JPS61209403A - Treatment of end face of optical fiber for infrared light - Google Patents

Abstract

PURPOSE:To form a smooth and good-quality fiber end by preforming the end face of a fiber for IR light by a blade or polishing then polishing chemically the end face. CONSTITUTION:The fiber for IR light is preliminarily cut by the blade or by polishing, by which the fiber end is preformed. The fiber end is then smoothed by polishing. The fiber is thereafter coated with a resin except the end face. The fiber end face is chemically polished. The chemical polishing liquid is selected according to the kind of the fiber. The end face of the fiber is slightly attached by the chemical reaction, quickly in a projecting part and slowly in a recess. The ruggedness such as flaw existing on the end face is thereby flattened. The fiber component supporting foreign matter, if gnawed to the end face, is attacked and therefore the foreign matter is dislodged and removed from the fiber end face. The fiber end is thereafter dipped in a suitable solvent to remove the resin coating layer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field The present invention relates to an end face treatment method for an infrared fiber.

The end face of the optical fiber must be finished with a flat surface. For this reason, it is often cut with a knife and polished with abrasive grains.

In the case of quartz glass fibers, the cut surface cut with a knife or the polished surface formed by polishing is used as the fiber end surface.

Since quartz fiber is hard and durable, a sufficiently smooth end surface was obtained by cutting and polishing.

However, the materials of infrared light fibers are generally soft. Therefore, there is a drawback that it is difficult to obtain a smooth end surface.

(b) Conventional technology and its problems There are the following types of infrared light fibers:

(1) Alkali metal halide crystals CsBr, CsI, etc. (2) Silver halide crystals AgCd, AgBr, etc. (3) Talicum halide crystals T (lcl, T6Br, TJl?I, etc.) These are crystalline fibers. It is the material.

Conventionally, these fibers have been cut with a cutter or polished with abrasive grains.

However, both methods have the following drawbacks.

FIG. 4 is a side view of the infrared fiber cut with a knife. FIG. 5 is an end view of the same.

The knife has chips and scratches on the cutting edge. With a knife like this,
When infrared fiber is cut, chips and scratches create streaks on the cut surface of the fiber. The cutting scratches 10 remaining as parallel streaks on the end face create unevenness on the end face.

Even if you thoroughly polish the tip of a knife, it is difficult to completely remove minute chips and scratches.

FIG. 6 is a side view of the end face of the infrared fiber which has been polished. FIG. 7 is an end view.

Since infrared fiber is soft, it is necessary to change the size of the abrasive grains in several stages, from large to small. Therefore, the time required for polishing is long. moreover,
During polishing, abrasive grains may become embedded in the soft fiber end face. In this way, groove-shaped polishing scratches 11 and defects of round polishing grains 12 remain on the end face of the fiber.

Such defects such as scratches and residual foreign matter on the end face of the infrared light fiber increase loss at the input/output end face of the fiber during optical transmission. Transmission efficiency decreases.

Furthermore, scratches on the fiber end face cause scattering of high-power Raded light. Laser light may also be absorbed by foreign substances such as abrasive grains. This generates a large amount of heat, which may damage the fiber end.

(i) Purpose The present invention aims to form a smooth, high-quality fiber end by preforming the end face of an infrared light fiber using a knife or polishing, and then chemically polishing the end face.

(1) Method of the present invention A feature of the present invention is that the infrared fiber is preformed and then chemically polished. As already mentioned, the infrared fiber is made of alkali metal halide (CsBr, C5I).
, silver halide (AgBr%AgC11), cricum halide (TIICII%TljBr, TllI)
There are crystalline fibers such as The present invention can be applied to either.

A method for forming an end face of an infrared fiber according to the present invention will be explained in order.

Cut the infrared fiber in advance with a knife or polishing,
Preform the fiber end face.

Polish the fiber end face to make it smooth. This is the same as before. Polishing is done using coarse abrasive grains and fine grains, gradually increasing the smoothness.

After this, the end faces are removed and coated with resin.

The resin coating is performed to prevent parts other than the end faces from undergoing chemical changes during chemical polishing.

The resin coating uses polyethylene, polystyrene, polyvinyl chloride, or fluororesin solution dissolved in a solvent. These solutions are applied to the fiber and dried. After this, the end face is re-polished to remove the resin attached to the end face. Expose the end face.

Next, the fiber end face is chemically polished.

The chemical polishing liquid is selected depending on the type of fiber.

(1) Alkali metal halides such as CsBr and CsI Since these are water-soluble, for example, a solution prepared by adding water to methyl alcohol, ethyl alcohol, etc. is used. The amount of water added is 0.1 to 5 wt% so that the fiber end face can be polished evenly.

(2) Use a silver halide sodium thiosulfate aqueous solution such as AgBr, Ag(J), or an aqueous solution prepared by adding sodium chloride to sodium thiosulfate.

A suitable concentration of sodium thiosulfate is 065 to 6 normal so that the fiber end face can be polished evenly.

(3) T(Ic(1, Tl; lBr, Tl1l
An aqueous solution of talicum/% ride potassium cyanide or hot water of 40 to 80°C is used.

FIG. 1 is a cross-sectional view schematically showing the process of chemically polishing the end face of an infrared fiber.

Around the infrared fiber 1, there is a resin coating layer 2 applied in the previous step.

A container 5 is filled with a chemical polishing liquid 3.

The end face 4 of the fiber 1 is immersed in a chemical polishing liquid 3. The chemical polishing liquid 3 causes a chemical reaction and gradually melts the end-face 4 of the fiber 1.

FIG. 2 is a cross-sectional view of the fiber before chemical polishing.

There are 10 cutting scratches, 11 polishing scratches, and 1 foreign matter on the end face of the fiber.
There are 3 etc.

Due to the chemical reaction, the end face of the fiber is melted little by little, with the protrusions melting faster and the concave parts melting slower. Therefore, irregularities such as scratches on the end face are smoothed out. Even if a foreign object is bitten into the end face, the fiber component supporting the foreign object is melted, so the foreign object separates from the fiber end face and is removed.

FIG. 3 is a sectional view near the end face of the infrared fiber after chemical polishing. The foreign object has been removed and almost no scars remain.

After chemical polishing in this manner, the fiber end is immersed in a suitable solvent to remove the resin coating layer 2.

In addition to the above-mentioned crystalline fibers, infrared light fibers include chalcogenide glass fibers such as As2S3, and heptadide galanium fibers such as zirconium heptide and gadolinicium fluoride.

The end face of such an infrared glass fiber can be treated using an appropriate chemical polishing liquid.

(e) Effects (1) Cutting scratches and polishing scratches on the end face of an infrared fiber can be easily removed in a short time, and a smooth end face can be obtained.

This is because unevenness and foreign matter on the fiber end face are removed by chemical reaction.

(2) No new abrasive grains are used. Not a physical effect,
The end face is polished by chemical action. Therefore, new abrasive grains are not embedded. During preforming polishing, the abrasive grains embedded in the fiber ends are removed.

(3) Infrared fibers are used for industrial CO2 laser processing machines and medical laser treatment. This is to guide CO2 laser light (10.6 μm). Since it is a high-power laser, if there are scratches or foreign objects on the end face, and light scattering or absorption occurs there, the fiber end will be damaged. In the present invention, since the end face of the fiber is free of foreign matter and smooth,
Almost no scattering or absorption occurs here, so there is no possibility of damaging the fiber end.

(Force) Example Both end faces of an AgBr fiber with a diameter of 1 ffφ and a length of 1 m were polished. I started with a 300 mm emery abrasive paper, then gradually changed to a finer abrasive paper, and finally sanded with a 42,000 grit abrasive paper. Sample A is a fiber that has been subjected to only this polishing.

Sample B was obtained by polishing with emery paper and then chemically polishing by the method of the present invention. After polishing, both ends of the fiber are immersed in an acetone solution of polyvinylidene heptafluoride resin. Dry this at 150°C. A coating layer of polyvinylidene resin is formed on the tip of the fiber.

Re-polish the fiber end with emery paper. Remove the resin attached to the end face and expose the fiber on the end face.

Immerse in a 1N sodium thiosulfate aqueous solution for 1 to 30 minutes. This is chemical polishing.

The polyvinylidene fluoride coating film is peeled off mechanically or by soaking it in an acetone solution.

Then, wash with pure water and dry. The sample made in this way is designated as B.

Sample A is according to the conventional method and sample B is according to the present invention. In order to check the loss on the end face, 10W
Co2 led light of 1 and 30 W was passed through both samples.

In sample A, the end face was not damaged by the 10 W laser beam. However, when exposed to 30W CO2 laser light,
The input end of the fiber is damaged. This means that there is a large loss due to scratches and foreign matter on the end face.

Sample B was not damaged at all by the LOW, 30W CO□ laser beam.

As described above, compared to the conventional infrared optical fiber end face treatment method, the infrared optical fiber end face treatment method of the present invention can finish the fiber end face smoothly and reduce energy loss at the end face. can. Therefore, it generates less heat, is not damaged, and can be used as a waveguide for a high-power Co2 laser.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the end face of an infrared fiber being chemically polished. FIG. 2 is a cross-sectional view of the vicinity of the fiber end face before chemical polishing. FIG. 3 is a cross-sectional view of the vicinity of the fiber end face after chemical polishing. FIG. 4 is a side view of the vicinity of the end face of the infrared optical fiber cut by a knife. FIG. 5 is an end view of the same. FIG. 6 is a side view of the vicinity of the end face of the infrared optical fiber after polishing with abrasive grains. FIG. 7 is an end view of the same. 1......Infrared light fiber 2...
・・・・・・Resin coating layer 3・・・・・・・・・
...Chemical polishing liquid 4...End face 5...Container 10...Cutting Wound 11...
...... Polishing scratches 12 ...... Abrasive grains 13 ... Foreign matter Inventor: Ken Takahashi - Noriyuki Yoshida Patent applicant: Sumitomo Electric Kogyo Co., Ltd. Application Agent Patent Attorney Shigeaki Akira Kawase? Arm) Figure 2: Before chemical polishing Figure 3: After chemical polishing

Claims (4)

[Claims] (1) An infrared optical fiber characterized in that the side surface of the infrared optical fiber near the fiber end is coated with a resin, and the end surface of the fiber is further immersed in a chemical polishing liquid for chemical polishing, and then the resin coating is removed. Edge treatment method. (2) The infrared light according to claim (1), wherein the infrared optical fiber is a crystalline fiber of CsBr or CsI, and the chemical polishing liquid is a methyl alcohol or ethyl alcohol solution added with water. Fiber end treatment method. (3) An end face treatment method for an infrared optical fiber according to claim (1), wherein the infrared optical fiber is a crystalline fiber of AgBr or AgCl, and the chemical polishing liquid is an aqueous sodium thiosulfate solution. (4) The method for end face treatment of an infrared optical fiber according to claim (1), wherein the infrared optical fiber is a TlBr or TlI crystalline fiber, and the chemical polishing liquid is warm water or an aqueous potassium cyanide solution.