JPH07206476A - Production of hermetically coated optical fiber - Google Patents

Abstract

PURPOSE:To produce a hermetically coated optical fiber by preventing degradation in concn. of a gaseous raw material on the surface of the optical fiber in a reaction furnace. CONSTITUTION:The hermetically coated optical fiber is produced by bringing the gaseous raw material supplied into the reaction furnace 5 into optical reaction and coating the surface of the optical fiber with a hermetic film while passing the optical fiber into the reaction furnace 5. At this time, the flow of the gaseous raw material at least near the surface of the optical fiber is disturbed within the reaction furnace 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hermetic coating for producing a hermetically coated optical fiber by chemically reacting a raw material gas supplied into a reactor to coat a surface of an optical fiber passing through the reactor with a hermetic film. The present invention relates to a method for manufacturing an optical fiber.

[0002]

2. Description of the Related Art As a conventional method for manufacturing a hermetically coated optical fiber of this type, the surface of an optical fiber immediately after drawing is coated with a hermetic film made of an inorganic material layer of 200 to 1000 angstroms by a thermal CVD method. It is known to manufacture optical fibers.

As a hermetic film obtained by such a manufacturing method, a carbon film made of carbon or a carbon compound is well known. The carbon film is formed on the surface of the optical fiber by thermally decomposing the raw material gas.
Since such a carbon film almost completely prevents H ₂ from penetrating, stress corrosion due to H ₂ O found in quartz glass does not occur, and naturally fatigue characteristics are remarkably improved. Furthermore,
Carbon-coated optical fibers having an initial strength equal to or higher than that of ordinary optical fibers can be manufactured, and are now being used in fields such as communication lines and optical components.

FIG. 10 and FIG. 11 show a schematic structure of an apparatus for carrying out the conventional method for manufacturing a hermetically coated optical fiber of this type.

That is, conventionally, GeO ₂ is provided in a drawing furnace 2 having a heater 1 such as a carbon heater, for example, in a core portion.
A portion of the optical fiber preform 3 to which is added as a dopant is disposed on the tip side, and an optical fiber 4a having an outer diameter of 125 μm is drawn from the tip of the optical fiber preform 3 heated and melted by the heater 1 to obtain The optical fiber 4a thus obtained is passed through the reaction furnace 5.

A partition 6 is provided above and below the reactor 5.
a and 6b are provided to form the seal chambers 7a and 7b, and a seal gas such as Ar gas is supplied to the seal chambers 7a and 7b from the upper seal gas supply port 8a and the lower seal gas supply port 8b, respectively. Fiber passage holes 9a, 10a, 9
Prevents outside air from entering b and 10b. Partition body 6a
A raw material gas consisting of a hydrocarbon gas such as acetylene is supplied into the reaction furnace 5 from the raw material gas supply port 11 provided immediately below the reactor, and the raw material gas is supplied as a laminar flow along the optical fiber 4a passing through the center of the reaction furnace 5. Flow the source gas. At this time, the optical fiber 4a
Is in a heating state immediately after drawing, and the heat causes the raw material gas to undergo a chemical reaction (in the case where the hermetic film is a carbon film, the raw material gas is thermally decomposed) and the surface of the optical fiber 4a passing through the reaction furnace 5. Is hermetically coated with a hermetic film to form a hermetically coated optical fiber 4b. The gas descending in the reaction furnace 5 is exhausted to the outside through an exhaust port 12 provided directly above the partition 6b.

The hermetically coated optical fiber 4b obtained in the reaction furnace 5 has its outer diameter measured by an outer diameter measuring device 13 and then passed through a resin coater 14 to coat its surface with a resin, for example, having an outer diameter of 250. It becomes the optical fiber core wire 4c of μm.

The optical fiber core wire 4c thus obtained is passed through a resin curing furnace 15 to cure the coating resin, and then the outer diameter measuring device 1
Measure the outer diameter with 6 and then take off the capstan 17
While taking it up, it is wound up by a winding machine (not shown).

[0009]

In such a conventional method for manufacturing a hermetically coated optical fiber, the raw material gas flows as a laminar flow along the surface of the optical fiber 4a in the reaction furnace 5, and a chemical reaction occurs in the process. Since a hermetic film is formed on the surface of the optical fiber 4a, the concentration of the raw material gas will decrease toward the downstream side. At the part of the optical fiber 4a where the concentration of the raw material gas is lowered,
There is a problem that the reaction rate decreases, and the film forming rate of the hermetic film significantly decreases on the downstream side in the reaction furnace 5. Further, in the conventional method, of the source gases supplied into the reaction furnace 5, only the gas flowing near the optical fiber 4a is used for forming the hermetic film, and most of the other source gases are used. Was exhausted as an exhaust gas to the outside of the reaction furnace 5, and there was a problem that the utilization efficiency of the raw material gas was poor. Further, in the conventional method, if the thickness of the hermetic film on the surface of the hermetically coated optical fiber 4b cannot be made to be a predetermined thickness for the above reason, a large amount of source gas is supplied into the reaction furnace 5, or Alternatively, although the length of the reaction furnace 5 was increased, the former had a problem that the utilization efficiency of the raw material gas was further deteriorated, and the latter had a problem that the apparatus was enlarged.

It is an object of the present invention to provide a method for producing a hermetically coated optical fiber which can prevent the concentration of the raw material gas on the surface of the optical fiber in the reaction furnace from decreasing.

Another object of the present invention is to provide a method for producing a hermetically coated optical fiber which can prevent a decrease in the raw material gas concentration on the surface of the optical fiber in the reaction furnace without using a consuming means such as an inert gas. To provide.

Another object of the present invention is to provide a method for producing a hermetically coated optical fiber which can prevent a decrease in the raw material gas concentration on the surface of the optical fiber in a reaction furnace by using gas.

[0013]

The means of the present invention for achieving the above object will be described below.

The present invention is a hermetic for producing a hermetically coated optical fiber by causing a raw material gas supplied into the reactor to undergo a chemical reaction to coat the surface of the optical fiber with a hermetic film while passing the optical fiber through the reactor. The target is a method of manufacturing a coated optical fiber.

The present invention is characterized in that, in such a method for producing a hermetically coated optical fiber, the flow of the source gas at least near the surface of the optical fiber is disturbed in the reaction furnace.

The present invention also provides a method for manufacturing a hermetically coated optical fiber as described above, wherein a raw material gas flow disturbing member is provided in the reaction furnace so as to project in a direction intersecting the flow direction of the raw material gas. It is characterized in that the flow disturbing device disturbs the flow of the raw material gas at least near the surface of the optical fiber.

In this case, as the raw material gas flow disturbing device,
A ring-shaped disk, a fiber through hole is provided in the center thereof, and a plurality of gas passage holes are provided in the raw material gas flow disturbing device around the fiber through hole, which projects into the reactor. Thing consisting of protrusions and irregularities, or by changing the inner diameter of the reaction furnace to a small taper in the longitudinal direction,
It can be configured by a stirring tool such as a fan.

Further, the present invention is characterized in that the gas is blown into the reaction furnace from a gas blowing portion provided in the longitudinal direction of the reaction furnace to disturb the flow of the raw material gas at least near the surface of the optical fiber. To do.

In this case, as the gas, an inert gas such as Ar gas or nitrogen gas, or a raw material gas is used.

Further, the present invention is characterized in that a vibrating body is provided in the reaction furnace, and the flow of the raw material gas at least near the surface of the optical fiber is disturbed by the vibration of the vibrating body.

[0021]

When the flow of the source gas at least near the surface of the optical fiber is disturbed in the reaction furnace as in the present invention, the concentration of the source gas near the surface of the optical fiber can be prevented from lowering. Therefore, the reaction speed becomes faster, and it is possible to prevent the film formation speed from decreasing.
A hermetically coated optical fiber can be manufactured efficiently in a short time. Further, according to the present invention, the utilization efficiency of the raw material gas can be improved. Furthermore, according to the present invention, it is possible to minimize the size increase of the reaction furnace.

Further, for example, a raw material gas flow disturbing tool which projects in a direction intersecting with the flow direction of the raw material gas is provided in the reaction furnace, and the raw material gas flow disturbing tool at least near the surface of the optical fiber is used. If the flow is disturbed, it is possible to prevent the concentration of the raw material gas on the surface of the optical fiber in the reaction furnace from decreasing without using a means for consuming the gas or the like. If no means for consuming gas or the like is used, the hermetically coated optical fiber can be manufactured at low cost.

As the raw material gas flow disturbing device, a ring-shaped disk is provided, a fiber through hole is provided at the center thereof, and the raw material gas flow disturbing device around the fiber through hole is provided with a plurality of gas passing holes. With the structure described above, the flow of the raw material gas can be disturbed at least in the vicinity of the surface of the optical fiber so as not to obstruct the flow of the raw material gas as much as possible.

The raw material gas flow disturbing device can be easily constructed by using a protrusion or projections and projections protruding into the reaction furnace as the raw material gas flow disturbing device.

If the material for disturbing the flow of the raw material gas is formed by tapering the inner diameter of the reaction furnace in the longitudinal direction, it can be carried out without complicating the structure of the reaction furnace.

When a stirring tool such as a fan is used as the raw material gas flow disturbing tool, the disturbance of the flow of the raw material gas can be appropriately selected by changing the movement of the stirring tool.

Further, when the flow of the raw material gas at least near the surface of the optical fiber is disturbed by blowing the gas into the reaction furnace from the gas blowing portion provided in the longitudinal direction of the reaction furnace, the gas is used for the optical fiber. The flow of the raw material gas near the surface of can be disturbed. In this case, since the tool for disturbing the raw material gas flow protruding into the reactor is not used, the problem of cleaning due to the adherence of the reaction product to the disturber for the raw material gas flow is avoided and the hermetic coating is performed. An optical fiber can be manufactured.

In this case, if an inert gas is used as the gas blown into the reaction furnace from the gas blowing section, no reaction occurs even if mixed with the raw material gas, and the formation of the hermetic film is not adversely affected. It is possible to prevent the concentration of the raw material gas near the surface from decreasing.

Further, when the raw material gas is used as the gas blown into the reaction furnace from the gas blowing portion, the raw material gas having a high concentration can be newly replenished in the vicinity of the surface of the optical fiber, and the raw material gas can be supplied as compared with the case of using the inert gas. The hermetic film can be formed more efficiently while preventing the concentration from decreasing.

Further, by providing a vibrating body in the reaction furnace and disturbing the flow of the raw material gas at least near the surface of the optical fiber by the vibration of the vibrating body, it is possible to prevent the concentration of the raw material gas near the surface of the optical fiber from lowering. Therefore, the reaction speed becomes faster,
It is possible to prevent the film formation rate from decreasing, and it is possible to efficiently manufacture the hermetically coated optical fiber in a short time. In this case, by appropriately selecting the frequency of the ultrasonic vibrator, the raw material gas in the reaction furnace can be efficiently stirred.

In the method for manufacturing a hermetically coated optical fiber by vibrating the vibrating body, a raw material gas flow disturbing tool is used, or gas is blown into the reaction furnace from the gas blowing part to cause the gas near the surface of the optical fiber. When used in combination with the method of disturbing the flow of the raw material gas, these raw gas flow disruptors are used, or a method of disturbing the flow of the raw material gas near the surface of the optical fiber by blowing gas from the gas blowing part into the reaction furnace is used. The method for producing a hermetically coated optical fiber can be carried out more efficiently than when it is performed alone. In addition, if an inert gas is used by the method of disturbing the flow of the raw material gas in the vicinity of the surface of the optical fiber by injecting the gas into the reaction furnace from the gas blowing part, it is possible to reduce the amount of the inert gas used. it can.

[0032]

Embodiments of the present invention will now be described in detail with reference to the drawings. In addition, in the portion corresponding to FIG. 11 described above,
The same reference numerals are given. In each of the embodiments, the structure of the reaction furnace 5 for forming a hermetic film, which constitutes the essential part of the invention, is shown. Other configurations are similar to those in FIG. 10 described above.

FIGS. 1 and 2 show a first embodiment of an apparatus for carrying out the method for manufacturing a hermetically coated optical fiber according to the present invention. The reactor 5 used in the hermetically coated optical fiber manufacturing apparatus of this embodiment has a length from the upper optical fiber passage hole 10a to the exhaust port 12 of 250.
mm, and the upper optical fiber passage hole 10 is provided in the reactor 5.
At a position 150 mm from a, there is provided a raw material gas flow disturbing device 18 made of a ring-shaped disk protruding in a direction intersecting with the flow direction of the raw material gas. The raw material gas flow disturbing device 18 made of the ring-shaped disk has a diameter of 30 mm, a fiber through hole 18a having a diameter of 10 mm is provided in the center thereof, and the raw material gas flow disturbing device 18 around the fiber through hole 18a is provided. Has a structure in which eight gas passage holes 18b having a diameter of 8 mm are provided.

When the hermetically coated optical fiber is manufactured by the apparatus for manufacturing the hermetically coated optical fiber using the reactor 5, the upper part to the lower part along the optical fiber 4a penetrating the axial center of the reactor 5 are manufactured. A raw material gas is flowed as a laminar flow. The raw material gas hits the raw material gas flow disturbing tool 18 in the course of flowing down and disturbs the flow of the raw material gas at least near the surface of the optical fiber 4a.

With this, that is, by stirring the raw material gas, it is possible to prevent the concentration of the raw material gas near the surface of the optical fiber 4a from decreasing. Therefore, the reaction speed becomes faster, the film formation speed can be prevented from lowering, and the hermetically coated optical fiber 4b can be efficiently manufactured in a short time. In particular, when the raw material gas flow disturbing tool 18 as in this embodiment is used, the raw material gas concentration on the surface of the optical fiber 4a in the reaction furnace 5 can be changed without using a means for consuming the gas described later. It can prevent the deterioration.
Therefore, the hermetically coated optical fiber can be manufactured at low cost.

Table 1 shows the manufacturing conditions and characteristic test results of the first embodiment.

FIGS. 3 and 4 show a second embodiment of an apparatus for carrying out the method for manufacturing a hermetically coated optical fiber according to the present invention. The reaction furnace 5 used in the hermetically coated optical fiber manufacturing apparatus of this embodiment also has a length from the upper optical fiber passage hole 10a to the exhaust port 12 of 250.
mm, and the upper optical fiber passage hole 10 is provided in the reactor 5.
Four gas blowing portions 19 are provided at a position of 150 mm from a at intervals of 90 ° in the circumferential direction. These gas blowing portions 19 are provided so as to blow gas into the inner circumference of the reaction furnace 5 in a tangential direction and obliquely downward.

When the hermetically coated optical fiber is manufactured by the apparatus for manufacturing the hermetically coated optical fiber using the reactor 5, the upper part to the lower part along the optical fiber 4a penetrating the axial center of the reactor 5 are manufactured. A raw material gas is flowed as a laminar flow. During the process in which the source gas flows down, Ar gas, which is a kind of inert gas, is tangentially and obliquely downwardly directed from each gas blowing portion 19 to the inner circumference of the reaction furnace 5, for example.
The Ar gas is blown in at a rate of 0.5 l / min to disturb the flow of the raw material gas at least near the surface of the optical fiber 4a.

As a result, the raw material gas is agitated to prevent the concentration of the raw material gas near the surface of the optical fiber 4a from decreasing. Therefore, the reaction speed becomes faster, the film formation speed can be prevented from lowering, and the hermetically coated optical fiber 4b can be efficiently manufactured in a short time. In particular, when the gas blowing section 19 as in this embodiment is used, the raw material gas flow disturbing tool 18 or the like protruding into the reaction furnace 5 is not used, so that the raw material gas flow disturbing tool 18 or the like reacts. The hermetically coated optical fiber 4b can be manufactured while avoiding the problem of cleaning due to the adhesion of the product.

Table 1 shows the manufacturing conditions and the characteristic test results of the second embodiment.

5 to 7 show a third embodiment of an apparatus for carrying out the method for manufacturing a hermetically coated optical fiber according to the present invention. The reactor 5 used in the hermetically coated optical fiber manufacturing apparatus of this embodiment is an example in which the first embodiment shown in FIGS. 1 and 2 and the second embodiment shown in FIGS. 3 and 4 are combined. It is shown. In this case, the gas blowing portion 19 is provided on the upstream side (upper side) of the raw material gas flow disturbing tool 18.

Thus, by combining the first embodiment shown in FIGS. 1 and 2 with the second embodiment shown in FIGS. 3 and 4, it is possible to further reduce the concentration of the raw material gas near the surface of the optical fiber 4a. It can be prevented further.

In particular, the gas blowing portion 19 is provided upstream of the raw material gas flow disturbing tool 18 in this manner, and the inert gas is tangentially and obliquely downwardly directed from the gas blowing portion 19 to the inner circumference of the reaction furnace 5. When blown, a part of the inert gas that swirls and descends along the inner circumference of the reaction furnace 5 cleans the upper surface of the raw material gas flow disturbing tool 18 and the surfaces of the holes 18a and 18b. It is possible to prevent reaction products from adhering to the disturbing tool 18, and reduce the number of times of cleaning the raw material gas flow disturbing tool 18.

FIG. 8 shows a fourth embodiment of an apparatus for carrying out the method for manufacturing a hermetically coated optical fiber according to the present invention. Also in the reactor 5 used in the apparatus for manufacturing the hermetically coated optical fiber of the present embodiment, the length from the upper optical fiber passage hole 10a to the exhaust port 12 is 250 mm.
There is an optical fiber passage hole 10a in the upper part of the reactor 5.
One gas blowing part 20 is provided at a position of 150 mm from. The gas blowing section 20 is provided so as to blow gas onto the optical fiber 4a passing through the reaction furnace 5.

When the hermetically coated optical fiber is manufactured by the hermetically coated optical fiber manufacturing apparatus using the reaction furnace 5, the optical fiber 4a passing through the reactor 5 penetrates the axial center of the reactor 5. The raw material gas is made to flow as a laminar flow from the upper part to the lower part along the optical fiber 4a. In the process of flowing the raw material gas, the raw material gas is blown into the reaction furnace 5 from the gas blowing portion 20 toward the optical fiber 4a,
The raw material gas disturbs the flow of the raw material gas at least near the surface of the optical fiber 4a.

As a result, the source gas having a high concentration is supplied near the surface of the optical fiber 4a, and the concentration of the source gas near the surface of the optical fiber 4a can be prevented from lowering. Particularly, in this case, since the raw material gas having a high concentration is newly blown from the gas blowing portion 20, the raw material gas concentration near the surface of the optical fiber 4a is increased. Therefore, A which is an inert gas
The reaction rate is faster than in the second embodiment in which r gas is blown,
The hermetically coated optical fiber 4b can be manufactured efficiently in a shorter time than in the second embodiment. Also in the case of this embodiment,
Since the raw material gas flow disturbing tool 18 or the like protruding into the reaction furnace 5 is not used, the hermetically coated optical fiber 4b can be avoided by avoiding the problem of cleaning caused by the reaction products adhering to the raw material gas flow disturbing tool 18 or the like. Can be manufactured.

Table 1 shows the manufacturing conditions and characteristic test results of the fourth embodiment.

In this case as well, similar to the third embodiment, it can be implemented in combination with the first embodiment. By doing so, the raw material gas is blown from the upstream gas blowing portion 19, so that the hermetically coated optical fiber 4b can be manufactured more efficiently than in the third embodiment.

FIG. 9 shows a fifth embodiment of an apparatus for carrying out the method for manufacturing a hermetically coated optical fiber according to the present invention. In the reactor 5 of the apparatus for manufacturing a hermetically coated optical fiber according to the present embodiment, an ultrasonic oscillator 22 is attached as an oscillator to the outer wall in the middle in the longitudinal direction.

When a hermetically coated optical fiber is manufactured by the apparatus for manufacturing a hermetically coated optical fiber using such a reactor 5, the optical fiber 4a passing through the reactor 5 is penetrated through the axial center of the reactor 5. The raw material gas is made to flow as a laminar flow from the upper part to the lower part along the optical fiber 4a. At this time, by operating the ultrasonic oscillator 22 to ultrasonically vibrate the reaction furnace 5 and stir the raw material gas in the reaction furnace 5, the raw material flowing in a laminar flow near the surface of the optical fiber 4a. The raw material gas is supplied to the gas phase portion having a low gas concentration from the gas phase portion having a high concentration outside thereof.

As a result, the raw material gas can be agitated to prevent a decrease in the raw material gas concentration near the surface of the optical fiber 4a.
Particularly, in this case, by appropriately selecting the frequency of the ultrasonic vibrator 22, the raw material gas in the reaction furnace 5 can be efficiently stirred.

When the method of manufacturing the hermetically coated optical fiber by vibrating the vibrating body 22 is used in combination with the methods of the first, second, third and fourth embodiments, the methods of these respective embodiments are more efficient. It can be implemented well.

As Comparative Examples 1 and 2, FIG. 1 having the same shape as FIG. 1 except that the raw material gas flow disturbing tool 18 is not provided.
Table 1 shows the manufacturing conditions and characteristic test results of the hermetically coated optical fiber formed by using the reaction furnace 5 shown in FIG.

As Comparative Example 3, as shown in FIG. 12, a reaction furnace 5 longer than that in FIG. 11, specifically, a reaction furnace 5 having a length from the upper optical fiber passage hole 10a to the exhaust port 12 of 700 mm was used. Table 1 shows the manufacturing conditions and characteristic test results of the hermetically coated optical fiber thus formed.

In each of the examples and comparative examples whose manufacturing conditions and characteristic test results are shown in Table 1, the temperature of the drawing furnace 2 is 2000 ° C., the spinning speed is 6 m / sec, the same conditions, and the upper end of the reaction furnace 5 is the same. And the lower end of the drawing furnace 2 were made the same, the amount of the seal gas supplied to the upper seal chamber 7a was made the same, and the surface temperature of the optical fiber 4a at the thermal decomposition reaction start portion was made the same. Further, the composition of the raw material gas was the same acetylene gas in all Examples and Comparative Examples.

[0056]

[Table 1] As is clear from each example and each comparative example, by using the method of the present invention, a hermetic coating having a sufficient film thickness and a sufficient mechanical strength while significantly reducing the amount of raw material gas used. It becomes possible to manufacture an optical fiber. Further, as is clear from Comparative Examples 1 and 3 and Examples, by adopting the method of the present invention, the reactor 5 can be downsized while having a sufficient film thickness, sufficient initial strength, sufficient fatigue characteristics and durability. It becomes possible to manufacture a hermetically coated optical fiber having hydrogen characteristics.

As the raw material gas flow disturbing device 18, in addition to the ring-shaped disk shown in FIGS. 1 and 2, protrusions or projections or projections projecting into the reaction furnace 5 are provided, or the inner diameter of the reaction furnace 5 is elongated. It is also possible to use a stirring tool such as a fan or the like in order to change the direction in a tapered shape.

The gas blowing portions 19 and 20 have one step in each of the above embodiments, but a plurality of steps may be provided in the longitudinal direction.

The aspects and effects of the invention described in the present specification other than the invention described in the claims are as follows.

A gas blowing section is provided on the upstream side of the reaction furnace, gas is blown obliquely downward in the tangential direction of the inner circumference of the reaction furnace, and the raw material gas flow is disturbed in the reaction furnace downstream of the gas blowing section. A tool is provided to disturb the flow of the raw material gas at least near the surface of the optical fiber.

In this way, since the gas blown into the reaction furnace from the gas blowing portion swirls along the inner circumference of the reaction furnace and descends, the surface of the tool for disturbing the raw material gas is washed. It is possible to prevent the reaction product from adhering to the raw material gas flow disturbing tool and reduce the number of times of cleaning the raw material gas flow disturbing tool.

In this case, an inert gas or a raw material gas is blown from the gas blowing portion. When the raw material gas is blown in, the reaction speed becomes faster, the film formation speed becomes faster, and the hermetically coated optical fiber can be manufactured efficiently in a shorter time, and the hermetically coated optical fiber can be spun for high-speed optical fiber spinning. Can be manufactured.

Further, in each of the above-mentioned embodiments, only the example of carbon coating has been explained, but as the hermetic coating, Si ₃ N _{4 is used.}
There is a coating, and the source gas used in this case is (S
iCl ₄ + NH ₃ ). It goes without saying that the invention can also be used with these hermetically coated optical fibers.

[0064]

As described above, according to the present invention, the following excellent effects can be obtained.

In the present invention, the flow of the raw material gas at least near the surface of the optical fiber is disturbed in the reaction furnace, so that the concentration of the raw material gas near the surface of the optical fiber can be prevented from lowering. Therefore, the reaction speed becomes faster, the film formation speed can be prevented from lowering, and the hermetically coated optical fiber can be efficiently manufactured in a short time. In particular, according to the present invention, a sufficient reaction of the raw material gas occurs within a limited time, so that the hermetically coated optical fiber can be manufactured in correspondence with the higher speed drawing. Further, according to the present invention, the utilization efficiency of the raw material gas can be improved. Furthermore, according to the present invention, it is possible to minimize the size increase of the reaction furnace.

Further, for example, a raw material gas flow disturbing member which projects in a direction intersecting with the flow direction of the raw material gas is provided in the reaction furnace, and the raw material gas flow disturbing device at least near the surface of the optical fiber Therefore, the concentration of the raw material gas on the surface of the optical fiber in the reaction furnace can be prevented from lowering without using a means for consuming the gas or the like. If no means for consuming gas or the like is used, the hermetically coated optical fiber can be manufactured at low cost.

In addition, since gas is blown into the reaction furnace from a gas blowing portion provided in the longitudinal direction of the reaction furnace, the flow of the raw material gas at least near the surface of the optical fiber is disturbed. It is possible to disturb the flow of the raw material gas near the surface of the optical fiber. In this case, since a raw material gas flow disturbing device protruding into the reaction furnace is not used,
The hermetically coated optical fiber can be manufactured while avoiding the problem of cleaning caused by the reaction product adhering to the tool for disturbing the raw material gas flow.

Further, the vibrating body is provided in the reaction furnace, and the flow of the raw material gas at least near the surface of the optical fiber is disturbed by the vibration of the vibrating body, so that the concentration of the raw material gas near the surface of the optical fiber can be prevented from lowering. Therefore, the reaction speed becomes faster, the film formation speed can be prevented from lowering, and the hermetically coated optical fiber can be efficiently manufactured in a short time. In this case, by appropriately selecting the frequency of the ultrasonic vibrator, the raw material gas in the reaction furnace can be efficiently stirred.

[Brief description of drawings]

FIG. 1 is a vertical sectional end view of a reaction furnace in a first embodiment of an apparatus for carrying out a method for manufacturing a hermetically coated optical fiber according to the present invention.

FIG. 2 is a plan view of a raw material gas flow disturbing tool used in the first embodiment.

FIG. 3 is a vertical sectional end view of a reaction furnace in a second embodiment of the apparatus for carrying out the method for manufacturing a hermetically coated optical fiber according to the present invention.

FIG. 4 is a cross-sectional end view of a gas blowing portion used in a second embodiment.

FIG. 5 is a vertical cross-sectional end view of a third embodiment of a reaction furnace in an apparatus for carrying out the method for producing a hermetically coated optical fiber according to the present invention.

FIG. 6 is a cross-sectional end view of a gas blowing portion used in a third embodiment.

FIG. 7 is a plan view of a raw material gas flow disturbing tool used in a third embodiment.

FIG. 8 is a vertical cross-sectional end view of a fourth embodiment of a reaction furnace in an apparatus for carrying out the method for producing a hermetically coated optical fiber according to the present invention.

FIG. 9 is a vertical sectional end view of a reaction furnace in a fifth embodiment of an apparatus for carrying out the method for manufacturing a hermetically coated optical fiber according to the present invention.

FIG. 10 is a vertical cross-sectional end view showing a schematic configuration of a conventional hermetically coated optical fiber manufacturing apparatus.

FIG. 11 is a vertical cross-sectional end view showing one example of a reaction furnace in a conventional hermetically coated optical fiber manufacturing apparatus.

FIG. 12 is a vertical cross-sectional end view showing another example of a reaction furnace in a conventional hermetically coated optical fiber manufacturing apparatus.

[Explanation of symbols]

 1 Heater 2 Wire drawing furnace 3 Optical fiber base material 4a Optical fiber 4b Hermetically coated optical fiber 4c Optical fiber core wire 5 Reactor 6a, 6b Partition body 7a, 7b Seal chamber 8a Upper seal gas supply port 8b Lower seal gas supply port 9a, 9b Optical fiber passage hole 10a, 10b Optical fiber passage hole 11 Raw material gas supply port 12 Exhaust port 13 Outer diameter measuring instrument 14 Resin coating device 15 Resin curing furnace 16 Outer diameter measuring instrument 17 Take-up capstan 18 Raw material gas flow disturbing tool 18a Fiber through hole 18b Gas passage hole 19 Gas blowing part 20 Gas blowing part 22 Ultrasonic transducer

Claims (4)

[Claims] 1. A hermetically coated light for producing a hermetically coated optical fiber by causing a raw material gas supplied into the reactor to undergo a chemical reaction to coat a hermetic film on the surface of the optical fiber while passing the optical fiber through the reactor. In the method for producing a fiber, the flow of the raw material gas at least near the surface of the optical fiber is disturbed in the reaction furnace, the method for producing a hermetically coated optical fiber. 2. A hermetically coated light for producing a hermetically coated optical fiber by causing a raw material gas supplied into the reactor to undergo a chemical reaction to coat a hermetic film on the surface of the optical fiber while passing the optical fiber through the reactor. In the method for producing a fiber, a hermetic coating is provided in the reaction furnace, wherein a raw material gas flow disturbing tool is provided, and the raw material gas flow disturbing tool disturbs at least the flow of the raw material gas near the surface of the optical fiber. Optical fiber manufacturing method. 3. A hermetically coated light for producing a hermetically coated optical fiber by causing a raw material gas supplied into the reactor to undergo a chemical reaction to coat a hermetic film on the surface of the optical fiber while passing the optical fiber through the reactor. In the method for producing a fiber, the flow of the raw material gas at least near the surface of the optical fiber is disturbed by blowing gas into the reaction furnace from a gas blowing portion provided in the longitudinal direction of the reaction furnace. A method for producing a hermetically coated optical fiber. 4. A hermetically coated light for producing a hermetically coated optical fiber by causing a raw material gas supplied into the reactor to undergo a chemical reaction to coat a hermetic film on the surface of the optical fiber while passing the optical fiber through the reactor. A method for producing a fiber, wherein a vibrating body is provided in the reaction furnace, and the flow of the raw material gas at least near the surface of the optical fiber is disturbed by the vibration of the vibrating body.