Multi-core optical fiber and optical communication system

Abstract

To provide a multi-core optical fiber capable of reducing optical interference with a simple configuration.SOLUTION: The MCF 10 includes the first core 12, the second core 14, and the cladding layer 16, the 10c of the outer peripheral surface of the MCF 10 is exposed at the first end, and the first core end surface 12a is inclined from the first end toward the second end opposite to the first end in the axial direction Z as the first core end surface 12a extends toward the second core end surface 14a in the first widthwise direction X. The second core end surface 14a is inclined from the first end portion toward the second end portion in the axial direction Z as the second core end surface 14a extends from the second core end surface 12a toward the first core end surface LA in the first widthwise direction X.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multi-core optical fiber and an optical communication system. [Background technology]

[0002] In recent years, with the advancement of autonomous driving technology, the number of high-resolution cameras and sensors has been increasing. As a result, there is a demand for optical communication systems capable of transmitting large amounts of data within vehicles. Conventionally, optical communication modules that perform full-duplex optical communication, which allows simultaneous transmission and reception using a single optical fiber, have been known, and methods for reducing interference between transmitted light and received light have been disclosed.

[0003] Patent Document 1 discloses an optical communication module having a receptacle for inserting a plug attached to the end of a plastic optical fiber. In this optical communication module, an interference prevention section is formed around the tip of the plug and / or plastic optical fiber when the plug is inserted into the receptacle, preventing transmitted light or scattered light inside the optical communication module from coupling with a light receiving element. The plastic optical fiber has an expanded section at its end whose diameter is larger than the core diameter, and the interference prevention section is positioned so as to block light irradiated onto the expanded section from the optical component. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-101809 Summary of the Invention [Problem to be solved by the invention]

[0005] The optical communications module of Patent Document 1 reduces interference caused by near-end reflection, which occurs when transmitted light is reflected at the end face of the optical fiber when it enters the optical fiber, and interference caused by internally scattered light within the optical communications module. However, the optical communications module described in Patent Document 1 requires an expanded section to be formed at the end of the plastic optical fiber. It is difficult to process the expanded section with high precision, and the transmission area is limited. Therefore, high mounting precision and alignment precision may be required.

[0006] The present invention has been made in view of the problems inherent in the conventional techniques, and an object of the present invention is to provide a multi-core optical fiber and an optical communication system that are capable of reducing optical interference with a simple configuration. [Means for solving the problem]

[0007] A multi-core optical fiber according to an aspect of the present invention includes a first core, a second core, and cladding layers for the first and second cores. An outer circumferential surface of the multi-core optical fiber is exposed at a first end portion which is one end portion of the multi-core optical fiber in the axial direction. A fiber end face having a first core end face which is an end face of the first core and a second core end face which is an end face of the second core is provided at the first end portion of the multi-core optical fiber. The first core end face is inclined in the axial direction from the first end portion to a second end portion opposite to the first end portion as it progresses in a direction from the first core end face to the second core end face in a first width direction perpendicular to the axial direction. The second core end face is inclined in the axial direction from the first end portion to the second end portion as it progresses in a direction from the second core end face to the first core end face in the first width direction.

[0008] An optical communication system according to another aspect of the present invention includes a multi-core optical fiber, a first light-emitting element that outputs first transmitted light, and a light-receiving element that receives received light emitted from the multi-core optical fiber or a second light-emitting element that outputs second transmitted light. The first transmitted light emitted from the first light-emitting element passes through the cladding layer and is reflected by the first core end face. The received light is reflected by the second core end face, passes through the cladding layer, and is received by the light-receiving element. The second transmitted light emitted from the second light-emitting element passes through the cladding layer and is reflected by the second core end face. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a multi-core optical fiber and an optical communication system that can reduce optical interference with a simple configuration. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a side view showing an optical communication system according to a first embodiment. [Figure 2] 1 is a perspective view showing a first end portion of a multi-core optical fiber according to a first embodiment. [Figure 3] FIG. 2 is a front view showing a first end portion of the multi-core optical fiber according to the first embodiment. [Figure 4] FIG. 10 is a side view showing an optical communication system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the multi-core optical fiber and the optical communication system according to the present embodiment will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0012] [First embodiment] FIG. 1 is a side view showing an optical communication system 1 according to a first embodiment. FIG. 2 is a perspective view showing a first end portion of a multi-core optical fiber 10 according to the first embodiment. FIG. 3 is a front view showing a first end portion of the multi-core optical fiber 10 according to the first embodiment. In this specification, the first width direction (radial direction) is defined as the X direction, the second width direction which is a width direction (radial direction) perpendicular to the first width direction X is defined as the Y direction, and the axial direction perpendicular to the first width direction X and the second width direction Y is defined as the Z direction. As shown in FIGS. 1 and 2, the optical communication system 1 includes a multi-core optical fiber 10, a first light-emitting element 20, a first collecting lens 30, a second collecting lens 32, and a light-receiving element 40.

[0013] The multi-core optical fiber 10 includes a first core 12, a second core 14, and a cladding layer 16 for the first core 12 and the second core 14. The multi-core optical fiber 10 according to this embodiment is a two-core multi-core optical fiber having two cores. A first end portion, which is one end portion of the multi-core optical fiber 10 in the axial direction Z, is in a bare fiber state, and an outer circumferential surface 10c of the multi-core optical fiber 10 is exposed at the first end portion. Note that the diameter of the multi-core optical fiber 10 according to this embodiment is 125 μm, and the diameter of the first core 12 and the diameter of the second core 14 are 50 μm. However, these diameters and propagation modes are not particularly limited. The multi-core optical fiber 10 may be, for example, a single mode.

[0014] The first core 12 and the second core 14 are preferably made of glass. When the first core 12 and the second core 14 are made of glass, the transmission loss is small and the bandwidth is wide, making them suitable for medium-distance communication, long-distance communication, and high-speed communication. The glass used in the multi-core optical fiber 10 may be silica glass. However, the first core 12 and the second core 14 may also be made of other materials such as plastic.

[0015] The cladding layer 16 has a refractive index lower than that of the first core 12 and the second core 14, and covers the outer peripheral surfaces of the first core 12 and the second core 14. The cladding layer 16 has the role of reflecting light at the outer peripheral surfaces of the first core 12 and the second core 14, and confining the light within the first core 12 and the second core 14. The cladding layer 16 is preferably made of glass. When the cladding layer 16 is made of glass, it has high heat resistance, and can prevent the performance of the multi-core optical fiber 10 from being deteriorated by heat or the like.

[0016] The end of the multi-core optical fiber 10 has a groove cut into a V shape when viewed from the second width direction Y of the multi-core optical fiber 10. When viewed from the second width direction Y, the groove has a shape with a depression in the center, and includes two convex portions provided at both ends in the first width direction X, and a concave portion sandwiched between the two convex portions.

[0017] A fiber end face 11 is provided at a first end, which is one end in the axial direction Z, of the multi-core optical fiber 10. The fiber end face 11 includes a first fiber end face 11a and a second fiber end face 11b. The first fiber end face 11a and the second fiber end face 11b are flat, smooth surfaces and have a semicircular shape. A groove is formed by the first fiber end face 11a and the second fiber end face 11b. When viewed from the axial direction Z, the fiber end face 11 is divided into the first fiber end face 11a and the second fiber end face 11b by a first center line CL1, and the first fiber end face 11a and the second fiber end face 11b are adjacent to each other in the first width direction X. When viewed from the axial direction Z, the first fiber end face 11a and the second fiber end face 11b are symmetrical with respect to the first center line CL1.

[0018] The multi-core optical fiber 10 has a first outer peripheral edge 11d and a second outer peripheral edge 11e, which are divided in a first width direction X perpendicular to the axial direction Z by a center line CL1 passing through a central axis CA1 of the multi-core optical fiber 10, when viewed from the axial direction Z. The first fiber end face 11a is formed by being surrounded by the first center line CL1 and the first outer peripheral edge 11d, which is a part of the outer peripheral edge 11c. A line segment connecting a point on the first outer peripheral edge 11d and the central axis CA1 inclines from the first end portion in the axial direction Z toward a second end portion (not shown) opposite the first end portion as it extends from the first outer peripheral edge 11d toward the central axis CA1. The second fiber end face 11b is formed by being surrounded by the first center line CL1 and the second outer peripheral edge 11e, which is a part of the outer peripheral edge 11c. The line segment connecting a point on the second outer peripheral edge 11e and the central axis CA1 inclines from the first end in the axial direction Z toward the second end (not shown) opposite the first end as it moves from the second outer peripheral edge 11e toward the central axis CA1.

[0019] The fiber end face 11 has a first core end face 12a which is the end face of the first core 12, and a second core end face 14a which is the end face of the second core 14. The first core end face 12a is provided at the first fiber end face 11a, and the second core end face 14a is provided at the second fiber end face 11b. A first center line CL1 separates the first fiber end face 11a, which is the region where the first core end face 12a exists, from the second fiber end face 11b, which is the region where the second core end face 14a exists.

[0020] The first core end face 12a is inclined in the first width direction X in a direction from the first core end face 12a toward the second core end face 14a so as to progress from the first end toward the second end opposite the first end in the axial direction Z. That is, the first core end face 12a is inclined in the first width direction X in a direction from the first outer peripheral edge 11d toward the first center line CL1 so as to progress from the first end toward the second end opposite the first end in the axial direction Z. Furthermore, the second core end face 14a is inclined in the first width direction X in a direction from the second core end face 14a toward the first core end face 12a so as to progress from the first end toward the second end in the axial direction Z. That is, the second core end face 14a is inclined in the first width direction X in a direction from the second outer peripheral edge 11e toward the first center line CL1 so as to progress from the first end toward the second end in the axial direction Z.

[0021] The first core end face 12a and the second core end face 14a are arranged so as not to overlap when viewed from the first width direction X. Specifically, the first fiber end face 11a is divided by a second center line CL2 that passes through the central axis CA1 and is perpendicular to the first center line CL1 into a first region 11a1 where the first core end face 12a is present and a second region 11a2 where the first core end face 12a is not present. The second fiber end face 11b is also divided by the second center line CL2 into a third region 11b1 where the second core end face 14a is present and a fourth region 11b2 where the second core end face 14a is not present. When viewed from the axial direction Z, the first region 11a1 and the fourth region 11b2 are adjacent to each other in the first width direction X, and the second region 11a2 and the third region 11b1 are adjacent to each other in the first width direction X.

[0022] The included angle of the convex portion at the first intersection P1 between the second center line CL2 and the first outer peripheral edge 11d is 45° when viewed from the second width direction Y. The included angle of the convex portion at the second intersection P2 between the second center line CL2 and the second outer peripheral edge 11e is 45° when viewed from the second width direction Y. The angle formed by the first fiber end face 11a and the exposed surface of the second fiber end face 11b is 90°. The included angle formed by the first center line CL1 and a third center line CL3 passing through the central axis CA2 of the first core 12 and the central axis CA3 of the second core 14 is 45°. However, these included angles may be changed as appropriate within a range of, for example, approximately ±10°.

[0023] The multi-core optical fiber 10 can be obtained, for example, by processing the end face into a V-shape. At this time, in order to suppress vibrations and the like that occur during processing when directly processing a bare fiber, the end face may be processed into a V-shape in a state where the multi-core optical fiber 10 is inserted into a ferrule. The groove can be formed by processing the ferrule into which the multi-core optical fiber 10 is inserted with a diamond blade rotator having a 90° cutting portion. Then, the processed multi-core optical fiber 10 can be removed from the ferrule, and the first end of the multi-core optical fiber 10 can be fixed and used.

[0024] A reflective film may be provided on the surfaces of the first core end face 12a and the second core end face 14a. In this embodiment, a reflective member (not shown) that reflects the first transmitted light TL1 and the received light RL (described later) may be provided in the groove, and the reflective member may be disposed on the surfaces of the first core end face 12a and the second core end face 14a to reflect the first transmitted light TL1 and the received light RL. However, the reflection of the first transmitted light TL1 and the received light RL can also be promoted by providing a reflective film on the surfaces of the first core end face 12a and the second core end face 14a. The reflective film may contain a metal such as gold. The reflective film can be formed by coating the surfaces of the first core end face 12a and the second core end face 14a with a metal. The reflective film may be provided on the first fiber end face 11a, including the first core end face 12a. Alternatively, the reflective film may be provided on the second fiber end face 11b, including the second core end face 14a.

[0025] A first core 12 and a cladding layer 16 are arranged between the first core end face 12a and the outer peripheral surface 10c of the multi-core optical fiber 10. In addition, a second core 14 and a cladding layer 16 are arranged between the second core end face 14a and the outer peripheral surface 10c of the multi-core optical fiber 10. In the optical communication system 1 according to this embodiment, a first transmitted light TL1 passes through the first core 12, and a received light RL passes through the second core 14.

[0026] Specifically, the first transmitted light TL1 enters the cladding layer 16 from the outer peripheral surface 10c of the multi-core optical fiber 10, and the first transmitted light TL1 that has passed through the cladding layer 16 is reflected by the first core end face 12a. The first transmitted light TL1 that has been reflected by the first core end face 12a passes through the first core 12 and is transmitted from the first end to the second end of the multi-core optical fiber 10. On the other hand, the received light RL that has been transmitted from the second end to the first end of the multi-core optical fiber 10 is reflected by the second core end face 14a. The received light RL that has been reflected by the second core end face 14a enters the cladding layer 16 from the second core 14, and the received light RL that has passed through the cladding layer 16 is emitted from the outer peripheral surface 10c of the multi-core optical fiber 10.

[0027] In the optical communication system 1 according to this embodiment, the first light-emitting element 20 outputs a first transmission light TL1 corresponding to an input electrical signal. The first transmission light TL1 emitted from the first light-emitting element 20 is condensed by a first condensing lens 30. The first transmission light TL1 emitted from the first light-emitting element 20 passes through the cladding layer 16 and is reflected by the first core end face 12a. The first transmission light TL1 reflected by the first core end face 12a is transmitted through the first cores 12 from the first end to the second end of the multi-core optical fiber 10.

[0028] On the other hand, the received light RL traveling from the second end to the first end of the multi-core optical fiber 10 through the second core 14 is collected by the second collecting lens 32, reflected by the second core end face 14a, passes through the cladding layer 16, and is received by the photodetector 40. The photodetector 40 receives the received light RL emitted from the multi-core optical fiber 10 and converts it into an electrical signal corresponding to the received light RL.

[0029] The light output from the first light-emitting element 20 may be laser light. The first light-emitting element 20 may include a laser diode (LD) or a light-emitting diode (LED). The laser diode may include a vertical-cavity surface-emitting laser (VCSEL). The first light-emitting element 20 may also be formed using silicon photonics technology.

[0030] The light receiving element 40 is an O / E conversion element that converts an optical signal into an electrical signal, and may include, for example, a photodiode.

[0031] The wavelength of the first transmitted light TL1 output from the first light-emitting element 20 and the wavelength of the received light RL received by the light-receiving element 40 may be the same or different.

[0032] [Second embodiment] Next, an optical communication system 1 according to a second embodiment will be described with reference to Fig. 4. As shown in Fig. 4, the optical communication system 1 according to this embodiment includes a multi-core optical fiber 10, a first light-emitting element 20, a first collecting lens 30, a third collecting lens 34, and a second light-emitting element 25. Compared to the optical communication system 1 according to the first embodiment, the optical communication system 1 according to this embodiment has the light-receiving element 40 replaced with the second light-emitting element 25. Unless otherwise specified, the optical communication system 1 according to this embodiment is the same as the optical communication system 1 according to the first embodiment, and therefore description thereof will be omitted.

[0033] The multi-core optical fiber 10 includes first cores 12, second cores 14, and cladding layers 16 for the first cores 12 and second cores 14, similar to the first embodiment.

[0034] In the optical communication system 1 according to this embodiment, the first light-emitting element 20 outputs a first transmission light TL1 corresponding to an input electrical signal. The first transmission light TL1 emitted from the first light-emitting element 20 is condensed by a first condensing lens 30. The first transmission light TL1 emitted from the first light-emitting element 20 passes through the cladding layer 16 and is reflected by the first core end face 12a. The first transmission light TL1 reflected by the first core end face 12a is transmitted through the first cores 12 from the first end of the multi-core optical fiber 10 toward the second end opposite to the first end.

[0035] On the other hand, in the optical communication system 1 according to this embodiment, the second light-emitting element 25 outputs a second transmission light TL2 corresponding to the input electrical signal. The second transmission light TL2 emitted from the second light-emitting element 25 is condensed by the third condenser lens 34. The second transmission light TL2 emitted from the second light-emitting element 25 enters the cladding layer 16 from the outer peripheral surface 10c of the multi-core optical fiber 10, passes through the cladding layer 16, and is reflected by the second core end face 14a. The second transmission light TL2 reflected by the second core end face 14a is transmitted through the second core 14 from the first end of the multi-core optical fiber 10 toward the second end opposite to the first end.

[0036] The wavelength of the first transmitted light TL1 output from the first light-emitting element 20 and the wavelength of the second transmitted light TL2 output from the second light-emitting element 25 may be the same or different.

[0037] As described above, the multi-core optical fiber 10 according to this embodiment includes the first cores 12, the second cores 14, and the cladding layers 16 of the first cores 12 and the second cores 14. At a first end portion which is one end portion of the multi-core optical fiber 10 in the axial direction Z, the outer circumferential surface 10c of the multi-core optical fiber 10 is exposed. At the first end portion of the multi-core optical fiber 10, a fiber end face 11 is provided which has a first core end face 12a which is an end face of the first core, and a second core end face 14a which is an end face of the second core 14. The first core end face 12a is inclined in the axial direction Z from the first end portion toward the second end portion opposite to the first end portion as it progresses in the direction from the first core end face 12a toward the second core end face 14a in a first width direction X perpendicular to the axial direction Z. The second core end face 14a is inclined in the first width direction X from the second core end face 14a toward the first core end face 12a, and inclined in the axial direction Z from the first end to the second end.

[0038] The multi-core optical fiber 10 according to this embodiment includes a first core 12 and a second core 14, an outer circumferential surface 10c of the multi-core optical fiber 10 is exposed, and the first core end face 12a and the second core end face 14a are inclined. Therefore, by transmitting and receiving light between the outer circumferential surface 10c of the multi-core optical fiber 10 and the first core end face 12a or the second core end face 14a, it is possible to reduce optical interference with a simple configuration.

[0039] The first core end faces 12a and the second core end faces 14a may be arranged so as not to overlap when viewed from the first width direction X. With this configuration, for example, even if part of the first transmission light TL1 is not reflected by the first core end faces 12a and exits the first core 12 to enter the air layer, it is possible to prevent the first transmission light TL1 from entering the second core 14 from the second core end faces 14a. This makes it possible to further reduce optical interference.

[0040] The first core 12, the second core 14, and the cladding layer 16 may be made of glass. Such a configuration provides high heat resistance and can prevent the performance of the multi-core optical fiber 10 from being degraded by heat or the like. Furthermore, when the first core 12 and the second core 14 are made of glass, the transmission loss is small and the bandwidth is wide, making it suitable for medium-distance communication, long-distance communication, and high-speed communication.

[0041] A reflective film may be provided on the surfaces of the first core end faces 12 a and the second core end faces 14 a. Such a configuration can promote the reflection of the first transmitted light TL1 and the received light RL at the first core end faces 12 a and the second core end faces 14 a.

[0042] Moreover, the optical communication system 1 according to this embodiment includes a multi-core optical fiber 10 and a first light-emitting element 20 that outputs a first transmitted light TL1. The optical communication system 1 includes a light-receiving element 40 that receives received light RL emitted from the multi-core optical fiber 10, or a second light-emitting element 25 that outputs second transmitted light TL2. The first transmitted light TL1 emitted from the first light-emitting element 20 passes through the cladding layer 16 and is reflected by the first core end face 12a. The received light RL is reflected by the second core end face 14a, passes through the cladding layer 16, and is received by the light-receiving element 40. The second transmitted light TL2 emitted from the second light-emitting element 25 passes through the cladding layer 16 and is reflected by the second core end face 14a.

[0043] According to the optical communication system 1 of this embodiment, by using the multi-core optical fiber 10, the first light-emitting element 20, and the light-receiving element 40, bidirectional transmission of the first outgoing light TL1 and the incoming light RL becomes possible using a single multi-core optical fiber 10.

[0044] Moreover, according to the optical communication system 1 of this embodiment, by using the multi-core optical fiber 10, the first light-emitting element 20, and the second light-emitting element 25, it is possible to transmit the first transmission light TL1 and the second transmission light TL2 using one multi-core optical fiber 10. Therefore, according to the optical communication system 1 of this embodiment, it is possible to perform co-directional transmission with increased transmission capacity. Furthermore, according to the optical communication system 1 of this embodiment, it is possible to transmit different wavelengths in the same direction using the first core 12 and the second core 14, thereby eliminating the need for an expensive wavelength selection filter.

[0045] Furthermore, since the optical communication system 1 according to the present embodiment uses the multi-core optical fiber 10, interference between the first transmitted light TL1 and the received light RL or the second transmitted light TL2 can be reduced without performing complex control or using an optical system for complex control. This makes it possible to simplify and reduce the cost of the optical communication system 1. Furthermore, since the optical system can be simplified, the degree of freedom in arranging the first light-emitting element 20 and the light-receiving element 40 or the second light-emitting element 25 is improved. This can contribute to miniaturization of an optical transceiver including the first light-emitting element 20 and the light-receiving element 40, and an optical transmitter including the first light-emitting element 20 and the second light-emitting element 25.

[0046] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0047] 1 Optical communication systems 10 Multi-core optical fiber 10c Outer surface 11 Fiber end face 11d First outer edge 11e Second outer edge 12 First Core 12a First core end face 14 Second Core 14a Second core end face 16 Cladding layer 20 First light-emitting element 25 Second light-emitting element 40 Photodetector CA1 center axis CL1 center line TL1 First transmitted light TL2 Second transmission light RL receiving light X 1st width direction Y Second width direction Z axis direction

Claims

1. A first core; A second core; cladding layers of the first core and the second core; A multi-core optical fiber comprising: an outer circumferential surface of the multi-core optical fiber is exposed at a first end portion which is one end portion in an axial direction of the multi-core optical fiber; a fiber end face having a first core end face that is an end face of the first core and a second core end face that is an end face of the second core is provided at the first end of the multi-core optical fiber, the first core end surface is inclined in the axial direction from the first end portion to a second end portion opposite to the first end portion as the first core end surface advances in a direction from the first core end surface to the second core end surface in a first width direction perpendicular to the axial direction, the second core end face is inclined in the axial direction from the first end face to the second end face as it progresses in the first width direction from the second core end face to the first core end face.

2. The multi-core optical fiber according to claim 1 , wherein the first core end face and the second core end face are arranged so as not to overlap when viewed from the first width direction.

3. The multi-core optical fiber according to claim 1 , wherein a reflective film is provided on a surface of the first core end face and the second core end face.

4. The multi-core optical fiber according to claim 1; a first light-emitting element that outputs a first transmitted light; a light receiving element that receives the received light emitted from the multi-core optical fiber, or a second light emitting element that outputs a second transmitted light; Equipped with the first transmitted light emitted from the first light-emitting element passes through the cladding layer and is reflected by the first core end face, the received light is reflected at the second core end face, passes through the cladding layer, and is received by the light receiving element, the second transmission light emitted from the second light-emitting element passes through the cladding layer and is reflected by the second core end face.

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