Optical connection structure

Abstract

To provide an optical connection structure with which, while suitable for a high density wiring, it is possible to bend to a small radius of bend without impairing mechanical strength reliability.SOLUTION: The optical connection structure comprises: an optical fiber bundle that has a plurality of optical fibers including one core part and a clad part enclosing the core part, and a bundle part composed by bundling the first end side of the plurality of optical fibers into one, with each of the core parts exposed to the end face of the bundle part; and an optical element unit that has a plurality of optical elements arranged so as to be optically connected to each of the exposed core parts. Each of the plurality of optical fibers has an expanded part where the clad diameter of the clad part expands from the first end toward a second end on the opposite side to the first end, the clad diameter of each of the clad parts at the end face of the bundle part being 80 μm or less, the clad diameter of each of the clad parts on the second end side being 125 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical connection structure.

Background Art

[0002] For example, in an optical transceiver used in a data center, an optical connection structure connecting an optical element array and a multi-core fiber is adopted for miniaturization and high density (Patent Document 1). The optical element array is a light-emitting element array such as a vertical cavity surface emitting laser (VCSEL) array or a light-receiving element array such as a photodetector array. The multi-core fiber is arranged in a housing of a device on which an optical transceiver is mounted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A multi-core fiber has a plurality of core portions in a cross section perpendicular to the longitudinal direction and is suitable for high-density wiring. However, since the multi-core fiber has a large number of core portions, the cladding diameter is relatively large compared to a single-core fiber having one core portion in a cross section perpendicular to the longitudinal direction. As a result, when the multi-core fiber is bent to the same diameter (bending diameter), the strain generated is larger than that of the single-core fiber, so the mechanical strength reliability is reduced. Therefore, the multi-core fiber has a relatively large allowable bending diameter during arrangement, and there is a problem with respect to the miniaturization of the device to be arranged.

[0005] [[ID=�9]]The present invention has been made in view of the above, and an object thereof is to provide an optical connection structure that is suitable for high-density wiring and can be bent to a small bending diameter without impairing mechanical strength reliability. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, one aspect of the present invention provides an optical connection structure comprising: a plurality of optical fibers having one core portion and a cladding portion surrounding the core portion; a bundle portion formed by bundling the first ends of the plurality of optical fibers together, wherein each of the core portions is exposed at the end face of the bundle portion; and an optical element unit having a plurality of optical elements arranged to be optically connected to each of the exposed core portions, wherein each of the plurality of optical fibers has an expanding portion in which the cladding diameter of the cladding portion increases from the first end to the second end opposite to the first end, the cladding diameter of each of the cladding portions at the end face of the bundle portion is 80 μm or less, and the cladding diameter of each of the cladding portions at the second end is 125 μm or less.

[0007] The cladding diameter of each of the cladding portions at the second end may be 60 μm or more.

[0008] One aspect of the present invention is an optical connection structure comprising: a plurality of optical fibers having one first core portion and a first cladding portion surrounding the first core portion; a bundle portion formed by bundling the first ends of the plurality of optical fibers together, wherein each of the first core portions is exposed at the end face of the bundle portion; and a multicore fiber having a plurality of second core portions optically connected to each of the exposed core portions, and a second cladding portion surrounding the plurality of second core portions, wherein each of the plurality of optical fibers has an expanded portion in which the cladding diameter of the first cladding portion increases from the first end toward the second end opposite to the first end, the cladding diameter of each of the first cladding portions at the end face of the bundle portion is 80 μm or less, and the cladding diameter of each of the first cladding portions at the second end is 125 μm or less.

[0009] The length of the multicore fiber may be 5 cm or less.

[0010] The cladding diameter of the second cladding portion of the multicore fiber may be 150 μm or more.

[0011] The core pitch of the multicore fiber may be 30 μm or more.

[0012] The core pitch of the multicore fiber may be 60 μm or less.

[0013] In the multicore fiber, the number of second cores may be 7, 19, or 37, and they may be arranged in a hexagonal close-packed configuration in a cross section perpendicular to the longitudinal direction.

[0014] In the multicore fiber described above, the number of second cores may be four, and they may be arranged in a square grid pattern in a cross section perpendicular to the longitudinal direction.

[0015] The system may further include an optical element unit having a plurality of optical elements arranged to be optically connected to each of the second core sections.

[0016] The multicore fiber and the optical element unit may be fixed in relative positions with an adhesive.

[0017] The multicore fiber may have a glass block attached to it, and the glass block may be bonded to the optical element unit with an adhesive. [Effects of the Invention]

[0018] The present invention provides the advantage of realizing an optical connection structure that is suitable for high-density wiring and can be bent to a small bending diameter without compromising mechanical strength reliability. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a schematic diagram of the optical connection structure according to Embodiment 1. [Figure 2] Figure 2 is a cross-sectional view of the optical fiber included in the optical fiber bundle shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the optical fiber bundle shown in Figure 1. [Figure 4] Figure 4 is a view showing the state of the optical fiber bundle shown in Figure 3 as seen from the tip side. [Figure 5] Figure 5 is a perspective view of the optical element unit shown in Figure 1. [Figure 6] Figure 6 is a schematic configuration diagram of the optical connection structure according to Embodiment 3. [Figure 7] Figure 7 is a cross-sectional view of the multi-core fiber shown in Figure 6.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the embodiments described below. Also, in each drawing, the same or corresponding components are appropriately given the same reference numerals. Further, it should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may be different from reality. There may also be parts where the dimensional relationships and ratios are different between the drawings. Also, for terms not specifically defined in this specification, the definitions and measurement methods in ITU-T G.650.1 and G.650.2 of the International Telecommunication Union (ITU) shall be followed.

[0021] (Embodiment 1) Figure 1 is a schematic configuration diagram of the optical connection structure according to Embodiment 1. The optical connection structure 100 includes an optical fiber bundle 10 and an optical element unit 20. The optical fiber bundle 10 and the optical element unit 20 are joined, for example, with an adhesive.

[0022] <Configuration of the optical fiber bundle> The optical fiber bundle 10 comprises seven optical fibers 11, which are multiple optical fibers. Figure 2 is a cross-sectional view of the optical fiber 11 along its longitudinal direction. The optical fiber 11 comprises a glass optical fiber portion 14 having one core portion 12 and a cladding portion 13 surrounding the core portion 12, and a resin coating portion 15 surrounding the outer circumference of the glass optical fiber portion 14. The optical fiber 11 is a single-core fiber. The optical fiber 11 has optical properties that conform to, for example, the definitions of ITU-T G.652, G.654, or G.657. The core diameter of the core portion 12 is, for example, 10 μm.

[0023] The glass optical fiber portion 14 is composed of a narrow-diameter portion 14a, an enlarged portion 14b, and a wide-diameter portion 14c, extending from the tip end to the base end. The tip is an example of a first end, and the base end is an example of a second end. The narrow-diameter portion 14a is a portion having a cladding diameter D2 smaller than the cladding diameter D1 of the wide-diameter portion 14c. The enlarged portion 14b is a portion where the cladding diameter tapers from D2 to D1, extending from the narrow-diameter portion 14a at the tip end to the wide-diameter portion 14c at the base end. The cladding diameter D2 is 80 μm or less, and the cladding diameter D1 is 125 μm or less.

[0024] The resin coating portion 15 is removed from the outer circumference of the small diameter portion 14a, the outer circumference of the enlarged portion 14b, and a portion of the outer circumference of the enlarged portion 14b side of the large diameter portion 14c.

[0025] Such an optical fiber 11 can be manufactured, for example, by removing the resin coating portion 15 at the tip of a single-mode optical fiber used for optical communication, and removing a part of the cladding portion 13 by etching or the like to form a narrow-diameter portion 14a and an enlarged portion 14b.

[0026] Figure 3 is a cross-sectional view of the optical fiber bundle 10 along its longitudinal direction. Figure 4 is a view of the optical fiber bundle 10 shown in Figure 3 from the tip side. The optical fiber bundle 10 includes a bundle portion 16 formed by bundling together a portion of the narrow diameter portions 14a, which are the tip ends of seven optical fibers 11, in a hexagonal close-packed arrangement in a cross section perpendicular to the longitudinal direction. Each of the core portions 12 is exposed at the end face 17 of the bundle portion 16. As shown in Figure 4, the core portions 12 are arranged in a hexagonal close-packed arrangement at the end face 17. At the end face 17, the core pitch, which is the distance between the centers of adjacent core portions 12, is Λ1. In this embodiment, Λ1 is the same as the cladding diameter D2 at the end face 17. That is, Λ1 is 80 μm or less.

[0027] Furthermore, the optical fiber bundle 10 includes a capillary 18. The capillary 18 houses the bundle portion 16 and the portions of each optical fiber 11 other than the bundle portion 16, namely a part of the narrow-diameter portion 14a, an enlarged portion 14b, and a part of the wide-diameter portion 14c. The capillary 18 is composed of a narrow-diameter portion 18a, an enlarged portion 18b, and a wide-diameter portion 18c, from the tip end to the base end. The narrow-diameter portion 18a is a portion having an inner and outer diameter smaller than the inner and outer diameters of the wide-diameter portion 18c. The enlarged portion 14b is a portion in which the inner and outer diameters taper from the tip end to the base end. The length of the capillary 18 is, for example, 5 cm or less.

[0028] In the optical fiber bundle 10, the optical fibers 11 are joined together, or the optical fibers 11 and the capillary 18 are joined by adhesive or fusion.

[0029] <Configuration of the optical element unit> Figure 5 is a perspective view of the optical element unit 20 shown in Figure 1. The optical element unit 20 comprises seven optical elements 21, which are multiple optical elements. The optical elements 21 are, for example, light-emitting elements, light-receiving elements, and optical waveguides, and are arranged in a manner that optically connects each to the core portion 12 exposed on the end face 17 of the optical fiber bundle 10. Specifically, the optical elements 21 are arranged in a hexagonal close-packed arrangement. The arrangement pitch of the optical elements 21 is Λ2, where Λ2 is the same value as the core pitch Λ1 and the cladding diameter D2. That is, Λ2 is 80 μm or less. However, if the optical elements 21 are photoelectric elements such as light-emitting elements or light-receiving elements, it is preferable that Λ2 be 30 μm or more in order to secure space for electrical wiring.

[0030] In the optical connection structure 100 configured as described above, the cladding diameter D2 of the optical fiber 11 in the optical fiber bundle 10 is 125 μm or less, which is equivalent to or less than the cladding diameter of a typical optical fiber. Therefore, it is possible to bend it to a relatively small bending diameter without compromising mechanical strength reliability. Moreover, at the end face 17 of the bundle portion 16 of the optical fiber bundle 10, the cladding diameter D2 of the optical fiber 11 is 80 μm or less, which enables the realization of a narrow core pitch Λ1 suitable for high-density wiring. Furthermore, this makes it easier to miniaturize the device on which the optical connection structure 100 is mounted.

[0031] From the viewpoint of balancing mechanical strength reliability and small bending diameter, D1 should be 125 μm or less, but a preferred example is around 80 μm. Furthermore, from the viewpoint of connectivity with ordinary single-mode optical fibers, which are often connected to optical fiber 11, or connectivity with optical systems that have high compatibility with single-mode optical fibers, D1 is preferably 60 μm or more.

[0032] From the viewpoint of high-density wiring, D2 should be 80 μm or less, but 60 μm or less is more preferable, for example, around 40 μm. The same applies to Λ1 and Λ2 as to D2. Furthermore, as mentioned above, from the viewpoint of securing space for the electrical wiring of the optical element 21, it is preferable that D2 be 30 μm or more.

[0033] (Embodiment 2) Figure 6 is a schematic diagram of the optical connection structure according to Embodiment 2. The optical connection structure 200 comprises an optical fiber bundle 10, an optical element unit 20, a multicore fiber 30, and a glass capillary 40.

[0034] The optical fiber bundle 10 and the optical element unit 20 are the same as the corresponding elements in the optical connection structure 100, so their explanation will be omitted as appropriate. In the optical fiber bundle 10 of the optical connection structure 200, the core portion 12 of the optical fiber 11 is an example of a first core portion, and the cladding portion 13 is an example of a first cladding portion.

[0035] The glass capillary 40 has a hole 41 that can accommodate the entire length of the multicore fiber 30. The multicore fiber 30 is fixed to the glass capillary 40 with an adhesive or the like while its entire length is contained within the hole 41. The glass capillary 40 is an example of a glass block.

[0036] Figure 7 is a cross-sectional view of the multicore fiber 30 in a plane perpendicular to the longitudinal direction. The multicore fiber 30 comprises seven core portions 31 as a plurality of second core portions and a cladding portion 32 as a second cladding portion surrounding the seven core portions 31. The multicore fiber 30 has optical properties according to, for example, the definitions of ITU-T G.652, G.654, or G.657. The seven core portions 31 are arranged in a hexagonal close-packed arrangement in a cross-section perpendicular to the longitudinal direction, and each is optically connected to each of the seven core portions 12 exposed at the end face 17 of the optical fiber bundle 10.

[0037] The core pitch Λ3 of the core portion 31 in the multicore fiber 30 is the same as Λ1 and Λ2. That is, Λ3 may be 80 μm or less, but 60 μm or less is more preferable, for example, about 40 μm, and preferably 30 μm or more.

[0038] Furthermore, the cladding diameter D3 of the cladding portion 32 of the multicore fiber 30 is set to 150 μm or more in order to accommodate the seven core portions 31 in a hexagonal close-packed arrangement with the core pitch Λ3 described above.

[0039] The glass capillary 40 is bonded to the optical element unit 20 with adhesive. This fixes the relative positions of the multicore fiber 30 and the optical element unit 20 using adhesive. In this state, the optical elements 21 of the optical element unit 20 are arranged to optically connect to each of the core portions 31 of the multicore fiber 30.

[0040] In the optical connection structure 200 configured as described above, the cladding diameter D3 of the multicore fiber 30 is 150 μm or more. However, similar to the optical connection structure 100, the cladding diameter D1 of the optical fiber 11 in the optical fiber bundle 10 is 125 μm or less, so it is possible to bend it to a relatively small bending diameter without compromising mechanical strength reliability. Moreover, at the end face 17 of the bundle portion 16 of the optical fiber bundle 10, the cladding diameter D2 of the optical fiber 11 is 80 μm or less, so a narrow core pitch Λ1 suitable for high-density wiring can be realized. Furthermore, this makes it easier to miniaturize the device on which the optical connection structure 200 is mounted.

[0041] Furthermore, according to the inventors' findings, interposing a multicore fiber 30 between the optical fiber bundle 10 and the optical element unit 20 reduces connection loss compared to directly connecting the optical fiber bundle 10 and the optical element unit 20. One reason for this is that the positional accuracy of the core portion 31 of the multicore fiber 30 relative to the arrangement of the optical elements 21 in the optical element unit 20 is relatively high and easier to manufacture than the positional accuracy of the core portion 12 of the optical fiber bundle 10 relative to the arrangement of the optical elements 21. The connection loss between the core portion 31 of the multicore fiber 30 and the core portion 12 of the optical fiber bundle 10 can be made extremely small by performing fusion splicing.

[0042] Furthermore, if the optical element 21 is a light-emitting element, the mode field diameter of the core portion 31 of the multicore fiber 30 can be set to a value between the beam diameter of the light emitted by the optical element 21 and the mode field diameter of the core portion 12 of the optical fiber bundle 10, thereby reducing the component of connection loss caused by mode field mismatch.

[0043] Furthermore, the length of the multicore fiber 30 is preferably 5 cm or less in order to lower the height of the optical connection structure 200.

[0044] In the above embodiment, the number of cores 31 in the multicore fiber 30 is 7, and they are arranged in a hexagonal close-packed configuration in a cross section perpendicular to the longitudinal direction. However, the number is not limited to 7; for example, it could be 19 or 37. With a hexagonal close-packed configuration, more cores can be arranged within a cladding section of a certain cross-sectional area. For example, if the core pitch Λ3 is 40 μm, 19 cores can be arranged in a hexagonal close-packed configuration within a cladding section with a cladding diameter D3 of 240 μm. Similarly, the number of cores 12 in the optical fiber bundle 10 and the optical elements 21 in the optical element unit 20 is not limited to 7; they could be 19 or 37 in a hexagonal close-packed configuration.

[0045] Furthermore, in the above embodiment, the number of cores in the multicore fiber may be four, and they may be arranged in a square grid in a cross section perpendicular to the longitudinal direction. The number of cores in the optical fiber bundle and the optical elements in the optical element unit may also be four, and they may be arranged in a square grid. In particular, it is preferable that the number of optical elements in the optical element unit be four and arranged in a square grid, as this makes it easier to wire electrical connections to the optical elements. In this case, the core pitch of the core portion and the arrangement pitch of the optical elements may be 80 μm or less, but it is more preferable to be 60 μm or less, and preferably 30 μm or more.

[0046] Furthermore, the present invention is not limited by the embodiments described above. Configurations that appropriately combine the above-described components are also included in the present invention. Moreover, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the embodiments described above, and various modifications are possible. [Explanation of Symbols]

[0047] 10: Fiber optic bundle 11: Optical fiber 12, 31: Core section 13, 32: Clad section 14: Glass optical fiber section 14a, 18a: Small diameter part 14b, 18b: Enlarged section 14c, 18c: Large diameter part 15: Resin-coated part 16:Bundle part 17: End face 18: Capillary 20: Optical element unit 21: Optical element 30: Multicore fiber 40: Glass capillary 41 :hole 100, 200: Optical connection structure

Claims

1. An optical fiber bundle having a plurality of optical fibers each having a first core portion and a first cladding portion surrounding the first core portion, and a bundle portion formed by bundling the first ends of the plurality of optical fibers together, wherein each of the first core portions is exposed at the end face of the bundle portion, An optical element unit having a plurality of light-emitting optical elements arranged in such a manner that it is optically connected to each of the exposed first core portions, A multicore fiber having a plurality of second core portions provided between the optical fiber bundle and the optical element unit, each of which is optically connected to each of the exposed first core portions, and a second cladding portion surrounding the plurality of second core portions, wherein each of the second core portions is optically connected to each of the plurality of optical elements, Equipped with, Each of the plurality of optical fibers has an expanded portion in which the cladding diameter of the first cladding portion tapers from the first end to the second end opposite to the first end, the cladding diameter of each of the first cladding portions at the end face of the bundle is 80 μm or less, and the cladding diameter of each of the first cladding portions at the second end is 60 μm or more and 125 μm or less. In the multicore fiber described above, the second core portion has four cores, which are arranged in a square grid pattern in a cross section perpendicular to the longitudinal direction. The length of the multicore fiber is 5 cm or less. The mode field diameter of the second core portion of the multicore fiber is the value between the beam diameter of the light emitted by the optical element and the mode field diameter of the first core portion of the optical fiber bundle. The optical fiber bundle comprises the bundle portion and a capillary with a length of 5 cm or less that houses a portion of the narrow diameter portion of the multiple optical fibers other than the bundle portion, which is on the first end side of the enlarged portion and a portion of the wide diameter portion which is on the second end side of the enlarged portion and the enlarged portion, such that the portion of the narrow diameter portion and the portion of the wide diameter portion are parallel to each other. Optical connection structure.

2. The cladding diameter of the second cladding portion of the multicore fiber is 150 μm or more. The optical connection structure according to claim 1.

3. The core pitch of the multicore fiber is 30 μm or more. The optical connection structure according to claim 1 or 2.

4. The core pitch of the multicore fiber is 60 μm or less. The optical connection structure according to any one of claims 1 to 3.

5. The multicore fiber and the optical element unit are fixed in relative positions by adhesive. The optical connection structure according to any one of claims 1 to 4.

6. A glass block is attached to the multicore fiber, and the glass block is bonded to the optical element unit with an adhesive. The optical connection structure according to any one of claims 1 to 5.

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