JPH07237938A - Method for producing hermetically coated optical fiber and apparatus therefor - Google Patents

Abstract

PURPOSE:To improve the productivity and quality of an optical fiber by forming a fiber passage hole of a reactor in a circle and carrying out positioning control of the reactor so that the optical fiber travels the center of circle in providing a hermetic coat to the optical fiber. CONSTITUTION:A preform 1 for optical fiber is melted and spun in a drawing furnace 2 to form an optical fiber bare wire 3 and the optical fiber bare wire 3 is passed through a fiber position detector 13 and further, passed through circular fiber passage holes 4a and 4b and introduced into a reactor 7 for hermetic coat. Hermetic coat is formed in the reactor 7 and fed through circular fiber passage holes 9a and 9b in the lower part of the reactor 7 to the outside. At that time, the position of the reactor 7 is controlled by a position controlling means so that the centers of the fiber passage holes 4a, 4b, 9a and 9b always coincide with the position of the traveling fiber 3 based on a position-detecting signal from fiber position detectors 13 and 14 and reactor position detectors 15a and 15b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a hermetically coated optical fiber having excellent hydrogen resistance and mechanical properties, and more particularly to a method for mass-producing a high quality hermetically coated optical fiber.

[0002]

2. Description of the Related Art A hermetic coating on the outer periphery of a fiber not coated with a so-called primary coat (hereinafter, also referred to as bare optical fiber) immediately after a preform for an optical fiber is melted and spun in a drawing furnace, It is very effective as a means to prevent water, hydrogen, outside air, etc. from entering the optical fiber. Inorganic materials such as metals including alloys and carbon are generally used as the coating material, and among them, carbon (carbon) coating is excellent in terms of its chemical stability, denseness of structure and the like. As a specific coating method, it is known that a CVD method (chemical vapor deposition method) of chemically reacting a raw material gas to deposit on a fiber surface is advantageous in terms of film formation rate and film quality. Conventionally, as such a technique, there is a manufacturing apparatus as shown in, for example, Japanese Patent Publication No. 60-25381, U.S. Pat. No. 4,790,625 or European Patent No. 0,308,143. A typical type of reactor is a seal gas inlet, raw material gas inlet, and exhaust gas inlet in order from the top (drawing furnace side). The high temperature light just spun from the drawing furnace is used. The bare fiber is hermetically coated by a thermal chemical reaction between these raw gas inlets and outlets. On the other hand, as a method of detecting the position of an optical fiber in an optical fiber drawing furnace, for example, a horizontal plane of a bare optical fiber drawn from an opening under a drawing furnace is proposed in Japanese Patent Laid-Open No. 60-137842. A method is known in which a preform attachment position is controlled by a position detection signal from an inner position detection device, and a clearance amount between a preform and an aligning airtight plate at the opening of the drawing furnace is controlled.

[0003]

Conventionally, the length of the preform to be drawn is not so long, and therefore the time-dependent movement (deviation) of the fiber running line caused by the slight bending of the preform and the minute distortion of the drawing machine column is at most. It was as small as 1 mm or less, and there was almost no problem. However, with the development of mass-production technology in recent years, the above-mentioned problems have become apparent due to the fact that large and long preforms with a fiber-equivalent length of several hundred km have begun to be used. The fiber comes into contact with the fiber passage opening of the reaction container, causing a disconnection.

[0004]

As means for solving the above problems, as a means for solving the above problems, an optical fiber preform is melted and spun in a drawing furnace to form a bare optical fiber, and then the bare optical fiber is passed through a reaction vessel. A raw material gas is introduced together with the reaction vessel, and in the method for producing a hermetically coated optical fiber in which a thin film coating layer is formed on the bare optical fiber by a chemical vapor deposition method, the fiber passage hole of the reaction vessel is circular, and It is characterized in that the positioning of the reaction vessel is controlled so that the traveling fiber is located at the center of the circle. As a particularly preferable embodiment of the present invention, (1) the positioning control of the reaction vessel is performed freely in the X-axis direction and the Y-axis direction on a plane substantially perpendicular to the Z axis when the fiber traveling axis is the Z axis. What is done by the movable position control means,
(2) The position control means has a mechanism that is automatically driven by remote control, and detects the fiber traveling position online so that the fiber traveling position passes through the center of the fiber passage port of the reaction vessel. While performing the positioning control, (3) the relative position between the fiber traveling position and the fiber passage port of the reaction vessel is detected by a detector, and the fiber traveling position is set to the center of the passage port from the deviation between the detection signals of the both. The amount of movement of the reaction vessel is calculated by an arithmetic processing unit so that the reaction vessel is fed back online to the remote controller of the position control means to automatically control the positioning of the reaction vessel. (4) The X axis as the position control means A stage freely movable in the Y-direction and the Y-axis direction is used, and the stage is provided at least at two positions, that is, the upper part and the lower part of the reaction vessel. To position the upper fiber passage opening and the lower fiber passage opening of the reaction container by attaching the respective dice, (5) using a laser light position detector as the fiber traveling position detector, (6) the hermetic coat The material of the layer is carbon,
Is mentioned. In the present invention, the optical fiber preform is melted and spun in a drawing furnace to form a bare optical fiber, the bare optical fiber is passed through the reaction vessel immediately after the drawing furnace, and the raw material is fed into the reaction vessel. In a device for producing a hermetically coated optical fiber in which a gas is introduced and a thin film coating layer is formed on the bare optical fiber by a chemical vapor deposition method, a cross section in a plane perpendicular to the fiber running direction of the upper and lower fiber passage ports of a reaction vessel. A device having a circular shape, a device for detecting a relative position between the center of the cross section of the upper and lower fiber passages and a fiber traveling position, a device for calculating deviations in the X and Y directions of the relative position detection signal, and the relative device. Turning on the position control device for moving the reaction container in the X and Y directions by the output signal corresponding to the deviation of the physical position detection signal in the X and Y directions, the detection device, the arithmetic device and the position control device. There is provided the manufacturing apparatus comprising comprises a remote control to means actuating means and the position control device is operated in in. In the device of the present invention, the reaction vessel is held by at least two places, an upper part and a lower part,
Moreover, since the holders are attached to the stages that are freely movable in the X-axis direction and the Y-axis direction, respectively, it is possible to realize more accurate control.

[0005]

In the present invention, as shown in FIG. 1, an optical fiber bare wire 3 spun in a drawing furnace passes through a position detecting device 13 such as a commercially available laser size measuring device, and a reaction container 7 for hermetic coating. , Through the fiber passage port 4. The hermetically coated fiber in the reaction vessel 7 is led out to the outside through the lower fiber passage port 9, and thereafter, a resin for protective coating is coated and wound on a reel in the same manner as in the ordinary optical fiber manufacturing method. . Many of the conventional hermetic coating reaction vessels are of a fixed type, and it is usual to perform drawing and hermetic coating without moving after positioning them in advance. Further, in the case where the drawing furnace and the reaction vessel are integrated, the reaction tube is fixed from the beginning and is immobile. On the other hand, in the present invention, circular holes are used as the fiber passage ports 4 and 9 of the reaction vessel, and the position of the reaction vessel 7 can be set so that the fiber traveling position is always at the center thereof. The above problems have been resolved. First, as a method for detecting the position of a running bare optical fiber, visual detection, electrical means such as a position detector using the eddy current method, or a position detector using ultrasonic waves can be used. Method, for example, a position detector using a laser beam is not easily affected by disturbance, and stable sensing can be performed, which is particularly preferable. Position detection device 13,
Based on the detection results from 15a and 15b, the position of the reaction vessel is controlled so that the center of the fiber passage opening of the reaction vessel and the running fiber always match. As a result, the distance between the fiber and the edge of the passage opening is constant at any point during the drawing, so that the risk of contact is reduced even if the fiber is slightly moved in any direction.

In the present invention, even if the reaction vessel is fixed to the movable position control means at one place by one holder, the verticality (horizontality between the central axis of the reaction vessel and the traveling fiber axis ) is obtained. If there is no problem, if it is fixed to the upper and lower parts with holders and each is attached to the free XY axis stage and operated independently, the verticality can be adjusted and more accurate control becomes possible. Therefore, it is preferable. As described above, the moving operation of the stage is visually or by a CCD camera (Charge Coupled Devise camera: a commercially available video camera) or the like, and the relative position between the fiber traveling position and the reaction container is confirmed and manually or directly controlled. Of course, it is possible to do so. The inventors further studied, provided a mechanism for freely moving the reaction vessel on a plane perpendicular to the fiber traveling axis, and responded to the phenomenon that the traveling position of the fiber moved during the drawing online. We have also devised a method of detecting the shift in the relative position of the two and correcting the position of the reaction vessel by remote control based on the result. Furthermore, the work was made more efficient by automating this and controlling it by a computer. That is, the position of the traveling fiber and the position of the reaction vessel are automatically detected by the separately installed sensor 15 such as an electromagnetic position detector, an ultrasonic position detector, a laser size measuring device, or a laser displacement meter. According to this, since the result can be calculated by the computer 16 and the stepping motor of the automatic stage 12 can be controlled to perform automatic positioning, this is the most preferable form in terms of labor saving.

Hereinafter, one embodiment of the present invention will be described in more detail with reference to the drawings. The laser dimension measuring device 13 was installed directly below the drawing furnace, and the reaction vessel 7 was installed directly below it. The reaction vessel 7 is, for example, a reaction tube made of quartz, and a hole having a diameter of 2 mm to 6 mm, preferably 3 mm to 4 mm is provided at the upper end of the reaction tube as a passage port 4a for cutting off an external atmosphere and an atmosphere inside the reaction tube. It is opened with good dimensional accuracy. Another for constructing a seal gas chamber underneath
A partition wall 42 and a passage port 4b are provided, and a raw material introduction pipe 6 for introducing the raw material from the lower side of the partition wall 42 is provided.
Hereinafter, the portion having the above-mentioned configuration will be referred to as the upper portion of the reaction tube. An exhaust pipe 8 for the reaction gas and by-products is provided below the reaction tube, and a lower seal chamber is provided again via the partition wall 9a.
One place on this upper part, holder 1 for fixing the reaction tube
0a and the support rod 11a are attached, and the support rod 11a is fixed to the universal XY axis stage 12a. A position sensor (a laser displacement meter in this example) is provided as a reaction tube position detector 15a in the immediate vicinity of the holder 10a fixed to the upper part of the reaction tube. A plurality of position detection sensors are provided as needed so that the position of an arbitrary point (X, Y) on the plane perpendicular to the Z axis can be read. In the present invention, preferably the holder 10b and the support rod 11b are similarly attached to at least another place, for example, the lower portion of the reaction tube, and the support rod 1 is attached.
If 1b is fixed to the free XY axis stage 12b and the position detection sensor 15b is provided, the position control becomes more precise. Since the outer diameter of the fiber is usually about 0.1 mm, the position detection sensor has a measurement accuracy of at least 0.1 mm or less, and a machine having the same movement accuracy of the free XY axis stage is used. Position detection of the fiber and the reaction tube and feedback of the result to the stage movement are always performed during drawing.

As described above, in the present invention, when the running position of the fiber is the vertical axis (Z axis), the deviation between the running position of the fiber on the horizontal plane and the position of the center of the reaction tube on the horizontal plane is detected. Then, based on the result, the running position of the fiber is adjusted so as to always come to the center of the reaction tube, that is, the center of the passage port. Of course, the fiber passage port of the reaction tube is accurately provided at the center of the reaction tube. As a result, the position of the reaction tube follows the on-time accordingly with respect to the temporal movement of the fiber traveling position that occurs during the drawing of a long preform, so that stable coating can be performed in the longitudinal direction of the fiber. In addition, by automatically controlling this operation using a device including a position detection sensor such as a laser, a computer, a remote controller, and an automatic stage, monitoring work can be omitted, and labor can be greatly saved. On the other hand, even when using an apparatus in which the drawing furnace of the reaction vessel is integrated,
As shown in FIG. 3, the position of the reaction tube can be adjusted by providing a minute clearance 20 between the drawing furnace 2 and the reaction vessel 7, or by connecting this portion with a flexible pipe 22. Examples of the material of the reaction vessel in which the hermetic coating is performed in the present invention include quartz, metal and ceramics.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Example 1 Using a coating apparatus as shown in FIG. 1, a long coating was continuously drawn for about 300 km, and carbon coating was simultaneously performed. 200 cc / each of ethylene and chlorine are used as carbon raw materials.
It was supplied to the reaction vessel (reaction tube) at a flow rate of min and 300 cc / min, and these gases were pyrolyzed by the heat of the fiber itself to coat a bare carbon fiber coating with a carbon coating having a thickness of about 50 nm. The drawing speed was 600 m / min, and the drawing was continuously performed for about 8 hours. The position of the reaction tube was automatically controlled by a device composed of a position sensor using a laser displacement meter, a computer, a remote controller and an automatic XY axis stage. During drawing
The fiber always passed through the center of the reaction vessel (passage port), there was no break in the middle, and the coating was performed for the entire length. The manufactured hermetically coated fiber was divided into pieces each having a length of about 10 km, and a strength test was performed at each end. A general-purpose tensile tester was used for the strength test, and the gauge length was 300 mm and the tensile strength was 1
The number of samples is 2 at each end.
The breaking strength distribution was determined by setting the number to 0. As a result, the intensity distribution is uniform in each part, and the average intensity is about 5 GP.
No deterioration of strength was observed in the longitudinal direction of the fiber, and the fiber had uniform strength characteristics.

Comparative Example 1 A conventional apparatus was used to carry out drawing under the same conditions as in Example 1 without adjusting the position of the reaction vessel (reaction tube) online. As a result, the running position of the fiber shifts with time, and the fiber and the passage end of the reaction vessel come into contact with each other when the fiber is drawn for about 180 km,
I had a break in the way. As a result of performing a strength test on this fiber in the same manner as in Example 1, the dispersion of the strength distribution became large after the drawing length exceeded 150 km, and the average strength thereof began to deteriorate to about 3 to 4 GPa. 2GP
It was confirmed that the probability that the low-strength portion of a or less was present was increased to 10% to 30%.

Example 2 An apparatus in which a drawing furnace and a reaction vessel are integrated as shown in FIG. 2 was used. A minute gap of about 1 to 3 mm, that is, a clearance 20 is provided between the reaction container and the drawing furnace, and a measurement window (observation window) 21 is provided for detecting the fiber traveling position. With such a configuration, the position of the reaction vessel can be controlled, and the drawing was performed under the same manufacturing conditions as in Example 1. The position control mechanism of the reaction tube was the same as in the case of Example 1. As a result, the coating was applied over the entire length without breaking, and no strength deterioration was observed in the longitudinal direction of the fiber.

[Example 3] The same test as described above was conducted using an apparatus in which a reaction vessel and a drawing furnace as shown in Fig. 3 were connected by a flexible pipe 22 made of stainless steel. Also in this case, a glass window (which may be a crystal window) transparent to the measuring light for position detection is attached to the flexible pipe 22 as a measuring window (observation window) 21. He-
When a Ne laser is used, borosilicate crown glass is used. The position control mechanism of the reaction tube was the same as in the case of Example 1. As a result, the coating was applied without breakage over the entire length, the fiber always ran in the center of the reaction tube during drawing, and the result of the strength test was also uniform over the entire length.

[0013]

As described above, according to the present invention, the relative position of the fiber and the reaction tube can be always fixed even for a long preform, so that a uniform hermetic coat is applied over several hundred km. Since the strength of the fiber can be prevented from being deteriorated due to the contact between the reaction tube and the fiber, productivity and quality can be improved.
Further, by automating the operation of the present invention, labor can be saved, which contributes to a reduction in manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of the present invention.

FIG. 2 is a schematic explanatory view showing another embodiment of the present invention.

FIG. 3 is a schematic explanatory view showing still another embodiment of the present invention.

[Explanation of symbols]

1 optical fiber preform, 2 wire drawing furnace,
3 bare optical fiber, 4a, 4b fiber passage,
5 seal gas introduction pipe, 6 raw material gas introduction pipe,
7 reaction vessel, 8 exhaust pipe, 9a, 9b fiber passage port, 10a, 10b fixture, 11a, 11
b support rod, 12a, 12b free XY axis stage,
13 fiber position detector, 14 fiber position detector, 15a, 15b reaction tube position detector,
16 arithmetic unit, 20 clearance, 21 measurement window, 22 flexible pipe.

Claims (9)

[Claims] 1. An optical fiber preform is melted and spun in a drawing furnace to form a bare optical fiber, the bare optical fiber is passed through the reaction vessel, and a raw material gas is introduced into the reaction vessel. In a method for producing a hermetically coated optical fiber in which a thin film coating layer is formed on the bare optical fiber by a chemical vapor deposition method, the fiber passage hole of the reaction vessel is circular, and the running fiber is located at the center of the circle. The above manufacturing method, characterized in that the positioning of the reaction container is controlled. 2. The position control of the reaction vessel is performed by a position control means that is freely movable in the X-axis direction and the Y-axis direction in a plane substantially perpendicular to the Z axis when the fiber traveling axis is the Z axis. The manufacturing method according to claim 1, wherein: 3. The position control means has a mechanism that is automatically driven by a remote control, and the fiber traveling position is set online so that the fiber traveling position passes through the center of the fiber passage port of the reaction vessel. 3. The positioning control is performed while being detected by.
The manufacturing method described. 4. A detector detects the relative position between the fiber traveling position and the fiber passage opening of the reaction container, and the fiber traveling position of the reaction container is adjusted so that the fiber traveling position is located at the center of the passage opening based on the deviation between the detection signals of the two. 4. The manufacturing method according to claim 3, wherein the movement amount is calculated by an arithmetic processing unit and is fed back online to the remote controller of the position control means to automatically control the positioning of the reaction container. 5. The X-axis direction and Y as the position control means
A freely movable stage is used as an axis, and the upper fiber passage port and the lower fiber passage port of the reaction vessel are positioned by mounting the stage at at least two places of the upper and lower portions of the reaction vessel. The manufacturing method according to any one of claims 1 to 5. 6. The manufacturing method according to claim 5, wherein a laser beam position detector is used as the fiber traveling position detector. 7. The manufacturing method according to claim 1, wherein the material of the hermetic coat layer is carbon. 8. A preform for an optical fiber is melted and spun in a drawing furnace to form a bare optical fiber, the bare optical fiber is passed through a reaction vessel immediately after the drawing furnace, and a raw material is placed in the reaction vessel. In a device for producing a hermetically coated optical fiber in which a gas is introduced and a thin film coating layer is formed on the bare optical fiber by a chemical vapor deposition method, a cross section in a plane perpendicular to the fiber running direction of the upper and lower fiber passage ports of a reaction vessel. A device having a circular shape, a device for detecting a relative position between the center of the cross section of the upper and lower fiber passages and a fiber traveling position, a device for calculating deviations in the X and Y directions of the relative position detection signal, and the relative device. A position control device for moving the reaction container in the X and Y directions by an output signal corresponding to deviations of the physical position detection signal in the X and Y directions, the detection device, the arithmetic device, and the position control device online. The manufacturing apparatus described above, which is provided with a means for operating the position control device and a means for remotely controlling the operation of the position control device. 9. The reaction container is held at least at two positions, an upper part and a lower part, by holders, and the holders are attached to a stage that is freely movable in the X-axis direction and the Y-axis direction, respectively. The manufacturing apparatus according to claim 8, which is characterized in that: