WO2005090248A1

WO2005090248A1 - Optical fiber preform processing method and optical fiber preform

Info

Publication number: WO2005090248A1
Application number: PCT/JP2005/004445
Authority: WO
Inventors: Hideki Fujii
Original assignee: Shin-Etsu Chemical Co., Ltd.
Priority date: 2004-03-18
Filing date: 2005-03-14
Publication date: 2005-09-29
Also published as: TW200533617A; KR20050093706A; JP2005263556A

Abstract

An optical fiber preform processing method in which no impurities adhere to the surface of an optical fiber matrix and an optical fiber preform are provided. The method for processing an optical fiber preform (1) supported at both ends by holding members while rotating the optical fiber matrix (1) and heating it by a burner flame is characterized in that prior to a drawing step for reducing the diameter of the optical fiber preform to a predetermined one, a flame polishing step is carried out. After the drawing step, another flame polishing step may be subsequently carried out. Further, the flame polishing step and the drawing step can be carried out in the same apparatus.

Description

Specification

Processing method of optical fiber preform and optical fiber preform

Technical field

The present invention relates to a method for stretching a large diameter optical fiber preform to a predetermined diameter by reducing the diameter of the optical fiber preform to a predetermined diameter, suppressing the adhesion of impurities to the surface of the preform, and obtaining an optical fiber preform at a high yield. The present invention relates to a method for processing an optical fiber preform and an optical fiber preform. This application is related to the following Japanese patent application. For those designated countries that are allowed to be incorporated by reference to the literature, the contents described in the following application are incorporated into this application by reference and are incorporated as a part of the description of this application.

Patent Application 2004— 078156 Application filed March 18, 2004 filed

Background art

[0002] Scratches or impurities on the surface of an optical fiber preform may cause a reduction in yield during drawing. Also, if the optical fiber preform has a bend and a diameter variation, it is difficult to set the optical fiber in the drawing machine, or the optical fiber having a uniform diameter may be obtained.

[0003] An optical fiber preform is required to have a smooth surface, no bending force, and no impurities. Therefore, in general, a series of steps are performed in the order of bending correction, stretching, and flame polishing by a burner flame using a chain hydrocarbon or hydrogen as a combustion gas using a glass lathe. Thus, the optical fiber preform is processed.

[0004] After passing through a stretching step of reducing the diameter of the optical fiber preform to a predetermined diameter in accordance with the drawing machine, a dummy glass rod is welded, flame polished, mounted on the drawing machine, and heated and melted. It is drawn in the shape of an optical fiber. At this time, since the dimensional accuracy of the optical fiber preform affects the dimensional accuracy of the optical fiber obtained by drawing, the outer diameter is measured at the neck-down part and two points immediately near the neck down during stretching, and based on this, There is known a method of obtaining an optical fiber preform having high dimensional accuracy by adjusting and controlling the stretching speed. (See Patent Document 1)

[0005] In general, the processing of the optical fiber preform is performed in a clean room or an environment similar thereto, and is performed in an atmosphere in which impurities do not adhere to the optical fiber preform as much as possible. However, after finishing the flame polishing step, which is the final step, or during flame polishing, impurities May be discovered. In that case, the operation of fusing and removing the impurity-attached portion is performed, and the yield is greatly reduced. Also, depending on the location of the attachment, the length may be short, and the entire base material may have to be discarded.

Therefore, a method for processing an optical fiber preform that does not cause impurities to adhere to the surface of the optical fiber preform is desired.

Patent Document 1: JP-A-56-9231

Disclosure of the invention

Problems to be solved by the invention

[0007] An object of the present invention is to provide a method for processing an optical fiber preform in which impurities do not adhere to the surface of the optical fiber preform, and an optical fiber preform.

Means for solving the problem

[0008] In the method for processing an optical fiber preform according to the present invention, the optical fiber preform is heated and processed by a burner flame while rotating an optical fiber preform supported at both ends by a holding member, for example, a chuck. A flame polishing step is performed prior to a stretching step of reducing the diameter of a material to a predetermined diameter.

In this case, the flame polishing step and the stretching step may be performed in the same apparatus. This makes it possible to perform the stretching process without moving the optical fiber preform to another device and without any time delay, thereby reducing the adhesion of new foreign matter after flame polishing. Furthermore, the working time can be reduced.

[0010] After the flame polishing step, the stretching step is preferably performed continuously. Further, after the stretching step, the flame polishing step may be further continuously performed.

[0011] In the stretching step, the surface of the optical fiber preform is heated at a higher temperature than in the flame polishing step. Specifically, the surface temperature of the optical fiber preform in the flame polishing step is 1800 ° C or more and less than 2200 ° C, and the surface temperature of the optical fiber preform in the drawing step is 2000 ° C or more and less than 2500 ° C. Is done. In this flame polishing step, the entire optical fiber preform is flame-polished. As a result, foreign substances and impurities attached to the optical fiber preform can be removed. The burner flame is a combustion flame using hydrogen and Z or a chain hydrocarbon as a combustion gas.

[0012] Alternatively, as another mode of the flame polishing step, foreign matter adhering to the optical fiber preform is removed. To remove, at least a portion of the optical fiber preform may be flame polished, followed by further flame polishing of the entire optical fiber preform. Thereby, the strain generated in the optical fiber preform due to the partially applied flame polishing can be appropriately removed.

[0013] The optical fiber preform of the present invention has been subjected to flame polishing and stretching using the above-described method for processing an optical fiber preform.

The invention's effect

In the method for processing an optical fiber preform according to the present invention, by performing the flame polishing step and the stretching step continuously, adhesion of impurities to the surface of the optical fiber preform is suppressed, and the optical fiber base material can be produced at a high yield. Material can be obtained.

Brief Description of Drawings

FIG. 1 is a schematic explanatory view illustrating a method for processing an optical fiber preform according to the present invention.

Explanation of symbols

[0016] 1 optical fiber preform,

2 Fixed chuck,

3 movable chuck,

Mo ¹ ~~~~~~

5 Norner.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the invention according to the scope of the claims, and all combinations of features described in the embodiments are described. Is not necessarily essential to the solution of the invention! / ,.

[0018] As a result of intensive studies, the present inventor has conducted a flame polishing step and a stretching step on the optical fiber preform continuously, instead of the conventional method, thereby forming the optical fiber preform. The present inventors have found that the adhesion of impurities to the surface of the base material is suppressed during processing, and have accomplished the present invention.

The method for processing an optical fiber preform of the present invention is performed as shown in FIG.

The optical fiber preform 1 has a fixed chuck 2 and a movable chuck 3 whose both ends are gripping members. , And rotated by the motor 4. The flame polishing is performed by heating the optical fiber preform with the burner 5 to a temperature of 1800 ° C. or more and less than 2200 ° C. and moving the optical fiber preform 1 along the optical fiber preform 1.

After completion of the flame polishing, the optical fiber preform is further heated by a burner 5 to a temperature of 2,000 ° C. or more and less than 2500 ° C., and the movable chuck 3 is pulled in accordance with the degree of softness of the preform. 1 is stretched to a predetermined diameter. In the drawings, the moving means of the burner 5, the pulling means and the adjustment control means of the movable chuck 3, the outer diameter measuring means, and the like are not shown.

The example shown in FIG. 1 is a method in which the optical fiber preform is horizontally supported and processed. Alternatively, the force may be performed while the optical fiber preform is vertically supported.

When examining impurities adhering to the surface of the preform during processing of the optical fiber preform, most of them are considered to be caused by metal materials such as iron, chromium, and nickel. Impurities adhering to the surface of these base materials have a force of several hundred microns or even a few millimeters. Actually, metal particles having a force of several microns or several tens of microns adhere and diffuse into the glass. Looks sharp. However, it is extremely difficult to extinguish these particles in the working environment.

[0022] Flame polishing is a method for removing impurities such as silica fine particles adhering to the surface, because a surface layer having a force of several microns and several tens of microns is melted and polished by heating at a relatively low temperature. It is heavily used. Further, this step is usually used in the final finishing step, because the distortion can be removed by removing the impurities attached to the surface. After flame polishing, the surface condition becomes smooth and it is difficult for new impurities to adhere.

[0023] The temperature at which the flame polishing force is applied is a force at which the surface temperature of the optical fiber preform is 1800 ° C or more and less than 2200 ° C, preferably 1900 ° C or more and less than 2100 ° C. . At a temperature of 2200 ° C. or higher, it becomes difficult to remove impurities and diffusion into the inside proceeds.

[0024] The subsequent stretching process is performed by heating to a higher temperature than the flame polishing, and therefore has a high ability to polish the surface with a flame. However, if impurities are attached, stress is applied by the flame. As a result, the impurities are buried in the surface of the base material before being polished, and gradually diffuse inside.

Therefore, in the flame polishing step, after the surface of the optical fiber preform is made to be free of impurities and hardly adhered to the impurities, the drawing step is performed without a pause, so that the preform is added. It is possible to suppress the attachment of impurities in the film.

[0025] The temperature at which the stretching process is performed is a force at which the surface temperature of the optical fiber preform is 2000 ° C or higher and lower than 2500 ° C, preferably 2200 ° C or higher and lower than 2500 ° C. If the temperature is lower than 2000 ° C, soft tension is insufficient, and a high tension is required for stretching, which increases the load on equipment.

[0026] By performing the flame polishing step and the stretching step continuously under the above conditions, adhesion of impurities to the surface of the optical fiber base material during processing of the optical fiber base material is suppressed, and the optical fiber is produced at a high yield. A base material can be obtained.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1

[0027] An optical fiber preform having an average diameter of 65 mm was set on a glass lathe equipped with a hydrogen flame burner having an oxygen nozzle for supplying oxygen as a supporting gas by connecting dummy rods to both ends.

First, the flame was polished with 250 L (liter) Zmin of hydrogen and 150 LZmin of oxygen. The surface temperature at this time was 2050 ° C. Subsequently, the film was stretched by a flame of 240 LZmin of hydrogen and 1 LOOLZmin of oxygen so that the surface temperature became 2200 ° C, so that the diameter became 60 mm. Subsequently, a series of 100 operations of performing flame polishing with 250 LZmin of hydrogen and 150 LZmin of oxygen were performed, and the finished surface was inspected. As a result, two of the 100 lines were found to have impurities exhibiting brown on the surface. The incidence was 2%.

Example 2

[0028] Dummy bars were connected to both ends of an optical fiber preform having an average diameter of 55 mm, and the optical fiber preform was set on a glass lathe.

First, flame polishing was performed with 270 LZmin of hydrogen and 170 LZmin of oxygen. The surface temperature at this time was 2100 ° C. Subsequently, the film was stretched with a flame of 260 LZ min of hydrogen and 150 LZ min of oxygen so that the surface temperature became 2400 ° C., so that the diameter became 50 mm. Subsequently, a series of 100 operations of performing flame polishing with 250 LZmin of hydrogen and 150 LZmin of oxygen were performed, and when the finished surface was inspected, one of the 100 lines showed a brown color on the surface with an incidence of 1%. Impurities were found.

(Comparative Example 1)

Except that flame polishing was not performed before stretching, 100 pieces were processed and the finished surface was inspected according to Example 1, and out of 100 pieces, 10 out of 100 pieces had an incidence of 10% and the surface had brown color. Was observed.

(Comparative Example 2)

Except for not performing flame polishing before stretching, 100 pieces were processed and the finished surface was inspected according to Example 2, and 9 out of 100 pieces had an incidence rate of 9% and had a brown surface. Was observed.

Industrial applicability

According to the optical fiber preform processing method of the present invention, the adhesion of impurities to the preform surface can be suppressed, and the optical fiber preform can be obtained with a high yield, which contributes to a reduction in manufacturing cost.

Claims

The scope of the claims

[1] A method in which an optical fiber preform whose both ends are supported by gripping members is heated and processed with a burner flame while rotating! A method for processing an optical fiber preform, wherein a flame polishing step is performed prior to a stretching step of reducing the diameter of the optical fiber preform to a predetermined diameter.

2. The method for processing an optical fiber preform according to claim 1, wherein after the flame polishing step, the drawing step is performed continuously.

3. The method for processing an optical fiber preform according to claim 2, wherein the flame polishing step and the stretching step are performed in the same apparatus.

[4] The method for processing an optical fiber preform according to any one of [1] to [3], wherein after the drawing step, the flame polishing step is further continuously performed.

5. The optical fiber preform processing method according to claim 1, wherein the stretching step heats a surface of the optical fiber preform at a higher temperature than the flame polishing step.

[6] The claim that the surface temperature of the optical fiber preform in the flame polishing step is 1800 ° C or more and less than 2200 ° C, and the surface temperature of the optical fiber preform in the drawing step is a temperature of 2000 ° C or more and less than 2500 ° C. Item 6. The method for processing an optical fiber preform according to any one of Items 1 to 5.

[7] The method for processing an optical fiber preform according to any one of claims 1 to 6, wherein in the flame polishing step, the entire optical fiber preform is flame-polished.

[8] The optical fiber preform according to any one of claims 1 to 6, wherein in the flame polishing step, after at least a part of the optical fiber preform is flame-polished, the entire optical fiber preform is further flame-polished. Processing method.

[9] The method for processing an optical fiber preform according to any one of claims 1 to 8, wherein the burner flame is a combustion flame using hydrogen and Z or a chain hydrocarbon as a combustion gas.

[10] An optical fiber preform which has been subjected to flame polishing and stretching using the method for processing an optical fiber preform according to any one of claims 1 to 9.