JP2010037127A - Method for manufacturing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical fiber for efficiently forming a carbon coat on the outer peripheral surface of a glass fiber by using a compact manufacturing apparatus even when a line speed is low. <P>SOLUTION: In a wire-drawing furnace 10, the lower end part of an optical fiber preform P is heated and softened, and is drawn to the lower side and, thereby, the glass fiber is prepared. The glass fiber is introduced into a carbon gas supply chamber 40 through a gas seal chamber 20. The glass fiber is heated by irradiation of a laser beam L in the carbon gas supply chamber 40 and the carbon coat is formed on the outer peripheral surface of the glass fiber. A heating temperature on the outer peripheral surface of the glass fiber due to the irradiation of the laser beam L is set to a temperature at which a carbon film can be produced on the outer peripheral surface of the glass fiber in the carbon gas supply chamber 40. A temperature in the carbon gas supply chamber 40 is set to be a temperature lower than the temperature at whch the carbon film can be produced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical fiber manufacturing method.

  An optical fiber in which a carbon coat is formed on the outer peripheral surface of a glass fiber is known. The carbon coat contains a lot of unsaturated bonds, has good adhesion to glass, and is a very dense coating. Since the carbon coat is very dense, the permeability of water and hydrogen is low, and the mechanical properties and hydrogen resistance properties of the glass fiber can be improved. The thickness of the carbon coat is usually very thin, 1 μm or less, and a resin coating is further applied to the outside thereof.

In addition, an optical fiber having a thermosetting resin coating (for example, polyimide) as a resin coating on the outside of the carbon coat is mainly used as a heat resistant application, for example, for measuring an optical fiber temperature distribution for searching an oil well. . When used in such a high temperature environment, a gas (H ₂ O, H _2, etc.) that can deteriorate optical fiber characteristics such as mechanical characteristics can be blocked by the carbon coat.

  An optical fiber coated with a thermosetting resin coating for heat-resistant applications is manufactured by applying a liquid resin to a glass fiber prepared by drawing an optical fiber preform, and heating and curing the resin in an oven. The In order to cure the thermosetting resin, it is necessary to hold it at a high temperature for a certain period of time. Can get worse. The drawing speed of a normal optical fiber is 1500 m / min or more, whereas the drawing speed in the case of an optical fiber coated with a thermosetting resin is as low as 5 to 10 m / min.

  On the other hand, the carbon coating is generally provided by thermally decomposing carbon gas (hydrocarbon-based or halogenated hydrocarbon-based gas) on the outer peripheral surface of a high-temperature glass fiber directly under the drawing furnace. At this time, unless the linear velocity is increased, the temperature of the outer peripheral surface of the optical fiber is lowered and no thermal decomposition reaction occurs. When the linear velocity is low, the surface temperature rapidly decreases, and when it is introduced into the carbon gas supply chamber that performs thermal decomposition, the temperature becomes lower than the lower limit temperature at which reaction can already occur.

  Thus, there is a conflicting demand regarding the linear velocity of the optical fiber between the formation of the carbon coat and the formation of the thermosetting resin coating. Therefore, it has been difficult to produce an optical fiber having both a carbon coat and a thermosetting resin coating.

Patent Document 1 discloses an invention that promotes the formation of a carbon coat by irradiating infrared light output from a lamp to increase the temperature of the glass fiber. If this invention is used, it is thought that a carbon coat can be formed on the outer peripheral surface of a glass fiber even if it is a case where a slow linear velocity is set in accordance with the formation of the thermosetting resin coating.
Japanese Patent Publication No. 61-32270

  However, in the invention disclosed in Patent Document 1, since the power density of the infrared light output from the lamp and applied to the glass fiber is low, the heating efficiency is low and the carbon coat formation efficiency is low. In order to efficiently irradiate the glass fiber with the infrared light emitted and emitted from the lamp, a reflecting mirror having a special shape may be used. However, the shape of the reflecting mirror is complicated and large.

  The present invention has been made to solve the above problems, and provides an optical fiber manufacturing method capable of forming a carbon coat on the outer peripheral surface of a glass fiber in a small size and efficiently even at a low linear velocity. The purpose is to do.

  An optical fiber manufacturing method according to the present invention is a method of manufacturing an optical fiber in which a carbon coat is formed on the outer peripheral surface of a glass fiber, and (1) a wire for drawing a glass fiber by drawing an optical fiber preform. And (2) irradiating the glass fiber produced in this drawing process with laser light to heat the glass fiber to form a carbon coat on the outer peripheral surface of the glass fiber in the carbon gas supply chamber. And a carbon coat forming step. Furthermore, in the optical fiber manufacturing method according to the present invention, in the carbon coat forming step, a heating temperature of the outer peripheral surface of the glass fiber by laser light irradiation is generated, and a carbon film is generated on the outer peripheral surface of the glass fiber in the carbon gas supply chamber. The temperature in the carbon gas supply chamber is set to a temperature lower than the temperature at which the carbon film can be formed. The optical fiber manufacturing method according to the present invention preferably further comprises a resin coating forming step of forming a polyimide resin coating on the outside of the carbon coat after the carbon coating forming step.

  According to the present invention, a carbon coat can be formed on the outer peripheral surface of a glass fiber in a small and efficient manner even at a low linear velocity.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  (First embodiment)

  Drawing 1 is a figure explaining the optical fiber manufacturing method concerning a 1st embodiment. An optical fiber manufacturing apparatus 1 used in the optical fiber manufacturing method according to the first embodiment manufactures an optical fiber F in which a carbon cord is formed on an outer peripheral surface by drawing an optical fiber preform P. . The optical fiber manufacturing apparatus 1 includes a drawing furnace 10, a gas seal chamber 20, a carbon gas supply chamber 40, and a gas seal chamber 50.

  The drawing furnace 10 heats and softens the lower end portion of the optical fiber preform P, and the lower end portion is drawn downward to produce a glass fiber. A gas seal chamber 20, a carbon gas supply chamber 40, and a gas seal chamber 50 are provided in order along the traveling path of the glass fiber.

The gas seal chamber 20 is provided below the drawing furnace 10, and the glass fiber produced in the drawing furnace 10 can pass from the top to the bottom. A gas supply pipe 21 is connected to the side surface of the gas seal chamber 20, and the inert gas G ₁ is supplied from the gas supply pipe 21 into the gas seal chamber 20. By supplying the inert gas G ₁ , the inside of the gas seal chamber 20 is set to a positive pressure, and outside air is prevented from entering the inside of the gas seal chamber 20 from the glass fiber inlet in the gas seal chamber 20.

The gas exhaust pipe 22 is provided between the gas seal chamber 20 and the carbon gas supply chamber 40. The gas exhaust pipe 22 for exhausting the exhaust gas G ₃ exiting from the outlet of the glass fiber in the gas seal chamber 20 to the outside.

The carbon gas supply chamber 40 is provided below the gas seal chamber 20, and the glass fiber that has passed through the gas seal chamber 20 can pass from top to bottom. A gas supply pipe 41 is connected to the upper part of the side surface of the carbon gas supply chamber 40, and the carbon gas G ₀ is supplied from the gas supply pipe 41 into the carbon gas supply chamber 40. Carbon gas G ₀ supplied to the interior, in a annular flow into a direction perpendicular to the fiber length axis (cyclic orifice) or more jets around the reaction tube (through a lot of holes), and carbon coating Supply the raw material to be.

Carbon gas G ₀ is a hydrocarbon or halogenated hydrocarbon gases. The hydrocarbon-based gas preferably has as few carbon atoms as possible and has many unsaturated bonds. Specific examples include acetylene, methylacetylene, propadiene, ethylene, propylene, methane, ethane, propane, and butane. The halogenated hydrocarbon gas is preferable in that it can reduce silanol groups on the glass surface. Specific examples thereof include carbon trichloride, carbon tetrachloride, ethane chloride, and propane chloride. A hydrocarbon-based gas and a halogenated hydrocarbon gas may be combined.

  A laser beam introduction window is provided on the side surface of the carbon gas supply chamber 40, and the laser beam L is incident from the outside through the laser beam introduction window. The glass fiber is irradiated with the laser beam L incident on the inside, and the glass fiber is heated. In particular, in the first embodiment, a laser beam introduction window is provided at the upper part of the side surface of the carbon gas supply chamber 40.

  The laser beam L preferably has a wavelength that makes it easy to heat the glass. For example, a laser beam having a wavelength of 10.6 μm output from a carbon dioxide laser light source is suitable. In this case, ZnSe or the like having a high transmittance is desirable as a material for the laser beam introduction window.

  The irradiation of the laser light L onto the glass fiber is preferably performed simultaneously from a plurality of directions. By doing so, the outer peripheral surface of the glass fiber can be heated uniformly and at high speed. In addition, it is preferable that the laser irradiation of the glass fiber is performed simultaneously at a plurality of positions along the longitudinal direction. By doing so, the outer peripheral surface of the glass fiber is rapidly heated to a temperature sufficient for reaction. Can be heated. Adjusting the heating temperature increases the laser energy (increasing the laser energy per beam and / or increasing the number of laser beams to irradiate (increase the number of irradiated spots)), and adjust the focal position of the lens for each beam. Etc.

  The carbon gas supply chamber 40 may have a heating furnace. In this case, the temperature inside the carbon gas supply chamber 40 is set to a temperature (for example, 200 ° C. to 700 ° C.) lower than the temperature at which the carbon film can be generated by heating with the heating furnace.

A gas exhaust pipe 42 is connected to the lower part of the side surface of the carbon gas supply chamber 40, and the exhaust gas G ₄ is exhausted from the gas exhaust pipe 42 to the outside.

  In this carbon gas supply chamber 40, an optical fiber F having a carbon coat formed on the outer peripheral surface of the glass fiber is formed, and this optical fiber F is discharged below the carbon gas supply chamber 40.

The gas seal chamber 50 is provided below the carbon gas supply chamber 40, and the fiber F that has passed through the carbon gas supply chamber 40 can pass from top to bottom. A gas supply pipe 51 is connected to the side surface of the gas seal chamber 50, and the inert gas G ₂ is supplied from the gas supply pipe 51 into the gas seal chamber 50. This supply of inert gas G ₂ is inside the gas seal chamber 50 is a positive pressure, the outside air from the outlet of the fiber F in the gas seal chamber 50 is prevented from entering the interior of the gas seal chamber 50.

  In the optical fiber manufacturing method according to the first embodiment, the optical fiber manufacturing apparatus 1 is used, and the optical fiber F is manufactured as follows. In the drawing furnace 10, the lower end portion of the optical fiber preform P is heated and softened, and the lower end portion is drawn downward to produce a glass fiber (drawing step). The glass fiber produced in this drawing process is introduced into the carbon gas supply chamber 40 through the gas seal chamber 20.

  In the carbon gas supply chamber 40, the glass fiber is heated by irradiation with the laser beam L. At this time, the heating temperature of the outer peripheral surface of the glass fiber by the irradiation with the laser light L is set to a temperature at which a carbon film can be formed on the outer peripheral surface of the glass fiber in the carbon gas supply chamber 40 (depending on the carbon gas used). Is done. The temperature in the carbon gas supply chamber 40 is set to a temperature lower than the temperature at which the carbon film can be generated. When acetylene gas is used as the carbon gas, the energy of the laser beam L irradiated is adjusted so that the temperature of the outer peripheral surface of the glass fiber is 700 ° C. or higher and 900 ° C. or lower in the carbon gas supply chamber 40. For example, the power of the laser beam is adjusted, or the power is adjusted by changing the lens position, that is, the focal position. At this time, temperature management is performed while monitoring the temperature. Moreover, when using acetylene, the temperature in the carbon gas supply chamber 40 shall be less than 700 degreeC.

  Thus, a carbon coat is formed on the outer peripheral surface of the glass fiber in the carbon gas supply chamber 40 (carbon coat forming step). The optical fiber F on which the carbon coat has been formed in this carbon coat formation process passes through the gas seal chamber 50, and then a polyimide resin is further formed (resin coating formation process).

  Thus, in this embodiment, since the glass fiber is heated by irradiation with the laser beam L, the following effects can be obtained as compared with the invention described in Patent Document 1 in which heating is performed by infrared irradiation. That is, since the power density of the laser light is high, the glass fiber is heated at a high speed, and the heating speed can be adjusted by adjusting the irradiation intensity. Therefore, it is possible to deal with a wide range of glass fiber linear velocities. Since the carbon coat can be formed on the outer peripheral surface of the glass fiber even at a low linear velocity, a resin coating forming process can be performed subsequent to the carbon coat forming process.

  In addition, it is easy to design an optical system for condensing and irradiating laser light onto a glass fiber. For example, a mirror and a lens may be provided on the optical path from the laser light source. Furthermore, since the heating system is fast and the optical system is simple, even if laser light irradiation is performed simultaneously at a plurality of positions along the longitudinal direction of the glass fiber, the number of irradiation positions may be small. Can be miniaturized.

  In particular, in the first embodiment, the glass fiber is heated by the irradiation of the laser beam L in the carbon gas supply chamber 40, and therefore, when the required temperature is reached, a carbon cord is formed by a thermal decomposition reaction. Therefore, it is easy to control the formation of the carbon coat. In the first embodiment, the laser light is applied to the glass fiber in the carbon gas supply chamber and directly above the heating source 43. Carbon gas is supplied around the glass fiber at the location where the laser beam is irradiated.

  The heating source 43 may heat the glass fiber so as not to lower the temperature of the outer peripheral surface as much as possible. However, the film quality of the carbon coat changes depending on the temperature. Quality deteriorates. When carbon gas is acetylene, it is preferable that the temperature of the outer peripheral surface of a glass fiber is 700 to 900 degreeC. Moreover, when carbon gas is ethylene, it is preferable that the temperature of the outer peripheral surface of a glass fiber is 1200 to 1400 degreeC.

  A good-quality carbon coat contains many graphite structures in amorphous carbon, contains many unsaturated bonds, has good adhesion to glass, and is dense. A high-quality carbon coat is also obtained by depositing low molecular weight carbon. In contrast, an improper carbon coat is brittle with few unsaturated bonds and therefore poor mechanical strength. High-carbon carbon (soot) deposited is also an inappropriate carbon coat. This soot is generated by the gas phase reactivity of the high temperature gas, or is attached by the reaction at the high temperature tube wall. In the present embodiment, the temperature in the carbon gas supply chamber 40 is lowered so that carbon is not generated except on the outer peripheral surface of the glass fiber.

  (Second Embodiment)

  FIG. 2 is a view for explaining an optical fiber manufacturing method according to the second embodiment. An optical fiber manufacturing apparatus 2 used in the optical fiber manufacturing method according to the second embodiment manufactures an optical fiber F in which a carbon cord is formed on an outer peripheral surface by drawing an optical fiber preform P. . The optical fiber manufacturing apparatus 2 includes a drawing furnace 10, a gas seal chamber 20, a carbon gas supply chamber 40, and a gas seal chamber 50.

  Compared with the configuration of the optical fiber manufacturing apparatus 1 shown in FIG. 1, the optical fiber manufacturing apparatus 2 shown in FIG. 2 irradiates the glass fiber with the laser light L in the carbon gas supply chamber 40. The difference is that a laser beam introduction window is provided near the center of the side surface of the carbon gas supply chamber 40 and at a location where the heating source 43 is located. That is, when the carbon gas supply chamber 40 has the heating source 43, a laser beam introduction hole is provided in the heating source 43. The laser beam L enters the carbon gas supply chamber 40 through the laser beam introduction hole and the laser beam introduction window. The glass fiber is irradiated with the laser beam L incident on the inside, and the glass fiber is heated.

  The optical fiber manufacturing method according to the second embodiment can achieve the same effects as the optical fiber manufacturing method according to the first embodiment. In particular, in the second embodiment, the glass fiber is heated by the irradiation of the laser beam L in the carbon gas supply chamber 40, so that a carbon cord is formed by a thermal decomposition reaction as soon as the required temperature is reached. Therefore, it is easy to control the formation of the carbon coat.

  (Third embodiment)

  FIG. 3 is a view for explaining an optical fiber manufacturing method according to the third embodiment. An optical fiber manufacturing apparatus 3 used in the optical fiber manufacturing method according to the third embodiment manufactures an optical fiber F in which a carbon cord is formed on an outer peripheral surface by drawing an optical fiber preform P. . The optical fiber manufacturing apparatus 3 includes a drawing furnace 10, a gas seal chamber 20, a laser beam irradiation chamber 30, a carbon gas supply chamber 40, and a gas seal chamber 50.

  Compared with the configuration of the optical fiber manufacturing apparatus 1 shown in FIG. 1, the optical fiber manufacturing apparatus 3 shown in FIG. 3 includes a laser light irradiation chamber 30 between the gas seal chamber 20 and the carbon gas supply chamber 40. It differs in that it is provided. In the laser light irradiation chamber 30, the glass fiber that has passed through the gas seal chamber 20 can pass from top to bottom. A laser beam introduction window is provided on the side surface of the laser beam irradiation chamber 30, and the laser beam L is incident from the outside through the laser beam introduction window. The glass fiber is irradiated with the laser beam L incident on the inside, and the glass fiber is heated.

  In the optical fiber manufacturing method according to the third embodiment, the optical fiber manufacturing apparatus 3 is used, and the optical fiber F is manufactured as follows. In the drawing furnace 10, the lower end portion of the optical fiber preform P is heated and softened, and the lower end portion is drawn downward to produce a glass fiber (drawing step). The glass fiber produced in this drawing step is heated by irradiation with the laser beam L when passing through the laser beam irradiation chamber 30 through the gas seal chamber 20 and further introduced into the carbon gas supply chamber 40. .

  At this time, the heating temperature of the outer peripheral surface of the glass fiber by irradiation with the laser light L is set to a temperature at which a carbon film can be generated on the outer peripheral surface of the glass fiber in the carbon gas supply chamber 40. The temperature in the carbon gas supply chamber 40 is set to a temperature lower than the temperature at which the carbon film can be generated.

  Thus, a carbon coat is formed on the outer peripheral surface of the glass fiber in the carbon gas supply chamber 40 (carbon coat forming step). The optical fiber F on which the carbon coat has been formed in this carbon coat formation process passes through the gas seal chamber 50, and then a polyimide resin is further formed (resin coating formation process).

  (Fourth embodiment)

  FIG. 4 is a view for explaining an optical fiber manufacturing method according to the fourth embodiment. An optical fiber manufacturing apparatus 4 used in the optical fiber manufacturing method according to the fourth embodiment manufactures an optical fiber F in which a carbon cord is formed on an outer peripheral surface by drawing an optical fiber preform P. . The optical fiber manufacturing apparatus 4 includes a drawing furnace 10, a carbon gas supply chamber 40, and a gas seal chamber 50.

  Compared with the configuration of the optical fiber manufacturing apparatus 1 shown in FIG. 1, the optical fiber manufacturing apparatus 4 shown in FIG. 4 has a laser beam for the glass fiber between the drawing furnace 10 and the gas seal chamber 20. It is different in that L is irradiated.

  In the optical fiber manufacturing method according to the fourth embodiment, the optical fiber manufacturing apparatus 4 is used, and the optical fiber F is manufactured as follows. In the drawing furnace 10, the lower end portion of the optical fiber preform P is heated and softened, and the lower end portion is drawn downward to produce a glass fiber (drawing step). The glass fiber produced in this drawing process is heated by irradiation with the laser beam L, and is introduced into the carbon gas supply chamber 40 through the gas seal chamber 20.

  At this time, the heating temperature of the outer peripheral surface of the glass fiber by irradiation with the laser light L is set to a temperature at which a carbon film can be generated on the outer peripheral surface of the glass fiber in the carbon gas supply chamber 40. The temperature in the carbon gas supply chamber 40 is set to a temperature lower than the temperature at which the carbon film can be generated.

  Thus, a carbon coat is formed on the outer peripheral surface of the glass fiber in the carbon gas supply chamber 40 (carbon coat forming step). The optical fiber F on which the carbon coat has been formed in this carbon coat formation process passes through the gas seal chamber 50, and then a polyimide resin is further formed (resin coating formation process).

It is a figure explaining the optical fiber manufacturing method concerning a 1st embodiment. It is a figure explaining the optical fiber manufacturing method which concerns on 2nd Embodiment. It is a figure explaining the optical fiber manufacturing method which concerns on 3rd Embodiment. It is a figure explaining the optical fiber manufacturing method which concerns on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1-4 ... Optical fiber manufacturing apparatus, 10 ... Drawing furnace, 20 ... Gas seal chamber, 21 ... Gas supply pipe, 22 ... Gas exhaust pipe, 30 ... Laser beam irradiation chamber, 40 ... Carbon gas supply chamber, 41 ... Gas supply pipe, 42 ... gas exhaust pipe, 43 ... heat source, 50 ... gas seal chamber 51: gas supply pipe, P ... optical fiber preform, F ... optical fiber, G 0 _... carbon _gas, G 1, _{G 2} ... inert gas, _{G 3, G} 4 _... exhaust gases, L ... laser light.

Claims (2)

A method of manufacturing an optical fiber having a carbon coat formed on the outer peripheral surface of a glass fiber,
A drawing step of drawing an optical fiber preform to produce a glass fiber;
A carbon coat forming step of heating the glass fiber by irradiating the glass fiber produced in this drawing step with a laser beam, and forming a carbon coat on the outer peripheral surface of the glass fiber in a carbon gas supply chamber;
With
In the carbon coat forming step,
The heating temperature of the outer peripheral surface of the glass fiber by laser light irradiation is set to a temperature at which a carbon film can be generated on the outer peripheral surface of the glass fiber in the carbon gas supply chamber,
The temperature in the carbon gas supply chamber is set to a temperature lower than the temperature at which a carbon film can be generated.
An optical fiber manufacturing method. The optical fiber manufacturing method according to claim 1, further comprising a resin coating forming step of forming a polyimide resin coating on the outside of the carbon coat after the carbon coating forming step.

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