JPS62226831A - Method for automatically regulating outside diameter of base material for optical fiber - Google Patents

Abstract

PURPOSE:To precisely, automatically and easily regulate the outside diameter of a base material for optical fiber to objective value by controlling the feed rate of a heating means basing on the deviation of both target values of the outside diameter which is decided from a core/ cladding ratio and present value of the outside diameter and performing flame abrasion. CONSTITUTION:The following distribution in the axial direction of a cladding diameter, namely, the distribution of the finished outside diameter of a base material 2 for optical fiber is calculated which is decided from a required core/cladding ratio in the basis on the measured value of the distribution in the axial direction of the core diameter of the base material 2 for optical fiber, and these value is preset as target value and inputted to an arithmetic control part 24 from an input operation part 22. Then the base material 2 is rotated via both a glass rod 4 for holding it and rotary chucks 8a, 8b, while allowing a bearer 14 of a burner 12 as a heating means to coincide with a position of a limit switch 26 which is regulated to the position butting to the left end of the base material 2 and arranged and heating the base material 2, the burner is transferred to the right and the base material 2 is subjected to flame abrasion. On the other hand, the outside diameter of the base material 2 just before being heated is measured by measuring devices 10a, 10b of the outside diameter and the transfer amount of the burner 12 is detected by a rotary encoder 20 and inputted to the arithmetic control part 24 and the feed rate of the burner 12 is controlled in accordance with the deviation value of both these measured value and the above-mentioned target value and changed and thereby the outside diameter of the base material 2 is regulated so as to attain the target value.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial application field The present invention relates to a method for automatically adjusting the outer diameter of an optical fiber preform (1) (b) Prior art and its problems In general, an optical fiber preform is The diameter of the optical fiber is reduced by stretching it using a spinning method or the like, but in this case, the same cross-sectional ratio between the core and the cladding of the optical fiber preform and the stretched optical fiber is maintained. Therefore, in order to obtain an optical fiber with a desired core-to-cladding ratio, the outer diameter of the optical fiber preform must be adjusted in advance so that the core-to-cladding ratio becomes the desired value at the optical fiber preform stage. This is necessary.

For this reason, conventionally, both ends of the optical fiber base material are attached to a lathe, etc., and while rotating, a part of the tip fiber base material is heated with a burner to vaporize and scatter, which is called flame polishing. The outer diameter along the axial direction was adjusted. However, in the conventional method, the outside diameter is adjusted entirely manually, which not only makes it difficult to accurately adjust the optical fiber base material to the required outside diameter, but also requires the skill of the operator. This is a factor that causes the core-to-cladding ratio of the optical fiber to deviate from the required range, such as variations in finishing accuracy depending on the degree of heat exchange.

The inventors of the present invention have conducted extensive studies in order to eliminate such conventional disadvantages, and have found that when flame polishing an optical fiber base material, the feeding speed of the heating means is adjusted to the target value of the outer diameter determined from the core-to-cladding ratio and the current value. It has been discovered that it is possible to freely adjust the outer diameter of the optical fiber preform by controlling it based on the deviation from the outer diameter value of the optical fiber preform.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to enable the outer diameter of an optical fiber preform to be accurately and automatically adjusted to a target value determined from the core-to-cladding ratio. purpose.

(C) Means for Solving the Problems In order to achieve the above object, the present invention provides a method for automatically adjusting the outer diameter of an optical fiber preform, in which the finishing of the optical fiber preform is determined based on the required core-to-cladding ratio. The outer diameter distribution is set in advance as a target value, and then, while rotating the optical fiber base material and sequentially moving the heating means along its axial direction, a part of the optical fiber base material is heated, vaporized, and scattered. With,
Measure the outer diameter of the optical fiber base material immediately before heating or during outer diameter adjustment with an outer diameter measuring device, successively compare the measured value and the target value at the measurement position to find the deviation between the two, and At least one of the feed rate and the amount of heat of the heating means is controlled according to the deviation value.

(d) Examples Hereinafter, the present invention will be explained in detail based on examples shown in the drawings.

FIG. 1 is a block diagram of an automatic outer diameter adjusting device for applying the method of the present invention. In the same figure, ■ is an automatic outer diameter adjustment device for an optical fiber preform, 2 is an optical fiber preform, 4 is a glass rod for gripping the optical fiber preform attached to the optical fiber preform 2, and 6a and 6b are main shafts. 6a, 6
Rotary chucks 8a and 8b are provided at b for gripping the glass rod 4 and rotating the optical fiber preform 2, respectively.

10aS IOb is a pair of outer diameter measuring instruments that are disposed facing each other perpendicular to the axial direction of the optical fiber preform 2, and in this example, a laser outer diameter measuring instrument is applied.

Further, 12 is a burner serving as a heating means for flame polishing the optical fiber preform 2. The outer diameter measuring instruments 10a, 10b and the burner 12 are both fixed to a support stand 14, and a screw shaft 16 for moving the support stand left and right in the figure is attached to this support stand 14. A support stand driving motor 18 is connected to one shaft end, and
A rotary encoder 20 is attached to the other shaft end of the screw shaft [6] for detecting the amount of movement of the support base 14 based on the number of rotations of the screw shaft [6]. Note that the amount of movement of the burner 12 can also be detected from changes in partial pressure resistance using a potentiometer instead of the rotary encoder 20.

Reference numeral 22 denotes an input operation section for inputting in advance a target value of the outer diameter distribution of the optical fiber preform determined from the required core-to-cladding ratio, and the screen of a personal computer can also be used. 24 determines the deviation between the heating straight outer diameter value of the optical fiber preform 2 measured by the outer diameter measuring instruments lOa and IOb and the target value input from the manual operation section 22, and adjusts the burner based on the deviation value. No. 14; Juryokuchohonga control o A seat Fuegaya control hall 96 is a limit switch that restricts the leftward movement of Jukomochidai 14. Next, a method of adjusting the outer diameter of the optical fiber preform 2 by applying the automatic outer diameter adjusting device 1 having such a configuration will be described.

First, the axial distribution of the core diameter of the optical fiber preform 2 is measured in advance using a preform analyzer, etc., and based on these measured values, the axial distribution of the cladding diameter determined from the required core-to-cladding ratio, that is, the optical fiber The finished outer diameter distribution of the base material 2 is determined, and these values are set as the target value DO.

The data of this target value Do is then input from the input operation section 22 to the arithmetic control section 24 . As a result, data on the target outer diameter Do is stored in the calculation control unit 24 for each position in the axial direction of the optical fiber preform 2.

Next, the glass rod 4 connected to the optical fiber preform 2 is held by the rotating chucks 8a, 8b, and the rotating chucks 8a, 8
b is rotated together with the optical fiber preform 2.

Also, align the support stand 4 of the burner 12 with the limit switch 26 at the left end in the figure. At this time, the position of the limit switch 26 is adjusted in advance so that the flame of the bar 12 hits the left end of the optical fiber preform 2. In this state, after igniting the burner 12 and setting the firepower to the required strength, the support base 14 is heated by the support base drive motor 18 while the burner 12 heats a part of the optical fiber base material 2. The fiber base material 2 is moved to the right along the axial direction. At this time, the heated portion of the optical fiber preform 2 heated by the burner 12 is vaporized and scattered, and the outer diameter thereof is reduced. Note that equivalent tension is not applied to the optical fiber preform 2 itself.

In parallel to the above, the outer diameter Dm of the optical fiber preform 2 immediately before heating is measured using the outer diameter measuring instruments 10aS and 10b. Further, the rotary encoder 12 detects the amount of movement of the burner 12. These outer diameter measurement value DI11 and burner movement amount are input to the calculation control unit 24, so the calculation control unit 24 calculates the measurement value Dm and the target value Do of the optical fiber preform 2 at the measurement position. By successive comparison, the deviation δ (=Dm-
Find Do). Further, the arithmetic control unit 24 controls the rotation of the support drive motor 18 in accordance with the deviation value δ to avoid changing the feed speed of the burner 12. That is, burner 1
There is a relationship between the feeding speed of No. 2 and the decrease in the outer diameter of the optical fiber base material 2 as shown in Fig. 2, so if the deviation value δ is large, the burner moving speed is slowed down, and when the deviation value δ is small, the burner movement speed is slowed down. increases its movement speed.

In this way, the burner 12 is moved along the axial direction of the optical fiber preform 2 at a speed corresponding to the deviation value δ.

When one process of flame polishing by the burner 12 is completed, the arithmetic control section 24 causes the support stand drive motor 18 to rotate in the reverse direction, and the support stand 14 is returned to the initial limit switch 26 position.

If the required outer diameter cannot be achieved with one adjustment, repeat the above operations such as rough adjustment and finish adjustment.
Finally, the outer diameter of the optical fiber preform is adjusted to a target value determined from the core-to-cladding ratio.

In order to confirm the method of the present invention, oxyhydrogen gas in burner 12, l
fi: Ht6512/min+of22Q/min, rotation speed of optical fiber base material: 50 rpms Movement speed of support stand 14: l
When automatic outer diameter adjustment was performed under the conditions of O~70+nn+/min, number of repetitions: 3 times, it was possible to finish the optical fiber base material with an outer diameter difference of within ±0, 1+n+n from the target value Do. .

In the above embodiment, only the moving speed of the burner 12 is changed and the thermal power of the burner 12 is kept constant, but conversely, the moving speed of the burner 12 is constant and the amount of oxyhydrogen gas sent to the burner 12 is changed. It is possible to adjust the outer diameter of the optical fiber preform by controlling the heating power. Furthermore, burner 1
Both the movement speed and firepower of No. 2 may be controlled at the same time.

Furthermore, in the above method, the outer diameter of the optical fiber preform 2 is measured with the outer diameter measuring devices 10a and 10b immediately before heating, but the diameter DC is measured during the adjustment of the heated outer diameter, and the target value D
Burner 12 according to the deviation value δ' (-Dc-Do) from o.
The speed of movement may be changed. In this case, the burner 12's Adjust movement speed.

(e) Effects As described above, according to the present invention, the outer diameter of the optical fiber preform can be precisely and automatically adjusted to the target value determined from the required core-to-cladding ratio. Therefore, the labor required for adjusting the outer diameter as in the conventional method is reduced, and excellent effects such as being able to obtain an optical fiber having a desired core-to-cladding ratio are exhibited.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an automatic outer diameter adjusting device to which the method of the present invention is applied, and FIG. 2 is a characteristic diagram showing the relationship between the burner feed speed and the decrease in the outer diameter of the optical fiber preform. l...Automatic outer diameter adjustment device for optical fiber base material, 2...
Optical fiber base material, IOa, 10b...outer diameter measuring device, 1
2... Heating means (burner), 24... Arithmetic control section.

Claims (1)

[Claims] (1) Preset the finished outer diameter distribution of the optical fiber base material determined by the required core-to-cladding ratio as a target value, and then:
While rotating the optical fiber preform, the heating means is sequentially moved along its axial direction to heat a part of the optical fiber preform to vaporize and scatter, and at the same time, the optical fiber preform is heated with an outer diameter measuring device. Measure the outer diameter just before or during outer diameter adjustment,
The measured value and the target value at the measurement position are successively compared to find a deviation between the two, and at least one of the feeding speed and the amount of heat of the heating means is controlled according to the deviation value. Automatic outer diameter adjustment method for fiber base material.