JP2001318270A - Glass capillary tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass capillary tube, capable of accurately holding an optical fiber and easily positioning the optical fiber so held with respect to other optical parts. SOLUTION: The glass capillary tube 21 is equipped with an insertion hole 22, having an inner diameter slightly larger than that of a single core optical fiber 24 and with two or more planar parts 21b, 21c on the outer surface in a manner such that the distance from the center axis 22a of the inserting hole to the planar parts is controlled within a required dimensional accuracy. Using these planar parts 21b, 21c, optical axis alignment and positioning are performed for the capillary tube, with respect to other optical parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass capillary tube into which an optical fiber is inserted, the optical axis of which is held at an accurate position, and which can be easily positioned and fixed with respect to other optical components. is there.

[0002]

2. Description of the Related Art Conventionally, when an optical fiber is connected and fixed to an optical axis of an optical component such as a lens, a light emitting element, a light receiving element, a waveguide element, and an optical fiber, the optical fiber generally has a circular cross section. A capillary tube held and fixed inside is used.

For example, an optical device such as an optical isolator using a polarization filter or an optical frequency modulator that handles an optical signal whose polarization plane is maintained by a polarization plane maintaining type optical fiber (commonly called a panda optical fiber) is used as a polarization plane. As shown in FIG. 5, when the optical signal holding the optical signal is transmitted and received through the optical fiber, first, the optical fiber 4 is inserted into the insertion hole 2 of the capillary 1.
Is inserted and fixed with an adhesive 5 such as an epoxy resin. After the optical fiber 4 protruding from the end face 1a is removed, the end face 1a is polished by a known method to produce a plug 6. The optical axis of the core 4a of the optical fiber 4 held by the plug 6 corresponding to the optical device 7 is aligned with the optical input / output unit 7 of the optical device 7.
The optical signal whose polarization plane is maintained is emitted and incident while being aligned with a.

[0004]

However, when aligning the optical axis of the optical fiber 4 held by the plug 6 with the optical input / output unit 7a of the optical device 7, the direction of the polarization plane is monitored in advance. A marker 6a indicating the polarization direction is engraved under the microscope on the outer surface of the plug 6, or in the case of an optical isolator, the reflected light from the end face 4b of the optical fiber 4 held by the plug 6 is output from a power meter, OTDR, or the like. A problem that a complicated operation is required in which the plug 6 is rotated in a state where the plug 6 is brought into contact with the bottom surface 8a and the side wall surface 8b of the holder 8 while being monitored using the optical measuring means and fixed at an angle at which the reflected light is most attenuated. There is.

Further, as shown in FIG. 6, an optical device 17 having an optical waveguide substrate 17b in which a plurality of optical waveguides 17a such as an optical switch, a star coupler, and a highly integrated transceiver are arranged in parallel. When an optical signal is transmitted and received through the optical waveguide 11, the V-groove array substrate 1 in which V-grooves 18 a capable of accurately holding the respective optical fibers 11 are arranged at predetermined positions corresponding to the respective optical waveguides 17 a of the optical waveguide substrate 17.
8 is used. However, when the applications of the plurality of optical waveguides 17a are different from each other such as the light emitting end and the light receiving end, individual processing such as oblique polishing processing or filter film forming processing is performed on the end face 11b of each optical fiber 11 where the core 11a is exposed. Therefore, when a V-groove array substrate 18 that integrally holds a plurality of optical fibers 11 is used, there is a problem that it is difficult to perform different processing on each end face 11b of each optical fiber 11. .

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above problems, and is a glass capable of accurately holding an optical fiber and easily positioning the held optical fiber with respect to other optical components. It is intended to provide a capillary.

[0007]

According to a first aspect of the present invention, there is provided a glass capillary tube having an insertion hole having an inner diameter slightly larger than that of a single-core optical fiber;
The outer surface has at least two flat portions provided at a predetermined distance from the central axis of the insertion hole. With this configuration, the positioning of the optical axis of the optical fiber inserted into the glass capillary and the optical axis of the other optical component can be accurately and easily performed by utilizing the one flat portion and the other flat portion of the outer surface of the glass capillary. Can be done.

The glass capillary according to a second aspect of the present invention is characterized in that the vertical distance between the central axis of the insertion hole and each of the flat portions is substantially equal. With this configuration, the positioning of the optical axis of the optical fiber inserted into the glass capillary and the optical axis of another optical component is performed by using any one or more flat portions of the outer surface of the glass capillary. Accurate and easy to do.

A glass capillary according to a third aspect of the present invention is characterized in that the outer surface is substantially rectangular.
With this configuration, by utilizing one flat portion of the outer surface of the glass capillary and another flat portion perpendicular thereto, the optical axis of the optical fiber inserted into the glass capillary and the optical axis of another optical component are used. Positioning can be performed accurately and easily. In addition,
A substantially rectangular shape is not limited to a rectangle or a quadrangle in a strict sense geometrically, but also includes, for example, a chamfered vertex portion to prevent cracking or chipping of the vertex portion, and the like. .

The glass capillary according to claim 4 of the present invention is characterized in that the outer surface is substantially square. With this configuration, by utilizing one flat portion of the outer surface of the glass capillary and another flat portion perpendicular thereto, the optical axis of the optical fiber inserted into the glass capillary and the optical axis of another optical component are used. Positioning can be performed accurately and easily. In this case, in particular, any one of the four sides of the outer surface of the glass capillary tube can be used as a reference surface, so that handling is easy and preferable. In addition, the substantially square is not limited to a square in a strict sense geometrically, and includes, for example, a chamfered vertex portion to prevent cracking or chipping of the vertex portion, and the like. .

In the glass capillary tube of the present invention, if the cylindrical surface circumscribing the outer surface has a predetermined diameter and the cylindrical surface circumscribing the outer surface has a predetermined cylindricity, It is preferable because it can be inserted into a holding member such as a sleeve having a cylindrical holding portion and held in a stable state. Further, when the cylindrical surface circumscribing the outer periphery of the glass capillary and the central axis of the insertion hole have a predetermined coaxiality, the positioning of the optical axis of the held optical fiber and the optical axis of another optical component can be easily performed. it can.

A glass capillary according to a fifth aspect of the present invention is characterized in that the flat portion has a surface roughness Ra value of 0.1 μm or less. With this configuration, when the glass capillary is made of transparent glass, the state of the insertion hole, the inserted state of the optical fiber, and the fixed state of the optical fiber can be easily confirmed from the flat part. The Ra value is defined as the surface roughness of the flat portion.
It is a value of the center line average roughness specified in JIS B0601, and the smaller the numerical value, the better the smoothness.

The glass capillary according to claim 6 of the present invention has a thickness of 1 mm and emits light having a wavelength of 350 nm to 500 nm.
It is characterized by being made of glass transmitting at least 0%. With this configuration, as an adhesive for fixing the optical fiber inserted into the glass capillary, a photocurable adhesive having sensitivity to blue light from ultraviolet to visible light can be used, so that it can be used in a short time. The optical fiber can be fixed to the glass capillary.

A glass capillary according to a seventh aspect of the present invention is made of glass containing alkali ions, and is characterized in that it is strengthened by generating a compressive stress layer on the surface by ion exchange. With this configuration, even if the glass capillary has some scratches due to machining or the like, it does not break when subjected to severe heat shock,
Even if the flare portion is greatly widened and the wall thickness is reduced, the flare portion is not chipped, so that it can be easily handled. In addition, glass capillaries containing moderately alkaline ions,
Since it can be manufactured by stretch molding using a glass drawing technique, the manufacturing cost can be reduced.

The glass capillary according to claim 8 of the present invention is characterized in that a flare portion which is smoothly continuous with the insertion hole is formed at the opening end of the insertion hole. With this configuration, the optical fiber can be easily inserted into the insertion hole of the glass capillary.

According to a ninth aspect of the present invention, in the optical fiber connection structure, the optical fiber is inserted and fixed in an insertion hole having an inner diameter slightly larger than that of a single-core optical fiber. A plug including a glass capillary having at least two flat portions provided at a predetermined distance from the central axis, an optical component connected to the plug, and a holder having a positioning surface for the flat portion of the glass capillary. In a state in which the optical axis of the optical fiber and the optical axis of the optical component are positioned with optical consistency by the contact between the flat portion provided on the glass capillary of the plug and the positioning surface of the holder. It is characterized by being fixed.
With this configuration, a plug having a single-core optical fiber,
It is possible to accurately and easily connect to other optical components.

According to a tenth aspect of the present invention, in the optical fiber connecting structure, the optical fiber is inserted and fixed in an insertion hole having an inner diameter slightly larger than that of a single-core optical fiber, and the outer surface of the insertion hole is fixed. A plurality of plugs each having a glass capillary having at least two flat portions provided at a predetermined distance from a central axis, an optical component having a plurality of optical axes connected to each of the plugs, A holder having a positioning surface for a plurality of plugs in which the flat portions provided on the glass capillaries of each plug are in contact with each other and aligned with each other, and the flat portions provided on the glass capillaries of the plurality of plugs and the The optical axis of the optical fiber and the plurality of optical axes of the optical component are fixed in a state of being positioned with optical consistency by abutting on the positioning surface of the holder. With this configuration, it is possible to accurately and easily connect a plurality of plugs having a single-core optical fiber and an optical component having a plurality of optical axes, and in particular,
Even when the applications of a plurality of optical axes (for example, optical waveguides) of optical components are different from each other, the tip of each optical fiber connected to each optical waveguide or the like can be individually processed in an optimum state according to each application. It will be easier.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1A is an end view of one embodiment of the glass capillary of the present invention, FIG.
(C) is an explanatory view of the outer surface of the glass capillary, FIG. 2 (A) is an end view showing a first use example of the glass capillary of the present invention,
3 (B) is a longitudinal side view thereof, FIG. 3 (A) is a perspective view showing a second use example of the glass capillary of the present invention, and FIG. 3 (B) is a perspective view showing a third use example of the glass capillary of the present invention. FIG.
In each figure, 21 is a glass capillary, 22 is an insertion hole for an optical fiber, 23 is a flare portion for guiding the optical fiber to the insertion hole, 24 is an optical fiber, 25 is an adhesive, 26 is an optical fiber 24 in the glass capillary 21. A fixed plug, 27 is an optical device to which the plug 26 is connected, and 28 is a holder.

The glass capillary tube 21 of the present invention contains about 6% by mass of Na ₂ O, has a thickness of 1 mm, and has a wavelength of 350 nm to 50 nm.
It is made of borosilicate glass that transmits 60% or more of 0 nm light, and is subjected to an ion exchange treatment to form a compressive stress layer on the surface. As shown in FIG. 1, the cross-sectional shape having a high dimensional accuracy with a distance L between opposing sides of the outer surface being 1273 μm ± 1.0 μm is a square prism, and
Has an inner diameter of 127 μm ± 1.0 μm, which is slightly larger than the optical fiber 24 having a diameter of 125 μm, and is manufactured so that the optical fiber 24 can be inserted and held.

As shown in FIG. 1A, a vertical distance S1 from the center axis 22a of the insertion hole 22 to the flat surface portion 21b of the outer surface and a center axis 22a are formed on the outer surface of the glass capillary tube 21.
The vertical distance S2 from the plane to the plane portion 21c is 636 μm.
m ± 1.0 μm. That is, the glass capillary 21
The optical fiber 24 having a diameter of 125 μm from which the coating has been removed can be inserted into the insertion hole 22 so that the optical fiber 24 can be positioned with high precision. Substantially conical flare portion 2 having an opening diameter of about 0.7 mm for guiding
3 are provided.

Next, an example of manufacturing the glass capillary tube 21 will be described.

First, a preform having a square cross section is prepared by grinding the outer surface so that each plane portion is at a predetermined distance with respect to the hole, and the preform is heated to have a predetermined cross-sectional dimension / size. While controlling the shape, it is extended and formed into a long capillary tube having an insertion hole 22 having a predetermined dimensional accuracy. The long capillary thus obtained is cut into a predetermined length, and a flare portion 23 is provided at one end of the insertion hole 22 by a chemical etching method or the like, thereby producing a glass capillary 21.

The glass capillary 2 obtained as described above
An example in which the optical fiber 24 is connected to another optical component by using No. 1 will be described.

First, as shown in FIG. 1B, an optical fiber 24 is inserted from a flare portion 23 into an insertion hole 22 of a glass capillary 21. In the case of the polarization-maintaining optical fiber, the flat portion 21 b or the flat portion 21 on the outer surface of the glass capillary 21 is used.
After positioning so that the polarization plane is parallel to c,
It is fixed with an epoxy resin adhesive 25, and the end face 21a is polished, or the tip face of the optical fiber 24 is polished by spherical polishing.
The core portion 24a is formed into a spherical shape by heat molding, etching, or the like.
Are made to protrude from the clad portion to produce the plug 26.

Next, the plug 2 obtained as described above
6, other optical components, for example, the light input / output unit 27a
Insertion hole 2 of glass capillary tube 21 in optical device 27 provided with
An example in which the optical fiber 24 held at 2 is positioned and connected to the optical input / output unit 27a will be described.

As shown in FIG. 2, the flat portion 21b of the glass capillary 21 of the plug 26 is placed on the bottom surface 28a of the holder 28.
The flat portion 21c is brought into contact with the side wall surface 28b of the holder 28, and the end surface 21a is brought into contact with the end surface of the optical device 27. By arranging in this manner, the optical fiber 2 held by the plug 26 and having a spherical end face and projected
4, the optical axis of the core portion 24a is accurately positioned in a pressed state with respect to the optical axis of the optical input / output portion 27a of the optical device 27. When the plug 26 is fixed to the holder 28 with an adhesive while maintaining this state, the connection is completed.

As described above, the glass capillary tube 21 of the present invention
Is used, the core portion 24a of the held optical fiber 24
Is maintained in a relative position with respect to the flat portions 21b, 21c of the outer surface of the glass capillary 21, and the flat portions 21b, 21
By using c to fix the plug 26 to the holder 28 holding the optical device 27, the optical axis of the core portion 24a of the optical fiber 24 and the optical axis of the optical input / output portion 27a can be accurately and easily adjusted. It can be arranged at the optimal position where it is connected with optical consistency. In this embodiment, 0.3 d
The connection loss within B and the return loss exceeding 50 dB could be achieved.

Even when there is a gap between the flat portion 21c and the side wall surface 28b of the holder 28, since the flat portion 21b of the plug 28 is stably abutted against the bottom surface 28a of the holder 28, an appropriate spacer Can be easily fixed at the optimum position.

By the way, the glass capillary tube 21 of the present invention comprises:
As shown in FIG. 1C, a cylindrical surface T circumscribing the outer surface thereof
Is, for example, 1800 μm ± 10 μm and the cylindrical surface T has an outer surface shape having a cylindricity within 10 μm. The optical axis of the optical fiber 24 held in the insertion hole 22 of the capillary 21 and the optical axis of another optical component can be easily positioned.
In addition, the cylindrical surface T and the central axis 22a of the insertion hole 22 are, for example, a glass capillary tube 21 having a coaxiality within 10 μm.
Is to make it easier to position the held optical axis of the optical fiber 24 and the optical axis of the other optical component by inserting the optical axis of the other optical component into a sleeve or the like in which the optical axis of the other optical component is positioned at the center in advance. Can be.

As shown in FIG. 3, by stacking and aligning a plurality of the above-mentioned glass capillaries 21,
High-density alignment connection of optical fibers, which conventionally used a V-groove array substrate, is now possible. By taking advantage of this advantage, the optical fiber 24 held in the glass capillary 21 can be used.
A plug 26 having a plurality of optical waveguides 37a having different uses such as a light emitting end and a light receiving end is manufactured by manufacturing a plug 26 having different specifications of the end face 24a according to the application. By arranging and arranging the 26 and abutting against the holder 38, it becomes possible to connect a plurality of optical fibers 24 to each optical waveguide 37a according to the application.

4 (A) to 4 (E) are explanatory views of modified embodiments of the present invention. First, FIG. 4 (A) shows that the outer surface of the glass capillary tube 31 is substantially Two rectangular flat sections 31a, 31 on the long side
“b” is such that the distances from the central axis of the insertion hole 32 are substantially equal and parallel, and the parallel plane portions 31a and 31b are used as a reference plane for optical axis alignment and the like. FIG. 4 (B) is a diagram in which the outer surface of the glass capillary 41 is formed in a rectangular shape as described above, and the center axis of the insertion hole 42 is shifted from the center of the glass capillary 41 to one side in the short side direction. Also in this case, the parallel plane portion 41a on the long side is
41b is used as a reference plane for optical axis alignment and the like. 4C shows an embodiment in which a plurality of the glass capillaries 41 shown in FIG. 4B are used. In this case, the flat portions 41a, 4a,
1b shows a high-density arrangement by contacting 1b with each other. FIG. 4D shows a glass capillary tube 51.
Is a substantially equilateral triangular cross section, and three plane portions 51a, 51b, 51c are formed at the same distance from the central axis of the insertion hole 52. In this case, these three planes are shown. At least one, two, or three of the portions 51a, 51b, and 51c are used as reference surfaces for optical axis alignment and the like. FIG. 4E shows that the outer surface of the glass capillary 61 is made substantially hexagonal and the insertion hole 62 is formed.
The distances from the center axis of each side to the plane portions 61a to 61f of each side are formed substantially equal to each other, and at least one surface or two or more surfaces are used as a reference surface for optical axis alignment or the like. As an application thereof, for example, it is illustrated that a plurality of glass capillaries 61 can be arranged in a honeycomb arrangement.

The cross section of the outer surface of the glass capillary of the present invention is formed symmetrically with respect to the plane including the center axis of the insertion hole on the outer surface and at a predetermined distance substantially equal to the center axis. There is no particular limitation as long as it has two or more plane portions. The number of the flat portions is not particularly limited as long as the number is two or more. For example, the outer surface may have a circular cross-sectional shape, and a part or a plurality of the parts may be flatly polished or cut and removed to form the flat part. In addition, it is preferable to form two or more flat portions at predetermined positions that are substantially rotationally symmetric with respect to the center axis of the insertion hole.
Further, the cross-sectional shape of the outer surface may be a polygon such as a triangle, a quadrangle, or a hexagon, and two or more of the outer surfaces of the polygon may be the flat portions. Polygons such as triangles, quadrangles, and hexagons are not limited to polygons in a strictly geometrical sense.For example, those with chamfered vertices to prevent cracking or chipping at the vertices Etc. are also included. Preferred cross-sectional shapes of the outer surface include a substantially rectangular shape in which opposing planes are parallel and adjacent planes are perpendicular to each other, and particularly include a substantially square shape.

The insertion hole can be used as long as it has a slightly larger inner diameter than the single-core optical fiber and can insert and hold and fix one single-core optical fiber inside.
The cross-sectional shape of the insertion hole is generally circular,
The present invention is not limited to this. For reducing the insertion resistance and facilitating the handling of the adhesive for fixing the optical fiber and the refractive index matching agent, etc., a triangular, quadrangular, hexagonal or other substantially polygonal shape is used. Good.

As the glass containing alkali ions, any glass containing ions of alkali elements such as Li and Na can be used, and borosilicate glass and lithium-alumina-silicate glass ceramics are suitable. ing.

[0035]

According to the first aspect of the present invention, since two or more flat portions are provided on the outer surface of the glass capillary, the optical axis of the optical fiber in the glass capillary can be easily adjusted using the flat portion. An optical signal can be connected so as to coincide with the optical axis of the optical component.

According to the second aspect of the present invention, the optical axis of the optical fiber inserted into the glass capillary and the other optical axis are utilized by utilizing any one or more flat portions of the outer surface of the glass capillary. Positioning of the component with the optical axis can be performed accurately and easily.

According to the third aspect of the present invention, by utilizing one plane portion of the outer surface of the glass capillary tube and another plane portion perpendicular thereto, the optical axis of the optical fiber inserted into the glass capillary tube and the other portion are used. Can be accurately and easily positioned with respect to the optical axis.

According to the fourth aspect of the present invention, by utilizing one plane part of the outer surface of the glass capillary and another plane part perpendicular to the outside, the optical axis of the optical fiber inserted into the glass capillary and the other plane part are used. Can be accurately and easily positioned with respect to the optical axis of the optical component. In this case, any one of the four sides of the outer surface of the glass capillary can be used as the reference surface, so that the handling is easy and preferable.

According to the fifth aspect of the present invention, when the glass capillary is made of transparent glass, the state of the insertion hole, the inserted state and the fixed state of the optical fiber can be easily confirmed from the flat part.

According to the invention of claim 6, as the adhesive for fixing the optical fiber inserted into the glass capillary, a photocurable adhesive having sensitivity to blue light from ultraviolet to visible light is used. As a result, the optical fiber can be fixed to the glass capillary in a short time, and the assembly cost of the optical device can be reduced.

According to the seventh aspect of the present invention, even if the glass capillary has some scratches due to machining or the like, it is not damaged when a severe heat shock is applied, and the flare portion is greatly expanded to increase the flesh. Even if the thickness becomes thin, the chip does not chip, so that it can be easily handled. Further, a glass capillary containing an appropriate amount of alkali ions can be produced by stretch molding using a glass drawing technique, so that the production cost can be reduced.

According to the eighth aspect of the present invention, the optical fiber can be easily inserted into the insertion hole of the glass capillary.

According to the ninth aspect of the present invention, a plug having a single-core optical fiber can be accurately and easily connected to another optical component.

According to the tenth aspect of the present invention, a plurality of plugs having a single optical fiber and an optical component having a plurality of optical axes can be accurately and easily connected to each other. Multiple optical axes of an optical component (eg, optical waveguide)
It is easy to individually treat the tip of each optical fiber connected to each optical waveguide or the like to an optimum state according to each use even when the uses are different.

[Brief description of the drawings]

FIG. 1A is an end view of an embodiment of a glass capillary of the present invention, FIG. 1B is a perspective view thereof, and FIG. 1C is an explanatory view of an outer surface of the glass capillary.

FIG. 2A is an end view showing a first use example of the glass capillary of the present invention, and FIG. 2B is a longitudinal side view thereof.

FIG. 3A is a perspective view showing a second use example of the glass capillary of the present invention, and FIG. 3B is a perspective view showing a third use example of the glass capillary of the present invention.

FIGS. 4A to 4E are explanatory views of modified embodiments of the present invention.

5A and 5B are explanatory views showing a connection operation between an optical fiber and another optical component using a conventional glass capillary tube, wherein FIG. 5A is an end view, and FIG.

FIG. 6 shows a conventional optical device having a plurality of optical waveguides and V
FIG. 4 is a perspective view showing a connection state with a plurality of optical fibers using a groove array substrate.

[Explanation of symbols]

21, 31, 41, 51, 61: glass capillaries 21b, 21c, 31a, 31b, 41a, 41b, 5
1a to 51c, 61a to 61, flat portion 22, 32, 42, 52, 6, insertion hole 22a, central axis 23, flare portion 24, optical fiber 25, adhesive 26, plug 27, 37 Optical device 28, 38 Holder

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanobu Minami 2-7-1 Hararashi, Otsu-shi, Shiga Inside Nippon Electric Glass Co., Ltd. (72) Takashi Tsuneoka 2-7-1 Hararashi, Otsu-shi, Shiga Nippon Electric Glass Co., Ltd. F-term (reference) 2H036 QA12 QA17 QA20 2H037 BA24 DA04 DA15

Claims (10)

[Claims] 1. An insertion hole having an inner diameter slightly larger than that of a single-core optical fiber, and at least two flat portions provided on an outer surface at a predetermined distance from a center axis of the insertion hole. And a glass capillary. 2. The glass capillary according to claim 1, wherein a vertical distance between a center axis of the insertion hole and each of the flat portions is substantially equal. 3. The glass capillary according to claim 1, wherein the outer surface is substantially rectangular. 4. The glass capillary according to claim 1, wherein the outer surface is substantially square. 5. The Ra value of the surface roughness of the flat portion is 0.1.
The glass capillary according to any one of claims 1 to 4, wherein the glass capillary is not more than μm. 6. A wavelength of 350 nm to 500 n at a thickness of 1 mm.
The glass capillary according to any one of claims 1 to 5, wherein the glass capillary is made of glass that transmits 60% or more of light of m. 7. The glass capillary tube according to claim 1, wherein the glass capillary tube is made of glass containing alkali ions, and is strengthened by forming a compressive stress layer on the surface by ion exchange. 8. The glass capillary tube according to claim 1, wherein a flare portion smoothly connected to the insertion hole is formed at an opening end of the insertion hole. 9. An optical fiber is inserted and fixed in an insertion hole having an inner diameter slightly larger than that of a single-core optical fiber,
A plug including a glass capillary having at least two flat portions provided on an outer surface thereof at a predetermined distance from a center axis of the insertion hole, an optical component connected to the plug, and positioning of the glass capillary relative to the flat portion A holder having a surface, and a flat portion provided on the glass capillary of the plug and a positioning surface of the holder are brought into contact with each other, so that the optical axis of the optical fiber and the optical axis of the optical component have optical consistency. A connection structure for an optical fiber, wherein the optical fiber is fixed in a state where the optical fiber is positioned. 10. An optical fiber is inserted and fixed in an insertion hole having an inner diameter slightly larger than that of a single-core optical fiber, and has at least two surfaces provided on an outer surface thereof at a predetermined distance from a center axis of the insertion hole. A plurality of plugs having a glass capillary having a flat portion, an optical component having a plurality of optical axes connected to each plug, and the flat portions provided on the glass capillaries of each of the plurality of plugs are mutually connected. A holder having a positioning surface for a plurality of plugs abutted and aligned, and a contact between a flat surface portion provided on a glass capillary tube of the plurality of plugs and a positioning surface of the holder, whereby the optical fiber An optical fiber connection structure, wherein an optical axis and a plurality of optical axes of the optical component are fixed while being positioned with optical consistency.