair, the coating burden tension may change due to the replacement, but even in this case, stable light quality can be obtained without having to reset the manufacturing conditions. Fiber strands can be manufactured.

It is a schematic diagram which shows schematic structure of an example of the manufacturing apparatus of the optical fiber strand which can implement 1st Embodiment of the manufacturing method of the optical fiber strand which concerns on this invention. It is a schematic diagram which shows the cross-section of the direction changer of the manufacturing apparatus shown in FIG. It is a front view which shows the example of a 1st direction changer. It is a front view which shows the example of a 2nd direction changer. It is a front view which shows the example of a 3rd direction changer. It is a schematic diagram which shows schematic structure of an example of the manufacturing apparatus of the optical fiber which can implement 2nd Embodiment of the manufacturing method of the optical fiber which concerns on this invention. It is a schematic diagram which shows schematic structure of an example of the manufacturing apparatus of the optical fiber which can implement 3rd Embodiment of the manufacturing method of the optical fiber which concerns on this invention. It is a graph which shows a test result.

  FIG. 1 is a schematic diagram showing a schematic configuration of an example of an optical fiber manufacturing apparatus that can implement the first embodiment of the optical fiber manufacturing method according to the present invention. Hereinafter, the positional relationship of each component may be expressed based on the drawing direction. For example, the upstream side is the upstream side in the drawing direction, and the downstream side is the downstream side in the drawing direction.

The manufacturing apparatus 1 shown in FIG. 1 includes a spinning unit 10, a direction changer 20 (20A, 20B, 20C) (non-contact holding mechanism), a tension measuring unit 30 (wire tension measuring device), and a first coating unit. 40, the 1st hardening part 50, the 2nd coating part 60, the 2nd hardening part 70, the span apparatus 80, the turn pulley 90, and the control part 100 are provided.
Although not shown, a winder for winding the optical fiber 5 is provided on the downstream side of the turn pulley 90.

  The spinning unit 10 includes a heating furnace 11, and the optical fiber preform 2 is heated and melt-spun by the heating furnace 11 to form the bare optical fiber 3.

The direction changer 20 changes the direction of the bare optical fiber 3. In the manufacturing apparatus 1, three direction changers 20 are used. These direction changers 20 are referred to as first to third direction changers 20A to 20C from the upstream side to the downstream side in the drawing direction, respectively.
The first direction changer 20A directs the bare optical fiber 3 drawn vertically downward from the optical fiber preform 2 horizontally by 90 ° direction change.
The vertically downward path of the bare optical fiber 3 from the optical fiber preform 2 to the first direction changer 20A is referred to as a first path L1, and the optical fiber from the first direction changer 20A to the second direction changer 20B. The horizontal path of the bare wire 3 is referred to as a second path L2.
A surface including the first path L1 and the second path L2 is referred to as P1. The X direction is a direction along the second path L2 in the plane P1, and the Y direction is a direction perpendicular to the plane P1.

The second direction changer 20B directs the bare optical fiber 3 in a direction opposite to the second path L2 by 180 ° direction change.
The third direction changer 20C turns the bare optical fiber 3 vertically downward by changing the direction of 90 °.
The horizontal path of the bare optical fiber 3 from the second direction changer 20B to the third direction changer 20C is referred to as a third path L3, and the vertically downward optical fiber bare line 3 from the third direction changer 20C. The route is referred to as a fourth route L4.

Hereinafter, the structure of the direction changer 20 will be described in detail.
FIG. 3 is a diagram showing the first direction changer 20A (hereinafter, simply referred to as direction changer 20A). The direction changer 20A is circular in plan view, and a guide groove 21 is formed on the outer peripheral surface 20a over the entire circumference.
The direction changer 20A has a posture in which the central axis direction (direction perpendicular to the paper surface of FIG. 3) coincides with the Y direction and the radial direction D1 (see FIG. 2) is directed in the direction along the surface P1 (see FIG. 1). Installed at. A direction along the outer peripheral surface 20a is referred to as a circumferential direction.

  As shown in FIG. 2, a fluid (for example, air) outlet 22 that floats the bare optical fiber 3 wired along the guide groove 21 is formed along the guide groove 21 at the bottom of the guide groove 21. ing. The blowout port 22 can be formed over the entire length of the guide groove 21 at least in a range through which the bare optical fiber 3 passes.

The direction changer 20 </ b> A can discharge the fluid in the space (fluid reservoir 25) secured inside the direction changer 20 </ b> A into the guide groove 21 through the outlet 22.
The direction changer 20 </ b> A is connected to an introduction path 26 (see FIG. 3) for introducing fluid from the outside into the fluid reservoir 25.
For example, the direction changer 20 </ b> A can introduce a fluid from the outside into the fluid reservoir 25 through the introduction path 26 and discharge the fluid into the guide groove 21 through the outlet 22. The flow rate of the fluid blown into the guide groove 21 is equal to the flow rate of the fluid introduced into the direction changer 20A.

  As shown in FIG. 2, the guide groove 21 is formed to be inclined with respect to the radial direction D1 so that the distance between the inner side surfaces 21c and 21c (dimension in the Y direction) gradually increases toward the outer side in the radial direction. It is preferable. The two inner side surfaces 21c and 21c preferably have the same inclination angle θ1 with respect to the radial direction D1.

  In the direction changer 20 </ b> A shown in FIG. 3, the bare optical fiber 3 enters the guide groove 21 from the incoming line portion 23 and exits from the guide groove 21 at the outgoing line portion 24. Since the outgoing line portion 24 is located at a position shifted from the incoming line portion 23 in the circumferential direction by about 90 ° in the circumferential direction, the direction of the bare optical fiber 3 is changed by 90 °.

FIG. 4 is a diagram showing a second direction changer 20B (hereinafter, simply referred to as a direction changer 20B). The direction changer 20B is circular in plan view, and a guide groove 31 is formed on the outer peripheral surface 20a over the entire circumference. The direction changer 20B can change the direction of the bare optical fiber 3 by 180 °.
The direction changer 20B is installed in a posture in which the central axis direction coincides with the Y direction and the radial direction D1 (see FIG. 2) is directed in the direction along the plane P1 (see FIG. 1).

A fluid outlet 32 for floating the bare optical fiber 3 is formed along the guide groove 31 at the bottom of the guide groove 31. The blowout port 32 can be formed over the entire length of the guide groove 31 at least in the range through which the bare optical fiber 3 passes.
The cross-sectional shape of the guide groove 31 is the same as the cross-sectional shape of the guide groove 21 (see FIG. 2). A structure similar to the structure shown in FIG. 2 can be adopted as the structure for discharging the fluid into the guide groove 31 through the outlet 32.

The direction changer 20B can discharge the fluid in the space (fluid reservoir 25) secured in the direction changer 20B into the guide groove 21 through the outlet 32.
The direction changer 20 </ b> B is connected to an introduction path 26 (see FIG. 4) for introducing fluid from the outside into the fluid reservoir 25.
For example, the direction changer 20 </ b> B can introduce a fluid from the outside into the fluid reservoir 25 through the introduction path 26 and discharge the fluid into the guide groove 31 through the outlet 32. The flow rate of the fluid blown out to the guide groove 31 is equal to the flow rate of the fluid introduced into the direction changer 20B.

  In the direction changer 20 </ b> B, the bare optical fiber 3 enters the guide groove 31 from the incoming line portion 33, and exits from the guide groove 31 at the outgoing line portion 34 at a position shifted by about 180 ° C. in the circumferential direction with respect to the incoming line portion 33. Thus, the direction change of 180 ° is performed.

FIG. 5 is a diagram showing a third direction changer 20C (hereinafter, simply referred to as a direction changer 20C). The direction changer 20C has the same configuration as the direction changer 20A shown in FIG.
In the direction changer 20 </ b> C, the bare optical fiber 3 enters the guide groove 21 from the incoming line portion 43 and exits from the guide groove 21 at the outgoing line portion 44, whereby the direction change of 90 ° is performed.

The tension measuring unit 30 includes a position detecting unit 35 that detects the position of the bare optical fiber 3, and a measuring unit main body 36 that measures the drawing tension based on the position of the bare optical fiber 3 detected by the position detecting unit 35. And have.
The position detector 35 is provided downstream of the third direction changer 20C and detects the position of the bare optical fiber 3 in the fourth path L4.
As the position detection unit 35, for example, a laser (optical) position sensor can be used. The laser-type position sensor receives, for example, light emitted from a light source (laser light source) toward the bare optical fiber 3 by a detector installed opposite to the light source, and generates light based on the light. The position of the bare fiber 3 can be detected.

  As will be described later, the measurement unit main body 36 can measure the drawing tension of the bare optical fiber 3 based on the correlation between the previously measured drawing tension and the position of the bare optical fiber 3. The measurement unit main body 36 may include a display unit such as a liquid crystal panel that displays measurement values.

  The control unit 100 controls the power supplied to the heating furnace 11 on the basis of the detected value of the flying height (floating position) of the bare optical fiber 3 by the position detection unit 35, whereby the optical fiber preform in the heating furnace 11 is controlled. The heating temperature of 2 can be adjusted.

The first coating unit 40 applies (coats) a coating material such as urethane acrylate resin to the outer peripheral surface of the bare optical fiber 3 to form a primary coating layer. The coating material used for the primary coating layer is, for example, an ultraviolet curable resin.
The first curing unit 50 includes, for example, one or a plurality of UV lamps, and cures the primary coating layer by ultraviolet irradiation.

  The second coating unit 60 applies (coats) a coating material such as urethane acrylate resin to the outer peripheral surface of the primary coating layer to form a secondary coating layer. Thereby, the optical fiber strand intermediate body 4 is obtained. The secondary coating layer preferably has a higher Young's modulus than the primary coating layer. The coating material used for the secondary coating layer is, for example, an ultraviolet curable resin.

The second curing unit 70 includes one or a plurality of UV lamps 70a, and cures the secondary coating layer by ultraviolet irradiation. Thereby, the optical fiber 5 is obtained.
The second curing unit 70 includes, for example, a plurality of pairs of UV lamps 70a provided across a space through which the optical fiber strand intermediate body 4 passes.
The covering material formed on the outer peripheral surface of the bare optical fiber 3 is not limited to a two-layer structure, and may be a one-layer structure or a structure having three or more layers.

The span device 80 can twist the optical fiber 5.
The turn pulley 90 can take the optical fiber 5 and change the direction of the optical fiber 5 to guide it to a winder (not shown).

Next, a first embodiment of the method for manufacturing an optical fiber according to the present invention will be described by taking as an example the case where the optical fiber 5 is manufactured using the manufacturing apparatus 1.
(Spinning process)
In the spinning unit 10, the optical fiber preform 2 is heated and melt-spun to form a bare optical fiber 3.

(Direction change by direction changer)
The bare optical fiber 3 drawn vertically downward (first path L1) from the optical fiber preform 2 is directed horizontally (second path L2) by 90 ° direction change in the first direction changer 20A. It is done.
The bare optical fiber 3 is directed in a direction opposite to the second path L2 (third path L3) by the 180 ° direction change in the second direction changer 20B, and 90 ° in the third direction changer 20C. By changing the direction of °, the vertical downward (fourth path L4) is obtained.

  In the direction changers 20 </ b> A to 20 </ b> C, the bare optical fiber 3 can be floated by discharging the fluid in the fluid reservoir 25 into the guide grooves 21 and 31 through the outlets 22 and 32. More specifically, as shown in FIG. 2, the pressure difference between the deep portion 21d and the shallow portion 21e of the guide groove 21 is increased by the discharged fluid, so that a radially outward force is exerted on the bare optical fiber 3. By acting, the bare optical fiber 3 is levitated.

The following explanation is possible for the principle that the optical fiber floats by the fluid.
If there is a shield in the fluid flow path, the shield receives a force from the fluid. The fluid having a limited flow path applies a force to the shield while satisfying the momentum conservation law and the energy conservation law. For example, when a weight is levitated in a triangular pyramid shaped flow path where the flow path area gradually increases, the pressure difference generated before and after the weight changes depending on the position. Accordingly, the weight can be stopped at a position where the buoyancy received by the weight from the fluid and the weight load are balanced. When the weight load is constant, there is a clear positive correlation between the floating position (more precisely, the flow channel area limited by the flow channel and the weight) and the flow rate. This phenomenon is widely used as the principle of a flow meter.

The principle of the flow meter, paradoxically, indicates that a correlation is created between the floating position of the weight and the weight load when the fluid flow rate is constant. For this reason, the present inventor considered that the weight load can be measured from the floating position by floating the weight in a triangular pyramid-shaped flow path through which a constant flow rate of fluid flows. The present inventor further indicates that the above-mentioned correlation occurs in the same manner when the linear body floats in the guide groove having a V-shaped cross section, and therefore, a constant flow of fluid is caused to flow through the guide groove having the V-shaped cross section. It was thought that the load on the striatum could be measured by levitating the strip.
Also, the force that an object receives from a fluid with a constant flow rate depends on the shape of the surface that receives the force, but in the normal optical fiber drawing process, the fiber outer diameter is kept constant by continuously changing the drawing speed. Since a simple control method is common, an optical fiber can be regarded as an infinitely long cylinder. Further, since the mass of the optical fiber is very small, the load applied to the fluid flowing through the guide groove having a V-shaped cross section can be regarded as almost equal to the tensile tension.

  From these facts, when the optical fiber is levitated in the guide groove in which a constant flow rate of fluid is flowed, the tensile tension can be kept constant by keeping the levitating position constant. Therefore, a part of the drawing optical fiber (bare optical fiber) is floated in the guide groove where a constant flow rate of fluid is passed, and the floating position is kept constant so that the glass part (bare optical fiber) Such a drawing tension can be kept constant.

(First coating process)
In the first coating portion 40, a coating material such as urethane acrylate resin is applied (coated) to the outer peripheral surface of the bare optical fiber 3 to form a primary coating layer.

(First curing step)
In the 1st hardening part 50, a primary coating layer is hardened, for example by ultraviolet irradiation by a UV lamp.

(Second coating process)
In the second coating portion 60, a coating material such as urethane acrylate resin is applied (coated) to the outer peripheral surface of the primary coating layer to form a secondary coating layer. Thereby, the optical fiber strand intermediate body 4 is obtained.

(Second curing step)
In the second curing unit 70, the secondary coating layer is cured by, for example, ultraviolet irradiation with a UV lamp. Thereby, the optical fiber 5 is obtained.

(Span process)
The optical fiber 5 can be twisted by the span device 80 as necessary.

(Pickup process)
The optical fiber 5 is taken up by the turn pulley 90 and changed in direction, and taken up by a winder (not shown).

The flying height of the bare optical fiber 3 in the direction changer 20 (20A, 20B, 20C) is affected by the force received from the fluid blown out in the guide groove 21 and the drawing tensile force applied to the bare optical fiber 3. receive. Usually, the higher the drawing tension applied to the bare optical fiber 3, the smaller the flying height, and the lower the drawing tension, the larger the flying height.
For example, in the third direction changer 20C, when the drawing tension is high, the force in the direction in which the bare optical fiber 3 approaches the direction changer 20C increases, and thus the flying height of the bare optical fiber 3 decreases.
On the other hand, when the drawing tension applied to the bare optical fiber 3 is low, the force in the direction in which the bare optical fiber 3 approaches the direction changer 20C becomes small. The amount gets bigger.

When the flying height of the bare optical fiber 3 in the third direction changer 20C (see FIG. 5) increases or decreases, the position in the X direction of the bare optical fiber 3 in the fourth path L4 changes.
For example, when the flying height of the bare optical fiber 3 in the third direction changer 20C decreases, the bare optical fiber 3 in the fourth path L4 moves in a direction approaching the third direction changer 20C. The position of is on the right side in FIGS. 1 and 5.
On the other hand, when the flying height of the bare optical fiber 3 increases, the bare optical fiber 3 of the fourth path L4 moves in a direction away from the third direction changer 20C. It is on the left side in FIG.

As described above, the position detection unit 35 can detect the position of the bare optical fiber 3 in the fourth path L4.
The position in the X direction of the bare optical fiber 3 in the fourth path L4 is a position corresponding to the flying height of the bare optical fiber 3 in the third direction changer 20C. If the position in the X direction of the bare optical fiber 3 of L4 is detected, the flying height (floating position) of the bare optical fiber 3 in the direction changer 20C can be grasped.

In this manufacturing method, based on the flying height (floating position) of the bare optical fiber 3 detected by the position detection unit 35, the control unit 100 controls the supply power for heating of the heating furnace 11, thereby heating The heating temperature of the optical fiber preform 2 in the furnace 11 can be adjusted.
For example, when the flying height of the bare optical fiber 3 is large, the flying height can be suppressed by adjusting the power supplied to the heating furnace 11 to lower the heating temperature of the optical fiber preform 2. On the other hand, when the flying height of the bare optical fiber 3 is small, the flying height can be increased by adjusting the power supplied to the heating furnace 11 to increase the heating temperature of the optical fiber preform 2. As a control method, feedback control such as PID control is preferable.
Thus, by controlling the manufacturing conditions of the optical fiber 5 (power supplied to the heating furnace 11), the flying height of the bare optical fiber 3 can be kept within a certain range. The applied tensile force can be kept within a certain range.

In the conventional manufacturing method, in order to make the drawing tension constant, the manufacturing conditions are set so that the tension of the coated optical fiber is constant under the premise that the drawing speed does not change. The method of controlling was taken.
However, since the post-coating tension includes the coating burden tension generated by the coating apparatus, if the drawing speed varies, the optical fiber optical characteristics may vary in the longitudinal direction even if the post-coating tension is constant. Could happen.
On the other hand, according to the manufacturing method of the present embodiment, since the manufacturing conditions are controlled based on the flying height (floating position) of the glass portion (bare optical fiber 3), the bare optical fiber is used regardless of the drawing speed. The drawing tension of the wire 3 can be kept within a certain range. In other words, the drawing speed can be adjusted while keeping the drawing tension of the bare optical fiber 3 within a certain range. Therefore, the range of operation of the process can be expanded.
In addition, when the coating parts 40 and 60 are replaced for renewal or repair, the coating burden tension may change due to the replacement. Even in this case, stable quality can be obtained without resetting the manufacturing conditions. The optical fiber 5 can be manufactured.
Further, if the power supplied to the heating furnace 11 is a control target, there is an advantage that the influence on other manufacturing conditions can be reduced.

In the manufacturing method of the present embodiment, the supply power for heating to the heating furnace 11 which is one of the manufacturing conditions in manufacturing the optical fiber 5 is controlled, but the manufacturing conditions controlled by the control unit 100 are heating. The power supplied to the furnace 11 is not limited.
The manufacturing condition controlled by the control unit 100 may be, for example, the entry speed of the optical fiber preform 2 into the heating furnace 11. In FIG. 1, the speed at which the optical fiber preform 2 enters the heating furnace 11 is the speed at which the optical fiber preform 2 moves downward. The approach speed of the optical fiber preform 2 can be controlled by adjusting the driving force of a drive mechanism (such as a motor) that moves the optical fiber preform 2 relative to the heating furnace 11.

When the flying height of the bare optical fiber 3 is large, the flying height can be suppressed by reducing the entry speed of the optical fiber preform 2 into the heating furnace 11. On the other hand, when the flying height of the bare optical fiber 3 is small, the flying height can be increased by increasing the entry speed of the optical fiber preform 2 into the heating furnace 11. As a control method, feedback control such as PID control is preferable.
If the approach speed of the optical fiber preform 2 into the heating furnace 11 is controlled, the influence on other manufacturing conditions can be reduced.

The manufacturing condition to be controlled may be a drawing speed. The drawing speed can be controlled by adjusting the driving speed of the turn pulley 90, for example. When the flying height of the bare optical fiber 3 is large, the flying height can be suppressed by increasing the drawing speed. On the other hand, when the flying height of the bare optical fiber 3 is small, the flying height can be increased by lowering the drawing speed.
In addition to this, the manufacturing condition to be controlled may be the supply pressure of the resin in the coating units 40 and 60.

In the manufacturing method of the present embodiment, as shown below, the tensile force of the bare optical fiber 3 can be measured using the tension measuring unit 30.
In order to measure the drawing tension of the bare optical fiber 3, the correlation between the drawing tension applied to the bare optical fiber 3 and the position of the fourth optical path bare wire 3 in the X direction is calculated in advance. Keep track. For example, it is preferable that the position detection unit 35 detects the position in the X direction of the bare optical fiber 3 of the fourth path L4 under a plurality of conditions with different drawing tensions by a preliminary test.

Data relating to the correlation between the drawing tension force measured in advance and the position of the bare optical fiber 3 is input to the measuring unit main body 36 of the tension measuring unit 30, and this data is used to detect the position detecting unit 35. The drawing tension is derived from the value. For example, the drawing tension can be derived by collating the detection value of the position detection unit 35 with the data.
Since the detection value of the position detection unit 35 is a value corresponding to the flying height of the bare optical fiber 3, the drawing tension applied to the glass part (bare optical fiber 3) can be accurately measured. In addition, since the drawing tension is derived from the detection value of the position detector 35, the drawing tension can be continuously measured in the length direction of the bare optical fiber 3 in the manufacturing process of the optical fiber 5. Therefore, when manufacturing conditions are controlled based on measured values, it is advantageous in terms of quick response. In addition, when a tension abnormality occurs, it becomes easy to identify the cause of the abnormality, so that the repair becomes easy.

In this method, the drawing tension can be measured without contacting the bare optical fiber 3. Therefore, unlike the case where a contact tension meter is used, the bare optical fiber 3 is not damaged and the strength of the bare optical fiber 3 does not deteriorate. Therefore, disconnection and yield deterioration due to strength deterioration can be prevented.
Furthermore, in measuring the wire pulling force, there is no disadvantage in manufacturing the optical fiber 5 because the apparatus configuration is not complicated or manufacturing conditions are not restricted.

  Note that the manufacturing conditions (for example, supply power for heating to the heating furnace 11) may be controlled based on the measured value of the drawing tension obtained by the tension measuring unit 30.

FIG. 6 is a schematic diagram showing a schematic configuration of an example of an optical fiber manufacturing apparatus capable of implementing the second embodiment of the optical fiber manufacturing method according to the present invention. Hereinafter, about the same structure as the manufacturing apparatus 1 of 1st Embodiment shown in FIG. 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
In the manufacturing apparatus 1A shown in FIG. 6, two direction changers 20 are used. These direction changers 20 are referred to as first and second direction changers 20A and 20D, respectively.

The second direction changer 20D turns the bare optical fiber 3 vertically downward by changing the direction by 90 °. The vertically downward path of the bare optical fiber 3 from the second direction changer 20D is referred to as a third path L5.
The position detector 35 is provided downstream of the second direction changer 20D and detects the position of the bare optical fiber 3 in the third path L5.

  Also in the manufacture of the optical fiber 5 using the manufacturing apparatus 1A, as in the manufacturing method of the first embodiment, the manufacturing conditions (for example, the supply power for heating to the heating furnace 11, the entry speed of the optical fiber preform 2) Etc.) can be controlled to keep the flying height of the bare optical fiber 3 within a certain range. Therefore, the drawing tension applied to the bare optical fiber 3 can be kept within a certain range.

FIG. 7 is a schematic diagram showing a schematic configuration of an example of an optical fiber manufacturing apparatus that can implement the third embodiment of the optical fiber manufacturing method according to the present invention.
The manufacturing apparatus 1B shown in FIG. 7 differs from the manufacturing apparatus 1 shown in FIG. 1 in that it includes a control unit 110 and a flow rate regulator 120.
Based on the detection signal from the position detection unit 35, the control unit 110 uses the flow rate adjuster 120 to control the flow rate of the fluid introduced into the direction changer 20 (for example, the direction changer 20C), thereby changing the direction. The flying height of the bare optical fiber 3 in the vessel 20 can be adjusted. As the flow controller 120, a mass flow controller (MFC) or the like can be used.

The position detection unit 35 outputs a detection signal to the control unit 110 based on the position information of the bare optical fiber 3 in the fourth path L4. This detection signal is, for example, a signal corresponding to the position of the bare optical fiber 3 in the guide groove 21 in the direction changer 20.
The control unit 110 controls the flow rate of the fluid introduced into the direction changer 20 using the flow rate adjuster 120 based on the detection signal. Thereby, in the direction changer 20, the flow rate of the fluid discharged from the outlet 22 to the guide groove 21 can be controlled, and the flying height of the bare optical fiber 3 can be adjusted.

For example, when the flying height of the bare optical fiber 3 is reduced and the bare optical fiber 3 in the fourth path L4 is displaced in a direction approaching the direction changer 20C, the control unit 110 moves to the direction changer 20C. Increase the flow rate of the fluid. As a result, in the direction changer 20C, the flow rate of the fluid discharged from the outlet 22 into the guide groove 21 is increased, and the flying height of the bare optical fiber 3 is recovered.
On the other hand, when the flying height of the bare optical fiber 3 is increased and the bare optical fiber 3 in the fourth path L4 is displaced in a direction away from the direction changer 20C, the control unit 110 moves to the direction changer 20C. Reduce the flow rate of the fluid. Thereby, in the direction changer 20C, the flow rate of the fluid discharged from the outlet 22 to the guide groove 21 is reduced, and the flying height of the bare optical fiber 3 is suppressed.
In this way, the floating position of the bare optical fiber 3 can be kept constant.
When feedback control such as PID control is employed as the control method, the flow rate of the fluid can be controlled with high responsiveness.

In this embodiment, based on the flow rate of the fluid in the direction changer 20 (20C) adjusted so that the floating position of the bare optical fiber 3 is constant, the control unit 100 performs manufacturing conditions (for example, the heating furnace 11). Power supply for heating, an approach speed of the optical fiber preform 2, and the like).
For example, based on the fluid flow rate in the direction changer 20 (20C), the control unit 100 controls the supply power for heating of the heating furnace 11, and thereby the heating temperature of the optical fiber preform 2 in the heating furnace 11 is controlled. Can be adjusted.
Specifically, when the flow rate of the fluid in the direction changer 20 (20C) is large, the flow rate of the fluid is suppressed by adjusting the power supplied to the heating furnace 11 to increase the heating temperature of the optical fiber preform 2. Can do. On the other hand, when the fluid flow rate is small, the fluid flow rate can be increased by adjusting the power supplied to the heating furnace 11 to lower the heating temperature of the optical fiber preform 2. As a control method, feedback control such as PID control is preferable.
In this way, by controlling the manufacturing conditions of the optical fiber 5, the drawing tension applied to the bare optical fiber 3 can be kept within a certain range.

In the manufacturing apparatus 1B shown in FIG. 7, the optical fiber bare of the fourth path L4 is subjected to a plurality of conditions with different drawing tensions and a plurality of conditions with different flow rates of the fluid to the direction changer 20 by preliminary tests. The position of the line 3 in the X direction can be detected by the position detector 35 in advance. Thereby, the correlation between the flow rate of the fluid introduced into the direction changer 20 that can keep the flying position of the bare optical fiber 3 constant and the drawing tension applied to the bare optical fiber 3 is grasped.
The measurement unit main body 36 can measure the drawing tension from the introduction flow rate of the fluid to the direction changer 20 using the correlation between the introduction flow rate of the fluid and the drawing tension.

As mentioned above, although the embodiment of the manufacturing method and the manufacturing apparatus of the optical fiber of the present invention has been described, the present invention is not limited to the above examples, and can be appropriately changed without departing from the spirit of the invention. is there.
In the manufacturing apparatus 1 shown in FIG. 1, the position detection unit 35 is provided on the downstream side of the third direction changer 20C, and in the manufacturing apparatus 1A shown in FIG. 6, the position detection unit 35 is provided on the downstream side of the second direction changer 20D. However, the position of the position detection unit is not limited to these examples.
For example, in the manufacturing apparatus 1 shown in FIG. 1, the position detectors may be provided on one or more downstream sides of the direction changers 20A, 20B, and 20C.
When the position detector is provided downstream of the direction changer 20A (between the direction changer 20A and the direction changer 20B), the flying height of the bare optical fiber 3 in the direction changer 20A can be detected. When the position detector is provided downstream of the direction changer 20B (between the direction changer 20B and the direction changer 20C), the flying height of the bare optical fiber 3 in the direction changer 20B can be detected.
Further, the direction change in the direction changer 20 can be performed at any position after the spinning process and before the first coating process. The installation position of the direction changer 20 may be any position as long as it is downstream of the spinning unit 10 and upstream of the first coating unit 40.
The number of direction changers 20 may be one or more.

If the outer diameter of the bare optical fiber 3 varies, the flying height in the direction changer 20 may change. Therefore, the outer diameter of the bare optical fiber 3 may be measured.
In order to measure the outer diameter of the bare optical fiber 3, for example, an outer diameter measuring unit (not shown) is provided on the downstream side of the position detecting unit 35 (between the position detecting unit 35 and the first coating unit 40). be able to. As the outer diameter measurement unit, for example, an optical measurement device including a light source and a detector can be used. For example, this measuring apparatus emits light from a light source (laser light source or the like) installed at a side position of the bare optical fiber 3, and receives forward scattered light by a detector installed facing the light source. The outer diameter of the bare optical fiber 3 is measured by analyzing the pattern or strength.
When measuring the outer diameter of the bare optical fiber 3, a measurement signal from the outer diameter measuring unit is sent to the control unit 100, and the control unit 100 performs control in consideration of the outer diameter of the bare optical fiber 3. Can do.
Since the force that the object receives from the fluid is affected by the size of the surface of the object that receives the force, for example, when the outer diameter of the bare optical fiber 3 increases, the flying height increases even if the drawing tension is constant. On the other hand, when the outer diameter of the bare optical fiber 3 is reduced, the flying height is reduced even if the drawing tension is constant. Therefore, in consideration of the variation in the flying height caused by the change in the outer diameter of the bare optical fiber 3, the control unit 100 sets the manufacturing conditions (for example, the heating furnace 11 to cancel the influence of the variation. Heating power supply etc.) can be controlled.

[Example 1]
The manufacturing apparatus 1 shown in FIG. 1 was produced.
The floating turning radius of the bare optical fiber 3 in the direction changer 20 (20A, 20B, 20C) was about 62.5 mm.
As shown in FIG. 2, the inclination angle θ of the inner surface 21c of the guide groove 21 of each of the direction changers 20A and 20C with respect to the radial direction R is 0.5 °. The width at the bottom of the guide groove 21 was 50 μm. The guide groove 31 of the direction changer 20B has the same structure as the guide groove 21.
The fluid introduced into the direction changers 20A to 20C was dehumidified air, and the temperature was room temperature (about 24 ° C.).
The air introduction flow rate was 100 liters / minute for each of the direction changers 20A and 20C, and 200 liters / minute for the direction changer 20B.

In the spinning section 10, the optical fiber preform 2 was melt-spun to obtain a bare optical fiber 3 (outer diameter 125 μm).
An optical fiber bare wire 3 drawn vertically downward (first path L1) from the optical fiber preform 2 is redirected horizontally (second path L2) by the first direction changer 20A, and then the second The direction change by 180 ° in the direction changer 20B is directed in the direction opposite to the second path L2 (third path L3), and the direction downward by 90 ° in the third direction changer 20C (fourth downward) Route L4).
A primary coating layer made of an ultraviolet curable resin is formed on the outer peripheral surface of the bare optical fiber 3 by the first coating unit 40, and the primary coating layer is cured by irradiating ultraviolet rays at the first curing unit 50. Then, a secondary coating layer made of an ultraviolet curable resin is formed on the outer peripheral surface of the primary coating layer, and the secondary coating layer is cured by irradiating with ultraviolet rays at the second curing unit 70, and the optical fiber 5 (outer diameter 250 μm) Got.
The optical fiber 5 was wound by a winder (not shown) through the span device 80 and the turn pulley 90. The drawing speed was 1000 m / min.

  Thus, when manufacturing the optical fiber strand 5, when the drawing tension applied to the bare optical fiber 3 was measured with time, it was confirmed that the drawing tension was kept constant.

FIG. 8 shows the correlation between the tensile force applied to the bare optical fiber 3 and the position of the bare optical fiber 3 in the fourth path L4 in the X direction (detected value of the position detector 35) by the preliminary test. It is a graph which shows the result investigated. The detection value (output) of the position detector 35 is substantially equal to the radial height position (floating position) from the bottom of the guide groove 21 of the direction changer 20C. For example, a load cell, a contact tension meter, or the like can be used to measure the drawing tension in the preliminary test. In this example, the flow rate of the fluid in the direction changer 20 is constant. 1 gf is about 9.81 × 10 ⁻³ N.
FIG. 8 shows that the drawing tension changes according to the flying height of the bare optical fiber 3.

DESCRIPTION OF SYMBOLS 1,1A ... Manufacturing apparatus of an optical fiber strand, 2 ... Optical fiber preform, 3 ... Bare optical fiber, 5 ... Optical fiber strand, 10 ... Spinning part, 20, 20A-20D ... Direction changer, 21, DESCRIPTION OF SYMBOLS 31 ... Guide groove, 22, 32 ... Outlet, 35 ... Position detection part, 40 ... 1st coating part, 60 ... 2nd coating part, 100 ... Control part.

Claims (8)

A spinning process in which an optical fiber preform is heated in a heating furnace to be melt spun to form a bare optical fiber;
A coating step of providing a coating layer made of a resin on the outer periphery of the bare optical fiber,
Between the spinning step and the coating step, the direction of the bare optical fiber is changed by a direction changer while floating the bare optical fiber with a fluid,
Detecting a floating position of the optical fiber bare in the direction change device, to control the production conditions of the optical fiber on the basis of the detection value of the floating position, the method for manufacturing an optical fiber.   The method for manufacturing an optical fiber according to claim 1, wherein the controlled manufacturing condition is supply power for heating to the heating furnace in a spinning process.   The method for manufacturing an optical fiber according to claim 1, wherein the controlled manufacturing condition is an entry speed of the optical fiber preform into the heating furnace. A spinning section that melts and spins an optical fiber preform in a heating furnace to form a bare optical fiber;
A coating portion for providing a coating layer made of a resin on the outer periphery of the bare optical fiber;
A direction changer that changes the direction of the bare optical fiber while floating the bare optical fiber with a fluid between the spinning portion and the coating portion,
A position detector for detecting a floating position of the bare optical fiber in the direction changer;
And a control unit that controls manufacturing conditions of the optical fiber based on the detected value of the floating position.   The apparatus for manufacturing an optical fiber according to claim 4, wherein the controlled manufacturing condition is a supply power for heating to the heating furnace.   The apparatus for manufacturing an optical fiber according to claim 4, wherein the controlled manufacturing condition is an entry speed of the optical fiber preform into the heating furnace. A spinning process in which an optical fiber preform is heated in a heating furnace to be melt spun to form a bare optical fiber;
A coating step of providing a coating layer made of a resin on the outer periphery of the bare optical fiber,
Between the spinning step and the coating step, the direction of the bare optical fiber is changed by a direction changer while floating the bare optical fiber with a fluid,
Detecting the floating position of the bare optical fiber in the direction changer, and adjusting the flow rate of the fluid in the direction changer based on the detection value of the floating position so that the floating position is constant; An optical fiber manufacturing method for controlling manufacturing conditions of an optical fiber based on a flow rate. A spinning section that melts and spins an optical fiber preform in a heating furnace to form a bare optical fiber;
A coating portion for providing a coating layer made of a resin on the outer periphery of the bare optical fiber;
A direction changer that changes the direction of the bare optical fiber while floating the bare optical fiber with a fluid between the spinning portion and the coating portion,
A position detector for detecting a floating position of the bare optical fiber in the direction changer;
A flow rate regulator for adjusting the flow rate of the fluid in the direction changer so that the flying position is constant;
And a control unit that controls manufacturing conditions of the optical fiber based on the flow rate.

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