JP2023012631A - Method for manufacturing optical fiber - Google Patents

Abstract

To suppress breakage of an optical fiber.SOLUTION: A method for manufacturing an optical fiber includes the steps of: forming a glass fiber; forming a resin coating layer so as to cover the outer periphery of the glass fiber; curing the resin coating layer using a predetermined curing device; conveying the optical fiber obtained by curing the resin coating layer by a plurality of guide rollers and a capstan; and winding the optical fiber by a bobbin. In the step of forming the resin coating layer, a first resin coating layer and a second resin coating layer as resin coating layers are formed in this order from a central axis side to an outer peripheral side of the glass fiber. Between the step of forming the resin coating layer and the step of winding the optical fiber, a density of particles having a size of 1/4 times or more the thickness of the second resin coating layer in the atmosphere is set to 1,060 pieces/m3 or less.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD The present disclosure relates to methods for manufacturing optical fibers.

An optical fiber is known in which the outer periphery of a glass fiber is covered with a resin coating layer (for example, Patent Document 1).

JP 2012-6797 A

An object of the present disclosure is to suppress disconnection of optical fibers.

According to one aspect of the present disclosure,
forming a glass fiber;
forming a resin coating layer so as to cover the outer periphery of the glass fiber;
A step of curing the resin coating layer using a predetermined curing device;
a step of conveying the optical fiber having the resin coating layer cured by a plurality of guide rollers and a capstan;
winding the optical fiber with a bobbin;
has
In the step of forming the resin coating layer,
forming a first resin coating layer and a second resin coating layer as the resin coating layers in this order from the central axis side to the outer peripheral side of the glass fiber;
Between the step of forming the resin coating layer and the step of winding the optical fiber,
A method for manufacturing an optical fiber is provided in which the density of particles having a size of 1/4 or more times the thickness of the second resin coating layer in the atmosphere is 1060 particles/m ³ or less.

According to the present disclosure, disconnection of an optical fiber can be suppressed.

1 is a schematic cross-sectional view showing an optical fiber according to one embodiment of the present disclosure; FIG. FIG. 2 is a schematic configuration diagram showing an optical fiber manufacturing apparatus according to one embodiment of the present disclosure. FIG. 3 is a diagram showing the disconnection frequency with respect to the thickness of the second resin coating layer. FIG. 4 is a diagram showing the disconnection frequency with respect to the target particle density.

[Description of Embodiments of the Present Disclosure]
<Knowledge acquired by the inventors, etc.>
First, the findings obtained by the inventors will be described.

In recent years, in order to mount a plurality of optical fibers at high density as an optical cable, it is required to reduce the outer diameter of the optical fibers. Specifically, some recent optical fibers have an outer diameter of 200 μm or less.

In the process of manufacturing an optical fiber having such a small diameter, the optical fiber is more likely to break than a conventional optical fiber having an outer diameter. If the optical fiber is broken during the manufacturing process, the manufacturing efficiency of the optical fiber is lowered. Therefore, there has been a demand for an unprecedented manufacturing method.

In order to solve the above-mentioned problem, attention was focused on particles existing in the atmosphere during the manufacturing process, and studies were carried out.

When particles present in the atmosphere adhere to the optical fiber during the manufacturing process, the particles intervene between the optical fiber and a guide roller or capstan that conveys the optical fiber. At this time, since the optical fiber is conveyed under a predetermined tension, particles adhering to the optical fiber are locally pressed against the resin coating layer. Therefore, local stress may be applied to the glass fiber. In such cases, damage such as cracks may occur in the glass fiber. As a result, the optical fiber may break due to damage to the glass fiber.

As a result of intensive studies on the particles, the inventors have found that the relationship between the specific particles in the atmosphere and the thickness of the second resin coating layer affects the disconnection frequency of the optical fiber.

The present disclosure is based on the above knowledge discovered by the present disclosure person.

[Details of the embodiment of the present disclosure]
Next, one embodiment of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to these examples, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

<One embodiment of the present disclosure>
(1) Optical Fiber An optical fiber 10 according to an embodiment of the present disclosure will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an optical fiber according to this embodiment.

In the following, the “axial direction” of the glass fiber 100 means the direction along the central axis of the glass fiber 100 and can be rephrased as the longitudinal direction of the glass fiber 100 . Also, the “radial direction” of the glass fiber 100 means the direction perpendicular to the axial direction of the glass fiber 100 , and can be rephrased as the lateral direction of the glass fiber 100 in some cases. Further, the “circumferential direction” of the glass fiber 100 means the direction along the outer periphery of the glass fiber 100 (circumferential direction in FIG. 1). For the optical fiber 10 as well, the same terminology as for the glass fiber 100 can be used.

As shown in FIG. 1, the optical fiber 10 of this embodiment is configured as a linear body in which the outer circumference of the glass fiber 100 is covered with a resin coating layer 200, for example. That is, the optical fiber 10 has, for example, the glass fiber 100 and the resin coating layer 200 in this order from the central axis side of the glass fiber 100 toward the outer peripheral side.

The term "optical fiber 10" used herein includes the optical fiber bare wire before coloring and the optical fiber core wire after coloring. Hereinafter, for example, the optical fiber 10 will be described as an optical fiber bare wire.

[Glass fiber]
The glass fiber 100 is configured, for example, as an optical transmission medium that transmits light introduced into the optical fiber 10 along the axial direction of the optical fiber 10 . Note that the glass fiber 100 is also called, for example, a “bare optical fiber”. The glass fiber 100 has, for example, silica (SiO ₂ ) glass as a base material (main component), and has a core 120 and a clad 140 .

[Resin coating layer]
The resin coating layer 200 is provided, for example, so as to cover the outer periphery of the glass fiber 100 and is configured to protect the glass fiber 100 .

In this embodiment, the resin coating layer 200 has, for example, a first resin coating layer (primary resin coating layer) 220 and a second resin coating layer (secondary resin coating layer) 240 .

The first resin coating layer 220 is provided, for example, so as to cover the outer circumference of the clad 140 of the glass fiber 100 and is in contact with the outer circumference of the clad 140 . The second resin coating layer 240 is provided, for example, so as to cover the outer periphery of the first resin coating layer 220 and is in contact with the outer periphery of the first resin coating layer 220 .

The first resin coating layer 220 and the second resin coating layer 240 are, for example, configured as a cured product obtained by curing an ultraviolet-curable resin composition by ultraviolet irradiation. Examples of the base resin in the UV-curable resin composition include urethane acrylate.

In this embodiment, the Young's modulus of the second resin coating layer 240 is preferably 900 MPa or more, for example. When the Young's modulus of the second resin coating layer 240 is less than 900 MPa, when particles present in the atmosphere during the manufacturing process adhere to the optical fiber 10, contact with guide rollers 552 of the conveying unit 550 described later causes The particles are likely to be locally pushed into the second resin coating layer 240 . Therefore, excessive stress may be applied to the glass fiber 100 . As a result, the optical fiber 10 may easily break. In contrast, in the present embodiment, by setting the Young's modulus of the second resin coating layer 240 to 900 MPa or more, that is, by making the second resin coating layer 240 hard, particles present in the atmosphere during the manufacturing process are Even if the particles adhere to the optical fiber 10 , local pushing of the particles into the second resin coating layer 240 can be suppressed. Thereby, application of excessive stress to the glass fiber 100 can be suppressed. As a result, disconnection of the optical fiber 10 can be stably suppressed.

Note that the upper limit of the Young's modulus of the second resin coating layer 240 is not particularly limited. For example, it is preferably 1400 MPa or less.

In addition, it is preferable that the Young's modulus of the first resin coating layer 220 is, for example, 0.15 MPa or more and 1.2 MPa or less.

In this embodiment, the optical fiber 10 is configured to have a small diameter, for example. Specifically, the outer diameter of the resin coating layer 200 described above (that is, the outer diameter of the second resin coating layer 240) is, for example, 190 μm or less. Thereby, a plurality of optical fibers 10 can be mounted at high density as an optical cable.

It is preferable that the outer diameter of the resin coating layer 200 is, for example, 160 μm or more.

From the relationship between the outer diameter of the first resin coating layer 220 and the outer diameter of the second resin coating layer 240 described above, the thickness of the second resin coating layer 240 is preferably, for example, 10 μm or more and 25 μm or less.

(2) Optical Fiber Manufacturing Apparatus Next, an optical fiber manufacturing apparatus 50 according to this embodiment will be described with reference to FIG. FIG. 2 is a schematic configuration diagram showing an optical fiber manufacturing apparatus according to this embodiment.

As shown in FIG. 2, the optical fiber manufacturing apparatus 50 of this embodiment includes, for example, a drawing furnace 510, a fiber position measuring section 522, a cooling device 523, an outer diameter measuring section 524, and a resin coating device 530. , a curing device 540 , a conveying section 550 , a bobbin 560 , a control section 590 , a clean booth 620 and an air conditioning system 640 . Device members other than the control unit 590, the clean booth 620, and the air conditioning system 640 are provided in this order.

Hereinafter, in each device member of the optical fiber manufacturing device 50, the side closer to the gripping mechanism 512 is called "upstream", and the side closer to the bobbin 560 is called "downstream".

Draw furnace 510 is configured to form glass fiber 100 .

By heating the inside of the furnace core tube 514 and stretching the softened glass, the glass fiber 100 having a small diameter is formed.

The fiber position measuring section 522 is configured to measure the horizontal position of the glass fiber 100 .

Cooling device 523 is configured to cool glass fiber 100 formed in drawing furnace 510 .

The outer diameter measuring section 524 is configured to measure the outer diameter of the glass fiber 100 before resin coating.

The resin coating device 530 is configured to form the resin coating layer 200 so as to cover the outer periphery of the glass fiber 100 . The resin coating layer 200 has a die for applying an ultraviolet curable resin composition to the outer periphery of the glass fiber 100 while inserting the glass fiber 100 .

In this embodiment, the resin coating device 530 has two dies for forming the first resin coating layer 220 and the second resin coating layer 240 in this order from the central axis side of the glass fiber 100 toward the outer peripheral side. have.

The curing device 540 is configured to irradiate the resin coating layer 200 with ultraviolet rays to cure the resin coating layer 200 .

The transport section 550 is configured to transport the optical fiber 10 with the resin coating layer 200 cured. Specifically, the transport section 550 has, for example, a plurality of guide rollers 552 and 556 and a capstan 554 . The direct roller 552a, which is one of the plurality of guide rollers 552, is positioned directly below the curing device 540, for example. The capstan 554 is provided, for example, downstream of the roller 552a directly below, and is configured to convey (pull) the optical fiber 10 with a predetermined tension while gripping the optical fiber 10 between the belt and the roller. there is Screening rollers 552 c , 552 d and 552 e among the plurality of guide rollers 552 are provided downstream of the capstan 554 and configured to apply screening tension to the optical fiber 10 together with the capstan 554 . The guide roller 556 is provided on the downstream side of the screening roller 552e and configured to adjust the tension of the optical fiber 10 by moving up and down according to the variation in the tension of the optical fiber 10 .

The bobbin 560 is provided, for example, downstream of the guide roller 556 and configured to wind the optical fiber 10 thereon.

The controller 590 is, for example, connected to each part of the optical fiber manufacturing apparatus 50 and configured to control them. The control unit 590 is configured as, for example, a computer.

Here, in the present embodiment, the environment from the resin coating device 530 to the bobbin 560 is maintained so as to satisfy the target particle density requirements in the atmosphere, which will be described later.

Specifically, the optical fiber manufacturing apparatus 50 has a clean booth 620 and an air conditioning system 640, for example.

The clean booth 620 is provided, for example, so as to surround the area from the resin coating device 530 to the bobbin 560 . The clean booth 620 has, for example, a resin plate or resin film that partitions an area from the resin coating device 530 to the bobbin 560 and other areas.

The air conditioning system 640 is configured, for example, to suck the air in the clean booth 620 , remove particles through a filter, and supply the cleaned air to the clean booth 620 . Examples of filters in the air conditioning system 640 include HEPA filters (High Efficiency Particulate Air Filters) and ULPA filters (Ultra Low Penetration Air Filters). Also, the air conditioning system 640 is configured, for example, to maintain the pressure inside the clean booth 620 to be more positive than the pressure in the area outside the clean booth 620 .

Furthermore, in this embodiment, at least one of the plurality of guide rollers 552, capstans 554, and bobbins 560 is configured to be able to remove static electricity so as to satisfy the requirements for the amount of static electricity in the wound optical fiber 10, which will be described later. It is

Specifically, each of the plurality of guide rollers 552, capstans 554 and bobbins 560 is provided with ionizers 580 (590a to 580h), for example. The ionizer 580 is configured, for example, to blow ionized air onto the object to neutralize the object.

(3) Method for Manufacturing Optical Fiber Next, a method for manufacturing the optical fiber 10 according to the present embodiment will be described with reference to FIG. Hereinafter, the step is abbreviated as "S".

The method for manufacturing the optical fiber 10 of the present embodiment includes, for example, a glass fiber forming step (drawing step) S100, a cooling step S200, a resin coating layer forming step S300, a curing step S400, a conveying step S500, and a winding step. and a removing step S600. These steps are continuously performed in this order in the optical fiber manufacturing apparatus 50 . Also, each component of the optical fiber manufacturing apparatus 50 is controlled by the control section 590 .

[S100: Drawing process]
First, the glass base material G is introduced into the furnace core tube 514 of the drawing furnace 510 and the heating element 516 heats the glass base material G in the furnace core tube 514 . After heating the glass preform G, the softened glass is drawn from the lower end of the glass preform G to form a glass fiber 100 having a small diameter.

[S200: Cooling step]
Next, the glass fiber 100 formed in the drawing furnace 510 is introduced into the cooling device 523 and air-cooled.

At this time, the feeding amount of the glass base material and the like are controlled so that the outer diameter of the glass fiber 100 before resin coating measured by the outer diameter measuring unit 524 is constant.

[S300: Resin coating layer forming step]
Next, the resin coating device 530 forms the resin coating layer 200 so as to cover the outer periphery of the glass fiber 100 .

At this time, in this embodiment, as the resin coating layer 200, the first resin coating layer 220 and the second resin coating layer 240 are continuously formed in this order from the central axis side of the glass fiber 100 toward the outer peripheral side. Form.

At this time, in the present embodiment, the outer diameter of the resin coating layer 200 is, for example, 190 μm or less.

[S400: Curing step]
Next, the curing device 540 irradiates the resin coating layer 200 with ultraviolet rays to cure the resin coating layer 200 . At this time, in this embodiment, the first resin coating layer 220 and the second resin coating layer 240 are cured at the same time. By setting the Young's modulus of the second resin coating layer 240 after curing to 900 MPa or more, it is possible to make the resin coating layer 200 less likely to be damaged by particles.

[S500: Conveying step]
Next, the transport section 550 transports the optical fiber 10 with the resin coating layer 200 cured. Specifically, in the conveying section 550, the optical fiber 10 is conveyed under a predetermined tension through a direct roller 552a, a guide roller 552b, a capstan 554, screening rollers 552c, 552d and 552e, and a guide roller 556. FIG.

[S600: winding step]
Next, the bobbin 560 winds the optical fiber 10 .

Here, in the present embodiment, from the resin coating layer forming step S300 to the winding step S600, for example, the size (particle size) of 1/4 or more times the thickness of the second resin coating layer 240 in the atmosphere diameter) is 1060 particles/m ³ or less. Note that the density of the particles is also referred to as "target particle density". In addition, when CF (cubic feet) is used as a unit, the above target particle density is equivalent to 30 particles/CF or less.

In the present embodiment, by setting the target particle density to 1060 particles/m ³ or less, it is possible to reduce the probability that particles having a large size to thickness ratio of the second resin coating layer 240 adhere to the optical fiber 10. can.

Note that the lower limit of the target particle density is not particularly limited because the lower the better.

The target particle density described above depends on, for example, the type of filter in the air conditioning system 640, the number of filters in the air conditioning system 640, the air intake speed of the air conditioning system 640, the clean air supply speed of the air conditioning system 640, the pressure in the clean booth 620, etc. adjust.

Further, in the present embodiment, in the steps from the conveying step S500 to the winding step S600, a plurality of guide rollers are arranged so that the absolute value of the static electricity of the entire optical fiber 10 after being wound onto the bobbin 560 is 6 kV or less. 552, capstan 554 and bobbin 560 are neutralized. By removing static electricity from each part so as to satisfy the above-described requirements for the amount of static electricity, adhesion of particles to the optical fiber 10 due to electrification of the optical fiber 10 can be suppressed.

It should be noted that the “static amount of the entire optical fiber 10 after being wound onto the bobbin 560 ” referred to herein can be rephrased as the amount of static electricity of the entire optical fiber 10 wound onto the bobbin 560 . The reason why the amount of static electricity of the entire optical fiber 10 after winding is specified is that the amount of static electricity of the optical fiber 10 cannot be measured during the process of transporting the optical fiber 10 . As described above, filling the entire amount of static electricity in the wound optical fiber 10 corresponds to suppressing the accumulation of static electricity in the optical fiber 10 during the process of transporting the optical fiber 10 .

The lower limit of the amount of static electricity in the wound optical fiber 10 is not particularly limited because the lower the better.

As a specific static elimination method, for example, ionized air having a polarity opposite to the polarity with which the optical fiber 10 is charged is applied to at least one of the plurality of guide rollers 552, capstans 554, and bobbins 560 to each ionizer. Spray by 580. It is preferable that the location where the ionized air is blown is a location on the object with which the optical fiber 10 comes into contact. Static electricity on the optical fiber 10 can be canceled by such a method. As a result, the static electricity of the optical fiber 10 can be stably removed.

Further, in this embodiment, for example, at least one of the plurality of guide rollers 552 and the capstan 554 located upstream of the bobbin 560 is preferably neutralized by the ionizer 580 . Since the optical fiber 10 is carried on the upstream side of the bobbin 560, the optical fiber 10 tends to approach particles in the atmosphere. Therefore, by positively removing static electricity on the upstream side of the bobbin 560 as described above, even during a period when the optical fiber 10 may approach particles in the atmosphere, particles do not reach the optical fiber 10 . Adhesion can be stably suppressed.

Further, in the present embodiment, it is more preferable, for example, to neutralize the capstan 554 with an ionizer 580c. At the capstan 554, the optical fiber 10 is easily charged because the optical fiber 10 rubs between the belt and the roller. Therefore, by positively removing the charge from the capstan 554 as described above, the charging of the optical fiber 10 can be stably suppressed. As a result, adhesion of particles to the optical fiber 10 can be stably suppressed.

In this embodiment, it is most preferable to neutralize all of the guide rollers 552 , the capstans 554 and the bobbins 560 by the ionizers 580 . As a result, charging of the optical fiber 10 during transportation of the optical fiber 10 can be reliably suppressed, and adhesion of particles to the optical fiber 10 can be reliably suppressed.

As described above, the optical fiber 10 of the present embodiment is manufactured.

(4) Effects According to the Present Embodiment According to the present embodiment, one or more of the following effects can be obtained.

(a) Between the resin coating layer forming step S300 and the winding step S600 of the present embodiment, the density of particles having a size of 1/4 or more times the thickness of the second resin coating layer 240 in the atmosphere is 1060/ ^m3 or less.

When the target particle density exceeds 1060 particles/m ³ , the probability that particles with a large size-to-thickness ratio of the second resin coating layer 240 adhere to the optical fiber 10 increases. When such large particles adhere to the optical fiber 10 , the particles are likely to be locally pushed into the second resin coating layer 240 due to contact with the guide rollers 552 of the conveying section 550 . Therefore, excessive stress may be applied to the glass fiber 100 . As a result, the optical fiber 10 may easily break.

On the other hand, in the present embodiment, by setting the target particle density to 1060 particles/m ³ or less, the probability that particles having a large size-to-thickness ratio of the second resin coating layer 240 adhere to the optical fiber 10 is reduced. can be lowered. By suppressing adhesion of particles, it is possible to suppress local pushing of particles into the second resin coating layer 240 . Thereby, application of excessive stress to the glass fiber 100 can be suppressed. As a result, disconnection of the optical fiber 10 can be stably suppressed.

By reducing the disconnection frequency of the glass fiber 100 in this manner, it is possible to suppress a decrease in the manufacturing efficiency of the optical fiber 10 .

(b) In the resin coating layer forming step S300 of the present embodiment, the Young's modulus of the second resin coating layer 240 is set to 900 MPa or more. That is, by hardening the second resin coating layer 240, even if particles present in the atmosphere adhere to the optical fiber 10 during the manufacturing process, the particles are prevented from being locally pushed into the second resin coating layer 240. can do. Thereby, application of excessive stress to the glass fiber 100 can be suppressed. As a result, disconnection of the optical fiber 10 can be stably suppressed.

(c) In the steps from the conveying step S500 to the winding step S600 of the present embodiment, a plurality of guide rollers are arranged so that the absolute value of the static electricity of the entire optical fiber 10 after being wound onto the bobbin 560 is 6 kV or less. 552, capstan 554 and bobbin 560 are neutralized.

Here, in conveying the optical fiber 10 by the plurality of guide rollers 552 and the capstan 554 and winding the optical fiber 10 by the bobbin 560 (collectively referred to as a conveying process of the optical fiber 10), the optical fiber 10 contacts each part. Therefore, the optical fiber 10 is easily charged.

The fact that the absolute value of the amount of static electricity in the entire optical fiber 10 after winding is less than 6 kV corresponds to the accumulation of static electricity in the optical fiber 10 during the transportation process of the optical fiber 10 described above. As described above, if the optical fiber 10 is electrically charged during the transportation process of the optical fiber 10 , particles tend to adhere to the optical fiber 10 due to static electricity during the transportation process of the optical fiber 10 . When particles adhere to the optical fiber 10 , excessive stress may be applied to the glass fiber 100 due to the pushing of the particles into the resin coating layer 200 as described above. As a result, the optical fiber 10 may easily break.

On the other hand, reducing the amount of static electricity in the entire optical fiber 10 after winding as in the present embodiment corresponds to suppressing the accumulation of static electricity in the optical fiber 10 during the transportation process of the optical fiber 10. . By suppressing the accumulation of static electricity in the optical fiber 10, adhesion of particles to the optical fiber 10 due to the charging of the optical fiber 10 can be suppressed. As a result, application of excessive stress to the glass fiber 100 due to the pushing of particles into the resin coating layer 200 can be suppressed. As a result, disconnection of the optical fiber 10 can be stably suppressed.

(d) In this embodiment, the outer diameter of the resin coating layer 200 of the optical fiber 10 is 190 μm or less. When manufacturing the optical fiber 10 with such a small diameter, as in the examples described later, adhesion of particles having a size of 1/4 or more times the thickness of the second resin coating layer 240 causes Breakage of the optical fiber 10 is likely to occur. Therefore, the manufacturing method described above is particularly effective for manufacturing the optical fiber 10 in which the outer diameter of the resin coating layer 200 is 190 μm or less.

<Other embodiments of the present disclosure>
Although the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments, and can be variously modified without departing from the scope of the present disclosure.

In the above-described embodiment, the optical fiber 10 is illustrated and described as an optical fiber bare wire before being colored, but as described above, the optical fiber 10 may be an optical fiber core wire after being colored. . That is, the optical fiber 10 may have a colored layer covering the outer circumference of the resin coating layer 200 .

In the above-described embodiment, the case where the resin coating layer 200 is composed of two layers has been described, but the present invention is not limited to this case. The resin coating layer 200 may be composed of only one layer, or may be composed of three or more layers.

In the above embodiment, the case where all of the following (i), (ii) and (iii) are implemented has been described, but the present invention is not limited to this case.
(i) Between the resin coating layer forming step S300 and the winding step S600, the density of particles having a size equal to or larger than 1/4 times the thickness of the second resin coating layer 240 in the atmosphere is 1060. /m ³ or less.
(ii) Young's modulus of the second resin coating layer 240 is set to 900 MPa or more.
(iii) In the steps from the conveying step S500 to the winding step S600, the plurality of guide rollers 552 and capstans are arranged so that the absolute value of the static electricity of the entire optical fiber 10 after being wound on the bobbin 560 is 6 kV or less. At least one of 554 and bobbin 560 is neutralized.
By implementing at least (i), the above effect can be obtained to a considerable extent. However, performing at least one of (ii) and (iii) in addition to the above (i) makes it possible to stably obtain the above effect.

In the above-described embodiment, the clean booth 620 partitions the area from the resin coating device 530 to the bobbin 560 and the other area, and the air conditioning system 640 reduces the target particle density in the clean booth 620. Although explained, it is not limited to this case. The target particle density may be reduced by an air conditioning system in the entire clean room in which the optical fiber manufacturing apparatus 50 is installed.

In the above-described embodiment, from the resin coating layer forming step S300 to the winding step S600, the density of particles having a size of 1/4 or more times the thickness of the second resin coating layer 240 in the atmosphere is , 1060/m ³ or less has been described, but the present invention is not limited to this case. Instead of adjusting the target particle density, the thickness of the second resin coating layer 240 may be adjusted. That is, the thickness of the second resin coating layer 240 may be, for example, four times or more the size of the particles present in the atmosphere in the largest number (for example, more than 30 particles/CF). However, since the thickness of the second resin coating layer 240 is determined by the specifications of the optical fiber 10, it is preferable to adjust the target particle density as described above.

Next, examples according to the present disclosure will be described. These examples are examples of the present disclosure, and the present disclosure is not limited by these examples.

(1) Production of Optical Fiber An optical fiber of each sample was produced under the following conditions.

When preparing each sample, the target particle density in the atmosphere was adjusted by changing the opening/closing condition of the clean booth.

[Common conditions]
Outer diameter of glass fiber: 125 μm
Outer diameter of optical fiber (outer diameter of second resin coating layer): 180 μm
Number of resin coating layers: 2 Layers Manufacturing equipment: Configuration shown in FIG.

[Experiment 1]
Thickness of the second resin coating layer: 5 to 30 μm (peripheral diameter of the second resin coating layer is fixed at 180 μm)
Particle size (particle diameter): 3.75 μm or 5 μm
Particle density: 30/CF
Young's modulus of the second resin coating layer: 900 MPa
Elimination of static electricity by the ionizer on the transport section and bobbins: None

[Experiment 2]
Thickness of the second resin coating layer: 20 μm
Target particle density: 0 to 50 / CF
Young's modulus of the second resin coating layer: 900 MPa
Elimination of static electricity by the ionizer on the transport section and bobbins: None

[Experiment 3]
Thickness of the second resin coating layer: 20 μm
Target particle density: 30 / CF
Young's modulus of the second resin coating layer: 800 to 2000 MPa
Elimination of static electricity by an ionizer in the transport section and bobbins: Yes Amount of static electricity in the optical fiber after winding (absolute value): 6 kV

[Experiment 4]
Thickness of the second resin coating layer: 20 μm
Target particle density: 30 / CF
Young's modulus of the second resin coating layer: 900 MPa
Elimination of static electricity by an ionizer in the conveying part and bobbin: Yes or no Static electricity amount (absolute value) of optical fiber after winding: 0.3 to 30 kV
(Sample B4-2 was not neutralized.)

(2) Evaluation [target particle density]
The target particle density in the clean booth surrounding the area from the resin coating device to the bobbin was measured with a particle counter (Met One Model 237B). According to the particle counter, it is possible to detect the size and the number of particles contained when 1 CF of air is sucked.

[Amount of static electricity]
The absolute value of the amount of static electricity in the optical fiber wound around the bobbin was measured with an electrostatic amount measuring instrument.

[Disconnection frequency measurement]
In the process of fabricating the optical fiber of each sample described above, the number of disconnections of the optical fiber was measured. In each sample, the number of disconnections per 1000 km was obtained as "disconnection frequency (times/Mm)". As a result, when the disconnection frequency was less than 5 times/Mm, it was evaluated as "good", and when the disconnection frequency was 5 times/Mm or more, it was evaluated as "bad".

(3) Results [Experiment 1]
The results of Experiment 1 regarding the dependence of the thickness of the second resin coating layer will be described with reference to FIG.

As shown in FIG. 3, in manufacturing an optical fiber in an atmosphere in which particles having a predetermined size are present, as the thickness of the second resin coating layer decreases from a predetermined threshold value, the disconnection frequency of the optical fiber gradually increases. was increasing. In addition, from a comparison of particles having different sizes, the threshold thickness of the second resin coating layer at which the frequency of disconnection of the optical fiber is 5 times/Mm or more is about 4 times the particle size, and is proportional to the particle size. I found out.

[Experiment 2]
With reference to FIG. 4, the results of Experiment 2 regarding the dependency of target particle density will be described.

As shown in FIG. 4, as the density of particles having a size of 1/4 or more times the thickness of the second resin coating layer in the atmosphere (target particle density) increases from a predetermined threshold value, the optical fiber disconnection frequency gradually increased. It was found that the threshold of the target particle density at which the optical fiber disconnection frequency is 5 times/Mm or more is 30 particles/CF.

From the results of Experiments 1 and 2, from the resin coating layer forming step to the winding step, the density of particles having a size of 1/4 or more times the thickness of the second resin coating layer in the atmosphere It was confirmed that the disconnection frequency of optical fibers can be reduced by setting the number to 30/CF or less.

[Experiment 3]
The results of Experiment 3 regarding the dependence of the Young's modulus of the second resin coating layer are described with reference to Table 1 below.

In sample B3-1, in which the Young's modulus of the second resin coating layer is less than 900 MPa, the optical fiber disconnection frequency is 5 times/Mm or more.

In sample B3-1, when particles adhered to the optical fiber, the particles were easily pushed into the second resin coating layer. As a result, it is considered that the optical fiber of sample B3-1 was more likely to break.

On the other hand, in the samples A3-1 to A3-4 in which the Young's modulus of the second resin coating layer was 900 MPa or more, the disconnection frequency of the optical fiber was less than 5 times/Mm. Further, in samples A3-1 to A3-4, there was a tendency that the higher the Young's modulus of the second resin coating layer, the lower the disconnection frequency of the optical fiber.

In samples A3-1 to A3-4, by setting the Young's modulus of the second resin coating layer to 900 MPa or more, even if particles adhere to the optical fiber, the particles are locally pushed into the second resin coating layer. could be suppressed. As a result, it was confirmed that disconnection of the optical fiber 10 could be stably suppressed in the samples A3-1 to A3-4.

[Experiment 4]
With reference to Table 2 below, the results of Experiment 4 regarding the dependence of the amount of static electricity are illustrated.

In samples B4-1 and B4-2, in which the absolute value of the static electricity amount of the optical fiber after winding was over 6 kV, the optical fiber disconnection frequency was 5 times/Mm or more. Further, in samples B4-1 and B4-2, the frequency of disconnection of the optical fiber tended to increase as the absolute value of the amount of static electricity in the wound optical fiber increased.

In samples B4-1 and B4-2, static electricity was accumulated in the optical fibers during the transportation of the optical fibers. For this reason, particles tend to adhere to the optical fiber. As a result, in samples B4-1 and B4-2, the optical fiber 10 was likely to break.

On the other hand, in samples A4-1 to A4-3 in which the absolute value of the static electricity amount of the optical fiber after winding was set to 6 kV or less, the disconnection frequency of the optical fiber was less than 5 times/Mm. Further, in the samples A4-1 to A4-3, the disconnection frequency of the optical fiber tended to decrease as the absolute value of the static electricity amount of the optical fiber after winding decreased.

In the samples A4-1 to A4-3, it was possible to suppress the accumulation of static electricity in the optical fiber during the transportation process of the optical fiber. This made it possible to suppress adhesion of particles to the optical fiber. As a result, it was confirmed that in samples A4-1 to A4-3, disconnection of optical fibers could be stably suppressed.

10 Optical fiber 50 Optical fiber manufacturing apparatus 100 Glass fiber 120 Core 140 Cladding 200 Resin coating layer 220 First resin coating layer 240 Second resin coating layer 430 Curing device 510 Drawing furnace 512 Gripping mechanism 514 Furnace core tube 516 Heating element 518 Gas supply Part 522 Fiber position measuring part 523 Cooling device 524 Outer diameter measuring part 530 Resin coating device 540 Hardening device 550 Conveying part 552 Guide roller 552a Directly below roller 552b Guide rollers 552c, 552d, 552e Screening roller 554 Capstan 555 Vibration suppression part 556 Guide roller 560 bobbins 580, 580a to 580h ionizer 590 control unit 620 clean booth 640 air conditioning system

Claims (3)

forming a glass fiber;
forming a resin coating layer so as to cover the outer periphery of the glass fiber;
A step of curing the resin coating layer using a predetermined curing device;
a step of conveying the optical fiber having the resin coating layer cured by a plurality of guide rollers and a capstan;
winding the optical fiber with a bobbin;
has
In the step of forming the resin coating layer,
forming a first resin coating layer and a second resin coating layer as the resin coating layers in this order from the central axis side to the outer peripheral side of the glass fiber;
Between the step of forming the resin coating layer and the step of winding the optical fiber,
A method for manufacturing an optical fiber, wherein the density of particles having a size of 1/4 or more times the thickness of the second resin coating layer in the atmosphere is 1060 particles/m ³ or less. In the step of forming the resin coating layer,
2. The method of manufacturing an optical fiber according to claim 1, wherein the Young's modulus of the second resin coating layer is 900 MPa or more. In the steps from the step of conveying the optical fiber to the step of winding the optical fiber,
2. At least one of the plurality of guide rollers, the capstan, and the bobbin is neutralized so that the absolute value of the amount of static electricity in the entire optical fiber after being wound on the bobbin is 6 kV or less. 3. A method for manufacturing an optical fiber according to claim 2.

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