Fan-in / fan-out devices

Abstract

The fan-in / fan-out device has an isolation function and reduces losses. [Solution] A fan-in / fan-out device comprising a multicore fiber having at least a first core and a second core, a first single-core fiber, and a second single-core fiber, wherein the first core and the core of the first single-core fiber are optically connected by a first optical path, and the second core and the core of the second single-core fiber are optically connected by a second optical path, wherein a first optical beam in the first optical path propagates from the first core side to the core side of the first single-core fiber, and a second optical beam in the second optical path propagates from the core side of the second single-core fiber to the second core side, and comprising a multicore fiber side lens, a first single-core fiber side lens, a second single-core fiber side lens, a first isolator unit, and a second isolator unit.

Description

Technical Field

[0001] The present invention relates to a fan-in / fan-out device. In particular, it relates to a space-coupled fan-in / fan-out device that includes a multi-core fiber and a plurality of single-core fibers, and optically couples the two using a lens.

Background Art

[0002] Communication traffic demand via the Internet has been increasing year by year, and further high-speed and large-capacity optical communication is desired. Conventionally, in order to meet this demand, the increase in transmission capacity has been promoted by technologies such as wavelength division multiplexing (WDM) and digital coherent technology.

[0003] In recent years, as a new multiplexing technology, space division multiplexing (SDM) technology using a multi-core fiber has attracted attention. According to the SDM technology, it is said that higher speed and larger capacity can be achieved. With the progress of research and development of the SDM technology, the demand for fan-in / fan-out (hereinafter sometimes also referred to as "FI / FO") devices has been increasing. The FI / FO device is an optical device that includes a multi-core fiber and a plurality of single-core fibers, and optically couples the two.

[0004] Examples of FI / FO devices include space-coupled, fiber bundle-type, melt-stretched, and planar light waveguide-type FI / FO devices. The space-coupled FI / FO device is characterized in that it optically couples a multi-core fiber and a plurality of single-core fibers using a lens (including a glass block, etc.). The space-coupled FI / FO device has an advantage that it can reduce the insertion loss compared to fiber bundle-type, melt-stretched, and planar light waveguide-type FI / FO devices.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 6554891 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Incidentally, in spatially coupled FI / FO devices, a light beam emitted from the end face of a single-core fiber core may be reflected at the end face of a multi-core fiber, and the reflected light may enter the core of the single-core fiber. Similarly, in spatially coupled FI / FO devices, a light beam emitted from the end face of a multi-core fiber core may be reflected at the end face of a single-core fiber, and the reflected light may enter the core of the multi-core fiber. Such reflected light is generally called "reflected backlight." Reflected backlight can degrade the optical properties of the signal light by entering the transmitting communication device via the multi-core or single-core fiber, or by undergoing multiple reflections.

[0007] For this reason, optical isolators (sometimes simply called "isolators") are sometimes used in conjunction with FI / FO devices. Optical isolators operate by allowing light beams emitted from the core of a multicore fiber (or single-core fiber) and propagating in one direction (forward), while suppressing light beams propagating in the reverse direction from entering the core of the multicore fiber (or single-core fiber).

[0008] Here, when multiple light beams include those with different propagation directions, it is difficult to transmit all multiple light beams through a single optical isolator simultaneously. In such cases, optical isolators may be provided separately from the FI / FO device on the optical path of each light beam. However, this can increase the number of components and, consequently, increase losses.

[0009] One example of the object of the present invention is to provide a fan-in / fan-out device that has isolation functionality and reduces losses. Other objects of the present invention will become apparent from the description herein. [Means for solving the problem]

[0010] One aspect of the present invention for achieving the above objective is a fan-in / fan-out device comprising a multicore fiber having at least a first core and a second core, a first single-core fiber, and a second single-core fiber, wherein the first core and the core of the first single-core fiber are optically connected by a first optical path, and the second core and the core of the second single-core fiber are optically connected by a second optical path, wherein the first optical beam in the first optical path propagates from the first core side to the core side of the first single-core fiber, and the second optical beam in the second optical path propagates from the core side of the second single-core fiber to the second core side, or the first optical beam propagates from the core side of the first single-core fiber to the first core side, and the second optical beam propagates from the core side of the first single-core fiber to the first core side. This fan-in / fan-out device comprises: a multicore fiber side lens provided corresponding to the multicore fiber, which propagates from the side to the core side of the second single core fiber; a first single core fiber side lens provided corresponding to the first single core fiber; a second single core fiber side lens provided corresponding to the second single core fiber; a first isolator unit disposed on the first optical path between the multicore fiber side lens and the first single core fiber side lens, having a first Faraday rotor and a first birefringent element; and a second isolator unit disposed on the second optical path between the multicore fiber side lens and the second single core fiber side lens, having a second Faraday rotor and a second birefringent element.

[0011] Other features of the present invention will be revealed in the specification and drawings described below. [Effects of the Invention]

[0012] According to the above embodiment of the present invention, a fan-in / fan-out device can have an isolation function and reduce losses. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is an explanatory diagram showing the fan-in / fan-out device 10 of this embodiment. [Figure 2] Figure 2 is an explanatory diagram showing the isolator unit group 49 and the magnet unit group 59 in this embodiment. [Figure 3] Figure 3 is a perspective view of the magnet unit 50. [Figure 4] Figure 4A is an explanatory diagram showing the propagation of the light beam in the forward direction in the first isolator unit 41 and the third isolator unit 43 in this embodiment. Figure 4B is an explanatory diagram showing the propagation of the light beam in the reverse direction in the first isolator unit 41 and the third isolator unit 43 in this embodiment. [Figure 5] Figure 5 is an explanatory diagram showing a model of magnetic interference in the magnet unit 50 in this embodiment. [Figure 6] Figure 6 shows examples of considerations for different magnetic pole orientations in the magnet unit 50 according to this embodiment. [Figure 7] Figure 7 is an explanatory diagram showing the prism 60 in this embodiment. [Figure 8] Figure 8 is an explanatory diagram showing the fan-in / fan-out device 10D of the first comparative example. [Figure 9] Figure 9 is an explanatory diagram showing the fan-in / fan-out device 10E of the second comparative example. [Figure 10] Figure 10 is an explanatory diagram showing the first isolator unit 41, the second isolator unit 42, and the magnet unit 50F in the first modified example. [Figure 11] Figure 11 is a perspective view of the magnet unit 50F. [Figure 12]FIG. 12A is an explanatory diagram showing the prism 60G in the second modification. FIG. 12B is an explanatory diagram showing the prism 60H in the third modification.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0015] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The same or equivalent components, members, etc. shown in each drawing are denoted by the same reference numerals, and repeated descriptions will be omitted as appropriate. ​​​​​​​​​​​​​​​​​​​​​​The +Z and -Z directions, +Y and -Y directions, +X and -X directions are all directions with a fixed orientation. However, sometimes both the +Z and -Z directions, which are not directions with a fixed orientation as described above, are simply called the "Z direction." Similarly, both the +Y and -Y directions are sometimes simply called the "Y direction." Also, both the +X and -X directions are sometimes simply called the "X direction."

[0021] Furthermore, the -Z direction is sometimes called the "front stage," the +Z direction the "rear stage," the +Y direction the "upper stage," and the -Y direction the "lower stage." In addition, the Z direction is sometimes called the "front-rear stage direction," and the Y direction the "upper-lower stage direction." These terms such as "front," "rear," "upper," and "lower" indicate the positional relationship (arrangement) on the drawing for the sake of ease of explanation, and the actual positional relationship (arrangement) may differ. In Figure 1, the +X, +Y, and +Z directions are represented by line segments with arrows to facilitate understanding of the direction of the fan-in / fan-out device 10. Note that the intersection of these line segments with arrows does not represent the coordinate origin.

[0022] Unless otherwise specified, the definitions of directions and other terms described above are common to other embodiments of this specification.

[0023] <<Overview>> Next, we will describe the overview of the fan-in / fan-out device 10 of this embodiment, as shown in Figure 1.

[0024] The fan-in / fan-out device 10 is an optical device that optically connects each of the multiple cores of a multicore fiber to each of the multiple single-core fibers. The fan-in / fan-out device 10 of this embodiment is used, for example, in a repeater when connecting landing stations with a submarine cable. In the repeater, by optically connecting the single-core fiber and the multicore fiber using the fan-in / fan-out device 10, it becomes possible to use optical devices that conventionally require connection by single-core fiber, such as optical isolators and wavelength division multiplexing equipment. However, the fan-in / fan-out device 10 may be used in applications other than submarine cable repeaters.

[0025] The fan-in / fan-out device 10 includes a multicore fiber 20, a first single-core fiber 21, a second single-core fiber 22, a multicore fiber side lens 30, a first single-core fiber side lens 31, a second single-core fiber side lens 32, an isolator unit group 49, a magnet unit group 59, and a prism 60. The isolator unit group 49, the magnet unit group 59, and the prism 60 are arranged along axis A.

[0026] The multicore fiber 20 is a multicore fiber having a first core 201 and a second core 202. The central axis at the end of the multicore fiber 20 in the -Z direction coincides with axis A. The first core 201 and the second core 202, and the cladding surrounding each of the first core 201 and the second core 202, are all formed of glass mainly composed of quartz. However, the first core 201 and the second core 202, and the cladding surrounding each of the first core 201 and the second core 202, are not limited to glass mainly composed of quartz, but may be formed of other materials. Furthermore, the end of the multicore fiber 20 in the -Z direction is inserted and held by, for example, a cylindrical ferrule.

[0027] The first single-core fiber 21 is a single-core fiber having a core 210. Both the core 210 and the cladding surrounding the core 210 are formed of glass mainly composed of quartz. However, the core 210 and the cladding surrounding the core 210 are not limited to glass mainly composed of quartz, and may be formed of other materials. Furthermore, the +Z end of the first single-core fiber 21 is inserted and held by, for example, a cylindrical ferrule.

[0028] The second single-core fiber 22 is a single-core fiber having a core 220. Both the core 220 and the cladding surrounding the core 220 are formed of glass mainly composed of quartz. However, the core 220 and the cladding surrounding the core 220 are not limited to glass mainly composed of quartz, and may be formed of other materials. Furthermore, the +Z end of the second single-core fiber 22 is inserted and held by, for example, a cylindrical ferrule.

[0029] The fan-in / fan-out device 10 optically connects the first core 201 of the multicore fiber 20 to the core 210 of the first single-core fiber 21 via a first optical path P1, and optically connects the second core 202 of the multicore fiber 20 to the core 220 of the second single-core fiber 22 via a second optical path P2.

[0030] In this embodiment, the fan-in / fan-out device 10 is described using an example where a multi-core fiber 20 having two cores (first core 201 and second core 202) is optically connected to two single-core fibers (first single-core fiber 21 and second single-core fiber 22) corresponding to the number of cores in the multi-core fiber 20 (here, two). However, the number of cores in the multi-core fiber 20 is not limited to two. The multi-core fiber 20 may have, for example, four cores, five cores, six cores, or seven cores. In that case, the number of single-core fibers optically connected to the multi-core fiber 20 should be the same as the number of cores in the multi-core fiber 20. However, the number of single-core fibers optically connected to the multi-core fiber 20 may be different from the number of cores in the multi-core fiber 20. For example, in a 4-core multi-core fiber 20, only two cores may be optically connected to single-core fibers.

[0031] The multicore fiber-side lens 30 is a collimating lens having a predetermined focal length, and more specifically, an aspherical lens having a rotationally symmetric curved surface. The optical axis of the multicore fiber-side lens 30 is located on the central axis of the multicore fiber 20 (i.e., on axis A). The multicore fiber-side lens 30 collimates (parallels) the light beams emitted and diverging from each of the two cores (first core 201 and second core 202) of the multicore fiber 20.

[0032] The multicore fiber-side lens 30 deflects and emits parallel light beams from each of the two cores (first core 201 and second core 202) (more specifically, it emits the light beams so that they are tilted in a predetermined direction). In other words, the multicore fiber-side lens 30 focuses the parallel light beams at a predetermined focal point. That is, the multicore fiber-side lens 30 is a lens provided in correspondence with the multicore fiber 20. The curved surface of the multicore fiber-side lens 30 may be rotationally symmetric as long as it can emit light beams from each of the two cores (first core 201 and second core 202) in a deflected manner. Furthermore, the multicore fiber-side lens 30 may be a spherical lens or a GRIN lens, or a lens with one flat surface.

[0033] Regarding the multicore fiber-side lens 30, we have described the optical beams emitted from each of the two cores (first core 201 and second core 202), but the same applies to the optical beams incident on each of the two cores (first core 201 and second core 202). The optical beam emitted from the core 210 side of the first single-core fiber 21 is deflected by the multicore fiber-side lens 30 and converges on the first core 201 (more precisely, on the center of the first core 201). Similarly, the optical beam emitted from the core 220 side of the second single-core fiber 22 is deflected by the multicore fiber-side lens 30 and converges on the second core 202 (more precisely, on the center of the second core 202).

[0034] The first single-core fiber-side lens 31 is a collimating lens having a predetermined focal length, and more specifically, an aspherical lens having a rotationally symmetric curved surface. The optical axis of the first single-core fiber-side lens 31 is located on the central axis of the first single-core fiber 21. The first single-core fiber-side lens 31 collimates (parallels) the light beam emitted from the core 210 of the first single-core fiber 21 and diverging. Further explanation is the same as for the multi-core fiber-side lens 30 and will be omitted.

[0035] The second single-core fiber-side lens 32 is a collimating lens having a predetermined focal length, and more specifically, an aspherical lens having a rotationally symmetric curved surface. The optical axis of the second single-core fiber-side lens 32 is located on the central axis of the second single-core fiber 22. The second single-core fiber-side lens 32 collimates (parallels) the light beam emitted from the core 220 of the second single-core fiber 22 and diverging. Further explanations are the same as for the multi-core fiber-side lens 30 and are therefore omitted.

[0036] The isolator unit group 49 has a plurality of isolator units. Specifically, the isolator unit group 49 has a first isolator unit 41, a second isolator unit 42, a third isolator unit 43, and a fourth isolator unit 44. In the fan-in / fan-out device 10 of this embodiment, the first isolator unit 41 and the third isolator unit 43 are arranged on the first optical path P1 between the multicore fiber side lens 30 and the first single-core fiber side lens 31. In addition, in the fan-in / fan-out device 10 of this embodiment, the second isolator unit 42 and the fourth isolator unit 44 are arranged on the second optical path P2 between the multicore fiber side lens 30 and the second single-core fiber side lens 32.

[0037] In this embodiment, the fan-in / fan-out device 10 has isolator units (here, the first isolator unit 41 to the fourth isolator unit 44). That is, the isolator units are provided within the fan-in / fan-out device 10. In other words, the fan-in / fan-out device 10 and the isolator units are integrated into one unit. This reduces losses compared to the case where the isolator units are provided separately from the fan-in / fan-out device 10. In other words, the fan-in / fan-out device 10 of this embodiment has an isolation function and can reduce losses.

[0038] Details of the isolator unit group 49 will be described later.

[0039] The magnet unit group 59 has a plurality of magnet units 50. Each of the plurality of magnet units 50 applies a magnetic field to the Faraday rotor (for example, the first Faraday rotor 410 described later) in the isolator unit of the isolator unit group 49. In the fan-in / fan-out device 10 of this embodiment, the magnet unit group 59 has magnet units 50 that apply a magnetic field to the Faraday rotor in the isolator unit on the -Z direction side (front stage) and magnet units 50 that apply a magnetic field to the Faraday rotor in the isolator unit on the +Z direction side (back stage).

[0040] Details of the magnet unit 50 will be described later.

[0041] The prism 60 is an optical element that changes the distance between the light beam in the first optical path P1 (sometimes called the first light beam) and the light beam in the second optical path P2 (sometimes called the second light beam). In this embodiment, as shown in Figure 1A, the prism 60 is positioned between the multicore fiber-side lens 30 and the isolator unit group 49 (here, the third isolator unit 43 and the fourth isolator unit 44). The prism 60 changes the distance between the first light beam and the second light beam such that the distance on the surface of the multicore fiber-side lens 30 (+Z direction side) is smaller than the distance on the surface of the isolator unit group 49 (-Z direction side).

[0042] The fan-in / fan-out device 10 has a prism 60, which allows for a large separation distance (amount of separation) between the light beam in the first optical path P1 and the light beam in the second optical path P2, and makes it easy to place isolator units for each optical path (first optical path P1 and second optical path P2).

[0043] Details about the Prism 60 will be discussed later.

[0044] <<About Optical Transmission Methods>> As shown in Figure 1, the fan-in / fan-out device 10 of this embodiment supports both the +Z and -Z optical transmission directions for each optical path (first optical path P1 and second optical path P2). Specifically, in the fan-in / fan-out device 10, the first optical path P1 supports the +Z optical transmission direction, and the second optical path P2 supports the -Z optical transmission direction. In other words, in the fan-in / fan-out device 10, the first optical beam in the first optical path P1 propagates from the core 210 side of the first single-core fiber 21 to the first core 201 side of the multi-core fiber 20, and the second optical beam in the second optical path P2 propagates from the second core 202 side of the multi-core fiber 20 to the core 220 side of the second single-core fiber 22. However, in the fan-in / fan-out device 10, the first optical beam in the first optical path P1 may propagate from the first core 201 side of the multicore fiber 20 to the core 210 side of the first single-core fiber 21, while the second optical beam in the second optical path P2 may propagate from the core 220 side of the second single-core fiber 22 to the second core 202 side of the multicore fiber 20. In other words, in this embodiment, a single fan-in / fan-out device 10 can support optical transmission methods with different propagation directions.

[0045] <<Configuration of Isolator Unit Group 49 and Magnet Unit Group 59>>

[0046] Figure 2 is an explanatory diagram showing the isolator unit group 49 and the magnet unit group 59 in this embodiment. Figure 3 is a perspective view of the magnet unit 50.

[0047] In this embodiment, the isolator unit group 49 is arranged on the first optical path P1 between the multicore fiber side lens 30 and the first single-core fiber side lens 31. The second isolator unit 42 and the fourth isolator unit 44 are arranged on the second optical path P2 between the multicore fiber side lens 30 and the second single-core fiber side lens 32.

[0048] As described above, in the fan-in / fan-out device 10 of this embodiment, isolator units are arranged for each optical path. This makes it possible to easily adjust the isolation for each optical path, even when the propagation direction of the first optical beam in the first optical path P1 is the first direction (here, the +Z direction) and the propagation direction of the second optical beam in the second optical path P2 is the second direction (here, the -Z direction) (i.e., even when the propagation directions of multiple optical beams propagating through the fan-in / fan-out device 10 are different for each optical path), as in the fan-in / fan-out device 10 shown in Figure 1 above.

[0049] As described above, in the fan-in / fan-out device 10 of this embodiment, since isolator units are arranged for each optical path, the isolation characteristics can be easily improved even when the propagation direction of the optical beam propagating through the fan-in / fan-out device 10 is different for each optical path.

[0050] Furthermore, in a given optical path, there may be only one isolator unit. That is, in the first optical path P1 between the multicore fiber-side lens 30 and the first single-core fiber-side lens 31, only one of the first isolator unit 41 and the third isolator unit 43 may be provided. Similarly, in the second optical path P2 between the multicore fiber-side lens 30 and the second single-core fiber-side lens 32, only one of the second isolator unit 42 and the fourth isolator unit 44 may be provided.

[0051] The first isolator unit 41 includes a first Faraday rotor 410 and a pair of first birefringent elements 411 positioned before and after the first Faraday rotor 410. The third isolator unit 43 is positioned behind the first isolator unit 41 and includes a third Faraday rotor 430 and a pair of third birefringent elements 431 positioned before and after the third Faraday rotor 430.

[0052] The second isolator unit 42 is positioned below the first isolator unit 41 and includes a second Faraday rotor 420 and a pair of second birefringent elements 421 positioned before and after the second Faraday rotor 420. The fourth isolator unit 44 is positioned behind the second isolator unit 42 and includes a fourth Faraday rotor 440 and a pair of fourth birefringent elements 441 positioned before and after the fourth Faraday rotor 440.

[0053] The magnet unit 50 includes a first magnet 51 that applies a magnetic field to the first Faraday rotor 410 of the first isolator unit 41, and a second magnet 52 that applies a magnetic field to the second Faraday rotor 420. The first magnet 51 and the second magnet 52 are arranged in close proximity with a predetermined distance between them in the vertical direction. However, the first magnet 51 and the second magnet 52 may be arranged adjacent to each other without any distance between them in the vertical direction. In other words, in the magnet unit 50 of this embodiment, magnets are provided in both the upper first isolator unit 41 and the lower second isolator unit 42. By providing magnets for each of the upper and lower isolator units in this way, the strength of the magnetic field can be improved compared to the case where a common (single) magnet is provided for both the upper and lower isolator units. In other words, by providing magnets for each of the upper and lower isolator units, the isolation characteristics can be improved.

[0054] As shown in Figure 3, a cylindrical hole 55 is formed in the center of the first magnet 51, which has a cylindrical outer shape, and the first Faraday rotor 410 is placed in the hole 55. Similarly, as shown in Figure 3, a cylindrical hole 55 is formed in the center of the second magnet 52, which has a cylindrical outer shape, and the second Faraday rotor 420 is placed in the hole 55. Note that the first magnet 51 and the second magnet 52 may be formed in a shape other than a cylinder, for example, a rectangular prism. Also, the hole 55 may be formed in a shape other than a cylinder, for example, a rectangular prism.

[0055] Although not shown in Figure 3, the magnet unit 50 includes a third magnet 53 that applies magnetic force to the third Faraday rotor 430 of the third isolator unit 43, and a fourth magnet 54 that applies magnetic force to the fourth Faraday rotor 440. The third magnet 53 and the fourth magnet 54 are arranged in close proximity with a predetermined gap between them in the vertical direction. However, the third magnet 53 and the fourth magnet 54 may be arranged adjacent to each other without any gap between them in the vertical direction.

[0056] Figure 4A is an explanatory diagram showing the propagation of the light beam in the forward direction in the first isolator unit 41 and the third isolator unit 43 in this embodiment. Figure 4B is an explanatory diagram showing the propagation of the light beam in the reverse direction in the first isolator unit 41 and the third isolator unit 43 in this embodiment.

[0057] As shown in Figure 4A, the light beam emitted from the core 210 of the first single-core fiber 21 and propagating in one direction (forward) is transmitted along the first optical path P1 by passing through the first isolator unit 41 and the third isolator unit 43. On the other hand, as shown in Figure 4B, the light beam propagating in the reverse direction is prevented from entering the core 210 of the first single-core fiber 21 by passing through the third isolator unit 43 and the first isolator unit 41. This prevents the reflected light from entering the transmitting communication device via the first single-core fiber 21 or from undergoing multiple reflections, thereby suppressing the degradation of the optical characteristics of the signal light.

[0058] Furthermore, the description of the propagation of the optical beam in the first isolator unit 41 and the third isolator unit 43 can also be applied similarly to the second isolator unit 42 and the fourth isolator unit 44. In addition, although the forward direction was described above as from the single-core fiber side to the multi-core fiber side and the reverse direction as from the multi-core fiber side to the single-core fiber side, this is not the only way. The forward direction may be from the multi-core fiber side to the single-core fiber side, and the reverse direction may be from the single-core fiber side to the multi-core fiber side.

[0059] <<Regarding the arrangement of the magnet unit 50>> As described above, in the magnet unit group 59 of this embodiment, multiple magnets are arranged in close proximity. Specifically, in the Y direction (upper and lower stages), the first magnet 51 and the second magnet 52 are arranged in close proximity, and the third magnet 53 and the fourth magnet 54 are arranged in close proximity. Also, in the Z direction (front and back stages), the first magnet 51 and the third magnet 53 are arranged in close proximity, and the second magnet 52 and the fourth magnet 54 are arranged in close proximity. In a situation where multiple magnets are arranged in close proximity in this way, magnetic interference between the multiple magnets may occur. Therefore, the arrangement of the magnet unit 50 that can suppress magnetic interference will be considered below.

[0060] Figure 5 is an explanatory diagram showing a model of magnetic interference in the magnet unit 50 in this embodiment.

[0061] Figure 5 shows the direction of the magnetic field component (Hz) in the Z direction when the third magnet 53 and the fourth magnet 54 are placed in close proximity. The third magnet 53 and the fourth magnet 54 are positioned so that their magnetic poles are oriented with the N pole on the -Z side and the S pole on the +Z side. Hereafter, the direction of the magnetic poles of the magnets will be expressed in the order of the -Z direction side and the +Z direction side, and may be expressed as, for example, "NS" or "SN". The magnetic pole directions of the third magnet 53 and the fourth magnet 54 shown in Figure 5 are both "NS". Figure 5 also shows region M1 where the direction of the magnetic field component Hz is in the +Z direction (sometimes called the "first direction") and region M2 where the direction of the magnetic field component Hz is in the -Z direction (sometimes called the "second direction"). Furthermore, for ease of understanding, the direction of the magnetic field component Hz in the +Z direction (first direction) is indicated by a black arrow, and the direction of the magnetic field component Hz in the -Z direction (second direction) is indicated by a white arrow.

[0062] Here, we consider an example in which, after regions M1 and M2 have been formed by the third magnet 53 and fourth magnet 54 described above, the first magnet 51 and the second magnet 52 are further arranged. In Figure 5, the first magnet 51 and the second magnet 52 are arranged so that their magnetic poles are oriented with the -Z side being the south pole and the +Z side being the north pole (the magnetic pole orientation of both the first magnet 51 and the second magnet 52 is "SN").

[0063] With respect to the Z direction (front-to-back stage direction), when considering the hole 55 of the first magnet 51 relative to the hole 55 of the third magnet 53, the hole 55 of the first magnet 51 is located in region M2 where the direction of the magnetic field component Hz is in the -Z direction (second direction). Therefore, the combination of the direction of the magnetic poles of the third magnet 53 and the first magnet 51 in Figure 5 results in a combination where the magnetic field component Hz reinforces each other in the hole 55. Similarly, with respect to the Z direction (front-to-back stage direction), when considering the hole 55 of the second magnet 52 relative to the hole 55 of the fourth magnet 54, the hole 55 of the second magnet 52 is located in region M2 where the direction of the magnetic field component Hz is in the -Z direction (second direction). Therefore, the combination of the direction of the magnetic poles of the fourth magnet 54 and the second magnet 52 in Figure 5 results in a combination where the magnetic field component Hz reinforces each other in the hole 55.

[0064] Therefore, as explained above, with respect to the Z direction (front-to-back stage direction), the combination in which the magnetic pole direction of the third magnet 53 is "NS" and the magnetic pole direction of the first magnet 51 is "SN" results in a combination in which the magnetic field component Hz reinforces each other in the hole 55. Also, with respect to the Z direction (front-to-back stage direction), the combination in which the magnetic pole direction of the fourth magnet 54 is "NS" and the magnetic pole direction of the second magnet 52 is "SN" results in a combination in which the magnetic field component Hz reinforces each other in the hole 55.

[0065] Furthermore, with respect to the Z direction (front-to-back stage direction), for the same reason, the combination in which the magnetic poles of the third magnet 53 are oriented "SN" and the magnetic poles of the first magnet 51 are oriented "NS" results in a combination in which the magnetic field component Hz reinforces each other in the hole 55. Also, with respect to the Z direction (front-to-back stage direction), the combination in which the magnetic poles of the fourth magnet 54 are oriented "SN" and the magnetic poles of the second magnet 52 are oriented "NS" results in a combination in which the magnetic field component Hz reinforces each other in the hole 55.

[0066] In other words, with respect to the Z direction (front-to-back stage direction), the magnetic field component Hz in the hole 55 reinforces each other only when the magnetic poles of the magnets in the front-to-back stage are oriented in opposite directions.

[0067] Figure 6 shows examples of considerations for different magnetic pole orientations in the magnet unit 50 according to this embodiment.

[0068] In the above, we examined the orientation of the magnetic poles of the magnets in the Z direction (front-to-back direction). In Figure 6, we also examine the orientation of the magnetic poles of the magnets in the Y direction (up-down direction) in addition to the Z direction. Here, using the same reasoning as when explaining with Figure 5, in the Y direction (up-down direction), the magnetic field component Hz reinforces in the hole 55 when the orientation of the magnetic poles of the magnets in the upper and lower sections is the same. For example, in the Y direction (up-down direction), the combination in which the magnetic pole orientation of the third magnet 53 is "NS" and the magnetic pole orientation of the fourth magnet 54 is "NS" results in a combination in which the magnetic field component Hz reinforces in the hole 55. Also, in the Y direction (up-down direction), the combination in which the magnetic pole orientation of the first magnet 51 is "SN" and the magnetic pole orientation of the second magnet 52 is "SN" results in a combination in which the magnetic field component Hz reinforces in the hole 55.

[0069] Figure 6 shows examples where the orientations of the magnetic poles of the first magnet 51 to the fourth magnet 54 are different. In Figure 6, the combination of magnetic pole orientations of the magnets in the Z direction (front-to-back direction) is underlined when the magnetic field component Hz reinforces in the hole 55 (when the magnetic pole orientations of the magnets are opposite). Also, the combination of magnetic pole orientations of the magnets in the Y direction (up-to-down direction) is shaded (hatched) when the magnetic field component Hz reinforces in the hole 55 (when the magnetic pole orientations of the magnets are the same). Therefore, the desirable example is when the orientations of the magnetic poles of the first magnet 51 to the fourth magnet 54 are in a direction that reinforces the magnetic field component Hz in the hole 55 in both the Z and Y directions (underlined and shaded). Thus, the cases of Study Example 1 and Study Example 5 are desirable examples.

[0070] In Examples 1 and 5, the direction of the magnetic poles of the first magnet 51 and the second magnet 52 are the same (SN or NS), and the direction of the magnetic poles of the third magnet 53 and the fourth magnet 54 are the same (NS or SN). In addition, the direction of the magnetic poles of the first magnet 51 and the third magnet 53 are opposite, and the direction of the magnetic poles of the second magnet 52 and the fourth magnet 54 are opposite. In this case, magnetic interference can be suppressed in the magnet unit 50.

[0071] <<Details of Prism 60>> Figure 7 is an explanatory diagram showing the prism 60 in this embodiment.

[0072] In this embodiment, the prism 60 is a three-dimensional shape formed integrally. Here, "formed integrally" means "not separated," and can include both cases where multiple members are bonded together and integral molding (such as machining). However, the prism 60 does not have to be a three-dimensional shape formed integrally; for example, it may be separated. The prism 60 is formed as a hexagon with a concave surface on the multicore fiber 20 side (+Z direction side) and a convex surface on the first single core fiber 21 side (-Z direction side) and the second single core fiber 22 side (-Z direction side). The prism 60 has a first plane 61, a second plane 62, a third plane 63, and a fourth plane 64. The first plane 61 faces the first single core fiber 21 side and is the surface through which the first light beam B1 in the first optical path P1 is transmitted. Furthermore, the second plane 62 faces the second single-core fiber 22 and is the plane through which the second optical beam B2 in the second optical path P2 is transmitted. Also, the third plane 63 faces the multi-core fiber 20 and is the plane through which the first optical beam B3 in the first optical path P1 is transmitted. Furthermore, the fourth plane 64 faces the multi-core fiber 20 and is the plane through which the second optical beam B4 in the second optical path P2 is transmitted.

[0073] In the prism 60 of this embodiment, the first plane 61 is inclined such that the angle between the normal of the first plane 61 and the first light beam B1 is within a first predetermined angle. The second plane 62 is inclined such that the angle between the normal of the second plane 62 and the second light beam B2 is within a second predetermined angle. The third plane 63 is inclined such that the angle between the normal of the third plane 63 and the first light beam B3 is within a third predetermined angle. The fourth plane 64 is inclined such that the angle between the normal of the fourth plane 64 and the second light beam B4 is within a fourth predetermined angle.

[0074] In the prism 60 of this embodiment, the first predetermined angle and the second predetermined angle described above are the same at angle β, and the third predetermined angle and the fourth predetermined angle described above are the same at angle α. However, the first predetermined angle and the second predetermined angle may be different angles, and the third predetermined angle and the fourth predetermined angle may be different angles. The first to fourth predetermined angles (here, angles α and β) are determined to be angles that can suppress the increase in PDL (Polarization Dependent Loss) (for example, within 30°).

[0075] <<Comparative Example>> Figure 8 is an explanatory diagram showing the fan-in / fan-out device 10D of the first comparative example.

[0076] The fan-in / fan-out device 10D of the first comparative example shown in Figure 8, like the fan-in / fan-out device 10 of the embodiment described above, optically connects each of the multiple cores of the multicore fiber 20 to each of the multiple single-core fibers (first single-core fiber 21 and second single-core fiber 22). However, unlike the embodiment, in the first comparative example, the fan-in / fan-out device 10D does not have an isolator unit (the fan-in / fan-out device 10D and the isolator unit are not integrated), and an isolator unit 46 is provided separately on the optical path. In this case, for example, optical components such as collimating lenses are required separately for the fan-in / fan-out device 10D and the isolator unit 46, which may increase losses.

[0077] In contrast, the fan-in / fan-out device 10 of this embodiment has an isolator unit (the fan-in / fan-out device 10D and the isolator unit are integrated and provided together), which reduces losses. In other words, the fan-in / fan-out device 10 of this embodiment has an isolation function and can reduce losses.

[0078] Figure 9 is an explanatory diagram showing the fan-in / fan-out device 10E of the second comparative example.

[0079] In the second comparative example, as shown in Figure 9, the fan-in / fan-out device 10E differs from the fan-in / fan-out device 10 of this embodiment in that it does not have an isolator unit for each optical path, and multiple optical beams are transmitted collectively through a single isolator unit 45. Therefore, in the second comparative example, when the propagation directions of multiple optical beams propagating through the fan-in / fan-out device 10E differ from one another for each optical path, it is difficult to adjust the isolation for each optical path with a single isolator unit 45.

[0080] In contrast, in the fan-in / fan-out device 10 of this embodiment, since isolator units are arranged for each optical path, the isolation characteristics can be easily improved even when the propagation direction of the light beam propagating through the fan-in / fan-out device 10 differs from that of each optical path.

[0081] <<Variation>> Figure 10 is an explanatory diagram showing the first isolator unit 41, the second isolator unit 42, and the magnet unit 50F in the first modified example. Figure 11 is a perspective view of the magnet unit 50F.

[0082] In the fan-in / fan-out device 10 of the embodiment described above, the magnet unit 50 had a first magnet 51 that applied magnetism to the first Faraday rotor 410 of the first isolator unit 41, and a second magnet 52 that applied magnetism to the second Faraday rotor 420. However, the configuration of the magnets in the magnet unit is not limited to this. As in the magnet unit 50F in the first modified example, a configuration in which the upper and lower first isolator units 41 and the second isolator unit 42 are arranged on a single magnet is also possible.

[0083] As shown in Figures 10 and 11, a cylindrical hole 55 is formed in the center of the cylindrical magnet unit 50F, and at least the first Faraday rotor 410 and the second Faraday rotor 420 are arranged in the hole 55F.

[0084] Even with the fan-in / fan-out device of the first modified example, the isolation characteristics in the fan-in / fan-out device can be easily improved by arranging isolator units for each optical path.

[0085] Figure 12A is an explanatory diagram showing prism 60G in the second modified example. Figure 12B is an explanatory diagram showing prism 60H in the third modified example.

[0086] In the prism 60 of the embodiment described above, the surface on the multicore fiber 20 side (+Z direction side) was concave, and the surfaces on the first single core fiber 21 (-Z direction side) and the second single core fiber 22 side (-Z direction side) were convex, forming a hexagon. However, the shape of the prism is not limited to this.

[0087] As shown in the second modified example in Figure 12A, the prism 60G may be formed in a hexagon shape with the multicore fiber 20 side (+Z direction side) being convex, and the first single core fiber 21 (-Z direction side) and the second single core fiber 22 side (-Z direction side) being convex. Alternatively, as shown in the third modified example in Figure 12B, the prism 60H may be formed in a pentagon shape with the multicore fiber 20 side (+Z direction side) being flat, and the first single core fiber 21 (-Z direction side) and the second single core fiber 22 side (-Z direction side) being convex.

[0088] ==Summary== According to this specification, fan-in / fan-out devices in the following embodiments are provided.

[0089] (Aspect 1) Embodiment 1 is a fan-in / fan-out device comprising a multicore fiber having at least a first core and a second core, a first single-core fiber, and a second single-core fiber, wherein the first core and the core of the first single-core fiber are optically connected by a first optical path, and the second core and the core of the second single-core fiber are optically connected by a second optical path, wherein the first optical beam in the first optical path propagates from the first core side to the core side of the first single-core fiber, and the second optical beam in the second optical path propagates from the core side of the second single-core fiber to the second core side, or the first optical beam propagates from the core side of the first single-core fiber to the first core side, and the second optical beam propagates from the second core side to the second single-core fiber This fan-in / fan-out device comprises: a multicore fiber side lens that propagates to the core side of a multicore fiber and is provided corresponding to the multicore fiber; a first single-core fiber side lens provided corresponding to the first single-core fiber; a second single-core fiber side lens provided corresponding to the second single-core fiber; a first isolator unit disposed on the first optical path between the multicore fiber side lens and the first single-core fiber side lens and having a first Faraday rotor and a first birefringent element; and a second isolator unit disposed on the second optical path between the multicore fiber side lens and the second single-core fiber side lens and having a second Faraday rotor and a second birefringent element.

[0090] According to the above-described embodiment, the isolation characteristics of the fan-in / fan-out device can be easily improved.

[0091] (Aspect 2) Embodiment 2 includes a magnetic unit that applies magnetism to the first Faraday rotor and the second Faraday rotor.

[0092] According to the above-described embodiment, the isolation characteristics of the fan-in / fan-out device can be easily improved.

[0093] (Aspect 3) In embodiment 3, the magnet unit includes a first magnet for applying magnetism to the first Faraday rotor and a second magnet for applying magnetism to the second Faraday rotor.

[0094] According to the above-described embodiment, the isolation characteristics of the fan-in / fan-out device can be easily improved.

[0095] (Aspect 4) In embodiment 4, the orientation of the magnetic poles of the first magnet and the orientation of the magnetic poles of the second magnet are the same.

[0096] According to the above-described embodiment, magnetic interference can be suppressed.

[0097] (Aspect 5) Embodiment 5 includes a third isolator unit arranged alongside the first isolator unit in the first optical path and having a third Faraday rotor and a third birefringent element, and a fourth isolator unit arranged alongside the second isolator unit in the second optical path and having a fourth Faraday rotor and a fourth birefringent element.

[0098] According to the above-described embodiment, the isolation characteristics of the fan-in / fan-out device can be easily improved.

[0099] (Aspect 6) In embodiment 6, the device includes a first magnet for applying magnetism to the first Faraday rotor, a second magnet for applying magnetism to the second Faraday rotor, a third magnet for applying magnetism to the third Faraday rotor, and a fourth magnet for applying magnetism to the fourth Faraday rotor, wherein the direction of the magnetic poles of the first magnet and the second magnet are the same, the direction of the magnetic poles of the third magnet and the fourth magnet are the same, and the direction of the magnetic poles of the first magnet and the third magnet are opposite.

[0100] According to the above-described embodiment, magnetic interference can be suppressed.

[0101] (Aspect 7) Embodiment 7 further comprises a prism positioned between the multicore fiber-side lens and the first isolator unit and the second isolator unit, wherein the prism changes the separation distance between the first light beam in the first optical path and the second light beam in the second optical path on the side of the multicore fiber-side lens and on the side of the first isolator unit and the second isolator unit.

[0102] According to the above-described embodiment, isolator units can be easily arranged for each optical path.

[0103] (Pattern 8) In embodiment 8, the prism is a three-dimensional shape formed integrally and has a first plane facing the multicore fiber side through which the first light beam passes, a second plane facing the multicore fiber side through which the second light beam passes, a third plane facing the first single-core fiber side through which the first light beam passes, and a fourth plane facing the second single-core fiber side through which the second light beam passes, wherein the first plane is inclined such that the angle between the normal of the first plane and the first light beam is within a first predetermined angle, the second plane is inclined such that the angle between the normal of the second plane and the second light beam is within a second predetermined angle, the third plane is inclined such that the angle between the normal of the third plane and the first light beam is within a third predetermined angle, and the fourth plane is inclined such that the angle between the normal of the fourth plane and the second light beam is within a fourth predetermined angle.

[0104] According to the above-described embodiment, the increase in PDL can be suppressed. [Explanation of symbols]

[0105] 10, 10D, 10E Fan-in / Fan-out Device 20 Multicore Fibers 21. First Single Core Fiber 22 Second Single Core Fiber 23 Single Core Fibers 30 Multicore fiber side lens 31. First single-core fiber side lens 32. Second single-core fiber side lens 33 Single-core fiber side lens 41. First Isolator Unit 42. Second Isolator Unit 43 Third Isolator Unit 44. Unit 4 Isolator 45,46 Isolator Unit 49 Isolator Unit Group 50,50F Magnet Unit 51 First Magnet 52 Second Magnet 53 Third Magnet 54. Fourth Magnet 55,55F hole 59 Magnet Unit Group 60, 60G, 60H prism 61,61G,61H 1st plane 62,62G,62H 2nd plane 63,63G,63H 3rd plane 64,64G,64H 4th plane 201 First Core 202 Second Core 210 cores 220 cores 410 First Faraday Rotor 411 First birefringent element 420 Second Faraday Rotor 421 Second birefringent element 430 Third Faraday Rotor 431 Third birefringent element 440 Fourth Faraday Rotor 441 Fourth Birefringent Element P1 1st optical path P2 2nd optical path M1 Region where the direction of the magnetic field is the first direction M2 is the region where the direction of the magnetic field is the second direction. A optical axis B1 First light beam B2 Second Light Beam S separation amount Z total length

Claims

1. A multicore fiber having at least a first core and a second core, First single core fiber, A second single core fiber is provided, A fan-in / fan-out device that optically connects the first core and the core of the first single-core fiber via a first optical path, and optically connects the second core and the core of the second single-core fiber via a second optical path, The first optical beam in the first optical path propagates from the first core side to the core side of the first single-core fiber, and the second optical beam in the second optical path propagates from the core side of the second single-core fiber to the second core side, or The first light beam propagates from the core side of the first single-core fiber to the first core side, and the second light beam propagates from the second core side to the core side of the second single-core fiber. A multicore fiber side lens provided in correspondence with the multicore fiber, A first single-core fiber side lens provided corresponding to the first single-core fiber, A second single-core fiber side lens provided in correspondence with the second single-core fiber, A first isolator unit is disposed on the first optical path between the multicore fiber-side lens and the first single-core fiber-side lens, and has a first Faraday rotor and a first birefringent element. A second isolator unit is disposed on the second optical path between the multicore fiber-side lens and the second single-core fiber-side lens, and has a second Faraday rotor and a second birefringent element. A fan-in / fan-out device equipped with these features.

2. The system includes a magnetic unit for applying magnetic fields to the first Faraday rotor and the second Faraday rotor. The fan-in / fan-out device according to claim 1.

3. The aforementioned magnet unit is A first magnet for applying magnetism to the first Faraday rotor, A second magnet for applying magnetic field to the second Faraday rotor, Having, The fan-in / fan-out device according to claim 2.

4. The orientation of the magnetic poles of the first magnet and the orientation of the magnetic poles of the second magnet are the same. The fan-in / fan-out device according to claim 3.

5. A third isolator unit is arranged in the first optical path alongside the first isolator unit and has a third Faraday rotor and a third birefringent element, In the second optical path, a fourth isolator unit is arranged alongside the second isolator unit and has a fourth Faraday rotor and a fourth birefringent element, Equipped with, The fan-in / fan-out device according to claim 1.

6. A first magnet for applying magnetism to the first Faraday rotor, A second magnet for applying magnetic field to the second Faraday rotor, A third magnet for applying magnetic field to the third Faraday rotor, A fourth magnet for applying magnetic field to the fourth Faraday rotor, Equipped with, The orientation of the magnetic poles of the first magnet and the orientation of the magnetic poles of the second magnet are the same. The direction of the magnetic poles of the third magnet and the direction of the magnetic poles of the fourth magnet are the same. The direction of the magnetic poles of the first magnet and the direction of the magnetic poles of the third magnet are opposite. The fan-in / fan-out device according to claim 5.

7. The multicore fiber side lens further comprises a prism positioned between the first isolator unit and the second isolator unit, The prism mentioned above is The separation distance between the first light beam in the first optical path and the second light beam in the second optical path is varied on the side of the multicore fiber side lens and on the side of the first isolator unit and the second isolator unit. The fan-in / fan-out device according to claim 1.

8. The prism is a three-dimensional shape formed integrally, A first plane facing the multicore fiber side, through which the first light beam passes, A second plane facing the multicore fiber side, through which the second light beam passes, A third plane facing the first single-core fiber side, through which the first light beam passes, A fourth plane facing the second single-core fiber side, through which the second light beam passes, It has, The first plane is inclined such that the angle between the normal to the first plane and the first light beam is within a first predetermined angle. The second plane is inclined such that the angle between the normal to the second plane and the second light beam is within a second predetermined angle. The third plane is inclined such that the angle between the normal to the third plane and the first light beam is within a third predetermined angle. The fourth plane is inclined such that the angle between the normal to the fourth plane and the second light beam is within a fourth predetermined angle. The fan-in / fan-out device according to claim 7.

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