JPH0756025A - Production of optical fiber - Google Patents

Abstract

PURPOSE:To suppress the generation of bending in a free state at the connecting ends of spun optical fibers, to expedite and facilitate the operation to connect the optical fibers and to improve the connecting system thereof by grinding or washing with detergent the preform surface prior to spinning. CONSTITUTION:The preform surface on which foreign matter is physically or chemically stuck is removed together with the foreign matter by grinding the entire surface of the preform. The foreign matter sticking to the preform surface is otherwise removed by washing the entire surface thereof. As a result, the preform to be subjected to spinning is made into the state that the foreign matter is not stuck to its surface. The heterogeneity of the optical fiber by the foreign matter sticking thereto is thus eliminated and the bending at the front end of the optical fiber occurring in the heterogeneity is prevented. The operation to connect the optical fibers in fusion splicing of the optical fibers is expedited and facilitated and the transmission efficiency of the juncture is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to processing of a preform for optical fiber spinning in an optical fiber manufacturing process, in which a spliced optical fiber is bent at a connecting end in a free state. This makes it possible to quickly and easily connect the fibers of the optical fiber tape, and to significantly improve the connection accuracy.

[0002]

2. Description of the Related Art Preform for optical fiber spinning
Is spun in a heating furnace for spinning and molded into an optical fiber,
The molded optical fiber is immediately coated with resin to be optically and mechanically protected to form an optical fiber element wire. In many cases, a large number of optical fiber strands are arranged and further covered collectively to form a tape-shaped optical fiber tape. The coating of the tip of the optical fiber tape thus produced is removed to leave the tip of the optical fiber 1 exposed, and the optical fiber 1 is abutted in the fusion splicing device to be fused and connected to form a long communication line. If the tip of the optical fiber is exposed for this fusion splicing, the tip of the optical fiber becomes free,
When it is slightly deformed (bent) and butt welded,
The cores (optical axes) of the tips of the optical fibers facing each other are slightly deviated, which lowers the splicing accuracy, increases the transmission loss at the spliced portion, and often lowers the transmission efficiency. It is relatively easy to match the optical axes of the single-fiber optical fiber wires by rotating the splicing end in the V groove 3 of the positioning base 2 of the fusion splicing device (see FIG. 1). In the case of an optical fiber tape in which a large number of optical fiber element wires are arranged and integrated, it is impossible to match the optical axes of all the optical fibers. In order to reduce the transmission loss due to the shift of the optical axis at the connecting portion of the optical fiber tape, the bending of the tip of the optical fiber 1 must be reduced as much as possible. As a result of research, it has been found that the cause of the slight bending of the tip of the optical fiber 1 lies in the base material used for spinning the optical fiber. That is, after molding the base material, a minute foreign substance 4 adheres to the surface of the base material before it is subjected to spinning, and when this foreign substance is melted and heated in a spinning furnace, it chemically reacts with quartz constituting the base material. As a result, an inhomogeneous portion different from quartz is formed on the surface of the base material, and this inhomogeneous portion is slightly different from quartz at the softening point, the strain point, etc., so that the homogeneity of the spun optical fiber 1 is impaired. This is because, after coating immediately after spinning, as the cooling proceeds, thermal strain occurs due to the difference in curing rate due to the inhomogeneity, and residual stress due to this thermal strain occurs. When the coating is removed and released from the restraint by the coating, the tip of the optical fiber 1 causes the above bending due to the residual stress (see FIG. 2). The foreign matter 4 includes human sweat, minute foreign matter in the air, and the like. Therefore, in order to prevent the above-mentioned bending of the optical fiber as much as possible, it is important to remove the foreign matter on the surface of the base material as much as possible and then provide the optical fiber for spinning. However, by thoroughly managing the base material so that human sweat and foreign matter in the environment do not adhere to the surface of the base material between the time when the base material is molded and the time when it is installed in the spinning heating furnace, You can solve the problem. For that purpose, when taking out the base material from the base material forming furnace, when transporting the base material, and when mounting the base material in the heating furnace for spinning,
These operations may be performed by an automatic device such as a manipulator and an automatic transfer device in a controlled closed space without manual labor, or when manually performed, when the resin is removed in the molding furnace when taken out from the molding furnace. When packaging the base material with a sheet and removing the base material from the forming furnace and when carrying it,
Wearing clothes and gloves that prevent sweat from escaping and adhering to the spinning furnace is recommended. However, the former is problematic in terms of cost, and the latter is not easy to implement 100% thorough management in practice. Therefore, it is cheaper and more reliable technical solution to take measures to remove foreign matter as much as possible before subjecting it to spinning, assuming that foreign matter adheres to the matrix. It is a measure.

[0003]

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned problem of bending of the tip of an optical fiber, and therefore, to remove foreign matter on the surface of a spinning base material efficiently and effectively before spinning. That is the subject.

[0004]

Means for Solving the Problems The means of the invention (claim 1) (hereinafter referred to as "first invention") taken to solve the above problems polishes the surface of a base material before spinning. That is.

The means of the invention described in [Claim 2] (hereinafter referred to as "second invention") taken to solve the above-mentioned problems is to wash the surface of the base material with a detergent before spinning. .

The "polishing" in the means of the first aspect of the invention is not a so-called general polishing treatment for smoothing the surface by removing fine scratches and irregularities on the surface, but for the surface of the base material. It means polishing to completely remove the surface layer in which foreign matter such as adhered sweat has penetrated.

[0007]

[Operation] Since the entire surface of the base material is polished by the means of the first invention to remove the surface of the base material physically or chemically attached to the base material together with the foreign material, the mother material to be used for spinning The material is in a state where no foreign matter is attached to its surface. Typical polishing means for this purpose are flame polishing and chemical polishing with hydrofluoric acid. When chemical polishing with hydrofluoric acid is adopted, it is desirable to remove hydrofluoric acid adhering to the surface by washing with water after completion of polishing. Since the entire surface layer is removed by polishing, foreign matter that has penetrated and adhered to the surface can be removed efficiently and effectively.

Further, the second means cleans the entire surface of the base material to remove the foreign matter adhering to the surface, so that the base material used for spinning has no foreign matter adhering to the surface. become. Typical cleaning means for this purpose are cleaning with water and cleaning with a chemical cleaning agent. When a cleaning means using a chemical cleaning agent is adopted, it is necessary to remove the chemical cleaning agent adhering to the surface by cleaning with water after the cleaning is completed. Since the foreign matter is removed by washing, the foreign matter that permeates and adheres to the surface is efficiently and effectively washed away and removed.

[0009]

[Examples] Next, examples will be described. In the first embodiment of the invention, the base material is flame-polished in a furnace to remove the surface layer by about 200 μm. The combustion gas in this case is oxygen and hydrogen, and the flame temperature is set to about 2000 ° C.
Perform flame polishing for minutes. As a result of testing an optical fiber having a wire diameter of 125 μm spun from the flame-polished base material as described above, a coating removal length of 10 out of 100 tests was performed.
The maximum eccentricity of the tip of the mm type was 5.0 μm, and the average eccentricity was 2.5 μm. However, the test results for the same optical fiber spun by the conventional method without performing the polishing treatment according to the present invention are as follows:
The maximum eccentricity at the tip of a coating removal length of 10 mm is 1
The average eccentricity was 4.5 μm and the average eccentricity was 8 μm.

The base material is chemically polished with hydrofluoric acid in a furnace to remove the surface layer by 100 μm. The polishing agent in this case is hydrofluoric acid having a concentration of 10% and a temperature of 25 ° C., and chemical polishing is performed for 20 minutes. As a result of testing an optical fiber having a wire diameter of 125 μm spun from the base material chemically polished in this way, the maximum eccentricity of the tip of the optical fiber having the coating removed by 10 mm was 5.5 μm and the average eccentricity was 100 out of 100 tests. The amount was 2.5 μm.

In the second embodiment of the invention, the base material is washed with water to remove foreign matter on the surface. In this case, the washing water is distilled water at a temperature of 20 ° C., and distilled water having a pressure of 3 Kg / cm ² is sprayed onto the surface of the base material at 20 m / sec and 0.002 m ³ / sec for washing for 5 minutes. As a result of testing an optical fiber having a wire diameter of 125 μm spun from the base material washed in this way, the coating was 10 times out of 100 times.
The maximum eccentricity of the tip of the optical fiber after mm removal is 5.0μ
m, and the average amount of eccentricity was 2.5 μm.

The base material is cleaned with a chemical cleaning agent to remove foreign matter on the surface. In this case, the chemical cleaning agent is a 1% solution of a surfactant at a temperature of 20 ° C., and the chemical cleaning agent having a pressure of 3 Kg / cm ² is sprayed onto the surface of the base material at 20 m / sec and 0.002 m ³ / sec for 3 minutes. To wash. Then, it is washed with distilled water to remove the chemical cleaning agent attached to the surface of the base material. Wire diameter of 125 μm spun from the base material washed in this way
As a result of testing the optical fiber of 100 times,
The maximum amount of eccentricity at the tip of the optical fiber with the coating removed by 10 mm was 5.5 μm, and the average amount of eccentricity was 2.5 μm. A cleaning method may be adopted in which the base material is dipped in a cleaning tank of a chemical cleaning agent, and the cleaning agent in the cleaning tank is circulated to perform cleaning for several minutes. The test results of the optical fiber spun from the base material washed in this way are not significantly different from those obtained by the above-mentioned cleaning method using the chemical cleaning agent.

Further, the surface of the base material is wiped with a cloth which is sufficiently impregnated with a cleaning agent having high volatility and permeability, and foreign matter which has penetrated and adhered to the surface is removed. In this case, the cloth impregnated with the cleaning agent must have high abrasion resistance to the extent that abrasion powder of the cloth does not adhere to the surface of the base material due to friction with the base material. When the woven fabric made of polyester long fibers is impregnated with ethyl alcohol and the surface of the base material is sufficiently wiped by hand, the above test results are the maximum eccentricity of the tip of the optical fiber with the coating removed by 10 mm out of 100 tests. The amount was 6.1 μm, and the average amount of eccentricity was 3.3 μm.

[0014]

[Effect] As described in detail above, the present invention eliminates the inhomogeneity of the optical fiber due to the foreign matter adhering to the base material,
Eliminating the problems of the above-mentioned conventional technology resulting from the non-uniformity, quick connection work in the optical fiber fusion splicing,
It is possible to make it easy and to significantly improve the transmission efficiency of the connecting portion. To remove the surface layer, a physical polishing method using an abrasive such as buff can be adopted,
When such a physical polishing method is used, innumerable minute scratches are left on the surface of the base material, and the quality of the spun optical fiber is significantly deteriorated due to the scratches. However, both of the above means according to the present invention are extremely safe because they do not leave scratches on the surface of the base material.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state where an optical fiber is placed in a V groove of a positioning table of a fusion splicing device for optical fiber strands.

FIG. 2 is a partially enlarged perspective view of the optical fiber in a state of being bent due to adhesion of foreign matter.

[Explanation of symbols]

 1 ... Optical fiber 2 ... Positioning stand 3 ... V groove 4 ... Foreign matter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Takahashi 1440 Rokuzaki, Sakura City, Chiba Prefecture Fujikura Ltd. Sakura Factory

Claims (2)

[Claims] 1. A method for producing an optical fiber, wherein a surface of a base material is polished before spinning to remove a surface layer in which foreign matter such as sweat has penetrated. 2. A method for producing an optical fiber, wherein the surface of a base material is washed with a detergent before spinning to remove foreign substances attached to the surface layer.