CN116217069A

CN116217069A - Method for manufacturing optical fiber

Info

Publication number: CN116217069A
Application number: CN202211544740.2A
Authority: CN
Inventors: 冈崎岩; 岩原圣
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 2021-12-06
Filing date: 2022-12-02
Publication date: 2023-06-06
Also published as: JP2023083734A

Abstract

Disclosed is a method for producing an optical fiber, wherein the amount of coating resin used can be reduced. A method for manufacturing an optical fiber, wherein a glass fiber formed by drawing an optical fiber base material while heating and melting the same is introduced into a resin coating device filled with a resin, the resin is coated around the glass fiber, and then the resin coated around the glass fiber is cured by a curing treatment to cure the resin, thereby manufacturing an optical fiber having a resin-coated layer formed around the glass fiber. The manufacturing method comprises the following steps: performing an extraction step for picking up the optical fiber by a pickup device; a wire speed raising step of raising the wire speed of the wire drawing after the drawing and before the stable wire drawing until the wire speed of the wire drawing is stabilized; and performing a stable drawing step of obtaining stable drawing of the product. The viscosity of the resin in the resin coating device in the wire speed increasing step is higher than the viscosity of the resin in the resin coating device in the stable drawing step.

Description

Method for manufacturing optical fiber

Technical Field

The present disclosure relates to a method of manufacturing an optical fiber.

Background

Patent document 1 discloses: in order to reduce breakage in a resin coating device caused by rapid change in the line speed at the time of transition from a drawing base material to a product optical fiber base material when the manufacturing line speed of an optical fiber is increased, the resin supply pressure is controlled at the time of increase in the line speed. Specifically, in patent document 1, in a section from a line speed in which the line speed of the optical fiber line is increased until the line speed reaches the product manufacturing line speed, the rate of increase of the resin supply pressure with respect to the line speed increase rate is made smaller than the rate of increase of the resin supply pressure with respect to the line speed increase rate determined by the product manufacturing line speed.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2001-066476

Disclosure of Invention

[ problem to be solved by the invention ]

In the case of increasing the line speed, that is, from the start of production to the time when the line speed reaches the product production line speed, the fiber yarn produced is disposed of without being used as a product, and therefore, it is desirable to reduce the amount of resin used in the line speed increase as much as possible. However, the purpose of patent document 1 is to reduce breakage of the optical fiber wire during the increase in the wire speed, and not to control the coating diameter during the increase in the wire speed, so that the effect of reducing the amount of resin used during the increase in the wire speed cannot be expected.

Accordingly, an object of the present disclosure is to provide a method for manufacturing an optical fiber capable of reducing the amount of resin used.

[ means for solving the problems ]

A method of manufacturing an optical fiber according to one embodiment of the present disclosure is a method of manufacturing an optical fiber,

wherein a glass fiber formed by drawing while heating and melting an optical fiber base material is fed into a resin coating apparatus filled with a resin, the resin is coated around the glass fiber, and then the resin coated around the glass fiber is cured by subjecting the resin to a curing treatment to thereby produce an optical fiber having a resin-coated layer formed around the glass fiber,

the method comprises the following steps:

performing an extraction step for picking up an extraction of the optical fiber by a pickup device;

a wire speed increasing step of increasing the wire speed of the wire drawing after the drawing and before the stable wire drawing until the wire speed of the wire drawing is reached at the time of the stable wire drawing; and

performing a stable drawing step of obtaining the stable drawing of the product,

the viscosity of the resin in the resin coating device in the line speed increasing step is higher than the viscosity of the resin in the resin coating device in the stable drawing step.

[ Effect of the invention ]

According to the present disclosure, it is possible to provide a method for manufacturing an optical fiber capable of reducing the amount of resin used by reducing the amount of pulling of the glass fiber into the resin coating apparatus against the coating resin during the increase in the wire speed.

Drawings

Fig. 1 is a schematic configuration diagram of an optical fiber manufacturing apparatus according to the present embodiment.

Fig. 2 is a graph showing a relationship between a linear velocity of an optical fiber and a temperature of a resin coating apparatus provided in the manufacturing apparatus of the optical fiber in fig. 1.

FIG. 3 is a graph showing the relationship between the linear velocity of an optical fiber and the temperature of a resin in a resin coating apparatus.

FIG. 4 is a cross-sectional view of an optical fiber manufactured by the optical fiber manufacturing apparatus of FIG. 1.

Fig. 5 (a) is a graph showing temperature control of the resin coating apparatus in examples 1 to 4, (b) is a graph showing change in outer diameter of the optical fiber when temperature control of the resin coating apparatus is performed as in examples 1 to 4, (c) is a graph showing the amount of the primary resin used in examples 1 to 4, and (d) is a graph showing the amount of the secondary resin used in examples 1 to 4.

Description of symbols

1: optical fiber manufacturing apparatus

10: wire drawing furnace

11: forced cooling device

12: resin coating device

12A: first die

12B: second die

13: resin supply device

13A: a first supply part

13B: a second supply part

14: resin curing device

15: guide roller

16: pickup unit

17: winding reel

18: wire drawing control device

19: temperature control device

19a,19b,20a,20b: piping arrangement

21a,21b: piping heating device

100: optical fiber

101: glass fiber

102: a first resin layer

103: a second resin-coated layer

G: optical fiber base material

G1: glass fiber

And G2: optical fiber

P: primary resin

S: secondary resin

T1 to T6: temperature (temperature)

V1-V3: line speed of optical fiber

Detailed Description

(description of embodiments of the present disclosure)

First, embodiments of the present disclosure are described below.

A method for manufacturing an optical fiber according to one embodiment of the present disclosure is a method for manufacturing an optical fiber in which

(1) A method for manufacturing an optical fiber having a resin-coated layer formed around a glass fiber by introducing a glass fiber formed by drawing while heating and melting an optical fiber base material into a resin coating apparatus filled with a resin, coating the resin around the glass fiber, and then curing the resin coated around the glass fiber by subjecting the resin to a curing treatment, the method comprising:

According to the above method, by making the viscosity of the resin in the resin coating device in which the wire speed is rising higher than the viscosity of the resin in the resin coating device in which the wire speed is stable at the time of drawing, the amount of drag of the resin by the glass fiber entering the resin coating device in which the wire speed is rising can be reduced. As a result, the coating diameter of the optical fiber in the linear velocity increasing step becomes small, so that the amount of resin used from the start of the drawing step to the end of the steady drawing step can be reduced.

(2) The temperature of the resin supplied into the resin coating device in the line speed increasing step may be lower than the temperature of the resin supplied into the resin coating device in the stable drawing step.

(3) The temperature of the resin coating device in the wire speed increasing step may be lower than the temperature of the resin coating device in the stable drawing step.

According to these methods, the viscosity of the resin in the line speed rise can be made higher than that in the stable drawing.

(4) The temperature of the glass fiber entering the resin coating apparatus in the wire speed increasing step may be higher than the temperature of the glass fiber entering the resin coating apparatus in the stable drawing step.

According to the above method, the amount of the resin drawn by the glass fiber during the increase in the linear velocity can be further reduced, and further reduction in the amount of the resin used can be expected.

(5) The viscosity of the resin in the resin coating device in the line speed increasing step may be 1pa·s or more.

By setting the viscosity of the resin at a constant value or more during the increase of the linear velocity, the amount of the resin used can be significantly reduced.

Another mode of the present disclosure relates to a method of manufacturing an optical fiber, in which

(6) A method for manufacturing an optical fiber having a resin-coated layer formed around a glass fiber by introducing a glass fiber formed by drawing while heating and melting an optical fiber base material into a resin coating apparatus filled with a resin, coating the resin around the glass fiber, and then curing the resin coated around the glass fiber by subjecting the resin to a curing treatment, the method comprising:

the temperature of the glass fiber entering the resin coating apparatus in the wire speed increasing step is higher than the temperature of the glass fiber entering the resin coating apparatus in the stable drawing step.

According to the above method, the amount of pulling of the glass fiber into the resin during the rise in the wire speed can be reduced by making the temperature of the glass fiber entering the resin coating device higher than the temperature of the glass fiber entering the resin coating device during the stable drawing. As a result, the coating diameter of the optical fiber in the linear velocity increasing step becomes small, so that the amount of resin used from the start of the drawing step to the end of the steady drawing step can be reduced.

(details of embodiments of the present disclosure)

Specific examples of the method for manufacturing an optical fiber according to the embodiment of the present disclosure will be described below with reference to the drawings.

It is intended that the disclosure not be limited to these examples, but rather by the claims, and that it is intended to include all variations within the meaning and scope equivalent to the claims.

Fig. 1 is a schematic configuration diagram showing an example of an optical fiber manufacturing apparatus 1 according to an embodiment of the present disclosure.

As shown in fig. 1, an optical fiber manufacturing apparatus 1 includes: a drawing furnace 10, a forced cooling device 5, a resin coating device 12, a resin supply device 13, a resin curing device 14, a guide roller 15, a pickup portion 16, a winding reel 17, a drawing control device 18, and a temperature control device 19. The optical fiber manufacturing apparatus 1 of the present embodiment is a double-coating type manufacturing apparatus that continuously coats and cures a primary resin and a secondary resin at one time.

The drawing furnace 10 is configured to heat and melt the lower end portion of the optical fiber preform G by a heater. The drawing furnace 10 is an example of a heating furnace. The lower end portion of the optical fiber preform G heated in the drawing furnace 10 is drawn finely downward, and drawn by the tension of the pickup 16, thereby forming the glass fiber G1.

The forced cooling device 11 cools the drawn glass fiber G1. The forced cooling apparatus 11 has a sufficient length along the traveling line to sufficiently cool the glass fiber G1. The forced cooling device 11 includes an air supply port (not shown) for cooling the glass fibers G1,

the glass fiber G1 is cooled by introducing a cooling gas from the gas supply port. As the cooling gas, helium is used, for example. By adjusting the flow rate of the cooling gas introduced into the forced cooling apparatus 11, the temperature of the glass fiber G1 passing through the forced cooling apparatus 11 can be controlled.

The resin coating device 12 is disposed downstream of the forced cooling device 11 in the traveling direction of the glass fiber G1 (the direction of arrow a in fig. 1). The resin coating device 12 is configured to coat the periphery of the drawn and forced-cooled glass fiber G1 with a resin.

The resin coating device 12 includes a first die 12A disposed on the upstream side in the traveling direction of the glass fiber G1 and a second die 12B disposed on the downstream side. The first die 12A coats the primary resin around the glass fiber G1. The second mold 12B coats the secondary resin around the primary resin coated around the glass fiber G1. As the primary resin for the inner layer (for the primary coating layer), an ultraviolet curable resin which is cured to be in a relatively soft state is used. As the secondary resin for the outer layer (for the secondary coating layer), an ultraviolet curable resin which is cured to be in a relatively hard state is used. Depending on the type of the optical fiber, the resin coating layer may be formed as a single layer. In addition, a thermosetting resin is sometimes used as the coating resin.

The resin supply device 13 is configured to: the primary resin P is supplied to the first mold 12A via the pipe 20A, and the secondary resin S is supplied to the second mold 12B via the pipe 20B.

The piping 20A and the piping 20B are provided with

piping heating devices

21A and 21B, respectively, so that the temperature in the piping 20A of the primary resin P flowing into the first mold 12A and the temperature in the piping 20B of the secondary resin S flowing into the second 5 mold 12B can be controlled to desired temperatures. The resin supply device 13 includes: a first supply portion 13A for supplying the primary resin P to the first mold 12A, and a second supply portion 13B for supplying the secondary resin S to the second mold 12B. When the resin is supplied from the first supply portion 13A and the second supply portion 13B,

the resin supply device 13 applies pressure to the primary resin P and the secondary resin S, respectively, and supplies them to the resin coating device 12.

The resin curing device 14 is disposed downstream of the resin coating device 12 in the traveling direction of the glass fiber G1. The resin curing device 14 is configured to cure the primary resin P and the secondary resin S applied to the glass fiber G1 by the resin application device 12. The resin curing device 14 is, for example, an ultraviolet irradiation device, and cures the resin by irradiation with ultraviolet rays. The optical fiber G2 formed by curing the resin is wound on the winding reel 17 via the guide roller 15 and the pickup 16.

The wire drawing control device 18 is configured to: the drawing conditions (heating temperature of the heater, conveyance speed of the optical fiber preform G, pickup speed of the pickup section 16, etc.) are controlled so that the drawing speed (hereinafter, referred to as a linear speed) of the optical fiber G2 becomes a desired speed. Specifically, the wire drawing control device 18 controls the wire drawing conditions such that the wire speed increases after the wire is drawn and reaches a constant wire speed after the wire is drawn stably. The drawing control device 18 outputs speed information to the temperature control device 19.

The temperature control device 19 is configured to control the temperatures of the first mold 12A and the second mold 12B to respective predetermined temperatures. Specifically, the temperature control device 19 controls the temperatures of the first die 12A and the second die 12B by, for example, allowing a fluid to flow through the

pipes

19A and 19B inside the resin coating device 12 and around the first die 12A and the second die 12B. By controlling the temperatures of the first mold 12A and the second mold 12B, the temperature of the primary resin P in the first mold 12A and the temperature of the secondary resin S in the second mold 12B are controlled.

The temperature control device 19 acquires line speed information from the drawing control device 18, and controls the temperatures of the first die 12A and the second die 12B to a predetermined temperature according to the line speed. Specifically, the temperature control device 19 sets the temperatures of the first die 12A and the second die 12B lower than the temperatures of the first die 12A and the second die 12B at the time of steady drawing during the period in which the linear speed is low; in the course of the wire speed rise, the temperatures of the first die 12A and the second die 12B are raised to the set temperatures of the first die 12A and the second die 12B at the time of stable wire drawing.

The temperature control device 19 may be configured to control the temperature of the primary resin P supplied into the first mold 12A and the temperature of the secondary resin S supplied into the second mold 12B to predetermined temperatures. Specifically, the temperature control device 19 may control the temperature of the primary resin P in the first supply portion 13A and the temperature of the secondary resin S in the second supply portion 13B of the resin supply device 13, respectively. The temperature of the primary resin P supplied into the first mold 12A and the temperature of the secondary resin S supplied into the second mold 12B are controlled by adjusting the temperature of the primary resin P in the first supply portion 13A and the temperature of the secondary resin S in the second supply portion 13B. Alternatively, the temperature control device 19 may acquire line speed information from the drawing control device 18, and control the temperatures of the primary resin P and the secondary resin S by adjusting the temperature of the pipe heating device 21A provided in the pipe 20A connecting between the first supply unit 13A and the first die 12A and the temperature of the pipe heating device 21B provided in the pipe 20B connecting between the second supply unit 13B and the second die 12B, respectively, according to the line speed.

In this case, the temperature control device 19 may acquire the wire speed information from the wire drawing control device 18, and may control the resin temperature of at least one of the resin supply device 13 (the first supply portion 13A and the second supply portion 13B) and the

pipes

20A and 20B to a predetermined temperature according to the wire speed. Specifically, during the period when the linear velocity is low, the resin temperature in the resin supply device 13 and the

pipes

20A and 20B is made lower than the resin temperature in the resin supply device 13 and the

pipes

20A and 20B at the time of stable drawing; the resin temperature is raised to the resin temperature at the time of stable drawing while the wire speed is rising.

Next, a method for manufacturing an optical fiber by using the optical fiber manufacturing apparatus 1 will be described.

First, the lower end portion of the optical fiber preform G is heated in the drawing furnace 10, and a part (glass gob) thereof is dropped by its own weight, and the glass gob hanging down from the drawing furnace 10 is received in an appropriate container. Further, the diameter of the suspended rod-shaped glass is reduced so as to be a fibrous glass, and the glass is suspended from the guide roller 15 and the pickup unit 16 by passing through the forced cooling device 11, the resin application device 12, and the resin curing device 14, and is guided to the winding reel 17 (drawing step). Then, one end of the glass is wound around the winding reel 17, and then drawn while gradually increasing the wire speed, thereby forming the glass fiber G1 (wire speed increasing step). After the wire speed reaches the wire speed for stable wire drawing, the wire speed is raised, and wire drawing is performed while maintaining the wire speed (stable wire speed) (stable wire drawing step).

An optical fiber formed by stable drawing was used as a product (obtained product). For example, the wire speed at the time of stable drawing is 2000 m/min or more. The glass fiber G1 formed by drawing is passed through the forced cooling device 11 and cooled to a predetermined temperature, and then passed through the resin coating device 12, and two layers of resins (primary resin P and secondary resin S) are coated on the outer periphery thereof at once.

Fig. 2 is a graph showing a relationship between a line speed and temperatures of the first die 12A and the second die 12B. Fig. 3 is a graph showing the relationship among the line speed, the temperature of the primary resin P supplied to the first die 12A, and the temperature of the secondary resin S supplied to the second die 12B. In fig. 2 and 3, the vertical axis represents temperature (c) or linear velocity (m/min), and the horizontal axis represents elapsed time from the start of production.

As shown in fig. 2, in the steady drawing step, the wire speed is controlled to be V1, and the temperatures of the first die 12A and the second die 12B are controlled to be T1. In the wire speed increasing step from the drawing to the stable drawing, the temperature control device 19 performs temperature control of the first die 12A and the second die 12B at the start of the wire speed increase so that the temperatures of the first die 12A and the second die 12B (temperature T2 in fig. 2) are lower than the temperature T1 at the time of the stable drawing. The temperature control device 19 controls the temperatures of the first mold 12A and the second mold 12B so that the temperatures of the first mold 12A and the second mold 12B rise to a temperature T1 while the linear velocity is rising. That is, after the linear velocity reaches the predetermined linear velocity (linear velocity V2 in fig. 2), the temperature control device 19 starts to raise the temperatures of the first die 12A and the second die 12B until the temperature is raised to the temperature T1. For example, the difference between the temperature T1 in the steady drawing step and the temperature T2 in the wire speed increasing step is 5 ℃ to 40 ℃, preferably 5 ℃ to 30 ℃. The relationship between the linear velocity V1 in the steady drawing step and the linear velocity V2 in the linear velocity increasing step is V2 < V1, preferably V2 < v1×0.9, and more preferably V2 < v1×0.8.

The temperature rise of the first mold 12A and the second mold 12B from the temperature T2 to the temperature T1 may be one or more than one. In particular, when the difference between the temperature T2 and the temperature T1 is large, the increase is preferably divided into a plurality of times.

In the above example, the temperature control as shown in fig. 2 was performed for both the first mold 12A and the second mold 12B, but the present invention is not limited to this example. For example, in the wire speed increasing step from the drawing to the steady drawing, only one of the first die 12A and the second die 12B may be subjected to temperature control for making the temperature (temperature T2 in fig. 2) lower than the temperature T1 at the time of steady drawing at the start of the wire speed increase, and temperature control for making the temperature rise to the temperature T1 may be performed on the way of the wire speed increase.

In addition, as shown in fig. 3, in the steady drawing step, the temperature of the primary resin P supplied to the first die 12A is controlled to be a temperature T3, and the temperature of the secondary resin S supplied to the second die 12B is controlled to be a temperature T4. In the wire speed increasing step from the drawing to the steady drawing, the temperature control device 19 performs temperature control of the primary resin P at the start of the wire speed increase so that the temperature of the primary resin P supplied to the first die 12A, that is, the temperature of at least one of the first supply portion 13A of the resin supply device 13 and the piping 20A (temperature T5 in fig. 3) is lower than the temperature T3 at the time of the steady drawing. Further, the temperature control device 19 performs temperature control of the secondary resin S at the start of the linear velocity increase so that the temperature of the secondary resin S supplied to the second die 12B, that is, the temperature of at least one of the second supply portion 13B of the resin supply device 13 and the pipe 20B (temperature T6 in fig. 3) is lower than the temperature T4 at the time of stable drawing. In addition, the temperature control device 19 performs temperature control of the primary resin P after the linear velocity reaches a predetermined linear velocity (linear velocity V3 in fig. 3) in the middle of the linear velocity increase so that the temperature of the primary resin P supplied to the first die 12A increases to a temperature T3. Similarly, the temperature control device 19 performs control of the temperature of the secondary resin S so that the temperature of the secondary resin S supplied to the second die 12B increases to a temperature T4 after the linear velocity reaches a predetermined linear velocity (linear velocity V3 in fig. 3) in the middle of the linear velocity increase. That is, the temperature control device 19 starts to raise the temperatures of the primary resin P and the secondary resin S until the temperatures rise to the temperature T3 and the temperature T4 after the linear velocity reaches the predetermined linear velocity (linear velocity V3 in fig. 3). For example, the difference between the temperature T3 and the temperature T5 of the primary resin P is 5 ℃ to 30 ℃, preferably 5 ℃ to 20 ℃. The difference between the temperature T4 and the temperature T6 of the secondary resin S is 5 ℃ to 30 ℃, preferably 5 ℃ to 20 ℃. Since the resin materials used for the primary resin P and the secondary resin S are different, the predetermined temperature at the time of stable drawing is different between the temperature T3 and the temperature T4. In addition, the predetermined linear velocity (linear velocity V3 in fig. 3) may also be different in the primary resin P and the secondary resin S.

In the above example, the temperature control as shown in fig. 3 was performed on both the primary resin P supplied to the first mold 12A and the secondary resin S supplied to the second mold 12B, but the present invention is not limited to this example. For example, the temperature control shown in fig. 3 may be applied only to any one of the primary resin P supplied to the first mold 12A and the secondary resin S supplied to the second mold 12B. That is, in the wire speed increasing step from the drawing to the steady drawing, the temperature of the primary resin P may be controlled so that the temperature of the primary resin P supplied to the first die 12A, that is, the temperature of at least one of the first supply portion 13A of the resin supply device 13 and the pipe 20A (temperature T5 in fig. 3) is lower than the temperature T3 in the steady drawing, at the start of the wire speed increase, and the temperature of the primary resin P may be controlled so that the temperature of the primary resin P supplied to the first die 12A is increased to the temperature T3 after the wire speed reaches a predetermined wire speed (wire speed V3 in fig. 3) in the middle of the wire speed increase. Alternatively, only in the wire speed increasing step from the drawing to the stable drawing, the temperature of the secondary resin S may be controlled at the start of the wire speed increase so that the temperature of the secondary resin S supplied to the second die 12B, that is, at least one of the second supply portion 13B of the resin supply device 13 and the pipe 20B (temperature T6 in fig. 3) is lower than the temperature T4 at the time of the stable drawing, and the temperature of the secondary resin S may be controlled after the wire speed reaches a predetermined wire speed (wire speed V3 in fig. 3) during the wire speed increase so that the temperature of the secondary resin S supplied to the second die 12B increases to the temperature T4.

By this, the temperature T2 of the first die 12A and the second die 12B in the wire speed raising step is lower than the temperature T1 of the first die 12A and the second die 12B in the steady drawing step, so that the viscosities of the primary resin P and the secondary resin S at the time of coating around the glass fiber G1 in the resin coating device 12 in the wire speed raising step are higher than the viscosities of the primary resin P and the secondary resin S coated around the glass fiber G1 in the resin coating device 12 in the steady drawing step. In the same manner, the temperature T5 of the primary resin P and the temperature T6 of the secondary resin S supplied to the resin coating device 12 in the wire-drawing step are set lower than the temperature T3 of the primary resin P and the temperature T4 of the secondary resin S supplied to the resin coating device 12 in the steady-drawing step, so that the viscosities of the primary resin P and the secondary resin S at the time of coating around the glass fiber G1 in the wire-drawing step are set higher than the viscosities of the primary resin P and the secondary resin S coated around the glass fiber G1 in the steady-drawing step. The viscosities of the primary resin P and the secondary resin S at the time of coating around the glass fiber G1 in the wire speed increasing step are preferably 1pa·s or more, for example. The viscosities of the primary resin P and the secondary resin S in the linear velocity increasing step are more preferably 1.5pa·s or more.

The glass fiber G1 coated with the resin is passed through a resin curing device 14, and the resin is cured to become an optical fiber G2. The optical fiber G2 is wound on the winding reel 17 via the guide roller 15 and the pickup 16. Fig. 4 is a cross-sectional view of an optical fiber 100 manufactured by the optical fiber manufacturing apparatus 1. In the optical fiber 100, a first coating resin layer 102 and a second coating resin layer 103 composed of a primary resin P and a secondary resin S are formed concentrically on the outer periphery of a glass fiber 101 composed of a core layer and a cladding layer. The optical fiber 100 is formed, for example: the diameter D1 of the glass fiber 101 is 124-126 μm, and the diameter D2 of the second resin coating layer 103 is 235-255 μm.

In the present embodiment, in the linear velocity increasing step, the flow rate of the cooling gas introduced into the forced cooling device 11 is controlled so that the temperature of the glass fiber G1 at the time of entering the resin coating device 12 is controlled to a predetermined temperature. The temperature of the glass fiber G1 in the wire speed increasing step is preferably higher than the temperature of the glass fiber G1 in the steady drawing step. Specifically, the temperature of the glass fiber G1 at the time of entering the resin coating apparatus 12 in the wire speed increasing step is controlled to be 60 ℃ to 85 ℃. The temperature of the glass fiber G1 is more preferably 70℃to 85℃and still more preferably 75℃to 80 ℃. When the temperature of the glass fiber G1 in the linear velocity increasing step is too high, the application of the primary resin P and the secondary resin S to the glass fiber G1 becomes unstable, and the resin cannot be pulled appropriately, so that the possibility of breakage of the optical fiber G2 becomes high. Therefore, the temperature of the glass fiber G1 in the line speed increasing step is preferably set to be within a range of 80 ℃ or lower, for example.

Example (example)

The evaluation results of each example of the above-described optical fiber manufacturing method will be described below with reference to fig. 5.

Fig. 5 (a) is a diagram showing temperature control of the resin coating apparatus 12 (the first die 12A and the second die 12B) in examples 1 to 4. In fig. 5 (a), the vertical axis represents temperature (°c), and the horizontal axis represents elapsed time from the start of production.

In the examples shown in fig. 5 (a) to (d), the control of the linear velocity of the optical fiber is set to be the same as the control of the linear velocity shown in fig. 2. As shown in fig. 5 (a), in example 1, the temperature of the resin coating apparatus 12 was constant from the time of the rise in the wire speed to the time of the stable drawing. In contrast, in example 2, at the start of the line speed increase, the temperature of the resin coating device 12 was set to a temperature lower than the set temperature at the time of steady drawing (a temperature of the same level as that of example 1), and at the time of the line speed increase reaching a predetermined time point, the temperature of the resin coating device 12 was started to be increased to the set temperature at the time of steady drawing. In examples 3 and 4, the temperature of the resin coating device 12 was set to a temperature lower than the set temperature at the time of steady drawing at the start of the line speed increase, and the temperature of the resin coating device 12 was started to be increased to the set temperature at the time of steady drawing at the time of the predetermined time point during the line speed increase, as in example 2. In the cases of examples 3 and 4, the time at which the temperature of the resin coating apparatus 12 was raised was set to be the time point later than the case of the ratio 2. In example 4, the temperature of the glass fiber G2 cooled by the forced cooling device 11 was set to be higher than those of examples 1 to 3.

Fig. 5 (b) is a diagram showing the change in the outer diameter of the optical fiber G2 when the temperature of the resin coating apparatus 12 is controlled as in examples 1 to 4. In fig. 5 (b), the vertical axis represents the coating diameter (μm) of the optical fiber G2, and the horizontal axis represents the elapsed time from the start of production. As shown in fig. 4, the coating diameter (μm) of the optical fiber G2 is the outer diameter of the optical fiber G2 (100) in a state in which the first coating resin layer 102 and the second coating resin layer 103 composed of the primary resin P and the secondary resin S are concentrically formed on the glass fiber G1 (101).

As shown in fig. 5 (b), immediately after the start of the increase in the linear velocity, the linear velocity of the optical fiber G2 is low, and the amounts of the primary resin P and the secondary resin S pulled by the glass fiber G1 passing through the resin coating device 12 become large, so that the coating diameter of the optical fiber G2 also becomes large. Then, as the linear velocity increases, the amounts of the primary resin P and the secondary resin S pulled by the glass fiber G1 gradually decrease, and the coating diameter of the optical fiber G2 also gradually becomes smaller. Then, at the time of stable drawing (at the time of stable linear velocity), the amounts of the primary resin P and the secondary resin S pulled by the glass fiber G1 are stabilized by a predetermined amount, and the coating diameters of all the optical fibers G2 in examples 1 to 4 are fixed. As shown in fig. 5 (a), when the temperature control of the resin coating apparatus 12 was different from that in examples 1 to 4, it was confirmed that: since the temperature of the resin coating device 12 at the start of the increase in the linear velocity of examples 2 to 4 was lower than that of example 1, the coating diameter of the optical fiber G2 in the process of increasing the linear velocity was reduced. In examples 3 and 4 where the temperature rise start time of the resin coating device 12 was late in proportion to 2, it was confirmed that the coating diameter of the optical fiber G2 was smaller in proportion to 2 throughout the linear velocity rise step. The coating diameter of example 4 was kept smaller than that of example 3 at the time of stable drawing.

Fig. 5 (c) is a graph showing the amount of the primary resin used in examples 1 to 4, and fig. 5 (d) is a graph showing the amount of the secondary resin used in examples 1 to 4. In fig. 5 (c) and (d), the vertical axis represents the amount (kg) of the primary resin P and the secondary resin S used, and the horizontal axis represents the elapsed time from the start of production.

As shown in fig. 5 (c), although the amounts of the primary resins P used were not significantly different in examples 1, 2 and 3, it was confirmed that the amount of the primary resin P used in example 4 was significantly reduced as compared with example 1. As shown in fig. 5 (d), the amount of the secondary resin S used was significantly reduced in examples 2 to 4 compared with example 1. That is, it was confirmed that the temperature of the resin coating device 12 was set to a temperature lower than the set temperature at the time of stable drawing in the wire speed raising step so that the temperatures of the primary resin P and the secondary resin S in the wire speed raising step were lower than the temperatures of the primary resin P and the secondary resin S in the stable drawing step, thereby having an effect of reducing the resin usage amount. In particular, it can be confirmed that: in example 4 in which the temperatures of the primary resin P and the secondary resin S were controlled while the temperatures of the glass fibers G1 were further controlled, the total amount of the primary resin layer P and the secondary resin layer S was reduced by about 25% as compared with the total amount of the primary resin P and the secondary resin S in example 1.

As described above, according to the method of manufacturing an optical fiber of the present embodiment, the temperature of the resin coating device 12 is set to be lower than the set temperature at the time of stable drawing in the wire speed increasing step so that the temperatures of the primary resin P and the secondary resin S in the wire speed increasing step are lower than the temperatures of the primary resin P and the secondary resin S in the stable drawing step. Thus, the viscosities of the primary resin P and the secondary resin S in the wire speed increasing step are higher than those of the primary resin P and the secondary resin S in the steady drawing step. By increasing the viscosity of the primary resin P and the secondary resin S, the amount of the glass fiber G1 pulled by the primary resin P and the secondary resin S at the time of the increase in the linear velocity decreases, and the primary resin P and the secondary resin S applied around the glass fiber G1 at the time of the increase in the linear velocity decrease. That is, the coating diameter of the optical fiber G2 in the line speed increasing step is reduced. As a result, the amounts of the primary resin P and the secondary resin S used in the step of discarding the product without forming the product, that is, in the line speed rise can be reduced.

In addition to the coating diameter of the optical fiber G2, in the final stable drawing step, it is sometimes necessary to satisfy a desired criterion for the concentricity (unbiased thickness) of the first coating resin layer 102 and the second coating resin layer 103, which are composed of the primary resin P and the secondary resin S, with respect to the glass fiber G1 (101). Therefore, the viscosity of the resin is controlled so as to reduce the amount of the resin used, and the linear velocity (linear velocity increasing step) is set to be smaller than that in the steady drawing step.

In addition, the temperature of the primary resin P and the secondary resin S supplied into the resin coating device 12 in the wire speed increasing step is preferably lower than the temperature of the primary resin P and the secondary resin S supplied into the resin coating device 12 in the steady wire drawing step. By this method, the viscosities of the primary resin P and the secondary resin S at the rising line speed can be made higher than those at the line speed at the time of stable drawing, and the amounts of the primary resin P and the secondary resin S used per 1 optical fiber base material can be reduced.

Further, the temperature of the glass fiber G1 entering the resin coating apparatus 12 in the wire speed increasing step is more preferably higher than the temperature of the glass fiber G1 entering the resin coating apparatus 12 in the steady drawing step. According to this method, the amount of the glass fiber G1 drawn by the primary resin P and the secondary resin S during the increase in the linear velocity can be further reduced, and further reduction in the amount of the resin used can be expected.

The present disclosure has been described in detail with reference to specific embodiments, but it will be apparent to one skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the disclosure. The number, position, shape, and the like of the constituent members described above are not limited to the above-described embodiments, and may be changed to the number, position, shape, and the like preferable for implementing the present disclosure.

In the above embodiment, the amount of resin used in the wire speed increasing step can be reduced by making the temperature of the resin in the resin coating device different between the wire speed increasing step and the steady drawing step, but the present invention is not limited to this example. For example, by increasing the temperature of the glass fiber G1 entering the resin coating apparatus 12 in the line speed increasing step while keeping the temperature of the resin constant, the amount of pulling of the glass fiber G1 against the resin during the line speed increase can be reduced. That is, the cooling temperature of the glass fiber G1 in the linear velocity increasing step is set to be equal to or higher than a predetermined temperature by adjusting the flow rate of the cooling gas introduced into the forced cooling device 11. Thus, only the viscosity of the resin around the glass fiber G1 in the first mold 12A and the second mold 12B is reduced, and thus the amount of pulling of the glass fiber G1 against the resin is reduced. As a result, the coating diameter of the optical fiber G2 in the line speed increasing step becomes small, and the resin usage amount can be reduced.

The optical fiber manufacturing apparatus 1 is a double-coating type manufacturing apparatus, but is not limited thereto. The optical fiber manufacturing apparatus 1 may be a tandem coating type manufacturing apparatus that performs resin coating and curing layer by layer. In the tandem coating type manufacturing apparatus, the first die 12A and the second die 12B are disposed separately. In the case of the tandem coating type, the resin curing device 14 is composed of a first curing portion disposed downstream of the first die 12A and upstream of the second die 12B, and a second curing portion disposed downstream of the second die 12B. The first curing section cures the primary resin applied through the first die 12A. The second curing section cures the secondary resin applied through the second die 12B. In this case, during the period when the line speed is low, the temperature of the primary resin P in the first die 12A and the temperature of the secondary resin S in the second die 12B are lowered than at the time of stable drawing, so that the viscosities of the primary resin P and the secondary resin S are increased, and the same effects as those of the above embodiment can be obtained.

In the above embodiment, the temperature control device 19 controls the resin temperature in the first die 12A and the second die 12B by flowing the fluid inside the resin coating device 12, but is not limited thereto. For example, the temperature control device 19 may control the resin temperature by providing a heating device, a cooling device, and controlling the operations of the heating device, the cooling device in the resin coating device 12.

In the above embodiment, the temperature control device 19 obtains the line speed information by the wire drawing control device 18, but is not limited thereto. For example, a measuring device for measuring the linear velocity of the optical fiber G2 may be provided, and linear velocity information may be obtained from the measuring device.

Claims

1. A method for manufacturing an optical fiber, in which a glass fiber formed by drawing an optical fiber base material while heating and melting the same is introduced into a resin coating device filled with a resin, the resin is coated around the glass fiber, and then the resin coated around the glass fiber is subjected to a curing treatment to cure the resin, thereby manufacturing an optical fiber in which a resin-coated layer is formed around the glass fiber, the method comprising:

performing an extraction step for picking up the optical fiber by a pickup device;

2. The method for manufacturing an optical fiber according to claim 1, wherein

The temperature of the resin supplied into the resin coating device in the wire speed increasing step is lower than the temperature of the resin supplied into the resin coating device in the stable drawing step.

3. The method for manufacturing an optical fiber according to claim 1 or claim 2, wherein

The temperature of the resin coating device in the wire speed increasing step is lower than the temperature of the resin coating device in the stable drawing step.

4. A method of manufacturing an optical fiber according to any one of claims 1 to 3, wherein

5. The method for manufacturing an optical fiber according to any one of claims 1 to 4, wherein

The viscosity of the resin in the resin coating device in the line speed increasing step is 1pa·s or more.

6. A method for manufacturing an optical fiber, in which a glass fiber formed by drawing an optical fiber base material while heating and melting the same is introduced into a resin coating device filled with a resin, the resin is coated around the glass fiber, and then the resin coated around the glass fiber is subjected to a curing treatment to cure the resin, thereby manufacturing an optical fiber in which a resin-coated layer is formed around the glass fiber, the method comprising: