JPH0710613A - Manufacturing method of metal coated optical fiber - Google Patents

Abstract

PURPOSE:To prevent the lowering of tensile strength of an optical fiber by suppressing the generation of internal stress in the optical fiber in the production of a metal-coated optical fiber. CONSTITUTION:This invention relates to a method for forming a metal-coated optical fiber by forming a metal layer on the outer surface of a carbon-coated optical fiber 8. A preform composed of a core and a clad is melted by heating and spun in a drawing line for optical fiber, a carbon layer is deposited on the drawn optical fiber by chemical vapor deposition method, a resin coating layer is applied to the outer circumference of the fiber and the coated fiber is wound on a bobbin 16. The resin coating layer of the UV resin coated optical fiber 7 wound on the bobbin is removed in a separate metal plating line by using a solvent tank 21 and a piece of absorbent cotton 22. Concretely, the resin coating layer is dissolved with a solvent in the solvent tank 21 and the remaining resin coating layer on the carbon-coated optical fiber is wiped off with the absorbent cotton 22. Thereafter, a metallic layer is formed by an electroplating method. The resin coating layer is a foamed resin such as foamed polystyrene and formed urethane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal-coated optical fiber having excellent heat resistance and airtightness.

[0002]

2. Description of the Related Art When performing information communication or measurement using an optical fiber in a place having a high temperature region such as a steel mill or a nuclear power plant, the optical fiber is required to have heat resistance of several 100 ° C. to about 1000 ° C. To be done. The heat resistance of an optical fiber largely depends on the heat resistance of its coating material. Up to now, a polyimide-coated optical fiber in which polyimide is coated on the optical fiber is generally well known as a heat-resistant optical fiber, but the heat resistance of the polyimide-coated optical fiber is up to about 300 ° C. Therefore, as an optical fiber usable in a higher temperature range, a metal-coated optical fiber in which a metal is coated on the surface of the optical fiber has been actively developed.

In the case of spinning an optical fiber to apply a metal coating, it is desirable that the spinning speed of the optical fiber and the molding speed of the metal plating are the same so that the spinning and plating are consistently molded. Since the fiber spinning speed and the metal plating molding speed are different, they must be molded on separate lines.

When the lines are separated as described above, it is necessary to coat the resin layer to protect the optical fiber after forming the carbon coat layer by spinning. By coating the resin layer in this way, it is possible to prevent the strength of the optical fiber from being lowered and to improve the handleability.

However, this resin layer must be removed before applying metal plating. As a method of removing this resin layer, a method of removing it by burning the resin layer is generally used. An example of this is JP-A-58-320.
There is a "method for producing a metal-coated optical fiber" described in JP-A-41-41 and a "method for producing a metal-coated optical fiber" described in JP-A-57-106542.

Further, the optical fiber after the resin layer is removed is electroplated by using the carbon coat layer as a conductive layer. At this time, the carbon coated optical fiber as the object to be plated is energized with copper, aluminum, carbon or the like. It was done using a solid electrode.

[0007]

However, when the resin layer of the optical fiber is burned and removed by the above-mentioned conventional method, internal stress is generated in the optical fiber due to the heat at that time, and the tensile strength is lowered. There is a problem.

Further, when the carbon coated optical fiber is energized by the solid electrode during electroplating, the optical fiber is broken due to mechanical contact with the solid electrode when the optical fiber is delivered in the longitudinal direction. There is a problem in that minute cracks that cause the above are generated.

The present invention has been made in view of the above problems, and a metal coating capable of surely preventing a decrease in tensile strength due to the generation of internal stress by removing the resin layer of an optical fiber without applying heat. An object is to provide a method for manufacturing an optical fiber.

Further, the object of the present invention is to perform electroplating on a solid material in a non-contact state until at least one layer of metal is coated to prevent generation of microcracks that cause breakage, and to provide high strength. An object is to provide a metal-coated optical fiber.

[0011]

In order to solve the above-mentioned problems, the method of the present invention comprises a core for transmitting light, and a clad provided around the core and having a refractive index lower than that of the core. A method for producing a metal-coated optical fiber, wherein a metal layer is formed on the outer surface of an optical fiber consisting of: a preform consisting of the core and the clad is spun by heating and melting, and then a carbon layer is formed on the outer periphery thereof. A resin coating layer is formed and wound on a bobbin, and the resin coated optical fiber wound on the bobbin in a separate step is introduced into the plating step while the resin coating layer is dissolved and removed by a solvent.

As the resin coating the outer circumference of the optical fiber, it is preferable to use a foamed resin such as foamed polystyrene or urethane foam.

Although the carbon layer of the optical fiber is formed by the chemical vapor deposition method, it is preferable that the carbon layer is in the graphite state in consideration of the airtightness in the plating process.

Electroplating using a liquid electrode is preferable for the plating step.

When removing the resin while dissolving the resin coating layer with a solvent, it is preferable to use fibers containing a solvent. As the fiber, absorbent cotton or chemical fiber is desirable.

[0016]

First, in an optical fiber drawing step, a preform is spun into a predetermined size, and then a carbon layer and a resin coating layer are sequentially coated on the outer periphery thereof and wound on a bobbin. Next, the resin layer of the resin-coated optical fiber wound on the bobbin is dissolved and removed with a solvent, and then a metal layer is formed on the carbon-coated optical fiber by a plating process to obtain a metal-coated optical fiber.

When a resin foam such as polystyrene foam or urethane foam is used for the resin coating layer, the resin coating layer can be easily and quickly removed by a solvent. Furthermore, if the resin is wiped off using fibers such as absorbent cotton containing a solvent and chemical fibers, the resin coating layer can be reliably removed. Further, during electroplating, if the carbon coated optical fiber is energized by the liquid electrode, microcracks are not generated in the optical fiber.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

A manufacturing apparatus used in the method for manufacturing the metal-coated optical fiber of this embodiment will be described.

FIG. 1 is a schematic configuration diagram showing a plating formation line, FIG. 2 is a schematic configuration diagram showing an optical fiber production line,
FIG. 3 is a sectional view showing the structure of an optical fiber obtained by the optical fiber production line of FIG.

As shown in FIG. 3, the UV resin coated optical fiber 7 comprises a core 2 and a clad 3 surrounding the core 2, and a carbon layer 4 is formed on the outer periphery of the clad 3. Further, a UV resin coating layer 5 for protecting the carbon coating optical fiber 8 is provided on the outer periphery of the carbon layer 4.
Are formed. The resin coating layer 5 is formed of foamed resin (foamed polystyrene) in consideration of easy removal.

Reference numeral 11 in FIG. 2 is a preform of the optical fiber 1. A heating furnace 12 is provided around the preform 11 and heats the preform 11 to spin it to form the glass optical fiber 1. Reference numeral 13 is a CVD apparatus provided on the spinning side of the installed preform 11.
The carbon layer 4 is formed on the outer surface of the glass optical fiber 1 immediately after spinning by the D device 13 to obtain the carbon-coated optical fiber 8. Reference numeral 14 is a coating portion for forming the resin coating layer 5 on the outer periphery of the carbon layer 4 of the carbon coated optical fiber 8, and a styrene monomer containing a foaming agent is coated on the outer periphery of the carbon layer 4. A heating unit 15 is provided downstream of the coating unit 14 so as to surround the optical fiber 1, and forms the UV resin coating layer 5 while heating and foaming the styrene monomer coated by the coating unit 14. Reference numeral 16 is a first bobbin for winding the UV resin-coated optical fiber 7 on which the resin coating layer 5 is formed.

Reference numeral 21 in FIG. 1 denotes a solvent tank containing a solvent for removing the resin coating layer 5, which is the resin coating layer 5 on the outer periphery of the UV resin coated optical fiber 7 fed from the first bobbin 16.
Melt. 22 is absorbent cotton as a fiber for wiping off the resin coating layer 5 melted in the solvent tank 21, and contains a solvent so that the resin can be efficiently wiped off. A degreasing tank 23 degreases the outer surface of the carbon-coated optical fiber 8. A base plating tank 24 forms a base for metal plating. An electroplating bath 25 forms an electroplating metal layer on the outer surface of the base formed in the base plating bath 24. Reference numeral 26 denotes a second bobbin around which the electroplated metal-coated optical fiber 9 is wound.

Next, a method of manufacturing the metal-coated optical fiber will be described.

The preform 11 is heated in a heating furnace 12 to be melted and spun. Thereby, for example, the outer diameter is 125
A glass optical fiber 1 of μm is formed. The glass optical fiber 1 immediately after this formation is introduced into the CVD apparatus 13 to form the carbon layer 4 on the outer surface of the glass optical fiber 1.
In the carbon-coated optical fiber 8 on which the carbon layer 4 is formed by the CVD device 13, the styrene monomer containing a foaming agent is applied to the outer periphery of the carbon layer 4 by the application unit 14, and the styrene monomer is heated and foamed by the heating unit 15. Meanwhile, the UV resin coating layer 5 is formed. The carbon coated optical fiber 8 on which the resin coating layer 5 is formed is wound around the first bobbin 16. The first bobbin 16 is transferred to the plating forming line.

In the plating forming line, the UV resin coated optical fiber 7 fed from the first bobbin 16 passes through the solvent tank 21 while the resin coating layer 5 is melted,
The resin remaining on the surface of the carbon-coated optical fiber 8 is wiped off with the absorbent cotton 22. After that, degreasing is performed in the degreasing tank 23, and a metal plating base is formed in the base plating tank 24.
An electroplating metal layer is formed on the outer periphery of the base in the electroplating bath 25 and wound on the second bobbin 26. Thus, as shown in FIG. 4, a metal-coated optical fiber 9 having excellent heat resistance and airtightness, in which the metal layer 6 is coated on the outer periphery of the carbon layer 4, is obtained.

The metal-coated optical fiber obtained as described above did not generate internal stress due to heating, so that no decrease in tensile strength was observed.

Although foamed polystyrene is used as the foamed resin in the above embodiment, the same action and effect as in the above embodiment can be obtained by using urethane foam.

Although absorbent cotton is used as the fiber containing the solvent, the same action and effect as described above can be obtained by using chemical fiber.

Next, another embodiment of the method for producing a metal-coated optical fiber according to the present invention will be described. First, the process of making an optical fiber (drawing process) will be described. Quartz glass preform is heated and melted in a wire drawing furnace and spun to give an outer diameter of 12
The optical fiber is 5 μm. A carbon layer is formed on the outer circumference of this optical fiber. The carbon layer is formed by a CVD device installed on the drawing line. In the CVD apparatus, hydrocarbon is used as a raw material, and the residual heat of the optical fiber heated and melted in the drawing furnace is used as decomposition energy to form a coating by the thermal CVD method. The surface electric resistance value R of the carbon-coated optical fiber was 5 KΩ / cm.

The main purpose of the carbon layer is usually to make the quartz optical fiber, which is an insulator, have conductivity, but in this embodiment, minute cracks due to H ₂ O molecules in the plating solution described later are generated. Considering the airtight effect of preventing growth, the carbon layer was made into a graphite state. Furthermore, with the drawing line,
UV resin is applied, and ultraviolet rays are irradiated to form a UV resin-coated optical fiber having an outer diameter of 250 μm and wound on a bobbin.

Next, a plating forming step of removing the UV resin layer of the UV resin-coated optical fiber and performing electroplating of gold (Au) as a metal layer will be described. FIG. 5 shows a plating forming line. In the figure, 31 is a sending-out device for sending out the UV resin-coated optical fiber 7 wound around the bobbin in the drawing step, and the UV resin peeling tank 3 is provided on the sending line.
2, a washing tank 33 and a gold plating tank 34 are sequentially installed.

In the UV resin peeling tank 32, Solcoat # 1200 (trade name, dichloromethane 75 to 85) is used as a peeling agent.
%, Methanol 5 to 15%), and is circulated in the tank by a circulation pump. Further, cleaning water is circulated in the rinsing tank 33, and electrolytic solution (potassium gold cyanide 8%) is circulated and supplied to the gold plating tank 34 by a circulation pump, respectively. A platinum-titanium electrode (anode) 36 is immersed in the electrolytic solution in the gold plating bath 34. A liquid electrode 40 for energizing the carbon-coated optical fiber (cathode) 8 is installed on the line immediately before the gold plating bath 34, and a voltage of 3 V is applied between the platinum-titanium electrode 36 and the liquid electrode 40. DC power source 35 of is connected.

As shown in FIG. 6, the liquid electrode 40 is housed in a glass test tube 41 using mercury 42 as a liquid metal serving as the electrode. The test tube 41 has a through hole 43 slightly larger than the outer diameter of the carbon-coated optical fiber 8.
Is formed, and the carbon-coated optical fiber 8 is sent to the gold plating bath 34 through the liquid electrode 40. In addition, 37 is a copper wire connected to the power supply 35.

The UV resin-coated optical fiber 7 is sent to the UV resin peeling tank 32 from the bobbin attached to the feeding device 31, and the UV resin is chemically removed by the peeling agent in the tank 32. (Note that the removal of this UV resin did not adversely affect the carbon layer.) Then, the carbon-coated optical fiber 8 in which the carbon layer is the outermost part
Is sent to the washing tank 33, and the carbon-coated optical fiber 8 is washed away with water in the washing tank 34. Next, gold plating tank 3
4, electrolytic plating is performed, and a metal coating with a gold plating thickness of 5 μm is applied to the outer circumference of the carbon-coated optical fiber 8. The obtained metal coated optical fiber 9 was wound at a winding speed of 2 m / min.

The bending strength of the metal-coated optical fiber 9 thus obtained was determined. The measurement is performed by putting the metal-coated optical fiber 9 in a high-temperature bath at 100 ° C to 100 ° C to 500 ° C.
The temperature was raised one by one and left at each temperature for 30 minutes, taken out each time and wound around a mandrel to measure the bending strength. As a result, no rupture was observed in bending with a diameter of 10 mm or more.

After the metal coating with the liquid electrode 40 in the gold plating bath 34, further plating treatment may be performed if necessary. In this case, since the metal coating has already been formed on the outermost layer of the optical fiber, even if electroplating using the solid electrode does not cause microcracks, even if other plating treatment is used in combination. Good.

[0038]

As described above in detail, according to the manufacturing method of the present invention, the resin coating layer of the optical fiber having the following effects is dissolved by the solvent and removed. It can be removed without addition, and the decrease in tensile strength of the metal-coated optical fiber due to the generation of internal stress can be reliably prevented.

If a foamed resin such as polystyrene foam or urethane foam is used for the resin coating layer, the resin can be easily and quickly removed with a solvent, and the resin can be wiped off with a fiber such as absorbent cotton containing the solvent. In this case, the resin coating layer can be surely removed, and the production line speed is not reduced and the metal coating is not adversely affected.

In addition, when the carbon coated optical fiber is energized by the liquid electrode during the electroplating, it is possible to prevent the occurrence of minute cracks which may cause breakage in the optical fiber as in the case of the solid electrode, and it A strong metal coated optical fiber is obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a plating forming line according to a manufacturing method of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of an optical fiber production line according to the production method of the present invention.

3 is a cross-sectional view showing the structure of an optical fiber obtained by the optical fiber production line of FIG.

4 is a cross-sectional view showing a metal-coated optical fiber obtained by the plating line of FIG.

FIG. 5 is a schematic configuration diagram showing another embodiment of the plating forming line according to the manufacturing method of the present invention.

6 is a cross-sectional view showing the structure of a liquid electrode used in the plating formation line of FIG.

[Explanation of symbols]

 1 glass optical fiber 4 carbon layer 5 UV resin coating layer 6 metal layer 7 UV resin coating optical fiber 8 carbon coating optical fiber 9 metal coating optical fiber 11 preform 12 heating furnace 13 CVD device 14 coating section 15 heating section 16 first bobbin 21 solvent tank 22 absorbent cotton 24 base plating tank 25 electroplating tank 26 second bobbin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromasa Nemoto 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture, Hitachi Cable, Ltd., Optro Systems Laboratories (72) Inventor Yoshimi Nasuno Hidaka, Hitachi City, Ibaraki Prefecture 5-1-1, Machi, Hitachi Cable, Ltd. Optro System Research Center

Claims (10)

[Claims] 1. A metal coating for forming a metal layer on an outer surface of an optical fiber comprising a core for transmitting light and a clad provided around the core and having a refractive index lower than that of the core. In the method for producing an optical fiber, after spinning the preform consisting of the core and the clad by heating and melting, a carbon layer is formed, a resin coating layer is formed on the outer periphery of the carbon layer, and the bobbin is wound up in a separate step. A method for producing a metal-coated optical fiber, characterized in that the wound resin-coated optical fiber is introduced into a plating step while the resin-coated layer is dissolved in a solvent and removed. 2. The method for producing a metal-coated optical fiber according to claim 1, wherein the resin coating the outer circumference of the optical fiber is a foamed resin. 3. The method for producing a metal-coated optical fiber according to claim 2, wherein the foamed resin is polystyrene foam. 4. The method for producing a metal-coated optical fiber according to claim 2, wherein the foamed resin is urethane foam. 5. The method for producing a metal-coated optical fiber according to claim 1, wherein the carbon layer of the optical fiber is formed by a chemical vapor deposition method. Method. 6. The method for producing a metal-coated optical fiber according to claim 1, wherein the plating step is electroplating. 7. The method for producing a metal-coated optical fiber according to claim 1, wherein a fiber containing a solvent is used when removing the resin while dissolving the resin coating layer with the solvent. A method for manufacturing a metal-coated optical fiber characterized by the above. 8. The method for producing a metal-coated optical fiber according to claim 7, wherein the fiber is absorbent cotton or a chemical fiber. 9. The method for producing a metal-coated optical fiber according to claim 6, wherein during the electroplating, the optical fiber coated with the carbon layer is energized by using a liquid electrode. 10. The metal according to claim 9, wherein the liquid electrode comprises a container that contains a liquid metal serving as an electrode and has a through hole through which the optical fiber coated with the carbon layer can pass. Manufacturing method of coated optical fiber.