JPH09255352A - Method for manufacturing flexible optical fiber bundle - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: It is easy to select and remove dirty single fibers without using an auxiliary agent for optical single fibers, and it is easy to perform the arraying work, and there is a drop or disorder. To provide a method for producing a flexible optical fiber bundle that is less likely to occur. SOLUTION: A first step of forming an optical single fiber 4 by coating an outer periphery of a core glass 1 having a high refractive index with a clad glass 2 having a low refractive index, and coating an outer periphery thereof with an acid-soluble glass 3. A second step of arranging the optical monofilaments 4 in an acid-soluble glass envelope 6 to make a multi-preform,
Before the second step, the glass component of the optical single fiber is corroded,
A surface modification treatment is performed to form many fine protrusions on the surface of the optical single fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a flexible optical fiber bundle.

[0002]

2. Description of the Related Art A method for manufacturing an optical fiber bundle for image transmission used in a medical or industrial endoscope is described below.
For example, the so-called acid elution method is well known in US Pat. No. 3,004,368 and the like.

In this acid elution method, the outer circumference of a core glass having a relatively high refractive index is coated with a clad glass having a relatively low refractive index, and the outer circumference of the clad glass is coated with an acid (1-2 N).
HCl, HNO ₃ ) of which is soluble in glass and whose outer diameter is about 500 μm and length is 200 to 300 mm to form a triple-layered optical monofilament. A large number (1000 to 50000) of these are regularly arranged in a jacket glass tube of ~ 30 mm, heated and stretched, cut into an appropriate length, and a fused optical fiber bundle is prepared. A flexible optical fiber bundle is manufactured by coating the above substance and immersing the whole in acid to elute the acid-soluble glass in the fused optical fiber bundle. In addition, JP-A-61-846
In No. 10, a step of immersing both ends of a multi-fiber fused with soluble glass between the strands of a fiber element coated with soluble glass in an eluent, and elution of the soluble glass with the eluent to remove the fiber element Is a step of impregnating and solidifying an insoluble resin in the eluate between the exposed fiber strands at both ends to form a fixed part at both ends, and immersing the multi-fiber having both fixed parts in the eluate, Disclosed is a method for manufacturing a flexible optical fiber bundle, which comprises a step of eluting soluble glass of multi-fiber, and the above-mentioned US Pat. No. 3,004,36.
In addition to the specification of No. 8, various methods for manufacturing a flexible optical fiber bundle have been proposed.

The same thing can be said in common in these production methods, in order to produce a good quality optical fiber bundle for image transmission, a large number of triple layers of optical monofilaments are regularly arranged in an acid-soluble outer glass tube. In doing so, it is necessary to prevent the arrangement from being distracted or disturbed and to prevent foreign matter from being mixed between the optical single fibers.

Therefore, in order to prevent the arrangement from becoming distorted or disturbed and to prevent foreign matter from being mixed between the optical single fibers,
Before carrying out the arraying work, it is necessary to wash the optical single fibers to remove dust, dirt and the like attached in the previous step.

However, the more thoroughly the cleaning is performed, the worse the sliding condition between the optical monofilaments becomes, which makes it very difficult to carry out the arraying work, which may cause dropout or disorder, or the optical monofilaments may be broken. There was a problem such as doing.

In order to solve this problem, Japanese Patent Publication No. 3-
In the publication No. 72019, in the work of regularly arranging a large number of optical single fibers, a lubricant which is sublimated or vaporized and decomposed to disappear in a subsequent heating step is coated on the single fibers to make them slippery, and the arrangement work is performed. A method of making a flexible optical fiber bundle that facilitates is disclosed. As the lubricant, for example, a fluorine-based solid lubricant containing PTFE (polytetrafluoroethylene) is used.

However, it is practically impossible to completely remove dust and dirt even if the optical single fibers are carefully washed, and in order to produce a higher quality optical fiber bundle, it is necessary to carry out before the arraying work. Although it is necessary to select and remove the dirty optical single fibers, normally, if the optical single fibers are coated with PTFE having large particles, there is a drawback that such selecting and removing operations become difficult.

It has also been found that when PTFE is vaporized and decomposed in a later heating step, bubbles may be generated in the optical fiber bundle, which causes the optical fiber bundle to deform and cause defects.

Therefore, the present applicant has filed Japanese Patent Application No. 7-2407.
In No. 07, a method of adhering finely powdered glass to optical single fibers was proposed. Finely powdered glass is applied to optical fiber bundles, especially as finely divided silica dispersed in a solvent. According to this method, since fine powder glass is adhered to the optical single fibers as a lubricant, even after the adhesion, the task of selecting and removing the contaminated single fibers is facilitated, and the arraying operation is easy to perform. It is useful because it is less likely to cause disorder or disorder.

However, if the fine powder silica is not uniformly dispersed in the solvent, the fine powder silica will also be non-uniformly attached to the optical single fiber, which may deform the optical single fiber during the heat drawing operation. There is. In addition, there is a problem that extra dust adheres before the arrangement work. Therefore, it was found that this method also has some room for improvement.

The present invention has been made in view of the above points, and the work of selecting and removing the contaminated single fiber without applying an auxiliary agent such as a lubricant or fine powder glass to the optical single fiber. It is an object of the present invention to provide a method for manufacturing a flexible optical fiber bundle that is easy to perform, arraying is easy, and is free from slippage and disorder.

[0013]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention can solve the above-mentioned conventional problems by performing a surface modification treatment for forming a large number of fine convex portions on the surface of an optical single fiber. It was found, and the present invention was able to be completed.

That is, according to the present invention, the core glass having a relatively high refractive index is coated with a clad glass having a relatively low refractive index, and the outer periphery thereof is coated with an acid-soluble glass to form an optical triple layer. Flexible optical fiber bundle comprising a first step of making single fibers and a second step of making multiple preforms by regularly arraying a plurality of the optical single fibers in an acid-soluble glass envelope. In the manufacturing method of 1., before the work of arranging the optical single fibers in the glass outer tube in the second step, a surface modification treatment for forming a large number of fine convex portions on the surface of the optical single fibers is performed. A method of manufacturing a flexible optical fiber bundle is provided.

The present invention also provides a method for producing the above flexible optical fiber bundle, wherein the surface modification treatment includes a step of corroding the glass component of the optical single fiber.

The present invention further provides the above-mentioned method for producing a flexible optical fiber bundle, which is surface-modified under a constant temperature and humidity condition.

Further, according to the present invention, the temperature condition is 20 to 3.
The present invention provides a method for producing the above flexible optical fiber bundle, which has a temperature of 0 ° C, preferably 25 to 30 ° C, and a relative humidity of 45 to 65%.

The present invention also provides the above-mentioned method for producing a flexible optical fiber bundle, wherein the convex portion has a substantially cylindrical or conical shape, the height is 70 to 200 nm, and the diameter is 350 to 1000 nm. It is provided. Further, the present invention is
Density of convex portion is 20000 to 1 per 1 mm ^{2 of} optical monofilament
The present invention provides a method for producing the above-mentioned flexible optical fiber bundle of 00000 pieces.

The present invention also provides a third step of producing a fused optical fiber bundle by heating and stretching the multi-preform obtained in the second step, and an acid-soluble glass in an intermediate portion of the fused optical fiber bundle. And a fourth step of eluting the flexible optical fiber bundle. Furthermore, the present invention provides the method for producing the flexible optical fiber bundle, wherein the fused optical fiber bundle is acid-treated in the fourth step while leaving both ends thereof.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in more detail with reference to the drawings. FIG. 1 shows the 3 used in the present invention.
It is a perspective view which shows the optical single fiber of a multilayer. The optical single fiber 4 has a core glass 1 (for example, barium flint glass) having a relatively high refractive index, and an acid resistant clad glass 2 (for example, crown glass) having a relatively low refractive index, which is coated on the outer periphery of the core glass 1. An acid-soluble glass 3 (for example, borosilicate glass) is coated so as to surround the outside. The acid-soluble glass 3 has, for example, 1 to 2
It can be dissolved in N HCl and HNO ₃ . The outer diameter of such an optical single fiber 4 is, for example, 250 μm, and it can be cut to an appropriate length, for example, 150 mm, washed and used in the next step.

Next, the surface modification treatment for forming a large number of fine projections on the surface of the optical single fiber will be described. According to the surface modification treatment of the present invention, the friction between the optical single fibers is reduced, the fibers become slippery, and the alignment work becomes easy.

This surface modification treatment is only required to form a large number of fine projections on the surface of the optical single fibers so that the optical single fibers can slip easily, and the specific means therefor is particularly limited. However, as described below, it is a simple and preferable method to cause so-called “burning” in the glass of the optical single fiber as shown below. The example is described below.

First, as shown in FIG. 2, a plurality of washed optical single fibers 4 are arranged on a rack 5 so as not to overlap, and 10 to 50 racks 5 are stacked and placed in a constant temperature and humidity chamber. The temperature and humidity conditions are variously changed depending on the desired form of the optical fiber bundle and the like. For example, the temperature is 20 to 30 ° C., preferably 25 to 30 ° C., and the relative humidity is 45 to 65%, preferably Conditions of 50-60% can be adopted. 7 to 6 for constant temperature and humidity
It is about 0 days. Under such conditions, the glass surface of the optical single fiber is burnt (corrosion), and as a result, a large number of convex portions are formed as shown in FIGS. Note that FIG. 3A is a plan view created from data obtained by measuring an area of about 4 nm × 4 nm on the glass surface with an AFM (atomic force microscope), and FIG. 3B is a BB line of FIG. 3A. A line sectional view, FIG. 3C is an enlarged view in which the height of the convex portion in FIG. 3B is magnified 10 times, and FIG. 4 is a range of about 4 nm × 4 nm on the glass surface based on the data measured by AFM. FIG. 3 is a perspective view in which is expressed in three dimensions.

Generally, the shape of the convex portion is substantially cylindrical or conical, and its size is 70 to 200n in height.
m, preferably 100 to 200 nm, the diameter is about 5 times the height, that is, 350 to 1000 nm, preferably 50.
About 0 to 1000 nm is preferable. If the shape is smaller than this range, the desired effect is not substantially obtained, and if the shape is larger, the optical effect may be adversely affected. The density of the convex portions in the optical single fiber is 20000 to 1000.
About 00 / mm ² is preferable.

Next, as shown in FIG. 5, for example, a borosilicate glass having the same composition as the above acid-soluble glass 3 and having an inner diameter of 40 mm, an outer diameter of 45 mm and a length of 200 mm.
In the glass sheath tube 6 which is soluble in acid, about 20000 optical monofilaments 4 which have been subjected to the above-mentioned surface modification treatment are arranged so as to satisfy regular hexagonal close packing to prepare a multi-preform. .

In this arrangement process, the friction between the optical single fibers is reduced by the formed convex portions, and the movement of the optical single fibers becomes very smooth. Therefore, at the same time as the arrangement work is completed in a short time, it is possible to achieve a neat arrangement without omission or disorder.

Subsequently, as shown in FIG. 6, the joint pipe 7 is held by the metal fitting 8 and the multi-preform is fed into the electric furnace 9. After the electric furnace 9 is heated to about 700 ° C. and one end of the lower part is softened so that it can be sufficiently stretched, the tip is forcibly pulled out by a tong or the like, and then the rubber roll 10 is sandwiched. The continuous drawing work,
The fused optical fiber bundle 11 is obtained.

The dimensions such as the outer diameter and the length of the fused optical fiber bundle 11 after heat drawing can be appropriately selected according to the intended use. The outer diameter of the fused optical fiber bundle 11 can be determined by the pulling speed of stretching, and the length thereof is determined by cutting at the lower part of the rubber roll 11.

Next, the fused optical fiber bundle 11 having an outer diameter of 2 mm and a length of 1 m, for example, is polished at both ends and then protected at both ends by heat shrink tubes and the like, and nitric acid at the middle part. Thus, the outermost coating layer of the acid-soluble glass is melted out, and a flexible high-quality optical fiber bundle can be manufactured.

The main feature of the present invention is to form a large number of fine projections on the surface of the optical single fiber. As described above, such fine protrusions can be preferably formed by intentionally corroding the burnt glass of the optical single fiber, that is, the glass. Note that the burnt glass is a matter well known to those skilled in the art. For example, when glass comes into contact with water, Na and the like in the glass are replaced by hydrogen in the water due to the ionization tendency, the pH of the water increases, and the glass becomes alkaline. Then, the alkaline water corrodes the glass surface, and a difference in the amount of corrosion occurs due to the difference in the composition of the glass surface, and a recess is formed on the surface. When the corrosion progresses to an appropriate level, the concave portion further expands,
As a result, it is considered that fine protrusions are generated.

This phenomenon similarly occurs even if the water content is in the air. That is, when water in the air adheres to the glass surface as water droplets, the ions are replaced as described above. Then, when the water droplets evaporate, the ionic component remains on the glass surface, and a slight recess is formed. Then, it is considered that the corrosion progresses as described above and a desired convex portion is formed. By producing many convex parts on the surface of the optical single fiber,
The friction between them is reduced, and the arrangement work becomes extremely easy. Further, in the present invention, it is not necessary to use an auxiliary agent for facilitating the arrangement work as in the conventional case, so that the dust can be easily selected. In the examples, the case where a flexible optical fiber bundle is manufactured by the acid elution method has been described, but the present invention is characterized in that a large number of triple-layered optical single fibers are regularly arranged in the outer glass tube. , Therefore,
First step of coating a core glass having a relatively high refractive index with a clad glass having a relatively low refractive index, and further coating an acid-soluble glass on the outer periphery thereof to form a triple-layer optical single fiber And a second step of forming a multi-preform by regularly arranging a large number of the above-mentioned optical single fibers in an acid-soluble glass envelope tube, and applying it to all other methods for producing a flexible optical fiber bundle. To be done.

[0032]

EFFECTS OF THE INVENTION According to the present invention, the monofilament is subjected to a surface modification treatment for forming a large number of fine projections on the surface of the optical monofilament before the operation of arranging the optical monofilament in the glass envelope. Friction between them is reduced, which facilitates arrangement work. In addition, since no auxiliary agent is used for the arraying work, it is easy to select and remove dirty single fibers, and it is easy to perform the arraying work, and it is possible to manufacture flexible optical fiber bundles that do not easily get lost or disturbed. A method is provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing a triple-layer optical single fiber used in the present invention.

FIG. 2 is a diagram showing a state in which optical single fibers are arranged on a plurality of racks.

FIG. 3A is a plan view created from data obtained by measuring an area of about 4 nm × 4 nm on a glass surface with an AFM, FIG. 3B is a sectional view taken along line BB of FIG. 3A, and FIG. It is the enlarged view which expanded the height of the convex part of 10 times.

FIG. 4 is a perspective view in which a range of about 4 nm × 4 nm on the glass surface is three-dimensionally represented based on the data measured by AFM.

FIG. 5 is a perspective view of a multi-preform used in the present invention.

FIG. 6 is a diagram for explaining a heating and stretching step in the present invention.

[Explanation of symbols]

 1 Core Glass 2 Clad Glass 3 Acid Soluble Glass 4 Optical Single Fiber 5 Rack 6 Glass Outer Tube 7 Joint Tube 8 Metal Fitting 9 Electric Furnace 10 Rubber Roll 11 Fused Optical Fiber Bundle

Claims (8)

[Claims] 1. A triple-layer optical single fiber is obtained by coating the outer periphery of a core glass having a relatively high refractive index with a clad glass having a relatively low refractive index, and further coating the outer periphery thereof with an acid-soluble glass. A method for producing a flexible optical fiber bundle, which comprises a first step of producing, and a second step of producing a multi-preform by regularly arranging a plurality of the optical single fibers in an acid-soluble glass envelope tube. In the above, before the work of arranging the optical single fibers in the glass outer tube in the second step, a surface modification treatment for forming a large number of fine convex portions on the surface of the optical single fibers is performed. Method for manufacturing flexible optical fiber bundle. 2. The method for producing a flexible optical fiber bundle according to claim 1, wherein the surface modification treatment includes a step of corroding the glass component of the optical single fiber. 3. The method for producing a flexible optical fiber bundle according to claim 2, wherein the surface modification treatment is performed under an arbitrary constant temperature and constant humidity condition. 4. The temperature condition is 20 to 30 ° C., preferably 2
5 to 30 ° C., and the humidity condition is 45 as relative humidity.
The method for producing a flexible optical fiber bundle according to claim 3, wherein the content is ˜65%. 5. The protrusion has a substantially cylindrical or conical shape with a height of 70 to 200 nm and a diameter of 350 to.
The method for producing a flexible optical fiber bundle according to claim 1, which has a thickness of 1000 nm. 6. The method for producing a flexible optical fiber bundle according to claim 1, wherein the density of the convex portions is 20,000 to 100,000 per 1 mm ^{2 of} the optical single fiber. 7. A third step of producing a fused optical fiber bundle by heating and stretching the multi-preform obtained in the second step, and eluting the acid-soluble glass in the intermediate portion of the fused optical fiber bundle. The method for producing a flexible optical fiber bundle according to claim 1, further comprising a fourth step. 8. The method for producing a flexible optical fiber bundle according to claim 7, wherein in the fourth step, the fused optical fiber bundle is treated with an acid while leaving both ends thereof.