JPS5890601A - Manufacture of image fiber - Google Patents

Abstract

PURPOSE:To prevent the generation of foams during fusion and wire drawing by heating organic impurities existing on the surface of optical fibers and a jacket pipe after inserting numbers of optical fibers into the glass-made jacket, and removing them through hydrogenation and oxidation successively. CONSTITUTION:Numbers of optical fibers 1 are packed lengthwise in a jacket 3 made of glass to form a jacket fiber group 3. To remove organic contaminating materials sticking strongly to surfaces of the optical fibers 1 and jacket pipe 3, the jacket 3 is filled with gaseous H2 and then heated at >=100 deg.C for hydrogenation to produce H2O, which is discharged by producing a vacuum. Then, gaseous O2 is introduced and heat oxidation is carried out to obtain gaseous CO2, thus removing all organic materials. Further, after O2 is substituted by inert gas, they are united by deposition under a vacuum and wire drawing is carried out to obtain a foam-free image fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an image fiber by drawing a large number of optical fibers at once.

This type of manufacturing method involves heating and melting a large number (for example, several thousand to tens of thousands) of optical fibers with an outer diameter of several hundred μm filled in a glass jacket tube with one end closed. After the pipes are integrated, the diameter of the pipe is reduced, or the inside of the jacket pipe is reduced in pressure without being integrated, and the diameter of the pipe is reduced.

By the way, a problem with such a manufacturing method is the generation of bubbles during the heating process such as during melting and integration or during wire drawing.

The image fiber has a sharp point when used for long image transmission in units of 100 m, and because it is enlarged and observed by attaching a lens system to both ends of the fiber, minute air bubbles (same as the pixel diameter) are created in the transmission path. If even one particle (with a size of several μmφ) is present, this causes a dark spot (a defect on the screen due to missing pixels), which poses a problem in terms of the performance of the image guide.

The following are the main causes of bubbles.

1) Gas existing between the optical fiber strands is trapped by surrounding welding 11) Contamination of foreign matter 11) Contamination of the material surface Therefore, as a countermeasure against these problems, vacuum welding has traditionally been used for the above 1). 11) and 111) above have been dealt with by means such as ultrasonic cleaning, acid cleaning, or combustion treatment with oxygen, and it is true that they are quite effective against i) and ii). I was hopeful.

However, no sufficient effect could be expected for the above 111).

Of course, this does not mean that all surface contamination cannot be removed, but there are certain substances, namely organic contaminants, that can be removed.
This substance is called the Griffith flow on the glass surface1.
A problem arises when the mounting base is attached to the inside of minute scratches of 0-''w or less.

Moreover, the same substance is always contained in acid solutions or cleaning water, albeit in small amounts, so when acid cleaning is used to clean the glass surface, the same substance will not adhere to the glass surface. is inevitable.

During the heating process, that is, during collapse or drawing, this organic material undergoes thermal history and generates gas, resulting in the formation of bubbles.

In the low viscosity region of glass, these microscopic bubbles can aggregate and become gigantic, exposing them as large defects. , after cleaning by heat treatment in a predetermined gas atmosphere,
The idea is to solve the above problem by drawing lines, and to explain this with reference to the embodiment shown in the drawings, first, an optical fiber wire m(1)... and a glass jacket are used. The pipe (2) is cleaned using ultrasonic waves and an acid such as sulfuric acid. This point is similar to the conventional example.

Next, the optical fiber strand (11(1)...
The inside of the gastric tube (2) is densely filled so that their longitudinal force matches that of the jacket tube (2), as shown in FIG. After introducing hydrogen gas into the jacket tube (2) of the obtained jacket fiber group (3) and creating a hydrogen gas atmosphere inside, the jacket fiber group was
By heating the optical fiber to a temperature higher than Molecular compound 1 will be converted 0 Even if the organic compound is in a fine scratch like a Griffith flow, hydrogen has a small atomic radius, so it acts on the organic compound inside the hole and converts it. Hydrogenate.

After this step is completed, hydrogen and low-molecular organic compounds are evacuated, oxygen is introduced into the jacket tube (2) to create an oxygen atmosphere, and then heated to a temperature of 100°C or higher. As a result, the organic compounds remaining inside the jacket tube (2) are completely oxidized to CO□ and H2O. ...and the surface of the jacket tube (2) is activated, so the process proceeds extremely smoothly.

When the above oxidation reaction is completed, after exhausting the oxygen and reaction products inside the jacket tube (2), an inert gas is introduced into the stomach tube (2) to create an inert gas atmosphere inside. .

Next, while exhausting the gas inside the jacket tube (2) from the open end, the jacket fiber group (3) is heated gradually from the closed end toward the open end at a temperature higher than the softening point of the glass. However, it is completely welded and integrated to form the image fiber base material.

Finally, the base material is drawn to obtain an image fiber.

In the above example, the jacket fiber group (3) is collapsed to form the image fiber base material and then drawn, but the jacket tube (2) is drawn without collapsing.
) It is also possible to directly draw an image fiber while reducing the internal pressure.

In addition, there are no restrictions on the type of glass used as the material for the jacket fiber group (3) (e.g., multi-component glass, quartz, etc.), and as a gas to be subjected to hydrogenation or oxidation reactions, it is possible to The gas is not limited to the above-mentioned types, and may be a single gas or a mixture of gases.

Figure 2 shows the equipment used for the above-mentioned cleaning process, with the dashed line frame I showing the exhaust system and the broken line frame N showing the gas introduction system. (3) is connected to either the exhaust system or the gas introduction system.

In the figure, (5) and (6) are actuated by an oil diffusion pump and an oil rotary pump, respectively, and by operating these, the inside of the jacket pipe (2) is evacuated.

The degree of vacuum inside the spacer tube (2) is determined by the Macleauto gauge (
7).

Furthermore, in the figure, (8)+91 and ao indicate cylinders for hydrogen gas, helium gas, oxygen gas, etc., respectively.

Here, we will discuss a more specific example using the same device.
A quartz glass jacketed tube with an inner diameter of 42wn and a length of 1m (
After immersing and cleaning 2) and 2) in 20% dilute sulfuric acid, they were immersed in water for ultrasonic cleaning, and after cleaning, they were dried.

After the dried optical fiber wires (1) (11...) are bundled and inserted into the jacket tube (2), after connecting the jacket fiber, open the switching cock (4) to the exhaust system I side to diffuse oil. Operate the pump (5) and oil rotary pump (6) and exhaust the inside of the jacket pipe (2) to 10-' torr using the macroauto gauge (7). After exhausting to 0, turn the switching cock (4) to introduce gas. Open it to the system side, then open the needle pulp cod, and introduce hydrogen gas into the jacket pipe (2) until it reaches normal pressure while watching the pressure gauge α. 2 at a temperature of 800℃
After heating for a period of time to perform a hydrogenation reaction, the inside of the jacket pipe (2) was evacuated by the exhaust system I in the same manner as above, and then oxygen was introduced into the jacket pipe (2) from the gas introduction system. 3 again at a temperature of 800℃
Heated for 0 minutes to perform an oxidation reaction. After this, the inside of the jacket tube (2) was evacuated in the same manner as above, and helium gas was introduced from the gas introduction system to completely replace the oxygen inside with helium gas. After that, exhaust the inside of the shaken pipe (2) using the exhaust system I.
The jacket fiber group (3) was heated and softened from the closed end to the open end of the jacket tube (2) using a hydrogen flame burner, and the jacket fiber group (3) was completely collapsed.

The image fiber preform after collapse was drawn to a predetermined outer diameter to obtain an image fiber with a length of 200 m.

No dark spots were observed over the entire length of this image fiber.

Next, to describe another specific example, 12,000 flint-based glass optical fibers having been washed with dilute sulfuric acid and dried and having an outer diameter of 200 μm are bundled and inserted into a similarly treated flint-based glass jacket tube having an inner diameter of 23 mm. .

Next, as described in the above specific example, the jacketed fiber group thus obtained is connected to the gas treatment apparatus shown in FIG. 2, and gas treatment is performed in the same manner as in the above specific example.

However, the heating temperature in the electric furnace shall be 50℃. After cleaning under such conditions, without going through the collapse process,
An image fiber having a length of 50 m was obtained by directly drawing the jacket tube (2) to a predetermined outer diameter while reducing the pressure inside the jacket tube (2).

When we cut this image fiber into 10 parts every 5 m and performed a dark spot inspection, only one dark spot was found among the 10 image fibers, and good images were obtained for the rest. 〇As described above, in the present invention, the jack, cut fiber 6, which is composed of an optical fiber and a jacket tube,
The group was sequentially heated in a reducing gas atmosphere containing hydrogen atoms and then in an oxidizing gas atmosphere containing oxygen atoms to sequentially hydrogenate and oxidize organic contaminants on the surfaces of the optical fiber and jacket tube. After that, the salmon throat tube was delineated in a vacuum, so that organic contaminants adsorbed or adhered to the surface of the optical fiber and the salmon tube were not hydrogenated or oxidized even if they were inside the Griffith flow. Because it became possible to remove by
During heating, bubbles (dark spots) are not generated due to thermal decomposition of contaminants, and therefore good image quality without image defects can be obtained.

Furthermore, since the yield is improved, costs can be reduced accordingly.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a group of jacketed fibers in which optical 2 eyes and ... Optical fiber wire (2) ... Jacket tube (3) ... Jacket fiber group patent applicant Makoto Ito

Claims (2)

[Claims] (1) In a method for manufacturing an image fiber in which a large number of optical fibers are inserted into a glass jacket tube and then the diameter of these fibers is reduced all at once, a group of Janat fibers consisting of the above-mentioned optical fibers and a Jachit tube is heated with hydrogen. After successively heating in a reducing gas atmosphere containing atoms and then in an oxidizing gas atmosphere containing oxygen atoms to sequentially hydrogenate and oxidize the organic contaminants on the surfaces of the optical fiber and Janut tube, the optical fiber and the Janut tube are heated in a vacuum state. A manufacturing method for ImageFi/< characterized by reducing the diameter of the Jakutfainok group with (2) After creating a hydrogen gas atmosphere inside the jacket pipe, 10
The method for manufacturing an image fiber according to claim 1, which comprises heating at a temperature of 0° C. or higher, then creating an oxygen atmosphere inside the jacket tube, and then heating at a temperature of 100° C. or higher. . +31 After sequentially hydrogenating and oxidizing organic contaminants, the jacket fiber group is placed in an inert gas atmosphere, and then the diameter of the image fiber is reduced in a vacuum state. Production method.