JP2020105054A - Method for manufacturing optical fiber, and apparatus for manufacturing optical fiber - Google Patents

Abstract

To provide a method for manufacturing an optical fiber, which can suppress a decrease in a mechanical strength of the optical fiber while suppressing a deviation in thickness of a resin coating layer; and an apparatus for manufacturing the optical fiber.SOLUTION: The method for manufacturing an optical fiber 1 comprises: a first resin application step P4 of inserting an optical fiber bare wire 1N into a first accommodation chamber 44 of which the upper side is open and in which an inner resin 61 is stored, from above the first accommodation chamber, and extracting the bare wire from a first die opening 55H; a second resin application step P5 of inserting the optical fiber bare wire 1N into a second accommodation chamber 45 which is filled with the inner resin 61 at a predetermined pressure, from the first die opening 55H, and extracting the bare wire from a second die opening 56H; and a third resin application step P6 of inserting the optical fiber bare wire 1N into a third accommodation chamber 46 which is filled with an outer resin 62 at a predetermined pressure, from the second die opening 56H, and extracting the bare wire from a third die opening 57H.SELECTED DRAWING: Figure 3

Description

The present invention relates to an optical fiber manufacturing method and an optical fiber manufacturing apparatus, and particularly to an optical fiber manufacturing method and an optical fiber manufacturing apparatus having a resin coating layer.

Conventionally, there is known an optical fiber in which the outer periphery of the core is surrounded by the clad and the outer peripheral surface of the clad is covered with a resin coating layer composed of a plurality of layers. A method of making an optical fiber is disclosed.

Patent Document 1 below uses a die main body having a first accommodation chamber having an upper opening and a lower die opening and a second accommodation chamber having an upper insertion opening and a lower die opening, and an inner resin Disclosed is a method of manufacturing an optical fiber having a resin coating layer including a layer and an outer resin layer. In the method of manufacturing an optical fiber using such a die body, the inner resin that serves as the inner resin layer is stored in the first housing chamber, and the outer resin that serves as the outer resin layer is stored in the second housing chamber at a predetermined pressure. It is filled. In this method of manufacturing an optical fiber, an optical fiber bare wire having no resin coating layer is inserted into the first housing chamber from above, extracted from the die port, and the uncured inner resin is applied to the outer peripheral surface of the bare optical fiber. To do. In addition, the bare optical fiber coated with the uncured inner resin is inserted into the second accommodation chamber through the insertion port and pulled out from the die opening to form the outer peripheral surface of the bare optical fiber coated with the uncured inner resin. Apply the uncured outer resin to. The uncured inner resin and outer resin thus applied are cured to form the inner resin layer and the outer resin layer.

Further, in Patent Document 1 below, the upper side of the first storage chamber is closed and an insertion port for inserting a bare optical fiber is provided above the first storage chamber, and the inner side is an inner resin layer. A method of manufacturing an optical fiber using a die main body different from the above-mentioned die main body in that the resin is filled into the first storage chamber at a predetermined pressure is disclosed.

International Publication No. 99/32415

When the die body whose upper side of the first storage chamber is open is used as in the one manufacturing method described in Patent Document 1, the uncured inner resin is stored in the first storage chamber whose upper side is open. Therefore, convection occurs in the inner resin along with the movement of the bare optical fiber that passes through the first storage chamber, and a meniscus that is recessed in a concave shape around the bare optical fiber is formed on the liquid surface of the inner resin that is in contact with gas. This convection may become unstable due to the viscosity of the inner resin, the extraction speed of the bare optical fiber, and the like. When the convection becomes unstable, the pressure of the uncured inner resin that is poured from the die opening together with the bare optical fiber fluctuates, and the thickness of the inner resin that is applied becomes uneven and the thickness of the inner resin layer becomes uneven. May occur, resulting in uneven thickness of the resin coating layer. For example, in an optical fiber having a double-clad structure in which the inner resin layer is an outer clad, when the inner resin layer becomes thin, excitation light may leak from a portion where the inner resin layer becomes thin. Therefore, there is a demand for suppressing uneven thickness of the resin coating layer.

On the other hand, when the die body having the insertion opening formed above the first storage chamber is used as in the other manufacturing method described in Patent Document 1, the inner resin in the uncured state has a predetermined pressure in the first storage chamber. Filled with. For this reason, formation of the above meniscus on the inner resin is suppressed, and unstable flow of the inner resin is suppressed. Therefore, in such a manufacturing method, fluctuations in the pressure of the uncured inner resin that is poured out from the die opening together with the bare optical fiber are suppressed, and unevenness in the thickness of the inner resin layer is suppressed. By so doing, it is possible to prevent the thickness of the resin coating layer from becoming uneven.

By the way, in the method of manufacturing an optical fiber, when the optical fiber preform is drawn to form an optical fiber bare wire in which the outer periphery of the core is surrounded by a clad, the optical fiber preform is rotated to produce the optical fiber bare wire. May give a permanent twist to. Therefore, in the optical fiber manufacturing method of Patent Document 1, for example, it is conceivable to use a bare optical fiber formed by drawing an optical fiber preform while rotating it. In this case, a centrifugal force due to the rotation of the optical fiber preform may cause the bare optical fiber to shake in a direction perpendicular to the longitudinal direction. When the uncured inner resin is filled in the first housing chamber with a predetermined pressure as described above, the outer peripheral surface of the bare optical fiber contacts the edge of the insertion port of the first housing chamber in the die body, and the optical fiber There is a possibility that the outer peripheral surface of the bare wire may be scratched and the mechanical strength of the optical fiber may be reduced.

Therefore, the present invention provides an optical fiber manufacturing method and an optical fiber manufacturing apparatus capable of suppressing a decrease in mechanical strength of an optical fiber while suppressing unevenness in the thickness of a resin coating layer. With the goal.

To achieve the above object, the method for producing an optical fiber of the present invention comprises a core, a clad that surrounds the outer peripheral surface of the core, an inner resin layer that covers the outer peripheral surface of the clad, and an outer peripheral surface of the inner resin layer. A method of manufacturing an optical fiber, comprising: a resin coating layer including an outer resin layer to be coated, wherein an inner resin which is open at the top and has a first die opening at the bottom and which is a part of the inner resin layer is stored. The optical fiber bare wire having the core and the clad is inserted into the first accommodating chamber from above the first accommodating chamber and pulled out from the first die port, and the inner resin is provided on the outer peripheral surface of the optical fiber bare wire. A first resin applying step of applying the inner resin that becomes a part of a layer, and an inner side that has a first insertion opening in the upper part and a second die opening in the lower part and becomes another part of the inner resin layer The bare optical fiber coated with the inner resin, which is a part of the inner resin layer, is inserted from the first insertion opening into the second storage chamber filled with resin at a predetermined pressure, and the second die opening is inserted. A second resin coating that is extracted from the inner resin layer and is coated with the inner resin that is a part of the inner resin layer on the outer peripheral surface of the bare optical fiber that is coated with the inner resin that is a part of the inner resin layer. And a third accommodation chamber having a second insertion opening on the upper side and a third die opening on the lower side and being filled with the outer resin serving as the outer resin layer at a predetermined pressure, the other inner resin layer The bare optical fiber coated with a part of the inner resin is inserted from the second insertion port and extracted from the third die port, and the inner resin that is another part of the inner resin layer is coated. And a third resin applying step of applying the outer resin to the outer peripheral surface of the bare optical fiber.

In this method for manufacturing an optical fiber, the uncured inner resin to be the inner resin layer is applied to the outer peripheral surface of the bare optical fiber by the first resin applying step and the second resin applying step, and is not applied by the third resin applying step. An uncured outer resin to be an outer resin layer is applied to the outer peripheral surface of the bare optical fiber coated with the hardened inner resin. The uncured inner resin and outer resin thus applied are cured to form the inner resin layer and the outer resin layer. In this method of manufacturing an optical fiber, the bare optical fiber is passed through the first storage chamber, the second storage chamber, and the third storage chamber in this order, and the upper side of the first storage chamber is open. Therefore, as compared with the case where the uncured inner resin is filled in the first storage chamber as in the manufacturing method described in Patent Document 1, the runout of the bare optical fiber in the direction perpendicular to the longitudinal direction Even if it occurs, it is possible to prevent the outer peripheral surface of the bare optical fiber from coming into contact with the member in which the first housing chamber is formed, and to prevent the outer peripheral surface of the bare optical fiber from being scratched. It is possible to suppress the decrease. Further, in this method of manufacturing an optical fiber, in the second resin applying step, the second accommodation chamber filled with a predetermined pressure of the inner resin, which is another part of the inner resin layer, becomes a part of the inner resin layer. Pass the bare optical fiber coated with the inner resin. Then, the inner resin serving as another part of the inner resin layer is applied to the outer peripheral surface of the bare optical fiber coated with the inner resin serving as a part of the inner resin layer. Since the second accommodation chamber is filled with the inner resin at a predetermined pressure, the uncured state that is poured out from the second die opening together with the bare optical fiber coated with the inner resin that becomes a part of the inner resin layer The fluctuation of the pressure of the inner resin is suppressed. Therefore, even if there is a deviation in the thickness of the inner resin applied to the outer peripheral surface of the bare optical fiber in the first resin applying step, the inner resin is applied so as to level this deviation in the second resin applying step. Thus, it is possible to prevent the thickness of the inner resin layer from being uneven. Further, in the third resin applying step, the outer circumference of the bare optical fiber coated with the inner resin is passed by passing the bare optical fiber coated with the inner resin through the third housing chamber filled with the outer resin at a predetermined pressure. Apply outer resin to the surface. Therefore, unevenness in the thickness of the outer resin layer is suppressed. As described above, in this optical fiber manufacturing method, it is possible to prevent the thickness of the inner resin layer and the outer resin layer in the resin coating layer from being uneven, and to suppress the thickness of the resin coating layer from being uneven.

In addition, a tubular guide member that surrounds the bare optical fiber is disposed apart from the outer peripheral surface of the bare optical fiber in at least the inner resin housed in the first housing chamber, and the guide member is The inner resin may be allowed to flow into a region inside the guide member.

By doing so, the convection generated in the inner resin stored in the first storage chamber can be formed in the region closer to the bare optical fiber than the guide member. Therefore, as compared with the case where the guide member is not arranged, the convection can be stabilized by narrowing the region where convection occurs in the inner resin and reducing the meniscus recessed in a concave shape. Therefore, it is possible to prevent the thickness of the inner resin applied to the outer peripheral surface of the bare optical fiber from being uneven in the first resin applying step.

Further, the guide member may be arranged before the inner resin is stored in the first storage chamber.

By doing so, the guide member can be arranged more easily than when the guide member is arranged after the inner resin is stored in the first storage chamber.

Further, when the guide member is arranged in the first storage chamber, the side surface of the guide member is formed with a communicating portion that communicates an outer region and an inner region of the guide member in the inner resin. Also good.

By doing so, as compared with the case where the communication portion is not formed on the side surface of the guide member, the inner resin located in the outer region of the guide member can easily flow into the inner region of the guide member, Convection in the inner resin stored in the first storage chamber can be made more stable. Therefore, it is possible to further prevent the thickness of the inner resin applied to the outer peripheral surface of the bare optical fiber from being unbalanced in the first resin applying step.

The resin forming the inner resin layer may be a resin having a refractive index lower than that of the clad.

By doing so, it is possible to manufacture an optical fiber having a double clad structure in which the clad of the bare optical fiber is the inner clad and the inner resin layer is the outer clad.

The optical fiber manufacturing method may further include a drawing step for forming the bare optical fiber by drawing the optical fiber preform while rotating it about the central axis of the optical fiber preform. good.

By doing so, a permanent twist can be imparted to the bare optical fiber. For example, in an optical fiber for amplification with a double-clad structure in which the clad of the bare optical fiber is the inner cladding and the inner resin layer is the outer cladding, the skew is caused by the permanent twist of the bare optical fiber. It is possible to further suppress light and make it easier for light propagating through the inner cladding to enter the core. Therefore, the absorption efficiency of the pumping light in the amplification optical fiber having the double clad structure can be increased. When the optical fiber preform is drawn while rotating it about the central axis of the optical fiber preform, the bare optical fiber tends to be swayed in a direction perpendicular to the longitudinal direction. However, according to the above optical fiber manufacturing method, it is possible to prevent the mechanical strength of the optical fiber from being lowered even when the bare optical fiber is deflected in the direction perpendicular to the longitudinal direction. Therefore, this method of manufacturing an optical fiber is particularly useful when the optical fiber preform is drawn around while rotating the optical fiber preform around the central axis of the optical fiber preform to form a bare optical fiber. ..

Further, the pressure of the outside resin with which the third storage chamber is filled may be smaller than the pressure of the inside resin with which the second storage chamber is filled.

Further, the first die port of the first storage chamber may also serve as the first insertion port of the second storage chamber.

In this manufacturing method, the bare optical fiber is applied to the inner resin which is a part of the inner resin layer by passing through the first die opening, and is inserted into the second housing chamber. Therefore, even when the bare optical fiber is shaken in the direction perpendicular to the longitudinal direction, compared with the case where the first die opening of the first storage chamber does not also serve as the first insertion opening of the second storage chamber. It is possible to prevent the inner resin applied to the bare optical fiber from coming into contact with the edge of the first insertion opening of the second storage chamber. Therefore, as compared with the case where the first die port does not also serve as the first insertion port of the second storage chamber, even if the runaway of the bare optical fiber occurs in the direction perpendicular to the longitudinal direction, the bare optical fiber will It is possible to further suppress the deviation of the thickness of the applied inner resin.

Further, the second die port of the second storage chamber may also serve as the second insertion port of the third storage chamber.

By doing so, the bare optical fiber is passed through the second die opening to be coated with the inner resin which is another part of the inner resin layer, and is inserted into the third housing chamber. Therefore, even if the bare optical fiber is shaken in the direction perpendicular to the longitudinal direction, compared with the case where the second die opening of the second storage chamber does not also serve as the second insertion opening of the third storage chamber. It is possible to prevent the inner resin applied to the bare optical fiber from coming into contact with the edge of the second insertion opening of the third storage chamber. Therefore, compared with the case where the second die port does not also serve as the second insertion port of the third storage chamber, even if the bare optical fiber is deflected in the direction perpendicular to the longitudinal direction, the bare optical fiber is It is possible to further suppress the deviation of the thickness of the applied inner resin.

Further, in the above-described method for manufacturing an optical fiber, the outer resin is applied to a fourth housing chamber that has a third insertion opening on the upper side and a fourth die opening on the lower side and is filled with a predetermined resin at a predetermined pressure. A fourth step of inserting the exposed bare optical fiber from the third insertion opening and pulling it out from the fourth die opening, and applying the predetermined resin to the outer peripheral surface of the bare optical fiber coated with the outer resin. A resin coating step may be further provided.

By doing so, an optical fiber having a resin coating layer including three resin layers can be manufactured.

The optical fiber manufacturing apparatus of the present invention includes a core, a clad that surrounds the outer peripheral surface of the core, an inner resin layer that covers the outer peripheral surface of the clad, and an outer resin layer that covers the outer peripheral surface of the inner resin layer. An optical fiber manufacturing apparatus having a resin coating layer including: a first housing chamber in which an upper side is opened and a lower side has a first die opening, and an inner resin which is a part of the inner side resin layer is stored. A second housing chamber having a first insertion opening above and a second die opening below and being filled with the inner resin which is another part of the inner resin layer at a predetermined pressure; A die main body having a second insertion opening, a third die opening below, and a third accommodation chamber filled with an outer resin serving as the outer resin layer at a predetermined pressure; Is passed through so that an optical fiber bare wire having the core and the clad can pass through from above to the first die opening, and the second accommodation chamber has the optical fiber bare wire passing through the first accommodation chamber. Is passed through the first insertion opening to the second die opening, and the bare optical fiber that has passed through the second accommodation room is inserted into the third accommodation room from the second insertion opening. It is characterized by being passed through the die opening.

In this optical fiber manufacturing apparatus, the bare optical fiber is passed through the first storage chamber, the second storage chamber, and the third storage chamber in this order, and the upper side of the first storage chamber is open. Therefore, as described above, even if the optical fiber bare wire is shaken in the direction perpendicular to the longitudinal direction, the outer peripheral surface of the bare optical fiber comes into contact with the die body and becomes It is possible to prevent the optical fiber from being damaged and to prevent the mechanical strength of the optical fiber from being lowered. Further, in this optical fiber manufacturing apparatus, the bare optical fiber coated with the inner resin which is a part of the inner resin layer is filled with the inner resin which is another part of the inner resin layer at a predetermined pressure. 2 Pass through the storage room. Therefore, as described above, even if there is a deviation in the thickness of the inner resin that is a part of the inner resin layer applied to the outer peripheral surface of the bare optical fiber, the inner resin layer should be leveled to equalize the deviation. It is possible to apply an inner resin that becomes another part of the inner resin layer, and to suppress unevenness in the thickness of the inner resin layer. Further, in this optical fiber manufacturing apparatus, since the bare optical fiber coated with the inner resin passes through the third storage chamber filled with the outer resin at a predetermined pressure, the thickness of the outer resin layer is increased as described above. Bias is suppressed from occurring. In this manner, the optical fiber manufacturing apparatus can suppress the decrease in the mechanical strength of the optical fiber while suppressing the occurrence of the uneven thickness of the resin coating layer.

The optical fiber manufacturing apparatus further includes a tubular guide member that surrounds the bare optical fiber while being separated from the outer peripheral surface of the bare optical fiber in at least the inner resin stored in the first storage chamber. The guide member may be configured such that the inner resin can flow into a region inside the guide member.

In this optical fiber manufacturing apparatus, as described above, the guide member stabilizes the convection in the inner resin stored in the first storage chamber, and the thickness of the inner resin applied to the outer peripheral surface of the bare optical fiber is uneven. Can be suppressed.

When the optical fiber manufacturing apparatus includes a guide member, a communication portion may be formed on the side surface of the guide member, the communication portion communicating the outer region and the inner region of the guide member in the inner resin. ..

By doing so, as compared with the case where the communication portion is not formed on the side surface of the guide member, the inner resin located in the outer region of the guide member can easily flow into the inner region of the guide member, Convection in the inner resin stored in the first storage chamber can be made more stable. Therefore, it is possible to further prevent the thickness of the inner resin applied to the outer peripheral surface of the bare optical fiber from being uneven.

Further, the first die port of the first storage chamber may also serve as the first insertion port of the second storage chamber.

With such a configuration, the die body can be downsized. Further, in this optical fiber manufacturing apparatus, as described above, the bare optical fiber is coated with the inner resin which is a part of the inner resin layer by passing through the first die opening, and is inserted into the second accommodation chamber. It Therefore, even when the bare optical fiber is shaken in the direction perpendicular to the longitudinal direction, compared with the case where the first die opening of the first storage chamber does not also serve as the first insertion opening of the second storage chamber. It is possible to prevent the inner resin applied to the bare optical fiber from coming into contact with the edge of the first insertion opening of the second storage chamber. Therefore, as compared with the case where the first die port does not also serve as the first insertion port of the second storage chamber, even if the runaway of the bare optical fiber occurs in the direction perpendicular to the longitudinal direction, the bare optical fiber will It is possible to further suppress the deviation of the thickness of the applied inner resin.

Further, the second die port of the second storage chamber may also serve as the second insertion port of the third storage chamber.

With such a configuration, the die body can be downsized. Further, in this optical fiber manufacturing apparatus, as described above, the bare optical fiber is coated with the inner resin, which is another part of the inner resin layer, by passing through the second die opening, and is also applied to the third storage chamber. Is inserted. Therefore, even if the bare optical fiber is deflected in the direction perpendicular to the longitudinal direction, the second die opening of the second storage chamber does not serve as the second insertion opening of the third storage chamber. It is possible to prevent the inner resin applied to the bare optical fiber from coming into contact with the edge of the second insertion opening of the third storage chamber. Therefore, compared with the case where the second die port does not also serve as the second insertion port of the third storage chamber, even if the bare optical fiber is deflected in the direction perpendicular to the longitudinal direction, the bare optical fiber is It is possible to further suppress the deviation of the thickness of the applied inner resin.

As described above, according to the present invention, a method for manufacturing an optical fiber and a method for manufacturing an optical fiber capable of suppressing a decrease in mechanical strength of an optical fiber while suppressing a deviation in the thickness of the resin coating layer A device is provided.

It is a figure which shows the cross section perpendicular|vertical to the longitudinal direction of the optical fiber which concerns on embodiment of this invention. It is a figure which shows schematically the manufacturing apparatus of the optical fiber which concerns on embodiment of this invention. It is a figure which shows schematically the application part shown by FIG. It is a perspective view which shows schematically the guide member shown by FIG. It is a flow chart which shows the manufacturing method of the optical fiber concerning the embodiment of the present invention. It is a figure which shows the cross section perpendicular|vertical to the longitudinal direction of the preform for optical fibers prepared by a preparatory process. It is a figure which shows the guide member which concerns on a modification. It is a figure which shows the application part used in Example 1 similarly to FIG. It is a figure which shows the optical fiber manufactured in Example 1 similarly to FIG. It is a figure which shows the application part used in the comparative example 1 similarly to FIG. It is a figure which shows the application part used in the comparative example 2 similarly to FIG. It is a figure which shows a part of appearance of the bending test of an optical fiber.

Hereinafter, preferred embodiments of an optical fiber manufacturing method and an optical fiber manufacturing apparatus according to the present invention will be described in detail with reference to the drawings. The embodiments illustrated below are for facilitating the understanding of the present invention and are not for limiting the interpretation of the present invention. The present invention can be modified and improved without departing from the spirit thereof. In the drawings referred to below, the dimensions of each member may be shown differently for easy understanding.

FIG. 1 is a view showing a cross section perpendicular to the longitudinal direction of an optical fiber according to an embodiment of the present invention. As shown in FIG. 1, the optical fiber 1 mainly includes an optical fiber bare wire 1N and a resin coating layer 12 including at least two resin layers and coating the outer peripheral surface of the optical fiber bare wire 1N. The bare optical fiber 1N of the present embodiment includes a core 10 and a clad 11 that surrounds the outer peripheral surface of the core 10. The resin coating layer 12 of the present embodiment includes an inner resin layer 13 that covers the outer peripheral surface of the clad 11, an outer resin layer 14 that covers the outer peripheral surface of the inner resin layer 13, and a resin that covers the outer peripheral surface of the outer resin layer 14. The protective layer 15 is formed. In this embodiment, the optical fiber 1 is a double-clad amplification optical fiber in which the clad 11 is an inner clad and the inner resin layer 13 is an outer clad. Therefore, in this embodiment, it can be understood that the clad 11 is the inner clad and the inner resin layer 13 is the outer clad. Therefore, the refractive index of the clad 11 as the inner clad is lower than the refractive index of the core 10, and the refractive index of the inner resin layer 13 as the outer clad is lower than the refractive index of the clad 11 as the inner clad. Further, the core 10 is arranged at the center of the clad 11.

Examples of the material forming the core 10 of the present embodiment include silica glass containing an active element such as ytterbium (Yb) that is excited by excitation light. As the active element, a rare earth element other than ytterbium can be cited. As the rare earth element, in addition to the above ytterbium, thulium (Tm), cerium (Ce), neodymium (Nd), europium (Eu), erbium (Er), etc. Are listed. Further, as the active element, bismuth (Bi) and the like can be mentioned in addition to the rare earth element. This active element generally has a property as a dopant for increasing the refractive index of the core 10. In addition to active elements, germanium (Ge), phosphorous (P), aluminum (Al), titanium (Ti), chlorine (Cl), boron (boron ( A dopant such as B) or fluorine (F) may be added. Further, to the material forming the core 10, an element that lowers the refractive index such as fluorine (F) or boron (B) may be added in order to adjust the refractive index.

In the present embodiment, the outer circumference of the cladding 11 is a substantially regular heptagon in a cross section perpendicular to the longitudinal direction. That is, the outer shape of the bare optical fiber 1N in the cross section perpendicular to the longitudinal direction is approximately a regular heptagon. As described above, in the present embodiment, since the outer shape of the clad 11 is non-circular, the light propagating through the clad 11 changes the reflection angle on the outer peripheral surface of the clad 11, which is the outer peripheral surface of the bare optical fiber 1N. The reflection may be repeated so that the light propagating through the cladding 11 can be easily incident on the core 10. Therefore, the skew light can be suppressed as compared with the case where the outer shape of the clad 11 is circular. Further, in the present embodiment, the bare optical fiber 1N is twisted about the central axis of the core 10. Therefore, the outer peripheral surface of the non-circular clad 11 is twisted in the longitudinal direction, so that skew light can be further suppressed and light propagating in the clad 11 can be easily incident on the core 10. Therefore, the absorption efficiency of the pumping light in the optical fiber 1 which is the amplification optical fiber having the double clad structure can be increased.

As a material forming the clad 11 as such an inner clad, for example, pure silica glass to which no dopant is added can be cited. An element such as fluorine (F) that lowers the refractive index may be added to the material forming the clad 11.

The inner resin layer 13 as the outer clad is made of a resin, and examples of the resin include an ultraviolet curable resin and a thermosetting resin.

The outer resin layer 14 is made of a resin different from the resin forming the inner resin layer 13, and examples of the resin include an ultraviolet curable resin and a thermosetting resin.

The resin protective layer 15 is made of a resin different from the resin forming the outer resin layer 14, and examples of the resin include an ultraviolet curable resin and a thermosetting resin.

The resin forming the outer resin layer 14 and the resin protective layer 15 is preferably an ultraviolet curable resin when the inner resin layer 13 is an ultraviolet curable resin, and the inner resin layer 13 is a thermosetting resin. In that case, it is preferably a thermosetting resin. By doing so, the resin that becomes the inner resin layer 13, the resin that becomes the outer resin layer 14, and the resin that becomes the resin protective layer 15 can be cured at once, and the productivity of the optical fiber 1 can be improved. ..

Next, an optical fiber manufacturing apparatus according to an embodiment of the present invention will be described.

FIG. 2 is a diagram schematically showing an optical fiber manufacturing apparatus according to this embodiment. The manufacturing apparatus 100 of the optical fiber 1 shown in FIG. 2 mainly includes a base material feeding device 20, a heating furnace 25, a cooling device 30, a coating layer forming device 40, a turn pulley 80, a take-up device 81, and a take-up device 82. Prepare The optical fiber 1 is manufactured by the optical fiber manufacturing apparatus 100.

The base material feeding device 20 is a device that feeds the optical fiber base material 1P from the lower end side into the heating furnace 25 at a predetermined speed. In the present embodiment, the base material feeding device 20 is attached to the upper end portion of the optical fiber base material 1P to be the optical fiber bare wire 1N, and the optical fiber base material 1P is placed around the center axis of the optical fiber base material 1P. It is configured so that it can be fed into the heating furnace 25 while being rotated at a predetermined speed.

The heating furnace 25 is a furnace for heating the optical fiber preform 1P fed by the preform feeder 20. In the present embodiment, the heating furnace 25 mainly includes a core tube 26, a heating element 27, and a heat insulating material 28, and the optical fiber base material 1P fed by the base material feeding device 20 is inserted into the core tube 26. To be done. The heating element 27 is provided so as to heat the core tube 26 from the outer peripheral surface side of the core tube 26, and is, for example, a resistance type heating element. The heating element 27 may be a part of the core tube 26. Since the core tube 26 and the heating element 27 are surrounded by the heat insulating material 28, the heat generated by the heating element 27 can be effectively used.

The maximum temperature in the heating furnace 25 is the size of the optical fiber preform 1P, the target outer diameter of the bare optical fiber 1N drawn from the preform 1P for optical fiber, the tension applied to the bare optical fiber 1N, and the like. However, it may be a high temperature of about 2000°C. Therefore, the material forming the core tube 26, the heating element 27, and the heat insulating material 28 is preferably carbon, for example.

The cooling device 30 is arranged below the heating furnace 25 and cools the bare optical fiber 1N formed by drawing the optical fiber preform 1P. Examples of the cooling device 30 include a configuration in which the bare optical fiber 1N is surrounded by a member through which cooling water flows.

The coating layer forming device 40 is a device that forms the resin coating layer 12 that covers the outer peripheral surface of the bare optical fiber 1N. In the present embodiment, the coating layer forming device 40 includes a coating unit 41 and a curing unit 42. The coating section 41 has a first coating section 41F and a second coating section 41S, and the curing section 42 has a first curing section 42F and a second curing section 42S. In the 1st application part 41F, the uncured inner resin which becomes the inner resin layer 13 is apply|coated to the outer peripheral surface of the optical fiber bare wire 1N, and the outer peripheral surface of the optical fiber bare wire 1N to which the uncured inner resin was applied. Is coated with an uncured outer resin to be the outer resin layer 14. In this way, the uncured inner resin and outer resin applied to the bare optical fiber 1N by the first application portion 41F are cured by the first curing portion 42F, and the inner resin layer 13 and the outer resin layer 14 are formed. .. In the second coating portion 41S, the uncured protective resin that will become the resin protective layer 15 is coated on the outer peripheral surface of the outer resin layer 14 thus formed. The uncured protective resin is cured by the second curing portion 42S to cure the protective resin, and the resin protective layer 15 is formed.

FIG. 3 is a diagram schematically showing the coating unit shown in FIG. 2, and is a diagram schematically showing a vertical cross section of the coating unit. As shown in FIG. 3, the coating section 41 of the present embodiment has the first coating section 41F and the second coating section 41S as described above. The first coating section 41F mainly includes a first die body 43 in which the first storage chamber 44, the second storage chamber 45, and the third storage chamber 46 are formed, and a guide member 70. The first die body 43 has a first block 51, a second block 52, and a third block 53. The second coating section 41S mainly includes a second die body 54 in which the fourth storage chamber 47 is formed.

The first block 51 of the first die body 43 in the first coating part 41F has a cylindrical side wall part 51s extending in the vertical direction and a bottom wall part 51b closing an opening on the lower side of the side wall part 51s. Then, the first die 55 is attached to the bottom wall portion 51b. The first die 55 is a substantially cylindrical member, is fitted into a circular through hole formed in the bottom wall portion 51b, and is fixed to the bottom wall portion 51b. The lower portion of the first die 55 as described above projects downward from the bottom wall portion 51b. The outer peripheral surface of the portion of the first die 55 projecting downward from the bottom wall portion 51b is inclined downward toward the center. Further, the inner peripheral surface of the first die 55 is inclined downward toward the center. Therefore, the portion where the inner diameter of the first die 55 is the minimum is the first die opening 55H which is the opening at the lower end of the first die 55, and the diameter of this first die opening 55H is the outside of the bare optical fiber 1N. Larger than diameter. The internal space of the first block 51 as described above serves as the first storage chamber 44. The upper part of the first accommodating chamber 44 is opened to form an opening 44H, and the first accommodating chamber 44 has a first die port 55H in the lower part.

The bare optical fiber 1N is passed through the first housing chamber 44 so as to pass through the upper opening 44H to the first die port 55H. The gap between the edge of the opening 44H and the outer peripheral surface of the bare optical fiber 1N is, for example, 10 mm or more. In addition, the diameter of the first die port 55H is, for example, larger than the outer diameter of the bare optical fiber 1N and not more than twice the outer diameter of the bare optical fiber 1N.

In addition, the uncured inner resin 61, which is a part of the inner resin layer 13 in the resin coating layer 12, is supplied from the upper opening 44H to the first accommodation chamber 44, and the inner resin 61 is stored and stored as gas. The liquid surface of the inner resin 61 that is in contact is formed in the first storage chamber 44.

The second block 52 of the first die body 43 includes a cylindrical side wall portion 52s that surrounds the side wall portion 51s and is separated from the outer peripheral surface of the side wall portion 51s of the first block 51, and a bottom wall portion 51b of the first block 51. A bottom wall portion 52b that is spaced apart from the lower surface and closes the lower side opening of the side wall portion 52s, and extends from the entire circumference of the upper end portion of the side wall portion 52s to the side wall portion 51s side of the first block 51 to form the side wall portion 51s. It has the top wall part 52t to connect. The second die 56 is attached to the bottom wall portion 52b. The second die 56 is a substantially cylindrical member, and is fitted into a circular through hole formed in the bottom wall portion 52b so that the central axis of the second die 56 substantially coincides with the central axis of the first die 55. And is fixed to the bottom wall portion 52b. The lower portion of the second die 56 as described above projects downward from the bottom wall portion 52b. The outer peripheral surface of the portion of the second die 56 that projects downward from the bottom wall portion 52b is inclined downward toward the center. Further, the inner peripheral surface of the second die 56 is inclined downward toward the center. Therefore, the portion where the inner diameter of the second die 56 is the minimum is the second die opening 56H which is the opening at the lower end of the second die 56. The space surrounded by the second block 52 and the first block 51 is the second storage chamber 45. The second storage chamber 45 communicates with the first storage chamber 44 through the first die port 55H and has a second die port 56H below. A resin supply port 64 communicating with the second storage chamber 45 is formed in the top wall portion 52t of the second block 52.

As described above, since the second storage chamber 45 communicates with the first storage chamber 44 via the first die port 55H, the bare optical fiber 1N passing through the first die port 55H is transferred to the second storage chamber 45. Is inserted. That is, it can be understood that the first die port 55H also serves as the first insertion port for inserting the bare optical fiber 1N into the second storage chamber 45. Then, the bare optical fiber 1N that has passed through the first storage chamber 44 is passed through the second storage chamber 45 so as to exit from the first die port 55H as the first insertion port to the second die port 56H. The diameter of the second die port 56H is, for example, larger than the outer diameter of the bare optical fiber 1N, and not more than twice the outer diameter of the bare optical fiber 1N.

In addition, the uncured inner resin 61, which is another part of the inner resin layer 13 in the resin coating layer 12, is supplied from the resin supply port 64 to the second storage chamber 45, and the inner resin 61 has a predetermined pressure. Filled with. Therefore, the inside of the second storage chamber 45 is filled with the inner resin 61, and the liquid surface of the inside of the second storage chamber 45 that is in contact with the gas is not formed. In the present embodiment, the pressure of the inner resin 61 filled in the second storage chamber 45 is set to be higher than the pressure of the inner resin 61 stored in the first storage chamber 44 in the vicinity of the first die port 55H.

The third block 53 of the first die body 43 includes a cylindrical side wall portion 53s that surrounds the side wall portion 52s and is separated from the outer peripheral surface of the side wall portion 52s of the second block 52, and a bottom wall portion 52b of the second block 52. A bottom wall portion 53b that separates from the lower surface and closes the lower side opening of the side wall portion 53s, and extends from the entire circumference of the upper end portion of the side wall portion 53s to the side wall portion 52s side of the second block 52 to form the side wall portion 52s. It has the top wall part 53t to connect. The third die 57 is attached to the bottom wall portion 53b. The third die 57 is a generally cylindrical member, and is fitted into a circular through hole formed in the bottom wall portion 53b so that the central axis of the third die 57 substantially coincides with the central axis of the second die 56. And is fixed to the bottom wall portion 53b. The lower portion of the third die 57 as described above projects downward from the bottom wall portion 53b. The outer peripheral surface of the portion of the third die 57 projecting downward from the bottom wall portion 53b is inclined downward toward the center. Further, the inner peripheral surface of the third die 57 is inclined downward toward the center. Therefore, the portion where the inner diameter of the third die 57 is minimum is the third die opening 57H which is the opening at the lower end of the third die 57. The space surrounded by the side wall portion 52s and the bottom wall portion 53b of the third block 53 and the second block 52 is the third storage chamber 46. The third storage chamber 46 communicates with the second storage chamber 45 via the second die port 56H and has a third die port 57H below. Further, a resin supply port 65 communicating with the third storage chamber 46 is formed in the top wall portion 53t of the third block 53.

As described above, since the third storage chamber 46 communicates with the second storage chamber 45 via the second die port 56H, the bare optical fiber 1N passing through the second die port 56H enters the third storage chamber 46. Is inserted. That is, it can be understood that the second die port 56H also serves as the second insertion port for inserting the bare optical fiber 1N into the third storage chamber 46. Then, the bare optical fiber 1N that has passed through the second storage chamber 45 is passed through the third storage chamber 46 so as to exit from the second die port 56H serving as the second insertion port to the third die port 57H. The diameter of the third die port 57H is, for example, larger than the diameter of the second die port 56H and is not more than twice the diameter of the second die port 56H.

Further, the uncured outer resin 62, which becomes the outer resin layer 14 in the resin coating layer 12, is supplied from the resin supply port 65 to the third storage chamber 46, and the outer resin 62 is filled with the predetermined pressure. Therefore, the inside of the third storage chamber 46 is filled with the outer resin 62, and the liquid surface of the third storage chamber 46 that is in contact with the gas of the outer resin 62 is not formed. In the present embodiment, the pressure of the outer resin 62 filled in the third storage chamber 46 is set higher than the pressure of the inner resin 61 stored in the first storage chamber 44 in the vicinity of the first die port 55H. The pressure of the outer resin 62 filled in the third storage chamber 46 is smaller than the pressure of the inner resin 61 filled in the second storage chamber 45.

The second die body 54 of the second coating section 41S is separated from the first die body 43 of the first coating section 41F, and is arranged below the first die body 43. The second die body 54 has a cylindrical side wall portion 54s extending in the up-down direction, a bottom wall portion 54b that closes the lower side opening of the side wall portion 54s, and a top that closes the upper side opening of the side wall portion 54s. It has a wall 54t. A fourth die 58 is attached to the bottom wall portion 54b, and a nipple 59 is attached to the top wall portion 54t. The fourth die 58 is a substantially cylindrical member and is fitted into a circular through hole formed in the bottom wall portion 54b so that the central axis of the fourth die 58 is substantially aligned with the central axis of the third die 57. And is fixed to the bottom wall portion 54b. The lower portion of the fourth die 58 as described above projects downward from the bottom wall portion 54b. The outer peripheral surface of the portion of the fourth die 58 projecting downward from the bottom wall portion 54b is inclined downward toward the center. Further, the inner peripheral surface of the fourth die 58 is inclined downward toward the center. Therefore, the portion where the inner diameter of the fourth die 58 is minimum is the fourth die opening 58H which is the opening at the lower end of the fourth die 58. The nipple 59 is a substantially cylindrical member and is fitted into a circular through hole formed in the top wall 54t so that the center axis of the nipple 59 substantially coincides with the center axis of the third die 57. It is fixed at 54t. The lower portion of such a nipple 59 projects downward from the top wall portion 54t. The outer peripheral surface of the portion of the nipple 59 that projects downward from the top wall portion 54t is inclined downward toward the center. The inner peripheral surface of the nipple 59 is inclined downward toward the center. Therefore, the portion where the inner diameter of the nipple 59 is the smallest is the third insertion port 59H which is the opening at the lower end of the nipple 59. Such an internal space of the second die body 54 serves as a fourth accommodation chamber 47, and the fourth accommodation chamber 47 has a third insertion port 59H in the upper part and a fourth die port 58H in the lower part. Further, a resin supply port 66 communicating with the fourth storage chamber 47 is formed in the top wall portion 54t of the second die body 54.

The bare optical fiber 1N that has passed through the third storage chamber 46 is passed through the fourth storage chamber 47 so as to exit from the third insertion port 59H to the fourth die port 58H. In this way, the bare optical fiber 1N sequentially passes through the first storage chamber 44, the second storage chamber 45, the third storage chamber 46, and the fourth storage chamber 47. The diameter of the third insertion port 59H is, for example, larger than the diameter of the third die port 57H and is 5 times or less the diameter of the third die port 57H. Further, the diameter of the fourth die port 58H is, for example, larger than the diameter of the third die port 57H and is not more than twice the diameter of the third die port 57H.

Further, the uncured protective resin 63, which becomes the resin protective layer 15 in the resin coating layer 12, is supplied from the resin supply port 66 to the fourth storage chamber 47, and the protective resin 63 is filled with the predetermined pressure. Therefore, the interior of the fourth accommodation chamber 47 is filled with the protective resin 63, and the liquid surface of the fourth accommodation chamber 47 in contact with the gas of the protective resin 63 is not formed. The protective resin 63 may overflow from the third insertion port 59H of the nipple 59 to the outside of the fourth storage chamber 47. In the present embodiment, the pressure of the protective resin 63 filled in the fourth storage chamber 47 is set higher than the pressure of the inner resin 61 stored in the first storage chamber 44 in the vicinity of the first die port 55H. However, the pressure of the protective resin 63 is not particularly limited.

FIG. 4 is a perspective view schematically showing the guide member shown in FIG. The guide member 70 of the present embodiment is a cylindrical member that extends in the vertical direction. On the side surface of the guide member 70, three slits 71 are formed as a communicating portion that connects the outer region and the inner region of the guide member 70. The three slits 71 extend upward from the lower end of the guide member 70 to a predetermined position, and are formed so as to be located at substantially equal intervals in the circumferential direction of the guide member 70. As shown in FIG. 3, such a guide member 70 has at least the slit 71 inside the inner resin 61 stored in the first housing chamber 44 while the lower end thereof is separated from the bottom wall portion 51b of the first block 51. A part of the optical fiber is placed so that the bare optical fiber 1N passes through the area inside the guide member 70. The guide member 70 arranged in this manner surrounds the bare optical fiber 1N at least in the inner resin 61 stored in the first housing chamber 44 and apart from the outer peripheral surface of the bare optical fiber 1N. The inner diameter of the guide member 70 is set to a predetermined value between the inner peripheral surface of the guide member 70 and the outer peripheral surface of the bare optical fiber 1N when the bare optical fiber 1N is inserted into the area inside the guide member 70. The diameter is such that a gap, for example, a gap of 5 mm or more is formed. Further, by disposing the guide member 70 in this way, the inner resin 61 can flow into the region inside the guide member 70 through the slit 71 and the opening at the lower end of the guide member 70. That is, the guide member 70 can allow the inner resin 61 to flow into the region inside the guide member 70.

The curing section 42 shown in FIG. 2 has the first curing section 42F and the second curing section 42S as described above. The first curing section 42F is arranged between the first coating section 41F and the second coating section 41S. For example, when the inner resin 61 and the outer resin 62 applied to the bare optical fiber 1N by the first application portion 41F are UV curable resins, the first curing portion 42F is applied with the inner resin 61 and the outer resin 62. In addition, it is a device that irradiates the bare optical fiber 1N with ultraviolet rays. On the other hand, when the inner resin 61 and the outer resin 62 applied to the bare optical fiber 1N by the first application portion 41F are thermosetting resins, the first curing portion 42F applies the inner resin 61 and the outer resin 62. It is a device for applying heat to the stripped bare optical fiber 1N. In addition, when one of the inner resin 61 and the outer resin 62 applied to the bare optical fiber 1N by the first applying unit 41F is an ultraviolet curable resin and the other is a thermosetting resin, the first curing unit 42F is The optical fiber bare wire 1N coated with the inner resin 61 and the outer resin 62 is irradiated with ultraviolet rays and heated.

The second curing section 42S is arranged below the second coating section 41S. When the protective resin 63 applied to the bare optical fiber 1N by the second coating unit 41S is an ultraviolet curable resin, the second curing portion 42S applies ultraviolet light to the bare optical fiber 1N coated with the protective resin 63. It is used as a device for irradiating. On the other hand, when the protective resin 63 applied to the bare optical fiber 1N by the second applying unit 41S is a thermosetting resin, the second curing unit 42S applies the bare optical fiber 1N to which the protective resin 63 is applied. It is a device that applies heat.

The take-up device 81 is a device for taking up the optical fiber 1 whose direction is changed by the turn pulley 80 at a predetermined take-up speed, and the take-up device 82 is a device for taking up the optical fiber 1 on a bobbin.

Next, a method for manufacturing the optical fiber according to the embodiment of the present invention will be described.

FIG. 5 is a flowchart showing a method for manufacturing an optical fiber according to the embodiment of the present invention. The optical fiber 1 is manufactured using the optical fiber manufacturing apparatus 100 by the optical fiber manufacturing method of the present embodiment. As shown in FIG. 5, the manufacturing method of the optical fiber 1 of the present embodiment includes a preparation step P1, a drawing step P2, a cooling step P3, a first resin applying step P4, and a second resin applying step P5. A third resin coating step P6, a first curing step P7, a fourth resin coating step P8, and a second curing step P9 are provided as main steps.

<Preparation process P1>
In this step, first, an optical fiber preform 1P having a core glass body to be the core 10 of the optical fiber 1 and a clad glass body to be the clad 11 is prepared. FIG. 6 is a view showing a cross section perpendicular to the longitudinal direction of the optical fiber preform 1P prepared in the preparation step P1. As shown in FIG. 6, the optical fiber preform 1P includes a core glass body 10P that serves as the core 10 of the optical fiber 1 and a clad glass body 11P that serves as the clad 11. The core glass body 10P is arranged at the center of the clad glass body 11P. In the cross section perpendicular to the longitudinal direction, the outer circumference of the clad glass body 11P is approximately a regular heptagon. That is, the outer shape of the optical fiber preform 1P in the cross section perpendicular to the longitudinal direction is approximately a regular heptagon. The method for producing the optical fiber preform 1P is not particularly limited. For example, an optical fiber preform having a circular outer shape is produced by an MCVD method (Modified chemical vapor deposition method), and the optical fiber preform having a circular outer shape is cut to form a regular heptagonal optical fiber preform. Make 1P.

Next, the optical fiber preform 1P is installed in the heating furnace 25. As shown in FIG. 2, the upper end of the optical fiber preform 1P is fixed to the preform feeding device 20, and the optical fiber preform 1P is inserted into the furnace core tube 26 of the heating furnace 25 from the lower end.

<Drawing process P2>
This step is a step of drawing the lower end portion of the optical fiber preform 1P while heating it in the heating furnace 25.

As described above, the optical fiber preform 1P is installed in the heating furnace 25 in the preparation step P1. In this embodiment, the optical fiber preform 1P thus installed is rotated about the central axis Pa of the optical fiber preform 1P. Further, the heating element 27 of the heating furnace 25 is caused to generate heat to heat the lower end portion of the rotating optical fiber preform 1P. The lower end of the optical fiber preform 1P is melted by being heated in the heating furnace 25, a tapered neck-down ND is formed, the diameter is reduced, and the glass wire is drawn out from the heating furnace 25. When the drawn glass wire exits the heating furnace 25, it is immediately solidified and becomes a bare optical fiber 1N composed of the core 10 and the clad 11. As described above, the core glass body 10P is arranged at the center of the clad glass body 11P, and the optical fiber preform 1P is rotated around the central axis Pa of the optical fiber preform 1P and drawn. Therefore, a permanent twist centered on the central axis of the core 10 is imparted to the bare optical fiber 1N. Further, as described above, the outer shape of the optical fiber preform 1P in the cross section perpendicular to the longitudinal direction is approximately a regular heptagon, and thus the outer shape of the bare optical fiber 1N in the cross section perpendicular to the longitudinal direction is a generally regular heptagon. It

The amount of twist imparted to the bare optical fiber 1N is determined by the take-up speed of the optical fiber 1 by the take-out device 81 and the preform 1P for the optical fiber by the preform feeding device 20 around the central axis Pa of the preform 1P for the optical fiber. Adjusted by adjusting the speed at which to rotate, and.

<Cooling process P3>
This step is a step of cooling the bare optical fiber 1N to an appropriate temperature. The bare optical fiber 1N is cooled by passing through the cooling device 30. When entering the cooling device 30, the temperature of the bare optical fiber 1N is, for example, about 200° C., but when leaving the cooling device 30, the temperature of the bare optical fiber 1N is, for example, 20° C. to 50° C. ..

<First resin coating step P4>
This step is a step of applying an uncured inner resin 61 which is a part of the inner resin layer 13 to the outer peripheral surface of the bare optical fiber 1N.

First, as a preparatory step for performing the first resin coating step P4, the bare optical fiber 1N sent out from the cooling device 30 is applied to the coating section 41 in a state where no resin is stored in each of the storage chambers 44, 45, 46, 47. Pass through. Specifically, the bare optical fiber 1N is inserted into the first housing chamber 44 from above the first housing chamber 44 and passed through the first die port 55H. At this time, the bare optical fiber 1N is passed through the area inside the guide member 70. Since the first storage chamber 44 and the second storage chamber 45 are communicated with each other through the first die port 55H, the bare optical fiber 1N passing through the first die port 55H is inserted into the second storage chamber 45. .. The bare optical fiber 1N inserted in the second storage chamber 45 is passed through the second die port 56H. Since the second storage chamber 45 and the third storage chamber 46 communicate with each other through the second die port 56H, the bare optical fiber 1N passing through the second die port 56H is inserted into the third storage chamber 46. .. The bare optical fiber 1N inserted into the third storage chamber 46 is passed through the third die port 57H and is taken out of the third storage chamber 46. The bare optical fiber 1N exiting from the third accommodation chamber 46 is inserted into the fourth accommodation chamber 47 from the third insertion port 59H, passed through the fourth die port 58H, and ejected from the fourth accommodation chamber 47. In this way, the optical fiber bare wire 1N to be sent out is brought into a state of sequentially passing through the first accommodation chamber 44, the second accommodation chamber 45, the third accommodation chamber 46, and the fourth accommodation chamber 47.

Further, resin is stored in each of the storage chambers 44, 45, 46, 47. First, the uncured protective resin 63 to be the resin protective layer 15 is supplied to the fourth accommodation chamber 47 whose die port is located at the lowest position, and the fourth accommodation chamber 47 is filled with the protective resin 63 at a predetermined pressure. Next, the uncured outer resin 62 to be the outer resin layer 14 is supplied to the third accommodation chamber 46, which is located above the fourth die opening 58H of the fourth accommodation chamber 47, so as to remove the outer resin 62 from the fourth die opening 58H. The 3 storage chamber 46 is filled with a predetermined pressure. Next, the uncured inner resin 61, which is another part of the inner resin layer 13, is supplied to the second accommodation chamber 45 in which the die port is located above the third die port 57H of the third accommodation chamber 46. The inner resin 61 is filled into the second storage chamber 45 with a predetermined pressure. Next, the uncured inner resin 61 which is a part of the inner resin layer 13 is supplied to the inside of the first storage chamber 44 in which the die port of the second storage chamber 45 is located above the second die port 56H. The resin 61 is stored in the first storage chamber 44. In this way, the resin is stored in each of the storage chambers 44, 45, 46, 47. The time when the resin starts to be supplied to the storage chambers 44, 45, 46, 47 is not particularly limited. However, as described above, it is preferable to supply the resin in order from the fourth storage chamber 47 whose die port is located at the lowest position to the third storage chamber 46, the second storage chamber 45, and the first storage chamber 44. By doing so, the inner resin 61 flows into the third storage chamber 46 and the inner resin 61 and the outer resin 62 are mixed with each other, or the inner resin 61 and the outer resin 62 flow into the fourth storage chamber 47. It is possible to prevent the inner resin 61 or the outer resin 62 and the protective resin 63 from being mixed with each other.

In this way, as shown in FIG. 3, the bare optical fiber 1N sequentially passes through the first accommodation chamber 44, the second accommodation chamber 45, the third accommodation chamber 46, and the fourth accommodation chamber 47, and each accommodation The resin is housed in the chambers 44, 45, 46, 47. By doing so, the bare optical fiber 1N passes through the first storage chamber 44 in which the uncured inner resin 61 is stored. That is, the bare optical fiber 1N is inserted from above the first housing chamber 44 into the first housing chamber 44 in which the uncured inner resin 61, which is a part of the inner resin layer 13, is stored, and the first die port is inserted. It will be extracted from 55H. As described above, since the diameter of the first die opening 55H is set to be larger than the outer diameter of the bare optical fiber 1N, there is a gap between the outer peripheral surface of the bare optical fiber 1N and the edge of the first die opening 55H. Is formed. Therefore, by pulling out the bare optical fiber 1N from the first die port 55H, the inner resin 61 is poured out from this gap, and the inner resin 61 is applied to the outer peripheral surface of the bare optical fiber 1N. The thickness of the inner resin 61 thus coated is substantially the same as the width of this gap, and the outer diameter of the bare optical fiber 1N coated with the inner resin 61 is substantially the same as the diameter of the first die port 55H. To be done. The inner resin 61 is stored in the first storage chamber 44 whose upper side is open. Therefore, when the bare optical fiber 1N passes through the first storage chamber 44, convection Cf is generated in the inner resin 61 around the bare optical fiber 1N. This convection Cf is a circular flow that goes downward on the side of the bare optical fiber 1N and goes upward on the side opposite to the side of the bare optical fiber 1N. Then, on the liquid surface of the inner resin 61, a meniscus Me that is recessed in a concave shape around the bare optical fiber 1N is formed. In the present embodiment, as described above, the guide member 70 that surrounds the bare optical fiber 1N is arranged inside the inner resin 61. Therefore, the convection Cf is regulated so as to be formed in the region closer to the optical fiber bare wire 1N side than the guide member 70, and the meniscus Me is also formed in the region closer to the optical fiber bare wire 1N side than the guide member 70. It is regulated to be done. Therefore, as compared with the case where the guide member 70 is not arranged, it is possible to stabilize the convection Cf by narrowing the region where the convection Cf in the inner resin 61 is generated and reducing the meniscus Me that is recessed in a concave shape. The slit 71 formed on the side surface of the guide member 70 is located inside the inner resin 61 as described above. Therefore, the inner resin 61 can pass back and forth between the outer region of the guide member 70 and the inner region of the guide member 70 through the slit 71. Further, the lower end of the guide member 70 is separated from the bottom wall portion 51b of the first block 51. Therefore, the inner resin 61 can pass back and forth between the outer region of the guide member 70 and the inner region of the guide member 70 through the lower opening of the guide member 70.

<Second resin coating step P5>
In this step, another part of the inner resin layer 13 is formed on the outer peripheral surface of the bare optical fiber 1N coated with the uncured inner resin 61, which is a part of the inner resin layer 13 in the first resin applying step P4. This is a step of applying the uncured inner resin 61.

As described above, the inner resin 61 is filled into the second storage chamber 45 at a predetermined pressure, so that the bare optical fiber 1N coated with the inner resin 61 in the first resin coating step P4 has an uncured inner resin. 61 passes through the second storage chamber 45 filled with a predetermined pressure. That is, the optical fiber bare wire 1N coated with the inner resin 61 in the first resin coating step P4 is filled with the predetermined pressure of the uncured inner resin 61 that is another part of the inner resin layer 13. It is inserted into the second accommodation chamber 45 through the first die port 55H and pulled out through the second die port 56H. As described above, the diameter of the second die port 56H is larger than the outer shape of the bare optical fiber 1N. For example, when the diameter of the second die port 56H is set to be larger than the diameter of the first die port 55H, the outer peripheral surface of the bare optical fiber 1N coated with the inner resin 61 in the first resin coating step P4 and the second A gap is formed between the edge of the die opening 56H. In FIG. 3, the outer peripheral surface of the bare optical fiber 1N coated with the inner resin 61 in the first resin coating step P4 is indicated by a broken line. Therefore, by pulling out the bare optical fiber 1N from the second die port 56H, the inner resin 61 is poured out from this gap, and the outer peripheral surface of the bare optical fiber 1N coated with the inner resin 61 in the first resin coating step P4. Inner resin 61 is applied to. In this way, the overall thickness of the inner resin 61 applied to the bare optical fiber 1N is approximately the same as the gap between the outer peripheral surface of the bare optical fiber 1N and the edge of the second die opening 56H. Adjusted. On the other hand, when the diameter of the second die opening 56H is smaller than the diameter of the first die opening 55H, a part of the inner resin 61 applied to the outer peripheral surface of the bare optical fiber 1N in the first resin applying step P4. Peels off. Here, in the second storage chamber 45, the inner resin 61 is filled with a predetermined pressure. Therefore, the inner resin 61 filled in the second storage chamber 45 is applied to the bare optical fiber 1N, and the entire thickness of the inner resin 61 applied to the bare optical fiber 1N is the outer peripheral surface of the bare optical fiber 1N. Is adjusted to be approximately the same as the gap between the edge of the second die opening 56H and the edge of the second die opening 56H. In this way, the outer diameter of the bare optical fiber 1N coated with the inner resin 61 in this step is approximately the same as the diameter of the second die port 56H.

<Third resin coating step P6>
In this step, the uncured outer resin layer 14 is formed on the outer peripheral surface of the bare optical fiber 1N coated with the uncured inner resin 61, which is another part of the inner resin layer 13 in the second resin coating step P5. This is a step of applying the outer resin 62 that becomes

By filling the third housing chamber 46 with the outer resin 62 at a predetermined pressure as described above, the bare optical fiber 1N coated with the inner resin 61 in the second resin coating step P5 is the uncured outer resin. 62 passes through the third storage chamber 46 filled with a predetermined pressure. That is, the bare optical fiber 1N coated with the inner resin 61 in the second resin coating step P5 is placed in the third storage chamber 46 in which the uncured outer resin 62 to be the outer resin layer 14 is filled at a predetermined pressure. , The second die opening 56H is inserted and the third die opening 57H is pulled out. As described above, since the diameter of the third die port 57H is set to be larger than the diameter of the second die port 56H, the diameter of the bare optical fiber 1N coated with the inner resin 61 in the second resin coating step P5 is A gap is formed between the edge of the third die opening 57H. Therefore, by pulling out the bare optical fiber 1N from the third die port 57H, the outer resin 62 is poured out from this gap, and the outer peripheral surface of the bare optical fiber 1N coated with the inner resin 61 in the second resin coating step P5. The outer resin 62 is applied to the. The thickness of the outer resin 62 applied in this manner is approximately the same as the width of this gap, and the outer diameter of the bare optical fiber 1N coated with the outer resin 62 in this step is the same as the diameter of the third die port 57H. Generally the same.

<First curing step P7>
This step is a step of curing the uncured inner resin 61 and outer resin 62 applied to the bare optical fiber 1N. The uncured inner resin 61 and outer resin 62 applied to the bare optical fiber 1N are cured by the first curing portion 42F, the inner resin 61 becomes the inner resin layer 13, and the outer resin 62 becomes the outer resin layer 14. ..

<Fourth resin coating step P8>
This step is a step of applying a protective resin 63 to be the uncured resin protective layer 15 to the outer peripheral surface of the bare optical fiber 1N in which the inner resin 61 and the outer resin 62 are cured in the first curing step P7.

As described above, the protective resin 63 is filled into the fourth storage chamber 47 at a predetermined pressure, so that the bare optical fiber 1N in which the inner resin 61 and the outer resin 62 are cured in the first curing step P7 is in an uncured state. The protective resin 63 of 4 passes through the fourth storage chamber 47 filled with a predetermined pressure. That is, the optical fiber bare wire 1N in which the inner resin 61 and the outer resin 62 are hardened in the first hardening step P7 is filled with the uncured protective resin 63 which becomes the resin protective layer 15 at a predetermined pressure. It is inserted into the chamber 47 through the third insertion port 59H and pulled out through the fourth die port 58H. As described above, the diameter of the fourth die port 58H is set to be larger than the diameter of the third die port 57H. Therefore, in the optical fiber bare wire 1N in which the inner resin 61 and the outer resin 62 are cured in the first curing step P7. A gap is formed between the outer peripheral surface and the edge of the fourth die opening 58H. Therefore, the protective resin 63 is poured out from this gap by extracting the bare optical fiber 1N from the fourth die port 58H, and the bare inner fiber 61 and the outer resin 62 are cured in the first curing step P7. A protective resin 63 is applied to the outer peripheral surface of the. The thickness of the protective resin 63 applied in this manner is substantially the same as the width of this gap, and the outer diameter of the bare optical fiber 1N coated with the protective resin 63 in this step is equal to the diameter of the fourth die port 58H. Generally the same.

<Second curing step P9>
This step is a step of curing the uncured protective resin 63 applied to the bare optical fiber 1N. The uncured protective resin 63 applied to the bare optical fiber 1N is cured by the second curing section 42S, the protective resin 63 becomes the resin protective layer 15, and the resin coating layer 12 is formed. As a result, the bare optical fiber 1N becomes the optical fiber 1 shown in FIG.

The direction of the optical fiber 1 is changed by the turn pulley 80, and the optical fiber 1 is wound by the winding device 82.

As described above, in the method of manufacturing the optical fiber 1 according to the present embodiment, the preparation step P1, the drawing step P2, the cooling step P3, the first resin applying step P4, the second resin applying step P5, and the third resin applying step. The optical fiber 1 shown in FIG. 1 is manufactured through P6, the first curing step P7, the fourth resin coating step P8, and the second curing step P9.

In the manufacturing method of the present embodiment, the uncured inner resin 61 that becomes the inner resin layer 13 is applied to the outer peripheral surface of the bare optical fiber 1N by the first resin applying step P4 and the second resin applying step P5. Further, the uncured outer resin 62 to be the outer resin layer 14 is applied to the outer peripheral surface of the bare optical fiber 1N to which the uncured inner resin 61 has been applied in the third resin applying step P6. The uncured inner resin 61 and outer resin 62 thus applied are cured to form the inner resin layer 13 and the outer resin layer 14. In the manufacturing method of the present embodiment, the bare optical fiber 1N is passed through the first storage chamber 44, the second storage chamber 45, and the third storage chamber 46 in this order, and the upper side of the first storage chamber is open. Therefore, as compared with the case where the first housing chamber 44 is filled with the uncured inner resin 61 as in the manufacturing method described in Patent Document 1, the bare optical fiber 1N is moved in a direction perpendicular to the longitudinal direction. Even if the runout occurs, it is possible to prevent the outer peripheral surface of the bare optical fiber 1N from being damaged by the outer peripheral surface of the bare bare optical fiber 1N coming into contact with the first die body 43 in which the first housing chamber 44 is formed. it can. Therefore, the manufacturing method of the present embodiment can suppress a decrease in the mechanical strength of the optical fiber 1.

Further, in the manufacturing method of the present embodiment, in the second resin applying step P5, the inner resin layer 13 that is another part of the inner resin layer 13 is filled with a predetermined pressure in the second accommodation chamber 45. The optical fiber bare wire 1N coated with the inner resin 61 that is a part of Then, the inner resin 61, which is a part of the inner resin layer 13, is applied to the outer peripheral surface of the bare optical fiber 1N, to which the inner resin 61, which is a part of the inner resin layer 13, is applied. Since the second housing chamber 45 is filled with the inner resin 61 at a predetermined pressure, it is poured from the second die port 56H together with the bare optical fiber 1N coated with the inner resin 61 which is a part of the inner resin layer 13. It is possible to suppress fluctuations in the pressure of the uncured inner resin 61 that is discharged. Therefore, even if there is a deviation in the thickness of the inner resin 61 applied to the outer peripheral surface of the bare optical fiber 1N in the first resin application step P4, the deviation is leveled inside in the second resin application step P5. The resin 61 can be applied, and unevenness in the thickness of the inner resin layer 13 can be suppressed. In the third resin applying step P6, the inner resin 61 is applied by passing the bare optical fiber 1N coated with the inner resin 61 through the third housing chamber 46 filled with the outer resin 62 at a predetermined pressure. The outer resin 62 is applied to the outer peripheral surface of the bare optical fiber 1N. Therefore, unevenness in the thickness of the outer resin layer 14 is suppressed. In this way, in the manufacturing method of the present embodiment, it is possible to suppress unevenness in the thickness of the resin coating layer 12.

Further, in the manufacturing method of the present embodiment, at least in the inner resin 61 housed in the first housing chamber 44, the tubular guide member 70 is spaced apart from the outer peripheral surface of the bare optical fiber 1N and surrounds the bare optical fiber 1N. Are placed. The guide member 70 is configured such that the inner resin 61 can flow into a region inside the guide member 70.

By doing so, as described above, the convection Cf generated in the inner resin 61 stored in the first housing chamber 44 can be formed in the region closer to the optical fiber bare wire 1N side than the guide member 70. .. Therefore, as compared with the case where the guide member 70 is not arranged, it is possible to stabilize the convection Cf by narrowing the region where the convection Cf in the inner resin 61 is generated and reducing the meniscus Me that is depressed in a concave shape. Therefore, it is possible to prevent the thickness of the inner resin 61 applied to the outer peripheral surface of the bare optical fiber 1N from being uneven in the first resin applying step P4.

Further, in the manufacturing method of this embodiment, the guide member 70 is arranged before the inner resin 61 is stored in the first storage chamber 44. Therefore, the guide member 70 can be arranged more easily than when the guide member 70 is arranged after the inner resin 61 is stored in the first storage chamber 44.

Further, in the manufacturing method of the present embodiment, a slit 71 is formed on the side surface of the guide member 70 as a communicating portion that communicates an outer region and an inner region of the guide member 70 in the inner resin 61. .. Therefore, as compared with the case where the slit 71 is not formed on the side surface of the guide member 70, the inner resin 61 located in the outer region of the guide member 70 can be made to easily flow into the inner region of the guide member 70. The convection Cf in the inner resin 61 stored in the first storage chamber 44 can be made more stable. Therefore, it is possible to further prevent the thickness of the inner resin 61 applied to the outer peripheral surface of the bare optical fiber 1N from being uneven in the first resin applying step P4.

Further, in the manufacturing method of the present embodiment, the resin forming the inner resin layer 13 is a resin having a refractive index lower than that of the cladding 11. Therefore, it is possible to manufacture the optical fiber 1 having the double clad structure in which the clad 11 of the bare optical fiber 1N is the inner clad and the inner resin layer 13 is the outer clad.

Further, in the manufacturing method of the present embodiment, the core 10 is made of silica glass containing an active element excited by excitation light. Therefore, the manufacturing method of this embodiment can manufacture an optical fiber for amplification having a double-clad structure.

In addition, the manufacturing method of the present embodiment includes a drawing step P2 of forming the bare optical fiber 1N by drawing the optical fiber preform 1P while rotating it about the central axis Pa of the optical fiber preform 1P. .. Therefore, a permanent twist can be given to the bare optical fiber 1N. For example, as in the present embodiment, in the amplification optical fiber having the double-clad structure in which the cladding 11 of the bare optical fiber 1N is the inner cladding and the inner resin 13 layer is the outer cladding, the bare optical fiber 1N is permanently attached. By imparting a general twist, it is possible to suppress the skew light and make the light propagating through the clad 11, which is the inner clad, easily enter the core 10. Therefore, the absorption efficiency of the pumping light in the amplification optical fiber having the double clad structure can be increased. When the optical fiber preform 1P is drawn while rotating it about the central axis Pa of the optical fiber preform 1P, the bare optical fiber 1N tends to be shaken in a direction perpendicular to the longitudinal direction. is there. However, as described above, according to the optical fiber manufacturing method of the present embodiment, even if the optical fiber bare wire 1N is deflected in the direction perpendicular to the longitudinal direction, the mechanical strength of the optical fiber is reduced. It can suppress that it falls. Therefore, in the optical fiber manufacturing method of the present embodiment, the optical fiber preform 1P is drawn around while rotating the optical fiber preform 1P around the central axis Pa of the optical fiber preform 1P to form the bare optical fiber 1N. It is especially useful when

Further, in the manufacturing method of the present embodiment, the outer shape of the bare optical fiber 1N in the cross section perpendicular to the longitudinal direction is non-circular. By making the outer shape of the bare optical fiber 1N non-circular, the light propagating through the clad 11 can be repeatedly reflected while changing the reflection angle on the outer circumferential surface of the clad 11, which is the outer circumferential surface of the bare optical fiber 1N, The light propagating through the clad 11 can be easily made incident on the core 10. Therefore, in the manufacturing method of the present embodiment, as compared with the case where the outer shape of the bare optical fiber 1N in the cross section perpendicular to the longitudinal direction is circular, a double-clad amplification optical fiber that can suppress skew light is manufactured. You can

Further, in the manufacturing method of the present embodiment, the first die port 55H of the first storage chamber 44 also serves as the first insertion port for inserting the bare optical fiber 1N into the second storage chamber 45. Therefore, in the manufacturing method according to the present embodiment, the bare optical fiber 1N is coated with the inner resin 61 which is a part of the inner resin layer 13 by passing through the first die port 55H and is inserted into the second storage chamber 45. To be done. Therefore, even if the bare optical fiber 1N is shaken in a direction perpendicular to the longitudinal direction, the first die port 55H of the first storage chamber 44 does not also serve as the first insertion port of the second storage chamber 45. Compared with the above, it is possible to suppress the inner resin 61 applied to the bare optical fiber 1N from coming into contact with the edge of the first insertion opening of the second storage chamber 45. Therefore, as compared with the case where the first die port 55H does not serve as the first insertion port of the second storage chamber 45, even if the runaway of the bare optical fiber 1N occurs in the direction perpendicular to the longitudinal direction, the bare optical fiber It is possible to further suppress the occurrence of unevenness in the thickness of the inner resin 61 applied to the line 1N.

Further, in the manufacturing method of the present embodiment, the second die port 56H of the second accommodation chamber 45 also serves as the second insertion port for inserting the bare optical fiber 1N into the third accommodation chamber 46. Therefore, in the manufacturing method of the present embodiment, the bare optical fiber 1N is coated with the inner resin 61, which is the other part of the inner resin layer 13, by passing through the second die port 56H, and at the same time, the third storage chamber 46 is formed. Inserted in. Therefore, even if the bare optical fiber 1N is shaken in the direction perpendicular to the longitudinal direction, the second die port 56H of the second storage chamber 45 does not also serve as the second insertion port of the third storage chamber 46. Compared with the above, it is possible to prevent the inner resin 61 applied to the bare optical fiber 1N from coming into contact with the edge of the second insertion opening of the third storage chamber 46. Therefore, as compared with the case where the second die port 56H does not serve as the insertion port of the third storage chamber 46, even if the runaway of the bare optical fiber 1N occurs in the direction perpendicular to the longitudinal direction, the bare optical fiber 1N It is possible to further suppress the occurrence of unevenness in the thickness of the inner resin 61 applied to the.

When the second die port 56H also serves as the second insertion port of the third storage chamber 46 as in the present embodiment, the pressure of the outer resin 62 filled in the third storage chamber 46 is stored in the second storage chamber 45. It is preferable that the pressure is smaller than the pressure of the filled inner resin 61. By doing so, it is possible to prevent the outer resin 62 filled in the third storage chamber 46 from flowing into the second storage chamber 45. Further, compared to the case where the pressure of the outer resin 62 filled in the third storage chamber 46 is set to be higher than the pressure of the inner resin 61 filled in the second storage chamber 45, the bare optical fiber 1N is coated. The thickness of the inner resin 61 can be increased.

Further, in the manufacturing method of the present embodiment, since the fourth resin coating step P8 is further provided, the optical fiber 1 having the resin coating layer 12 including three resin layers can be manufactured.

Further, the optical fiber 1 manufacturing apparatus 100 of the present embodiment includes the first die body 43 including the first housing chamber 44, the second housing chamber 45, and the third housing chamber 46. The upper part of the first storage chamber 44 is open, and the first storage chamber 44 has a first die port 55H in the lower part. The second storage chamber 45 has a first die port 55H as an insertion port on the upper side and a second die port 56H on the lower side. The third storage chamber 46 has a second die port 56H as an insertion port on the upper side and a third die port 57H on the lower side. The inner resin 61, which is a part of the inner resin layer 13, is stored in the first housing chamber 44, and the inner resin 61, which is another part of the inner resin layer 13, is filled in the second housing chamber 45 at a predetermined pressure. Then, the third housing chamber 46 is filled with the outer resin 62, which becomes the outer resin layer 14, at a predetermined pressure. The bare optical fiber 1N is passed through the first storage chamber 44 so as to pass through the first die port 55H from above. The bare optical fiber 1N that has passed through the first storage chamber 44 is passed through the second storage chamber 45 so as to escape from the first die port 55H as an insertion port to the second die port 56H. The bare optical fiber 1N that has passed through the second storage chamber 45 is passed through the third storage chamber 46 so as to escape from the second die port 56H serving as an insertion port to the third die port 57H.

In the manufacturing apparatus 100 of the present embodiment, the bare optical fiber 1N is passed through the first storage chamber 44, the second storage chamber 45, and the third storage chamber 46 in this order, and the upper side of the first storage chamber 44 is open. Therefore, as described above, even if the bare optical fiber 1N is shaken in the direction perpendicular to the longitudinal direction, the outer peripheral surface of the bare optical fiber 1N contacts the first die body 43 and the bare optical fiber It is possible to prevent the outer peripheral surface of the wire 1N from being scratched, and to prevent the mechanical strength of the optical fiber 1 from decreasing. Further, in the manufacturing apparatus 100 of the present embodiment, the bare optical fiber 1N coated with the inner resin 61 which is a part of the inner resin layer 13 has a predetermined inner resin 61 which is another part of the inner resin layer 13. It passes through the second storage chamber 45 filled with pressure. Therefore, as described above, even if the thickness of the inner resin 61, which is a part of the inner resin layer 13 applied to the outer peripheral surface of the bare optical fiber 1N, is uneven, the unevenness should be leveled. The inner resin 61, which is another part of the inner resin layer 13, can be applied, and unevenness in the thickness of the inner resin layer 13 can be suppressed. Further, in the manufacturing apparatus 100 of the present embodiment, since the bare optical fiber 1N coated with the inner resin 61 passes through the third housing chamber 46 filled with the outer resin 62 at a predetermined pressure, as described above, The unevenness in the thickness of the outer resin layer 14 is suppressed. In this way, the manufacturing apparatus 100 of the present embodiment can suppress the decrease in the mechanical strength of the optical fiber 1 while suppressing the deviation of the thickness of the resin coating layer 12 from occurring.

In addition, since the manufacturing apparatus 100 of the present embodiment includes the guide member 70, it is possible to prevent the thickness of the inner resin 61 applied to the outer peripheral surface of the bare optical fiber 1N from being uneven as described above.

Further, on the side surface of the guide member 70, a slit 71 is formed as a communication portion that connects an outer region and an inner region of the guide member 70 in the inner resin 61. Therefore, as compared with the case where the slit 71 is not formed on the side surface of the guide member 70, the inner resin 61 located in the outer region of the guide member 70 can be made to easily flow into the inner region of the guide member 70. The convection Cf in the inner resin 61 stored in the first storage chamber 44 can be made more stable. Therefore, it is possible to further prevent the thickness of the inner resin 61 applied to the outer peripheral surface of the bare optical fiber 1N from being uneven.

Further, in the manufacturing apparatus 100 of the present embodiment, the first dice port 55H of the first storage chamber 44 also serves as the first insertion port for inserting the bare optical fiber 1N into the second storage chamber 45, and thus the first dice. The body 43 can be downsized. Further, in the manufacturing apparatus 100 of the present embodiment, as described above, the bare optical fiber 1N is coated with the inner resin 61 which is a part of the inner resin layer 13 by passing through the first die port 55H, and the second It is inserted into the accommodation chamber 45. Therefore, even if the bare optical fiber 1N is shaken in a direction perpendicular to the longitudinal direction, the first die port 55H of the first storage chamber 44 does not also serve as the first insertion port of the second storage chamber 45. Compared with the above, it is possible to suppress the inner resin 61 applied to the bare optical fiber 1N from coming into contact with the edge of the first insertion opening of the second storage chamber 45. Therefore, as compared with the case where the first die port 55H does not serve as the insertion port of the second accommodation chamber 45, even if the bare optical fiber 1N is shaken in the direction perpendicular to the longitudinal direction, the bare optical fiber The unevenness in the thickness of the inner resin 61 applied to 1N can be further suppressed.

Further, in the manufacturing apparatus 100 of the present embodiment, the second dice port 56H of the second storage chamber 45 also serves as the second insertion port for inserting the bare optical fiber 1N into the third storage chamber 46, so that the first dice. The body 43 can be downsized. Further, in the manufacturing apparatus 100 of the present embodiment, as described above, the bare optical fiber 1N is coated with the inner resin 61 which is another part of the inner resin layer 13 by passing through the second die port 56H. It is inserted into the third storage chamber 46. Therefore, even if the bare optical fiber 1N is shaken in the direction perpendicular to the longitudinal direction, the second die port 56H of the second storage chamber 45 does not also serve as the second insertion port of the third storage chamber 46. Compared with the above, it is possible to prevent the inner resin 61 applied to the bare optical fiber 1N from coming into contact with the edge of the second insertion opening of the third storage chamber 46. Therefore, compared with the case where the second die port 56H does not also serve as the insertion port of the third storage chamber 46, even if the optical fiber bare wire 1N is shaken in the direction perpendicular to the longitudinal direction, the bare optical fiber line The unevenness in the thickness of the inner resin 61 applied to 1N can be further suppressed.

Although the present invention has been described above by taking the embodiment as an example, the present invention is not limited thereto.

For example, in the above-described embodiment, the optical fiber 1 which is a double-clad structure amplification optical fiber has been described as an example. However, the optical fiber has a core, a clad that surrounds the outer peripheral surface of the core, and a resin coating layer that includes an inner resin layer that covers the outer peripheral surface of the clad and an outer resin layer that covers the outer peripheral surface of the inner resin layer. As far as it is limited, it is not particularly limited. For example, the optical fiber may be an optical fiber in which an active element excited by excitation light is not added to the core, or an optical fiber having a single clad structure in which the inner resin layer 13 is not an outer clad, It may be a multi-core fiber having a core. In addition, the resin coating layer 12 of the above-described embodiment has the resin protective layer 15 that covers the outer peripheral surface of the outer resin layer 14. However, the resin coating layer 12 only needs to have at least the inner resin layer 13 and the outer resin layer 14, and the resin coating layer 12 does not need to have the resin protective layer 15 and is more than the resin protective layer 15. You may have another resin layer on the outer side. For example, when the resin coating layer 12 does not have the resin protective layer 15, the optical fiber manufacturing method does not include the fourth resin coating step P8 and the second curing step P9, and the configuration of the coating section 41 is the second coating section. The configuration of 41S is not provided, and the configuration of the curing section 42 is configured not to have the second curing section 42S.

Further, in the above-described embodiment, the outer shape of the bare optical fiber 1N in the cross section perpendicular to the longitudinal direction is non-circular, and is approximately a regular heptagon. However, the outer shape of the bare optical fiber 1N in a cross section perpendicular to the longitudinal direction is not particularly limited, and a polygon such as a hexagon, a heptagon, an octagon, or a shape with rounded corners is used. It may be non-circular or circular.

In the drawing step P2 of the above embodiment, the lower end of the optical fiber preform 1P is heated in the heating furnace 25 while rotating the optical fiber preform 1P around the central axis Pa of the optical fiber preform 1P. It was a process of drawing a wire while heating. However, the drawing step P2 may be a step of drawing the lower end of the optical fiber preform 1P while heating the lower end of the optical fiber preform 1P in the heating furnace 25 without rotating the optical fiber preform 1P. When the drawing step P2 is such a step, it is possible to manufacture an optical fiber in which the optical fiber bare wire 1N is not permanently twisted.

Further, in the above-described embodiment, the first die body 43 in which the first storage chamber 44, the second storage chamber 45, and the third storage chamber 46 are formed, and the first coating unit 41F including the guide member 70 will be described as an example. did. However, the first application unit 41F may not include the guide member 70. However, from the viewpoint of suppressing the unevenness in the thickness of the inner resin layer 13, the first coating portion 41F preferably includes the guide member 70.

Further, in the above embodiment, the cylindrical guide member 70 in which the three slits 71 extending upward from the lower end are formed has been described as an example. However, the guide member is a tubular member that surrounds the bare optical fiber 1N while being separated from the outer peripheral surface of the bare optical fiber 1N at least in the inner resin 61 stored in the first housing chamber 44. There is no particular limitation as long as the inner resin 61 can flow into the region inside the guide member. Further, the communication portion formed on the side surface of the guide member 70 is not particularly limited as long as it communicates with the area inside the resin 61 inside the guide member 70. For example, the slit 71 formed on the side surface of the guide member 70 may be a slit extending downward from the upper end. In this case, the guide member 70 is arranged such that at least a part of the slit 71 is located inside the inner resin 61 stored in the first storage chamber 44. Further, the three slits 71 do not have to be positioned at substantially equal intervals in the circumferential direction of the guide member 70. However, from the viewpoint of stabilizing the convection Cf in the inner resin 61, it is preferable that the three slits 71 are located at substantially equal intervals in the circumferential direction of the guide member 70. The number of slits 71 is not particularly limited, and may be one, two, or four or more. Further, on the side surface of the guide member 70, instead of the slit 71, a through hole may be formed as a communicating portion penetrating from the outer peripheral surface to the inner peripheral surface, and the through hole and the slit 71 may be formed as the communicating portion. May be. When the communication portion is formed on the side surface of the guide member 70, the upper end of the guide member 70 is located above the liquid surface of the inner resin 61, and the lower end of the guide member 70 is the bottom wall portion of the first block 51. It may be in contact with 51b. Even with such a guide member 70, the inner resin 61 flows into the region inside the guide member 70 from the communicating portion of the guide member 70.

Further, the guide member 70 may be a member as shown in FIG. 7: is a figure which shows the guide member which concerns on a modification, FIG. 7(A) is a perspective view of the guide member 70 which concerns on a modification, and FIG. 7(B) is a guide member 70 which concerns on another modification. FIG. 7C is a diagram showing a state in which the guide member 70 according to another modification is arranged in the first storage chamber 44.

A guide member 70 shown in FIG. 7(A) is a cylindrical member having an outer diameter and an inner diameter reduced from the upper side to the lower side, and the side surface of the guide member 70 serves as a communicating portion in the vertical direction from the upper end to the lower end. One slit 71 extending in the direction is formed. The inner diameter at the lower end, which is the minimum inner diameter of the guide member 70, is set to be larger than the outer diameter of the bare optical fiber 1N. Even with such a guide member 70, similarly to the guide member 70 of the above-described embodiment, the region of the inner resin 61 where the convection Cf is generated is narrowed to reduce the meniscus Me that is recessed in a concave shape to stabilize the convection Cf. obtain. When the width of the slit 71 is larger than the outer shape of the bare optical fiber 1N, the guide member 70 may be removed even when the bare optical fiber 1N passes through the first storage chamber 44. It can be attached. Therefore, the guide member 70 can be removed or attached without interrupting the drawing of the optical fiber preform 1P.

The guide member 70 shown in FIG. 7(B) is a rectangular tubular member extending in the vertical direction, and one slit 71 extending in the vertical direction from the upper end to the lower end is formed on the side surface of the guide member 70 as a communicating portion. Has been done. In a cross section perpendicular to the extending direction of the guide member 70, the diameter of the circle in contact with the inner peripheral surface of the guide member 70 is larger than the outer diameter of the bare optical fiber 1N. Even with such a guide member 70, similarly to the guide member 70 of the above-described embodiment, the region of the inner resin 61 where the convection Cf is generated is narrowed to reduce the meniscus Me that is recessed in a concave shape to stabilize the convection Cf. obtain. When the width of the slit 71 is larger than the outer shape of the bare optical fiber 1N, the drawing of the optical fiber preform 1P is interrupted in the same manner as the guide member 70 shown in FIG. 7(A). The guide member 70 can be removed or attached without doing so. However, from the viewpoint of stabilizing the convection Cf in the inner resin 61, like the guide member 70 of the above embodiment and the guide member 70 shown in FIG. 7A, in a cross section perpendicular to the extending direction of the guide member 70, The inner peripheral shape of the guide member 70 is preferably circular.

The guide member 70 shown in FIG. 7C is different from the guide member 70 in the above-described embodiment in that the slit 71 is not formed and the vertical length is short. Note that in FIG. 7C, the second block 52 and the third block 53 of the first die body 43 and the second die body 54 are omitted for easy understanding. The guide member 70 as described above is wholly located inside the inner resin 61 that is stored in the first housing chamber 44, for example, and the lower end thereof is separated from the bottom wall portion 51b of the first block 51 and inside the guide member 70. It is arranged so that the bare optical fiber 1N passes through the region. In the guide member 70 arranged in this way, the inner resin 61 can flow into the region inside the guide member 70 from the opening at the upper end or the opening at the lower end of the guide member 70. Even with such a guide member 70, similarly to the guide member 70 of the above-described embodiment, the region of the inner resin 61 where the convection Cf is generated is narrowed to reduce the meniscus Me that is recessed in a concave shape to stabilize the convection Cf. obtain. Note that, as shown in FIG. 7C, when the lower end of the guide member 70 is separated from the bottom wall portion 51 b of the first block 51, the upper end of the guide member 70 is located above the liquid surface of the inner resin 61. You can do it. When the upper end of the guide member 70 is located below the liquid level of the inner resin 61, the lower end of the guide member 70 may be in contact with the bottom wall portion 51b of the first block 51. Even with such a guide member 70, the inner resin 61 flows into the region inside the guide member 70 from the opening at the upper end or the opening at the lower end of the guide member 70.

Further, in the above-described embodiment, the first die opening 55H of the first storage chamber 44 also serves as the first insertion opening for inserting the bare optical fiber 1N into the second storage chamber 45, and the second die storage chamber 45 of the second storage chamber 45. The die opening 56H also served as the second insertion opening for inserting the bare optical fiber 1N into the third storage chamber 46. However, the first die port 55H does not have to serve as the first insertion port for inserting the bare optical fiber 1N into the second storage chamber 45, and the second die port 56H has no optical fiber in the third storage chamber 46. The second insertion port for inserting the line 1N may not be used as the second insertion port. As the first die body 43 in which the first die port 55H does not serve as the first insertion port for inserting the bare optical fiber 1N into the second housing chamber 45, for example, the second block 52 is separated from the first block 51. A configuration is possible in which a nipple for inserting the bare optical fiber 1N is attached to the top wall portion 52t so that the second housing chamber 45 can be filled with the inner resin 61 at a predetermined pressure. Further, as the first die main body 43 in which the second die port 56H does not also serve as the second insertion port for inserting the bare optical fiber 1N into the third storage chamber 46, for example, the third block 53 from the first block 51 is used. There is a configuration in which a nipple for inserting the bare optical fiber 1N is attached to the top wall portion 53t which is separated from the top wall portion 53t so that the outer housing 62 can be filled with the outer resin 62 at a predetermined pressure. The nipple here is a cylindrical member like the nipple 59 attached to the second die body 54. The second block 52 and the third block 53 may be connected to each other while the first block 51 and the second block 52 are separated from each other. Further, the first block 51 and the second block 52 may be connected to each other while the second block 52 and the third block 53 are separated from each other.

Further, in the above embodiment, the uncured inner resin 61 and the outer resin 62 applied to the bare optical fiber 1N are cured by the first curing portion 42F, and are applied to the bare optical fiber 1N by the second curing portion 42S. The uncured protective resin 63 was cured. However, the curing section 42 is not particularly limited as long as it cures the uncured resin applied to the bare optical fiber 1N. For example, these uncured resins 61, 62, 63 may be cured by one curing section. For example, the curing portion may be arranged below the second coating portion 41S and configured to cure the uncured inner resin 61, outer resin 62, and protective resin 63 applied to the bare optical fiber 1N. good. In this case, the optical fiber bare wire 1N coated with the uncured inner resin 61 and the outer resin 62 is filled with the uncured protective resin 63 which becomes the resin protective layer 15 at a predetermined pressure. It is inserted into 47 through the third insertion port 59H and pulled out through the fourth die port 58H. Then, the protective resin 63 is applied to the outer peripheral surface of the bare optical fiber 1N coated with the inner resin 61 and the outer resin 62. The curing portion cures the uncured inner resin 61, outer resin 62, and protective resin 63 thus applied to the bare optical fiber 1N. In such a case, the third die opening 57H of the third storage chamber 46 may also serve as the third insertion opening 59H of the nipple 59 of the second main body portion, and the first die main body 43 and the second die main body 54 mutually Will be connected.

Further, in the above embodiment, the optical fiber bare wire 1N is formed by the drawing step P2, and the resin coating layer 12 is formed on the bare optical fiber 1N to manufacture the optical fiber 1. However, the optical fiber manufacturing method may not include the drawing step P2. In this case, for example, in the preparation step P1, the bare optical fiber 1N is prepared, and the bare optical fiber 1N is passed through the coating layer forming device 40 to form the resin coating layer 12 on the bare optical fiber 1N to form the optical fiber 1. May be manufactured.

Hereinafter, the content of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Example 1)
FIG. 8 is a diagram showing the coating part used in Example 1 in the same manner as FIG. 3, and FIG. 9 is a diagram showing the optical fiber manufactured in Example 1 in the same manner as in FIG. In FIG. 8, the same components as those in FIG. 3 are designated by the same reference numerals, and in FIG. 9, the same components as those in FIG. 1 are designated by the same reference numerals. The coating section 41 used in Example 1 is different from the coating section 41 exemplified in the above embodiment in that it does not have the second coating section 41S and is composed of the first coating section 41F. Using the manufacturing apparatus 100 including the coating layer forming apparatus 40 having such a coating section 41, as shown in FIG. 9, the external shape of the bare optical fiber 1N in a cross section perpendicular to the longitudinal direction is circular and the resin. An optical fiber 1 different from the optical fiber 1 illustrated in the above embodiment in that the coating layer 12 does not have the resin protective layer 15 was manufactured. Similar to the optical fiber 1 illustrated in the above embodiment, the optical fiber 1 is an amplification optical fiber having a double clad structure in which the clad 11 is an inner clad and the inner resin layer 13 is an outer clad. Specifically, the optical fiber preform 1P having a circular outer shape in a cross section in a direction perpendicular to the longitudinal direction is rotated at 250 rpm around the central axis Pa of the optical fiber preform 1P, and at 15 m/min. It was drawn at the drawing speed of. An optical fiber bare wire 1N having an outer diameter of 250 μm is formed by this drawing, and the optical fiber bare wire 1N is passed through the coating layer forming device 40 to manufacture the optical fiber 1 shown in FIG. In this example, 10 lots of the optical fiber 1 having a length of 5 km were manufactured. The pressure of the inner resin 61 filled in the second storage chamber 45 of the coating layer forming apparatus 40 is 0.10 MPa, and the pressure of the outer resin 62 filled in the third storage chamber 46 is 0.05 MPa. A stable meniscus Me was formed in the inner resin 61 stored in the storage chamber 44.

(Comparative Example 1)
FIG. 10 is a diagram showing the coating unit used in Comparative Example 1 in the same manner as in FIG. 8, and in FIG. 10, the same components as those in FIG. 8 are denoted by the same reference numerals. The coating section 41 used in Comparative Example 1 is mainly different from the coating section 41 used in Example 1 above in that the first housing chamber 44 is not formed in the first die body 43. In the second block 52 of the first die body 43 in Comparative Example 1, the first die 55 is attached to the top wall portion 52t. The first die 55 is fitted into a circular through hole formed in the top wall portion 52t and fixed to the top wall portion 52t so that the center axis thereof substantially coincides with the center axis of the second die 56. Such an internal space of the second block 52 serves as a second storage chamber 45.

Ten lots of the optical fiber 1 having a length of 5 km were manufactured in the same manner as in Example 1 except that the coating section 41 was the coating section 41 shown in FIG.

(Comparative example 2)
FIG. 11 is a diagram showing the coating unit used in Comparative Example 2 in the same manner as in FIG. 8, and in FIG. 11, the same components as those in FIG. 8 are denoted by the same reference numerals. The coating part 41 used in Comparative Example 2 mainly differs from the coating part 41 used in Example 1 above in that the second housing chamber 45 is not formed in the first die body 43 and the guide member 70 is not arranged. In the third block 53 of the first die main body 43 in this comparative example, the side wall portion 53s surrounds the side wall portion 51s while being separated from the outer peripheral surface of the side wall portion 51s of the first block 51, and the bottom wall portion 53b is in the first block 51. Is separated from the lower surface of the bottom wall portion 51b to close the lower opening of the side wall portion 53s, and the top wall portion 53t extends from the entire circumference of the upper end portion of the side wall portion 53s to the side wall portion 51s side of the first block 51. Then, the side wall 51s is connected. Such an internal space of the third block 53 serves as a third storage chamber 46. The diameter of the first die port 55H in the first block 51 is set to be substantially the same as the diameter of the second die port 56H shown in FIG.

Ten lots of the optical fiber 1 having a length of 5 km were manufactured in the same manner as in Example 1 except that the coating section 41 was the coating section 41 shown in FIG.

(Proof survival length)
Each optical fiber 1 manufactured in this manner was rewound while performing a bending test. FIG. 12 is a view showing a part of the bending test of the optical fiber. In this bending test, the optical fiber 1 is wound around a plurality of pulleys 90 to bend the optical fiber 1 in different directions in sequence. In FIG. 12, an arrow indicating the winding direction is described. The bending direction of the optical fiber 1 is eight radial directions in a cross section perpendicular to the longitudinal direction, and the two adjacent directions are shifted by approximately 45 degrees in the circumferential direction. The curvature diameter in bending of the optical fiber 1 was set to a diameter such that the stress applied to the bare optical fiber 1N when the bare optical fiber 1N was stretched by 1% was applied to the outer peripheral surface of the optical fiber 1. Then, a value obtained by dividing the total length of the optical fiber subjected to the bending test by the number of times the optical fiber was broken during the bending test was calculated as the proof survival length. The proof survival length of the optical fiber 1 of Example 1 is 10 km/time, the proof survival length of the optical fiber 1 of Comparative Example 1 is 0.2 km/time, and the proof survival length of the optical fiber 1 of Comparative Example 2 is It was 10 km/time. The proof survival length of the optical fiber 1 of Comparative Example 1 is shorter than the proof survival length of the optical fiber 1 of Example 1 and Comparative Example 2, and the optical fiber 1 of Comparative Example 1 is the optical fiber of Example 1 and Comparative Example 2. The mechanical strength was lower than 1. In the production of the optical fiber of Comparative Example 1, the bare optical fiber 1N is deflected due to the rotation of the optical fiber preform 1P, and the bare optical fiber is provided in the first die 55 of the second accommodation chamber 45. It can be considered that the outer peripheral surface of the 1N is in contact with and scratches the outer peripheral surface of the bare optical fiber 1N.

(Light leakage)
With respect to each of the optical fibers 1 manufactured in this manner, it is confirmed whether light leaks from the outer peripheral surface of the optical fiber 1 when visible light enters the clad 11 which is the inner clad from one end of the optical fiber 1. did. The optical fiber 1 of Example 1 and Comparative Example 1 did not leak light, and the optical fiber 1 of Comparative Example 2 leaked light. Observation of a portion where light leakage occurred in the optical fiber 1 of Comparative Example 2 revealed that there was a portion where the inner resin layer 13 was scarcely formed. It can be considered that this is because in manufacturing the optical fiber 1 of Comparative Example 2, the thickness of the inner resin layer 13 was uneven. On the other hand, in the manufacture of the optical fibers 1 of Example 1 and Comparative Example 1, it can be considered that unevenness in the thickness of the inner resin layer 13 and the outer resin layer 14 is suppressed.

As described above, according to the manufacturing method of the present invention, it is possible to prevent the thickness of each resin layer in the resin coating layer 12 having the inner resin layer 13 and the outer resin layer 14 from being uneven, and to form the resin coating layer 12. It was confirmed that the optical fiber 1 capable of suppressing the decrease in the mechanical strength of the optical fiber 1 even if the bare optical fiber 1N shakes at that time can be manufactured.

As described above, according to the present invention, a method for manufacturing an optical fiber and an optical fiber capable of suppressing the mechanical strength of the optical fiber from being reduced while suppressing the occurrence of unevenness in the thickness of the resin coating layer A manufacturing apparatus is provided and expected to be used in the fields of optical fiber communication, amplification optical fiber, and the like.

DESCRIPTION OF SYMBOLS 1... Optical fiber 1N... Optical fiber bare wire 1P... Optical fiber base material 10... Core 11... Clad 12... Resin coating layer 13... Inner resin layer 14... Outer resin layer 15... Resin protective layer 41... Coating section 41F... First coating section 41S... Second coating section 43... First die body 44... First storage chamber 45 ...Second accommodation chamber 46...Third accommodation chamber 47...Fourth accommodation chamber 54...Second die main body 55H...First die opening 56H...Second die opening 57H... -Third die port 58H... Fourth die port 59H... Third insertion port 61... Inner resin 62... Outer resin 63... Protective resin 70... Guide member 71... Slit P2... Drawing process P4... First resin application process P5... Second resin application process P6... Third resin application process P8... Fourth resin application process Cf... Convection Me... ..Meniscus

Claims (15)

An optical fiber having a core, a clad surrounding the outer peripheral surface of the core, and a resin coating layer including an inner resin layer coating the outer peripheral surface of the clad and an outer resin layer coating the outer peripheral surface of the inner resin layer. A manufacturing method,
A light having the core and the clad from above the first storage chamber is provided in the first storage chamber in which the upper side is open and the first die port is provided in the lower side, and the inner resin which is a part of the inner resin layer is stored. A first resin applying step of inserting a bare fiber, pulling it out from the first die opening, and applying the inner resin which is a part of the inner resin layer to the outer peripheral surface of the optical fiber bare wire;
The inner resin layer is provided in the second accommodation chamber that has the first insertion opening above and the second die opening below and is filled with the inner resin that is another part of the inner resin layer at a predetermined pressure. The optical fiber bare wire coated with the inner resin that is a part of is inserted from the first insertion opening and pulled out from the second die opening, and the inner resin that is a part of the inner resin layer is applied. A second resin applying step of applying the inner resin, which is the other part of the inner resin layer, to the outer peripheral surface of the bare optical fiber,
A third accommodating chamber having a second insertion opening on the upper side and a third die opening on the lower side and being filled with the outer resin serving as the outer resin layer at a predetermined pressure is provided with another part of the inner resin layer. The optical fiber bare wire coated with the inner resin is inserted from the second insertion opening and pulled out from the third die opening, and the inner resin serving as another part of the inner resin layer is applied. A third resin applying step of applying the outer resin to the outer peripheral surface of the bare optical fiber;
A method for manufacturing an optical fiber, comprising: A tubular guide member that surrounds the bare optical fiber is arranged apart from the outer peripheral surface of the bare optical fiber in at least the inner resin housed in the first housing chamber,
The method of manufacturing an optical fiber according to claim 1, wherein the guide member allows the inner resin to flow into a region inside the guide member. The method of manufacturing an optical fiber according to claim 2, wherein the guide member is arranged before the inner resin is stored in the first storage chamber. 4. The optical fiber according to claim 2, wherein a communication portion that communicates an outer region and an inner region of the guide member in the inner resin is formed on a side surface of the guide member. Production method. The method of manufacturing an optical fiber according to claim 1, wherein the resin forming the inner resin layer is a resin having a refractive index lower than that of the clad. The optical fiber preform is rotated around the central axis of the optical fiber preform, and a drawing step is further provided to form the bare optical fiber by drawing the optical fiber preform. Item 1. The method for producing an optical fiber according to item 1. 7. The pressure of the outer resin filled in the third storage chamber is set to be lower than the pressure of the inner resin filled in the second storage chamber. A method for manufacturing an optical fiber according to item. 8. The method of manufacturing an optical fiber according to claim 1, wherein the first die port of the first storage chamber also serves as the first insertion port of the second storage chamber. 9. The method for manufacturing an optical fiber according to claim 1, wherein the second die port of the second storage chamber also serves as the second insertion port of the third storage chamber. The optical fiber bare wire coated with the outer resin is placed in a fourth accommodation chamber having a third insertion opening above and a fourth die opening below and filled with a predetermined resin at a predetermined pressure. And a fourth resin applying step of applying the predetermined resin onto the outer peripheral surface of the bare optical fiber coated with the outer resin, the third resin applying step of inserting the third resin into the insertion opening and pulling out from the fourth die opening. The method for manufacturing an optical fiber according to claim 1, wherein An optical fiber having a core, a clad surrounding the outer peripheral surface of the core, and a resin coating layer including an inner resin layer coating the outer peripheral surface of the clad and an outer resin layer coating the outer peripheral surface of the inner resin layer. Manufacturing equipment,
A first accommodation chamber in which an upper side is opened and a lower side has a first die opening and an inner resin which is a part of the inner resin layer is stored; and a first insertion opening is formed above and a second die opening is formed in a lower side. A second storage chamber having the inner resin, which is the other part of the inner resin layer and is filled with a predetermined pressure, a second insertion port above, and a third die port below, and the outside A die main body including a third accommodating chamber filled with an outer resin serving as a resin layer at a predetermined pressure,
A bare optical fiber having the core and the clad is passed through the first storage chamber so as to pass through from the upper side to the first die port,
The optical fiber bare wire that has passed through the first storage chamber is passed through the second storage chamber so as to escape from the first insertion port to the second die port,
An apparatus for manufacturing an optical fiber, wherein the bare optical fiber that has passed through the second storage chamber is passed through the third storage chamber so as to pass through the second insertion port to the third die port. .. Further comprising a tubular guide member that surrounds the bare optical fiber with being separated from the outer peripheral surface of the bare optical fiber in the inner resin stored in at least the first housing chamber,
The optical fiber manufacturing apparatus according to claim 11, wherein the guide member allows the inner resin to flow into a region inside the guide member. The optical fiber manufacturing apparatus according to claim 12, wherein a communication portion that communicates an outer region and an inner region of the guide member in the inner resin is formed on a side surface of the guide member. .. 14. The optical fiber manufacturing apparatus according to claim 11, wherein the first die port of the first storage chamber also serves as the first insertion port of the second storage chamber. The optical fiber manufacturing apparatus according to any one of claims 11 to 14, wherein the second die port of the second storage chamber also serves as the second insertion port of the third storage chamber.

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