JPH06234535A - Method for producing optical fiber preform and optical fiber and device for producing its preform - Google Patents

Abstract

PURPOSE:To obtain an optical fiber preform free from bubbles by boring a hole in the preform contg. a bubble from the surface with a high-power pulse laser beam to suck off the gas in the bubble, heating, melting and sealing the hole inlet. CONSTITUTION:An optical fiber preform 2 contg. a bubble 3 is clamped by a chuck 10 and set in a vacuum chamber 1. The light from a halogen lamp 4 is then injected in the axial direction of the preform through a lens system 5, the light 15 scatttered by the bubble 3 is received by a sensor 6, and the information is processed to specify the position of the bubble 3. A high-power pulse laser beam is injected on the bubble 3 from a laser oscillation system 11 to bore a small-diameter hole to the bubble 3 from the surface, and the gas in the bubble 3 is sucked off. A carbon resistance heater 16 is then brought close to the hole inlet to heat and seal the inlet. The obtained preform 2 is heated, melted and drawn, and an optical fiber free from bubbles is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber preform used in optical fiber communication and the like, an optical fiber production method and an optical fiber preform production apparatus, and more particularly to removing bubbles existing in the optical fiber preform. The present invention relates to a method and an apparatus for manufacturing an optical fiber.

[0002]

2. Description of the Related Art Optical fibers are generally manufactured by heating, melting and drawing an optical fiber preform having a core and a clad. By the way, in the process of manufacturing the optical fiber preform, bubbles may be generated in the preform, but the presence of these bubbles remains in the drawn optical fiber and disturbs the structure of the optical fiber, affecting the transmission characteristics. Exert. Further, there is a problem that the optical fiber is easily broken from the bubbles in the optical fiber as a starting point. Conventionally, for bubbles in the optical fiber preform, 1) either leave the bubbles as they are and draw them into the optical fiber, or 2) mechanically cut the part containing bubbles of the optical fiber preform to remove it. , 3) The problem was solved by melting and tearing away the part of the base material containing bubbles.

[0003]

In the conventional method of this type, when the base material is divided by mechanical means or melting, the loss of the base material at the cutting portion is large, and the lead-out work time during drawing is further increased. (At the start of drawing, a predetermined fiber diameter and a predetermined drawing speed while melting and dropping a small part of the base material to draw, that is, a working time until a steady drawing state,
It takes about 30 to 60 minutes in the conventional method), but it takes much time to obtain the same fiber length. Also,
When a fiber is drawn while leaving bubbles in the base material, the bubble portion must be cut out after drawing, and a reliable method is not currently known as an inspection method. It is an object of the present invention to provide a method capable of producing a bubble-free optical fiber from an optical fiber preform having such bubbles.

[0004]

Means for Solving the Problems As means for solving the above-mentioned problems, the present invention is as follows: 1) After finely perforating a bubble from an optical fiber preform surface having a bubble inside to the bubble by a high-power pulse laser, A method for producing an optical fiber preform characterized by sucking and removing the gas inside the bubble and then heat-melting and sealing the entrance of the perforated portion, 2) High-power pulse from the surface of the optical fiber preform having bubbles inside Laser is used to penetrate into the bubble and perforate it finely, then the gas inside the bubble is removed by suction, and then the inlet of the perforation part is heated and melted and sealed. A method for producing an optical fiber, characterized in that the optical fiber has no bubbles, 3) a vacuum container, (1) a movable chuck for holding an optical fiber preform, and (2) a chuck held by the chuck. Inside the optical fiber preform Means for identifying the position of the bubble, (3) means for irradiating the bubble with a high pulse laser beam in accordance with the position identification information according to (2) above to perforate from the base material surface to the bubble, (4) heating and melting the perforation inlet It has a movable heater for sealing,
And (5) an apparatus for manufacturing an optical fiber preform, which includes a controller for controlling a chuck position and outputting a movable heater position control signal according to the position specifying information.

[0005]

According to the present invention, as shown in FIG. 2 (a), the bubbles 3 generated in the optical fiber preform 2 are used from the outside of the preform by using a high output pulse laser such as a YAG laser, a CO ₂ laser, an excimer laser. , Peak power 1 Mw / mm ^{2 to} 50 Mw /
The laser beam 14 is irradiated with the beam diameter narrowed down to about 1 to 100 μm under the condition of mm ² , pulse width of about 1 to 10 nsec to perforate from the outside of the optical fiber fiber preform to the bubble portion. Next, as shown in FIG. 2B, when the gas inside the bubbles is sucked and exhausted from the perforated portion to bring the inside into a state close to a vacuum, the perforated portion inlet portion as shown in FIG. It is sealed by heating and melting so that voids containing no gas remain in the base material. The optical fiber preform thus prepared is heated and melted at a temperature of about 2000 ° C. and drawn to form an optical fiber.

The average bubble size generated in the optical fiber preform production line is about 1 mm in diameter. It is difficult to make a hole with a diameter of micron order in the optical fiber preform, especially silica glass having a high melting point, but it is possible if a high energy pulse laser is used. To process quartz,
A pulse width of several ηsec is required, and as its energy, a YAG laser, a CO ₂ laser, an excimer laser, or the like can be used. The beam is narrowed down by an optical system, and is vertically incident on the surface of the base material so that the bubble portion has the shortest distance. If the gas inside the bubbles is removed from the small-diameter holes and the cavity is closed to a vacuum state and the hole entrance is blocked, the gas will not be in the base metal even if it is heated and melted for drawing. As a result, the shape cannot be maintained, and since the perforated portion is melted and the cavity disappears due to surface tension, no bubbles are present in the drawn fiber. As described above, in order to eliminate the voids by the surface tension of the fused quartz so as not to affect the characteristics in the peripheral portion, it is desirable that the diameter of the holes drilled by the laser or the like be several μm to several hundred μm.

[0007]

【Example】

Example An optical fiber having the structure shown in FIG. 1 was manufactured according to the present invention. In this embodiment, φ0.2 mm, φ1.0
A quartz optical fiber preform (hereinafter abbreviated as preform) containing three bubbles of mm and φ1.5 mm was used. The optical fiber preform 2 was gripped and set by the chuck 10 in the vacuum chamber 1. The light from the halogen lamp 4 is made to enter in parallel with the axial direction of the base material through the lens system 5, and the incident light is scattered light 15 scattered by the bubbles 3 in the base material is received by the light receiving sensor 6 and is received from the sensor. The signal is processed by the sensor processing motor control system 7 to specify the position of the bubble 3 in the base material, and the motor drive system 8 can be controlled so as to traverse the chuck 10 to the spot position of the laser beam. A YAG laser is used as the laser oscillation system 11 and has a peak power of 20 Mw / mm ² and a pulse width of 5
The laser beam 14 is made to enter the bubble 3 with a beam diameter of 10 μm as ηsec, and is continuously made incident until the scattering information pattern of the halogen light at the bubble part changes, and a small-diameter hole is formed almost from the surface to the bubble part. It was The vacuum degree in the vacuum chamber 1 was set to 0.1 Torr. After drilling, the heater holder 17 is provided with a sensor processing motor control system 7
Position control information to the motor drive system 9 and the carbon resistance heater 16 is set at the entrance of the perforation, and the temperature is about 2000 ° C.
The heater 16 heated to the above was brought close to it to melt-seal the inlet. This operation was performed for 3 bubbles. When the optical fiber preform having voids obtained above was heated to about 2000 ° C. and drawn into the optical fiber, no bubbles remained in the optical fiber.

[0008]

As described above, according to the present invention, an optical fiber without bubbles can be manufactured without performing mechanical cutting of the bubble portion of the optical fiber preform or cutting by heat melting tearing. The effect of improving the manufacturing yield is obtained. Therefore, in the optical fiber manufacturing, the quantitative production yield is improved and the long yield of the long product is also improved, which is industrially very advantageous.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram illustrating an embodiment of an optical fiber manufacturing apparatus of the present invention.

FIG. 2 is a schematic explanatory diagram illustrating an embodiment of the optical fiber manufacturing method of the present invention.

[Explanation of symbols]

1 vacuum chamber, 2 optical fiber base material, 3 air bubbles, 4 halogen lamp, 5 lens system, 6 light receiving sensor, 7 sensor processing / motor control system, 8
Motor drive system, 9 motor drive system, 10 chuck, 11 laser oscillation system, 12 laser operation system,
13 vacuum pump system connection, 14 laser beam,
15 scattered light, 16 heater, 17 heater holder.

Claims (3)

[Claims] 1. A thin fiber is penetrated from the surface of an optical fiber preform having bubbles inside to the bubbles by a high-power pulse laser, gas inside the bubbles is removed by suction, and then the inlet of the hole is heated. A method for manufacturing an optical fiber preform, which comprises melt-sealing. 2. A high-power pulsed laser is used to penetrate into the bubble from the surface of the optical fiber preform having the bubble inside, and the gas inside the bubble is removed by suction, and then the inlet of the hole is heated. A method for producing an optical fiber, characterized in that a base material having a cavity obtained after fusion-sealing is drawn by heating and melting to form an optical fiber having no bubbles. 3. A vacuum container in which (1) a movable chuck for holding an optical fiber preform, (2) means for locating a bubble in the optical fiber preform held by the chuck, (3) ) A means for irradiating a bubble with a high pulse laser beam in accordance with the position identification information according to the above (2) to perforate from the base material surface to the bubble
(4) having a movable heater for heating and melting and sealing the perforation inlet, and (5) having a control device for outputting chuck position control and movable heater position control signals according to the position specifying information. Optical fiber preform manufacturing equipment.