JPH0588027A - Light guide terminal part and its formation - Google Patents

Abstract

PURPOSE:To increase the heat resistance of a light guide terminal part to the heat resistance that an optical fiber itself has. CONSTITUTION:Many optical glass fibers 3 used for a light guide are bundled together at their peripheral edge by using an annular glass layer 2 which has nearly the same softening point with their clads 5. The annular glass layer 2 and the clads 5 of the respective optical fibers 3 are connected by fusion splicing. A glass pipe is usable as this annular glass layer or may be formed on the peripheral surface of a ferrule pipe 1. A glass pipe fitted in the ferrule pipe is, of course, usable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a terminal portion of a light guide mainly composed of a large number of bundled optical fibers.

[0002]

2. Description of the Related Art A light guide consisting of a large number of optical fibers is used by bundling its end portions. As shown in FIG. 4, the most common conventional terminal forming technique is to use a metal short tube 111 having a predetermined inner diameter as a base into which a large number of optical fibers 113 are inserted and to which an organic adhesive 116 is applied. It is fixed with. The optical fiber used for this light guide made of glass originally has heat resistance of about 500 to 600 ° C., and since the mouthpiece is also made of metal, it can sufficiently withstand higher temperatures. However, the heat-resistant temperature of the organic adhesive used in the actual light guide is around 200 ° C, and a survey of other usable organic adhesives with higher heat-resistant temperature showed that the polyimide-based adhesive The best one has a heat resistance of about 350 ° C., and there is no one that can maximize the heat resistance of the glass optical fiber itself. Further, since the adhesive 116 has entered between the optical fibers 113, the optical fiber 1
The filling factor of No. 13 is not sufficiently increased.

Further, in Japanese Patent Laid-Open No. 57-97504, the clad at the end of the optical fibers to be bundled is removed and the end of the optical fiber which is only the core is inserted into a glass tube. There is disclosed a technique in which a core and a glass tube are integrated by heating and fusing. In this technology, a means of heat fusion is used to integrate the core and the glass tube, but the original purpose is to strengthen the light guide terminal part rather than to make it heat resistant. There is. That is, by making the structure of the light guide terminal portion itself to be one optical fiber, it is intended to realize higher strength than that of a large number of bundled optical fibers. The end portion of the light guide formed as a result is integrated into one large-diameter optical fiber, and a large number of optical fibers are not bundled in a large number. Further, in this publication, it is described that in the formed light guide end portion, there is no gap between the cores and between the integrated core and the glass, but in reality, there is not much space. It must be heated evenly, and an escape route must be secured before the heating so that the air in the air gaps between the cores can escape from the air gaps, and the air must be heated under the condition that this air completely escapes. .. For that purpose, it is considered that some heating conditions effective for venting air, such as heating in vacuum, are actually required. Otherwise 1
There is a risk that some air bubbles will remain inside the embossed core or between the core and the glass tube, resulting in a defective product. It is also described in this publication that resin or the like is filled between the tapered portion of the glass tube and the portion of the optical fiber where the clad remains to be integrated. Therefore, it must be said that this portion filled with the resin also has low heat resistance.

Further, in Japanese Patent Laid-Open No. 1-114804, the end portion of the fiber bundle is dipped in a low melting point glass melt, and excess glass melted out of the glass melt spread between the optical fibers is sleeved. A technique is disclosed in which the end portion of the fiber bundle is converged and formed by squeezing with a jig. Since this technique uses low-melting glass without using an organic resin adhesive, it has better heat resistance than adhesives, but the melting point of low-melting glass itself is lower than that of optical fibers. Therefore, the heat resistance of the optical fiber cannot be maximized. Further, the technique of squeezing out excess molten glass using a sleeve-shaped jig is difficult to apply to manufacture of a coaxial light guide. A coaxial light guide is a light guide with a structure in which the bundle of optical fibers at the center and the bundle of optical fibers around it are separated by an annular partition wall provided between them, and arranged coaxially. is there. In the structure with such a partition wall, the molten glass filled in the bundle of optical fibers at the center and the molten glass filled in the bundle of surrounding optical fibers are squeezed by a sleeve jig, and these are coaxial. It is almost impossible to place it on top.

The present invention has been devised in view of the above-mentioned conventional technical problems to effectively solve them.
Therefore, it is an object of the present invention to provide a light guide terminal portion in which the heat resistance is increased to the heat resistance of the optical fiber and the filling rate of the optical fiber is increased as high as possible, and a method for forming the same.

Another object of the present invention is a method for forming a light guide terminal portion in which a large number of optical fibers are bundled in a state of a large number, and there is no possibility that air bubbles will be generated in the individual optical fibers. Provided is a method for forming a light guide terminal portion and a light guide terminal portion formed by the method, in which the heat resistance of the light guide terminal portion is increased to the heat resistance of the optical fiber and the filling rate of the optical fiber is also increased. To do.

Still another object of the present invention is to provide a method suitable for forming an end portion of a coaxial type light guide, and a heat resistance of the end portion of the light guide manufactured by the method to the heat resistance of the optical fiber. Another object of the present invention is to provide a terminal portion of a coaxial type light guide which has a high filling rate of optical fiber.

[0008]

The light guide terminal section according to the present invention has the following structure in order to solve the problems of the prior art as described above and to achieve the object. That is, the light guide terminal portion of the present invention includes a large number of glass optical fibers and an annular glass layer of glass that surrounds the periphery of the bundle of the plurality of optical fibers and has a softening point approximately equal to the cladding of the optical fibers. And the mutual contact portions of the clads of the plurality of optical fibers and the mutual contact portions of the annular glass layer and the clads of the optical fibers are fused. Further, it may be configured with a base, or may be a terminal portion of a coaxial light guide. The end portion of the coaxial light guide may have no base or may have a base. Further, the above-mentioned base is not limited to a metal one,
Ceramics are also included. The annular glass layer may be formed on the peripheral surface of the die, or may be composed of a glass tube which itself has an annular shape.

In the method of forming a light guide terminal portion of the present invention, a first step of filling a large number of optical fibers into a glass tube having a softening point substantially equal to the cladding of the optical fibers, and the first step. After the second step of heating the glass tube and the optical fiber at a temperature equal to or higher than the softening point until the claddings of the optical fiber and the cladding and the glass tube are fused, and after the second step, And a third step of gradually cooling the heated glass tube and the optical fiber. The light guide in this case may be a coaxial type.

Further, in a method of forming a terminal portion of a light guide having a base (including not only metal but also ceramics), a large number of optical fibers are provided with a softening point almost equal to that of the cladding of the optical fibers. A first step of filling the inside of the glass tube, and after the first step, the glass tube and the optical fiber are fused with each other and the clads of the optical fiber and the clad and the glass tube are fused at a temperature equal to or higher than the softening point. A second step of heating to, a third step of gradually heating the heated glass tube and the optical fiber after the second step, and at least prior to the second step, A fourth step of fitting into a mouthpiece tube having an inner diameter tapered, and heating in the second step involves heating the glass tube and the optical fiber as they soften. As lowered into the small diameter side of the mouthpiece tube by gravity Te, the glass tube is performed in a state where the optical fiber and ferrule tube standing vertically.

Further, the method of forming the end portion of the coaxial light guide having the base (including not only metal but also ceramic) has a softening point almost equal to that of the glass optical fiber clad filled therein. A first glass tube and a second glass tube which are coaxially arranged with each other;
A first step of filling a large number of the optical fibers in the glass tube and between the second glass tube and the first glass tube; and, after the first step, the first and second glass tubes and A second step of heating the optical fiber at a temperature equal to or higher than the softening point until the claddings of the optical fiber and the cladding and the first and second glass tubes are fused, and the heating after the second step. The third step of gradually cooling the first and second glass tubes and the optical fiber, and at least the second step are performed in advance, and the inner diameters of the first and second glass tubes are tapered. A fourth step of fitting into the mouthpiece tube, and heating in the second step is performed so that the first and second glass tubes and the optical fiber are lowered to the smaller diameter side of the mouthpiece tube by their own weight as the first and second glass tubes and the optical fiber are softened. , The first, 2 glass tube is performed in a state where the optical fiber and ferrule tube standing vertically.

The method of forming the end portion of the light guide without using the glass tube is the first method of applying a paste of glass powder having a softening point substantially equal to that of the clad of the glass optical fiber to the inner peripheral surface of the die tube. A step of heating the die tube coated with the paste of the glass powder to evaporate the solvent in the paste and bring it into close contact with the inner peripheral surface of the die tube to form a solidified layer of the glass powder; Steps,
In the die tube in which the solidified layer of the glass powder is formed,
A third step of filling a large number of glass optical fibers,
After the third step, the glass powder and the optical fiber are heated at a temperature equal to or higher than the softening point to melt the glass powder to form an annular glass layer for bonding, and the clads of the optical fibers and the clad are The method includes a fourth step of fusing the bonding annular glass layer and a fifth step of gradually cooling the bonding annular glass layer and the optical fiber after the fourth step.

Further, in the method of forming the end portion of the coaxial light guide without using the glass tube, the first and second die tubes having different diameters are prepared, and the inner peripheral surface of the first die tube having a small diameter and The first step of applying a paste of glass powder having a softening point substantially equal to that of the clad of the glass optical fiber to the outer peripheral surface and the inner peripheral surface of the second diameter cap tube; The glass powder is produced by heating the first and second die pipes to vaporize the solvent in the paste and making them adhere to the inner and outer peripheral surfaces of the first die pipe and the inner peripheral surface of the second die pipe. Second step of forming a solidified layer of, and after the second step, the first and second mouthpiece tubes are arranged coaxially, and the inside of the first mouthpiece tube and the first mouthpiece tube and the second mouthpiece Third, filling a large number of the above-mentioned optical fibers with a gold tube
After the step and the third step, the glass powder and the optical fiber are heated at a temperature equal to or higher than the softening point to melt the glass powder to form an annular glass layer for bonding, and clads between the optical fibers and The method includes a fourth step of fusing the clad and the bonding annular glass layer, and a fifth step of gradually cooling the bonding annular glass layer and the optical fiber after the fourth step.

[0014]

In the light guide terminal portion according to the present invention, since the cladding of the optical fiber and the annular glass layer have approximately equal softening points, heating the optical fiber above the softening point causes the optical fiber The clads and the clad and the annular glass layer are fused to each other. Since an adhesive such as a resin material does not enter between these, the filling rate can be maximized, and the heat resistance of the light guide terminal portion can be improved to be approximately equal to the heat resistance of the clad. Moreover, no bubbles are generated in the core of each optical fiber, and the heating conditions are much milder than in the case of removing the cladding and heating and fusing the core.

Metals generally have higher heat resistance than glass, and when a glass tube is used as the annular glass layer, the light guide terminal portion can be formed even with the metal die attached. If formed with a metal die with a taper on the inner diameter, heating these in an upright state causes the softened clad and glass tube to descend to the smaller diameter side of the die by its own weight. Familiarity is also very good.

In particular, by making the glass tubes the first glass tube and the second glass tube in the double coaxial arrangement, the filling rate is maximized and the heat resistance is approximately equal to the heat resistance of the clad. The end portion of the coaxial light guide can be easily formed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A light guide terminal portion and a method of forming the same according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a partially enlarged view of a terminal portion of a light guide having a simple arrangement using a multi-component glass optical fiber. In this embodiment, the cap tube 1 is provided at the outermost peripheral portion and is made of stainless steel (SUS 430F). Mouthpiece 1
The inner peripheral surface of is tapered as shown in FIG.
A low melting point bonding glass tube 2 is fitted on the inner peripheral side of the base tube 1. Inside the glass tube 2 is a multi-component glass optical fiber 3
Is packed with a high filling rate. The thermal expansion coefficient of the base pipe 1 is 108 × 10 ⁻⁷ . The softening point of the glass tube 2 is 595.
C., thermal expansion coefficient is 94.5 × 10 ⁻⁷ , and refractive index is 1.52. Regarding the optical fiber 3, the softening point of the core 4 is 688 ° C., the coefficient of thermal expansion is 85 × 10 ⁻⁷ , and the refractive index is 1.
57. Similarly, the softening point of the clad 5 is 615 ° C., the coefficient of thermal expansion is 90.2 × 10 ⁻⁷ , and the refractive index is 1.52. The end portion of the light guide of this embodiment can endure at least up to 523 ° C., which is the yield point of the glass tube 2.

Since no organic adhesive such as resin is interposed between the respective optical fibers 3, the individual optical fibers 3 are filled with the glass tube 2 at such a high filling rate that the clads 5 contact each other. It is packed inside. Specifically, inner diameter 2.1m
Approximately 1440 optical fibers with a diameter of 50 μm and approximately 225 optical fibers with a diameter of 40 μm for an m glass tube
For glass tubes with an inner diameter of 3.5 mm, packed with 0, about 4000 optical fibers with a diameter of 50 μm, 4
An optical fiber of 0 μm is packed with about 6250. The clads 5 are fused to each other at their contact points, and the heat resistance of the clad 5 itself is exhibited as it is.
Further, the glass tube 2 and the optical fiber 3 in contact with the inner peripheral surface thereof
The clad 5 is also fused at the contact point. It should be noted that the filling rate of the optical fiber is much higher in this embodiment than in FIG. 4 showing the conventional technique.

The process of forming the light guide terminal portion of this embodiment is performed by the following steps. 1) The glass optical fiber 3 is packed in the bonded glass tube 2. 2) Insert the glass tube 2 into the base tube 1. The end of the base tube 1 on which the inner peripheral surface is tapered is defined as the tip side of the optical fiber 3. 3) Insert the assembled optical fiber 3, glass tube 2 and base tube 1 into a ring-shaped ring heater,
Heat to 620 ° C. For this insertion, the inner peripheral surface of the mouthpiece 1 should be tapered downward and the mouthpiece 1
It is stopped at the position where it heats up from around. 4) Continue heating at 620 ° C. for about 5 minutes, and wait for the softened glass tube 2 to melt from the tapered end of the die tube 1. By tapering the inner peripheral surface of the base tube 1, a tight contact state of the glass tube 2 with the base tube 1 is formed. Between the optical fibers 3 and between the optical fibers 3 and the glass tube 2, a space may remain at their non-contact portions, but no bubbles are formed inside each optical fiber 3. 5) When the glass tube 2 begins to melt, the heating temperature of the heater is lowered and the ambient temperature is gradually lowered to gradually cool to the transition point. This slow cooling is performed at a rate of about 5 ° C. per minute.
By this slow cooling, the composition of the core 4 and the clad 5 of the optical fiber 3 is not changed, and the desired optical performance is maintained.

Although the multi-component glass optical fiber is used in the above-mentioned embodiment, if the silica type optical fiber is used, a high heat resistant light guide is used in combination with a cemented glass tube having a softening point which is approximately close to the softening point of the cladding. It is also possible to form the terminal part of the. In this case, a die tube made of machinable ceramic is suitable, and the heating temperature is further increased.

Further, although the multi-component optical fibers are simply arranged in the above-mentioned embodiment, the end portion of the coaxial type light guide in which the glass tubes are coaxially and doubly arranged as shown in FIG. It can be formed extremely easily according to the forming process. In FIG. 3, 11 is a base tube, 12 ₁ is an inner bonded glass tube, 12 ₂ is an outer bonded glass tube, and 13 is a multi-component optical fiber. The clads 15 of the optical fibers 13 are fused to each other at their contact points.
The heat resistance of itself is exhibited as it is. Further, the clad 15 of the optical fiber 13 which is in contact with the inner peripheral surface and the outer peripheral surface of both the glass tubes 12 ₁ and 12 ₂ is also fused at the contact points.

The formation process is performed by the following steps. 1) Inside glass tube 12 ₁ in which glass optical fiber 13 is coaxially double-positioned and inside glass tube 12 ₁ and outside glass tube 1
Fill between 2 ₂ . 2) Insert the assembled glass tubes 12 ₁ and 12 ₂ and the optical fiber 13 into the base tube 11. The end of the base tube 11 on which the inner peripheral surface is tapered is defined as the tip side of the optical fiber 13. 3) Insert the assembled optical fiber 13, glass tubes 12 ₁ and 12 ₂ and cap tube 11 into a ring heater formed in an annular shape, and heat to 620 ° C. This insertion is stopped at a position where the inner peripheral surface of the mouthpiece pipe 11 is tapered downward and the heating is performed from the periphery of the mouthpiece pipe 11. 4) Continue heating at 620 ° C. for about 5 minutes, and wait for the softened glass tubes 12 ₁ and 12 ₂ to melt from the tapered end of the die tube 11. By tapering the inner peripheral surface of the base pipe 11, a tight contact state of the glass pipe 12 _{2 with} the base pipe 11 is formed. Bubbles are formed inside each optical fiber 13 although there is a space between the optical fibers 13 and between the optical fiber 13 and both glass tubes 12 ₁ and 12 ₂ at their non-contact portions. There is no such thing. 5) When the glass tubes 12 ₁ and 12 ₂ have melted, the heating temperature of the heater is lowered, and the ambient temperature is gradually lowered to gradually cool to the transition point. This slow cooling is performed at a rate of about 5 ° C. per minute. By this slow cooling, the core 14 of the optical fiber 13 is
The composition of the clad 15 maintains the desired optical performance without modification.

Although the multi-component glass optical fiber is used also in the above-mentioned embodiment, it is of course possible to use the silica optical fiber also in the case of this coaxial type light guide. Further, in each of the above-described embodiments, only the structure having the mouthpiece pipe has been described, but a structure in which only the mouthpiece pipe is removed in these structures may be used, and the terminal portion of the formed light guide may be formed as necessary. You may install the base tube later. In that case,
The step of inserting the glass tube into the die tube in each of the above forming processes is eliminated. In order to prevent the optical fiber from slipping out of the glass tube during heating, bundle the optical fiber with a thread or other material on the upper side of the glass tube before heating or at a position away from the glass tube so as not to be affected by the heat of the ring heater. It is good to tie with a metal wire.

Next, an embodiment in which a glass tube is not used will be described with reference to FIGS. First, in the embodiment shown in FIG. 5, as an alternative structure to the glass tube, an annular glass layer 22 attached to the wall surface of the die tube 21 is formed. The annular glass layer 22 is obtained by dissolving a glass powder having a softening point substantially equal to that of the clad glass in a solvent such as glycerin which has a relatively high viscosity and is easily vaporized, and while pouring it into the die pipe 21, it is uniformly applied to the wall surface. Further, it is formed by being fused with the wall surface while further heating with the die tube 21 to vaporize the solvent. The formed annular glass layer 22 is made of the same material as the glass tube of the above embodiment. Since the annular glass layer 22 is sufficiently adhered to the base pipe 21 by this fusion, it is not necessary to taper the inner peripheral surface like the base pipe of the above embodiment.

The multi-component glass optical fiber 23 is packed in the glass layer-attached base tube 21 formed as described above at a high filling rate, and heating and gradual cooling similar to those in the above-mentioned embodiment is performed to end the light guide. Parts are formed. Needless to say, a quartz optical fiber can be used. Note that the glass tube-equipped base tube 21 plays a role of holding the optical fibers in a bundled state, which is achieved by the glass tube in the above-described embodiment in this process.

The process of forming the light guide terminal portion of the embodiment in the case of forming the annular glass layer by fusion will be specifically described below. 1) Glass powder of the same quality as the glass tube used in the above example was melted into a paste with a small amount of glycerin, and this was melted into a base tube 2
While pouring into 1, apply evenly to the inner peripheral surface. 2) The die tube 21 is heated to 180 ° C to 200 ° C to vaporize glycerin and obtain a uniform glass powder layer on the inner peripheral surface. 3) The base tube 21 is temporarily heated to 620 ° C. to melt the glass powder, and the glass powder layer is bonded to the annular glass layer 22 for bonding.
To 4) The glass optical fiber 23 is packed in the base 21. 5) Insert the assembled optical fiber 23 and base tube 21 into a ring-shaped ring heater, and set at 620 ° C.
Heat up to. 6) Continue heating at 620 ° C. for about 5 minutes to fuse the optical fibers 23 and the optical fibers 23 to the annular glass layer 22. 7) After fusing, the temperature of the heater is lowered, and the ambient temperature is gradually lowered to gradually cool to the transition point.

Further, as shown in FIG. 6, the double base pipe 3
11 ₁ and 31 ₂ are used to form the bonding annular glass layers 32 ₁ and 32 ₂ on the inner peripheral surface and the outer peripheral surface of the inner peripheral side cap tube 31 _{1 and} the inner peripheral surface of the outer peripheral side cap tube 31 _2. Further, by forming the annular glass layer 32 ₃ for bonding, it is possible to create a coaxial light guide.

[Brief description of drawings]

FIG. 1 is a partially enlarged view showing an embodiment of a light guide terminal portion of a simple arrangement using a multi-component glass optical fiber according to the present invention.

FIG. 2 is a vertical sectional view of a cap tube used in the light guide terminal portion shown in FIG.

FIG. 3 is a partially enlarged view showing an embodiment of a light guide terminal portion in which glass optical fibers are coaxially arranged.

FIG. 4 is a partially enlarged view showing a light guide terminal unit having a simple arrangement according to a conventional technique.

FIG. 5 is a partially enlarged view showing another embodiment of a light guide terminal portion of a simple arrangement using a multi-component glass optical fiber according to the present invention.

FIG. 6 is a partially enlarged view showing another embodiment of a light guide terminal portion in which glass optical fibers are coaxially arranged.

[Explanation of symbols]

₁ , 11, 21, 31 ₁ , 31 ₂ Base tube 2, 12 ₁ , 12 ₂ , 22, 32 ₁ , 32 ₂ , 32 ₃ Annular glass layer ₃ , ₁₃ , 23, 33 Optical fiber 4, 14, 24, 34 Core 5,15,25,35 Clad

Claims (10)

[Claims] 1. A large number of glass optical fibers (3,13,23,33)
And a plurality of optical fibers (3,13,23,33) around the periphery of the bundle of the optical fiber (3,13,23,33) clad (5,15,2
5,35) and an annular glass layer of glass having a softening point substantially equal to (2,12 ₁ , 12 ₂ , 22, 32 ₁ , ₁ , 32 ₂ , 32 ₃ ) and a large number of the optical fibers (3, 13 , 23,33) clad (5,15,
25,35) and the annular glass layer (2,1)
2 ₁ , 12 ₂ , 22,32 ₁ , 32 ₂ , 32 ₃ ) and the above optical fiber (3,13,23,33)
The end portion of the light guide characterized in that the mutual contact portions with the clads (5, 15, 25, 35) are fused together. 2. A large number of glass optical fibers (3,13,23,33)
And a plurality of optical fibers (3,13,23,33) around the periphery of the bundle of the optical fiber (3,13,23,33) clad (5,15,2
5,35) annular glass layer of glass having a softening point approximately equal to (2,12 ₁ , 12 ₂ , 22,32 ₁ , ₁ , 32 ₂ , 32 ₃ ) and the annular glass layer (2, 12 ₁ , 12 ₂ , 22,32 ₁ , 32 ₂ , 32 ₃ ) with a cap tube (1,11,21,31 ₁ , 31 ₂ ), which holds the above-mentioned multiple optical fibers (3,13,23,33). Clad (5,15,
25, 35) mutual contact portion, the annular glass layer (2, 12 ₁ , 12 ₂ , 2
2,32 ₁ , 32 ₂ , 32 ₃ ) and the optical fiber (3,13,23,33) clad (5,15,25,35) mutual contact portion, and the annular glass layer (2,12) ₁ , 12 ₂ , 22,32 ₁ , 32 ₂ , 32 ₃ ) and the above cap pipe (1,11,2
1,31 _1, 31 light guide terminal _{unit 2)} and the mutual contact portions of the is characterized in that it is fused, respectively. Wherein said annular glass layer (2, 12 _1, 12 ₂₎ is a light guide end portion according to claim 1 or 2, wherein composed of glass tubes. 4. The annular glass layer comprises a first glass tube (1
From 2 _1), the first glass tube (12 ₁₎ and second glass tubes arranged coaxially and having an inner diameter larger than the outer diameter of the first glass tube (12 ₁₎ and (12 ₂₎ becomes, the large number of glass optical fibers (13), the first glass tube (12 ₁₎ within and, filled between the first glass tube (12 ₁₎ and the second glass tube (12 ₂₎ The light guide terminal part according to claim 1 or 2. 5. The first cap pipe (3) on the inner peripheral side is the cap pipe.
1 ₁ ) and a second mouthpiece pipe (31 ₂ ) which is separated from the first mouthpiece pipe (31 ₁ ) to the outer peripheral side and is arranged coaxially with the first mouthpiece pipe (31 ₁ ). glass layer, said first mouthpiece tube (31 ₁₎ first annular glass layer formed on the inner peripheral surface on the (32 _1), said first mouthpiece tube
The second annular glass layer (32 ₂ ) formed on the outer peripheral surface of (31 ₁ ) and the third annular glass layer (32 ₂ ) formed on the inner peripheral surface of the second cap tube (31 ₂ ).
Annular glass layer (32 _3), consists, the large number of glass optical fibers (33), said first annular glass layer (32 ₁₎ and in said second annular glass layer (32 ₂₎ the first 3. A space between the three annular glass layers (32 ₃ )
The described light guide terminal. 6. A glass tube (2, 12 ₁ , 12 ₂ ) having a large number of glass optical fibers (3, 13) and a softening point substantially equal to the cladding (5, 15) of the optical fibers (3, 13). ), And after the first step, the glass tube (2, 12 ₁ , 12 ₂ ) and the optical fiber (3, 13) are filled with the optical fiber (3, 13) at a temperature equal to or higher than the softening point. 3,13) clads (5,15) and their clads
The second step of heating until the (5,15) and the glass tube (2,12 ₁ , 12 ₂ ) are fused, and after the second step, the heated glass tube (2,1)
2 ₁ , 12 ₂ ) and a third step of gradually cooling the optical fiber (3, 13). 7. A glass tube (2, 12 ₁ , 12 ₂ ) having a large number of glass optical fibers (3, 13) and a softening point substantially equal to the cladding (5, 15) of the optical fibers (3, 13). ), And after the first step, the glass tube (2, 12 ₁ , 12 ₂ ) and the optical fiber (3, 13) are filled with the optical fiber (3, 13) at a temperature equal to or higher than the softening point. 3,13) clads (5,15) and their clads
The second step of heating until the (5,15) and the glass tube (2,12 ₁ , 12 ₂ ) are fused, and after the second step, the heated glass tube (2,1)
2 _1, 12 ₂₎ and a third step of annealing and optical fiber (3, 13), carried out prior to at least the second step, the glass tube (2, 12 _1, 12 _2), the inner diameter Has a fourth step of fitting into the tapered pipe tube (1,11), and heating in the second step is performed by the glass tube (2,1).
2 _1, 12 ₂₎ and the optical fiber (3, 13) is by its own weight with the softened to fall into the small-diameter side of the mouthpiece tube (1, 11), the glass tube (2, 12 _1, 12 ₂₎ , Optical fiber (3,13) and base tube (1,
11) A method for forming a light guide terminal portion, which is performed in a state in which the step (11) is set upright. 8. A glass optical fiber (13) filled inside.
Using cladding (15) and the first and second glass tubes arranged coaxially with respect to each other have substantially equal softening point (12 _1, 12 _2), said first glass tube (12 ₁₎ in and , The second glass tube
A first step of filling a large number of the optical fibers (13) between the (12 ₂ ) and the first glass tube (12 ₁ ); and, after the first step, the first and second glass Tube (1
2 ₁ , 12 ₂ ) and the optical fiber (13) at a temperature equal to or higher than the softening point, between the claddings (15) of the optical fiber (13) and between the cladding (15) and the first and second glass tubes (12 ₁ , 12 ₂ ), and the heated first and second glass tubes (12 ₁ , 12 ₂ ) and the optical fiber (13) are gradually heated after the second step. Third to cool
Step 4 and at least preceding the second step, and a fourth step of fitting the first and second glass tubes (12 ₁ , 12 ₂ ) into the mouthpiece tube (11) having a tapered inner diameter. The heating in the second step is performed by heating the first and second glass tubes (12 ₁ , 12 ₂ ) and the optical fiber (13) due to their own weight as the softening of the first and second glass tubes (12 ₁ , 12 ₂ ). Formation of a light guide terminal portion which is performed with the first and second glass tubes (12 ₁ , 12 ₂ ), the optical fiber (13) and the base tube (11) standing vertically so as to descend to the side. Method. 9. The cladding (2) of the glass optical fiber (23, 33)
5,35), a first step of applying a paste of glass powder having a softening point approximately equal to that of the inner surface of the die pipe (21,31 ₁ , 31 ₂ ), and the die pipe coated with the paste of the glass powder (21,31
₍₁ , 31 ₂ ) is heated to vaporize the solvent in the paste, and is adhered to the inner peripheral surface of the die tube (21,31 ₁ , 31 ₂ ) to form a solidified layer of the glass powder. Step, and the spinneret (21,31) on which the solidified layer of the glass powder is formed
The third step of filling a large number of glass optical fibers (23, 33) in ₁ , 31 ₂ ) and the glass powder and the optical fibers (23, 33) after the third step Heating at the above temperature, melting the glass powder to bond the annular glass layer (22, 32 ₁ , 32 ₂ ,
32 ₃ ) and the cladding (2, 33) of the optical fiber (23, 33).
5 and 35) How to and the cladding (25, 35) and the joint annular glass layer (22, 32 _1, 32 ₂₎ and a fourth step of fusing the, after the fourth step, the cyclic for the bonding Glass layer (22,
32 ₁ , 32 ₂ ) and the fifth step of gradually cooling the optical fibers (23, 33). 10. The first and second ferrules (3) having different diameters.
1 ₁ , 31 ₂ ), and a glass optical fiber (1 ₁ , 31 ₂ ) on the inner and outer peripheral surfaces of the small-diameter first base pipe (31 ₁ ) and the large-diameter second base pipe (31 ₂ ). 33) The first step of applying a glass powder paste having a softening point approximately equal to that of the clad (35), and the first and second steps of applying the glass powder paste.
On the inner and outer peripheral surfaces of the first die pipe (31 ₁ ) and the second die pipe (31 ₂ ) by heating the die pipes (31 ₁ , 31 ₂ ) of the above to vaporize the solvent in the paste. A second step of forming a solidified layer of the glass powder by closely adhering to the peripheral surface, and after the second step, the first and second die pipes (3
1 ₁ , 31 ₂ ) are arranged coaxially, and inside the first mouthpiece pipe (31 ₁ ) and
A third step of filling a large number of the optical fibers (33) between the first base pipe (31 ₁ ) and the second base pipe (31 ₂ ), and the glass powder after the third step. And the optical fiber (33) is heated at a temperature of the softening point or higher, and the glass powder is melted to form a bonding annular glass layer (32 ₁ , 32 ₂ , 32 ₃ ), and the optical fiber (33) Cladding (35) and the cladding (35) and the annular glass layer for bonding (32 ₁ , 32 ₂ , 3
2 ₃ ) and the fourth step, and after the fourth step, the annular glass layer for bonding (3
2 ₁ , 32 ₂ , 32 ₃ ) and a fifth step of gradually cooling the optical fiber (33).