CN112823302A - Optical fiber fusion splicing method, optical fiber, and fusion splicing device - Google Patents
Optical fiber fusion splicing method, optical fiber, and fusion splicing device Download PDFInfo
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- CN112823302A CN112823302A CN201980062816.8A CN201980062816A CN112823302A CN 112823302 A CN112823302 A CN 112823302A CN 201980062816 A CN201980062816 A CN 201980062816A CN 112823302 A CN112823302 A CN 112823302A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/255—Splicing of light guides, e.g. by fusion or bonding
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Abstract
The strength of an optical fiber formed by fusion-splicing two optical fibers having different melting points is improved. The optical fiber fusion splicing method comprises the following steps: configuring a 1 st optical fiber (2) and a 2 nd optical fiber (3), the 1 st optical fiber (2) having a 1 st diameter (d1) and having a 1 st melting point, the 2 nd optical fiber (3) having a 2 nd diameter (d2) smaller than the 1 st diameter (d1) and having a 2 nd melting point higher than the 1 st melting point; heating at least the tip of the 1 st optical fiber (2) to a temperature which is not lower than the 1 st temperature at which the 1 st optical fiber (2) is softened and lower than the 2 nd temperature at which the 1 st optical fiber (2) is crystallized; moving the 2 nd optical fiber (3) in the 1 st direction approaching the 1 st optical fiber in a state that the front end of the 1 st optical fiber (2) is heated, and inserting the front end of the 2 nd optical fiber (3) into the 1 st optical fiber (2); and after the tip of the 2 nd optical fiber (3) is inserted into the 1 st optical fiber (2), moving the 2 nd optical fiber (3) in the 2 nd direction opposite to the 1 st direction.
Description
Technical Field
The present invention relates to a fusion splicing method for fusion splicing two optical fibers made of materials having different melting points at their distal ends, and an optical fiber manufactured by fusion splicing two optical fibers made of different materials using the fusion splicing method.
Background
When an optical system such as an optical circuit is formed of an optical fiber, it is necessary to connect optical fibers made of different materials to the tip. The connection of optical fibers is generally performed by fusion splicing.
Optical fibers have different physical properties depending on their materials. For example, quartz used in a general optical fiber has a melting point higher than that of a material other than quartz (for example, fluoride glass).
As a method for connecting such optical fibers of different types of materials having different melting points, the following methods are known: an optical fiber having a high melting point is made smaller in diameter than an optical fiber having a low melting point, and the two optical fibers are fused by heating and pressing the optical fiber having a high melting point against the optical fiber having a low melting point (see, for example, patent document 1).
In this fusion splicing method, the low-melting-point optical fiber is softened by heat after heating the high-melting-point optical fiber, and fusion splicing is performed in a state where the tip of the high-melting-point optical fiber is inserted into the tip of the low-melting-point optical fiber, thereby increasing the strength of the fusion-spliced portion.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2003-156652
Disclosure of Invention
Problems to be solved by the invention
However, the fusion-bonding strength of the optical fiber fusion-bonded by the above fusion-bonding method is about 80kPa, and it is not sufficient to construct an optical system using the optical fiber. This is because, with such a degree of fusion splice strength, there is a high possibility that the fusion splice of the optical fibers is released when handling the optical fibers.
In addition, it is considered that the optical fiber fusion-spliced by the fusion-splicing method is easily damaged by bending or the like.
Specifically, in the optical fiber fusion spliced by the above fusion splicing method, a step portion having a diameter that changes abruptly is formed at the connection portion. For example, when an optical fiber having such a step portion is bent, stress concentrates on the step portion, and the optical fiber at or near the step portion may be damaged.
The invention aims to improve the strength of an optical fiber formed by fusion-splicing two optical fibers having different melting points.
Means for solving the problems
Hereinafter, a plurality of embodiments will be described as means for solving the problem. These means can be combined arbitrarily as needed.
An optical fiber fusion splicing method according to an embodiment of the present invention is a method for fusion splicing a 1 st optical fiber having a 1 st melting point and a 2 nd optical fiber having a 2 nd melting point higher than the 1 st melting point. The welding method has the following steps.
The 1 st optical fiber having the 1 st diameter and the 2 nd optical fiber having the 2 nd diameter smaller than the 1 st diameter are arranged.
The tip of the 1 st optical fiber is heated to at least the 1 st temperature at which the 1 st optical fiber is softened and a temperature lower than the 2 nd temperature at which the 1 st optical fiber is crystallized.
The 2 nd optical fiber is moved in the 1 st direction close to the 1 st optical fiber in a state where at least the tip of the 1 st optical fiber is heated, and the tip of the 2 nd optical fiber is inserted into the 1 st optical fiber.
After the tip of the 2 nd optical fiber is inserted into the 1 st optical fiber, the 2 nd optical fiber is moved in the 2 nd direction opposite to the 1 st direction.
In the optical fiber fusion splicing method, after the 1 st optical fiber is softened and the tip of the 2 nd optical fiber is inserted into the 1 st optical fiber, the 2 nd optical fiber is further moved in the 2 nd direction opposite to the 1 st direction in which the tip of the 2 nd optical fiber is inserted into the 1 st optical fiber. That is, the 2 nd optical fiber is moved in a direction away from the 1 st optical fiber.
Thus, when the 2 nd optical fiber is moved in a direction away from the 1 st optical fiber, the tip portion of the 1 st optical fiber on the side connected to the 2 nd optical fiber is pulled. By this drawing, the diameter of the tip portion of the 1 st optical fiber is reduced, and the connection portion between the 1 st optical fiber and the 2 nd optical fiber is tapered.
In this way, the strength of the optical fiber manufactured by connecting the 1 st optical fiber and the 2 nd optical fiber can be improved by forming the connecting portion of the two optical fibers into a tapered shape. For example, when the manufactured optical fiber is bent, stress can be made less likely to concentrate on the connecting portion of the two optical fibers, and thus strength can be improved.
Further, by heating at least the leading end of the 1 st optical fiber having a low melting point, when the 2 nd optical fiber is moved in a direction away from the 1 st optical fiber, the connecting portion is easily tapered.
The welding method may further include the steps of: after moving the 2 nd fiber in the 2 nd direction, the 1 st and 2 nd fibers are gradually cooled.
Thus, when the 1 st optical fiber and the 2 nd optical fiber are cooled, it is possible to suppress the occurrence of stress and breakage at the connecting portion of the two optical fibers due to the difference in the expansion coefficients of the two optical fibers.
In the step of inserting the distal end of the 2 nd optical fiber into the 1 st optical fiber, the insertion distance of the distal end of the 2 nd optical fiber into the 1 st optical fiber may be a distance in the range of 20% to 40% of the 2 nd diameter.
Thus, the insertion depth of the tip of the 2 nd optical fiber into the 1 st optical fiber is set to an appropriate depth, and the two optical fibers can be connected with a sufficiently strong fusion splice strength.
In the step of moving the 2 nd optical fiber in the 2 nd direction, the moving distance of the 2 nd optical fiber may be a distance in a range of 50% to 70% of the 2 nd diameter.
Thus, the taper angle of the 1 st optical fiber tip can be set to an appropriate angle at which stress is not easily concentrated on the connection portion between the 1 st optical fiber and the 2 nd optical fiber.
In the step of disposing the 1 st optical fiber and the 2 nd optical fiber, the tip of the 1 st optical fiber and the tip of the 2 nd optical fiber may be disposed in proximity to each other.
This enables heating not only the tip of the 1 st optical fiber but also the tip of the 2 nd optical fiber. As a result, when the 2 nd optical fiber and the 1 st optical fiber are brought into contact with each other, the temperature decrease of the 1 st optical fiber can be suppressed.
It is also possible that the 1 st diameter is in the range of 1.5 to 3 times the 2 nd diameter. This allows the 1 st optical fiber and the 2 nd optical fiber to be connected with sufficient strength.
The 1 st temperature may be a softening point of the 1 st optical fiber. This can reliably soften the 1 st optical fiber, and can reliably perform insertion of the distal end of the 2 nd optical fiber and formation of the tapered shape.
The 2 nd temperature may be a crystallization temperature of the 1 st optical fiber. This can reliably prevent the 1 st optical fiber from being crystallized to lower the transparency of the 1 st optical fiber. As a result, the fusion-splicing loss at the fusion-spliced portion between the 1 st optical fiber and the 2 nd optical fiber can be reduced.
Alternatively, the 1 st optical fiber may be a fluoride optical fiber. Thus, the optical fiber in which the 1 st optical fiber and the 2 nd optical fiber are connected can be applied to a fiber laser, a fiber amplifier, and the like.
The 2 nd optical fiber may be a quartz optical fiber. Thus, the optical fiber in which the 1 st optical fiber and the 2 nd optical fiber are connected can be applied to a fiber laser, a fiber amplifier, a fiber sensor, a transmission fiber, and the like.
Another embodiment of the present invention provides an optical fiber including a 1 st optical fiber and a 2 nd optical fiber.
The 1 st optical fiber has a tapered portion. The tapered portion is a portion whose diameter decreases from the 1 st diameter toward the leading end.
The 2 nd optical fiber has a 2 nd diameter smaller than the 1 st diameter. The 2 nd optical fiber is connected to the 1 st optical fiber in a state where the distal end is inserted into the distal end of the tapered portion.
In the optical fiber formed by connecting the 1 st optical fiber and the 2 nd optical fiber, the connecting part of the 1 st optical fiber and the 2 nd optical fiber is in a conical shape, so that the strength of the optical fiber can be improved. For example, when the optical fiber is bent, stress can be made less likely to concentrate on the connecting portion of the two optical fibers.
The insertion depth of the tip of the 2 nd optical fiber into the taper portion of the 1 st optical fiber may be in the range of 4% to 16% of the 2 nd diameter.
This allows the 1 st optical fiber and the 2 nd optical fiber to be connected with a sufficiently strong fusion splice strength.
The taper angle formed by the side surface of the tapered portion and the longitudinal direction of the 1 st optical fiber may be in the range of 20 degrees to 50 degrees.
This makes it possible to form the tapered portion into an optimal shape in which stress is not easily concentrated on the connection portion between the 1 st optical fiber and the 2 nd optical fiber.
It is also possible that the 1 st diameter is in the range of 1.5 to 3 times the 2 nd diameter. This allows the 1 st optical fiber and the 2 nd optical fiber to be connected with sufficient strength.
The 1 st diameter may be 2 times the 2 nd diameter, and a taper angle formed by a side surface of the tapered portion and a longitudinal direction of the 1 st optical fiber may be in a range of 22 degrees to 30 degrees.
The 1 st diameter may be 3 times the 2 nd diameter, and a taper angle formed by a side surface of the tapered portion and a longitudinal direction of the 1 st optical fiber may be in a range of 35 degrees to 50 degrees.
Thus, by setting the taper angle in an appropriate range according to the ratio of the 1 st diameter to the 2 nd diameter, the taper portion can be formed into an optimum shape in which stress is not easily concentrated on the connection portion of the 1 st optical fiber and the 2 nd optical fiber.
Alternatively, the 1 st optical fiber may be a fluoride optical fiber. Thus, the optical fiber in which the 1 st optical fiber and the 2 nd optical fiber are connected can be applied to a fiber laser, a fiber amplifier, and the like.
The 2 nd optical fiber may be a quartz optical fiber. Thus, the optical fiber in which the 1 st optical fiber and the 2 nd optical fiber are connected can be applied to a fiber laser, a fiber amplifier, a fiber sensor, a transmission fiber, and the like.
A fusion splicing device according to another aspect of the present invention is a fusion splicing device for fusion splicing a 1 st optical fiber having a 1 st melting point and a 2 nd optical fiber having a 2 nd melting point higher than the 1 st melting point. The fusion apparatus has a heating light source and an optical fiber moving device.
The heating light source heats the tip of a 1 st optical fiber having a 1 st diameter to a temperature which is not lower than the 1 st temperature at which the 1 st optical fiber is softened and lower than the 2 nd temperature at which the 1 st optical fiber is crystallized.
The optical fiber moving device moves a 2 nd optical fiber having a 2 nd diameter smaller than the 1 st diameter in a 1 st direction approaching the 1 st optical fiber in a state where at least a tip of the 1 st optical fiber is heated, inserts the tip of the 2 nd optical fiber into the 1 st optical fiber, and then moves the 2 nd optical fiber in a 2 nd direction opposite to the 1 st direction.
In the above-described fusion splicer, after the 1 st optical fiber is softened and the distal end of the 2 nd optical fiber is inserted into the 1 st optical fiber, the 2 nd optical fiber is further moved in the 2 nd direction opposite to the 1 st direction in which the distal end of the 2 nd optical fiber is inserted into the 1 st optical fiber. That is, the 2 nd optical fiber is moved in a direction away from the 1 st optical fiber.
Thus, when the 2 nd optical fiber is moved in a direction away from the 1 st optical fiber, the tip portion of the 1 st optical fiber on the side connected to the 2 nd optical fiber is pulled. By this drawing, the diameter of the tip portion of the 1 st optical fiber is reduced, and the connection portion between the 1 st optical fiber and the 2 nd optical fiber is tapered.
In this way, the strength of the optical fiber manufactured by connecting the 1 st optical fiber and the 2 nd optical fiber can be improved by forming the connecting portion of the two optical fibers into a tapered shape. For example, when the manufactured optical fiber is bent, stress can be made less likely to concentrate on the connecting portion of the two optical fibers, and thus strength can be improved.
Further, by heating at least the leading end of the 1 st optical fiber having a low melting point, when the 2 nd optical fiber is moved in a direction away from the 1 st optical fiber, the connecting portion is easily tapered.
Effects of the invention
By forming the tapered shape in the connecting portion of the two optical fibers, the strength of the optical fiber manufactured by connecting the two optical fibers can be improved.
Drawings
Fig. 1 is a diagram showing the configuration of an optical fiber manufactured by fusion splicing.
Fig. 2 is a diagram showing the entire structure of the welding apparatus.
Fig. 3 is a diagram showing the structure of the light ray moving device.
Fig. 4 is a diagram schematically illustrating a fusion splicing method of optical fibers.
Fig. 5 is a view showing an optical microscopic image of the optical fiber of example 1.
Fig. 6 is a diagram showing an optical microscopic image of the optical fiber of example 2.
Fig. 7 is a graph showing the relationship between the taper angle and the fusion loss of the optical fiber of example 1.
Fig. 8 is a graph showing the relationship between the taper angle and the fusion loss of the optical fiber of example 2.
Fig. 9 is a view showing a transmission optical microscopic image of the optical fiber manufactured in comparative example 1.
Fig. 10 is a view showing an optical microscopic image of the optical fiber of comparative example 2.
Detailed Description
1. Embodiment 1
(1) Optical fiber
The method for fusion splicing optical fibers according to embodiment 1 will be described below.
First, the structure of the optical fiber 1 manufactured by the fusion splicing method according to the present embodiment will be described with reference to fig. 1. Fig. 1 is a diagram showing the configuration of an optical fiber manufactured by fusion splicing.
As shown in fig. 1, the optical fiber 1 has a 1 st optical fiber 2 and a 2 nd optical fiber 3. The 1 st optical fiber 2 and the 2 nd optical fiber 3 are fusion-spliced to each other at the tip portions by the fusion-splicing method of the present embodiment.
The 1 st optical fiber 2 is an optical fiber composed of a material having a 1 st melting point. In the present embodiment, the 1 st optical fiber 2 is a fluoride (ZBLAN) fiber. The 1 st melting point is the softening point of the fluoride fiber, i.e., about 300 degrees. When the 1 st optical fiber 2 is a fluoride optical fiber, the melting point is about 440 degrees, the crystallization point is about 350 degrees, and the glass transition point is about 260 degrees. The fluoride fiber is often used as a laser medium for fiber lasers.
The core of the 1 st optical fiber 2, which is a fluoride optical fiber, may be doped with an element such as erbium (Er).
In addition, aluminum fluoride, chalcogenide based glasses (e.g., arsenic trisulfide (As)), can be used2S3)、Ge33As12Se55Etc.), a glass fiber made of tellurite (TeO) based glass or the like is used as the 1 st optical fiber 2. These glasses also have a melting point lower than that of quartz, which is a material of the 2 nd optical fiber 3 described later.
In addition, the 1 st optical fiber 2 has a circular cross section perpendicular to the longitudinal direction and has a 1 st diameter d 1. The 1 st optical fiber 2 has a tapered portion 21 at a connection portion with the 2 nd optical fiber 3, i.e., a leading end.
The diameter of the conical portion 21 decreases from the 1 st diameter d1 toward the front end. The diameter of the tapered portion 21 at the connection portion with the 2 nd optical fiber 3, i.e., the tip, is substantially the same as the diameter of the 2 nd optical fiber 3 (the 2 nd diameter d 2).
As described later, the optimum value of the taper angle θ of the tapered portion 21 varies depending on the ratio of the 1 st diameter d1 to the 2 nd diameter d2, but is set to an angular range of 20 degrees to 50 degrees. In the present embodiment, the taper angle θ is defined as an angle formed by the side surface of the tapered portion 21 and the longitudinal direction of the 1 st optical fiber 2.
The 2 nd optical fiber 3 is an optical fiber composed of a material having a 2 nd melting point. In the present embodiment, the 2 nd optical fiber 3 is a quartz optical fiber. The 2 nd melting point is the melting point of quartz, i.e., about 1700 degrees.
The cross section of the 2 nd optical fiber 3 perpendicular to the longitudinal direction is a circle having a 2 nd diameter d 2. In the present embodiment, the 2 nd diameter d2 is smaller than the 1 st diameter d 1. Specifically, the 1 st diameter d1 can be set to be in the range of 1.5 to 3 times the 2 nd diameter d 2.
Thus, the 1 st optical fiber 2 and the 2 nd optical fiber 3 can be connected with sufficient strength by a fusion splicing method described later.
The 2 nd optical fiber 3 is fusion-spliced to the 1 st optical fiber 2 in a state where the tip thereof is inserted into the tip of the tapered portion 21 of the 1 st optical fiber 2. The insertion depth of the tip of the 2 nd optical fiber 3 into the tapered portion 21 can be set to a range of 4% to 16% of the 2 nd diameter d 2. For example, when the 2 nd diameter d2 of the 2 nd optical fiber 3 is 125 μm, the insertion depth can be set to a range of 5 μm to 20 μm.
By having the above-described structure, the optical fiber 1 manufactured by fusion-splicing the 1 st optical fiber 2 and the 2 nd optical fiber 3 is not easily separated from the 1 st optical fiber 2 at the time of handling, and is not easily broken at the time of bending.
Specifically, the 1 st optical fiber 2 and the 2 nd optical fiber 3 can be connected with a sufficiently strong fusion-splicing strength by inserting the distal end of the 2 nd optical fiber 3 into the distal end of the tapered portion 21 of the 1 st optical fiber 2 by the depth in the above range.
Further, by providing the tapered portion 21 having the taper angle θ at the connection portion between the 1 st optical fiber 2 and the 2 nd optical fiber 3, stress can be made less likely to concentrate on the connection portion between the two optical fibers when, for example, the optical fiber 1 is bent.
The optical fiber 1 in which two optical fibers made of different materials are fusion-spliced can be applied to, for example, a fiber laser, a fiber amplifier, a fiber sensor, a transmission fiber, and the like, depending on the material of the 1 st optical fiber 2.
(2) Welding device
Next, the welding apparatus 100 will be described with reference to fig. 2 and 3. Fig. 2 is a diagram showing the entire structure of the welding apparatus. Fig. 3 is a diagram showing the structure of the optical fiber moving apparatus.
The fusion splicing apparatus 100 of the present embodiment irradiates the heating laser HL to heat and soften the 1 st optical fiber 2 having a low melting point, and presses the 2 nd optical fiber 3 against the softened 1 st optical fiber 2 to perform fusion splicing.
The fusion splicing apparatus 100 mainly includes an optical fiber moving device 4, a heating light source 6, and a shutter 8.
(2-1) optical fiber moving device
The optical fiber moving device 4 is a device for moving the 1 st optical fiber 2 and/or the 2 nd optical fiber 3 in the 1 st direction (fig. 3) and the 2 nd direction (fig. 3) opposite thereto. Specifically, the optical fiber moving device 4 includes the 1 st moving unit 41 and the 2 nd moving unit 43.
The 1 st direction is defined as a direction parallel to the lengthwise direction of the 1 st optical fiber 2 and approaching the 1 st optical fiber 2. On the other hand, the 2 nd direction is defined as a direction parallel to the lengthwise direction of the 1 st optical fiber 2 and away from the 1 st optical fiber 2.
The 1 st moving part 41 moves the 1 st optical fiber 2 in the 1 st direction or the 2 nd direction. The 1 st moving unit 41 includes a 1 st moving table 41a and a 1 st holding unit 41 b.
The 1 st moving table 41a is a table that can move in the 1 st direction or the 2 nd direction. The 1 st moving table 41a is, for example, an X-Y table. By allowing the 1 st moving table 41a to move two-dimensionally, the 1 st optical fiber 2 can be aligned with high accuracy at its distal end. The 1 st movement table 41a can be controlled to move in units of μm with high accuracy by, for example, a piezoelectric element or the like.
The 1 st holding portion 41b holds the 1 st optical fiber 2. The 1 st holding portion 41b is a clamp for an optical fiber for holding the 1 st optical fiber 2 by pressing it against the bottom of the V-shaped groove with a screw or the like, for example.
The 1 st holding portion 41b is fixed to an upper portion of the 1 st moving table 41a, and moves in the 1 st direction or the 2 nd direction in accordance with the movement of the 1 st moving table 41 a.
The 2 nd moving part 43 moves the 2 nd optical fiber 3 in the 1 st direction or the 2 nd direction. The 2 nd moving unit 43 has a 2 nd moving table 43a and a 2 nd holding unit 43 b.
The structure and function of the 2 nd moving table 43a and the 2 nd holding portion 43b are the same as those of the 1 st moving table 41a and the 1 st holding portion 41b, respectively, and therefore, the description thereof is omitted here.
(2-2) heating light Source
The heating light source 6 is a light source that outputs a heating laser HL. As the heating light source 6, for example, CO that outputs infrared light can be used2A laser light source. Heating ofThe light source 6 can control the intensity of the heating laser HL with high accuracy.
The heating laser light HL output from the heating light source 6 is redirected by the 1 st mirror 61 and enters the light branching member 62 (e.g., half mirror). The heating laser light HL incident on the light branching member 62 is branched in 2 directions.
One of the heating laser beams HL branched by the optical branching member 62 is changed in path by a 2 nd mirror 63, and reaches a position where the tips of the 1 st optical fiber 2 and the 2 nd optical fiber 3 are arranged from a predetermined one direction.
The one heating laser beam HL is focused at a position (or a vicinity thereof) where the distal ends of the 1 st optical fiber 2 and the 2 nd optical fiber 3 are arranged by the 1 st lens 64.
The other side of the heating laser beam HL branched by the optical branching member 62 is changed in path by the 3 rd mirror 65, and reaches the position where the tip ends of the 1 st optical fiber 2 and the 2 nd optical fiber 3 are arranged from the direction opposite to the above-described predetermined one direction.
The other heating laser beam HL is focused at a position (or its vicinity) where the tips of the 1 st optical fiber 2 and the 2 nd optical fiber 3 are arranged by the 2 nd lens 66.
In this way, by irradiating the heating laser HL to the leading ends of the 1 st optical fiber 2 and the 2 nd optical fiber 3 from two directions opposite to each other, the leading ends of the 1 st optical fiber 2 and the 2 nd optical fiber 3 can be uniformly heated.
The irradiation diameter (diameter) of the heating laser HL irradiated to the 1 st optical fiber 2 and the 2 nd optical fiber 3 is preferably sufficiently larger than the diameter of the 1 st optical fiber 2. For example, the irradiation diameter of the heating laser HL can be set to about several hundred μm.
(2-3) shutter
The shutter 8 is disposed on or near the optical path of the heating laser light HL from the heating light source 6 to the light branching member 62. In the present embodiment, as shown in fig. 2, the shutter 8 is disposed between the heating light source 6 and the 1 st reflecting mirror 61.
When the shutter 8 is disposed on the optical path of the heating laser light HL, the heating laser light HL is blocked by the shutter 8, and the heating of the leading ends of the 1 st optical fiber 2 and the 2 nd optical fiber 3 is stopped.
On the other hand, when the shutter 8 is away from the optical path of the heating laser light HL, the heating laser light HL reaches the leading ends of the 1 st and 2 nd optical fibers 2 and 3, thereby heating the leading ends.
That is, the shutter 8 controls execution and stop of heating of the leading ends of the 1 st and 2 nd optical fibers 2 and 3. By controlling the execution and stop of heating by the shutter 8, the heating of the leading end of the optical fiber can be performed for a short time.
The welding apparatus 100 further includes a control unit, not shown. The control unit is a computer system having a CPU, a storage device (such as RAM or ROM), and various interfaces, and controls each unit of the welding apparatus 100. Specifically, the control unit controls the optical fiber moving device 4, the heating light source 6, and the shutter 8.
The control unit may control the respective units of the welding apparatus 100 by a program stored in a storage device of a computer system constituting the control unit.
(2-4) Structure for monitoring weld status and the like
The fusion splicing device 100 has a structure for monitoring the fusion splicing state of the 1 st optical fiber 2 and the 2 nd optical fiber 3.
Specifically, the welding apparatus 100 includes a pair of cameras 10. The camera 10 acquires the arrangement state of the 1 st optical fiber 2 and the 2 nd optical fiber 3, the fusion-splicing process of these optical fibers, and the fusion-spliced state of the optical fibers based on visual information (for example, a moving image or a still image).
The pair of cameras 10 acquire the states of the 1 st optical fiber 2 and the 2 nd optical fiber 3 from two directions in which the heating laser light HL is irradiated.
The fusion splicing device 100 is configured to measure the light transmittance of the optical fiber 1 manufactured by fusion splicing the 1 st optical fiber 2 and the 2 nd optical fiber 3. Specifically, welding apparatus 100 includes inspection light source 12 and light receiving device 14.
The inspection light source 12 outputs inspection light IL incident from the 2 nd optical fiber 3 side of the optical fiber 1. The inspection light source 12 is, for example, a laser diode.
The light receiving device 14 measures the intensity of the inspection light IL propagating through the 1 st optical fiber 2 and the 2 nd optical fiber 3. The light receiving device 14 is, for example, a power meter that measures the intensity of the inspection light IL.
In the above configuration, the transmittance of light of the optical fiber 1 can be calculated from the ratio of the intensity of the inspection light IL output from the inspection light source 12 to the intensity of the inspection light IL measured by the light receiving device 14.
When the light transmittance of the optical fiber 1 is low, it means that the loss due to fusion-splicing of the 1 st optical fiber 2 and the 2 nd optical fiber 3 is large, and it can be determined that the connection of these two optical fibers is not appropriate.
In some cases, when the connection between the two optical fibers is not appropriate, the front end of the 1 st optical fiber 2 is crystallized to lower the transparency, and as a result, the light transmittance of the optical fiber 1 is lowered. In this case, since the temperature of the 1 st optical fiber 2 is not lower than the crystallization temperature for a long time, it can be estimated that the connection is not appropriate.
Further, when the fusion splicing of the 1 st optical fiber 2 and the 2 nd optical fiber 3 is released by stress during heating and slow cooling, there is a possibility that the transmittance of the optical fiber 1 is lowered when optical coupling loss occurs due to a defective shape of the fusion-spliced portion of these optical fibers, when foreign matter is mixed into the fusion-spliced surface, or the like. In such a case, it can be estimated that the fusion connection is not appropriate.
(3) Method for fusion splicing optical fibers
Hereinafter, a method of fusion splicing optical fibers according to embodiment 1 will be described with reference to fig. 4. Fig. 4 is a diagram schematically illustrating a fusion splicing method of optical fibers. Hereinafter, a method of fusion-splicing two optical fibers having different melting points will be described using a process of fusion-splicing the 1 st optical fiber 2 and the 2 nd optical fiber 3 to manufacture the optical fiber 1 shown in fig. 1.
First, the 1 st optical fiber 2 and the 2 nd optical fiber 3 are arranged in the fusion-splicing device 100.
Specifically, first, the 1 st optical fiber 2 is held by the 1 st holding portion 41b, and the 2 nd optical fiber 3 is held by the 2 nd holding portion 43 b.
Then, the 1 st optical fiber 2 and/or the 2 nd optical fiber 3 are moved by the 1 st movement stage 41a and/or the 2 nd movement stage 43a, and the 1 st optical fiber 2 and the 2 nd optical fiber 3 are aligned. For example, as shown in fig. 4 a, alignment is performed so that the centerline of the 1 st optical fiber 2 (the line indicated by the broken line in fig. 4 a) coincides with the centerline of the 2 nd optical fiber 3.
Next, the 1 st optical fiber 2 and/or the 2 nd optical fiber 3 are moved by the 1 st movement stage 41a and/or the 2 nd movement stage 43a, and the leading end of the 1 st optical fiber 2 and the leading end of the 2 nd optical fiber 3 are brought close to each other.
After the 1 st optical fiber 2 and the 2 nd optical fiber 3 are arranged in the fusion-splicing device 100, the heating laser light HL is output from the heating light source 6, and the heating laser light HL is irradiated to the tip portion of the 1 st optical fiber 2 by separating the shutter 8 from the optical path of the heating laser light HL, as shown in fig. 4 (B). In fig. 3, the irradiation region of the heating laser HL is indicated by a dashed circle.
As described above, since the tip of the 1 st optical fiber 2 and the tip of the 2 nd optical fiber 3 are disposed close to each other, the heating laser light HL is irradiated to both the tip of the 1 st optical fiber 2 and the tip of the 2 nd optical fiber 3. As a result, not only the tip portion of the 1 st optical fiber 2 but also the tip portion of the 2 nd optical fiber 3 is heated.
By heating both the tip portion of the 1 st optical fiber 2 and the tip portion of the 2 nd optical fiber 3, the 2 nd optical fiber 3 absorbs heat of the 1 st optical fiber 2 when the 2 nd optical fiber 3 comes into contact with the heated 1 st optical fiber 2 in a step of moving the 2 nd optical fiber 3 in the 1 st direction, which will be described later, and a temperature drop of the 1 st optical fiber 2 can be suppressed.
While the intensity of the heating laser beam HL output from the heating light source 6 is adjusted to a predetermined intensity, the heating laser beam HL is irradiated to the tip of the 1 st optical fiber 2 and the tip of the 2 nd optical fiber 3 for several seconds.
Thereby, the tip portion of the 1 st optical fiber 2 is heated to a temperature not lower than the 1 st temperature at which the 1 st optical fiber 2 is softened and lower than the 2 nd temperature at which the 1 st optical fiber 2 is crystallized.
The 1 st temperature is a softening point of the 1 st optical fiber 2. The 2 nd temperature is the crystallization temperature of the 1 st optical fiber 2. For example, in the case where the 1 st optical fiber 2 is fluoride glass, the 1 st temperature is about 300 ℃ and the 2 nd temperature is about 370 ℃.
By setting the leading end portion of the 1 st optical fiber 2 in the above temperature range, the 1 st optical fiber can be reliably softened, and the 1 st optical fiber 2 can be reliably prevented from being crystallized and from being lowered in transparency. As a result, fusion splicing of the 1 st optical fiber 2 and the 2 nd optical fiber 3 can be reliably performed, and fusion loss at the fusion spliced portion can be reduced.
In addition, the 2 nd optical fiber 3 does not soften at a temperature within the range of the 1 st temperature to the 2 nd temperature described above.
By irradiating the heating laser HL, the tip portions of the 1 st optical fiber 2 and the 2 nd optical fiber 3 are heated, the tip portion of the 1 st optical fiber 2 is maintained in the above temperature range, and as shown in fig. 4 (C), the 2 nd optical fiber 3 is moved in the 1 st direction with respect to the 1 st optical fiber 2, and the tip portion of the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2.
That is, the 2 nd optical fiber 3 is moved in a direction approaching the 1 st optical fiber 2, and the tip portion of the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2.
At this time, the 1 st optical fiber 2 is moved in the 2 nd direction by the 1 st moving portion 41, and the 2 nd optical fiber 3 is moved in the 1 st direction by the 2 nd moving portion 43, so that the 2 nd optical fiber 3 is moved in the 1 st direction relative to the 1 st optical fiber 2.
In the above step, the insertion distance of the tip of the 2 nd optical fiber 3 into the 1 st optical fiber 2 is preferably a distance in the range of 20% to 40% of the 2 nd diameter d2, more preferably a distance in the range of 25% to 35% of the 2 nd diameter d2, and most preferably a distance of 32% of the 2 nd diameter d 2.
For example, when the 2 nd diameter d2 is 125 μm, the insertion distance of the tip of the 2 nd optical fiber 3 into the 1 st optical fiber 2 is preferably 25 μm to 50 μm, more preferably 30 μm to 45 μm, and most preferably 40 μm.
This makes it possible to set the insertion depth of the distal end of the 2 nd optical fiber 3 into the 1 st optical fiber 2 to an appropriate depth, and to connect the two optical fibers with a sufficiently strong fusion splice strength.
The speed when the 2 nd optical fiber 3 is moved in the 1 st direction is, for example, about several tens μm per second.
When the tip of the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2, the 2 nd optical fiber 3 is pushed into the 1 st optical fiber 2, and therefore, as shown in fig. 4 (C), the tip of the 1 st optical fiber 2 is slightly expanded.
As shown in fig. 4C, in a state where the tip of the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2, the boundary portion (connection portion) between the 1 st optical fiber 2 and the 2 nd optical fiber 3 has a stepped shape.
When the optical fibers are cooled in a state where the connection portion of the 1 st optical fiber 2 and the 2 nd optical fiber 3 becomes a step shape, the connection portion of the 1 st optical fiber 2 and the 2 nd optical fiber 3 maintains the step shape, and the two optical fibers are connected. Such a step-shaped connecting portion is easily damaged by stress concentration when the optical fiber is bent.
Therefore, in the present embodiment, the 1 st optical fiber 2 and the 2 nd optical fiber 3 are formed in a tapered shape having a stronger strength than the stepped shape. Specifically, as described below, the connecting portion is formed in a tapered shape.
First, as shown in fig. 4 (C), the heating laser HL is irradiated for several seconds while the distal end of the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2.
Then, the heating laser HL continues to be irradiated, and the 2 nd optical fiber 3 is moved in the 2 nd direction. That is, the 2 nd optical fiber 3 is moved in a direction away from the 1 st optical fiber 2.
At this time, the 1 st optical fiber 2 is moved in the 1 st direction by the 1 st moving portion 41, and the 2 nd optical fiber 3 is moved in the 2 nd direction by the 2 nd moving portion 43, so that the 2 nd optical fiber 3 is moved in the 2 nd direction relative to the 1 st optical fiber 2.
In the above step, the tip portion of the 1 st optical fiber 2 on the side connected to the 2 nd optical fiber 3 moves together with the 2 nd optical fiber 3 moving in the 2 nd direction in a state where the tip portion is attached to the tip of the 2 nd optical fiber 3 by surface tension. As a result, the tip portion of the 1 st optical fiber 2 is pulled by the 2 nd optical fiber 3 moving in the 2 nd direction.
By this drawing, the diameter of the leading end of the 1 st optical fiber 2 on the side connected to the 2 nd optical fiber 3 is reduced from the 1 st diameter d1 and is substantially the same as the 2 nd diameter d 2. As a result, as shown in fig. 4 (D), the connecting portion between the 1 st optical fiber 2 and the 2 nd optical fiber 3 has a tapered shape.
As described above, in the present embodiment, the leading end portion of the low melting point 1 st optical fiber 2 is heated. Accordingly, since the viscosity of the 1 st optical fiber 2 on the side to be drawn is low, when the 2 nd optical fiber 3 is moved in a direction away from the 1 st optical fiber 2, a tapered shape is easily formed at the connection portion between the 1 st optical fiber 2 and the 2 nd optical fiber 3.
In the above step, the moving distance of the 2 nd optical fiber 3 in the 2 nd direction is preferably in the range of 50% to 70% of the 2 nd diameter d2, more preferably in the range of 55% to 65% of the 2 nd diameter d2, and most preferably in the range of 64% of the 2 nd diameter d 2.
For example, when the 2 nd diameter d2 is 125 μm, the moving distance of the 2 nd optical fiber 3 in the 2 nd direction is preferably 62 to 88 μm, more preferably 68 to 82 μm, and most preferably 80 μm.
Thus, the taper angle θ of the tip of the 1 st optical fiber 2 can be set to an appropriate angle at which stress is not easily concentrated on the connecting portion between the 1 st optical fiber 2 and the 2 nd optical fiber 3.
The moving speed of the 2 nd optical fiber 3 when the tapered shape is formed is, for example, about several tens μm per second.
After the tip portion of the 1 st optical fiber 2 is drawn by moving the 2 nd optical fiber 3 in the 2 nd direction and the tapered shape is formed at the connection portion, as shown in fig. 4 (E), the irradiation of the heating laser HL is stopped, and the 1 st optical fiber 2 and the 2 nd optical fiber 3 are cooled, thereby connecting the 1 st optical fiber 2 and the 2 nd optical fiber 3.
In the present embodiment, the intensity of the heating laser HL is gradually decreased to 0 for about several tens of seconds to several minutes, and the 1 st optical fiber 2 and the 2 nd optical fiber 3 are gradually cooled.
Generally, there is a large difference in thermal expansion coefficient between the 1 st optical fiber 2 having a low melting point and the 2 nd optical fiber 3 having a high melting point. For example, the fluoride glass used for the 1 st optical fiber 2 has a coefficient of expansion of 20X 10-6K, whereas the expansion coefficient of the silica used for the 2 nd optical fiber 3 is 0.55X 10-6There is a nearly 40-fold difference in/K.
Therefore, when the 1 st optical fiber 2 and the 2 nd optical fiber 3 are rapidly cooled, stress is generated at the connection portion of the 1 st optical fiber 2 and the 2 nd optical fiber 3 due to the difference in the thermal expansion coefficient, and the connection portion may be broken during cooling.
Therefore, as described above, by gradually cooling the 1 st optical fiber 2 and the 2 nd optical fiber 3 in several tens of seconds to several minutes, it is possible to suppress the occurrence of stress at the connection portion of the 1 st optical fiber and the 2 nd optical fiber due to the difference in the expansion coefficient between the two optical fibers and the breakage.
(4) Examples of the embodiments
In order to confirm whether or not a strong fusion-spliced connection can be achieved by the above-described fusion-splicing method for optical fibers, two optical fibers are actually fusion-spliced by the above-described fusion-splicing method to manufacture the optical fiber 1. An example of the production of the optical fiber 1 will be described below.
In the following examples, an optical fiber made of fluoride glass was used as the low melting point 1 st optical fiber 2. On the other hand, a light beam made of quartz is used as the high melting point 2 nd optical fiber 3.
The 2 nd diameter d2 of the 2 nd optical fiber 3 was set to 125 μm (core diameter: 100 μm, cladding diameter: 125 μm).
On the other hand, the 1 st diameter d1 of the 1 st optical fiber 2 was set to two kinds of 240 μm (core diameter: 170 μm, clad diameter: 240 μm) and 330 μm (core diameter: 280 μm, clad diameter: 330 μm). That is, the 1 st diameter d1 is set to 1.9 times and 2.6 times the 2 nd diameter d 2.
Hereinafter, the example having the 1 st diameter d1 of 240 μm will be referred to as "example 1", and the example having the 1 st diameter d1 of 330 μm will be referred to as "example 2".
In the present embodiment, in order to examine the strength of fusion splicing, a tensile load was applied to the optical fiber 1 after fusion splicing while holding both ends of the optical fiber 1, and the tensile load at the time of fracture of the connecting portion was measured as the strength of fusion splicing. The tensile test can be performed, for example, using a fiber crawler.
Optical microscope images of the connecting portion of the optical fiber 1 manufactured in the present embodiment are shown using fig. 5 and 6. Fig. 5 is a view showing an optical microscopic image of the optical fiber of example 1. Fig. 6 is a diagram showing an optical microscopic image of the optical fiber of example 2.
In fig. 5 and 6, an optical microscopic image of the outer periphery of the optical fiber 1 ((a) of each figure) and a transmission optical microscopic image of the optical fiber 1 ((B) of each figure) are shown. In fig. 5 and 6, the 1 st optical fiber 2 is denoted by "2" and the 2 nd optical fiber 3 is denoted by "3".
As shown in fig. 5 and 6, in the optical fiber 1 of any of the embodiments, the diameter of the tip portion of the 1 st optical fiber 2 on the side connected to the 2 nd optical fiber 3 is reduced to have a tapered shape. No step of sharp change in diameter was observed at the connecting portion of the two optical fibers.
As is clear from the transmission optical microscopic image, the tip of the 2 nd optical fiber 3 is inserted into the core of the 1 st optical fiber 2, and the tip of the 2 nd optical fiber 3 is covered with the core of the 1 st optical fiber 2 from 3 directions.
Further, as is clear from the results of the tensile test conducted on the optical fibers 1 of examples 1 and 2, the connection portion of the optical fiber 1 of the present example can withstand a load of 200gf to 250gf (1.6 MPa to 2MPa in terms of pressure).
This indicates that the connection portion of the optical fiber 1 of the present embodiment has a conventional strength of about 200 times as compared with the result of the verification test of the optical fiber in the above-mentioned patent document 1 (strength of the connection portion: 80 kPa).
In addition, by forming the tapered shape in the connecting portion (that is, the 1 st optical fiber 2 has the tapered portion 21), the strength of the connecting portion is also improved by 2 times or more as compared with the optical fiber of the comparative example described later.
In addition, in order to examine the fusion loss at the connection portion of the optical fiber 1 manufactured in the present embodiment and the optimum taper angle θ, optical fibers 1 having tapered portions 21 having various taper angles θ were manufactured, and the fusion loss of each optical fiber 1 was measured.
The inspection light IL outputted from the inspection light source 12 is incident from the 2 nd optical fiber 3 side, the intensity of the inspection light IL is measured by the light receiving device 14 on the 1 st optical fiber 2 side, and the fusion loss is calculated according to the following equation.
In the following expression, "the intensity of the transmitted light in the 2 nd optical fiber 3 alone" may be an actual measurement value obtained by measuring the intensity of the inspection light IL that enters one of the 2 nd optical fibers 3 and is output from the other by the light receiving device 14, or may be a theoretical value calculated from the transmittance of the 2 nd optical fiber 3.
Fusion loss is 1- (intensity of inspection light IL measured by light-receiving device 14/intensity of transmitted light in 2 nd optical fiber 3 alone)
Hereinafter, the relationship between the taper angle θ of the tapered portion 21 and the welding loss will be described with reference to fig. 7 and 8. Fig. 7 is a graph showing the relationship between the taper angle and the fusion loss of the optical fiber of example 1. Fig. 8 is a graph showing the relationship between the taper angle and the fusion loss of the optical fiber of example 2.
In fig. 7 and 8, "," indicates a value at which the fusion splice loss is extremely large, and means that the optical fiber 1 is broken at the connection portion (for example, the fusion splice is released and broken at the time of fusion splice of the optical fiber (at the time of heating and gradual cooling), and is broken at the time of handling the optical fiber 1 after fusion splice).
As shown in fig. 7 and 8, it is understood that the fusion loss of the optical fiber 1 whose connecting portion is not broken is extremely low, i.e., 0.2dB or less. That is, it is understood that the welding method of embodiment 1 described above is an excellent method in which only welding loss is generated to such an extent that actual use is not hindered.
In addition, as shown in fig. 7 and 8, when the taper angle θ is out of the specific range, the connection portion is broken in all the optical fibers 1. From this, it is understood that if the taper angle θ of the tapered portion 21 is set to an appropriate angle, the strength of the connection portion can be made sufficient. Specifically, if the taper angle θ is set to 20 to 50 degrees, the strength of the connection portion can be improved.
Further, it is understood that the optimum value of the taper angle θ for enhancing the strength of the connection portion is different between the case of embodiment 1 and the case of embodiment 2.
Specifically, in example 1 shown in fig. 7, that is, in the case where the 1 st diameter d1(240 μm) is about 2 times the 2 nd diameter d2(125 μm), the optimum taper angle θ is in the range of 22 degrees to 30 degrees.
On the other hand, in the case of example 2 shown in fig. 8, that is, in the case where the 1 st diameter d1(330 μm) is about 3 times the 2 nd diameter d2(125 μm), the optimum taper angle θ is in the range of 35 degrees to 50 degrees.
In this way, by setting the taper angle θ to an appropriate range according to the ratio of the 1 st diameter d1 of the 1 st optical fiber 2 to the 2 nd diameter d2 of the 2 nd optical fiber 3, the tapered portion 21 can be formed into an optimum shape in which stress is not easily concentrated on the connecting portion of the 1 st optical fiber 2 and the 2 nd optical fiber 3.
(5) Comparative example
Hereinafter, comparative experiments were performed to confirm the effectiveness of the optical fiber 1 and the optical fiber fusion splicing method according to embodiment 1.
First, as comparative example 1, the diameter of the 1 st optical fiber 2 and the diameter of the 2 nd optical fiber 3 were made the same (the 1 st diameter d1 being equal to the 2 nd diameter d2), and fusion splicing of these two optical fibers was attempted. The results are shown in fig. 9. Fig. 9 is a view showing a transmitted optical microscopic image of the optical fiber manufactured in comparative example 1.
As shown in FIG. 9, if the 1 st diameter d1 and the 2 nd diameter d2 are made to be the same degree, the 2 nd optical fiber 3 is not inserted into the 1 st optical fiber 2. In addition, therefore, the connecting portion cannot be formed in a tapered shape.
In the optical fiber of comparative example 1, the connection portion was broken by a load smaller than 100gf (pressure conversion: 0.8 MPa).
Thus, in order to insert the 2 nd optical fiber 3 into the 1 st optical fiber 2 to improve the strength of the connection portion, the 1 st diameter d1 is preferably sufficiently larger than the 2 nd diameter d2, for example, in the range of 1.5 to 3 times the 2 nd diameter d 2.
Next, as comparative example 2, in the above fusion splicing method, as shown in fig. 4 (C), in a state where the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2, the 2 nd optical fiber 3 is cooled without moving in the 2 nd direction, and the 1 st optical fiber 2 and the 2 nd optical fiber 3 are fusion spliced.
In addition, the same optical fibers as those used in example 1 above were used for the 1 st optical fiber 2 and the 2 nd optical fiber 3.
Fig. 10 shows an optical microscope image of an optical fiber manufactured without moving the 2 nd optical fiber 3 in the 2 nd direction from the state where the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2. Fig. 10 is a view showing an optical microscopic image of the optical fiber of comparative example 2.
As shown in fig. 10, in the optical fiber of comparative example 2, the 1 st optical fiber 2 and the 2 nd optical fiber 3 were fusion-spliced, but there was a step (indicated by an arrow in fig. 10) in which the diameter sharply changed at the spliced portion.
When the optical fiber having the step at the connecting portion is taken out of the fusion splicing apparatus 100 after fusion splicing, it is broken at the step of the connecting portion or its vicinity, and handling thereof is difficult.
As described above, in order to increase the strength of the connection portion between the 1 st optical fiber 2 and the 2 nd optical fiber 3, it is preferable that the connection portion between these two optical fibers is formed in a tapered shape.
(6) Common matters of the embodiments
The above embodiment 1 has the following configuration and functions in common.
The optical fiber fusion splicing method is a method of fusion splicing a 1 st optical fiber 2 having a 1 st melting point (an example of the 1 st optical fiber) and a 2 nd optical fiber 3 having a 2 nd melting point higher than the 1 st melting point (an example of the 2 nd optical fiber). The welding method has the following steps.
The 1 st optical fiber 2 having the 1 st diameter d1 (an example of the 1 st diameter) and the 2 nd optical fiber 3 having the 2 nd diameter d2 (an example of the 2 nd diameter) smaller than the 1 st diameter d1 are arranged.
The tip of the 1 st optical fiber 2 is heated to at least the 1 st temperature at which the 1 st optical fiber 2 is softened and a temperature lower than the 2 nd temperature at which the 1 st optical fiber 2 is crystallized.
The 2 nd optical fiber 3 is moved in the 1 st direction close to the 1 st optical fiber 2 in a state where the 1 st optical fiber tip is heated, and the 2 nd optical fiber 3 tip is inserted into the 1 st optical fiber 2.
After the tip of the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2, the 2 nd optical fiber 3 is moved in the 2 nd direction opposite to the 1 st direction.
In the optical fiber fusion splicing method according to embodiment 1, after the 1 st optical fiber 2 is softened and the distal end of the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2, the 2 nd optical fiber 3 is further moved in the 2 nd direction opposite to the 1 st direction in which the distal end of the 2 nd optical fiber 3 is inserted into the 1 st optical fiber 2. That is, the 2 nd optical fiber 3 is moved in a direction away from the 1 st optical fiber 2.
Thus, when the 2 nd optical fiber 3 is moved in a direction away from the 1 st optical fiber 2, the tip portion of the 1 st optical fiber 2 on the side connected to the 2 nd optical fiber 3 is pulled. By this drawing, the diameter of the tip portion of the 1 st optical fiber 2 is reduced, and the connection portion between the 1 st optical fiber and the 2 nd optical fiber is tapered.
In this way, by forming the connecting portion between the 1 st optical fiber 2 and the 2 nd optical fiber 3 into a tapered shape, the strength of the optical fiber 1 (an example of an optical fiber) manufactured by connecting these two optical fibers can be improved. For example, when the manufactured optical fiber 1 is bent, stress can be made less likely to concentrate on the connecting portion of the two optical fibers, and thus strength can be improved.
Further, by heating the tip of the 1 st optical fiber 2 having a low melting point, when the 2 nd optical fiber 3 is moved in a direction away from the 1 st optical fiber 2, the tapered shape is easily formed at the connecting portion.
2. Other embodiments
While one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. In particular, the plurality of embodiments and modifications described in the present specification can be arbitrarily combined as needed.
(A) The tip portions of the 1 st optical fiber 2 and the 2 nd optical fiber 3 can be heated not only by irradiation of the heating laser light HL but also by other heating methods. For example, discharge heating and heating by a heater can be performed.
(B) The fusion splicing of the 1 st optical fiber 2 and the 2 nd optical fiber 3 can be performed in a controlled atmosphere. For example, when a glass having deliquescence such as a fluoride glass is used as the 1 st optical fiber 2, fusion splicing can be performed in a dry atmosphere in order to prevent the fluoride glass from being crystallized due to humidity (moisture) in the atmosphere.
Further, depending on the properties of the material used for the optical fiber, the fusion-spliced connection can be performed in a controlled atmosphere such as an atmosphere with less oxygen (e.g., a nitrogen atmosphere, an inert gas atmosphere), a dry atmosphere, or the like.
Further, in order to heat the two optical fibers efficiently and with high accuracy, fusion splicing may also be performed in a windless atmosphere.
Industrial applicability
The present invention can be widely applied to a fusion splicing method in which two optical fibers made of materials having different melting points are fusion-spliced at the leading ends thereof, and an optical fiber in which two optical fibers made of materials having different melting points are fusion-spliced.
Description of the reference symbols
1: an optical fiber; 2: 1 st optical fiber; 21: a conical portion; θ: a taper angle; d 1: 1 st diameter; 3: a 2 nd optical fiber; d 2: a 2 nd diameter; 100: a welding device; 4: an optical fiber moving device; 41: a 1 st moving part; 41 a: 1, moving a workbench; 41 b: 1 st holding part; 43: a 2 nd moving part; 43 a: 2 nd moving working table; 43 b: the 2 nd holding part; 6: a heating light source; HL: heating the laser; 61: a 1 st reflecting mirror; 62: an optical branching section; 63: a 2 nd reflecting mirror; 64: a 1 st lens; 65: a 3 rd reflecting mirror; 66: a 2 nd lens; 8: a shutter; 10: a camera; 12: inspecting the light source; 14: a light receiving device; IL: the light is examined.
Claims (19)
1. A fusion splicing method for fusion splicing a 1 st optical fiber having a 1 st melting point and a 2 nd optical fiber having a 2 nd melting point higher than the 1 st melting point,
the welding method comprises the following steps:
configuring the 1 st optical fiber having a 1 st diameter and the 2 nd optical fiber having a 2 nd diameter smaller than the 1 st diameter;
heating at least the leading end of the 1 st optical fiber to a temperature which is not less than the 1 st temperature at which the 1 st optical fiber is softened and less than the 2 nd temperature at which the 1 st optical fiber is crystallized;
moving the 2 nd optical fiber in a 1 st direction approaching the 1 st optical fiber in a state where at least a tip of the 1 st optical fiber is heated, and inserting a tip of the 2 nd optical fiber into the 1 st optical fiber; and
after the leading end of the 2 nd optical fiber is inserted into the 1 st optical fiber, the 2 nd optical fiber is moved in a 2 nd direction opposite to the 1 st direction.
2. The fusion splicing method according to claim 1,
the welding method also comprises the following steps: after moving the 2 nd optical fiber in the 2 nd direction, gradually cooling the 1 st optical fiber and the 2 nd optical fiber.
3. The welding method according to claim 1 or 2,
in the step of inserting the distal end of the 2 nd optical fiber into the 1 st optical fiber, an insertion distance of the distal end of the 2 nd optical fiber into the 1 st optical fiber is a distance in a range of 20% to 40% of the 2 nd diameter.
4. The welding method according to any one of claims 1 to 3,
in the step of moving the 2 nd optical fiber in the 2 nd direction, the moving distance of the 2 nd optical fiber is a distance in a range of 50% to 70% of the 2 nd diameter.
5. The welding method according to any one of claims 1 to 4,
in the step of disposing the 1 st optical fiber and the 2 nd optical fiber, a tip of the 1 st optical fiber and a tip of the 2 nd optical fiber are disposed in proximity to each other.
6. The welding method according to any one of claims 1 to 5,
the 1 st diameter is in a range of 1.5 to 3 times the 2 nd diameter.
7. The welding method according to any one of claims 1 to 6,
the 1 st temperature is a softening point of the 1 st optical fiber.
8. The welding method according to any one of claims 1 to 7,
the 2 nd temperature is a crystallization temperature of the 1 st optical fiber.
9. The welding method according to any one of claims 1 to 8,
the 1 st optical fiber is a fluoride optical fiber.
10. The welding method according to any one of claims 1 to 9,
the 2 nd optical fiber is a quartz optical fiber.
11. An optical fiber, comprising:
a 1 st optical fiber having a tapered portion with a diameter decreasing from the 1 st diameter toward a leading end; and
and a 2 nd optical fiber having a 2 nd diameter smaller than the 1 st diameter, the 2 nd optical fiber being connected to the 1 st optical fiber in a state where a tip of the 2 nd optical fiber is inserted into a tip of the tapered portion.
12. The optical fiber of claim 11,
the insertion depth of the 2 nd optical fiber into the tapered portion is in the range of 4% to 16% of the 2 nd diameter.
13. The optical fiber of claim 11 or 12,
the taper angle formed by the side surface of the taper portion and the length direction of the 1 st optical fiber is in the range of 20 degrees to 50 degrees.
14. The optical fiber according to any one of claims 11 to 13,
the 1 st diameter is in a range of 1.5 to 3 times the 2 nd diameter.
15. The optical fiber of claim 14,
the 1 st diameter is 2 times the 2 nd diameter, and a taper angle formed by a side surface of the tapered portion and a longitudinal direction of the 1 st optical fiber is in a range of 22 degrees to 30 degrees.
16. The optical fiber of claim 14,
the 1 st diameter is 3 times the 2 nd diameter, and a taper angle formed by a side surface of the tapered portion and a longitudinal direction of the 1 st optical fiber is in a range of 35 degrees to 50 degrees.
17. The optical fiber according to any one of claims 11 to 16,
the 1 st optical fiber is a fluoride optical fiber.
18. The optical fiber according to any one of claims 11 to 17,
the 2 nd optical fiber is a quartz optical fiber.
19. A fusion-splicing device for fusion-splicing a 1 st optical fiber having a 1 st melting point and a 2 nd optical fiber having a 2 nd melting point higher than the 1 st melting point,
the welding device comprises:
a heating light source that heats a tip of the 1 st optical fiber having a 1 st diameter to a temperature that is equal to or higher than a 1 st temperature at which the 1 st optical fiber is softened and lower than a 2 nd temperature at which the 1 st optical fiber is crystallized; and
and an optical fiber moving device that moves the 2 nd optical fiber having a 2 nd diameter smaller than the 1 st diameter in a 1 st direction in which the 2 nd optical fiber approaches the 1 st optical fiber, inserts the tip of the 2 nd optical fiber into the 1 st optical fiber, and then moves the 2 nd optical fiber in a 2 nd direction opposite to the 1 st direction in a state in which at least the tip of the 1 st optical fiber is heated.
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| Application Number | Priority Date | Filing Date | Title |
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| JP2018184101 | 2018-09-28 | ||
| JP2018-184101 | 2018-09-28 | ||
| PCT/JP2019/025703 WO2020066190A1 (en) | 2018-09-28 | 2019-06-27 | Method for fusion splicing optical fiber, optical fiber, and fusing device |
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| CN112823302A true CN112823302A (en) | 2021-05-18 |
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| CN201980062816.8A Withdrawn CN112823302A (en) | 2018-09-28 | 2019-06-27 | Optical fiber fusion splicing method, optical fiber, and fusion splicing device |
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| Country | Link |
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| JP (1) | JPWO2020066190A1 (en) |
| CN (1) | CN112823302A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113955926A (en) * | 2021-12-03 | 2022-01-21 | 吉林大学 | Low-temperature fusion welding method for improving strength of fusion welding point between soft glass optical fiber and quartz optical fiber |
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| JP3285166B2 (en) * | 1992-06-24 | 2002-05-27 | 住友電気工業株式会社 | Optical fiber functional component and method of manufacturing the same |
| JP2001318261A (en) * | 2000-05-09 | 2001-11-16 | Sumitomo Electric Ind Ltd | Method for manufacturing optical fiber element and optical fiber element |
| JP4729394B2 (en) * | 2004-12-28 | 2011-07-20 | プレサイスゲージ株式会社 | Optical component manufacturing method and apparatus, and optical component |
| JP2007065437A (en) * | 2005-09-01 | 2007-03-15 | Juki Corp | Fiber collimator |
| JP2011039493A (en) * | 2009-07-13 | 2011-02-24 | Central Glass Co Ltd | Fusion-splicing structure and optical waveguide element having the structure, and light source device using the same, and splicing method |
| PL400636A1 (en) * | 2012-09-03 | 2014-03-17 | P.H. Elmat Spólka Z Ograniczona Odpowiedzialnoscia | Method for thermal fiber splicing |
| JP2014191277A (en) * | 2013-03-28 | 2014-10-06 | Sumitomo Electric Ind Ltd | Laser transmission fiber and manufacturing method therefor |
| US10310184B2 (en) * | 2017-03-07 | 2019-06-04 | Afl Telecommunications Llc | Methods for splicing optical fibers |
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2019
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- 2019-06-27 WO PCT/JP2019/025703 patent/WO2020066190A1/en active Application Filing
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113955926A (en) * | 2021-12-03 | 2022-01-21 | 吉林大学 | Low-temperature fusion welding method for improving strength of fusion welding point between soft glass optical fiber and quartz optical fiber |
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