WO2013031563A1

WO2013031563A1 - Coupling structure for multicore fiber

Info

Publication number: WO2013031563A1
Application number: PCT/JP2012/070957
Authority: WO
Inventors: 史生長井
Original assignee: コニカミノルタアドバンストレイヤー株式会社
Priority date: 2011-09-01
Filing date: 2012-08-20
Publication date: 2013-03-07
Also published as: JP2014219428A

Abstract

The purpose of the present invention is to provide a coupling structure capable of minimizing the decrease in coupling efficiency when a multicore fiber is connected to other optical elements. The coupling structure for a multicore fiber has an optical element, a multicore fiber and an optical coupling system. The optical element is either one of a plurality of light sources, a plurality of light-receiving elements, or a bundle of a plurality of single core fibers. The optical coupling system optically couples the optical element to the multicore fiber. The distances among a plurality of light sources (distances among a plurality of light-receiving elements, the distances among a plurality of single core fibers) are larger than the distances among a plurality of cores in a multicore fiber. The optical coupling system has a reflector element and an optical imaging system. The reflector element has a reflection surface for reflecting light emitted from an emission side element. The optical imaging system guides the light reflected by the reflection element to enter an incidence side element.

Description

Multi-core fiber coupling structure

Embodiments of the present invention relate to a coupling structure for coupling an optical element used for optical communication or the like and a multi-core fiber.

With the spread of smartphones and tablet terminals, data communication with a huge amount of information is required. Accordingly, further increase in capacity of optical communication is desired.

Conventional optical communication is performed using a single core fiber in which one core is provided in a clad. However, since there is a capacity limit when communication is performed using one single core fiber, means for performing data communication with a capacity exceeding that is required.

In this regard, for example, a multi-core fiber that is an optical fiber in which a plurality of cores are provided in one clad can be used (see Patent Documents 1 and 2). Since the multi-core fiber has a plurality of cores, it is possible to perform large-capacity data communication compared to the single-core fiber.

In optical communication, such a multi-core fiber may be used by being optically coupled with, for example, a fiber bundle in which a plurality of single-core fibers are bundled, a light emitting element such as a laser diode, or a light receiving element such as a photodiode. is there. Hereinafter, all or part of the multi-core fiber, the fiber bundle, the light emitting element, and the light receiving element may be referred to as “optical element”.

JP-A-10-104443 JP-A-8-119656

Here, when optically coupling the multi-core fiber and other optical elements, securing the coupling efficiency becomes a problem.

When connecting multi-core fibers having the same number of cores, the cores can be reliably connected by aligning the multi-core fibers. Therefore, it is difficult to cause coupling loss, and high coupling efficiency can be achieved.

On the other hand, when the multi-core fiber and another optical element are coupled, there is a problem that coupling efficiency is lowered. For example, when the number of light emitting elements and light receiving elements corresponding to each core of a multi-core fiber is provided, the intervals between the cores are very narrow, and thus the corresponding light emitting elements and light receiving elements must be arranged close to each other (Patent Document 1).

However, in this case, there is a problem in that the coupling efficiency is reduced due to physical interference between the optical elements due to the size of the optical elements and the influence of heat and electrical noise generated by the optical elements.

The present invention solves the above-described problems, and an object of the present invention is to provide a coupling structure that can suppress a decrease in coupling efficiency when a multi-core fiber and another optical element are coupled.

In order to solve the above problems, a multi-core fiber coupling structure according to claim 1 includes an optical element, a multi-core fiber, and a coupling optical system. The optical element is any one of a plurality of light sources, a plurality of light receiving elements, and a fiber bundle obtained by bundling a plurality of single core fibers. In a multi-core fiber, a plurality of cores are covered with a clad. The coupling optical system is disposed between the optical element and the multicore fiber, and optically couples the optical element and the multicore fiber. Any one of the interval between the plurality of light sources, the interval between the plurality of light receiving elements, and the interval between the plurality of single core fibers is arranged to be wider than the interval between the plurality of cores of the multicore fiber. The coupling optical system includes a reflecting element and an imaging optical system. The reflection element has a reflection surface that reflects light emitted from an emission-side element that is one of an optical element and a multi-core fiber. The imaging optical system causes the light reflected by the reflecting element to enter the other incident side element.
In order to solve the above problem, the multi-core fiber coupling structure according to claim 2 is the multi-core fiber coupling structure according to claim 1, wherein the output side element or the incident side element includes a plurality of light sources or a plurality of light sources. In the case of the light receiving elements, at least two of the plurality of light sources or the plurality of light receiving elements are arranged on the same plane.
In order to solve the above problem, the multi-core fiber coupling structure according to claim 3 is the multi-core fiber coupling structure according to

claim

1 or 2, wherein the reflecting element has two or more reflecting surfaces. It is formed of at least one member.
Moreover, in order to solve the said subject, the coupling structure of the multi-core fiber of Claim 4 is a coupling structure of the multi-core fiber of Claim 3, Comprising: A reflective surface is the light radiate | emitted from the output side element. It is inclined with respect to the traveling direction of the plurality of lights emitted from the emission side element so as to reflect at least two lights.
In order to solve the above-mentioned problem, the multi-core fiber coupling structure according to claim 5 is the multi-core fiber coupling structure according to claim 3, wherein the reflecting surface is formed in a stepped shape.
In order to solve the above problem, the multi-core fiber coupling structure according to claim 6 is the multi-core fiber coupling structure according to any one of claims 1 to 5, wherein the imaging optical system includes a plurality of imaging optical systems. The microlenses are arranged in an array.
In order to solve the above problem, the multi-core fiber coupling structure according to claim 7 is the multi-core fiber coupling structure according to any one of claims 1 to 6, wherein the coupling optical system is a relay lens optical system. Has a system. The relay lens optical system guides the light emitted from the emission side element to the imaging optical system. By moving any of the exit side element, the entrance side element, the relay lens optical system, and the reflection element, the position of the exit side element and the entrance side element can be adjusted.

Thus, each of the plurality of lights emitted from the emission side element can be guided to the corresponding incident side element via the reflection element. Therefore, the interval between the optical elements can be made wider than the interval between the plurality of cores of the multi-core fiber, and the arrangement can be simplified. This makes it less susceptible to physical interference between optical elements due to the size of the optical elements, and heat and electrical noise generated by the optical elements. That is, when the multi-core fiber 1 and another optical element are coupled, a decrease in coupling efficiency can be suppressed.

It is a figure which shows the multi-core fiber common to embodiment. It is a figure which shows the coupling structure which concerns on 1st Embodiment. It is a figure which shows the coupling optical system which concerns on 1st Embodiment. It is a figure which shows the coupling structure which concerns on the modification of 1st Embodiment. It is a figure which shows the coupling optical system which concerns on the modification of 1st Embodiment. It is a figure which shows the coupling structure which concerns on 2nd Embodiment. It is a figure which shows the coupling structure which concerns on 3rd Embodiment.

[Configuration of multi-core fiber]
With reference to FIG. 1, the structure of the multi-core fiber 1 common to embodiment is demonstrated. The multi-core fiber 1 is generally a long cylindrical member having flexibility. FIG. 1 is a perspective view of the multi-core fiber 1. In FIG. 1, only the tip portion of the multi-core fiber 1 is shown.

The multi-core fiber 1 is made of a material having a high light transmittance such as quartz glass or plastic. The multicore fiber 1 includes a plurality of cores C _k (k = 1 to n) and a clad 2.

The core C _k is a transmission path for transmitting light from the light source D _k (described later). Each of the cores C _k has an end face E _k (k = 1 to n). Light emitted from a light source D _k (described later) is emitted from the end surface E _k . In order to increase the refractive index as compared with the clad 2, the core C _k is made of a material in which germanium oxide (GeO ₂ ) is added to, for example, quartz glass. Although FIG. 1 shows a configuration having _seven cores C ₁ to C ₇ , the number of cores C _k may be at least two. FIG. 1 shows a configuration in which the cores C ₂ to C ₇ are arranged on a concentric circle with the core C ₁ as the center. However, the configuration is not limited to this as long as the core has at least two cores C _k. Any arrangement is possible.

The clad 2 is a member that covers the plurality of cores _Ck . The clad 2 has a role of confining light from the light source D _k (described later) in the core C _k . The clad 2 has an end face 2a. The end surface _Ek of the core _Ck and the end surface 2a of the clad 2 form the same surface (the end surface 1b of the multicore fiber 1). The cladding 2 material, a low refractive index material is used than the core C _k material. For example, when the material of the core C _k is made of quartz glass and germanium oxide, quartz glass is used as the material of the clad 2. Thus, by making the refractive index of the core C _k higher than the refractive index of the cladding 2, the light from the light source D _k (described later) is totally reflected at the boundary surface between the core C _k and the cladding 2. Therefore, light can be transmitted in the core _Ck .

<First Embodiment>
Next, with reference to FIG.2 and FIG.3, the coupling structure of the multi-core fiber 1 which concerns on 1st Embodiment is demonstrated. In the present embodiment, a structure in which a plurality of light sources D _k (k = 1 to n) and a multi-core fiber 1 are coupled by a coupling optical system 10 will be described. The number of the light sources D _k (seven in the present embodiment) equal to the number of cores of the multi-core fibers 1 to be coupled (seven in the present embodiment) is provided. The plurality of light sources D _k and the plurality of cores C _k are associated one-to-one. That is, there is a light source _{D k} (e.g., _{D 1)} Light from is adapted to be guided to the corresponding core _{C k} (e.g., _{C 1).} FIG. 2 is a sectional view in the axial direction of the coupling optical system 10, the light source _Dk, and the multi-core fiber 1. FIG. In FIG. 2, only the three cores (C ₁ , C ₂ , C ₅ ) of the multi-core fiber 1 and the corresponding three light sources (D ₁ , D ₂ , D ₅ ) are shown. FIG. 3 is a diagram of the coupling optical system 10 viewed from the direction of arrow A in FIG.

[Configuration of coupling optical system]
Coupling optics 10 is arranged between the light source D _k and a multi-core fiber 1, coupling the light source D _k and multi-core fiber 1 optically. The coupling optical system 10 includes a relay lens system 11, a reflection element 12, a support member 13, and an imaging optical system 14.

The relay lens system 11 has a function of guiding the light emitted from the light source _Dk to the imaging optical system 14 (via the reflection element 12). The number of relay lens systems 11 is equal to the number of the light sources _Dk (seven in this embodiment). The relay lens system 11 includes two

convex lenses

11a and 11b. By the

convex lenses

11a and 11b, the light from the light source _Dk is guided to the imaging optical system 14 in a condensed state (via the reflection element 12). The relay lens system 11 is an example of a “relay lens optical system”. Incidentally, the relay lens system 11 corresponding to the light source D ₁ is configured to direct directly to the imaging optical system 14 in a state of being focused light from the light source D _1.

The relay lens system 11 is not limited to a condensing optical system using the

convex lenses

11a and 11b. For example, a collimating optical system that collimates light emitted from the light source _Dk may be used.

The reflection element 12 is an element that reflects the light guided from the light source _Dk via the relay lens system 11 toward the imaging optical system 14. The reflection element 12 is configured by, for example, a mirror or a prism. The reflection element 12 has a reflection surface 12 a that reflects the light guided by the relay lens system 11.

The number of reflection elements 12 provided varies depending on the arrangement of the plurality of light sources _Dk . For example, when the light source D ₁ is arranged on the optical axis of the core C ₁ as in the present embodiment, six reflecting elements 12 are provided so as to correspond to the other light sources D ₂ to D ₇ .

The reflecting surface 12a has a predetermined angle with respect to the optical axis of the corresponding core _Ck . This angle is determined by the arrangement of the light source D _k , the core C _k (multi-core fiber 1), and the imaging optical system 14. In the present embodiment, since the cores C ₂ to C ₇ are arranged on concentric circles centered on C ₁ , the angles of the reflecting surfaces 12a are equal. On the other hand, when the core C _k is not concentric, or when the core C _k is arranged on a plurality of concentric circles having different diameters, the reflecting surface 12a is formed at different angles depending on the arrangement of the corresponding core C _k. .

The support member 13 is a plate-like member that supports at least two of the plurality of light sources D _k (corresponding relay lens system 11 and reflection element 12). In this embodiment, as shown in FIG. 3, the light sources D ₂ to D ₇ , the corresponding relay lens system 11 and the reflecting element 12 are supported by the support member 13. The plurality of light sources D _k (D ₂ to D ₇ ) have an interval p (a distance between light emitting ends of adjacent light sources D _k (see FIG. 3)), and in this embodiment, each of the light sources D ₂ to D ₇ . The intervals are assumed to be equal) so as to be wider than the interval P between the plurality of cores C _k of the multi-core fiber 1 (the distance between the optical axes of adjacent cores C _k (see FIG. 2)). At the center of the support member 13, the hole 13a for passing the light from the light source D ₁ is provided. The light source D ₁ is supported at a predetermined position (on the optical axis of the core C ₁ ) by a member different from the support member 13.

The light source _Dk supported by the support member 13 is arranged on the same plane. By arranging a plurality of light sources D _k (corresponding relay lens system 11 and reflecting element 12) on the same plane, not only the configuration can be simplified, but also the positions of the light source D _k , relay lens system 11 and reflecting element 12 in advance. Adjustments can be made. Therefore, the assembly of the coupling optical system 10 is facilitated (that is, the coupling between the multicore fiber 1 and the light source _Dk is facilitated). In addition, in order to make the space | interval p between each light source _Dk wider, it is also possible to support each light source _Dk with a different support member.

It is also possible to move at least one of the multi-core fiber 1, the light source D _k , the relay lens system 11, and the reflection element 12 perpendicular to the optical axis direction of the light source D _k (or the optical axis direction of the multi-core fiber 1). is there. In this case, it is possible to adjust the position when the light from the light source D _k is incident on the core C _k of the multi-core fiber 1. Further, the position of the light from the light source D _k can be individually adjusted with respect to the core C _k of the multi-core fiber 1. Thereby, the coupling efficiency can be improved.

The imaging optical system 14 has a function of condensing the light reflected by the reflecting element 12 and making it incident on the corresponding core C _k . In the present embodiment, a single convex lens is disposed as the imaging optical system 14. Note that the imaging optical system 14 also has a function of condensing light directly guided from the light source D ₁ and causing the light to enter the core C ₁ of the multicore fiber 1.

[How light travels]
Next, how light travels according to the present embodiment will be described with reference to FIG. In the present embodiment, a configuration in which light is emitted from a plurality of light sources _Dk and guided to the multicore fiber 1 will be described. That is, the plurality of light sources _Dk in the present embodiment is an example of “emission-side element”. On the other hand, the multi-core fiber 1 in the present embodiment is an example of an “incident side element”.

First, light is emitted from each of the plurality of light sources D ₁ to D ₇ . The emitted light is incident on the corresponding relay lens system 11 while being diffused. The incident light is collected by the relay lens system 11 and emitted to the reflecting element 12. The light from the light source D ₁ is directly by the relay lens system 11, is guided to the imaging optical system 14.

Each light emitted from the relay lens system 11 corresponding to the plurality of light sources D ₂ to D ₇ is reflected by the reflecting surface 12 a of the corresponding reflecting element 12 and guided to the imaging optical system 14.

Each of the light reflected by the reflecting surface 12a is collected by the imaging optical system 14 and enters the corresponding cores C ₂ to C ₇ . The light from the light source D _1, except that through the reflective element 12, similarly entering the core C _1.

Here, in the present embodiment, an example in which a plurality of lights emitted from a plurality of light sources _Dk are guided to the multi-core fiber 1 via the coupling optical system 10 has been described, but the target for emitting the light is limited to this. Absent. For example, a fiber bundle (not shown) composed of a plurality of single core fibers is disposed between the plurality of light sources D _k and the relay lens system 11, and the light from the plurality of light sources D _k is indirectly guided to the multi-core fiber 1. It is also possible. In this case, the interval between the plurality of single core fibers (the distance between the optical axes of adjacent single core fibers) is arranged to be wider than the interval P between the plurality of cores C _k of the multicore fiber 1. Here, a fiber bundle (a plurality of single core fibers) is an example of an “outgoing element”.

Alternatively, it is also possible to guide each of a plurality of lights emitted from the multi-core fiber 1 (a plurality of cores C _k ) to a light receiving element or a fiber bundle (all not shown) using the above-described coupling optical system 10. In this case, either the interval between the plurality of light receiving elements (the distance between the centers of the light receiving surfaces of adjacent light receiving elements) or the interval between the plurality of single core fibers is the interval between the plurality of cores C _k of the multicore fiber 1. Arranged to be wider than P. Here, the multi-core fiber 1 is an example of an “emission side element”. The light receiving element or the fiber bundle is an example of the “incident side element”.

In this case, the imaging optical system 14 has a function of guiding each light from the core C _k of the multi-core fiber 1 to the corresponding reflecting element 12. That is, here, the imaging optical system 14 corresponds to a “relay lens optical system”.

Furthermore, in this case, the relay lens system 11 has a function of condensing the light reflected by the reflecting element 12 onto a light receiving element or a single core fiber forming a fiber bundle. That is, here, the relay lens system 11 corresponds to the “imaging optical system”.

[Action / Effect]
The operation and effect of this embodiment will be described.

The coupling structure of the multicore fiber 1 according to the present embodiment includes an optical element, the multicore fiber 1, and a coupling optical system 10. The optical element includes any one of a plurality of light sources D _k , a plurality of light receiving elements, and a fiber bundle obtained by bundling a plurality of single core fibers. In the multi-core fiber 1, a plurality of cores C _k are covered with a clad 2. The coupling optical system 10 is disposed between the optical element and the multicore fiber 1, and optically couples the optical element and the multicore fiber 1. The interval p between a plurality of light sources D _k, one of the intervals between intervals and a plurality of single-core fiber among the plurality of light receiving elements, wider than the interval P between the plurality of cores C _k of the multicore fiber 1 It is arranged as follows. The coupling optical system 10 includes a reflective element 12 and an imaging optical system 14. The reflection element 12 has a reflection surface 12 a that reflects light emitted from the emission-side element that is one of the optical element and the multi-core fiber 1. The imaging optical system 14 causes the light reflected by the reflecting element 12 to enter the other incident side element.

As described above, the light emitted from the emission side element (for example, the plurality of light sources D _k ) can be guided to the corresponding incident side element (for example, the core C _{k of the} multicore fiber 1) via the reflection element 12. Therefore, it is possible to widely than the interval P between the plurality of cores C _k intervals (e.g. spacing p between a plurality of light sources D _k) of the multi-core fiber 1 between the optical elements. In this case, and the physical interference between the optical element according to the size of the optical element (e.g. a light source D _k), it is not causing a decrease in coupling efficiency due to the influence of heat and electric noise which the optical element (e.g. a light source D _k) emitted. That is, when the multi-core fiber 1 and another optical element are coupled, a decrease in coupling efficiency can be suppressed.

Also, if the outgoing side elements or entrance side element according to the present embodiment comprises a plurality of light sources D _k or the plurality of light receiving elements, at least two of the plurality of light sources D _k or the plurality of light receiving elements, on the same plane Has been placed.

Thus, by arranging a plurality of light sources D _k (or a plurality of light receiving elements), the configuration can be simplified. Further, the position adjustment of the light source D _k , the relay lens system 11 and the reflection element 12 can be performed before the multi-core fiber 1 and the optical element are coupled. Therefore, assembly of the coupling optical system 10 is facilitated.

Further, the coupling optical system 10 according to the present embodiment has a relay lens optical system (relay lens system 11). The relay lens optical system guides the light emitted from the emission side element to the imaging optical system 14. Then, by moving any of the exit side element, the entrance side element, the relay lens optical system, and the reflection element, it is possible to adjust the position of the exit side element and the entrance side element.

In this case, it is possible to perform position adjustment when light from the emission side element (for example, the light source D _k ) is incident on the incident side element (for example, the multi-core fiber 1). Therefore, the coupling efficiency can be improved.

<Variation 1 of the first embodiment>
Next, with reference to FIG. 4, the coupling structure of the multi-core fiber 1 according to a modification of the first embodiment will be described. FIG. 4 is a sectional view in the axial direction of the coupling optical system 10, the light source _Dk, and the multi-core fiber 1. As shown in FIG. FIG. 4 shows only three light sources (D ₁ , D ₂ , D ₅ ) corresponding to the three cores (C ₁ , C ₂ , C ₅ ) of the multi-core fiber 1.

In the first embodiment, the configuration having one convex lens as the imaging optical system 14 has been described, but the imaging optical system 14 is not limited to this configuration. The imaging optical system 14 may have a configuration having a plurality of microlenses M _k (k = 1 to n).

Microlens M _k is provided by the number equal to the cores C _k of the multi-core fiber 1. In this modification, microlenses M ₁ to M ₇ corresponding to the cores C ₁ to C ₇ are provided (in FIG. 4, the micro lenses M ₁ and M ₂ corresponding to the cores C ₁ , C ₂ , and C ₅ are provided. , it shows only the _{M 5).} The plurality of microlenses _Mk are arranged in an array. Each microlens _Mk is installed such that its center is located on the optical axis of the corresponding core _Ck .

Thus, by using the microlens M _k as the imaging optical system 14, the light from the light source D _k or the like can be reliably guided to the core C _k (or the light from the core C _k can be reliably transmitted). Can be guided to a light receiving element). Therefore, the coupling efficiency can be improved when the multi-core fiber 1 and another optical element are coupled.

<Modification 2 of the first embodiment>
Next, with reference to FIG. 5, the modification of the reflective element 12 of 1st Embodiment is demonstrated. FIG. 5 is a perspective view of the reflecting member 15.

In the first embodiment, the configuration in which the six reflecting elements 12 corresponding to the light sources D ₂ to D ₇ are individually provided has been described. On the other hand, it is also possible to use a reflecting member 15 in which a plurality of reflecting elements 12 are integrated. The reflection member 15 in this modification is an example of a “reflection element”.

The reflecting member 15 has a plurality of reflecting surfaces 15a corresponding to the arrangement of the optical elements (for example, the light source D _k ). The reflecting surface 15 a reflects light from the optical element (for example, the light source D _k ) and guides it to the imaging optical system 14. In this modification, six reflecting surfaces 15a corresponding to the light sources D ₂ to D ₇ are provided. In the present modification, the reflecting member 15 is provided with a flat surface 15b. Plane 15b is configured to transmit light from the light source D _1.

In addition, although the reflective member 15 which integrated the six reflective elements 12 was demonstrated here, the structure which provides the two reflective members 15 which integrated the three reflective elements 12 may be sufficient, for example. That is, a plurality of reflecting members having two or more reflecting surfaces can be provided.

Moreover, the plane 15b portion, may be provided with a hole for passing light from the light source D _1. In that case, light from the light source D ₁ is not affected by the refractive index of the reflecting member 15 has. Therefore, it is possible to improve the coupling efficiency at the time of entering the corresponding core C _1.

As described above, even when the reflecting element 12 is formed of one member, the light emitted from the emitting side element (for example, the plurality of light sources D _k ) is converted into the corresponding incident side element (for example, the core C of the multicore fiber 1). _k ). Therefore, it is possible to widely than the interval P between the plurality of cores C _k intervals (e.g. spacing p between a plurality of light sources D _k) of the multi-core fiber 1 between the optical elements. In this case, and the physical interference between the optical element according to the size of the optical element (e.g. a light source D _k), it is not causing a decrease in coupling efficiency due to the influence of heat and electric noise which the optical element (e.g. a light source D _k) emitted. That is, when the multi-core fiber 1 and another optical element are coupled, a decrease in coupling efficiency can be suppressed. Furthermore, it is not necessary to individually adjust a plurality of reflective elements by forming the reflective elements from a single member. Therefore, it is easy to adjust the position of the reflective element. In addition, since the reflective element is formed of a single member, the coupling optical system can be reduced in size.

<Second Embodiment>
Next, the coupling structure of the multi-core fiber 1 according to the second embodiment will be described with reference to FIG. In the present embodiment, a structure in which a plurality of light sources D _k (k = 1 to n) and a multi-core fiber 1 are coupled by a coupling optical system 20 will be described. The number of light sources _Dk is the same as the number of cores of the multi-core fiber 1 to be coupled. FIG. 6 is a cross-sectional view in the axial direction of the coupling optical system 20, the light source D _k and the multi-core fiber 1. In FIG. 6, among the cores C _k having a rotationally symmetric structure or a three-dimensional structure around the optical axis of the core C ₁ , five cores (C ₁ to C ₅ ) and corresponding five light sources (D ₁ To D ₅ ), only _five microlenses (M ₁ to M ₅ ) are shown. Detailed description of the same configuration as the first embodiment may be omitted.

[Configuration of coupling optical system]
Coupling optics 20 is disposed between the light source D _k and a multi-core fiber 1, coupling the light source D _k and multi-core fiber 1 optically. The coupling optical system 20 includes a relay lens system 21, a reflecting member 22, and an imaging optical system 24.

The relay lens system 21 has a function of guiding the light emitted from the light source _Dk to the imaging optical system 24 (via the reflection member 22). As many relay lens systems 21 as the number of the light sources _Dk are provided. The relay lens system 21 includes one collimating lens. By the collimating lens, the light from the light source _Dk is guided to the imaging optical system 24 in a collimated state (via the reflecting element 12). The relay lens system 21 is an example of a “relay lens optical system”. Incidentally, the relay lens system 21 corresponding to the light source D ₁ is configured to direct directly to the imaging optical system 24 in a state where the light was collimated from the light source D _1.

The relay lens system 21 is not limited to a collimating optical system using a collimating lens. For example, a condensing optical system using a plurality of convex lenses may be used.

The reflecting member 22 is one member that reflects the light guided from the light source _Dk via the relay lens system 21 toward the imaging optical system 24. The reflecting member 22 is formed with a plurality of reflecting surfaces 22 a that reflect the light guided by the relay lens system 21. The reflection member 22 in the present embodiment is an example of a “reflection element”.

Each reflection surface 22a, of the light emitted from the light source D _k, so as to reflect at least two light is obliquely set with respect to the traveling direction of the plurality of the light emitted from the light source D _k. For example, the reflection surface 22 a located on the lower side in FIG. 6 reflects light from the light sources D ₃ and D ₅ toward the imaging optical system 24. The reflecting surface 22a, the structure of the core C _k (e.g., rotationally symmetric structure or conformation around the optical axis of the core C ₁₎ is installed so as to correspond to.

In the present embodiment, a distance between the optical axes α of the two light incident on one of the reflecting surfaces 22a, spacing P between the distance between the optical axes of the two light reflected by the reflecting surface 22a [alpha] '(core C _k Is equal). In this case, as the interval p of the plurality of light sources D _k is wider than the interval P between the plurality of cores C _k of the multi-core fiber 1, the positioning of the light source D _k is made.

The number of reflection surfaces 22a of the reflection member 22 is different depending on the arrangement of the plurality of light sources _Dk and the number of lights reflected by one reflection surface 22a. For example, when two light beams are reflected by one reflecting surface 22a, the reflecting surface 22a only needs to be provided by half the number of light sources _Dk . When the light source D ₁ is arranged on the optical axis of the core C ₁ as in the present embodiment, the light from the light source D ₁ passes through the reflecting member 22 and is guided to the imaging optical system 24. Accordingly, the reflecting surface 22a is may be provided by half of the number of other light sources D _k except light source D _1.

The reflecting surface 22a has a predetermined angle with respect to the optical axis of the corresponding core C _k. This angle is determined by the arrangement of the light source D _k , the core C _k (multi-core fiber 1), and the imaging optical system 24. That is, the angle of each reflecting surface 22a may be equal or different.

Incidentally, in the central portion of the reflecting member 22 may be provided with a hole for passing light from the light source D _1. In that case, the light from the light source D ₁ is not affected by the refractive index of the base material of the reflecting member 22. Therefore, it is possible to improve the coupling efficiency at the time of entering the corresponding core C _1.

It is also possible to move at least one of the multi-core fiber 1, the light source D _k , the relay lens system 21, and the reflecting member 22 perpendicular to the optical axis direction of the light source D _k (or the optical axis direction of the multi-core fiber 1). is there. In this case, it is possible to adjust the position when the light from the light source D _k is incident on the core C _k of the multi-core fiber 1. Further, the position of the light from the light source D _k can be individually adjusted with respect to the core C _k of the multi-core fiber 1. Thereby, the coupling efficiency can be improved.

The imaging optical system 24 has a function of condensing the light reflected by the reflecting member 22 and making it incident on the corresponding core _Ck . In the present embodiment, as an imaging optical system 24, the number of micro lenses M _k equals the number of cores C _k are arranged in an array. The microlens M ₁ also has a function of condensing light directly guided from the light source D ₁ and causing the light to enter the core C ₁ of the multicore fiber 1.

[How light travels]
Next, with reference to FIG. 6, how the light travels according to the present embodiment will be described. In the present embodiment, a configuration in which light is emitted from a plurality of light sources _Dk and guided to the multicore fiber 1 will be described. That is, the plurality of light sources _Dk in the present embodiment is an example of “emission-side element”. On the other hand, the multi-core fiber 1 in the present embodiment is an example of an “incident side element”.

First, light is emitted from each of the plurality of light sources D ₁ to D ₅ . The emitted light is incident on the corresponding relay lens system 21 while being diffused. The incident light is collimated by the relay lens system 21 and emitted to the reflecting member 22. The light from the light source D ₁ is directly by the relay lens system 21 is guided to the imaging optical system 24.

Each light emitted from the relay lens system 21 corresponding to the plurality of light sources D ₂ to D ₅ is reflected by the reflecting surface 22 a of the reflecting member 22 and guided to the imaging optical system 24. For example, the light emitted from the light sources D ₃ and D ₅ is reflected by one reflecting surface 22a and guided to the corresponding microlenses M ₃ and M ₅ .

Each light reflected by the reflection surface 22a is condensed by the imaging optical system 24, incident on the corresponding core C _k. For example, the light condensed by the microlens _M 3, _{M 5} is incident on the core _C 3, _{C 5} corresponding. The light from the light source D _1, except that through the reflecting member 22, similarly entering the core C _1.

Here, in the present embodiment, an example in which a plurality of lights emitted from a plurality of light sources _Dk are guided to the multicore fiber 1 via the coupling optical system 20 has been described, but the target for emitting the light is limited to this. Absent. For example, a fiber bundle (not shown) made up of a plurality of single core fibers is arranged between the plurality of light sources _Dk and the relay lens system 21, and the light from the plurality of light sources _Dk is indirectly guided to the multicore fiber 1. It is also possible. In this case, the interval between the plurality of single core fibers is arranged to be wider than the interval P between the plurality of cores C _k of the multicore fiber 1. Here, a fiber bundle (a plurality of single core fibers) is an example of an “outgoing element”.

Alternatively, it is possible to guide each of a plurality of lights emitted from the multi-core fiber 1 (a plurality of cores C _k ) to a light receiving element or a fiber bundle (all not shown) using the above-described coupling optical system 20. In this case, either the interval between the plurality of light receiving elements or the interval between the plurality of single core fibers is arranged to be wider than the interval P between the plurality of cores C _k of the multicore fiber 1. Here, the multi-core fiber 1 is an example of an “emission side element”. The light receiving element or the fiber bundle is an example of the “incident side element”.

In this case, the imaging optical system 24 has a function of guiding each light from the core C _k of the multi-core fiber 1 to the reflecting member 22 (reflecting surface 22a). That is, here, the imaging optical system 24 corresponds to a “relay lens optical system”.

Furthermore, in this case, the relay lens system 21 has a function of condensing the light reflected by the reflecting member 22 (reflecting surface 22a) onto a light receiving element or a single core fiber forming a fiber bundle. That is, here, the relay lens system 21 corresponds to the “imaging optical system”.

The reflecting surface 22a of the reflecting element (reflecting member 22) according to the present embodiment is arranged so as to reflect at least two lights out of the light emitted from the emitting side element (for example, the plurality of light sources D _k ) from the emitting side element. It is inclined with respect to the traveling direction of the emitted light.

In this way, even if the reflection element is formed of one member and at least two lights are reflected by one reflection surface 22a, the light emitted from the emission side element (for example, a plurality of light sources D _k ) it can be guided to the corresponding incident side element (e.g. core C _k of the multicore fiber _1). Therefore, it is possible to widely than the interval P between the plurality of cores C _k intervals (e.g. spacing p between a plurality of light sources D _k) of the multi-core fiber 1 between the optical elements. In this case, and the physical interference between the optical element according to the size of the optical element (e.g. a light source D _k), it is not causing a decrease in coupling efficiency due to the influence of heat and electric noise which the optical element (e.g. a light source D _k) emitted. When coupling the multi-core fiber 1 and another optical element, it is possible to suppress a decrease in coupling efficiency.

Furthermore, it is not necessary to individually adjust a plurality of reflective elements by forming the reflective elements from a single member. Therefore, the configuration can be simplified and the position of the reflective element can be easily adjusted. The light source in the optical axis and symmetrical position of the core C ₁ (e.g., D2 and D3, D4 and D5) it is also possible to arrange on the same plane. Therefore, the configuration can be simplified and the position of the optical element can be easily adjusted.

<Third Embodiment>
Next, with reference to FIG. 7, the coupling structure of the multi-core fiber 1 according to the third embodiment will be described. In the present embodiment, a structure in which a plurality of light sources D _k (k = 1 to n) and the multi-core fiber 1 are coupled by a coupling optical system 20 ′ will be described. The number of light sources _Dk is the same as the number of cores of the multi-core fiber 1 to be coupled. FIG. 7 is a cross-sectional view in the axial direction of the coupling optical system 20 ′, the light source D _k, and the multi-core fiber 1. In FIG. 7, among the cores C _k having a rotationally symmetric structure or a three-dimensional structure around the optical axis of the core C ₁ , nine cores (C ₁ to C ₉ ) and corresponding nine light sources (light sources D). ₁ to D ₉ ), only _nine microlenses (M ₁ to M ₉ ) are shown. Detailed description of the same configuration as that of the second embodiment may be omitted.

[Configuration of coupling optical system]
Coupling optics 20 'is positioned between the light source D _k and a multi-core fiber 1, coupling the light source D _k and multi-core fiber 1 optically. The coupling optical system 20 ′ includes a relay lens system 21, a reflecting member 25, and an imaging optical system 24. Since the relay lens system 21 and the imaging optical system 24 have the same configuration as in the second embodiment, detailed description thereof is omitted.

The reflecting member 25 is one member that reflects the light guided from the light source _Dk via the relay lens system 21 toward the imaging optical system 24. The reflecting member 25 is formed with a plurality of reflecting surfaces 25 a that reflect the light guided by the relay lens system 21. The reflecting member 25 in the present embodiment is an example of a “reflecting element”.

Each reflecting surface 25a is formed in a step shape. In the present embodiment, three steps are formed on one reflecting surface 25a. That is, four reflecting regions 251a to 254a are formed on one reflecting surface 25a. The reflection regions 251a to 254a reflect the light emitted from the light source _Dk toward the imaging optical system 24. For example, each of the reflection regions 251a to 254a located on the lower side in FIG. 7 receives light from the light sources D ₃ , D ₅ , D ₇ , and D ₉ and corresponding microlenses M ₃ , M ₅ , M ₇ , and M _9. Reflect towards. The reflecting surface 25a, the structure of the core C _k (e.g., rotationally symmetric structure or conformation around the optical axis of the core C ₁₎ is installed so as to correspond to.

In the present embodiment, the distance α between the optical axis of the incident light to the reflective region 251a ~ 254a, (equal to the spacing P between the core _{C k)} reflective regions 251a ~ 254a distance between the optical axes of the light reflected by the α' Is bigger than. Therefore, the distance p between the light sources _Dk can be made wider than the distance P between the cores _Ck . That is, as shown in FIG. 7, the light sources D _k (for example, the light sources D ₃ , D ₅ , D ₇ , and D ₉ ) corresponding to the one reflecting surface 25a can be arranged on the same plane.

The number of reflection surfaces 25a of the reflection member 25 varies depending on the arrangement of the plurality of light sources _Dk and the number of steps provided on one reflection surface 25a. For example, when the light source D ₁ is arranged on the optical axis of the core C ₁ as in the present embodiment, the light from the light source D ₁ passes through the reflecting member 25 and is guided to the imaging optical system 24. Further, when three steps are formed on one reflecting surface 25a, four reflecting regions are formed on one reflecting surface 25a. Accordingly, the reflecting surface 25a is may be provided by a quarter of the number of other light sources _{D k} except light source _{D 1.}

The reflection surface 25a (each reflection region) has a predetermined angle with respect to the optical axis of the corresponding core _Ck . This angle is determined by the arrangement of the light source D _k , the core C _k (multi-core fiber 1), and the imaging optical system 24. That is, the angle of each reflecting surface 25a may be equal or different.

Incidentally, in the central portion of the reflecting member 25 may be provided with a hole for passing light from the light source D _1. In that case, light from the light source D ₁ is not affected by the base material the refractive index of the reflecting member 25. Therefore, it is possible to improve the coupling efficiency at the time of entering the corresponding core C _1.

It is also possible to move at least one of the multi-core fiber 1, the light source D _k , the relay lens system 21, and the reflection member 25 perpendicularly to the optical axis direction of the light source D _k (or the optical axis direction of the multi-core fiber 1). is there. In this case, it is possible to adjust the position when the light from the light source D _k is incident on the core C _k of the multi-core fiber 1. Further, the position of the light from the light source D _k can be individually adjusted with respect to the core C _k of the multi-core fiber 1. Thereby, the coupling efficiency can be improved.

[How light travels]
Next, how the light travels according to the present embodiment will be described with reference to FIG. In the present embodiment, a configuration in which light is emitted from a plurality of light sources _Dk and guided to the multicore fiber 1 will be described. That is, the plurality of light sources _Dk in the present embodiment is an example of “emission-side element”. On the other hand, the multi-core fiber 1 in the present embodiment is an example of an “incident side element”.

First, light is emitted from each of the plurality of light sources D ₁ to D ₉ . The emitted light is incident on the corresponding relay lens system 21 while being diffused. The incident light is collimated by the relay lens system 21 and emitted to the reflecting member 25. The light from the light source D ₁ is directly by the relay lens system 21 is guided to the imaging optical system 24.

Each light emitted from the relay lens system 21 corresponding to the plurality of light sources D ₂ to D ₉ is reflected by the reflection regions 251 a to 254 a formed on the reflection surface 25 a of the reflection member 25 and guided to the imaging optical system 24. It is burned. For example, light emitted from the light sources D ₃ , D ₅ , D ₇ , and D ₉ is reflected by the reflection regions 251a to 254a and guided to the corresponding microlenses M ₃ , M ₅ , M ₇ , and M ₉ .

Each light reflected by the reflecting region 251a ~ 254a is condensed by the imaging optical system 24, incident on the corresponding core _{C k.} For example, the light condensed by the microlens _{_{_{M 3, M 5, M 7}}} , M 9 is incident on the corresponding core _{_{_{C 3, C 5, C 7}}} , C 9. The light from the light source D _1, except that through the reflecting member 25, similarly entering the core C _1.

Here, in this embodiment, an example has been described in which a plurality of lights emitted from a plurality of light sources _Dk are guided to the multicore fiber 1 via the coupling optical system 20 ′. However, the object to emit light is limited to this. I can't. For example, a fiber bundle (not shown) made up of a plurality of single core fibers is arranged between the plurality of light sources _Dk and the relay lens system 21, and the light from the plurality of light sources _Dk is indirectly guided to the multicore fiber 1. It is also possible. In this case, the interval between the plurality of single core fibers is arranged to be wider than the interval P between the plurality of cores C _k of the multicore fiber 1. Here, a fiber bundle (a plurality of single core fibers) is an example of an “outgoing element”.

Alternatively, it is possible to guide each of a plurality of lights emitted from the multi-core fiber 1 (a plurality of cores C _k ) to a light receiving element or a fiber bundle (all not shown) by using the above-described coupling optical system 20 ′. . In this case, either the interval between the plurality of light receiving elements or the interval between the plurality of single core fibers is arranged to be wider than the interval P between the plurality of cores C _k of the multicore fiber 1. Here, the multi-core fiber 1 is an example of an “emission side element”. The light receiving element or the fiber bundle is an example of the “incident side element”.

In this case, the imaging optical system 24 has a function of guiding each light from the core C _k of the multi-core fiber 1 to the reflecting member 25 (reflecting surface 25a). That is, here, the imaging optical system 24 corresponds to a “relay lens optical system”.

Furthermore, in this case, the relay lens system 21 has a function of condensing the light reflected by the reflecting member 25 (reflecting surface 25a) onto a light receiving element or a single core fiber forming a fiber bundle. That is, here, the relay lens system 21 corresponds to the “imaging optical system”.

The reflection surface 25a of the reflection element (reflection member 25) according to the present embodiment is formed in a step shape (reflection regions 251a to 254a).

As described above, even when the reflection element is formed of one member and the light is reflected by the step-like reflection surface 25a, the light emitted from the emission side element (for example, the plurality of light sources D _k ) is handled. The incident side element (for example, the core C _k of the multi-core fiber 1) can be guided. Therefore, it is possible to widely than the interval P between the plurality of cores C _k intervals (e.g. spacing p between a plurality of light sources D _k) of the multi-core fiber 1 between the optical elements. In this case, and the physical interference between the optical element according to the size of the optical element (e.g. a light source D _k), it is not causing a decrease in coupling efficiency due to the influence of heat and electric noise which the optical element (e.g. a light source D _k) emitted. When coupling the multi-core fiber 1 and another optical element, it is possible to suppress a decrease in coupling efficiency.

Further, by making the reflection surface 25a stepped, the interval α between the optical axes of the light emitted from the emission side elements (for example, the plurality of light sources D _k ) is set between the optical axes of the light reflected by the reflection surface 25a. It can be made wider than the interval α ′. That is, since the interval between the optical elements (for example, the interval p between the plurality of light sources _Dk ) can be widened, the optical element corresponding to one reflection surface 25a can be formed on the same surface. Therefore, the configuration can be simplified and the position of the optical element can be easily adjusted. It is also possible to arrange the light sources in the optical axis and symmetrical position of the core C ₁ (e.g., D2 and D3, D4 and D5, etc.) on the same plane. Therefore, the configuration can be simplified and the position of the optical element can be easily adjusted.

<Modification of the first embodiment to the third embodiment>
In the present embodiment, the distance p between the light sources _Dk is described as being equal between the light sources, but the distance p between the light sources _Dk is different _{depending on} the arrangement of the cores Ck of the multi-core fiber 1 or the like. May be. For example, in the first embodiment, may be the distance the light source D ₃ between the light source D ₂ and the light source D ₃ and the spacing between the light source D ₄ are different.

The interval p between the light sources _Dk only needs to be at least wider than the interval between the corresponding cores _Ck . In the second embodiment and the third embodiment, the optical axis distance α of the light from the light source D _k may be equal to or greater than the optical axis distance α ′ of the reflected light.

Further, the light from the light source D ₁ is reflected, may be provided with a reflecting surface to be incident on the core C ₁ of the multi-core fiber 1. This reflective surface may be formed integrally with the reflective element.

DESCRIPTION OF SYMBOLS 1 Multi-core fiber 1b End surface 2 Clad 2a End surface 10 Coupling optical system 11

Relay lens system

11a, 11b Convex lens 12 Reflective element 12a Reflective surface 13 Support member 13a Hole 14 Imaging optical system C _k core D _k light source E _k end surface

Claims

Any one of a plurality of light sources, a plurality of light receiving elements, and a fiber bundle obtained by bundling a plurality of single core fibers;
A multi-core fiber having a plurality of cores covered with a cladding;
A coupling optical system disposed between the optical element and the multi-core fiber to optically couple the optical element and the multi-core fiber;
A multi-core fiber coupling structure comprising:
Any one of the spacing between the plurality of light sources, the spacing between the plurality of light receiving elements, and the spacing between the plurality of single core fibers is arranged to be wider than the spacing between the plurality of cores of the multicore fiber,
The coupling optical system includes:
A reflective element having a reflective surface for reflecting light emitted from an output side element composed of one of the optical element and the multi-core fiber;
An imaging optical system for causing the light reflected by the reflecting element to enter an incident side element composed of the other; and
A multi-core fiber coupling structure characterized by comprising:
When the output side element or the incident side element is composed of the plurality of light sources or the plurality of light receiving elements, at least two of the plurality of light sources or the plurality of light receiving elements are arranged on the same plane. The multi-core fiber coupling structure according to claim 1.
The multi-core fiber coupling structure according to claim 1 or 2, wherein the reflective element is formed of at least one member having two or more reflective surfaces.
The reflection surface is provided obliquely with respect to the traveling direction of a plurality of lights emitted from the emission side element so as to reflect at least two lights out of the light emitted from the emission side element. The multi-core fiber coupling structure according to claim 3.
The multi-core fiber coupling structure according to claim 3, wherein the reflecting surface is formed in a stepped shape.
The multi-core fiber coupling structure according to any one of claims 1 to 5, wherein the imaging optical system has a configuration in which a plurality of microlenses are arranged in an array.
The coupling optical system includes:
A relay lens optical system for guiding the light emitted from the emission side element to the imaging optical system;
The position adjustment of the said output side element and the said incident side element is attained by moving any of the said output side element, the said incident side element, the said relay lens optical system, and the said reflection element. Item 7. A multi-core fiber coupling structure according to any one of Items 1 to 6.