JP2000275454A - Optical fiber, manufacture of optical fiber, optical fiber assembly and manufacture of optical fiber assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce transmission losses by providing in a portion of an optical fiber element an inflated core portion where cores smoothly increase in diameter and then return to their original diameters, setting the length from the end of the inflated core portion to the portion of the maximum core radius at a specific value or more, and setting the maximum core radius of the inflated core portion at a specific ratio or less. SOLUTION: An inflated core portion A where cores 2a, 2b smoothly increase in diameter and then return to their original diameters is provided in a portion of an optical fiber 100. The length (d) of the inflated core portion A from an end to a position where a maximum core radius (h) is reached is 1.5 mm or more. The maximum core radius (h) of the inflated core portion A is 1 % or less of the length (d). Hence, losses resulting from leaking light at the inflated core portion and losses resulting from misalignment of an optical axis at a connection can both be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber, a method for manufacturing an optical fiber, an optical fiber assembly, and a method for manufacturing an optical fiber assembly, and more particularly, to an optical fiber and an optical fiber capable of reducing transmission loss. The present invention relates to a method, an optical fiber assembly and a method for manufacturing the optical fiber assembly. In particular, the optical fiber, other optical fiber, light source,
It is useful for connecting to information processing devices and optical communication equipment.

[0002]

2. Description of the Related Art A manufacturing method according to an example of a conventional optical fiber assembly will be described. First, as shown in FIG. 8A, a high-temperature treatment is performed in which a part of the optical fiber 11 having a structure in which the core 12 is surrounded by the clad 13 is exposed to the flame of the burner 21. The diameter φ of the optical fiber 11 is, for example, 125 μm. The core diameter of the optical fiber 11 (MF
D; Mode Field Diameter) φc is, for example, 10 μm. Then, as shown in FIG. 8B, the temperature of the optical fiber 11 sharply increases in a short section near the middle, for example, a section of 1 mm, and the core 12 expands in the section. I do.

FIG. 9 is an enlarged view of a core bulging portion A 'of the optical fiber 500 manufactured by the high-temperature processing of FIG. 8 (the vertical direction is enlarged for convenience of illustration). The length d 'of the core bulge A' is less than 1.5 mm, for example, 1 mm. The maximum core radius h of the core bulge A '
Is, for example, 20 μm. The guided light Li that has passed through the core 52b partially passes through the clad 53a at the core bulging portion A ′.
Leaks into the light Lr, and the remaining light Lo becomes the core 52a.
Go through. Conversely, the same applies to the case where guided light is transmitted through the core 52a.

Next, as shown in FIG. 10, the optical fiber 500 is cut at a portion α (or in the vicinity thereof) where the core radius is the maximum core radius h by an optical fiber cutter C. Then, as shown in FIG.
The ferrule 31 is attached to the end of 0 'to make an optical fiber assembly 501.

[0005]

In the above-described conventional optical fiber assembly 501, the maximum core radius h at the core bulging portion A 'is h.
When is increased, the ratio of the optical axis deviation to the core diameter on the connection surface with the connection partner becomes relatively small, and the loss at the connection portion can be reduced. However, the core bulge A '
In this case, the loss due to the leaked light Lr increases. When the maximum core radius h at the core bulging portion A 'is reduced to reduce the leakage light Lr, the ratio of the optical axis deviation to the core diameter at the connection surface with the connection partner relatively increases. In addition, the loss at the connection portion increases. After all, conventionally, there is a problem that it is difficult to sufficiently reduce the transmission loss. Therefore, an object of the present invention is to provide an optical fiber that can reduce transmission loss as a whole, a method of manufacturing an optical fiber,
An object of the present invention is to provide an optical fiber assembly and a method of manufacturing the optical fiber assembly.

[0006]

According to a first aspect of the present invention, there is provided a core bulge at an intermediate portion of an optical fiber, wherein the core bulges smoothly and gradually returns to its original diameter. The length from the end of the core bulge to the portion having the maximum core radius is 1.5 mm or more, and the maximum core radius of the core bulge is 1% or less of the length. An optical fiber is provided. According to literatures and the like, when the maximum core radius of the core bulge is 1% or less of the length from the end of the core bulge to the portion having the maximum core radius, the loss at the core bulge is negligible. Turned out to be smaller. Therefore, in the optical fiber according to the first aspect, the core is smoothly expanded at a core bulging portion over a length of 1.5 mm or more, and the maximum core radius is set to 1% or less of the length. Leakage light, ie, loss, at the core bulge can be reduced by making the degree of diameter expansion relative to the distance in the optical axis direction relatively small. Also, by increasing the length, the maximum core radius at the core bulge can be made sufficiently large, which is caused by an optical axis shift when the optical fiber cut at the core bulge is connected to the connection partner. Loss can be reduced. As a result, transmission loss can be sufficiently reduced as a whole.

[0007] In a second aspect, the present invention provides a method according to the present invention, wherein a heat source is brought close to an optical fiber and the two are relatively moved along the optical axis direction of the optical fiber. The optical fiber according to the first aspect is manufactured by performing a high-temperature treatment on an intermediate portion of the optical fiber wire by relatively moving the two along the optical axis direction while moving them apart, and manufacturing the optical fiber according to the core radius. Is cut at or near a portion having a maximum core radius. In the method for manufacturing an optical fiber according to the second aspect, the two are relatively moved in the direction of the optical axis of the optical fiber while bringing the heat source close to the optical fiber, and then both are moved while moving the heat source away from the optical fiber. Since it moves relatively in the axial direction, the heat distribution in the middle of the optical fiber can be made to have the shape of a chevron with a wide skirt (a characteristic in which the temperature rises with a low gradient over a relatively wide range and falls to the original temperature). The optical fiber according to the first aspect can be suitably manufactured. Further, since the optical fiber is cut at or near the portion having the maximum core radius, an optical fiber having an end suitable for connection with the connection partner can be manufactured.

In a third aspect, the present invention provides an optical fiber obtained by cutting an optical fiber having the above configuration at or near a portion where the core radius is the maximum core radius, and a ferrule attached to an end of the optical fiber. An optical fiber assembly comprising: In the optical fiber assembly according to the third aspect, the ferrule is attached to the end of the optical fiber having the above configuration, which is convenient for connection with the connection partner.

In a fourth aspect, the present invention provides a method for cutting an optical fiber having the above structure at or near a portion where the core radius is the maximum core radius, and attaching a ferrule to an end of the optical fiber. And a method for manufacturing an optical fiber assembly, characterized in that the tip of the ferrule is polished. In the method for manufacturing an optical fiber assembly according to the fourth aspect, a ferrule is attached to the end of the optical fiber having the above-described configuration, which is convenient for connection with a connection partner. Further, since the optical fiber and the tip of the ferrule are polished, the reflected return light can be reduced, and the transmission loss can be further reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited by this. FIG. 1 is a flowchart showing an optical fiber assembly manufacturing process for manufacturing an optical fiber assembly according to one embodiment of the present invention. In step ST1, as shown in FIG.
After moving the burner 21 in the direction of the optical axis of the optical fiber 11 while bringing the flame of the burner 21 close to the middle of the optical fiber 11 having the structure surrounded by 3, the flame of the burner 21 is removed. The high-temperature processing of moving the burner 21 in the optical axis direction while moving away from 1 is repeated (a method of moving the burner 21 along a locus as shown in the drawing is called a perspective method). The flame of the burner 21 is, for example, an acetylene flame or a flame of a mixed gas of propane gas and oxygen. The movement width W of the burner 21 in the optical axis direction is, for example, about 4 mm. The diameter φ of the optical fiber 11 is, for example, 125 μm. The core diameter (MFD) φc of the optical fiber 11 is, for example, 1
0 μm. Then, as shown in FIG. 2 (b), the heat distribution of the optical fiber 11 has a wide-tailed mountain-like characteristic in the vicinity of the halfway point, and the dopant (dopant; The trace amount of impurities diffuses toward the clad 13 and the core 2 expands in diameter.

Incidentally, as shown in FIG.
(A method of moving the burner 21 along a locus as shown in FIG. 3 is called a comet method). Further, instead of moving the burner 21, the optical fiber 11 may be moved.

In step ST2, it is determined whether or not a prescribed high-temperature processing time has elapsed. If so, the process proceeds to step ST3, and if not, the process returns to step ST1.
The high-temperature processing time varies depending on the core diameter of the optical fiber element 11 and the state of the flame, but is, for example, about several minutes to several tens of minutes.

FIG. 4 is an enlarged view of the core bulging portion A of the optical fiber 100 manufactured by the above-described high-temperature treatment (the vertical direction is enlarged for convenience of illustration). In the core bulge A,
The core 2 (2a, 2b) smoothly expands its diameter and smoothly returns to its original diameter. The maximum core radius h from the end of the core bulge A
The length d up to the portion becomes 1.5 mm or more, for example, 2.5 mm. The maximum core radius h of the core bulging portion A is 1% or less of the length d, for example, 20 μm.
It is. Comparing the degree of diameter expansion of the core 2 of the core bulging portion A of the optical fiber 100 with the degree of diameter expansion of the core 52 of the core bulging portion A ′ (see FIG. 9) of the conventional optical fiber 500, If the maximum core radius h is the same, the former is smaller than the latter. Therefore, the cladding 3
The leakage light leaking to a (or the leakage light leaking from the core 2b to the cladding 3b) can be reduced as compared with the related art.

Returning to FIG. 1, in step ST3, as shown in FIG. 5, the optical fiber 100 is moved by the optical fiber cutter C so that the optical fiber 100 has the maximum core radius h (or its vicinity).
Disconnect with In step ST4, as shown in FIG.
The ferrule 31 is attached to the end of the cut optical fiber 100 ′ to form an optical fiber assembly 101. Step S
At T5, the tip of the optical fiber 100 'and the ferrule 31 are polished. Then, the optical fiber assembly manufacturing process ends.

According to the above-described optical fiber assembly manufacturing process, the core (2 in FIG.
a, 2b) is provided with a core bulge A that smoothly expands and returns to the original diameter smoothly, and the length d from the end of the core bulge A to the portion having the maximum core radius h is 1. Since it is 5 mm or more and the maximum core radius h is 1% or less of the length d, both the loss at the core bulging portion A and the loss at the connection portion can be reduced.

In the above embodiment, the high-temperature processing is performed by moving the burner 21 relative to the optical fiber 11, but the high-temperature processing may be performed in the following configuration. (1) As shown in FIG. 7, high-temperature processing may be performed by passing the optical fiber 11 through the center of the ceramic heater 41 that generates heat by the heater current i. In this case, in order to obtain a heat distribution corresponding to the core bulging portion A (see FIG. 2B),
For example, the temperature of the heating surface of the ceramic heater 41 is changed depending on the position in the optical axis direction, or the heating surface is curved with respect to the optical axis direction of the optical fiber 11. (2) High-temperature processing may be performed using a plurality of heat sources (for example, burners) arranged along the optical axis direction of the optical fiber 11. From the viewpoint of shortening the high-temperature processing time and preventing eccentricity of the core 2, it is preferable to arrange the heat source so as to sandwich the optical fiber 11 from a plurality of directions. (3) The combustion gas discharge port of the burner 21 is formed into an elliptical or rectangular shape determined so as to obtain a heat distribution corresponding to the core bulging portion A, and high-temperature processing is performed with the burner 21 fixed. Is also good. (4) The periphery of the optical fiber 11 may be covered with a ceramic heat filter so as to obtain a heat distribution corresponding to the core bulging portion A, and high-temperature treatment may be performed using an electric furnace or the like. (5) irradiating the optical fiber 11 with a laser beam through a lens for obtaining a heat distribution corresponding to the core bulging portion A,
High temperature treatment may be performed.

[0017]

According to the optical fiber, the method for manufacturing the optical fiber, the optical fiber assembly, and the method for manufacturing the optical fiber assembly of the present invention, the length of the portion where the core expands at the core bulging portion is set to 1. Since it is 5 mm or more and the upper limit of the maximum core radius is restricted to 1% of the length, both the loss caused by the leaked light at the core bulging portion and the loss caused by the optical axis shift of the connection portion are reduced. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an optical fiber assembly manufacturing process according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a trajectory of a burner and a heat distribution of an optical fiber in an optical fiber assembly manufacturing process of FIG. 1;

FIG. 3 is another explanatory diagram showing a trajectory of a burner in the optical fiber assembly manufacturing process of FIG. 1;

FIG. 4 is an enlarged view of a core bulging portion of the optical fiber according to one embodiment.

FIG. 5 is an explanatory diagram showing a state in which the optical fiber according to the embodiment is cut.

FIG. 6 is a sectional view showing an optical fiber assembly manufactured by the optical fiber assembly manufacturing process of FIG. 1;

FIG. 7 is a cross-sectional view showing a state where high-temperature processing is performed using a ceramic heater.

FIG. 8 is an explanatory view showing a high-temperature treatment and a heat distribution of an optical fiber according to a conventional optical fiber assembly manufacturing method.

FIG. 9 is an enlarged view of a core bulge portion of a conventional optical fiber.

FIG. 10 is an explanatory diagram showing a state in which a conventional optical fiber is cut.

FIG. 11 is a cross-sectional view showing an optical fiber assembly manufactured by a conventional optical fiber assembly manufacturing method.

[Explanation of symbols]

 Reference Signs List 100, 100 'Optical fiber 101 Optical fiber assembly 2, 2a, 2b, 12 Core 3, 3a, 3b, 13 Cladding 11 Optical fiber 21 Burner 31 Ferrule 41 Ceramic heater A Core bulging portion

Claims (4)

[Claims] An optical fiber has a core bulging portion at an intermediate portion of an optical fiber, wherein the core bulges smoothly and returns to its original diameter, and a maximum core radius is obtained from an end of the core bulging portion. An optical fiber, wherein the length to the portion is 1.5 mm or more and the maximum core radius of the core bulge is 1% or less of the length. 2. A method according to claim 1, further comprising: moving the heat source closer to the optical fiber while moving the heat source closer to the optical fiber while moving the heat source away from the optical fiber. The optical fiber according to claim 1 is manufactured by performing a high-temperature treatment on an intermediate portion of the optical fiber by moving relatively along the optical fiber, and the manufactured optical fiber has a core radius having a maximum core radius or a portion thereof. A method for producing an optical fiber, comprising cutting near. 3. An optical fiber obtained by cutting the optical fiber according to claim 1 at or near a portion where the core radius is the maximum core radius, and a ferrule attached to an end of the optical fiber. An optical fiber assembly characterized by the above-mentioned. 4. The optical fiber according to claim 1, wherein the optical fiber is cut at or near a portion where a core radius is the maximum core radius, a ferrule is attached to an end of the optical fiber, and the optical fiber and a tip of the ferrule. A method for manufacturing an optical fiber assembly, comprising: polishing an optical fiber assembly.