JPS5828706A - Production of optical fiber bundle having flexibility - Google Patents

Abstract

PURPOSE:To produce an optical fiber bundle having flexibility with high efficiency by an acid eluting method, by adhering the powder or fiber of the glass soluble to acid with an adhesive which can be removed away by heat and then using an outer coat tube having high accuracy of measurement. CONSTITUTION:A slip is obtained by mixing the powder of the glass soluble to acid and an adhesive like nitrocellulose, etc. that can be removed away by heat. Then a circular or polygonal hollow outer coat tube 23a of the acid soluble glass with use of a metallic mold and a casting molding process, etc. When the fibers are used in place of the powder, the fibers 31 are put densely into a metallic mold 30 and an adhesive 32 of the same kind is poured into the spaces among the fibers 31 to obtain an outer coat tube. Then the fibers 1 coated with acidproof optical fibers by means of the acid soluble glass are regularly arranged into the tube 23a. These fibers 1 are then melt-stuck with heat and stretched. The edge part of an optical fiber bundle thus obtained is coated with the acidproof resin, and then the entire bundle is dipped in acid. Thus an optical fiber bundle having flexibility is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flexible optical fiber bundle. More specifically, the present invention relates to a method of manufacturing an optical fiber bundle in which each optical fiber is fixed at its end and other parts are flexible.

When the optical fiber bundle is used as an image guide, and the ends of the optical fiber bundle are used as mirrors, etc., the optical fibers are fixed to each other at both ends, and the intermediate portion is flexible. It is required to be flexible. By the way, various methods have been proposed for manufacturing optical fiber bundles having such fixed end portions and flexible intermediate portions.

For example, a core glass with a high refractive index is placed in the inner crucible of a double crucible, and a covering glass with a low refractive index is placed in the outer crucible, the double crucible is heated to an appropriate temperature, and both glasses are inserted through the bottom hole of the crucible. Coat the core glass with the coating glass, wind the obtained optical fiber into a row of loops without gaps, fix one place of the loop with adhesive, and then loop it in a row in the same way as before. The loop-shaped optical fiber bundle is wound into a shape without any gaps, fixed with adhesive at the fixed part of the previously formed loop, and the operation is repeated to obtain a loop-shaped optical fiber bundle with a desired thickness. A method for manufacturing a flexible optical fiber bundle for an image guide is known, which comprises cutting the optical fibers at right angles to the longitudinal direction of the optical fibers at the center, and then polishing the two cut surfaces. In this method, optical fibers of a desired thickness (e.g. 20μ) can be made in one heating step.
The subsequent manufacturing process, that is, the arrangement of optical fibers, requires great skill as the optical fibers are extremely thin, and there is a high risk of cutting them, so this method (3) of image guidance is advantageous. This method has the disadvantages of low efficiency and high cost. As another method, a method for producing optical fiber bundles using an acid elution method is known. That is, in this method, a core glass with a high refractive index is placed in the innermost crucible of a triple crucible, a coating glass with a low refractive index and good acid resistance is placed in the outer crucible, and the expansion coefficient and viscosity of the core glass are placed in the outermost crucible. Acid-soluble glasses similar to the core glass and the covering glass are placed respectively, the entire triple crucible is heated to an appropriate temperature, the aforementioned glasses are drawn through the bottom hole of the crucible, the core glass is covered with the covering glass, and further Triple optical fiber whose outer periphery is coated with acid-soluble glass (the diameter of this optical fiber is approximately 20 mm)
The triple optical fibers were cut into appropriate lengths (approximately 400 m), and a large number of them (for example, 10,
000 optical fibers) are placed in a regular array in a jacket tube made of acid-soluble glass, and the optical fibers are heated and fused, heated to an appropriate temperature, and drawn until the diameter of the optical fibers is approximately 1/15 (4 ) Then, both ends of the hard optical fiber bundle thus obtained are coated with an acid-resistant coating, and then the entire optical fiber bundle is coated with an acid (for example, nitric acid).
A method for producing a flexible optical fiber bundle is known, which comprises eluting acid-soluble glass from the intermediate portion of the optical fiber bundle by contacting with the optical fiber bundle.

Compared to the above-mentioned method, this method allows optical fibers to be arranged with a thickness of approximately 200 μm, making the arrangement easier and with very little risk of breakage. Moreover, after the arrangement, the above-mentioned fear is completely eliminated because they are integrated by heat fusion. Therefore, according to this method, the manufacturing yield is higher than that of the above-mentioned method, and the cost can be significantly reduced. However, this method requires a jacket tube made of acid-soluble glass with an inner diameter of 20 mm in order to regularly arrange a large number of triple optical fibers. Unlike ordinary soda-lime glass, this acid-soluble glass has very poor processability.
Therefore, the variation in the inner diameter dimension over the length of the outer tube is very large. If such a jacket tube is used, the alignment of each optical fiber will be very poor, and the image transmission characteristics will be significantly degraded. In order to avoid the above-mentioned drawbacks, a large number of triple optical fibers are regularly arranged in an acid-soluble glass jacket tube, and the acid-soluble glass jacket tube with the triple fibers arranged inside is further increased in diameter. The end of the trailing outer glass mantle tube placed in the long outermost glass mantle tube is connected to an exhaust means to evacuate the inside of the outermost glass mantle tube and heat it to melt the triple optical fibers inside. Method of removing the outermost glass jacket tube after dressing
42737) has been proposed. In this method, since the outermost glass jacket tube can be made of ordinary soda lime glass, sufficient dimensional accuracy can be obtained, and the arrangement of the optical fibers will not be deteriorated.

However, the outermost glass jacket tube must be removed by mechanical polishing or the like, which requires a considerable number of man-hours.

The purpose of the present invention is to eliminate the use of the jacket tube, which is problematic as described above, and to improve dimensional accuracy by fixing at least a part of the acid-soluble glass powder or acid-soluble glass fibers with an adhesive that can be removed by heating. The present invention provides a method for efficiently manufacturing a flexible optical fiber bundle by molding a large mantle tube and using this mantle tube.

That is, the present invention has a core glass with a high refractive index coated with a glass having a low refractive index and acid resistance, and a large number of triple optical fibers in which the outer periphery is further coated with an acid-soluble glass in an acid-soluble glass jacket tube. This is arranged in a regular manner, heated, and stretched to make a hard optical fiber bundle, which is then treated with acid to dissolve the acid-soluble glass jacket tube and the acid-soluble glass coating to create a flexible optical fiber bundle. In the manufacturing step, a mantle tube formed by fixing at least a part of acid-soluble glass powder or acid-soluble glass fiber with an adhesive that can be removed by heating is used as the acid-soluble glass mantle tube (7). ) The present invention relates to a method for manufacturing an optical fiber bundle having flexibility.

The present invention will be explained in detail below with reference to the drawings. First, in a triple crucible as shown in FIG. Acid-soluble glass 7 is charged into each.

The core glass that can be used in the present invention has, for example, the following composition and properties.

Weight composition of core glass (To) 5tos = 45.0
q6, K, O = 11.0%, PbO-24.0%,
Ba0=12.0%, Zn0=5.0%, At
*0n-3.0%, ASt On =0.7%, refractive index (nd l = 1.59062, dislocation point = 528t:
', Softening point=583C1 Coefficient of thermal expansion-99,0×1O-
7crn/, C0 The coated glass that can be used in the present invention has, for example, the following composition and properties.

(8) -- Weight composition of coated glass (%) SL, 2 = 64.0%
, Na20=16.0%, Pb0=12.0
'Xi, Zn0 = 5.0 excellent, A120a = 3.0
q6, ASz On -0-7%, refractive index (nd) = 1
-52852, dislocation point -4860, softening point 533C1 coefficient of thermal expansion = 98-0 x l0-7 crn/cm C.

Further, the acid-soluble glass that can be used in the present invention has, for example, the following composition and properties.

Weight composition (%) of acid-soluble glass sto, -19,
5%, IlhOs = 36-5'16, Na20
=11.0%, Ba0=26.0%, Zn0=
7-0%, AS208=0-3%, refractive index (nd)
-1,58090, dislocation point=540C1 softening point=57
4U, thermal expansion coefficient -92, Ox 10' cm/1-
rn C0 Then, a triple crucible containing the core glass, coating glass, and acid-soluble glass is heated in an electric furnace 11, and the triple optical fiber 1 is pulled by a roller 12. FIG. 1 shows a diametrical cross-sectional view of the triple optical fiber 1. The outer diameter of the 1-0 triple optical fiber 1 is approximately 200μ, the thickness of the acid-soluble glass 4 is approximately 5μ,
The thickness of the coated glass 3 is approximately 20μ. This triple optical fiber 1 is cut into a length of about 400+m. Next, about 60 parts of the acid-soluble glass powder and about 40 parts of an adhesive that can be removed by heating are mixed to prepare a slip, and the slip is molded by casting, press molding, or extrusion molding as shown in FIG. A circular or polygonal hollow acid-soluble glass jacket tube as shown in FIG. 23a, FIG. 4, FIG. 4, 23b, and FIG. 5, 23c is made. When using fibers instead of powder, as shown in FIG. 8, fibers 31 are tightly inserted into a mold 30, and adhesive 32, which can be removed by heating, is injected into the gaps between the fibers. A hollow circular or polygonal acid-soluble glass jacket tube is made. Adhesives that can be removed by heating include nitrocellulose, acetylcellulose, ethylcellulose, polyvinyl butyral, polyvinyl acetate, and the like, and in this example, the following composition was used.

Blending composition: Ethyl cellulose: approx. 5%, plasticizer: small amount,
Acetone: Approximately 85 units.

40 ethyl cellosolve per 100 parts of the above blended composition
~50 parts of the solution was used as an adhesive. Next, the step of inserting the triple optical fibers 1 cut to a certain length into the acid-soluble glass jacket tube 23a so as to be regularly arranged is shown in FIG. 4 as an embodiment of the lath jacket tube 23b.

FIG. 5 shows an embodiment of a hexagonal acid-soluble glass jacket tube 23c.

(11) The acid-soluble glass jacket tube 23b, which can be divided, is much easier and more efficient when arranging the triple optical fibers 1 regularly than the acid-soluble glass jacket tube 23a, which cannot be divided.

Almost the same effect can be obtained by adding a small amount of refractory to acid-soluble glass powder or acid-soluble glass fiber. Alternatively, glass fibers coated with a relatively thick acid-soluble glass may be used. Further, when triple optical fibers are arranged using a polygonal, for example, hexagonal acid-soluble glass jacket tube, close packing can be achieved relatively easily.

Next, an acid-soluble glass jacket tube into which triple optical fibers 1 are regularly arranged is heat-fused, and then,
As shown in FIG. 6, the triple optical fiber 1 fused together with the acid-soluble glass jacket tube 23 is further heated and stretched. In this case, the acid-soluble glass jacket tube 23 into which the triple optical fibers 1 are regularly arranged may be directly applied to the apparatus shown in FIG. 6 to perform heating (12) and hot stretching at the same time. The acid-soluble glass jacket tube 23 into which the triple optical fiber 1 has been inserted is sent downward little by little by rollers 14, and its tip is heated in an electric furnace 16 for about 70 minutes.
000 to soften it and stretch it downward with rollers 15. In this case, the stretched optical fiber bundle 1γ is stretched to a diameter of about 1/15 of the diameter before stretching, that is, about 1.5 diameter. As a result, the diameter of each optical fiber is approximately 13μ. In the above heat fusing or heat stretching step, the atmosphere may be made vacuum to remove gas between each triple optical fiber or between the triple optical fiber and the acid-soluble glass jacket tube.

Next, the end part of the obtained hard optical fiber 1γ was glued with acid-resistant resin 20
Cover with Next, the entire optical fiber bundle with the end portions covered is immersed in the acid elution treatment liquid 19 in the acid elution treatment tank 21 to elute the acid-soluble glass in the middle portion to produce a flexible optical fiber bundle.

As mentioned above, the present invention does not use a problematic mantle tube,
Each optical fiber is characterized by the use of a jacket tube with high dimensional accuracy, which is formed by fixing at least a portion of acid-soluble glass powder or acid-soluble glass fibers with an adhesive that can be removed by heating. It is possible to efficiently produce an optical fiber bundle having very good alignment and flexibility with excellent image transmission properties.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a triple optical fiber. FIG. 2 is a schematic diagram of the process of heating a triple crucible to produce triple optical fibers. Figures 3(a) and 3(b) are a front view and a side view showing the triple optical fiber inserted into the acid-soluble glass jacket tube. FIGS. 4(a) and 4(b) are a front view and a side view of a two-part acid-soluble glass mantle. Figures 5 (&) and (b) are a front view and a side view of a hexagonal acid-soluble glass jacket tube. FIG. 6 is a schematic diagram of the process of heating and stretching an acid-soluble glass jacket tube into which triple optical fibers are inserted. FIG. 7 is a schematic diagram of the process of acid elution treatment. FIG. 8 is an explanatory diagram showing a method for manufacturing a mantle tube formed by fixing at least a portion of acid-soluble glass fibers with an adhesive that can be removed by heating. 1...Triple optical fiber 2.5...Core glass 3.6...Coating glass 4, γ...Acid-soluble glass 8.9.10 ...... Crucible 11.16 ... Electric furnace 12.14.15 ... Roller 17 ...
- Optical fiber bundles 23.23a, 23b, 23c... Acid-soluble glass jacket tubes 24a, 24b... Fitting portion 21... Acid elution treatment tank 19...・Acid elution treatment liquid 20...Acid-resistant resin 30...
... Mold 31 ... Acid-soluble glass fiber 32
...Adhesive Applicant Fuji Photo Koki Co., Ltd. (15) ((1) (49 Figure 3 (ku) (Clothing) 4th Closing 5th Flash Figure 6

Claims (2)

[Claims] (1) A core glass made of high refractive index glass is coated with a glass having low refractive index and acid resistance,
A large number of triple optical fibers, the outer periphery of which is further coated with acid-soluble glass, are regularly arranged in an acid-soluble glass jacket tube,
In the process of heating and stretching this to make a hard optical fiber bundle, and then treating it with acid to elute the acid-soluble glass jacket tube and the acid-soluble glass coating to produce a flexible optical fiber bundle, A flexible optical system characterized in that the acid-soluble glass jacket tube is a jacket tube formed by fixing at least a portion of acid-soluble glass powder or acid-soluble glass fiber with an adhesive that can be removed by heating. Method for producing fiber bundles. (2) A method for manufacturing a flexible optical fiber bundle according to claim 1, which comprises dividing the acid-soluble glass jacket tube according to claim 1 into at least two parts in the length direction. .