JPH06171987A - Production of carbon coated optical fiber - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for manufacturing a carbon-coated optical fiber which can be manufactured at low cost and at high speed. [Structure] An optical fiber 3a is passed through a carbon coating reaction vessel 5, and a carbon film is coated on the surface of the optical fiber 3a by a chemical vapor phase method using a hydrocarbon gas as a raw material in the carbon coating reaction vessel 5. Produce fiber. At this time, the fiber inlet 8 of the carbon-coated reaction vessel 5
A and the fiber outlet 8b are sealed with carbon dioxide gas or carbon tetrachloride gas.

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 carbon-coated optical fiber by passing the optical fiber through a carbon-coated reaction vessel to obtain a carbon-coated optical fiber.

[0002]

2. Description of the Related Art Carbon-coated optical fibers have excellent hydrogen permeation prevention properties and fatigue properties, and have attracted attention as practical optical fibers in order to significantly improve the long-term reliability of optical fiber cables for communication. There is.

FIG. 1 shows the structure of a carbon-coated optical fiber manufacturing apparatus for manufacturing such a carbon-coated optical fiber.

In this apparatus, the optical fiber preform 1 is heated in the drawing furnace 2 to, for example, about 2000.degree. C., and the optical fiber 3a having an outer diameter of, for example, 125 .mu.m from the heating and melting portion of the optical fiber preform 1.
Draw a line.

The optical fiber 3a thus obtained is used as an outer diameter measuring device 4
And pass through the carbon-coated reaction vessel 5. In the carbon-coated reaction vessel 5, the hydrocarbon gas supplied from the raw material gas supply port 6 is used as a raw material, which is pyrolyzed, and then the chemical gas phase method (CVD method) is applied to the surface of the clean optical fiber 3a immediately after drawing. The carbon film is coated to obtain the carbon-coated optical fiber 3b. The exhaust gas in the carbon-coated reaction vessel 5 is discharged from the exhaust port 7. The hydrocarbon gas used in the carbon-coated reaction vessel 5 at this time is often flammable such as acetylene gas, and the upper and lower fiber inlets 8a and fiber outlets 8b of the carbon-coated reaction vessel 5 are used.
When air enters from the inside, the surface temperature of the optical fiber 3a is high, which may cause an explosion and fire. Therefore, He gas is blown from the upper and lower sealing portions 9a and 9b of the carbon-coated reaction vessel 5 to the fiber inlet 8a and the fiber outlet 8b for sealing, and the optical fiber 3
A is cooled to prevent explosion and fire. That is, since the He gas has a much higher thermal conductivity than other gases and has a high cooling effect, the heat of the optical fiber 3a is taken and the thermal decomposition of the hydrocarbon gas is suppressed to prevent an explosion fire. There is.

The carbon-coated optical fiber 3b coming out of the carbon-coated reaction vessel 5 is passed through a resin coater 10 and coated with a resin such as an ultraviolet curable resin to form a carbon-coated optical fiber core wire 3c of 250 μm, for example. The carbon coated optical fiber core wire 3c is passed through a resin curing device 11 such as an ultraviolet curing furnace to cure the coating resin and then an outer diameter measuring device 12
Then, it is wound by a winder (not shown) via the take-up capstan 13.

[0007]

However, in the conventional method for producing the carbon-coated optical fiber 3b performed in the carbon-coated reaction vessel 5 as described above, since expensive He gas is used as the seal gas, the cost is increased. There is a problem that becomes.

Further, since the He gas has a much higher thermal conductivity than other gases as described above, the optical fiber 3a
However, there is a problem in that the production of the carbon-coated optical fiber cannot be promoted by taking too much heat.

An object of the present invention is to provide a method for manufacturing a carbon-coated optical fiber which is expensive and can be manufactured at high speed at low cost without using He gas which impairs the speeding up of manufacturing speed. It is in.

[0010]

Means for Solving the Problems To explain the means of the present invention for achieving the above object, the present invention is to pass an optical fiber through a carbon-coated reaction vessel and use hydrocarbon gas as a raw material in the carbon-coated reaction vessel. In the method for producing a carbon-coated optical fiber in which a carbon film is coated on the surface of the optical fiber by a chemical vapor phase method to obtain a carbon-coated optical fiber, carbon fiber gas or tetrachloride is provided at the fiber inlet and the fiber outlet of the carbon-coated reaction vessel. The carbon-coated optical fiber is manufactured while being sealed with carbon gas.

[0011]

By thus sealing the fiber inlet and the fiber outlet of the carbon-coated reaction vessel with carbon dioxide gas or carbon tetrachloride gas, the carbon-coated optical fiber can be manufactured at low cost.

Further, the carbon dioxide gas or carbon tetrachloride gas has a lower thermal conductivity than that of He gas, and the carbon-coated optical fiber can be manufactured without overcooling the optical fiber.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

First, a first embodiment of a carbon-coated optical fiber manufacturing method according to the present invention, which is carried out using the apparatus shown in FIG. 1, will be described.

In this embodiment, carbon dioxide (CO2) is supplied from the upper and lower upper seal portions 9a and lower seal portion 9b of the carbon-coated reaction vessel 5 to the fiber inlet 8a and the fiber outlet 8b.
While blowing out gas to perform sealing, a hydrocarbon gas is used as a raw material in the carbon-coated reaction vessel 5 to thermally decompose this, and the surface of the optical fiber 3a is coated with a carbon film by a chemical vapor deposition method (CVD method). Carbon coated optical fiber 3b
To get

Carbon dioxide gas is known to significantly narrow the combustion range of hydrocarbon gas among inert gases. As a result, it is safer against explosive fires than other inert gases.

Further, since carbon dioxide gas has a low thermal conductivity, it becomes possible to manufacture the carbon-coated optical fiber 3b at 500 m / min.

Further, the cost of gas is CO2: He =
It was 1: 7, which was a great reduction to 1/7.

Subsequent steps are the same as those in the conventional example described above.

Next, a second embodiment of the carbon-coated optical fiber manufacturing method according to the present invention, which is carried out by using the apparatus shown in FIG. 2, will be described. The parts corresponding to those in FIG. 1 described above are denoted by the same reference numerals.

This embodiment shows an example in which carbon tetrachloride (CCl ₄ ) gas is used as the seal gas.
In this case, since carbon tetrachloride 14 is a liquid at room temperature,
The carbon tetrachloride 14 is stored in a storage tank 15 and heated by a heater 16 to be gasified. The obtained carbon tetrachloride gas is passed through a pipe 17 which is kept warm by a heater 16 and a carbon-coated reaction vessel 5
It is supplied to the upper and lower upper seal portions 9a and 9b and is blown out from the fiber inlet 8a and the fiber outlet 8b to perform sealing. In this state, a hydrocarbon gas is used as a raw material in the carbon-coated reaction vessel 5 and is thermally decomposed to coat the surface of the optical fiber 3a with a carbon film by a chemical vapor deposition method (CVD method). To get

Since carbon tetrachloride 14 is an organic solvent and is harmful, a local exhaust device 18 is installed around the carbon coating reaction vessel 5.

The carbon tetrachloride (CCl ₄ ) gas contained in the carbon coating reaction vessel 5 is also thermally decomposed in the carbon coating reaction vessel 5. At this time, C becomes a part of the carbon film, but Cl becomes HCl. Therefore, in order to prevent air pollution, an exhaust gas treatment device 19 is connected to the exhaust port 7 for treatment.

In this way, the carbon-coated optical fiber 3
When b is manufactured, carbon tetrachloride gas has an advantage that it has a greater effect of suppressing an explosion fire than carbon dioxide gas.

[0025]

As described above, in the method for producing a carbon-coated optical fiber according to the present invention, since the fiber inlet and the fiber outlet of the carbon-coated reaction vessel are sealed with carbon dioxide gas or carbon tetrachloride gas, the cost is low. A carbon coated optical fiber can be manufactured.

Further, the carbon dioxide gas or carbon tetrachloride gas has a lower thermal conductivity than He gas, and the carbon-coated optical fiber can be manufactured more efficiently without overcooling the optical fiber.

[Brief description of drawings]

FIG. 1 is a longitudinal section showing a schematic configuration of a first embodiment of an apparatus for carrying out a carbon-coated optical fiber manufacturing method according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a second embodiment of an apparatus for carrying out the carbon-coated optical fiber manufacturing method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber base material 2 Drawing furnace 3a Optical fiber 3b Carbon coating optical fiber 3c Carbon coating optical fiber core wire 4 Outer diameter measuring instrument 5 Carbon coating reaction vessel 6 Raw material gas supply port 7 Exhaust port 8a Fiber inlet 8b Fiber outlet 9a Top seal Part 9b Lower seal part 10 Resin coating device 11 Resin curing device 12 Outer diameter measuring device 13 Collection capstan 14 Carbon tetrachloride 15 Storage tank 16 Heater 17 Piping 18 Local exhaust device 19 Exhaust gas treatment device

Claims (1)

[Claims] 1. An optical fiber is passed through a carbon-coated reaction vessel, and a carbon film is coated on the surface of the optical fiber by a chemical vapor phase method using a hydrocarbon gas as a raw material in the carbon-coated reaction vessel. In the method for producing a carbon-coated optical fiber, the carbon-coated optical fiber is produced while sealing the fiber inlet and the fiber outlet of the carbon-coated reaction vessel with carbon dioxide gas or carbon tetrachloride gas. Manufacturing method of coated optical fiber.