JPH10133040A - Method for expanding core diameter of optical fiber, and optical fiber holding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the eccentricity of an expanded core by uniformizing a heat temperature distribution at the time of the heat expansion of the core diameter of an optical fiber. SOLUTION: This device consists of an optical fiber holding base 2 which has a body part 3 and two-leg parts 4A and 4B, crossing the body part 3 at right angles, molded integrally in a channel shape and also has optical fiber extension and fixation grooves 5A and 5B cut in the two-leg parts 4A and 4B in parallel to the body part 3, pressure plates 6A and 6B which press an optical fiber F arrayed in the said optical fiber extension and fixation grooves 5A and 5B, and a rotating means 7 which rotates the optical fiber holding device on the groove axis of the optical fiber extension and fixation grooves 5A and 5B as an axis of rotation; and the optical fiber F is extended between the optical fiber extension and fixation grooves 5A and 5B and fixed with the pressure plates 6A and 6B, and while a microburner 10 is applied to a local place A of the optical fiber F at right angles, the optical fiber F is rotated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber core diameter enlarging method capable of precisely enlarging an optical fiber core diameter without causing core eccentricity, and an optical fiber holding device used for the method.

[0002]

2. Description of the Related Art When two optical fibers having different core diameters or an optical fiber having a different mode field are interconnected with an optical semiconductor device, the spot size of light at the connection surface becomes discontinuous. A large connection loss occurs. In order to reduce the connection loss, it is desirable that the mode fields at the connection surfaces between the optical fibers or between the optical fibers and the optical semiconductor element be made to have the same size.
As a measure for this, there is a technique of reducing the connection loss by enlarging the core diameter of the connection end of the optical fiber having the smaller core diameter in accordance with the mode field of the optical fiber or the optical semiconductor element to be connected. It has been put to practical use.

[0003] The core diameter of the optical fiber is increased by adding a dopant for increasing the refractive index of the core into the core or using an optical fiber doped with a dopant for lowering the refractive index of the clad in the clad. Is heated by a micro burner or the like to thermally diffuse the dopant in the core or clad.
In this case, the portion of the optical fiber to be heated must be stretched and held straight. FIG. 3 shows a front view of such a conventional optical fiber stretching and holding apparatus. The conventional optical fiber tension holding device 21 includes a fixture 22A and a fixture 22B for holding and fixing both sides of the heated portion A of the optical fiber F, and the fixture 22A and the fixture 22B are configured independently of each other. ing. An optical fiber F is used for the fixtures 22A and 22B.
23A and 23B are provided in the direction in which the optical fiber F is stretched, and the holding lids 24A and 24B cover the grooves 23A and 23B. The tension holding of the optical fiber F is performed by inserting both ends of the heated portion A of the optical fiber F into the grooves 23A and 23B of the fixtures 22A and 22B, applying tension to the optical fiber F, and straightening the optical fiber F (the tension applying device is (Not shown), and press down lids 24A and 24B from above the optical fiber F.
And fixed. After the optical fiber F is stretched and held, the heated portion A is heated for a required time by the micro burner 25, and the core diameter of the heated portion A is enlarged. Thereafter, the optical fiber F is cut at a portion A where the core diameter is enlarged, and a connection end face is formed.

[0004]

As described above, the core diameter of the optical fiber having the smaller core diameter is enlarged, and the optical fiber or the optical semiconductor element to be connected is connected so that the size of the mode field is substantially the same. Even in such a case, if the expanded core is eccentric, a large connection loss may be caused even though the bent core is expanded. Reduction of connection loss is strongly required in optical members. For example, when interconnecting single-mode optical fibers having a core diameter of 10 μm, it is desirable to suppress the connection loss to within 0.2 dB. In order to suppress the connection loss within 0.2 dB, as is known from a calculation example diagram showing the relationship between the optical fiber axis deviation and the connection loss shown in FIG. 4, the optical fiber axis deviation, in other words, the core eccentricity is 1 μm. Must be kept within. In addition, if the eccentricity of the enlarged core is large, there is also a problem that it takes a long time to align the optical core with the optical semiconductor element, and the assembling workability is reduced. From such a problem, how to expand the core without causing eccentricity has been an important technical problem in the method of expanding the core diameter of the optical fiber.

However, in the above-mentioned conventional means for enlarging the core diameter of an optical fiber, the fixtures 22A and 22B for extending and holding both sides of the heated portion A of the optical fiber F are independent from each other. Therefore, it is difficult to accurately install the fixtures 22A and 22B so that the axes of the fixtures 22A and 22B do not shift in the horizontal direction or the left and right direction. As a result, the fixtures 22A, 22A,
The optical fiber F stretched and fixed between 2B was likely to be displaced in the horizontal or horizontal direction in the stretching direction. This displacement of the optical fiber F in the direction in which it is stretched causes unevenness in the heating temperature distribution when the micro burner 25 is applied to the heated portion A of the optical fiber F. Irregularities in the heating temperature distribution of the optical fiber F cause variations in the diffusion of the dopant, making the expansion of the core diameter of the optical fiber F non-uniform,
This was a major factor causing eccentricity in the core. Further, there is a problem that the optical fiber F is locally softened and bent due to uneven heating. The optical fiber F has a very small diameter (for example, 125 μm for a single mode optical fiber).
m), there is a problem even if the optical fiber F stretched between the fixtures 22A and 22B has a slight horizontal or horizontal shift.

Accordingly, an object of the present invention is to provide a method for expanding the core diameter of an optical fiber and an optical fiber holding apparatus which eliminates uneven temperature distribution when the optical fiber is heated by a micro burner and does not cause core eccentricity. It is in.

[0007]

According to a first aspect of the present invention, there is provided an optical fiber comprising a core and a clad to which a doping agent is added, which is locally heated by a micro burner, and the heated local doping agent is provided. In the method of expanding the core diameter of the optical fiber by expanding the core diameter of the optical fiber by diffusing the optical fiber, the optical fiber fixing portion provided on both U-shaped legs of the optical fiber holding means integrally formed in a U-shape. An optical fiber characterized by stretching and fixing an optical fiber in parallel with the body of the U-shaped optical fiber holding means, and applying a micro-burner vertically to a portion of the optical fiber between the optical fiber fixing portions and heating the optical fiber. An object of the present invention is to provide a method for enlarging a core diameter.

[0008] In a second aspect, the present invention provides an optical fiber in which a doping agent is added to one of a core and a clad, and the optical fiber is heated by a micro burner to diffuse the doping agent at the heated region. In the method of enlarging the core diameter of an optical fiber, the U-shaped light is inserted between the optical fiber fixing portions provided on both U-shaped legs of the optical fiber holding means integrally formed in the U shape. An optical fiber is stretched and fixed in parallel with the body of the fiber holding means, and a micro-burner is applied vertically to the local portion of the optical fiber between the optical fiber fixing portions from one direction while heating, and the optical fiber is turned around the rotation axis and inverted. It is an object of the present invention to provide a method for enlarging the core diameter of an optical fiber, wherein the method is rotated to uniformly heat the entire outer periphery of the optical fiber.

According to a third aspect of the present invention, the present invention provides an optical fiber comprising a core and a clad to which a doping agent is added, wherein both ends of the optical fiber are held, and a local portion of the optical fiber is vertically heated by a micro burner. An optical fiber holding device for use in an optical fiber core diameter expanding device for expanding a core diameter of an optical fiber by diffusing a local doping agent. The optical fiber holding device includes a trunk and a bipod perpendicular to the trunk. And an optical fiber holding base in which both legs are provided with grooves for holding and fixing the optical fiber in parallel with the body, and an optical fiber holding and fixing groove in both legs of the optical fiber holding base. And a holding plate for holding the optical fibers arranged in a line.

[0010] In a fourth aspect, the present invention is directed to an optical fiber in which a doping agent is added to one of a core and a clad, and both ends of the optical fiber are held, and a local portion of the optical fiber is vertically heated by a micro burner. An optical fiber holding device for use in an optical fiber core diameter expanding device for expanding a core diameter of an optical fiber by diffusing a local doping agent. The optical fiber holding device includes a trunk and a bipod perpendicular to the trunk. And an optical fiber holding base in which grooves for fixing and fixing the optical fiber parallel to the body are formed in both legs, and an optical fiber is fixed to both legs of the optical fiber holding base. An optical fiber, comprising: a holding plate that holds an optical fiber aligned with a groove; and a rotation unit that rotates the optical fiber holding table around a groove axis of the optical fiber tension fixing groove as a rotation axis. Retention It is to provide a location.

[0011]

In the method for enlarging the core diameter of an optical fiber according to the first aspect, the optical fiber is stretched and held by an integrally formed optical fiber holding means. Since the optical fiber holding means by integral molding can form the structural dimensions with high precision,
When the optical fiber is stretched and fixed to the optical fiber holding means, no deviation occurs in the horizontal and horizontal directions in which the optical fiber is stretched, and the local portion of the optical fiber is uniformly heated by the micro burner, and the core is eccentric. The diameter of the core can be increased without causing the problem.

In the method for enlarging the core diameter of an optical fiber according to the second aspect, the optical fiber is stretched and held by an optical fiber holding means integrally formed, and the optical fiber is turned around the optical fiber axis as a rotation axis. In this method, the local portion of the optical fiber is vertically heated by a micro burner, and the entire outer peripheral portion of the local portion of the optical fiber is uniformly heated, so that the diffusion of the dopant becomes uniform and the eccentricity of the core of the enlarged portion does not occur.

Since the optical fiber holding device according to the third aspect is formed by integral molding, the structure can be formed in a desired shape with extremely high precision. In addition, the optical fiber holding device has a body and a bipedal section orthogonal to the body, and the optical fiber extension fixing grooves of both legs are cut in parallel with the body, so that the optical fiber is As long as the optical fiber is aligned with the fiber tension fixing groove, the optical fiber does not shift in both the horizontal and horizontal directions in the tension direction. Therefore,
The stretched optical fiber is locally heated uniformly by the micro burner, and the core diameter can be increased without causing core eccentricity.

The optical fiber holding device according to the fourth aspect has the same function as that of the optical fiber holding device according to the third aspect due to the integral molding structure, and at the same time, the optical fiber holding base is attached and fixed. Since the groove is configured to be rotatable about the groove axis, the outer periphery of the local portion of the optical fiber is evenly heated without uneven temperature, the diffusion of the dopant becomes uniform, and the core is enlarged and formed without eccentricity. what if,
In the case where the independent optical fiber fixing stand of the conventional structure is rotated around the optical fiber as the rotation axis, the axis shift between the two optical fiber fixing stands and the rotation of the two optical fiber fixing stands are caused. Since it is difficult to completely synchronize the movement, not only the eccentricity of the expanded core due to uneven heating temperature distribution of the heated portion of the optical fiber occurs, but also the twisting force is applied to the optical fiber, causing the optical fiber to twist. become.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a method for enlarging a core diameter of an optical fiber and an optical fiber holding apparatus according to the present invention. It should be noted that the present invention is not limited by this.

FIGS. 1A and 1B are a top view and a side view showing an embodiment of an optical fiber holding base according to the present invention. The optical fiber holding base 2 is provided with a trunk 3 and two legs 4A and 4B orthogonal to the trunk 3, and is integrally molded in a U-shape. The legs 4A and 4B are parallel to the trunk 3. The optical fiber tensioning and fixing grooves 5A and 5B are respectively formed. The optical fiber holding base 2 is manufactured by sintering a ceramic material such as zirconia (ZrO ₂ ) or a glass substrate or the like, which is unlikely to cause processing distortion or temporal distortion during use. Stainless steel and steel are not preferable as the material of the optical fiber holding base 2 because they easily cause processing distortion and temporal distortion during use.
9A and 9B are screw holes for fixing the optical fiber holding base 2 to optical fiber pressing plates 6A and 6B, which will be described later, and the rotary connection plate 8.

The optical fibers F are aligned in a state where they are straightened to the optical fiber tension fixing grooves 5A and 5B, and are pressed by pressing plates 6A and 6B (not shown in FIG. 1) to form the grooves 5A and 5B. Fixed to The optical fiber F stretched and fixed between the legs 4A and 4B is heated by applying a micro burner 10 (not shown) perpendicularly to the local area A thereof.

FIG. 2 is a front view showing another embodiment of the optical fiber holding device of the present invention. Optical fiber holding device 1
Has a configuration in which the optical fiber holding base 2 described in FIG. 1 is rotated. The optical fiber holding base 2 has the same structure as that described in FIG. 1, and the U-shaped two legs 4A and 4B of the optical fiber holding base 2 are provided with optical fiber tension fixing grooves 5A and 5B. Pressing plates 6A and 6B for fixing the stretched optical fiber F are detachably attached by screws screwed into screw holes 9A and 9B. Further, the optical fiber holding device 1 is provided with a turning device 7 for turning the optical fiber holding device 1 by 180 degrees with the optical fiber tensioning and fixing grooves 5A and 5B as turning axes. The optical fiber holding base 2 and the holding plates 6A, 6B are connected to each other by screws screwed into screw holes 9A, 9B. The rotation axis of the rotation device 7 is formed so as to coincide with the central axis of the optical fiber tension fixing grooves 5A and 5B.

In the optical fiber holding device 1 having such a configuration,
The optical fibers F are aligned in a state of being stretched straight between the optical fiber tension fixing grooves 5A and 5B, and
A and 6B fix to the grooves 5A and 5B. The optical fiber F stretched and held between the legs 4A and 4B in this manner is
The rotation device 7 repeatedly applies a reverse rotation of approximately 180 degrees with the central axis of the stretched optical fiber F as a rotation axis. The heating of the optical fiber F is performed by repeating the inversion rotation of the optical fiber F.
Is performed by vertically applying the micro burner 10 to the local area A. For example, a mixed gas of propane and oxygen is used for the micro burner 10, and the heating temperature and the heating time vary depending on the type of the optical fiber, the enlarged size of the core, and the like, but are generally from 1500 ° C to 2000 ° C for 1 to 2 minutes. is there. After cooling, the heated optical fiber F is cut at the center of the heating area A, and an optical fiber having an enlarged core end face is obtained.

-Measurement of connection loss- Using the optical fiber holding device 1 of the present invention shown in FIG. 2, the rotation device 7 is stopped, and the local portion A of the optical fiber F is heated by the micro burner 10 to increase the core diameter. The optical fiber of Example 1 and the optical fiber of Example 2 in which the local diameter A of the optical fiber F was heated by the micro burner 10 by rotating the rotation device 7 to increase the core diameter were compared with the conventional optical fiber of FIG. When the local fiber A of the optical fiber F is heated by the micro burner 25 using the optical fiber holding device 21 and the core diameter is enlarged, the optical fiber of Comparative Example 1 is interconnected with the optical fiber having the same core diameter by the optical connector. Was measured. The results are shown in Table 1 below.

As can be seen from the measurement results in Table 1, the optical fibers F of Examples 1 and 2 in which the core diameter was expanded by using the optical fiber holding device 1 of the present invention were compared with the optical fibers F of Comparative Example 1. Connection loss is greatly reduced. In particular, the optical fiber F of the second embodiment, in which the core diameter is enlarged by heating the optical fiber holding device 1 while rotating it, is the optical fiber F of the comparative example 1.
The connection loss is significantly reduced by about 60% as compared with FIG.
The low connection loss indicates that the eccentricity of the enlarged core of the optical fiber is small. As described above, the core-enlarged optical fiber formed by the method for enlarging the core diameter of an optical fiber using the optical fiber holding device 1 of the present invention has a small eccentricity of the enlarged core and is interconnected with another optical fiber or an optical semiconductor element. Connection loss at the time of connection can be extremely reduced.

[0022]

[Table 1] However, the above-mentioned measured values indicate the average value of the measured values of 14 samples, each of which takes 14 samples.

[0023]

According to the method for enlarging the core diameter of an optical fiber of the present invention, the portion to be heated of the optical fiber can be uniformly heated, so that the core can be enlarged without eccentricity. Therefore, the optical fiber whose core is expanded by the present method can be interconnected with another optical fiber or an optical semiconductor device with low connection loss. Further, since the optical fiber holding device of the present invention is formed with high precision by integral molding, the optical fiber stretched on the optical fiber holding device does not have a displacement in the stretching direction,
When heating the local part of the optical fiber, the outer circumference can be heated evenly and evenly, so the core is expanded and formed without eccentricity,
It is possible to provide an optical fiber having a large core diameter and a small connection loss.

[Brief description of the drawings]

FIG. 1 shows an embodiment of an optical fiber holding base according to the present invention, wherein FIG. 1 (a) is a top view thereof and FIG. 1 (b) is a side view thereof.

FIG. 2 is a front view showing one embodiment of the optical fiber holding device of the present invention.

FIG. 3 is a front view showing a conventional optical fiber holding device.

FIG. 4 is a calculation example diagram showing a relationship between an axial deviation of an optical fiber and a connection loss.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber holding device 2 Optical fiber holding base 3 Body 4A, 4B Leg 5A, 5B Optical fiber tension fixing groove 6A, 6B Holding plate 7 Rotating device 8 Rotating connecting plate 9A, 9B Screw hole 10 Micro Burner F Optical fiber A Heated area

Claims (4)

[Claims] An optical fiber in which a doping agent is added to one of a core and a clad, and the local diameter of the optical fiber is heated by a micro burner to diffuse the doping agent in the heated region, thereby expanding the core diameter of the optical fiber. In the method of expanding the core diameter of the fiber, between the optical fiber fixing portions provided on the U-shaped both legs of the optical fiber holding means integrally formed in a U-shape, parallel to the trunk of the U-shaped optical fiber holding means. A method for enlarging the core diameter of an optical fiber, wherein a micro-burner is vertically applied to a local portion of the optical fiber between the optical fiber fixing portions and heated. 2. An optical fiber in which a doping agent is added to one of a core and a clad, and a local area of the optical fiber is heated by a micro-burner, and the doping agent at the heated area is diffused to enlarge the core diameter of the optical fiber. In the method of expanding the core diameter of the fiber, between the optical fiber fixing portions provided on the U-shaped both legs of the optical fiber holding means integrally formed in a U-shape, parallel to the trunk of the U-shaped optical fiber holding means. An optical fiber is stretched and fixed, and a micro-burner is applied vertically from one direction to the local portion of the optical fiber between the optical fiber fixing portions, and the optical fiber is heated and turned around the optical fiber axis as a rotation axis while heating. A method for enlarging the core diameter of an optical fiber, comprising uniformly heating the entire outer periphery of the optical fiber. 3. An optical fiber in which a doping agent is added to one of a core and a clad, wherein both ends of the optical fiber are held, and a local portion of the optical fiber is vertically heated by a micro burner to diffuse the doping agent at the heated local portion. An optical fiber holding device used in an optical fiber core diameter enlarging device for enlarging an optical fiber core diameter by providing a trunk portion and a two-leg portion orthogonal to the trunk portion, and integrally molding into a U-shape. An optical fiber holding base in which grooves for optical fiber tensioning and fixing parallel to the trunk are carved on both legs, and an optical fiber aligned with the optical fiber tensioning and fixing grooves of both legs of the optical fiber holding base. An optical fiber holding device comprising a holding plate for holding. 4. An optical fiber in which a doping agent is added to one of a core and a clad, wherein both ends of the optical fiber are held, and a local portion of the optical fiber is vertically heated by a micro burner to diffuse the doping agent at the heated local portion. An optical fiber holding device used in an optical fiber core diameter enlarging device for enlarging an optical fiber core diameter by providing a trunk portion and a two-leg portion orthogonal to the trunk portion, and integrally molding into a U-shape. An optical fiber holding base in which grooves for optical fiber tensioning and fixing parallel to the trunk are carved on both legs, and an optical fiber aligned with the optical fiber tensioning and fixing grooves of both legs of the optical fiber holding base. An optical fiber holding device comprising: a holding plate for holding; and a rotating means for rotating the optical fiber holding base with a groove axis of the optical fiber tension fixing groove as a rotation axis.