JPH0840741A - Method for drawing preform of optical fiber and machine for drawing preform of optical fiber - Google Patents

Abstract

PURPOSE:To obtain a bend-free drawn preform, even when there happens axis deviation between the feeding dummy rod and the take-off dummy rod, the drawn preform is controlled so that its secter axis coincides with the center axis of the drawig over. CONSTITUTION:In an optical fiber-drawing machine 10 for the base material, fine particles of glass are formed by the flame hydrolysis to give a glass body as a preform for optical fiber 3 and the preform is heated and softened to effect drawing in the drawing over whereby the drawn preform 3A is obtained in a prescribed diameter. In this process, two couples of sensors 11, 12 for detecting the distance to the surface of the necking position of the preform are set to the lower end of the oven body 4 of the drawing oven 2 in the longitudinal and transverse directions to control the dummy rod 6 for feeding the base material in the upper part so that the center axis 3 of the softening part of the base material 3 held on the lower take off dummy rod 8 always comes on the moving axis of the dummy rod 6 for feeding as well as the moving axis of the dummy rod 8 for taking off and further the axis coincides with the center of the oven body 4 thereby producing the drawn preform 3A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stretching an optical fiber preform for producing a stretched preform by stretching an optical fiber preform having glass particles formed by a flame hydrolysis reaction to form a glass body. More particularly, the present invention relates to an optical fiber preform stretching method and an optical fiber preform stretching apparatus for producing a preform that does not bend after being stretched in an optical fiber preform stretching step.

[0002]

2. Description of the Related Art Generally, in an optical fiber, light is
It propagates through the core while being totally reflected at the boundary surface between the core and the clad. In such an optical fiber, it is ideal that the intensity of the incident light be emitted from the terminal without being attenuated, but there are various causes as the light propagates through the core of the optical fiber. Causes transmission loss. The degree to which the intensity of light becomes weaker while propagating in an optical fiber is the transmission loss of the optical fiber. In particular, the defective structural characteristics of the spun optical fiber have a great influence on the transmission loss and the like, and it is desired to manufacture an optical fiber preform that does not cause bending. Such an optical fiber is not manufactured at once by spinning an optical fiber base material (for example, 50φ) formed by producing glass particles by a flame hydrolysis reaction to form a glass body. The base material (for example, 50φ) is stretched to manufacture a stretched base material (for example, 20φ), and then the stretched base material is spun and manufactured.

The drawing base material is conventionally manufactured by using an optical fiber base material drawing apparatus as shown in FIG. That is, reference numeral 1 is an optical fiber preform stretching apparatus, which produces a glass fine particle by a flame hydrolysis reaction to form a glass body, and extends the produced optical fiber preform to produce a stretched preform. Reference numeral 2 is a drawing furnace, and the drawing furnace 2 melts the inserted optical fiber base material 3 to draw a base material 3A having a desired diameter.
For manufacturing. Reference numeral 4 denotes a furnace body formed in a cylindrical shape, into which the optical fiber preform 3 is inserted. 5
Is a heater provided in the lower part of the furnace body 3, and is provided so as to cover the outer peripheral surface of the furnace body 4. The heater 5 is for softening the optical fiber preform 3 inserted in the furnace body 4 into a state in which it can be drawn to a predetermined diameter.

Reference numeral 6 is a base material feeding dummy rod, which is processed by a glass lathe and fused onto the upper part of the optical fiber base material 3. The base material feeding dummy rod 6 is held by a base material feeding chuck portion 7 provided above the drawing furnace 2. The base material feeding chuck portion 7 has a function of feeding the optical fiber base material 3 downward little by little by feeding the base material feeding dummy rod 6 downward little by little. Reference numeral 8 denotes a dummy rod for taking the preform, which is processed by a glass lathe and fused to the lower part of the optical fiber preform 3. The base material take-up dummy rod 8 is held by a base material take-up chuck portion 9 provided below the drawing furnace 2. The base material take-up chuck portion 9 pulls out the base material take-up dummy rod 8 at a predetermined speed,
It has an action of pulling out the stretched preform 3A while stretching the softened optical fiber preform 3 to a predetermined diameter.

With this structure, first, the preform feeding dummy rod 6 is fused to the upper part of the optical fiber preform 3 and the take-up dummy rod 8 is fused to the lower part by a glass lathe. Next, the optical fiber preform 3 to which the dummy rods 6 and 8 are attached is inserted into the furnace body 3 of the drawing furnace 2, and the preform feeding chuck part 7 and the preform taking chuck part 9 are moved. The preform feed dummy rod 6 and the preform take-up dummy rod 8 are set so that the central axes thereof are on the central axis of the optical fiber preform 3 (the center of the drawing furnace). In such a state, the heater 5 is operated to heat the furnace body 4. When the furnace body 4 is heated, the lower end portion of the optical fiber preform 3 is softened as shown in FIG. 3 (indicated by dots in the figure), and when the preform chucking portion 9 is pulled out in this state. As shown in FIG. 3, the softened portion of the optical fiber preform 3 is stretched to form the constricted portion 3
B is formed and stretched to produce a stretched base material 3A having a predetermined diameter. Then, the extension is performed such that the extension of the central axis of the optical fiber preform 3 becomes the moving axis of the preform feeding chuck 7 and the preform pulling chuck 9 so that the preformed preform becomes I try to be straight (no bends).

[0006]

However, when the optical fiber preform 3 is drawn by using the conventional optical fiber preform drawing apparatus, the optical fiber preform 3 as shown in FIG.
For example, as shown in FIG. 4 (A), in the case of the optical fiber preform 3 in which a slight bend occurs in the optical fiber preform manufacturing process in the former stage, or in the former stage as shown in FIG. 4 (B). In the optical fiber preform manufacturing process, there is the following problem in the case of the optical fiber preform 3 in which the bending is not generated but the dummy rod is not attached straightly and the connection part has an axial deviation. That is, when the optical fiber preform 3 shown in FIGS. 4A and 4B is used and the stretching is started and the stretching is continued for a while,
The center of the softened portion 3C (FIG. 3) of the optical fiber preform 3 is on the central axis of the optical fiber preform 3 that is initially set (the movement in which the preform feeding chuck 7 and the preform taking chuck 9 move). The position is deviated from (on-axis), and the film is bent and stretched in a direction not on the axis. And in such a state,
Since the center of the softening portion 3C of the optical fiber preform 3 is located at a position deviated from the center of the drawing furnace 2, there is a difference in the amount of heat applied to the optical fiber preform 3 from the heater 5, and the softening of the optical fiber preform 3 occurs. A temperature difference occurs in the outer peripheral surface temperature of the portion 3C. This temperature difference occurs in the circumferential direction of the optical fiber preform 3, and the softening state of the optical fiber preform 3 becomes nonuniform due to this temperature difference, and thus the optical fiber preform 3 is stretched in the nonuniform softening state. Then, there is a problem that the stretched base material 3A is further bent during the stretching.

After the optical fiber preform 3 is softened and stretched as described above, when the stretched preform 3A is bent, the bent portion of the stretched preform 3A is heated by a glass lathe or the like in a later step to be repaired. Although the drawn preform 3A is spun to manufacture an optical fiber core wire, the portion where the bending is corrected in the subsequent step has a problem that the characteristics of the optical fiber are adversely affected. Further, when the stretched base material 3A is bent, there is a problem that the production yield is remarkably poor by disposing of the bent portion that is so bad that it cannot be corrected in a subsequent process, such as by discarding it. However, it is difficult to straighten the bending of the optical fiber preform 3 before stretching, which is the main cause of the bending of the stretched preform 3A, by a flame lathe or the like before stretching, and the preform feed dummy rod 6 and Dummy rod for picking up base material 8
It also requires skill to attach the optical fiber straightly, and it is difficult to always supply the optical fiber preform 3 with no axial misalignment.
It can be corrected only in the drawing step of manufacturing the drawn base material 3A, and it is necessary to correct the bending of the optical fiber base material 3 in the drawing step. The object of the present invention is that the optical fiber preform before drawing has a bend, or the preform feeding dummy rod and the preform drawing dummy rod are not attached straight to the optical fiber preform before stretching. The purpose is to obtain a stretched base material that does not bend even if there is axial misalignment between the base material feeding dummy rod and the base material receiving dummy rod.

[0008]

According to a first aspect of the present invention, there is provided a method for drawing an optical fiber preform in which a fine glass particle is formed by a flame hydrolysis reaction to form a glass body, and a preform feed dummy is provided above the glass body. The center of the drawn base material during drawing when producing a drawn base material with a predetermined diameter by heating and softening the optical fiber base material in which a dummy rod for drawing the base material is fused to the lower part of the rod Detect the position of the shaft, adjust the position of the central axis of the dummy rod for feeding the base material based on the detected value,
The stretching base material is manufactured by controlling the position of the central axis of the stretching base material so as to coincide with the central axis of the stretching furnace. In the method for drawing an optical fiber preform according to the invention of claim 2, the position of the central axis of the drawing preform during drawing is detected by heating and softening the optical fiber preform at the lower end of the drawing furnace to draw the preform. This is carried out in the constricted portion that stretches to.

An optical fiber preform stretching apparatus according to a third aspect of the present invention comprises a heater for heating the inside of the furnace, and glass particles are formed by flame hydrolysis reaction to form a glass body, and the preform is formed on the upper part. A drawing furnace that inserts an optical fiber preform with a dummy rod for preform fusion bonded to the lower part of the dummy rod for feed, and a dummy rod for preform feed above the drawing furnace to grasp the preform at a predetermined speed. A base material feeding chuck part for sending into the drawing furnace, and a base material drawing chuck part for holding a base material drawing dummy rod below the drawing furnace and drawing the base material out of the drawing furnace at a predetermined speed. In an apparatus for stretching an optical fiber preform, which comprises softening and heating the optical fiber preform in a stretching furnace to produce a stretched preform having a predetermined diameter, the optical fiber preform is provided at the lower end of the stretching furnace. When producing a stretched base material by stretching One or two or more pairs of distance detection sensors facing each other for detecting the distance to the surface of the constricted portion of the fiber preform are provided, and the preform feed dummy rod is gripped to fix the optical fiber preform at a predetermined speed. The preform feeding chuck part to be fed into the drawing furnace is attached to an XY stage movable on a horizontal plane via a chuck part support base, and the optical fiber matrix is detected from each of the two pair of sensors. A distance difference detection unit that detects and outputs a difference in distance from the distance to the surface of the constricted portion of the material is provided, and the X difference is detected based on the detection difference between the pair of distance detection sensors output from the distance difference detection unit. An XY stage control unit that calculates the moving direction and moving distance of the -Y stage and outputs the control amount to the XY stage is provided.

[0010]

According to the invention of claim 1, glass particles are formed by producing glass fine particles by a flame hydrolysis reaction,
An optical fiber preform with a preform feed dummy rod on the top and a preform take-up dummy rod on the bottom is heat-softened and stretched in a stretching furnace to produce a stretched preform with a predetermined diameter. The position of the central axis of the drawing base material in the inside is detected, the position of the central axis of the dummy rod for feeding the base material is adjusted based on the detected value, and the position of the central axis of the drawing base material is set to the central axis of the drawing furnace. Since the drawn preform is manufactured by controlling so as to match, there is a bend in the optical fiber preform before being drawn, and the preform feed dummy rod and the preform take-up dummy rod are not drawn. As a result of not being attached straight to the optical fiber preform, even if there is axial misalignment between the preform feed dummy rod and the preform take-up dummy rod, it is possible to obtain a stretched preform without bending.

According to the second aspect of the present invention, the position of the central axis of the drawing base material during drawing is detected, and the constricted portion for heating and softening the optical fiber base material at the lower end of the drawing furnace to draw the drawing base material. Therefore, the central axis of the stretched base material can be easily detected. According to the invention as set forth in claim 3, a heater for heating the inside of the furnace is provided, a glass body in which glass particles are generated by a flame hydrolysis reaction is formed, and a dummy rod for feeding a base material is provided in an upper part and a dummy rod for taking a base material is provided in a lower part A drawing furnace for inserting the optical fiber preform on which the dummy rod is fused,
A dummy rod for feeding a base material is held above the drawing furnace to feed the base material into the drawing furnace at a predetermined speed, and a dummy rod for drawing the base material is held below the drawing furnace. And a preform chucking unit for drawing the preform from the drawing furnace at a predetermined speed, and heating and softening in the drawing furnace to draw the optical fiber preform to produce a drawn preform having a predetermined diameter. In a fiber preform drawing device, the lower end of the drawing furnace is opposed to each other for detecting the distance to the surface of the constricted part of the optical fiber preform when the optical fiber preform is drawn to manufacture the drawn preform. One or two or more pairs of two distance detection sensors are provided, and a base material feeding chuck part for gripping the base material feeding dummy rod and sending the base material into the drawing furnace at a predetermined speed is provided via a chuck part support base. On an XY stage that can move on a horizontal plane And a distance difference detection unit for detecting and outputting a difference in distance from the distance from the sensor to the surface of the constricted portion of the optical fiber preform, which is detected by each of the pair of two sensors. An XY stage control unit that calculates a moving direction and a moving distance of the XY stage based on a detection difference between a pair of distance detection sensors output from the difference detection unit, and outputs a control amount to the XY stage. As a result, the pre-stretched optical fiber preform is bent, or the preform feed dummy rod and the preform take-up dummy rod are not attached straight to the prestretched optical fiber preform. Even if the base material feeding dummy rod and the base material receiving dummy rod are misaligned, a stretched base material without bending can be obtained.

[0012]

EXAMPLES Examples of a method for stretching an optical fiber preform and an apparatus for stretching an optical fiber preform according to the present invention will be described below. FIG. 1 shows an embodiment of a method for drawing an optical fiber preform and an apparatus for drawing an optical fiber preform according to the present invention. In the figure, components designated by the same reference numerals as those used in FIG. 2 are constituted by the same members. That is, 2 is a drawing furnace, 3 is an optical fiber preform, and 3A
Is a drawn base material, 4 is a furnace body, 5 is a heater, 6 is a base material feeding dummy rod, 7 is a base material feeding chuck portion, 8 is a base material taking dummy rod, and 9 is a base material taking chuck It is a department.

Numeral 10 is an optical fiber preform drawing apparatus for producing a drawn preform 3A by drawing the optical fiber preform 3 produced by forming glass fine particles by a flame hydrolysis reaction to form a glass body. Is. Reference numerals 11 and 12 denote distance detection sensors, which are provided at positions opposite to the lower end of the furnace body 4 of the drawing furnace 2. The distance detection sensors 11 and 12 are
The distance to the surface of the constricted portion 3B of the optical fiber preform 3 when the stretched preform 3A is manufactured by stretching the optical fiber preform 3 is detected. This distance detection sensor 11, 12
2 are used as a pair, but two or more sets are preferably provided at the lower end of the furnace body 4, and a pair of right and left and a pair of front and rear are preferably provided at the lower end of the furnace body 4 as shown in FIG. The distance detection sensors 11 and 12 may be of any type as long as they can detect the distance from the position of the distance detection sensor to the surface of the constricted portion 3B of the optical fiber preform 3, but a general laser sensor or the like is used. Since the optical fiber preform 3 is used in a state where it is softened and emits light, a heat ray absorption filter or the like is required. Also, since the environment around the drawing furnace 2 is at a high temperature, a sensor cooling device such as heat-resistant glass is provided for use. Will be done.

Reference numeral 13 denotes a chuck portion supporting base for supporting a base material feeding chuck portion 7 for holding the base material feeding dummy rod 6 and sending the optical fiber base material 3 into the drawing furnace 2 at a predetermined speed. . Reference numeral 14 denotes an XY stage to which a chuck support base 13 is attached.
3 is moved on the XY plane. Reference numeral 15 denotes a distance difference detection unit, which inputs the distance detection value detected by the distance detection sensor 11 and the distance detection value detected by the distance detection sensor 12. That is, the distance difference detection unit 15 is used in the distance detection sensor 1
1 from the distance detection sensor 11 to the surface of the constricted portion 3B of the optical fiber preform 3 and the distance detection sensor 12 detected by the distance detection sensor 12 to the surface of the constricted portion 3B of the optical fiber preform 3. From the center of the furnace body 4 of the drawing furnace 2 to the optical fiber preform 3
R1 to the detection side surface by the distance detection sensor 11 of
And the distance R2 from the center of the furnace body 4 of the drawing furnace 2 to the surface of the optical fiber preform 3 on the detection side by the distance detection sensor 12, and the difference between this distance R and 1 and the distance R2 (where the preform softening part is Is biased toward the side).

Reference numeral 16 denotes an XY stage control unit. The XY stage control unit 16 includes a pair of distance detection sensors 11 and 1 output from the distance difference detection unit 15.
The movement direction of the XY stage 14 based on the detection difference of 2.
The moving distance is calculated and the control amount is output to the XY stage 14. That is, the XY stage control unit 16 operates the XY stage 14 based on the detection data calculated by the distance difference detection unit 15,
By moving the base material feed chuck part 7 supported on the XY stage 14, the distance from the center of the furnace body 4 of the drawing furnace 2 to the detection side surface of the optical fiber base material 3 by the distance detection sensor 11 is constantly maintained. The XY stage 14 is moved so that the distance R1 is equal to the distance R2 from the center of the furnace body 4 of the drawing furnace 2 to the surface of the optical fiber preform 3 on the detection side of the distance detection sensor 12.

By controlling the XY stage 14 in this manner, the central axis of the softening portion 3C of the optical fiber preform 3 is always on the moving axis of the preform feeding dummy rod 6 and for preform taking-up. The dummy rod 8 is controlled to be on the moving axis, and the central axis of the softening portion 3C of the optical fiber preform 3 is controlled to be the center of the furnace body 4 of the drawing furnace 2. By controlling the XY stage 14 in this manner, the central axis of the softening portion 3C of the optical fiber preform 3 is controlled while sampling at predetermined time intervals.

[0017]

According to the first aspect of the present invention, glass particles are formed by a flame hydrolysis reaction to form a glass body, and a base material feeding dummy rod is provided at an upper portion and a base material receiving dummy rod is provided at a lower portion. In producing a stretched preform having a predetermined diameter by heating and softening the fused optical fiber preform in a stretching furnace, the position of the central axis of the stretched preform after stretching is detected, and the detected value is obtained. Based on this, the position of the central axis of the dummy rod for feeding the base material is adjusted, and the position of the central axis of the drawing base material is controlled so as to match the center axis of the drawing furnace, so that the drawing base material is manufactured. , The pre-stretching optical fiber preform is bent, or the preform feeding dummy rod and the preform pulling dummy rod are not attached straight to the prestretching optical fiber preform. Axes are attached to the rod and the dummy rod for collecting the base metal. Even if not occur, it is possible to obtain a bend-free elongated preform.

According to the second aspect of the present invention, the position of the center axis of the stretched base material after stretching is detected, and the optical fiber preform at the lower end of the stretching furnace is heated and softened to be stretched to the stretched base material. Since it is performed in the section, the central axis of the stretched base material can be easily detected. According to the invention of claim 3, a heater for heating the inside of the furnace is provided, glass particles are formed by a flame hydrolysis reaction to form a glass body, and a base material feeding dummy rod is provided at an upper portion and a base material is provided at a lower portion. A drawing furnace for inserting the optical fiber preform with the dummy dummy rod fused,
A dummy rod for feeding a base material is held above the drawing furnace to feed the base material into the drawing furnace at a predetermined speed, and a dummy rod for drawing the base material is held below the drawing furnace. And a preform chucking unit for drawing the preform from the drawing furnace at a predetermined speed, and heating and softening in the drawing furnace to draw the optical fiber preform to produce a drawn preform having a predetermined diameter. In a fiber preform drawing device, the lower end of the drawing furnace is opposed to each other for detecting the distance to the surface of the constricted part of the optical fiber preform when the optical fiber preform is drawn to produce the drawn preform. One or two or more pairs of distance detection sensors are provided, and a base material feeding chuck part for gripping the base material feeding dummy rod and sending the base material into the drawing furnace at a predetermined speed is provided via a chuck part support base. On an XY stage that can move on a horizontal plane And a distance difference detection unit for detecting and outputting a difference in distance from the distance from the sensor to the surface of the constricted portion of the optical fiber preform, which is detected by each of the pair of two sensors. An XY stage control unit that calculates a moving direction and a moving distance of the XY stage based on a detection difference between a pair of distance detection sensors output from the difference detection unit, and outputs a control amount to the XY stage. As a result, the pre-stretched optical fiber preform is bent, or the preform feed dummy rod and the preform take-up dummy rod are not attached straight to the prestretched optical fiber preform. Even if the base material feeding dummy rod and the base material receiving dummy rod are misaligned, a stretched base material without bending can be obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a method for stretching an optical fiber preform and an apparatus for stretching an optical fiber preform according to the present invention.

FIG. 2 is an overall configuration diagram showing a conventional optical fiber preform stretching device.

FIG. 3 is a diagram showing a softened state of the optical fiber preform shown in FIG.

FIG. 4 is a diagram showing an axially displaced state of an optical fiber preform stretched by the optical fiber preform stretching device shown in FIG.

[Explanation of symbols]

2 …………………………………………………… Drawing furnace 3 …………………………………………………… Optical fiber preform 3A …… …………………………………………… Stretched base metal 3B ……………………………………………… Constriction part 3C ……………………………… …………………… Softening part 4 …………………………………………………… Furnace body 5 ……………………………………………… …… Heater 6 ………………………………………………………… Dummy rod for feeding the base metal 7 …………………………………………………… Mother Material feeding chuck 8 ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… …… Matching part for preform 10 ……………………………………………… Drawer for optical fiber preform 11,12 …… …………………………………… Distance detection sensor 13 ……………………………………………… Chuck support 14 …………………………… ………………… XY stage 15 ……………………………………………… Distance difference detection unit 16 ………………………………………… ………Controller unit

Claims (3)

[Claims] 1. An optical fiber preform in which glass microparticles are formed by a flame hydrolysis reaction to form a glass body, and a preform feed dummy rod is fused to an upper part and a preform take-up dummy rod is fused to a lower part. When manufacturing a stretched base material having a predetermined diameter by heating and softening in a furnace, the position of the central axis of the stretched base material during stretching is detected, and the center of the base material feeding dummy rod is detected based on the detected value. A method for drawing an optical fiber preform for producing a drawn preform by adjusting the position of the axis and controlling the position of the central axis of the draw preform so as to coincide with the central axis of the drawing furnace. 2. The position of the central axis of the drawing base material during drawing is detected in a constricted part at the lower end of the drawing furnace, which heats and softens the optical fiber base material and draws it into the drawing base material. 1. The method for drawing an optical fiber preform according to 1. 3. A heater for heating the inside of the furnace is provided, glass fine particles are formed by a flame hydrolysis reaction to form a glass body, and a dummy rod for feeding a preform is provided at an upper portion and a dummy rod for taking up a preform at a lower portion. A drawing furnace for inserting the fused optical fiber base material, a base material feeding chuck part for holding the base material feeding dummy rod above the drawing furnace and sending the base material into the drawing furnace at a predetermined speed, and An optical fiber preform is provided below the drawing furnace for holding a dummy rod for drawing the preform and pulling out the preform from the drawing furnace at a predetermined speed. In an apparatus for stretching an optical fiber preform for producing a stretched preform having a predetermined diameter, an optical fiber preform for producing a stretched preform by stretching from the optical fiber preform at the lower end of the stretching furnace. Relative to detect the distance to the surface of the constricted part of One or two or more pairs of distance detecting sensors facing each other are provided, and a chuck portion for feeding the preform for grasping the dummy rod for preform feeding and sending the optical fiber preform into the drawing furnace at a predetermined speed is chucked. It is attached to an XY stage that is movable on a horizontal plane via a support, and the difference in distance from the distance from the sensor detected by each of the pair of sensors to the surface of the constricted portion of the optical fiber preform. A distance difference detection unit for detecting and outputting the X-Y stage is calculated based on the detection difference of the pair of distance detection sensors output from the distance difference detection unit. An optical fiber preform stretching device, characterized in that an XY stage control unit for outputting a controlled variable is provided on the Y stage.