JP2001318265A - Method for coupling optical fiber and coupling optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for coupling an optical fiber, capable of coupling plural laser beam exited from plural exit side optical fibers to one incident side optical fiber, without producing leakage in the state of high energy density. SOLUTION: Plural laser beams from plural exit side optical fibers 11 are made incident into slopes of a first conical primes 15, whose apex is directed to the incident side, plural laser beams exited from the first conical prism are made incident into a second conical prism 16 whose apex is directed to the opposite side of that of the first conical prism and which is arranged on the same optical axis as that of the first conical prism, and exited plural laser beams are condensed by a condenser lens 17, to make the laser beams incident into one incident side optical fiber 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber coupling method and a coupling optical system for synthesizing a plurality of laser beams emitted from a plurality of optical fibers and causing the laser beams to enter one optical fiber.

[0002]

2. Description of the Related Art There is known an optical fiber coupling method in which a plurality of laser beams emitted from a plurality of emission side optical fibers are combined and made incident on one incidence side optical fiber (see, for example, Japanese Patent Application Laid-Open No. H8-08258). 75947). In this coupling method, a plurality of laser beams emitted from a plurality of emission-side optical fibers are respectively collimated by a collimating lens system.
Then, the plurality of collimated laser beams are combined in a parallel and multi-layer state (concentric) so as not to interfere with each other by the perforated reflection mirror, and all the combined laser beams are collected by the condenser lens system. Light is incident on one incident side optical fiber with all optical axes aligned.

[0003]

In this coupling method, as the number of outgoing optical fibers increases, the laser incident on a converging lens system for converging all laser beams on one incident optical fiber. The beam diameter increases. This means that three outgoing-side optical fibers are focused on one incident-side optical fiber rather than a laser beam diameter for focusing two outgoing-side optical fibers on one incident-side optical fiber. Means that the laser beam diameter becomes larger.

However, in practice, the core of an optical fiber used, for example, a step index type (SI type) optical fiber is made of quartz, and the laser beam taking-in angle is NA = 0.20, that is, sin θ = 0.20. The maximum capture angle θ is defined. In this case, since the maximum take-in angle θ is about 11.5 ° and the NA shows a half angle value, the full angle value is about 23 °.

When a plurality of laser oscillators used to supply a laser beam to a plurality of output side optical fibers have the same specifications, the diameter of the laser beam formed by the two output side optical fibers is smaller than that of the laser beam formed by the two output side optical fibers. The diameter of the laser beam formed by the emission side optical fiber is 3/2 = 1.5 times larger. This means that the angle of taking in the laser beam required to converge the light on one incident side optical fiber increases in proportion to the number of outgoing side optical fibers.

This is because, in the above-mentioned coupling method, the laser beams from a plurality of outgoing side optical fibers are made to enter one incident side optical fiber. This means that even if an attempt is made to couple the laser beam of the outgoing side optical fiber to one incoming side optical fiber, it may be possible to focus only at an angle larger than the laser take-in angle of the incoming side optical fiber. In this case, the laser beam leaks from the incident side optical fiber, and a phenomenon occurs in which the incident side optical fiber is burned.

It is an object of the present invention to couple a plurality of laser beams emitted from a plurality of output side optical fibers to one input side optical fiber in a state of high energy density without causing leakage. It is an object of the present invention to provide an optical fiber coupling method that can be performed.

Another object of the present invention is to provide a coupling optical system of an optical fiber suitable for the above coupling method.

[0009]

According to the present invention, a plurality of laser beams emitted from a plurality of optical fibers are made incident on an inclined surface of a first conical prism whose vertices face the incident side,
A plurality of laser beams emitted from the first cone-shaped prism are directed to a second cone having vertices directed to the opposite side of the first cone-shaped prism and arranged on the same optical axis as the first cone-shaped prism. The present invention provides a method for coupling optical fibers, wherein a plurality of laser beams emitted from the laser beam are made incident on a prism and condensed into one optical fiber.

In this coupling method, the first conical prism and the second conical prism have similar shapes, and a plurality of laser beams emitted from the plurality of optical fibers are respectively transmitted through the collimating lens. The light is incident on one conical prism.

In the present coupling method, it is preferable that the plurality of laser beams emitted from the second conical prism are condensed through a condenser lens.

In the present coupling method, it is preferable that the first and second conical prisms are conical prisms having the same apex angle.

According to the present invention, there is also provided a first conical prism having an apex directed to the incident side, and the first conical prism on the same optical axis as the first conical prism and on the exit side thereof. A second conical prism arranged with its vertex facing the opposite side of the prism, and a plurality of laser beams emitted from a plurality of optical fibers are incident on the slope of the first conical prism. A plurality of laser beams emitted from one conical prism are incident on the second conical prism, and a plurality of laser beams emitted from the second conical prism are condensed and incident on one optical fiber. An optical fiber coupling optical system is provided.

Also in the present coupling optical system, the first conical prism and the second conical prism have similar shapes, and the exit ends of the plurality of optical fibers and the incident side of the first conical prism. By disposing a collimating lens between
Incident on the conical prism.

In the present coupling optical system, a condensing lens is arranged between the exit side of the second conical prism and the entrance side of the one optical fiber. The plurality of emitted laser beams are condensed and incident on the one optical fiber.

In the present coupling optical system, the laser beams emitted from the plurality of optical fibers and collimated by the collimating lens are incident on the first conical prism at different angles via respective reflecting mirrors.

In the present coupling optical system, the plurality of optical fibers are further arranged so as to extend in a vertical direction parallel to the optical axis, and a laser beam emitted from the plurality of optical fibers and collimated by the collimating lens is provided. Each of them may be made to enter the first conical prism.

In the present coupling optical system, further, the first,
It is preferable that a mechanism for adjusting the position of one of the second conical prisms in the optical axis direction is provided.

In the present coupling optical system, further, the first,
Preferably, each of the second conical prisms is a conical prism having the same apex angle.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of an optical fiber coupling optical system according to the present invention will be described with reference to FIGS. The optical fiber coupling optical system according to the present embodiment transmits six laser beams output from six laser oscillators having the same specifications through six emission-side optical fibers, and emits six laser beams from the emission ends. This is for coupling the beam to one incident side optical fiber. The specific configuration will be described sequentially.

Each of 1.6 laser oscillators (not shown) is connected with a step index type (SI type) optical fiber 11 as a light emitting side optical fiber 11 having a core diameter of φ600 μm, thereby enabling laser energy transmission. I have.

The outgoing ends of the 2.6 optical fibers 11 are attached to the entrance 12 of the optical fiber coupling optical system. Here, the six emission-side optical fibers 11 are radially arranged so as to extend in the horizontal direction about the optical axis of the optical fiber coupling optical system.

3. The laser beams emitted from the emission-side optical fiber 11 mounted on the incidence section 12 are collimated (parallel) by a collimating lens 13.

In this embodiment, the focal length f of the collimating lens 13 is designed to be 80 mm, and the diameter of the collimated laser beam is 20 mm.

Each of the 4.6 collimated laser beams is reflected downward by the reflecting mirror 14 and is irradiated on the first conical prism 15. The first conical prism 15 has a diameter of φ130 mm, the central axis thereof coincides with the optical axis of the present optical fiber coupling optical system, and the apex is arranged upward, that is, toward the laser beam incident side.
The six laser beams having a diameter of 20 mm correspond to the external dimensions of the collimating lens 13 having a focal length of f80 mm and the reflecting mirror 1.
The light is applied to the first conical prism 15 while maintaining the distance defined by the outer dimensions of the first conical prism 4.

On the lower side of the first conical prism 15, that is, on the exit side, the second conical prism 16 (φ60 mm) with its apex facing the optical axis and opposite to the first conical prism 15. ) Is arranged. Also, the second
A condensing lens 17 is arranged below the conical prism 16, that is, on the exit side, so that the optical axis coincides with the convergent prism 16. Furthermore, an incident side optical fiber 18 is provided below the condenser lens 17 at a position corresponding to the focal length on the optical axis of the condenser lens 17.

5.6 The collimated laser beam has a diameter φ7 centered on the vertex of the first conical prism 15.
Irradiation is performed so that the center of the laser beam φ20 mm is positioned at equal angular intervals on the circumference of 0 mm. In this case, when the six collimated laser beams are regarded as one laser beam, the outermost laser beam diameter is (φ70 mm + φ10 mm + φ10 mm) as shown in FIG.
And can be regarded as φ90 mm.

6. When these six laser beams are directly condensed by the condenser lens 17 (focal length f = 120 mm) without the first conical prism 15 and the second conical prism 16, the laser beam diameter is φ90 mm. NA at this time is Becomes

As described above, when the laser beam is incident on the incident side optical fiber 18 only through the condenser lens 17 having the focal length f = 120 mm, the laser beam incident angle becomes larger than the fiber take-in angle, and the incident side optical fiber 18 Part of the laser beam leaks from the
Burn itself. For this reason, the fiber cannot be actually incident in this state.

[7] At this time, the incident side optical fiber 18
The diameter of the laser spot focused on the incident end face of
0 μm (core diameter of emission side optical fiber 11) × f120 m
m (focal length of the condenser lens 17) / f80 mm (focal length of the collimating lens 13) = φ900 μm.

Accordingly, the core diameter of the optical fiber usable as the incident side optical fiber 18 is φ900 μm or more.

In this embodiment, six laser beams of the output side optical fiber 11 having a core diameter of 600 μm are combined with one core diameter φ.
1000 μm incident side optical fiber 18 or φ120
The optical fiber 18 is coupled to the incident optical fiber 18 of 0 μm.

8. In this embodiment, as a method of reducing the outermost diameter of the six collimated laser beams, two methods are used.
First and second conical prisms 15, 16 having the same apex angle α
Are arranged such that the vertices face outward. Further, the first conical prism 15 and the second conical prism 16 are arranged on the same optical axis. Further, the first conical prism 15
Is mechanically fixed, and the distance between the second conical prism 16 and the first conical prism 15 is variable with respect to the optical axis.

9. Assuming that the apex angle of the first and second conical prisms 15 and 16 is α, the deflection angle is β, and the refractive index is n, the deflection angle δ can be approximated by δ = (n−1) β.

The first and second conical prisms 15, 16
Is defined as d.

10.6 collimated φ20 mm
When the laser beam is incident on the first conical prism 15 in a state where the facing center distance is 70 mm away and the outermost diameter of the entire laser beam is φ90 mm, the deflection angle δ of the conical prism and the The distance d between the first and second conical prisms 15 and 16 can reduce the facing center distance 70 mm.

11. In this embodiment, the outermost diameters of the six φ20 mm laser beams are set to the first and second conical prisms 15,
16 by using φ 16 as shown in FIGS.
Can be compressed to 44 mm. In FIG. 1, φα
What is indicated by mm is a value defined from mechanical tolerance and adjustment margin.

12. Focal length f120 of the condenser lens 17
mm, the beam diameter to the incident side optical fiber 18 is φ44 mm, And the incident angle of the laser beam is
Within the laser capture angle.

As is apparent from the above description, according to the present embodiment, the six laser beams emitted from the six emission-side optical fibers 11 can be combined with each other in a high energy density state without leakage. It can be coupled to the entrance side optical fiber 18.

FIGS. 2 and 3 show the actual configuration of the coupling optical system. As is apparent from FIG.
4. The first conical prism 15 is housed in a cylindrical case 20. As shown in FIG. 6, the six reflecting mirrors 14 are attached to a hexagonal pyramid attached to the upper lid of the case 20. The second conical prism 16 and the condenser lens 17 are housed in a cylindrical case 21 attached to the lower end of the case 20. The incident side optical fiber 18 is attached to the lower end of the case 21. Needless to say, the pass area of the laser beam at the bottom of the case 20 is made of a transparent member (in the case of FIG. 2) or an opening.

Further, the second conical prism 16 described above is used.
Although not shown, a mechanism for making the position variable in the optical axis direction can be realized by, for example, the following structure. The second conical prism 16 is held by a prism holder, and the prism holder can be slid along the inner wall of the case 21, and a knob provided thereon is
The case 21 is led out of the case 21 through an elongated hole provided along the axial direction of the case 21. Then, the knob can be fixed to the case 21 by a screw or the like. When adjusting the position of the second conical prism 16, the screw may be loosened and moved up and down, and after the adjustment is completed, the screw may be fixed again with the screw.

On the other hand, each of the six collimating lenses 13 has a case 22 radially attached to the case 20.
Is housed in The case 22 is provided with the incident portion 12 to which the above-mentioned emission side optical fiber 11 is fixed.

As described above, due to the combination of the collimating lens 13 and the pair of first and second conical prisms 15 and 16, a plurality of laser beams incident on the first conical prism 15 are formed as shown in FIG. The plurality of laser beams that are parallel and that are emitted from the second conical prism 16 are also parallel, and the diameter of incidence on the condenser lens 17 can be reduced. For this purpose, the first and second conical prisms 15,
Preferably, 16 is a similar shape. Assuming that there is no pair of first and second conical prisms 15 and 16,
Since the diameter of incidence on the condenser lens 17 increases, the size of the entire coupling optical system increases.

Referring to FIGS. 7 and 8, a second embodiment of the present invention will be described. In this embodiment, the housing structure of the reflection mirror 14 and the first conical prism 15 in the case 20 and the second conical prism 1 in the case 21
6. The housing structure of the condenser lens 17 is the same as that of the first embodiment. The difference from the first embodiment is that six outgoing-side optical fibers 11 extend in the up-down (vertical) direction at equal intervals on the same circumference centered on the optical axis of the present coupling optical system. It is located at the point. For this purpose, a case 22 accommodating the collimating lens 13 is attached so as to extend vertically at equal intervals on the same circumference of the upper lid of the case 20. Of course, the upper cover is provided with an opening or a laser light transmitting portion in a region immediately below the emission side optical fiber 11. Then, in order to introduce the laser beam emitted downward from the emission-side optical fiber 11 to the reflection mirror 14, the laser beam from the emission-side optical fiber 11 is horizontally reflected on the lower side of the upper lid. Reflection mirrors 19
Is attached. According to the second embodiment, the radial dimension of the optical fiber coupling optical system can be reduced as compared with the first embodiment.

According to the optical fiber coupling optical system of the present invention,
Even if there are a plurality of three or more, specifically, six or more outgoing optical fibers, if the shapes (sizes) and distances of the first and second conical prisms are ensured, the outgoing optical fibers are emitted. It is possible to compress the outermost outer diameter of a plurality of subsequent laser beams. This means that six or more outgoing optical fibers can be coupled.

Further, a pyramid prism may be used instead of the conical prism, or the position of the first conical prism may be adjusted instead of the second conical prism, and the plurality of laser oscillators may not necessarily have the same specifications. For example, when a hexagonal pyramid prism is used, it is necessary to make a laser beam incident on a surface avoiding the boundary between the six surfaces. This means that the outer diameter of the six laser beams is larger than that of the conical prism described with reference to FIG.

[0047]

According to the present invention, three or more, preferably six, outgoing optical fibers transmitted with energy from a plurality of laser oscillators, and in principle, even with six or more outgoing optical fibers, the energy density can be reduced. It can be coupled to one incident side optical fiber at a high state without leakage.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical fiber coupling optical system according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a first embodiment of an optical fiber coupling optical system according to the present invention.

FIG. 3 is a top view of the coupling optical system of the optical fiber shown in FIG. 2;

FIG. 4 is a view for explaining the operation of the first conical prism shown in FIG. 1;

FIG. 5 is a view for explaining the operation of the second conical prism shown in FIG. 1;

FIG. 6 is a diagram showing the relationship between the six reflecting mirrors and the collimating lens shown in FIG. 1 as viewed from below.

FIG. 7 is a longitudinal sectional view of a second embodiment of a coupling optical system for optical fibers according to the present invention.

FIG. 8 is a top view of the coupling optical system of the optical fiber shown in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Emission-side optical fiber 12 Incident part 13 Collimating lens 14 and 19 Reflecting mirror 15 First conical prism 16 Second conical prism 17 Condensing lens 18 Incident-side optical fiber 20, 21, 22 Case

Claims (11)

[Claims] 1. A plurality of laser beams emitted from a plurality of optical fibers are made incident on an inclined surface of a first conical prism whose apexes face the incident side, and a plurality of laser beams emitted from the first conical prism are emitted. Beams are directed to a second conical prism arranged with its apex on the opposite side to the first conical prism and on the same optical axis as the first conical prism. An optical fiber coupling method, wherein light is condensed and made incident on one optical fiber. 2. The method according to claim 1, wherein the first conical prism and the second conical prism have similar shapes, and a plurality of laser beams emitted from the plurality of optical fibers. Are respectively input to said first conical prism through a collimating lens. 3. The method according to claim 2, wherein the plurality of laser beams emitted from the second conical prism are condensed through a condenser lens. . 4. The optical fiber coupling method according to claim 1, wherein said first and second conical prisms are conical prisms having the same apex angle. Fiber coupling method. 5. A first conical prism whose apex is directed to the incident side, and on the same optical axis as the first conical prism, on the exit side, and opposite to the first conical prism. A second conical prism arranged with its apex facing the side, and a plurality of laser beams emitted from a plurality of optical fibers are made incident on an inclined surface of the first conical prism, the first conical prism A plurality of laser beams emitted from the second conical prism are made incident on the second conical prism, and the plurality of laser beams emitted from the second conical prism are condensed and made incident on one optical fiber. A coupling optical system for an optical fiber, comprising: 6. The optical fiber coupling optical system according to claim 5, wherein the first conical prism and the second conical prism are similar in shape, and the emission ends of the plurality of optical fibers and the second conical prism. The coupling optics of an optical fiber, wherein a collimated laser beam is incident on the first conical prism by disposing a collimating lens between the incident side of the first conical prism and the collimating lens. system. 7. The optical fiber coupling optical system according to claim 6, wherein a condensing lens is disposed between an exit side of the second conical prism and an entrance side of the one optical fiber. An optical fiber coupling optical system, wherein a plurality of laser beams emitted from a second conical prism are condensed and incident on the one optical fiber. 8. The optical fiber coupling optical system according to claim 6, wherein the laser beams emitted from the plurality of optical fibers and collimated by the collimating lens are respectively changed in angle via a reflection mirror, and the first beam is changed. A coupling optical system for an optical fiber, which is incident on a conical prism. 9. The optical fiber coupling optical system according to claim 8, wherein said plurality of optical fibers are arranged to extend in a vertical direction parallel to said optical axis, and are emitted from said plurality of optical fibers. A coupling optical system for an optical fiber, wherein a laser beam collimated by a collimator lens is incident on the first conical prism. 10. The optical fiber coupling optical system according to claim 5, wherein a mechanism for adjusting a position of one of said first and second conical prisms in an optical axis direction is provided. An optical fiber coupling optical system, comprising: 11. The coupling optical system according to claim 5, wherein the first and second conical prisms are conical prisms having the same apex angle. Optical fiber coupling optics.