Optical fiber connector, optical communication system, optical device, and method for manufacturing optical fiber connector

Abstract

Provided is an optical fiber connector or a method for manufacturing the same, the optical fiber connector having at least two multicore optical fibers provided with marks and improved optical characteristics. At least provided are: a first multicore optical fiber (111) including a plurality of cores (111a1-111an) arranged inside a cladding and a first mark (111c); and a second multicore optical fiber (112) including a plurality of cores (112a1-112an) arranged inside a cladding and a second mark (112c), and one end face (112L) is connected to one end face (111R) of the first multicore optical fiber, the plurality of cores of the second multicore optical fiber are respectively connected to any one of the plurality of cores of the first multicore optical fiber, or the plurality of cores of the first multicore optical fiber are respectively connected to any one of the plurality of cores of the second multicore optical fiber.

Description

Technical Field

[0001] This invention relates to an optical fiber connector having multiple multi-core optical fibers and a method for manufacturing the same. Background Technology

[0002] Multi-core optical fibers with multiple cores are widely used in the field of optical communication. Patent Document 1 is an example of a document that discloses multi-core optical fibers. Multi-core optical fiber connectors that connect multiple multi-core optical fibers are also widely used. Existing technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-152866 Summary of the Invention (a) Technical problems to be solved

[0004] The purpose of this invention is to solve the following first or second technical problem.

[0005] (First technical issue) Multi-core optical fibers have multiple cores and a cladding. The cladding is a cylindrical component, and each core is a cylindrical region located inside the cladding, with a higher refractive index than the cladding, extending in the same direction as the cladding. Sometimes, markings are formed on the multi-core optical fibers to identify each core individually. These markings are regions located inside the cladding, with a different refractive index than the cladding, extending in the same direction as the cladding. The shape of the markings is arbitrary, such as cylindrical, triangular prism, etc. When manufacturing an optical fiber connector by connecting multiple multi-core optical fibers with markings, the connection operation is performed by connecting the markings of one multi-core optical fiber to the markings of another multi-core optical fiber. However, there is still room for improvement in the optical properties of optical fiber connectors manufactured in this way.

[0006] One aspect of the present invention addresses the aforementioned technical problem by providing an optical fiber connector or a method for manufacturing the optical fiber connector, the optical fiber connector comprising at least two marked multi-core optical fibers and improving optical properties.

[0007] (Second technical issue) Sometimes, markings for identifying the fiber cores are formed on multi-core optical fibers. In existing optical fiber connectors that connect such multi-core optical fibers, the end face of one of the adjacent multi-core optical fibers is designated as the first end face, and the end face of the other is designated as the second end face, and the multi-core optical fibers are connected to each other in a manner that satisfies the following conditions.

[0008] (1) Multiple fiber cores in the first end face overlap with multiple fiber cores in the second end face.

[0009] (2) The mark in the first end face coincides with the mark in the second end face.

[0010] Therefore, when fiber cores are identified at both ends of the fiber connector based on the distance from the mark, the optically coupled cores are assigned the same identifier. Thus, for example, if each core is used for either input or output of an optical signal, and cores with the same identifier are used for the same purpose, then the two ends of the optically coupled cores are used for input, or the two ends of the optically coupled cores are used for output. Based on this, existing fiber connectors present a problem that is difficult to handle.

[0011] One aspect of the present invention addresses the aforementioned technical problems, with the aim of providing an optical fiber connector that is easier to handle than previously possible. (II) Technical Solution

[0012] (Solution to the first technical problem) According to one aspect of the first aspect of the present invention, an optical fiber connector is characterized by comprising at least: a first multi-core optical fiber having a plurality of cores and at least one first mark disposed inside a cladding; and a second multi-core optical fiber having a plurality of cores and at least one second mark disposed inside a cladding, and having one end face connected to one end face of the first multi-core optical fiber, wherein each core of the second multi-core optical fiber is connected to any core of the first multi-core optical fiber, or each core of the first multi-core optical fiber is connected to any core of the second multi-core optical fiber, and at least one of the second marks of the second multi-core optical fiber is connected to a portion of the first multi-core optical fiber other than the first mark, or at least one of the first marks of the first multi-core optical fiber is connected to a portion of the second multi-core optical fiber other than the second mark.

[0013] A method for manufacturing an optical fiber connector according to a first aspect of the present invention is characterized in that the optical fiber connector comprises: a first multi-core optical fiber having a plurality of cores and at least one first mark disposed inside a cladding, and a second multi-core optical fiber having a plurality of cores and at least one second mark disposed inside a cladding; the method comprising the steps of: connecting each core of the second multi-core optical fiber to any core of the first multi-core optical fiber, or connecting each core of the first multi-core optical fiber to any core of the second multi-core optical fiber; and connecting one end face of the second multi-core optical fiber to one end face of the first multi-core optical fiber in such a manner that at least any one of the second marks of the second multi-core optical fiber is connected to a portion of the first multi-core optical fiber other than the first mark, or connecting at least any one of the first marks of the first multi-core optical fiber to a portion of the second multi-core optical fiber other than the second mark.

[0014] (Solution to the second technical problem) According to a second aspect of the present invention, an optical fiber connector is characterized in that it is connected to a plurality of multi-core optical fibers with identical core configurations. Each multi-core optical fiber has an end face containing a cladding, a plurality of cores arranged linearly symmetrically inside the cladding, and a mark, the center of which is located outside the axis of symmetry of the plurality of cores. When one end face of an adjacent multi-core optical fiber is designated as a first end face and the other end face as a second end face, the number of connection points satisfying the following conditions is odd: (1) the plurality of cores on the first end face coincide with the plurality of cores on the second end face; and (2) the mark on the first end face coincides with a position on the second end face that is linearly symmetrical with respect to the axis of symmetry to the mark on the second end face.

[0015] A method for manufacturing an optical fiber connector according to a second aspect of the present invention is characterized in that the optical fiber connector is connected to a plurality of multi-core optical fibers with identical core configurations. Each multi-core optical fiber has an end face that includes a cladding, a plurality of cores arranged in a line symmetrical manner inside the cladding, and a mark disposed at a position other than the axis of symmetry of the plurality of cores. When the end face of one of the multi-core optical fibers adjacent to each other is set as a first end face and the end face of the other multi-core optical fiber is set as a second end face, the plurality of multi-core optical fibers are connected in such a way that the number of connection points satisfying the following conditions is an odd number: (1) the plurality of cores of the first end face coincide with the plurality of cores of the second end face; and (2) the mark of the first end face coincides with a position in the second end face that is line symmetrical with respect to the axis of symmetry with respect to the mark of the second end face. (III) Beneficial Effects

[0016] One aspect of the present invention has the following first or second effects.

[0017] (First effect) According to one aspect of the invention, an optical fiber connector is provided that has at least two marked multi-core optical fibers and improves optical properties.

[0018] (Second effect) According to one aspect of the present invention, an optical fiber connector that is easier to handle than before can be realized. Furthermore, according to another aspect of the present invention, an optical communication system or optical device incorporating such an optical fiber connector can be realized. Attached Figure Description

[0019] Figure 1These are side views and cross-sectional views showing the structure of an optical fiber connector according to a first embodiment of the first aspect of the present invention. Figure 2 yes Figure 1 The cross-sectional view of the fiber optic connector shown illustrates the variation in the connection pattern. Figure 3 It means Figure 1 Side view and cross-sectional view of the first modified example of the optical fiber connector shown. Figure 4 It means Figure 1 Side view and cross-sectional view of a second modified example of the optical fiber connector shown. Figure 5 These are side views and cross-sectional views showing the structure of an optical fiber connector according to a second embodiment of the first aspect of the present invention. Figure 6 yes Figure 5 The cross-sectional view of the fiber optic connector shown illustrates the variation in the connection pattern. Figure 7 yes Figure 5 The cross-sectional view of the fiber optic connector shown illustrates the variation in the marking configuration. Figure 8 It means Figure 5 Side view and cross-sectional view of a modified example of the optical fiber connector shown. Figure 9 The diagram shows a multi-core optical fiber included in an optical fiber connector according to a second aspect of the present invention. (a) is a side view of the multi-core optical fiber, (b) is a front view of one end face of the multi-core optical fiber, and (c) is a front view of the other end face of the multi-core optical fiber. Figure 10 It means Figure 9 The diagrams showing the changes in the cross-sectional structure of the multi-core optical fiber are shown in (a) to (f), which are front views of one end face of the multi-core optical fiber. Figure 11 The diagram shows two multi-core optical fibers that are typically connected. (a) is a side view of the two multi-core optical fibers, (b) is a front view of the end face of one multi-core optical fiber, and (c) is a front view of the end face of the other multi-core optical fiber. Figure 12 The diagram shows two multi-core optical fibers connected in a flipped configuration. (a) is a side view of the two multi-core optical fibers, (b) is a front view of the end face of one multi-core optical fiber, and (c) is a front view of the end face of the other multi-core optical fiber. Figure 13 The diagram shows two multi-core optical fibers connected in a flipped configuration. (a) is a side view of the two multi-core optical fibers, (b) is a front view of the end face of one multi-core optical fiber, and (c) is a front view of the end face of the other multi-core optical fiber. Figure 14The diagram shows an optical fiber connector according to one aspect of the second aspect of the present invention, (a) is a side view of the optical fiber connector, (b) is a front view of one end face of the optical fiber connector, and (c) is a front view of the other end face of the optical fiber connector. Figure 15 This is an explanation Figure 14 The diagrams show the effect of the fiber optic connector. (a) is a front view of one end face of the fiber optic connector, and (b) is a front view of the other end face of the fiber optic connector. Figure 16 It means Figure 14 The figure shows a modified example of the fiber optic connector, (a) is a side view of the fiber optic connector, (b) is a front view of one end face of the fiber optic connector, and (c) is a front view of the other end face of the fiber optic connector. Figure 17 It means to include Figure 14 The diagram shows an optical communication system with an optical fiber connector and two transceivers. (a) is a side view of the communication system, (b) is a front view of one end face of the optical fiber connector, (c) is a front view of the other end face of the optical fiber connector, (d) is a front view of the optical input / output element of one transceiver, and (e) is a front view of the optical input / output element of the other transceiver. Figure 18 It means to include Figure 14 The diagram shows a block diagram of an optical communication system with an optical fiber connector and two fan-in / fan-out devices. Figure 19 This is a cross-sectional view showing a modified example of the optical fiber connector according to the first embodiment of the first aspect of the present invention. Figure 20 This is a cross-sectional view showing a modified example of the optical fiber connector according to the first embodiment of the first aspect of the present invention. Figure 21 This is a cross-sectional view showing a modified example of the optical fiber connector according to the first embodiment of the first aspect of the present invention. Detailed Implementation

[0020] (First aspect) (First embodiment of the first aspect) (Structure of fiber optic connector) Reference Figure 1 The structure of the optical fiber connector 101 according to the first embodiment of the first aspect of the present invention will be described. Figure 1 These are side views and cross-sectional views showing the structure of the optical fiber connector 101.

[0021] like Figure 1As shown, the optical fiber connector 101 includes a first multi-core optical fiber 111 and a second multi-core optical fiber 112. One end face 111R of the first multi-core optical fiber 111 is connected (in this embodiment, fused) to one end face 112L of the second multi-core optical fiber 112.

[0022] The first multi-core optical fiber 111 comprises n (n is a natural number greater than or equal to 2) cores 111a1 to 111an and a cladding 111b. The cladding 111b is a cylindrical component. Furthermore, the cross-sectional shape of the cladding 111b is not particularly limited; for example, it can be a polygonal shape such as a quadrilateral or hexagon, or a drum shape. The cladding 111b is, for example, made of quartz glass. Each core 111ai (i is a natural number greater than or equal to 1 and less than n) is a cylindrical region disposed within the cladding 111b and having a higher refractive index than the cladding 111b, extending in the same direction as the cladding 111b. Each core 111ai is, for example, made of quartz glass to which a rising dopant such as germanium is added. The cores 111a1 to 111an are arranged such that their cross-sectional centers are evenly spaced on a circle of radius R starting from the center of the cladding 111b.

[0023] The first multi-core optical fiber 111 also includes a marker 111c. The marker 111c is a region located inside the cladding 111b and extending in the same direction as the cladding 111b, with a refractive index different from that of the cladding 111b. The shape of the marker 111c is arbitrary, such as cylindrical, triangular prism, etc. The marker 111c may be made of, for example, quartz glass with added de-dopers such as fluorine or boron. In this case, the refractive index of the marker 111c is lower than that of the cladding 111b. Alternatively, the marker 111c may be made of quartz glass with added up-dopers such as germanium, aluminum, phosphorus, or chlorine. In this case, the refractive index of the marker 111c is higher than that of the cladding 111b. The marker 111c can be formed using, for example, a hole-opening method or a stacking method.

[0024] Regarding the configuration of marker 111c in the first multi-core optical fiber 111, the distance from marker 111c to fiber core 111ai is set as di, and determined in such a way that d1, d2, ..., dn are all different. This is to make it easy to identify fiber cores 111a1 to 111an based on the distance from marker 111c. This allows for more reliable identification of each fiber core, for example, enabling the measurement of the characteristics of a specific fiber core. Furthermore, the ordinal numbers of fiber cores 111a1 to 111an in the first multi-core optical fiber 111 can be determined based on their positional relationship with marker 111c as follows: That is, among fiber cores 111a1 to 111an, the fiber core closest to marker 111c is designated as the first fiber core 111a1. Additionally, among fiber cores 111a1 to 111an, the fiber core that is second only to the first fiber core 111a1 in proximity to marker 111c is designated as the second fiber core 111a2. The ordinal numbers of the remaining fiber cores 111a3 to 111an are determined according to their arrangement order on the aforementioned circle of radius R. For example, the fiber core that is not the first fiber core 111a1 among the two fiber cores adjacent to the second fiber core 111a2 is designated as the third fiber core 111a3. Furthermore, the fiber core that is not the second fiber core 111a2 among the two fiber cores adjacent to the third fiber core 111a3 is designated as the fourth fiber core 111a4.

[0025] The second multi-core optical fiber 112 comprises n cores 112a1 to 112an and a cladding 112b. The cladding 112b is a cylindrical component. The cladding 112b is, for example, made of quartz glass. Each core 112ai is a cylindrical region disposed within the cladding 112b and having a higher refractive index than the cladding 112b, extending in the same direction as the cladding 112b. Furthermore, the cross-sectional shape of the cladding 112b is not particularly limited; for example, it can be a polygonal shape such as a quadrilateral or hexagon, or it can be drum-shaped. Each core 112ai is, for example, made of quartz glass with added germanium or other rising dopants. The number of cores 112a1 to 112an is the same as the number of cores 111a1 to 111an in the first multi-core optical fiber 111. Additionally, the diameters of the cores 112a1 to 112an are the same as the diameters of the cores 111a1 to 111an in the first multi-core optical fiber 111. Furthermore, the arrangement of fiber cores 112a1 to 112an is determined in the same manner as the arrangement of fiber cores 111a1 to 111an in the first multi-core fiber 111, such that the cross-sections of fiber cores 112a1 to 112an are arranged at equal intervals on a circle with a radius of R starting from the center of cladding 112b.

[0026] The second multi-core optical fiber 112 also includes a marker 112c. The marker 112c is a region located inside the cladding 112b and extending in the same direction as the cladding 112b, with a refractive index different from that of the cladding 112b. The shape of the marker 112c is arbitrary, such as cylindrical, triangular prism, etc. The marker 112c is, for example, made of quartz glass with added descending dopants such as fluorine. In this case, the refractive index of the marker 112c is lower than that of the cladding 112b. Alternatively, the marker 112c can be made of quartz glass with added ascending dopants such as germanium, aluminum, phosphorus, chlorine, etc. In this case, the refractive index of the marker 112c is higher than that of the cladding 112b. The marker 112c can be formed using methods such as aperture drilling or stacking.

[0027] The configuration of marker 112c in the second multi-core optical fiber 112 is determined in the same manner as the configuration of marker 111c in the first multi-core optical fiber 111. Furthermore, the ordinal numbers of the cores 112a1 to 112an in the second multi-core optical fiber 112 are determined in the same manner as the ordinal numbers of the cores 111a1 to 111an in the first multi-core optical fiber 111.

[0028] also, Figure 1 The AA' section of the first multi-core optical fiber 111 shown is from... Figure 1 Observing from the right side of the middle, relatively speaking, Figure 1 The BB' section of the second multi-core optical fiber 112 shown is from... Figure 1 Observe from the left side. Therefore, in the connection between one end face 111R and one end face 112L, the AA' section of the first multi-core optical fiber 111... Figure 1 The right end of the middle and the BB' section of the second multi-core fiber 112 Figure 1 The left ends of the first multi-core optical fiber 111 are interconnected, and the AA' section of the first multi-core optical fiber 111 is... Figure 1 The left end of the middle and the BB' section of the second multi-core fiber 112 Figure 1 The right ends of the two are connected to each other.

[0029] In the optical fiber connector 101 of this embodiment, the first multi-core optical fiber 111 and the second multi-core optical fiber 112 are connected in a manner that satisfies the following conditions.

[0030] Condition 1: Each core 112ai of the second multi-core optical fiber 112 is connected to any core 111a1 to 111an of the first multi-core optical fiber 111.

[0031] Condition 2: Mark 112c of the second multi-core optical fiber 112 is connected to the portion of the first multi-core optical fiber 111 other than mark 111c.

[0032] Furthermore, the optical fiber connector 101 of this embodiment satisfies the following conditions.

[0033] Condition 3A: The first fiber core 112a1 in the second multi-core fiber 112 that is closest to mark 112c is connected to the fiber core other than the first fiber core 111a1 that is closest to mark 111c among the fibers 111a1 to 111an of the first multi-core fiber 111 (specifically the third fiber core 111a3).

[0034] (Effect of the fiber optic connector) It is known that in multi-core optical fibers, the waveguide properties of the core closest to the marker are prone to deterioration. There are several reasons for this, including: The gaps between the marker material and the cladding material in the fiber's matrix and cladding may be compressed and damaged. Additionally, during cooling after the fiber's matrix is ​​drawn, the glass surrounding the marker may deform and be stressed due to the difference in linear expansion coefficients between the marker and the cladding. In such cases, the core closest to the marker experiences stress and deformation, potentially leading to deterioration in its waveguide properties. Examples of properties that may deteriorate in the core closest to the marker include polarization mode dispersion.

[0035] In existing fiber optic connectors, the core closest to the mark in the second multi-core fiber is connected to the core closest to the mark in the first multi-core fiber. Therefore, regarding the signal light propagating along the core closest to the mark in the first multi-core fiber, degradation caused by the mark easily occurs in both the first and second multi-core fibers. Consequently, errors can occur in communications that use signal light propagating along the core closest to the mark in the first multi-core fiber.

[0036] In contrast, in the fiber optic connector 101 of this embodiment, the first core 112a1 closest to mark 112c in the second multi-core fiber 112 is connected to a core other than the first core 111a1 closest to mark 111c among the cores 111a1 to 111an of the first multi-core fiber 111 (specifically, the third core 111a3). Therefore, regarding the signal light propagated along the core 111a1 closest to mark 111c in the first multi-core fiber 111, the degradation caused by mark 112c can be suppressed in the second multi-core fiber 112. Thus, the possibility of errors occurring in communications using signal light propagated along the first core 111a1 closest to mark 111c in the first multi-core fiber 111 can be reduced.

[0037] In addition, Figure 1In the connection pattern shown, the first fiber core 111a1, which is closest to mark 111c in the first multi-core fiber 111, is connected to the third fiber core 112a3, which is furthest from mark 112c in the second multi-core fiber 112. Furthermore, the second fiber core 111a2, which is closest to mark 111c after the first fiber core 111a1 in the first multi-core fiber 111, is connected to the fourth fiber core 112a4, which is furthest from mark 112c after the third fiber core 112a3 in the second multi-core fiber 112. This allows for more uniform degradation of the signal light propagated in each fiber core 111a1 of the first multi-core fiber 111. This is because the first fiber core 111a1, whose optical properties are most prone to degradation in the first multi-core fiber 111, is connected to the third fiber core 112a3, whose optical properties are least prone to degradation in the second multi-core fiber 112. Furthermore, the reason is that in the first multi-core fiber 111, the second core 111a2, whose optical properties are second most easily degraded, is connected to the fourth core 112a4, whose optical properties are second least easily degraded, in the second multi-core fiber 112. As a result, the possibility of errors occurring in communications that use signal light transmitted in each core 111a1 of the first multi-core fiber 111 can be further reduced.

[0038] (Changes in the connecting pattern) The connection patterns that meet conditions 1, 2, and 3A above are not limited to Figure 1 The connection pattern shown. Figure 2 It shows Figure 1 Other connection patterns besides the shown connection pattern that satisfy conditions 1, 2 and 3A above.

[0039] Figure 2 (a) represents the connection pattern of the first fiber core 111a1, which is closest to mark 111c in the first multi-core fiber 111, to the second fiber core 112a2 in the second multi-core fiber 112. The first fiber core 112a1, which is closest to mark 112c in the second multi-core fiber 112, is connected to the fourth fiber core 111a4 in the first multi-core fiber 111.

[0040] Figure 2 (b) represents the connection pattern of the first core 111a1, which is closest to mark 111c in the first multi-core fiber 111, to the fourth core 112a4 in the second multi-core fiber 112. The first core 112a1, which is closest to mark 112c in the second multi-core fiber 112, is connected to the second core 111a2 in the first multi-core fiber 111.

[0041] Figure 2(c) represents the connection pattern of the first fiber core 111a1, which is closest to mark 111c in the first multi-core optical fiber 111, to the second fiber core 112a2 in the second multi-core optical fiber 112. The first fiber core 112a1, which is closest to mark 112c in the second multi-core optical fiber 112, is connected to the second fiber core 111a2 in the first multi-core optical fiber 111.

[0042] Figure 2 (d) represents the connection pattern of the first fiber core 111a1, which is closest to mark 111c in the first multi-core fiber 111, to the fourth fiber core 112a4 in the second multi-core fiber 112. The first fiber core 112a1, which is closest to mark 112c in the second multi-core fiber 112, is connected to the fourth fiber core 111a4 in the first multi-core fiber 111.

[0043] Figure 2 (e) represents the connection pattern of the first fiber core 111a1, which is closest to mark 111c in the first multi-core fiber 111, to the third fiber core 112a3 in the second multi-core fiber 112. The first fiber core 112a1, which is closest to mark 112c in the second multi-core fiber 112, is connected to the fourth fiber core 111a4 in the first multi-core fiber 111.

[0044] exist Figure 2 In any of the connection patterns shown in (a) to (e), the first fiber core 112a1 closest to mark 112c in the second multi-core fiber 112 is connected to a fiber core other than the first fiber core 111a1 closest to mark 111c among the fibers 111a1 to 111an of the first multi-core fiber 111. Therefore, regarding the signal light propagated along the fiber core 111a1 closest to mark 111c in the first multi-core fiber 111, degradation caused by mark 112c is less likely to occur in the second multi-core fiber 112. Therefore, the possibility of errors occurring in communications using signal light propagated along the first fiber core 111a1 closest to mark 111c in the first multi-core fiber 111 can be reduced.

[0045] In addition, Figure 2In the connection pattern shown in (d), the first fiber core 111a1, which is closest to mark 111c in the first multi-core fiber 111, is connected to the fourth fiber core 112a4, which is second only to the third fiber core 112a3 and furthest from mark 112c in the second multi-core fiber 112. Furthermore, the second fiber core 111a2, which is second only to the first fiber core 111a1 and closest to mark 111c in the first multi-core fiber 111, is connected to the third fiber core 112a3, which is furthest from mark 112c in the second multi-core fiber 112. This allows for more uniform degradation of the signal light propagated in each fiber core 111a1 of the first multi-core fiber 111. This is because the first fiber core 111a1, whose optical properties are most prone to degradation in the first multi-core fiber 111, is connected to the fourth fiber core 112a4, whose optical properties are less prone to degradation in the second multi-core fiber 112. Furthermore, the reason is that in the first multi-core fiber 111, the second core 111a2, whose optical properties are second most prone to degradation, is connected to the third core 112a3, whose optical properties are least prone to degradation, in the second multi-core fiber 112. As a result, the possibility of errors occurring in communications that use signal light transmitted in each core 111a3 of the first multi-core fiber 111 can be further reduced.

[0046] (Modified Example) also, Figure 1 The fiber optic connector 101 shown is composed of two multi-core optical fibers 111 and 112, but it is not limited to this. That is, the fiber optic connector 101 can be composed of three or more multi-core optical fibers. Referring below... Figure 3 and Figure 4 The optical fiber connector 101, which consists of three multi-core optical fibers 111 to 113, will be described.

[0047] Figure 3 These are side views and cross-sectional views showing a first modified example of the fiber optic connector 101 (hereinafter referred to as fiber optic connector 101A). Furthermore, Figure 3 The AA' section of the first multi-core optical fiber 111 shown is from... Figure 3 Observing from the right side of the middle, relatively speaking, Figure 3 The BB' section of the second multi-core optical fiber 112 shown is from... Figure 3 Observe from the left side. Additionally, Figure 3 The CC' section of the second multi-core optical fiber 111 shown is from... Figure 3 Observing from the right side of the middle, relatively speaking, Figure 3 The DD' section of the third multi-core optical fiber 113 shown is from... Figure 3 Observe from the left side of the middle.

[0048] like Figure 3As shown, the optical fiber connector 101A includes a first multi-core optical fiber 111, a second multi-core optical fiber 112, and a third multi-core optical fiber 113. One end face 111R of the first multi-core optical fiber 111 is connected to one end face 112L of the second multi-core optical fiber 112. The other end face 112R of the second multi-core optical fiber 112 is connected to one end face 113L of the third multi-core optical fiber 113. The structures of the first multi-core optical fiber 111 and the second multi-core optical fiber 112 are as described above.

[0049] The third multi-core optical fiber 113 comprises n cores 113a1 to 113an and a cladding 113b. The cladding 113b is a cylindrical component. The cladding 113b is, for example, made of quartz glass. Each core 113ai is a cylindrical region disposed within the cladding 113b and extending in the same direction as the cladding 113b, having a higher refractive index than the cladding 113b. Each core 113ai is, for example, made of quartz glass to which rising dopants such as germanium are added. The number of cores 113a1 to 113n is the same as the number of cores 111a1 to 111an in the first multi-core optical fiber 111. Furthermore, the diameters of the cores 113a1 to 113an are the same as the diameters of the cores 111a1 to 111an in the first multi-core optical fiber 111. Furthermore, the arrangement of the fiber cores 113a1 to 113an is determined in the same way as the arrangement of the fiber cores 111a1 to 111an in the first multi-core fiber 111, such that their cross-sections are arranged at equal intervals on a circle of radius R starting from the center of the cladding 113b.

[0050] The third multi-core optical fiber 113 also includes a marker 113c. The marker 113c is a region located inside the cladding 113b and extending in the same direction as the cladding 113b, with a refractive index different from that of the cladding 113b. The shape of the marker 113c is arbitrary, such as cylindrical, triangular prism, etc. The marker 113c may be made of, for example, quartz glass with added descending dopants such as fluorine. In this case, the refractive index of the marker 113c is lower than that of the cladding 113b. Alternatively, the marker 113c may be made of quartz glass with added ascending dopants such as germanium, aluminum, phosphorus, chlorine, etc. In this case, the refractive index of the marker 113c is higher than that of the cladding 113b. The marker 113c can be formed using methods such as aperture drilling or stacking.

[0051] The configuration of marker 113c in the third multi-core optical fiber 113 is determined in the same manner as the configuration of marker 111c in the first multi-core optical fiber 111. In addition, the ordinal numbers of the cores 113a1 to 113an in the third multi-core optical fiber 113 are determined in the same manner as the ordinal numbers of the cores 111a1 to 111an in the first multi-core optical fiber 111.

[0052] In the optical fiber connector 101A, the first multi-core optical fiber 111 and the second multi-core optical fiber 112 are connected in a manner that satisfies conditions 1, 2, and 3A as described above. Furthermore, in the optical fiber connector 101A, the second multi-core optical fiber 112 and the third multi-core optical fiber 113 are connected in a manner that satisfies condition 4 below.

[0053] Condition 4: The i-th core 113ai of the third multi-core optical fiber 113 is connected to the cores 112a1 to 112an of the second multi-core optical fiber 112, which are connected to the i-th core 111ai of the first multi-core optical fiber 111.

[0054] Specifically, the first core 113a1 of the third multi-core optical fiber 113 is connected to the third core 112a3 of the second multi-core optical fiber 112 (cores 112a1 to 112an) that is connected to the first core 111a1 of the first multi-core optical fiber 111. Furthermore, the second core 113a2 of the third multi-core optical fiber 113 is connected to the fourth core 112a4 of the second multi-core optical fiber 112 (cores 112a1 to 112an) that is connected to the second core 111a2 of the first multi-core optical fiber 111. Additionally, the third core 113a3 of the third multi-core optical fiber 113 is connected to the first core 112a1 of the second multi-core optical fiber 112 (cores 112a1 to 112an) that is connected to the third core 111a3 of the first multi-core optical fiber 111. In addition, the fourth core 113a4 of the third multi-core optical fiber 113 is connected to the second core 112a2 of the cores 112a1 to 112an of the second multi-core optical fiber 112, which is connected to the fourth core 111a4 of the first multi-core optical fiber 111.

[0055] Therefore, the optical signal input from the i-th core 111ai of the first multi-core fiber 111 is output from the i-th core 113ai of the third multi-core fiber 113. Since the core numbers are the same in both the input and output of the optical signal, it is less likely to cause incorrect wiring when fan-in and fan-out, or transmitters, receivers, and repeaters are connected to the first multi-core fiber 111 and the third multi-core fiber 113, respectively.

[0056] Furthermore, the connection pattern between the first multi-core optical fiber 111 and the second multi-core optical fiber 112 is set as follows: Figure 1 The connection pattern shown is not limited to this. The connection pattern between the first multi-core optical fiber 111 and the second multi-core optical fiber 112 can also be... Figure 2 The connection patterns shown.

[0057] Figure 4 These are side views and cross-sectional views of a second modified example of the optical fiber connector 101 (hereinafter referred to as optical fiber connector 101B).

[0058] like Figure 4As shown, the optical fiber connector 101B includes a first multi-core optical fiber 111, a second multi-core optical fiber 112, and a third multi-core optical fiber 113. One end face 111R of the first multi-core optical fiber 111 is connected to one end face 112L of the second multi-core optical fiber 112. The other end face 112R of the second multi-core optical fiber 112 is connected to one end face 113L of the third multi-core optical fiber 113. The structures of the first multi-core optical fiber 111, the second multi-core optical fiber 112, and the third multi-core optical fiber 113 are as described above.

[0059] In the optical fiber connector 101B, the first multi-core optical fiber 111 and the second multi-core optical fiber 112 are connected in a manner that satisfies conditions 1, 2, and 3A as described above. Furthermore, in the optical fiber connector 101B, the second multi-core optical fiber 112 and the third multi-core optical fiber 113 are connected in a manner that satisfies condition 5 as described below.

[0060] Condition 5: The first core 113a1 closest to mark 113c in the third multi-core fiber 113 is connected to the cores 112a1 to 112an of the second multi-core fiber 112, which satisfies the following (1) and (2): (1) The core is other than the first core 112a1 closest to mark 112c, and (2) The core is other than the third core 112a3 connected to the first core 111a1 closest to mark 111c in the first multi-core fiber 111 (specifically the fourth core 112a4).

[0061] Therefore, regarding the signal light propagating along the first core 111a1 closest to mark 111c in the first multi-core fiber 111, the degradation caused by mark 112c in the second multi-core fiber 112 can be suppressed, and the degradation caused by mark 113c in the third multi-core fiber 113 can also be suppressed. Furthermore, regarding the signal light propagating along the first core 112a1 closest to mark 112c in the second multi-core fiber 112, the degradation caused by mark 111c in the first multi-core fiber 111 can also be suppressed, and the degradation caused by mark 113c in the third multi-core fiber 113 can also be suppressed.

[0062] (Second implementation of the first aspect) (Structure of fiber optic connector) Reference Figure 5 The structure of the optical fiber connector 102 according to the second embodiment of the first aspect of the present invention will be described. Figure 5 These are side views and cross-sectional views showing the structure of the optical fiber connector 102.

[0063] like Figure 5As shown, the optical fiber connector 102 includes a first multi-core optical fiber 121 and a second multi-core optical fiber 122. One end face 121R of the first multi-core optical fiber 121 is connected (in this embodiment, fused) to one end face 122L of the second multi-core optical fiber 122.

[0064] The first multi-core optical fiber 121 comprises n (n is a natural number greater than or equal to 3) cores 121a1 to 121an and a cladding 121b. The cladding 121b is a cylindrical component. The cladding 121b is, for example, made of quartz glass. Each core 121ai (i is a natural number greater than or equal to 1 and less than n) is a cylindrical region disposed inside the cladding 121b and having a higher refractive index than the cladding 121b, extending in the same direction as the cladding 121b. Each core 121ai is, for example, made of quartz glass to which a rising dopant such as germanium is added. The cores 121a1 to 121an are arranged such that their cross-sectional centers are equally spaced on a circle of radius R starting from the center of the cladding 121b.

[0065] The first multi-core optical fiber 121 also includes a marker 121c. The marker 121c is a region located inside the cladding 121b and extending in the same direction as the cladding 121b, with a refractive index different from that of the cladding 121b. The shape of the marker 121c is arbitrary, such as cylindrical, triangular prism, etc. The marker 121c may be made of, for example, quartz glass with added descending dopants such as fluorine. In this case, the refractive index of the marker 121c is lower than that of the cladding 121b. Alternatively, the marker 121c may be made of quartz glass with added ascending dopants such as germanium, aluminum, phosphorus, chlorine, etc. In this case, the refractive index of the marker 121c is higher than that of the cladding 121b. The marker 121c can be formed using, for example, a hole-punching method or a stacking method.

[0066] Regarding the configuration of marker 121c in the first multi-core optical fiber 121, the distance from marker 121c to fiber core 121ai is set as di, and determined in such a way that d1, d2, ..., dn are all different. This is to facilitate the identification of fiber cores 121a1 to 121an based on the distance from marker 121c. This allows for more reliable identification of each fiber core, for example, enabling the measurement of the characteristics of a specific fiber core. Furthermore, the ordinal numbers of fiber cores 121a1 to 121an in the first multi-core optical fiber 121 can be determined based on their positional relationship with marker 121c as follows: That is, among fiber cores 121a1 to 121an, the fiber core closest to marker 121c is designated as the first fiber core 121a1. Additionally, among fiber cores 121a1 to 121an, the fiber core that is closer to marker 121c among the two adjacent fiber cores of the first fiber core 121a1 is designated as the second fiber core 121a2. The ordinal numbers of the remaining fiber cores 121a3 to 121an are determined according to their arrangement order on the aforementioned circle of radius R. For example, the fiber core that is not the first fiber core 121a1 among the two fiber cores adjacent to the second fiber core 121a2 is designated as the third fiber core 121a3. Furthermore, the fiber core that is not the second fiber core 121a2 among the two fiber cores adjacent to the third fiber core 121a3 is designated as the fourth fiber core 121a4.

[0067] The second multi-core optical fiber 122 includes n cores 122a1 to 122an and a cladding 122b. The cladding 122b is a cylindrical component. The cladding 122b is, for example, made of quartz glass. Each core 122ai is a cylindrical region disposed within the cladding 122b and extending in the same direction as the cladding 122b, having a higher refractive index than the cladding 122b. Each core 122ai is, for example, made of quartz glass with added rising dopants such as germanium. The number of cores 122a1 to 122an is the same as the number of cores 121a1 to 121an in the first multi-core optical fiber 121. Furthermore, the diameters of the cores 122a1 to 122an are the same as the diameters of the cores 121a1 to 121an in the first multi-core optical fiber 121. Furthermore, the arrangement of fiber cores 122a1 to 122an is determined in the same manner as the arrangement of fiber cores 121a1 to 121an in the first multi-core fiber 121, such that their cross-sections are arranged at equal intervals on a circle of radius R starting from the center of the cladding 122b.

[0068] The second multi-core optical fiber 122 also includes a marker 122c. The marker 122c is a region located inside the cladding 122b and extending in the same direction as the cladding 122b, with a refractive index different from that of the cladding 122b. The shape of the marker 122c is arbitrary, such as cylindrical, triangular prism, etc. The marker 122c may be made of, for example, quartz glass with added descending dopants such as fluorine. In this case, the refractive index of the marker 122c is lower than that of the cladding 122b. Alternatively, the marker 122c may be made of quartz glass with added ascending dopants such as germanium, aluminum, phosphorus, chlorine, etc. In this case, the refractive index of the marker 122c is higher than that of the cladding 122b. The marker 122c can be formed using methods such as aperture drilling or stacking.

[0069] The configuration of marker 122c in the second multi-core optical fiber 122 is determined in the same manner as the configuration of marker 121c in the first multi-core optical fiber 121. Furthermore, the ordinal numbers of the cores 122a1 to 122an in the second multi-core optical fiber 122 are determined in the same manner as the ordinal numbers of the cores 121a1 to 121an in the first multi-core optical fiber 121.

[0070] also, Figure 5 The AA' section of the first multi-core optical fiber 121 shown is from... Figure 5 Observing from the right side of the middle, relatively speaking, Figure 5 The BB' section of the second multi-core optical fiber 122 shown is from... Figure 5 Observe from the left side. Therefore, in the connection between one end face 121R and one end face 122L, the AA' section of the first multi-core optical fiber 121... Figure 5 The right end of the middle and the BB' section of the second multi-core fiber 122 Figure 5 The left ends of the first multi-core optical fiber 121 are interconnected, and the AA' section of the first multi-core optical fiber 121 is also connected. Figure 5 The left end of the middle and the BB' section of the second multi-core fiber 122 Figure 5 The right ends of the two are connected to each other.

[0071] In the optical fiber connector 102 of this embodiment, the first multi-core optical fiber 121 and the second multi-core optical fiber 122 are connected in a manner that satisfies the following conditions.

[0072] Condition 1: Each core 122ai of the second multi-core optical fiber 122 is connected to any one of the cores 121a1 to 121an of the first multi-core optical fiber 121.

[0073] Condition 2: Mark 122c of the second multi-core optical fiber 122 is connected to the portion of the first multi-core optical fiber 121 other than mark 121c.

[0074] Furthermore, the optical fiber connector 102 of this embodiment satisfies the following conditions.

[0075] Condition 3B: The pair consisting of the first fiber core 122a1 closest to mark 122c and the second closest fiber core 122a2 in the second multi-core fiber 122 is connected to: the pair consisting of the first fiber core 121a1 closest to mark 121c and the second closest fiber core 121a2 in the first multi-core fiber 121 (specifically the pair consisting of the third fiber core 121a3 and the second fiber core 121a2).

[0076] (Effect of the fiber optic connector) In multi-core optical fibers, markings between adjacent cores suppress light transmission from one core to the other. This reduces crosstalk between the core closest to the mark and the second closest core to the mark.

[0077] In existing fiber optic connectors, a pair consisting of the closest marked core and the second closest core in a first multi-core fiber is connected to a pair consisting of the closest marked core and the second closest core in a second multi-core fiber. As a result, the number of core pairs that can achieve the effect of reducing crosstalk is limited to one pair.

[0078] In contrast, in the fiber optic connector 102 of this embodiment, a pair consisting of the first fiber core 121a1 closest to mark 121c and the second closest fiber core 121a2 in the first multi-core fiber 121 is connected to a pair other than the pair consisting of the first fiber core 122a1 closest to mark 122c and the second closest fiber core 122a2 in the second multi-core fiber 122 (specifically, a pair consisting of the second fiber core 122a2 and the third fiber core 122a3). Therefore, these fiber core pairs can achieve the effect of reducing crosstalk.

[0079] Furthermore, in the fiber optic connector 102 of this embodiment, a pair consisting of the first fiber core 122a1 closest to mark 122c and the second closest fiber core 122a2 in the second multi-core fiber 122 is connected to a pair other than the pair consisting of the first fiber core 121a1 closest to mark 121c and the second closest fiber core 122a2 in the first multi-core fiber 121 (specifically, a pair consisting of the third fiber core 121a3 and the second fiber core 121a2). Therefore, these fiber core pairs can also achieve the effect of reducing crosstalk.

[0080] As described above, the fiber optic connector 102 according to this embodiment increases the number of fiber core pairs that can achieve the effect of reducing crosstalk. Here, when the fiber core sequence in each multi-core fiber is determined according to the fiber core arrangement order, with the fiber core closest to the mark as the first and the fiber core second closest to the mark as the second, when there are multiple second closest fiber cores, any pair can be selected, and each pair can achieve the same effect.

[0081] Furthermore, when the refractive indices of the markers 121c and 122c are lower than those of the cladding layers 121b and 122b, the fiber optic connector 102 of this embodiment has the following advantages: It can more effectively suppress light transmission from the first fiber cores 121a1 and 122a1 to the second fiber cores 121a2 and 22a2, and light transmission from the second fiber cores 121a2 and 22a2 to the first fiber cores 121a1 and 122a1. Therefore, the effect of reducing crosstalk can be further improved. Conversely, when the refractive indices of the markers 121c and 122c are higher than those of the cladding layers 121b and 122b, the fiber optic connector 102 of this embodiment has the following advantages: The light collected by the markers 121c and 122c propagates in the first multi-core fiber 121 and the second multi-core fiber 122, which is advantageous depending on the propagation distance and fiber parameters. Alternatively, due to the deterioration of crosstalk between the first fiber cores 121a1, 122a1 and the second fiber cores 121a2, 122a2, which are close to the markings 121c, 122c, the pairs with poor crosstalk characteristics are dispersed, thus reducing crosstalk for the multi-core fiber as a whole, which is beneficial.

[0082] (Changes in the connecting pattern) Connection patterns that meet conditions 1, 2, and 3B above are not limited to Figure 5 The connection pattern shown. In Figure 6 The diagram shows conditions 1, 2, and 3B that are satisfied above. Figure 5 Other connection patterns besides the one shown.

[0083] Figure 6 (a) represents a connection pattern in which a pair consisting of the first fiber core 121a1, which is closest to mark 121c, and the second fiber core 121a2, which is closest to mark 121c, is connected to a pair consisting of the third fiber core 122a3 and the fourth fiber core 122a4 of the second multi-core fiber 122. The pair consisting of the first fiber core 122a1, which is closest to mark 122c, and the second fiber core 122a2, which is closest to mark 122c, is connected to a pair consisting of the third fiber core 121a3 and the fourth fiber core 121a4 of the first multi-core fiber 121.

[0084] Figure 6(b) represents a connection pattern in which a pair consisting of the first fiber core 121a1, which is closest to mark 121c, and the second fiber core 121a2, which is closest to mark 121c, is connected to a pair consisting of the fourth fiber core 122a4 and the first fiber core 122a1 of the second multi-core fiber 122. A pair consisting of the first fiber core 122a1, which is closest to mark 122c, and the second fiber core 122a2, which is closest to mark 122c, is connected to a pair consisting of the second fiber core 121a2 and the third fiber core 121a3 of the first multi-core fiber 121.

[0085] Figure 6 (c) represents a connection pattern in which a pair consisting of the first fiber core 121a1, which is closest to mark 121c, and the second fiber core 121a2, which is closest to mark 121c, is connected to a pair consisting of the first fiber core 122a1 and the fourth fiber core 122a4 of the second multi-core fiber 122. Similarly, a pair consisting of the first fiber core 122a1, which is closest to mark 122c, and the second fiber core 122a2, which is closest to mark 122c, is connected to a pair consisting of the first fiber core 121a1 and the fourth fiber core 121a4 of the first multi-core fiber 121.

[0086] Figure 6 (d) represents a connection pattern in which the pair consisting of the first fiber core 121a1, which is closest to mark 121c, and the second fiber core 121a2, which is closest to mark 121c, are connected to the pair consisting of the fourth fiber core 122a4 and the third fiber core 122a3 of the second multi-core fiber 122. The pair consisting of the first fiber core 122a1, which is closest to mark 122c, and the second fiber core 122a2, which is closest to mark 122c, in the second multi-core fiber 122 are connected to the pair consisting of the fourth fiber core 121a4 and the third fiber core 121a3 of the first multi-core fiber 121.

[0087] Figure 6 (e) represents a connection pattern in which a pair consisting of the first fiber core 121a1, which is closest to mark 121c, and the second fiber core 121a2, which is closest to mark 121c, is connected to a pair consisting of the third fiber core 122a3 and the second fiber core 122a2 of the second multi-core fiber 122. The pair consisting of the first fiber core 122a1, which is closest to mark 122c, and the second fiber core 122a2, which is closest to mark 122c, of the second multi-core fiber 122 is connected to a pair consisting of the third fiber core 121a3 and the second fiber core 121a2 of the first multi-core fiber 121.

[0088] exist Figure 6In any of the connection patterns shown in (a) to (e), a pair consisting of the first fiber core 121a1 closest to mark 121c and the second fiber core 121a2 closest to mark 121c in the first multi-core fiber 121 is connected to a pair other than the pair consisting of the first fiber core 122a1 closest to mark 122c and the second fiber core 122a2 closest to mark 122c in the second multi-core fiber 122. Therefore, these fiber core pairs can achieve the effect of reducing crosstalk.

[0089] In addition, Figure 6 In any of the connection patterns shown in (a) to (e), a pair consisting of the first fiber core 122a1 closest to mark 122c and the second closest fiber core 122a2 in the second multi-core fiber 122 is connected to any other pair except for the pair consisting of the first fiber core 121a1 closest to mark 121c and the second closest fiber core 122a2 in the first multi-core fiber 121. Therefore, these fiber core pairs can also achieve the effect of reducing crosstalk.

[0090] As mentioned above, in Figure 6 In any of the connection patterns shown in (a) to (e), the fiber core pairs that achieve the effect of reducing crosstalk are two pairs.

[0091] (Supplementary information regarding tag configuration) like Figure 7 As shown in (a), preferably, the marker 121c in the first multi-core optical fiber 121 is disposed inside region A sandwiched between the first core 121a1 and the second core 121a2. Typically, the intensity of light leaking from the first core 121a1 has a concentric Gaussian distribution in the cross-section of the first multi-core optical fiber 121. The magnitude of crosstalk between the first core 121a1 and the second core 121a2 in the multi-core optical fiber 121 is determined by the overlap integral of the intensity distribution of light leaking from the first core 121a1 and the intensity distribution of light leaking from the second core 121a2. This is because: by employing... Figure 7 The configuration shown in (a) can suppress light blockage in areas with high light intensity, and can most effectively reduce crosstalk. The same applies to the configuration of mark 122c in the second multi-core fiber 122.

[0092] It should be noted that the position of marker 121c in the first multi-core optical fiber 121 is not limited to this. For example, marker 121c in the first multi-core optical fiber 121 can also be positioned as follows: Figure 7 As shown in (b), it is disposed on the boundary of region A sandwiched between the first fiber core 121a1 and the second fiber core 121a2. This is because: although compared with the use of Figure 7 The configuration shown in (a) is relatively poor, but using Figure 7The configuration shown in (b) also achieves the effect of reducing crosstalk. Additionally, as... Figure 7 As shown in (c), the marker 121c in the first multi-core optical fiber 121 can also be positioned near region A sandwiched between the first fiber core 121a1 and the second fiber core 121a2. This is because: although compared with the use of Figure 7 The configuration shown in (a) and Figure 7 The configuration shown in (b) is relatively poor, but using Figure 7 The configuration shown in (c) also achieves the effect of reducing crosstalk. Additionally, as... Figure 7 As shown in (d), the marker 121c in the first multi-core fiber 121 can also be configured at a location separate from region A sandwiched between the first fiber core 121a1 and the second fiber core 121a2. This is because: although compared with the use of Figure 7 The configuration shown in (a) Figure 7 The configuration shown in (b) and Figure 7 The configuration shown in (c) is relatively poor, but using Figure 7 The configuration shown in (d) also achieves the effect of reducing crosstalk. The same applies to the configuration of mark 122c in the second multi-core fiber 122.

[0093] (Modified Example) also, Figure 5 The fiber optic connector 102 shown can be fitted with optical connectors at both ends. Hereinafter, refer to... Figure 8 The fiber optic connector 102, which is equipped with an optical connector, will be described.

[0094] Figure 8 These are side views and cross-sectional views showing a modified example of the fiber optic connector 102. Furthermore, Figure 8 The EE' section of frame 141 shown in (b) and (c) is from... Figure 8 Observing from the right side of (a), relatively speaking, Figure 8 The FF' section of frame 142 shown in (b) and (c) is from... Figure 8 Observe the left side of (a).

[0095] like Figure 8 As shown in (a), the end face of the first multi-core optical fiber 121 on the second multi-core optical fiber 122 side is covered by a metal ring 131, and the metal ring 131 is covered by a frame 141. Similarly, the end face of the second multi-core optical fiber 122 on the first multi-core optical fiber 121 side is covered by a metal ring 132, and the metal ring 132 is covered by a frame 142. Protrusions referred to as connecting keys 141a and 142a are provided on the outer surfaces of the frames 141 and 142.

[0096] In this case, the fiber optic connector is constructed according to the following procedure. First, as follows... Figure 8 As shown in (b) or (c), the position of the connecting key 141a of frame 141 is aligned with the position of the connecting key 142a of frame 142. Next, after fitting each connecting key into the connecting keyway of the adapter (not shown) and aligning them, frame 141 and frame 142 are connected to each other. Thus, the first multi-core optical fiber 121 and the second multi-core optical fiber 122 are connected to form an optical fiber connector. Furthermore, the optical fiber connector can be understood to have the following structure: It further includes a frame 141 located at the end of the first multi-core optical fiber 121 on the second multi-core optical fiber 122 side, and a frame 142 located at the end of the second multi-core optical fiber 122 on the first multi-core optical fiber 121 side. The position of the connecting key 141a on the surface of frame 141 is aligned with the position of the fiber core 121a1 closest to mark 121c, and the position of the connecting key 142a on the surface of frame 142 is aligned with the position of the fiber core 122a1 closest to mark 121c. Based on the above structure, if the two connecting keys are aligned and connected, the first multi-core fiber 121 and the second multi-core fiber 122 are appropriately connected. Therefore, an optical fiber connector can be realized that allows for easy and appropriate connection between the first multi-core fiber and the second multi-core fiber.

[0097] Furthermore, the aforementioned multi-core fiber connector 101 can also be configured to satisfy either condition α1 or condition α2. As an example, in... Figure 19 The end faces of the first multi-core fiber 111 and the second multi-core fiber 112 in the multi-core fiber connector 101 that satisfies both conditions α1 and α2 are shown.

[0098] Condition α1: Only a portion of the mark 112c of the second multi-core fiber 112 is connected to the portion of the first multi-core fiber 111 other than the mark 111c (cladding 111b, etc.).

[0099] Condition α2: Only a portion of the marking 111c of the first multi-core fiber 111 is connected to the portion of the second multi-core fiber 112 other than the marking 112c (cladding 111b, etc.).

[0100] In the first multi-core optical fiber 111, if the marker 111c is at least close to the core 111a1 closest to the marker 111c, the gap between the marker material and the cladding material in the parent material and the multi-core optical fiber 111 may be compressed and damaged. When the parent material of the multi-core optical fiber 111 is drawn and cooled, the glass around the marker 111c may deform due to the difference in linear expansion coefficients between the marker 111c and the cladding 111b. Furthermore, since the core 111a1 closest to the marker 111c is subjected to stress and deforms, a characteristic degradation problem occurs: the characteristics of the core 111a1 closest to the marker 111c as an optical waveguide may deteriorate. Examples of characteristics that may deteriorate in the core closest to the marker include polarization mode dispersion. The same applies to the second multi-core optical fiber 112. When conditions α1 or α2 are satisfied, compared to the case where conditions α1 and α2 are not satisfied (the case where markers 111c and 112c do not overlap (the case where conditions δ1 and δ2 described later are satisfied)), it is possible to separate marker 111c from at least the core 111a1 closest to marker 111c in the first multi-core fiber 111, and to separate marker 112c from at least the core 112a1 closest to marker 112c in the second multi-core fiber 112. In this case, the aforementioned characteristic degradation problem can be suppressed (hereinafter sometimes referred to as the effect of the former). In addition, compared to the case of radial separation, it is possible to suppress the increase in the thickness of cladding 111b or the deformation of cladding 111b caused by manufacturing processes, etc. (hereinafter sometimes referred to as the effect of the latter). For condition α2, the second multi-core fiber 112 can also obtain the same effect.

[0101] Furthermore, the multi-core fiber connector 101 described above can be configured to satisfy either condition α1 or condition α2, or it can be configured to satisfy condition β1 or β2. As an example, in... Figure 20 The diagram shows the end faces of the first multi-core fiber 111 and the second multi-core fiber 112 in a multi-core fiber connector 101 that satisfies both conditions β1 and β2.

[0102] Condition β1: In the end face of the first multi-core optical fiber 111, the mark 111c coincides with the virtual vertical bisecting line of the virtual line segment connecting the center of the core 111a1 closest to the mark 111c and the center of the second closest core 111a2 among the cores 111a1 to 111a4 of the first multi-core optical fiber 111.

[0103] Condition β2: In the end face of the second multi-core optical fiber 112, the mark 112c coincides with the virtual vertical bisecting line of the virtual line segment connecting the center of the core 112a1 closest to the mark 112c and the center of the second closest core 12a2 among the cores 112a1 to 112a4 of the second multi-core optical fiber 112.

[0104] When either condition β1 or condition β2 is satisfied, in the first multi-core fiber 111, the marker 111c can be further separated from the core 111a1 closest to the marker 111c, and in the second multi-core fiber 112, the marker 112c can be further separated from the core 112a1 closest to the marker 112c. Therefore, the aforementioned characteristic degradation problem that occurs when the marker 111c is at least close to the core 111a1 and when the marker 112c is at least close to the core 112a1 can be suppressed.

[0105] Furthermore, the aforementioned condition β1 can be the following condition β1', and condition β2 can be the following condition β2'. In this case, in the first multi-core fiber 111, the marker 111c can be further separated from the fiber cores 111a1 to a4, and in the second multi-core fiber 112, the marker 112c can be further separated from the fiber cores 112a1 to 112a4. Therefore, the aforementioned characteristic degradation problems that occur when the marker 111c is close to the fiber cores 111a1 to 111a4 and when the marker 112c is close to the fiber cores 112a1 to 112a4 can be further suppressed.

[0106] Condition β1': In the end face of the first multi-core optical fiber 111, the center of the mark 111c can coincide with the virtual vertical bisecting line of the virtual line segment connecting the center of the fiber core 111a1 to 111a4 of the first multi-core optical fiber 111, which is closest to the mark 111c, and the center of the second closest fiber core 111a2.

[0107] Condition β2': In addition, in the end face of the second multi-core optical fiber 112, the center of the mark 112c coincides with the virtual vertical bisecting line of the virtual line segment that connects the center of the fiber core 112a1 closest to the mark 112c and the center of the second closest fiber core 12a2 among the fiber cores 112a1 to 112a4 of the second multi-core optical fiber 112.

[0108] Furthermore, the aforementioned multi-core fiber optic connector 101 can also be configured to satisfy condition γ1 or γ2 as described below. Additionally, besides condition α1 or condition α2 as described above, it can also be configured to satisfy condition γ1 or γ2 as described below. Furthermore, besides condition α1 or condition α2 and conditions β1, β1', β2, or β2' as described above, it can also be configured to satisfy condition γ1 or γ2 as described below. As an example, in... Figure 21 (a) shows the end faces of the first multi-core fiber 111 and the second multi-core fiber 112 in the multi-core fiber connector 101 that satisfies both conditions γ1 and γ2.

[0109] Condition γ1: In the end face of the first multi-core optical fiber 111, the center of the mark 111c does not coincide with the virtual vertical bisecting line of the virtual line segment connecting the center of the virtual core 111a1 (closest to the mark 111c) and the center of the second closest core 111a2 among the cores 111a1 to 111a4 of the first multi-core optical fiber 111.

[0110] Condition γ2: In the end face of the second multi-core optical fiber 112, the center of the mark 112c does not coincide with the virtual vertical bisecting line of the virtual line segment connecting the center of the virtual core 112a1 closest to the mark 112c and the center of the second virtual core 112a2 among the cores 112a1 to 112a4 of the second multi-core optical fiber 112.

[0111] In this case, the center of marker 111c or the center of marker 112c will be offset from the aforementioned virtual vertical bisector. Therefore, compared to the case where marker 111c of the first multi-core fiber 111 and marker 112c of the second multi-core fiber 112 completely coincide, or the case where the center of marker 111c and the center of marker 112c coincide with the aforementioned virtual vertical bisector, the identification of the end face of the first multi-core fiber 111 and the end face of the second multi-core fiber 112, or the identification of the fiber core number of the first multi-core fiber 111, or the identification of the fiber core number of the second multi-core fiber 112 becomes easier. As a result, the connection of the first multi-core fiber 111 or the second multi-core fiber 112 to external transceivers and external fan-in / fan-out devices becomes easier.

[0112] Furthermore, the aforementioned multi-core fiber optic connector 101 can also be configured to satisfy the following condition η. As an example, in... Figure 21 (b) shows the end faces of the first multi-core fiber 111 and the second multi-core fiber 112 in the multi-core fiber connector 101 that satisfies condition η.

[0113] Condition η: In one end face of the first multi-core fiber 111 or one end face of the second multi-core fiber 112, the virtual straight line connecting the center of mark 111c of the first multi-core fiber 111 and the center of mark 112c of the second multi-core fiber 112 is parallel to: the virtual straight line connecting the center of the fiber core 111a1 closest to mark 111c and the center of the second closest fiber core 111a2 in the end face of the first multi-core fiber 111, or the virtual straight line connecting the center of the fiber core 112a1 closest to mark 112c and the center of the second closest fiber core 112a2 in the end face of the second multi-core fiber 112.

[0114] In this case, similarly to the effects described above, the identification of the end face of the first multi-core fiber 111 and the end face of the second multi-core fiber 112, or the identification of the fiber core number of the first multi-core fiber 111, or the identification of the fiber core number of the second multi-core fiber 112, becomes easier. Therefore, the connection between the first multi-core fiber 111 or the second multi-core fiber 112 and external transceivers or external fan-in / fan-out devices becomes easier. Furthermore, compared to the case where the virtual straight lines connecting the two marks 111c and 112c are not parallel, since at least one of the two marks 111c and 112c can separate from the outer periphery of the cladding 111b and 112b, it is possible to suppress the increase in the thickness of the cladding 111b and 112b, or deformation of the cladding 111b and 112b during manufacturing, etc.

[0115] In addition, the aforementioned multi-core fiber connector 101 can also be used as follows: Figure 1 As shown, it is constructed in a manner that satisfies either condition δ1 or condition δ2.

[0116] Condition δ1: Mark 112c of the second multi-core optical fiber 112 is connected to the part of the first multi-core optical fiber 111 other than mark 111c (cladding 111b, etc.).

[0117] Condition δ2: Mark 111c of the first multi-core optical fiber 111 is connected to the part of the second multi-core optical fiber 112 other than mark 112c (cladding 111b, etc.).

[0118] Compared to cases where the smaller marker 111c is connected to the smaller marker 112c, or where marker 111c is connected across marker 112c and cladding 112b, connecting marker 111c only to the larger cladding 111b reduces (mitigates) the stress on marker 111c. This helps to suppress damage to marker 111c. The same applies to marker 112c.

[0119] In addition, such as Figure 7 (b) or Figure 7As shown in (c), the multi-core fiber connector 101 described above can be configured to satisfy either condition ε1 or condition ε2.

[0120] Condition ε1: In the end face of the first multi-core fiber 111, the center of the mark 111c is located in the area enclosed by the following three conditions (1) to (3) (hereinafter also referred to as area B): (1) The virtual circumscribed circle of the fiber 111a1 closest to the mark 111c and the second closest fiber 111a2 among the multiple fiber cores 111a1 to 111a4 of the first multi-core fiber 111, that is, the virtual circumscribed circle centered on the center of the cladding 111b of the first multi-core fiber 111. (1) Circle; (2) Virtual bisecting line of the angle formed by the virtual straight line passing through the center of the fiber core 111a1 closest to mark 111c and the center of the second closest fiber core 111a2 and the virtual straight line passing through the center of the fiber core 111a1 and the center of the cladding 111b; (3) Virtual bisecting line of the angle formed by the virtual straight line passing through the center of the fiber core 111a1 and the center of the fiber core 111a2 and the virtual straight line connecting the center of the fiber core 111a2 and the center of the cladding 111b.

[0121] Condition ε2: In the end face of the second multi-core fiber 112, the center of the mark 112c is located in the region enclosed by the following three conditions (1) to (3) (hereinafter also referred to as region C): (1) the virtual circumscribed circle of the fiber 112a1 closest to the mark 112c and the second closest fiber 112a2 among the multiple fiber cores 112a1 to 112a4 of the second multi-core fiber 112, that is, the virtual circumscribed circle centered on the center of the cladding 112b of the second multi-core fiber 112. (1) Circle; (2) Virtual bisecting line of the angle formed by the virtual straight line passing through the center of the fiber core 112a1 closest to mark 112c and the center of the second closest fiber core 112a2 and the virtual straight line passing through the center of the fiber core 112a1 and the center of the cladding 112b; (3) Virtual bisecting line of the angle formed by the virtual straight line passing through the center of the fiber core 112a1 and the center of the fiber core 112a2 and the virtual straight line connecting the center of the fiber core 112a2 and the center of the cladding 112b.

[0122] In this case, in the first multi-core fiber 111, both the effects of the former and the latter can be obtained. In particular, compared with the cases of condition ζ1 or condition ζ2 described later, since the mark 111c is disposed at a position separated from the outer periphery of the cladding 111b, it is possible to suppress the increase in the thickness of the cladding 111b and 112b, or the deformation of the cladding 111b during manufacturing, etc. Therefore, in particular, the latter effect can be further enhanced. The same applies to the second multi-core fiber 112.

[0123] In addition, the multi-core fiber connector 101 described above can also be configured to satisfy either condition ζ1 or condition ζ2.

[0124] Condition ζ1: In the end face of the first multi-core fiber 111, the center of the mark 111c is located in the area enclosed by the following four elements (1) to (4) (hereinafter also referred to as area D): (1) the virtual circumscribed circle of the fiber 111a1 to 111a4 closest to the mark 111c and the second closest fiber 111a2 among the multiple fiber cores 111a1 to 111a4 of the first multi-core fiber 111, that is, the virtual circumscribed circle centered on the center of the cladding 111b of the first multi-core fiber 111; (2) through (3) The virtual bisecting line of the angle formed by the virtual straight line passing through the center of the fiber core 111a1 closest to mark 111c and the center of the second closest fiber core 111a2 and the virtual straight line passing through the center of the fiber core 111a1 and the center of the cladding 111b; (4) The virtual bisecting line of the angle formed by the virtual straight line passing through the center of the fiber core 111a1 and the center of the fiber core 111a2 and the virtual straight line connecting the center of the fiber core 111a2 and the center of the cladding 111b;

[0125] Condition ζ2: In the end face of the second multi-core fiber 112, the center of the mark 112c is located in the area enclosed by the following four elements (1) to (4) (hereinafter also referred to as area E): (1) the virtual circumscribed circle of the fiber 112a1 closest to the mark 112c and the second closest fiber 112a2 among the multiple fiber cores 112a1 to 112a4 of the second multi-core fiber 112, that is, the virtual circumscribed circle centered on the center of the cladding 112b of the second multi-core fiber 112; (2) through (3) The virtual bisecting line of the angle formed by the virtual straight line passing through the center of the fiber core 112a1 closest to the mark 112c and the center of the second closest fiber core 112a2 and the virtual straight line passing through the center of the fiber core 112a1 and the center of the cladding 112b; (4) The virtual bisecting line of the angle formed by the virtual straight line passing through the center of the fiber core 112a1 and the center of the fiber core 112a2 and the virtual straight line connecting the center of the fiber core 112a2 and the center of the cladding 112b; (5) The outer periphery of the cladding.

[0126] In this case, in the first multi-core fiber 111, both the effects of the former and the latter can be obtained. In particular, compared with the cases of condition ε1 or condition ε2, since the mark 111c is disposed at the position separating from the fiber core 111a1 or 111a2, the deformation of the fiber core 111a1 or 111a2 can be suppressed, and therefore, in particular, the effect of the former can be further enhanced. The same applies to the second multi-core fiber 112.

[0127] Furthermore, for conditions ε1, ε2, ζ1, or ζ2, a structure can also be adopted in which at least a portion of the mark 111c is disposed in region B or region D on the end face of the first multi-core fiber 111 (hereinafter also referred to as structure 1), a structure in which the mark 111c is entirely disposed in region B or region D (hereinafter also referred to as structure 2), or a structure in which at least a portion of the mark 111c is disposed across the boundary between region B and region D (hereinafter also referred to as structure 3). Structures 1 to 3 can all obtain the effects of the former and the latter. However, especially in the case of structure 2, the structure in which the mark 111c is entirely disposed in region B, compared with the structure in the case of structure 2 in which the mark 111c is entirely disposed in region D or structure 3, can further enhance the effect of the latter because the mark 111c is disposed at a position separated from the outer periphery of the cladding 111b. Furthermore, especially in the case of structure 2, the structure in which marker 111c is entirely disposed in region D, compared to the structure in the case of structure 2 where marker 111c is entirely disposed in region B, or structure 3, because marker 111c is disposed at a position separated from core 111a1 or 111a2, can particularly enhance the effect of the former. Furthermore, especially in the case of structure 3, compared to structure 2, because marker 111c is disposed on the outer periphery of cladding 111b and at a position separated from core 111a1 or 111a2, the effects of the former and the latter can be obtained in a balanced manner. Similarly, in the end face of the second multi-core fiber 112, a structure in which at least a portion of marker 112c is disposed in region C or region E, a structure in which marker 112c is entirely disposed in region C or region E, or a structure in which at least a portion of marker 112c is disposed at the boundary between region C and region E can also be adopted. The effect obtained in this case is the same as that obtained in the first multi-core fiber 111 described above.

[0128] (Appendix Item 1) The first aspect of the present invention is not limited to the embodiments or variations described above. Various modifications can be made within the scope shown in this specification. The appropriate combination of the various technical means disclosed in the embodiments or variations is also included in the technical scope of the present invention.

[0129] For example, the number of cores in each multi-core fiber constituting the optical fiber connector is not limited to 4; it is arbitrary within the range where the desired effect can be obtained. For example, the number of cores in each multi-core fiber constituting the optical fiber connector can be 5, 6, 7, 8, or 9.

[0130] Furthermore, in this embodiment, the number of cores in the first multi-core optical fiber and the number of cores in the second multi-core optical fiber are the same. A structure is adopted in which each core of the first multi-core optical fiber is connected to any core of the second multi-core optical fiber, and each core of the second multi-core optical fiber is connected to each core of the first multi-core optical fiber. However, this is not a limitation. For example, if the number of cores in the first multi-core optical fiber is greater than the number of cores in the second multi-core optical fiber, it is sufficient that each core of the second multi-core optical fiber is connected to any core of the first multi-core optical fiber. Alternatively, if the number of cores in the second multi-core optical fiber is greater than the number of cores in the first multi-core optical fiber, it is sufficient that each core of the first multi-core optical fiber is connected to any core of the second multi-core optical fiber.

[0131] Furthermore, the number of markings on each multi-core fiber constituting the fiber optic connector is not limited to one; it is arbitrary within the range where the desired effect can be achieved. For example, the number of markings on each multi-core fiber constituting the fiber optic connector can be two, three, four, five, or six. When there are multiple markings, at least one marking of the second multi-core fiber can be connected to a portion of the first multi-core fiber other than the portion marked therein, or at least one marking of the first multi-core fiber can be connected to a portion of the second multi-core fiber other than the portion marked therein.

[0132] Furthermore, in a structure where the mark of the second multi-core optical fiber is connected to the portion other than the mark of the first multi-core optical fiber, there is also a structure where a portion of the mark of the second multi-core optical fiber is connected to the portion other than the mark of the first multi-core optical fiber (however, this excludes a structure where the mark of the second multi-core optical fiber is larger than the mark of the first multi-core optical fiber and the mark of the second multi-core optical fiber completely encompasses the mark of the first multi-core optical fiber). Similarly, in a structure where the mark of the first multi-core optical fiber is connected to the portion other than the mark of the second multi-core optical fiber, there is also a structure where a portion of the mark of the first multi-core optical fiber is connected to the portion other than the mark of the second multi-core optical fiber (however, this excludes a structure where the mark of the first multi-core optical fiber is larger than the mark of the second multi-core optical fiber and the mark of the first multi-core optical fiber completely encompasses the mark of the second multi-core optical fiber).

[0133] Furthermore, the cross-sectional shape of the markings on each multi-core optical fiber constituting the optical fiber connector is not limited to a circle, but can be arbitrary. For example, the cross-sectional shape of the markings on each multi-core optical fiber constituting the optical fiber connector can be triangular, quadrilateral, pentagonal, or hexagonal.

[0134] Furthermore, the material of the markings on each multi-core optical fiber constituting the optical fiber connector is not limited to quartz glass and can be any material. For example, the markings on each multi-core optical fiber constituting the optical fiber connector can be any type of hole. In this case, the refractive index of the markings (the refractive index of air) is lower than the refractive index of fluorine-added quartz glass. Therefore, crosstalk can be reduced more effectively in this case.

[0135] Furthermore, the method of connecting the multi-core optical fibers that constitute an optical fiber connector is not limited to fusion splicing; it can be any method. For example, the method of connecting the multi-core optical fibers that constitute an optical fiber connector can be based on connectors or adhesives.

[0136] (Second aspect) (Implementation method of the second aspect) (Fiber optic connector) The optical fiber connector according to an embodiment of the present invention will be described below with reference to the accompanying drawings. Furthermore, the optical fiber connector of this embodiment is an optical fiber connector obtained by connecting multiple multi-core optical fibers. Two methods of describing the multi-core optical fibers and their connection points will be described below, followed by a description of the multi-core optical fiber of this embodiment.

[0137] (Multi-core optical fiber) Reference Figure 9 The concept of multi-core fiber optic (MF) is explained. Figure 9 In the image, (a) is a side view of the multi-core fiber MF, (b) is a front view of one end face σ1 of the multi-core fiber MF viewed from the direction of line of sight E1, and (c) is a front view of the other end face σ2 of the multi-core fiber MF viewed from the direction of line of sight E2.

[0138] A multi-core fiber (MF) has n cores (n is a natural number greater than or equal to 2) a1 to an and a cladding b. The cladding b is a cylindrical component. The cladding b is, for example, made of quartz glass. Each core ai (i is a natural number greater than or equal to 1 and less than n) is a cylindrical region located inside the cladding b, having a higher refractive index than the cladding b, and extending in the same direction as the cladding b. Each core ai is, for example, made of quartz glass with added germanium or other rising dopants. Furthermore, the cladding b can be cylindrical, and its cross-sectional shape is arbitrary. The cross-sectional shape of the cladding b can be, for example, a quadrilateral, a hexagon, or a polygon, or a drum shape. Additionally, the cross-sectional shape of the cladding b is not particularly limited, but it is preferable that the cladding shape is symmetrical with respect to axis L1 (described later). This is because when two multi-core fibers (MF) are fused together, the cladding shapes of the two opposing multi-core fibers (MF) are approximately identical, which can suppress cladding deformation when the multi-core fibers (MF) melt.

[0139] In end faces σ1 and σ2, fiber cores a1 to an are arranged in a line-symmetric configuration with respect to axis L1, which is orthogonal to the central axis L0 of the multi-core fiber MF. Furthermore, in end faces σ1 and σ2, fiber cores a1 to an are arranged to avoid axis L1. In other words, in end faces σ1 and σ2, fiber cores a1 to an are located outside of axis L1.

[0140] Multi-core optical fibers (MF) also possess a marker c. Marker c is a region located within the cladding b, with a refractive index different from that of the cladding b, extending in the same direction as the cladding b. The cross-sectional shape of marker c is arbitrary, such as circular, triangular, or quadrilateral. Marker c can be, for example, made of quartz glass with decreasing dopants such as fluorine or boron. In this case, the refractive index of marker c is lower than that of the cladding b. Alternatively, marker c can be made of quartz glass with increasing dopants such as germanium, aluminum, phosphorus, or chlorine. In this case, the refractive index of marker c is higher than that of the cladding b. Marker c can be formed using methods such as aperture drilling or stacking.

[0141] In end faces σ1 and σ2, the center of mark c is positioned to avoid axis L1. In other words, in end faces σ1 and σ2, the center (geometric center) of mark c is located outside axis L1. Furthermore, mark c can be positioned simply so that its center avoids axis L1, or a portion of mark c can coincide with axis L1.

[0142] (Changes in cross-sectional structure) Reference Figure 10 The changes in the cross-sectional structure of multi-core optical fiber (MF) are explained.

[0143] Figure 10 (a) is the first specific example. Figure 9 The front view of the end face σ1 of the multi-core fiber MF shown in the specific example. The multi-core fiber MF of this specific example has four cores a1 to a4 arranged at the vertices of a square. For these four cores a1 to a4, (1) it can be said that they are arranged in a line-symmetric configuration with respect to the aforementioned axis L1, and (2) it can also be said that they are arranged in a line-symmetric configuration with respect to the axis L2. Here, axis L2 is an axis orthogonal to axis L1 in the end face σ1 of the multi-core fiber MF. These four cores a1 to a4 are arranged in a manner that avoids axes L1 and L2. In other words, they are arranged in positions other than axes L1 and L2. Furthermore, if the structure in which cores a1 to a4 are also allowed to be arranged on the line-symmetric axis, there are also two unshown axes of symmetry that are at 45° to axes L1 and L2.

[0144] Figure 10 (b) is a front view of the end face σ1 of the multi-core fiber MF in the second specific example. The multi-core fiber MF of this specific example has four cores a1 to a4 disposed at the vertices of an isosceles trapezoid. These four cores a1 to a4 can be described as being arranged in a linearly symmetrical manner with respect to axis L1. Here, axis L1 is an axis orthogonal to the central axis of the multi-core fiber MF. These four cores a1 to a4 are arranged to avoid axis L1. In other words, they are disposed at a position outside of axis L1.

[0145] Figure 10(c) is a front view of the end face σ1 of the multi-core fiber MF in the third specific example of the multi-core fiber MF. The multi-core fiber MF in this specific example has six cores a1 to a6 arranged at the vertices of a regular hexagon. For these six cores a1 to a6, (1) it can be said that they are arranged in a line-symmetric configuration with respect to axis L1, (2) it can also be said that they are arranged in a line-symmetric configuration with respect to axis L2, and (3) it can also be said that they are arranged in a line-symmetric configuration with respect to axis L3. Here, axis L1 is an axis orthogonal to the central axis of the multi-core fiber MF. Axis L2 is an axis on the end face σ1 of the multi-core fiber MF that forms an angle of 60° with axis L1. Axis L3 is an axis on the end face σ1 of the multi-core fiber MF that forms an angle of 60° with axes L1 and L2, respectively. These six cores a1 to a6 are arranged in a manner that avoids axes L1, L2, and L3. In other words, they are arranged in positions other than axes L1, L2, and L3. Furthermore, if the structure of cores a1 to a6 being arranged on the axis of symmetry is also allowed, then there are three unillustrated axes of symmetry that form a 30° angle with axes L1, L2, and L3.

[0146] Figure 10(d) is a front view of the end face σ1 of the multi-core fiber MF in the fourth specific example of the multi-core fiber MF. The multi-core fiber MF in this specific example has six cores a1 to a6 arranged at the vertices of a regular hexagon, and one core a7 arranged at the center of the regular hexagon. For these seven cores a1 to a7, (1) it can be said that they are arranged in a line-symmetric configuration with respect to axis L1, (2) it can also be said that they are arranged in a line-symmetric configuration with respect to axis L2, and (3) it can also be said that they are arranged in a line-symmetric configuration with respect to axis L3. Here, axis L1 is an axis orthogonal to the central axis of the multi-core fiber MF. Axis L2 is an axis on the end face σ1 of the multi-core fiber MF that forms an angle of 60° with axis L1. Axis L3 is an axis on the end face σ1 of the multi-core fiber MF that forms an angle of 60° with axes L1 and L2, respectively. The six cores a1 to a6 of these seven cores a1 to a7 arranged at the vertices of the regular hexagon are arranged in a manner that avoids axes L1, L2, and L3. In other words, they are positioned outside of axes L1, L2, and L3. As explained later, these fiber cores a1 to a6 are suitable for either inputting or outputting optical signals. Additionally, a fiber core a7, positioned at the center of the regular hexagon, is located on axes L1, L2, and L3. This fiber core a7 can be used for either inputting or outputting optical signals, or it can function as a virtual fiber core without inputting or outputting optical signals. Of course, in the fiber connector 201 described later, if fiber core a7 is used for optical signal input on one end face 211, it can be used for optical signal output on the other end face 212; conversely, if fiber core a7 is used for optical signal output on one end face 211, it can be used for optical signal input on the other end face 212. Furthermore, if a structure also allows fiber cores a1 to a6 to be positioned on axes of symmetry, then there are three axes of symmetry (not shown) forming a 30° angle with axes L1, L2, and L3.

[0147] Figure 10(e) is a front view of the end face σ1 of the multi-core fiber MF in the fifth specific example of the multi-core fiber MF. The multi-core fiber MF in this specific example has eight cores a1 to a8 arranged at the vertices of a regular octagon. For these eight cores a1 to a8, (1) it can be said that they are arranged in a line symmetric configuration with respect to axis L1, (2) it can also be said that they are arranged in a line symmetric configuration with respect to axis L2, (3) it can also be said that they are arranged in a line symmetric configuration with respect to axis L3, and (4) it can also be said that they are arranged in a line symmetric configuration with respect to axis L4. Here, axis L1 is an axis orthogonal to the central axis of the multi-core fiber MF. Axis L2 is an axis on the end face σ1 of the multi-core fiber MF that forms an angle of 45° with axis L1. Axis L3 is an axis on the end face σ1 of the multi-core fiber MF that forms an angle of 45° with axis L2. Axis L4 is an axis on the end face σ1 of the multi-core fiber MF that forms an angle of 45° with axes L3 and L1, respectively. These eight fiber cores a1 to a8 are arranged to avoid axes L1, L2, L3, and L4. In other words, they are arranged in positions other than axes L1, L2, L3, and L4. Furthermore, if the structure also allows the fiber cores a1 to a8 to be arranged on the axis of symmetry, then there are four other axes of symmetry (not shown) that form a 22.5° angle with axes L1, L2, L3, and L4.

[0148] Figure 10 (f) is a front view of the end face σ1 of the multi-core fiber MF in the sixth specific example of the multi-core fiber MF. The multi-core fiber MF of this specific example has eight cores a1 to a8 arranged in a row and column configuration of two rows and four columns. For these eight cores a1 to a8, (1) it can be said that they are arranged in a line-symmetric configuration with respect to axis L1, and (2) it can also be said that they are arranged in a line-symmetric configuration with respect to axis L2. Here, axis L1 is an axis orthogonal to the central axis of the multi-core fiber MF and parallel to the column direction of cores a1 to a8, and axis L2 is an axis orthogonal to the central axis of the multi-core fiber MF and parallel to the row direction of cores a1 to a8. These eight cores a1 to a8 are arranged in a manner that avoids axes L1 and L2. In other words, they are arranged in positions other than axes L1 and L2.

[0149] (Connection points of multi-core optical fibers) Reference Figures 11-13 The connection point of the two multi-core optical fibers MF is described below. Hereinafter, one of the two connected multi-core optical fibers MF will be referred to as multi-core fiber MF1, and the other as multi-core fiber MF2. Multi-core optical fibers MF1 and MF2 are multi-core optical fibers with identical cross-sectional structures. The connection between multi-core optical fibers MF1 and MF2 can be a fusion splice, a connection using a connector, or a connection using adhesive.

[0150] For the connection points of multi-core optical fibers MF1 and MF2, there are normal connection points and reverse connection points.

[0151] Figure 11The diagrams show the connection points of typical connections. (a) is a side view of multi-core optical fibers MF1 and MF2, (b) is a front view of the end face σ2 of multi-core optical fiber MF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ1 of multi-core optical fiber MF2 viewed from the direction of line of sight E1. The typical connection point is either the connection point connecting the end face σ2 of multi-core optical fiber MF1 to the end face σ1 of multi-core optical fiber MF2, or the connection point connecting the end face σ1 of multi-core optical fiber MF1 to the end face σ2 of multi-core optical fiber MF2. Figure 11 (It is the former). The connection parts of the connection usually meet the following conditions.

[0152] Condition 1: The cores a1 to an of the end face σ1 of the multi-core fiber MF2 coincide with the cores a1 to an of the end face σ2 of the multi-core fiber MF1. Specifically, (1) the core a1 of the end face σ1 of the multi-core fiber MF2 coincides with the core a1 of the end face σ2 of the multi-core fiber MF1, (2) the core a2 of the end face σ1 of the multi-core fiber MF2 coincides with the core a2 of the end face σ2 of the multi-core fiber MF1, (3) the core a3 of the end face σ1 of the multi-core fiber MF2 coincides with the core a3 of the end face σ2 of the multi-core fiber MF1, (4) the core a4 of the end face σ1 of the multi-core fiber MF2 coincides with the core a4 of the end face σ2 of the multi-core fiber MF1.

[0153] Condition 2a: The mark c on the end face σ1 of the multi-core fiber MF2 coincides with the mark c on the end face σ2 of the multi-core fiber MF1.

[0154] In simple terms, a typical connection is a connection method where the fiber cores a1 to an are optically coupled and marked with a c connection.

[0155] Figure 12 The diagram shows the connection points of the flipped connection. (a) is a side view of multi-core optical fibers MF1 and MF2, (b) is a front view of the end face σ2 of multi-core optical fiber MF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ2 of multi-core optical fiber MF2 viewed from the direction of line of sight E1. The connection point of the flipped connection is the connection point that connects the end face σ2 of multi-core optical fiber MF1 to the end face σ2 of multi-core optical fiber MF2, or the connection point that connects the end face σ1 of multi-core optical fiber MF1 to the end face σ1 of multi-core optical fiber MF2. Figure 12 (It is the former). The connection parts of the flip connection meet the following conditions.

[0156] Condition 1: The cores a1 to an of the end face σ2 of the multi-core fiber MF2 coincide with the cores a1 to an of the end face σ2 of the multi-core fiber MF1. Specifically, (1) the core a1 of the end face σ2 of the multi-core fiber MF2 coincides with the core a4 of the end face σ2 of the multi-core fiber MF1, (2) the core a2 of the end face σ2 of the multi-core fiber MF2 coincides with the core a3 of the end face σ2 of the multi-core fiber MF1, (3) the core a3 of the end face σ2 of the multi-core fiber MF2 coincides with the core a2 of the end face σ2 of the multi-core fiber MF1, and (4) the core a4 of the end face σ2 of the multi-core fiber MF2 coincides with the core a1 of the end face σ2 of the multi-core fiber MF1.

[0157] Condition 2b: The mark c on the end face σ2 of the multi-core fiber MF2 coincides with the position x on the end face σ2 of the multi-core fiber MF1 that is linearly symmetrical with respect to axis L1 to the mark c on the multi-core fiber MF1.

[0158] Simply put, the flip connection is a connection method where the fiber cores a1 to an are optically coupled and the marker c is not connected.

[0159] Furthermore, the flip connection is defined according to the axis of linear symmetry of the fiber cores a1 to an. For example, in a structure with... Figure 10 In the multi-core optical fibers MF1 and MF2 with the cross-sectional structure shown in (a), the cores a1 to a4 are linearly symmetrical with respect to axis L1 and with respect to axis L2. Therefore, these multi-core optical fibers MF1 and MF2, in addition to being linearly symmetrical with respect to axis L1, also exhibit linear symmetry with respect to axis L2. Figure 12 In addition to the flip connection shown on shaft L1, it can also be relative to... Figure 13 The axis L2 shown is flipped and connected.

[0160] Figure 13 The diagram shows the connection points of the flipped connection. (a) is a side view of multi-core optical fibers MF1 and MF2, (b) is a front view of the end face σ2 of multi-core optical fiber MF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ2 of multi-core optical fiber MF2 viewed from the direction of line of sight E1. The connection point of the flipped connection is the connection point that connects the end face σ2 of multi-core optical fiber MF1 to the end face σ2 of multi-core optical fiber MF2, or the connection point that connects the end face σ1 of multi-core optical fiber MF1 to the end face σ1 of multi-core optical fiber MF2. Figure 13 (It is the former). The connection parts of the flip connection meet the following conditions.

[0161] Condition 1: The cores a1 to an of the end face σ1 of the multi-core fiber MF2 coincide with the cores a1 to an of the end face σ2 of the multi-core fiber MF1. Specifically, (1) the core a1 of the end face σ2 of the multi-core fiber MF2 coincides with the core a2 of the end face σ2 of the multi-core fiber MF1, (2) the core a2 of the end face σ2 of the multi-core fiber MF2 coincides with the core a1 of the end face σ2 of the multi-core fiber MF1, (3) the core a3 of the end face σ2 of the multi-core fiber MF2 coincides with the core a4 of the end face σ2 of the multi-core fiber MF1, and (4) the core a4 of the end face σ2 of the multi-core fiber MF2 coincides with the core a3 of the end face σ2 of the multi-core fiber MF1.

[0162] Condition 2b: The mark c on the end face σ2 of the multi-core fiber MF2 coincides with the position x on the end face σ2 of the multi-core fiber MF1 that is linearly symmetrical with respect to the axis L2 to the mark c of the multi-core fiber MF1.

[0163] (Fiber optic connector) Reference Figure 14 The optical fiber connector 201 of this embodiment will be described.

[0164] Figure 14 (a) is a side view of the optical fiber connector 201 of this embodiment. The optical fiber connector 201 is an optical fiber connector obtained by connecting m (m is a natural number of 2 or more) multi-core optical fibers MF. Hereinafter, the multi-core optical fibers MF constituting the optical fiber connector 201 will also be referred to as multi-core optical fibers MF1, MF2, ..., MFm. Multi-core optical fibers MF1 to MFm are multi-core optical fibers with the same cross-sectional structure. The connection of multi-core optical fibers MF1 to MFm can be a fusion splice, a connection using a connector, or a connection using adhesive.

[0165] The fiber optic connector 201 is composed of m multi-core optical fibers MF1 to MFm. Therefore, the fiber optic connector 201 includes m-1 connection points CP1 to CPm-1. Connection point CPi (i is a natural number greater than or equal to 1 and less than or equal to m-1) is a connection point created by connecting multi-core optical fibers MFi and MFi+1. The fiber optic connector 201 is characterized in that an odd number of these m-1 connection points CP1 to CPm-1 are connection points with inverted connections relative to a specific axis. In this embodiment, the other connection points are assumed to be normally connected connection points. It should be noted that an even number of connection points with inverted connections relative to another specific axis may also be included among the other connection points.

[0166] Based on this feature, the end faces 211 and 212 of the optical fiber connector 201 can be either end faces σ1 or end faces σ2 of the multi-core optical fiber MF.

[0167] Figure 14 Figures (b) and (c) are diagrams showing the case where the two end faces 211 and 212 of the fiber connector 201 become the end face σ1 of the multi-core fiber MF. Figure 14 (b) is a front view of one end face 211 of the fiber optic connector 201 as viewed from the line of sight E1. Figure 14 (c) is a front view of the other end face 212 of the fiber optic connector 201 as viewed from the E2 line of sight.

[0168] In this case, (1) the fiber core a1 of the multi-core fiber (e.g., multi-core fiber MF1) located in the front stage is optically coupled to the fiber core a4 of the multi-core fiber (e.g., multi-core fiber MF2) located in the rear stage; (2) the fiber core a2 of the multi-core fiber (e.g., multi-core fiber MF1) located in the front stage is optically coupled to the fiber core a3 of the multi-core fiber (e.g., multi-core fiber MF2) located in the rear stage; (3) the fiber core a3 of the multi-core fiber (e.g., multi-core fiber MF1) located in the front stage is optically coupled to the fiber core a2 of the multi-core fiber (e.g., multi-core fiber MF2) located in the rear stage; and (4) the fiber core a4 of the multi-core fiber (e.g., multi-core fiber MF1) located in the front stage is optically coupled to the fiber core a1 of the multi-core fiber (e.g., multi-core fiber MF2) located in the rear stage.

[0169] Figure 14 Figures (d) and (e) are diagrams showing the case where the two end faces 211 and 212 of the fiber connector 201 become the end face σ2 of the multi-core fiber MF. Figure 14 (d) is a front view of one end face 211 of the fiber optic connector 201 as viewed from the line of sight E1. Figure 14 (e) is a front view of the other end face 212 of the fiber optic connector 201 as viewed from the direction of line of sight E2.

[0170] In this case, (1) the core a1 of multi-core fiber MF1 is optically coupled to the core a4 of multi-core fiber MFm, (2) the core a2 of multi-core fiber MF1 is optically coupled to the core a3 of multi-core fiber MFm, (3) the core a3 of multi-core fiber MF1 is optically coupled to the core a2 of multi-core fiber MFm, and (4) the core a4 of multi-core fiber MF1 is optically coupled to the core a1 of multi-core fiber MFm.

[0171] (Effect of the fiber optic connector) Reference Figure 15 The effects achieved by the fiber optic connector 201 are explained. Figure 15 (a) and (b) with Figure 14 Similarly, (b) and (c) are diagrams concerning the case where the two end faces 211 and 212 of the fiber connector 201 become the end face σ1 of the multi-core fiber MF. Figure 15 (a) is a front view of one end face 211 of the fiber optic connector 201 as viewed from the line of sight E1. Figure 15 (b) is a front view of the other end face 212 of the fiber optic connector 201 as viewed from the E2 line of sight.

[0172] Consider identifying fiber cores a1 to a4 based on the distance from mark c on both end faces 211 and 212 of the fiber connector 201. Here, as... Figure 15 As shown, the identifier "1" is assigned to the fiber core a1 closest to mark c, the identifier "2" is assigned to the fiber core a4 second closest to mark c, the identifier "3" is assigned to the fiber core a2 third closest to mark c, and the identifier "4" is assigned to the fiber core a3 farthest from mark c. That is, for fiber cores located outside the aforementioned linearly symmetrical axis, when the fiber cores are identified on the two end faces 211 and 212 of the fiber connector 201 based on the distance from the identifier, the same identifier is assigned to the fiber cores that are linearly symmetrical to each other.

[0173] Therefore, fiber core a1, designated as "1" in one end face 211 of fiber connector 201, is optically coupled to fiber core a4, designated as "2" in the other end face 212 of fiber connector 201. Additionally, fiber core a4, designated as "2" in one end face 211 of fiber connector 201, is optically coupled to fiber core a1, designated as "1" in the other end face 212 of fiber connector 201. Furthermore, fiber core a2, designated as "3" in one end face 211 of fiber connector 201, is optically coupled to fiber core a3, designated as "4" in the other end face 212 of fiber connector 201. Additionally, fiber core a3, designated as "4" in one end face 211 of fiber connector 201, is optically coupled to fiber core a2, designated as "3" in the other end face 212 of fiber connector 201.

[0174] Thus, in the fiber optic connector 201, instead of optically coupling the same identifier to each other on the two end faces 211 and 212, the fiber cores with identifiers in an interchangeable relationship (1←→2, 3←→4) are optically coupled to each other. Therefore, when fiber cores a1 to a4 are used for two complementary purposes (e.g., optical input and optical output), when fiber cores with the same identifier are used for the same purpose, fiber cores used for complementary purposes can be optically coupled to each other. Therefore, the two ends of interconnected fiber cores are not used for input and the two ends of interconnected fiber cores are not used for output. Therefore, according to the above structure, a fiber optic connector 201 with superior processing performance can be achieved compared to the past. Furthermore, this effect applies to fiber cores a1 to an that are arranged away from the axis of symmetry L1 (in the case where all fiber cores a1 to an are arranged away from the axis of symmetry, this applies to all fiber cores). Furthermore, when all fiber cores a1 to an are arranged away from the axis of symmetry, a fiber connector 201 with superior processing performance can be achieved compared to the case where all fiber cores a1 to an are arranged away from the axis of symmetry.

[0175] For example, in the two end faces 211 and 212, the fiber core assigned the identifier "1" is set to be used for the input of the first optical signal, the fiber core assigned the identifier "2" is set to be used for the output of the first optical signal, the fiber core assigned the identifier "3" is set to be used for the output of the second optical signal, and the fiber core assigned the identifier "4" is set to be used for the input of the second optical signal.

[0176] Therefore, in the fiber optic connector 201, fiber core a1, designated as the input of the first optical signal and marked with identifier "1" in one end face 211, is optically coupled to fiber core a4, designated as the output of the first optical signal and marked with identifier "2" in the other end face 212, thus enabling communication. Similarly, fiber core a4, designated as the output of the first optical signal and marked with identifier "2" in one end face 211, is optically coupled to fiber core a1, designated as the input of the first optical signal and marked with identifier "1" in the other end face 212, thus enabling communication. Likewise, fiber core a2, designated as the output of the second optical signal and marked with identifier "3" in one end face 211, is optically coupled to fiber core a3, designated as the input of the second optical signal and marked with identifier "4" in the other end face 212, thus enabling communication. Similarly, optical coupling occurs between fiber core a3, designated as the input of the second optical signal and marked with the identifier "4" in one end face 211, and fiber core a2, designated as the output of the second optical signal and marked with the identifier "3" in the other end face 212, thus enabling communication. Furthermore, regarding fiber cores a1 to a4, it is preferable that in both end faces 211 and 212, the fiber cores for inputting the first optical signal and the fiber cores for inputting the second optical signal are arranged diagonally, and the fiber cores for outputting the first optical signal and the fiber cores for outputting the second optical signal are also arranged diagonally. This allows the spacing between the fiber cores propagating the first and second optical signals to be increased from one end face to the other. Therefore, when the first or second optical signal propagates from the end face 211 side to the end face 212 side or from the end face 212 side to the end face 211 side, it is possible to suppress the propagation of the first or second optical signal propagating in a specific fiber core to a fiber core that can propagate the same type of optical signal as the first or second optical signal but is different from that specific fiber core. The above methods can reduce crosstalk between the first and second optical signals.

[0177] Furthermore, regarding the case where the two end faces 211 and 212 of the fiber optic connector 201 become the end faces σ1 of the multi-core fiber MF, the effect achieved by the fiber optic connector 201 is explained. The same effect can be obtained when the two end faces 211 and 212 of the fiber optic connector 201 become the end faces σ2 of the multi-core fiber MF. Additionally, regarding the case where there is an odd number of connection points for the flip connection to axis L1, the effect achieved by the fiber optic connector 201 is explained. The same effect can be obtained when there is an odd number of connection points for the flip connection to axis L2.

[0178] Furthermore, when fan-in / fan-out devices or transceivers are connected to both ends of the fiber optic connector 201, the following effect is achieved. Specifically, when fan-in / fan-out devices or transceivers are connected to both ends of an existing fiber optic connector where all connection points are normally connected, it is necessary to prepare fan-in / fan-out devices or transceivers with different port configurations, or fan-in / fan-out devices or transceivers capable of converting the use of each port. Therefore, in the former case, a technical problem arises with an increased number of components, and in the latter case, a technical problem arises with increased structural complexity. In contrast, when fan-in / fan-out devices are connected to both ends of the fiber optic connector 201 where an odd number of connection points are reverse-connected, as explained later, even if the port configuration is a universal fan-in / fan-out device, since the transmitting port of one fan-in / fan-out device is connected to the receiving port of another, it is not necessary to prepare fan-in / fan-out devices with different port configurations, nor is it necessary to prepare fan-in / fan-out devices capable of converting the use of each port. Therefore, by using the fiber optic connector 201, a communication system can be implemented with fewer components or a simpler structure than before. The same effect can be achieved when transceivers are connected to both ends of the fiber optic connector 201. The port configuration structure described above will be explained in detail later.

[0179] (Modified example of fiber optic connector) Reference Figure 16 A first modification of the optical fiber connector 201 (hereinafter referred to as optical fiber connector 201A) will be described. Figure 16 In the image, (a) is a side view of the fiber connector 201A, (b) is a front view of the end face (σ1) of the multi-core fiber MF2 side of the multi-core fiber MF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face (σ1) of the multi-core fiber MF1 side of the multi-core fiber MF2 viewed from the direction of line of sight E1.

[0180] The difference between fiber connector 201A and fiber connector 201 lies in the fact that each multi-core fiber MF has a metal ring d and a frame e at both ends. The metal ring d is a cylindrical structure covering the outer side of the cladding b, and the frame e is a cylindrical structure covering the outer side of the metal ring d. A key f is provided on the frame e. The key f is a convex structure located on the outer side of the frame e. The metal ring d and the frame e are an example of an envelope covering multi-core fibers MF1 and MFm.

[0181] like Figure 14 As shown in (b) and (c), key f is disposed on the line-symmetric axis L1 of fiber cores a1 to an. Therefore, by connecting multi-core fibers MF1 and MF2 with their respective key f positions aligned, a normal connection or a reverse connection can be easily achieved (in...). Figure 16(In the case of a flip connection). Furthermore, the connection between multi-core fiber MF1 and multi-core fiber MF2 can be performed, for example, as follows: First, align the position of key f on frame e of multi-core fiber MF1 with the position of key f on frame e of multi-core fiber MF2. Next, after fitting and aligning each key f onto the connection keyway of the adapter (not shown), connect frame e of multi-core fiber MF1 to frame e of multi-core fiber MF2.

[0182] Furthermore, regarding all connection points CPi (i being a natural number between 1 and m-1), a structure in which a key f is provided near the end face of the multi-core fiber MFi+1 side of the multi-core fiber MFi and near the end face of the multi-core fiber MFi+1 side of the multi-core fiber MFi, is described, but is not limited to this. Regarding at least one connection point CPi, as long as a key f is provided near the end face of the multi-core fiber MFi+1 side of the multi-core fiber MFi and near the end face of the multi-core fiber MFi+1 side of the multi-core fiber MFi, normal or reverse connections of these multi-core fibers MFi and MF can be easily performed. Additionally, a key f can be provided near the end face 211 of the multi-core fiber MF1 and / or near the end face 212 of the multi-core fiber m.

[0183] (Optical communication system) Reference Figure 17 An optical communication system 210 including an optical fiber connector 201 will be described.

[0184] Figure 17 (a) is a side view of the optical communication system 210. The optical communication system 210 includes: an optical fiber connector 201, a first transceiver 202 connected to one end face 211 of the optical fiber connector 201, and a second transceiver 203 connected to the other end face of the optical fiber connector 201. In addition, the first transceiver 202 includes an optical input / output element 202a, and the second transceiver 203 includes an optical input / output element 203a.

[0185] Figure 17 (b) is a front view of the end face 211 of the fiber optic connector 201 as viewed from the direction of line of sight E1. Figure 17 (c) is a front view of the end face 212 of the fiber optic connector 201 as viewed from the E2 line of sight. Figure 17 (d) is a front view of the optical input / output element 202a of the first transceiver 202 as viewed from the line of sight E2. Figure 17(e) is a front view of the optical input / output element 203a of the second transceiver 203 as viewed from the line of sight E1. The optical input / output elements 202a and 203a each have a transmit port Tx1 for transmitting a first optical signal, a receive port Rx1 for receiving the first optical signal, a transmit port Tx2 for transmitting a second optical signal, and a receive port Rx2 for receiving the second optical signal. Transmit port Tx1 and receive port Rx1 form a first pair of ports, and transmit port Tx2 and receive port Rx2 form a second pair of ports. Furthermore, the port configuration structure having transmit port Tx1, receive port Rx1, transmit port Tx2, and receive port Rx2 is a common structure in the end faces of the optical input / output elements 202a and 203a.

[0186] By using the fiber optic connector 201, an optical communication system 210 can be made so that the port configuration structure in the optical input / output element 202a of the first transceiver 202 is universalized with the port configuration structure in the optical input / output element 203a of the second transceiver 203. Therefore, the optical input / output elements 202a of the first transceiver 202 and 203a of the second transceiver 203 can be made to be identical components. Thus, an optical communication system 210 with fewer components or a simpler structure can be realized. Here, "universal port configuration structure" means, for example, that the labels or tags assigned to each optical input / output element are identical.

[0187] In fact, (1) fiber core a1 of end face 211 is optically coupled to fiber core a4 of end face 212, (2) fiber core a4 of end face 211 is optically coupled to fiber core a1 of end face 212, (3) fiber core a2 of end face 211 is optically coupled to fiber core a3 of end face 212, and (4) fiber core a3 of end face 211 is optically coupled to fiber core a2 of end face 212. Therefore, in optical input / output elements 202a and 203a, even if the configuration of transmitting port Tx1, receiving port Rx1, transmitting port Tx2, and receiving port Rx2 is generalized, communication can still be established.

[0188] The reason is that (1) the fiber core a1 connected to the transmitting port Tx1 of the optical input / output element 202a on one end face 211 of the optical fiber connector 201 is optically coupled to the fiber core a4 connected to the receiving port Rx1 of the optical input / output element 203a on the other end face 212 of the optical fiber connector 201, and (2) the fiber core a4 connected to the receiving port Rx1 of the optical input / output element 202a on one end face 211 of the optical fiber connector 201 is optically coupled to the fiber core a1 connected to the transmitting port Tx1 of the optical input / output element 203a on the other end face 212 of the optical fiber connector 201. Optical coupling, (3) optical coupling is performed between the fiber core a2 connected to the receiving port Rx2 of the optical input / output element 202a on one end face 211 of the fiber connector 201 and the fiber core a3 connected to the transmitting port Tx2 of the optical input / output element 203a on the other end face 212 of the fiber connector 201, and (4) optical coupling is performed between the fiber core a3 connected to the transmitting port Tx2 of the optical input / output element 202a on one end face 211 of the fiber connector 201 and the fiber core a2 connected to the receiving port Rx2 of the optical input / output element 203a on the other end face 212 of the fiber connector 201. This is the effect achieved by utilizing the above-mentioned features of the fiber connector 201.

[0189] (Optical equipment) Reference Figure 18 The optical device 220, which includes the optical fiber connector 201, will be described.

[0190] Figure 18 (a) is a block diagram of optical device 220. Optical device 220 includes: an optical fiber connector 201, a first fan-in / fan-out device 204 connected to one end face 211 of the optical fiber connector 201, and a second fan-in / fan-out device 205 connected to the other end face 212 of the optical fiber connector 201. In addition, the first fan-in / fan-out device 204 and the second fan-in / fan-out device 205 each include: optical path conversion units 204a and 205a, a single-core optical fiber connected to the optical path conversion units 204a and 205a, and four connectors connected to the single-core optical fiber.

[0191] Figure 18 (b) is a front view of the end face 211 of the fiber optic connector 201 as viewed from the direction of line of sight E1. Figure 18 (c) is a front view of the end face 212 of the fiber optic connector 201 as viewed from the E2 line of sight. Figure 18 (d) is a front view of the end face of the optical path conversion section 204a of the first fan-in / fan-out device 204 as viewed from the line of sight E2. Figure 18(e) is a front view of the optical path conversion section 205a of the second fan-in / fan-out device 205, viewed from the line of sight E1. Optical path conversion sections 204a and 205a each include: a transmitting port Tx1 connected to a first transmitting connector for transmitting a first optical signal; a receiving port Rx1 connected to a first receiving connector for receiving the first optical signal; a transmitting port Tx2 connected to a second transmitting connector for transmitting a second optical signal; and a receiving port Rx2 connected to a second receiving connector for receiving the second optical signal. Here, the port configuration structure including the transmitting port Tx1, receiving port Rx1, transmitting port Tx2, and receiving port Rx2 is a common structure in the end faces of the optical path conversion sections 204a and 205a.

[0192] By using the fiber optic connector 201, an optical device 220 can achieve a port configuration structure that is universal between the optical path conversion section 204a of the first fan-in / fan-out device 204 and the optical path conversion section 205a of the second fan-in / fan-out device 205. The reason for this is the same as in the optical communication system 210, where the port configuration structure of the optical input / output element 202a of the first transceiver 202 is universal between the port configuration structure of the optical input / output element 203a of the second transceiver 203. Here, "universal" port configuration means, for example, that the labels or tags assigned to each connector are the same, and in the case of ribbon fiber or multi-core connectors, the fiber arrangement order is the same. Therefore, an optical device 220 with fewer components or a simpler structure can be achieved.

[0193] Furthermore, while fan-in / fan-out devices 204 and 205 are fan-in / fan-out devices without pigtails and having a multi-core fiber structure, they are not limited to this. For example, fan-in / fan-out devices 204 and 205 could be fan-in / fan-out devices with a multi-core fiber structure connected to pigtails. In this case, the same effect as described above can be obtained. Additionally, using fan-in / fan-out devices 204 and 205 connected to pigtails capable of identifying the fiber core arrangement structure enables the port configuration structure to be universally applicable. This allows for the realization of an optical device 220 with fewer components or a simpler structure. Furthermore, the port configuration structure of fan-in / fan-out devices 204 and 205 can be easily identified simply by recognizing the fiber core arrangement structure. Examples of pigtails capable of identifying the fiber core arrangement structure include optical fibers with markings on their end faces, optical fibers with keys on the sheath covering the pigtail, and optical fibers with identification information around the pigtail. In addition, there are no particular limitations on the fan-in / fan-out devices 204 and 205, and examples include fused strand type, spatial bonding type, fiber bundle type, planar waveguide type, etc.

[0194] (Appendix Item 2) The second aspect of the present invention is not limited to the embodiments or variations described above. Various modifications can be made within the scope shown in this specification. The methods obtained by appropriately combining the various technical means disclosed in the embodiments or variations described above are also included in the technical scope of the present invention.

[0195] (Summary 1) Regarding the optical fiber connector of Embodiment 1 of the first aspect of the present invention, it is characterized by comprising at least: a first multi-core optical fiber having a plurality of cores and at least one first mark disposed inside the cladding; and a second multi-core optical fiber having a plurality of cores and at least one second mark disposed inside the cladding, and one end face being connected to one end face of the first multi-core optical fiber, wherein each core of the second multi-core optical fiber is connected to any core of the first multi-core optical fiber, or each core of the first multi-core optical fiber is connected to any core of the second multi-core optical fiber, at least any one of the second marks of the second multi-core optical fiber is connected to a portion of the first multi-core optical fiber other than the first mark, or at least any one of the first marks of the first multi-core optical fiber is connected to a portion of the second multi-core optical fiber other than the second mark.

[0196] Regarding the optical fiber connector of the first aspect 2 of the present invention, in addition to the structure of the first aspect 1, the following structure is also adopted: the number of cores in the first multi-core optical fiber and the second multi-core optical fiber is 2 or more, and the core in the second multi-core optical fiber that is closest to the second mark is connected to the core in the first multi-core optical fiber that is other than the core in the first multi-core optical fiber that is closest to the first mark.

[0197] Regarding the optical fiber connector of embodiment 3 of the first aspect of the present invention, in addition to the structure of embodiment 1, the following structure is also adopted: the number of cores in the first multi-core optical fiber and the second multi-core optical fiber is 3 or more, and the pair of cores in the second multi-core optical fiber consisting of the core closest to the second mark and the second closest core, or the pair of cores closest to the second mark, is connected to: the pair of cores in the first multi-core optical fiber except for the pair of cores closest to the first mark and the second closest core, or the pair of cores except for the pair of cores closest to the first mark.

[0198] Regarding the optical fiber connector of embodiment 4 of the first aspect of the present invention, in addition to the structure of embodiment 3, the following structure is also adopted: the refractive index of the first mark is lower than the refractive index of the cladding of the first multi-core optical fiber, and the refractive index of the second mark is lower than the refractive index of the cladding of the second multi-core optical fiber.

[0199] Regarding the optical fiber connector of embodiment 5 of the first aspect of the present invention, in addition to the structure of any one of embodiments 1 to 4, the following structure is also adopted: it further comprises a third multi-core optical fiber, which has a plurality of cores and a third mark arranged inside the cladding, and one end face is connected to the other end face of the second multi-core optical fiber. The number of cores in the first multi-core optical fiber and the third multi-core optical fiber is n (n is a natural number greater than or equal to 2). When the ordinal number of the cores in each multi-core optical fiber is determined according to the arrangement order of the cores and with the core closest to the mark as the first and the second core closest to the mark as the second, the i-th core (i is a natural number greater than or equal to 1 and less than or equal to n) of the third multi-core optical fiber is connected to the core of the second multi-core optical fiber that is connected to the i-th core of the first multi-core optical fiber.

[0200] Regarding the optical fiber connector of the first aspect of the present invention, in addition to any of the structures of embodiments 1 to 4, the following structure is also adopted: it further comprises a third multi-core optical fiber, which has a plurality of cores and a third mark arranged inside the cladding, and one end face is connected to the other end face of the second multi-core optical fiber, wherein the core closest to the third mark in the third multi-core optical fiber is connected to a core satisfying the following (1) and (2): (1) the core is a core of the second multi-core optical fiber other than the core closest to the second mark, and (2) the core is a core of the second multi-core optical fiber other than the core connected to the core closest to the first mark in the first multi-core optical fiber.

[0201] Regarding the optical fiber connector of embodiment 7 of the first aspect of the present invention, in addition to the structure of any one of embodiments 1 to 6, the following structure is also adopted: in the first multi-core optical fiber, the first mark is configured such that the distance from the first mark to each fiber core is completely different; and in the second multi-core optical fiber, the second mark is configured such that the distance from the second mark to each fiber core is completely different.

[0202] Regarding the optical fiber connector of embodiment 8 of the first aspect of the present invention, in addition to the structure of any one of embodiments 1 to 7, it also adopts the following structure: it further comprises a first frame disposed at the end of the first multi-core optical fiber on the second multi-core optical fiber side, and a second frame disposed at the end of the second multi-core optical fiber on the first multi-core optical fiber side, wherein the position of the connecting key disposed on the surface of the first frame is aligned with the position of the fiber core closest to the first mark, and the position of the connecting key disposed on the surface of the second frame is aligned with the position of the fiber core closest to the second mark.

[0203] The method for manufacturing an optical fiber connector according to the first aspect 9 of the present invention is characterized in that the optical fiber connector comprises: a first multi-core optical fiber having a plurality of fiber cores and at least one first mark disposed inside the cladding, and a second multi-core optical fiber having a plurality of fiber cores and at least one second mark disposed inside the cladding; the method comprising the steps of: connecting each fiber core of the second multi-core optical fiber to any fiber core of the first multi-core optical fiber, or connecting each fiber core of the first multi-core optical fiber to any fiber core of the second multi-core optical fiber, and connecting one end face of the second multi-core optical fiber to one end face of the first multi-core optical fiber in such a manner that at least one of the second marks of the second multi-core optical fiber is connected to a portion of the first multi-core optical fiber other than the first mark, or connecting at least one of the first marks of the first multi-core optical fiber to a portion of the second multi-core optical fiber other than the second mark.

[0204] (Summary 2) Regarding the optical fiber connector of the second aspect 1 of the present invention, it is characterized in that it is connected to a plurality of multi-core optical fibers with the same core configuration, each multi-core optical fiber having an end face containing a cladding, a plurality of cores arranged in a line symmetrical manner inside the cladding, and a mark, the center of the mark being disposed at a position other than the axis of symmetry of the plurality of cores, and when one end face of an adjacent multi-core optical fiber is designated as a first end face and the other end face is designated as a second end face, the number of connection points satisfying the following conditions is odd: (1) the plurality of cores of the first end face coincide with the plurality of cores of the second end face; and (2) the mark of the first end face coincides with a position in the second end face that is line symmetrical with respect to the axis of symmetry with respect to the mark of the second end face.

[0205] Regarding the optical fiber connector of the second aspect of the present invention, in addition to the structure of the first aspect, the following structure is also adopted: the plurality of fiber cores are all arranged at positions other than the axis of symmetry.

[0206] Regarding the optical fiber connector of the second aspect of the present invention, in addition to the structure of the second aspect or the third aspect, the following structure is also adopted: the multi-core optical fibers that are adjacent to each other are used as the first multi-core optical fiber and the second multi-core optical fiber, a key is provided on the outside of the sleeve covering the side of the first multi-core optical fiber, and a key is provided on the outside of the sleeve covering the side of the second multi-core optical fiber.

[0207] Regarding the optical fiber connector of embodiment 4 of the second aspect of the present invention, in addition to the structure of any one of embodiments 1 to 3, the following structure is also adopted: the purpose of the plurality of fiber cores is determined in such a way that, in the two end faces of the optical fiber connector, the fiber cores for inputting optical signals are arranged diagonally opposite each other, and the fiber cores for outputting optical signals are arranged diagonally opposite each other.

[0208] Regarding the optical communication system of embodiment 5 of the second aspect of the present invention, the following structure is adopted: it includes an optical fiber connector of any one of embodiments 1 to 4, a first transceiver disposed at one end of the optical fiber connector, and a second transceiver disposed at the other end of the optical fiber connector, wherein the port configuration structure of the first transceiver is the same as the port configuration structure of the second transceiver.

[0209] Regarding the optical device of embodiment 6 of the second aspect of the present invention, it adopts the following structure: it includes an optical fiber connector of any one of embodiments 1 to 4, a first fan-in / fan-out device disposed at one end of the optical fiber connector, and a second fan-in / fan-out device disposed at the other end of the optical fiber connector, wherein the port configuration structure of the first fan-in / fan-out device is the same as the port configuration structure of the second fan-in / fan-out device.

[0210] The method for manufacturing an optical fiber connector according to the second aspect 7 of the present invention is characterized in that the optical fiber connector is connected to a plurality of multi-core optical fibers with the same core configuration. Each multi-core optical fiber has an end face that includes a cladding, a plurality of cores arranged in a line symmetrical manner inside the cladding, and a mark disposed at a position other than the axis of symmetry of the plurality of cores. When the end face of one of the multi-core optical fibers that are adjacent to each other is set as a first end face and the end face of the other multi-core optical fiber is set as a second end face, the plurality of multi-core optical fibers are connected in such a way that the number of connection points satisfying the following conditions is an odd number: (1) the plurality of cores of the first end face coincide with the plurality of cores of the second end face; and (2) the mark of the first end face coincides with a position in the second end face that is line symmetrical with respect to the axis of symmetry with respect to the mark of the second end face.

[0211] (Appendix Item 3) The first and second aspects of the present invention are not limited to the embodiments or variations described above. Various modifications can be made within the scope shown in this specification. Any combination of the technical means disclosed in the embodiments or variations of the first aspect and the technical means disclosed in the embodiments or variations of the second aspect is also included in the technical scope of the present invention.

[0212] Confirmed, to the extent that there is no technical contradiction, the technical scope of the present invention may also include any of the following structures (1) to (6).

[0213] (1) The structure of any one of the embodiments 1 to 9 of the first aspect of the present invention.

[0214] (2) The structure formed by combining any two or more of the embodiments 1 to 9 of the first aspect of the present invention.

[0215] (3) The structure of any one of the embodiments 1 to 7 of the second aspect of the present invention.

[0216] (4) The structure formed by combining any two or more of the embodiments 1 to 7 of the second aspect of the present invention.

[0217] (5) A structure formed by combining any two or more of the structures in (1) to (4) above.

[0218] (6) A structure formed by combining any of the above-mentioned technical means in any combination of the structures (1) to (5).

[0219] (Summary 3) Regarding the optical fiber connector of Embodiment 1 of the present invention, it is characterized in that it comprises at least: a first multi-core optical fiber, which includes a plurality of cores disposed inside the cladding and a first mark; and a second multi-core optical fiber, which includes a plurality of cores disposed inside the cladding and a second mark, and one end face is connected to one end face of the first multi-core optical fiber, wherein the plurality of cores of the second multi-core optical fiber are respectively connected to any one of the plurality of cores of the first multi-core optical fiber, or the plurality of cores of the first multi-core optical fiber are respectively connected to any one of the plurality of cores of the second multi-core optical fiber.

[0220] Regarding the optical fiber connector of embodiment 2 of the present invention, in addition to the structure of embodiment 1, the following structure is also adopted: at least a portion of the second mark of the second multi-core optical fiber is connected to the portion of the first multi-core optical fiber other than the first mark, or at least a portion of the first mark of the first multi-core optical fiber is connected to the portion of the second multi-core optical fiber other than the second mark.

[0221] Regarding the optical fiber connector of embodiment 3 of the present invention, in addition to the structure of embodiment 2, the following structure is also adopted: the number of the plurality of cores of the first multi-core optical fiber and the number of the plurality of cores of the second multi-core optical fiber are both 2 or more. The fiber core of the second multi-core optical fiber that is closest to the second mark is connected to the fiber core of the first multi-core optical fiber that is other than the fiber core that is closest to the first mark.

[0222] Regarding the optical fiber connector of embodiment 4 of the present invention, in addition to the structure of embodiment 2, the following structure is also adopted: the number of the plurality of cores of the first multi-core optical fiber and the number of the plurality of cores of the second multi-core optical fiber are both 3 or more, and a pair consisting of two cores selected from the plurality of cores of the second multi-core optical fiber, or a pair consisting of the core closest to the second mark and the second closest core, or a pair consisting of the two cores closest to the second mark, is connected to: a pair consisting of two cores selected from the plurality of cores of the first multi-core optical fiber, other than the pair consisting of the core closest to the first mark and the second closest core, or a pair consisting of the two cores closest to the first mark.

[0223] Regarding the optical fiber connector of embodiment 5 of the present invention, in addition to the structure of embodiment 4, the following structure is also adopted: the refractive index of the first mark is lower than the refractive index of the cladding of the first multi-core optical fiber, and the refractive index of the second mark is lower than the refractive index of the cladding of the second multi-core optical fiber.

[0224] Regarding the optical fiber connector of embodiment 6 of the present invention, in addition to the structure of any one of embodiments 2 to 5, it also adopts the following structure: it further includes a third multi-core optical fiber, which has multiple cores and a third mark arranged inside the cladding, and one end face is connected to the other end face of the second multi-core optical fiber. The number of the multiple cores of the first multi-core optical fiber and the number of the multiple cores of the third multi-core optical fiber are both n, where n is a natural number greater than or equal to 2. If the ordinal number of the multiple cores of the first multi-core optical fiber is determined according to the arrangement order of the multiple cores of the first multi-core optical fiber, with the core closest to the first mark as the first and the second core closest to the first mark as the second, and according to... The order of the multiple cores of the second multi-core optical fiber is determined by arranging the cores in the order of the multiple cores, with the core closest to the second mark being the first and the core closest to the first mark being the second. Similarly, the order of the multiple cores of the third multi-core optical fiber is determined by arranging the cores in the order of the multiple cores, with the core closest to the third mark being the first and the core closest to the first mark being the second. In this case, the i-th core of the third multi-core optical fiber is connected to the core of the second multi-core optical fiber that is connected to the i-th core of the first multi-core optical fiber, where i is a natural number greater than or equal to 1 and less than or equal to n. Furthermore, in this method, it is preferable that the number of flip connections is an even number.

[0225] Regarding the optical fiber connector of embodiment 7 of the present invention, in addition to any of the structures of embodiments 2 to 5, the following structure is also adopted: it further comprises a third multi-core optical fiber, which has a plurality of cores and a third mark arranged inside the cladding, and one end face is connected to the other end face of the second multi-core optical fiber. The core of the plurality of cores of the third multi-core optical fiber that is closest to the third mark is connected to the core of the plurality of cores of the second multi-core optical fiber that satisfies the following (1) and (2): (1) the core is a core other than the core that is closest to the second mark, and (2) the core is a core other than the core that is connected to the core of the plurality of cores of the first multi-core optical fiber that is closest to the first mark.

[0226] Regarding the optical fiber connector of embodiment 8 of the present invention, in addition to the structure of any one of embodiments 2 to 7, the following structure is also adopted: in the first multi-core optical fiber, the first mark is configured such that the distance from the first mark to each of the plurality of fiber cores is completely different; in the second multi-core optical fiber, the second mark is configured such that the distance from the second mark to each of the plurality of fiber cores is completely different.

[0227] Regarding the optical fiber connector of embodiment 9 of the present invention, in addition to the structure of any one of embodiments 2 to 8, the following structure is also adopted: the second mark of the second multi-core optical fiber is entirely connected to the portion other than the first mark of the first multi-core optical fiber, or the first mark of the first multi-core optical fiber is entirely connected to the portion other than the second mark of the second multi-core optical fiber.

[0228] Regarding the optical fiber connector of embodiment 10 of the present invention, in addition to the structure of any one of embodiments 2 to 8, the following structure is also adopted: the second mark of the second multi-core optical fiber is only partially connected to the portion other than the first mark of the first multi-core optical fiber, or the first mark of the first multi-core optical fiber is only partially connected to the portion other than the second mark of the second multi-core optical fiber.

[0229] Regarding the optical fiber connector of embodiment 11 of the present invention, in addition to the structures of embodiments 2 to 10, the following structure is also adopted: In the one end face of the first multi-core optical fiber, the first mark coincides with the virtual vertical bisecting line of the virtual line segment connecting the center of the virtual core closest to the first mark and the center of the second closest core among the plurality of cores of the first multi-core optical fiber; or, in the one end face of the second multi-core optical fiber, the second mark coincides with the virtual vertical bisecting line of the virtual line segment connecting the center of the virtual core closest to the second mark and the center of the second closest core among the plurality of cores of the second multi-core optical fiber.

[0230] Regarding the optical fiber connector of embodiment 12 of the present invention, in addition to the structure of any one of embodiments 2 to 11, the following structure is also adopted: In the one end face of the first multi-core optical fiber, the center of the first mark does not coincide with the virtual vertical bisecting line of the virtual line segment connecting the center of the virtual core closest to the first mark and the center of the second closest core among the plurality of cores of the first multi-core optical fiber; or, in the one end face of the second multi-core optical fiber, the center of the second mark does not coincide with the virtual vertical bisecting line of the virtual line segment connecting the center of the virtual core closest to the second mark and the center of the second closest core among the plurality of cores of the second multi-core optical fiber.

[0231] Regarding the optical fiber connector of embodiment 13 of the present invention, in addition to the structure of any one of embodiments 2 to 12, the following structure is also adopted: in one end face of the first multi-core optical fiber or the one end face of the second multi-core optical fiber, the virtual straight line connecting the center of the first mark and the center of the second mark is parallel to: the virtual straight line connecting the center of the fiber core closest to the first mark and the center of the second closest fiber core, or the virtual straight line connecting the center of the fiber core closest to the second mark and the center of the second closest fiber core.

[0232] Regarding the optical fiber connector of embodiment 14 of the present invention, in addition to the structure of any one of embodiments 2 to 13, the following structure is also adopted: In one end face of the first multi-core optical fiber, the center of the first mark is disposed in the area enclosed by the following three (1) to (3): (1) a virtual circumscribed circle circumscribed in the plurality of cores of the first multi-core optical fiber, the core closest to the first mark and the second closest core, i.e., a virtual circumscribed circle centered on the center of the cladding of the first multi-core optical fiber; (2) a virtual bisecting line of the angle formed by a virtual straight line passing through the center of the core closest to the first mark and the center of the second closest core and a virtual straight line connecting the center of the core closest to the first mark and the center of the cladding; (3) a virtual straight line passing through the center of the core closest to the first mark and the center of the second closest core and connecting the center of the second closest core and the center of the cladding. The virtual bisecting line is the angle formed by the virtual straight line, or, in one end face of the second multi-core optical fiber, the center of the second mark is disposed in the area enclosed by the following three (1) to (3): (1) the virtual circumscribed circle of the fiber closest to the second mark and the second closest fiber among the plurality of fiber cores of the second multi-core optical fiber, i.e., the virtual circumscribed circle centered on the center of the cladding of the second multi-core optical fiber; (2) the virtual bisecting line is the angle formed by the virtual straight line passing through the center of the fiber closest to the second mark and the center of the second closest fiber and the virtual straight line connecting the center of the fiber closest to the second mark and the center of the cladding; (3) the virtual bisecting line is the angle formed by the virtual straight line passing through the center of the fiber closest to the second mark and the center of the second closest fiber and the virtual straight line connecting the center of the second closest fiber and the center of the cladding. In addition, in this embodiment, the center of the first mark or the center of the second mark can be the entire first mark or the entire second mark, respectively.

[0233] Regarding the optical fiber connector of embodiment 15 of the present invention, in addition to the structure of any one of embodiments 2 to 13, the following structure is also adopted: In one end face of the first multi-core optical fiber, the center of the first mark is disposed in the area enclosed by the following four elements (1) to (4): (1) a virtual circumscribed circle circumscribed in the plurality of cores of the first multi-core optical fiber, namely, a virtual circumscribed circle centered on the center of the cladding of the first multi-core optical fiber; (2) a virtual bisecting line forming the angle between a virtual straight line passing through the center of the core closest to the first mark and the center of the second closest core and a virtual straight line connecting the center of the core closest to the first mark and the center of the cladding; (3) the angle between a virtual straight line passing through the center of the core closest to the first mark and the center of the second closest core and a virtual straight line connecting the center of the second closest core and the center of the cladding. (4) The outer periphery of the cladding, or, in one end face of the second multi-core fiber, the center of the second mark is disposed in the area enclosed by the following (1) to (4): (1) the virtual circumscribed circle of the fiber closest to the second mark and the second closest fiber among the plurality of fibers of the second multi-core fiber, i.e., the virtual circumscribed circle centered on the center of the cladding of the second multi-core fiber; (2) the virtual bisector of the angle formed by the virtual straight line passing through the center of the fiber closest to the second mark and the center of the second closest fiber and the virtual straight line connecting the center of the fiber closest to the second mark and the center of the cladding; (3) the virtual bisector of the angle formed by the virtual straight line passing through the center of the fiber closest to the second mark and the center of the second closest fiber and the virtual straight line connecting the center of the second closest fiber and the center of the cladding; (4) the outer periphery of the cladding. In addition, in this method, the center of the first mark or the center of the second mark can be the entire first mark or the entire second mark, respectively.

[0234] Regarding the optical fiber connector of embodiment 16 of the present invention, in addition to the structure of any one of embodiments 1 to 15, the following structure is also adopted: a plurality of multi-core optical fibers including the first multi-core optical fiber and the second multi-core optical fiber are connected, the plurality of multi-core optical fibers including the following multi-core optical fibers: the multi-core optical fiber has an end face including a cladding, a plurality of cores arranged in a line symmetrical manner inside the cladding, and a mark, the center of the mark being disposed at a position other than the virtual axis of symmetry of the plurality of cores, for the connection portion of two adjacent multi-core optical fibers in the plurality of multi-core optical fibers, when the end face of one multi-core optical fiber is set as the first end face and the end face of the other multi-core optical fiber is set as the second end face, the number of connection portions satisfying the following conditions is odd: (1) the plurality of cores of the first end face coincide with any one of the plurality of cores of the second end face; and (2) the mark of the first end face coincides with a position in the second end face that is line symmetrical with respect to the virtual axis of symmetry with respect to the mark of the second end face. Furthermore, it is confirmed that the axis of symmetry of the first or second aspect of the present invention described above can be interpreted and understood as a virtual axis of symmetry.

[0235] Regarding the optical fiber connector of embodiment 17 of the present invention, in addition to the structure of embodiment 16, the following structure is also adopted: all the plurality of fiber cores are arranged outside the virtual axis of symmetry.

[0236] Regarding the optical fiber connector of embodiment 18 of the present invention, in addition to the structure of any one of embodiments 1 to 17, the following structure is also adopted: at both end faces of the optical fiber connector, the fiber cores for inputting optical signals are arranged diagonally opposite each other, and the fiber cores for outputting optical signals are also arranged diagonally opposite each other. Furthermore, the fiber cores for inputting optical signals or for outputting optical signals may also have the following structure: that is, the fiber core for inputting optical signals is a fiber core capable of optically coupling to the input port of an external transceiver, and the fiber core for outputting signals is a fiber core capable of optically coupling to the output port of an external transceiver.

[0237] Regarding the optical communication system of embodiment 19 of the present invention, the following structure is adopted: comprising: an optical fiber connector of any one of embodiments 1 to 18, a first transceiver disposed at one end of the optical fiber connector, and a second transceiver disposed at the other end of the optical fiber connector, wherein the port configuration structure described below (1) is the same as the port configuration structure described below (2): (1) a port configuration structure relating to the port of the first transceiver connected to the fiber core in the multi-core optical fiber at one end of the optical fiber connector that is capable of conducting signal light; or, in the first transceiver (2) A port configuration structure relating to the port of the first transceiver, in which the fiber core capable of conducting signal light is connected to the multi-core optical fiber connected to the second transceiver at the other end of the optical fiber connector; or, a port configuration structure relating to the port of the second transceiver, in which the fiber core capable of conducting signal light is connected to the multi-core optical fiber connected to the second transceiver at the other end of the optical fiber connector.

[0238] Regarding the optical device of embodiment 20 of the present invention, the following structure is adopted: comprising: an optical fiber connector of any one of embodiments 1 to 18, a first fan-in / fan-out device disposed at one end of the optical fiber connector, and a second fan-in / fan-out device disposed at the other end of the optical fiber connector, wherein the port configuration structure described below (1) is the same as the port configuration structure described below (2): (1) a port configuration structure relating to the port of the first fan-in / fan-out device connected to the fiber core in the multi-core optical fiber at one end of the optical fiber connector that is capable of conducting signal light; or, in the first fan-in / fan-out device (2) A port configuration structure relating to the port of the first fan-in / fan-out device, in which the core of the multi-core optical fiber capable of conducting signal light is connected to the second fan-in / fan-out device at the other end of the optical fiber connector; or, a port configuration structure relating to the port of the second fan-in / fan-out device, in which the core of the multi-core optical fiber capable of conducting signal light is connected to the second fan-in / fan-out device at the other end of the optical fiber connector; or, a port configuration structure relating to the port of the second fan-in / fan-out device, in which the core of the multi-core optical fiber capable of conducting signal light is connected to the second fan-in / fan-out device at the other end of the optical fiber connector.

[0239] Regarding the method for manufacturing an optical fiber connector according to embodiment 21 of the present invention, the method for manufacturing an optical fiber connector according to any one of embodiments 2 to 15 of the present invention is characterized by comprising the following steps: connecting one end face of the second multi-core optical fiber to one end face of the first multi-core optical fiber in such a manner that the plurality of cores of the second multi-core optical fiber are respectively connected to any one of the plurality of cores of the first multi-core optical fiber, or connecting the plurality of cores of the first multi-core optical fiber to any one of the plurality of cores of the second multi-core optical fiber; and connecting one end face of the second multi-core optical fiber to one end face of the first multi-core optical fiber in such a manner that at least a portion of the second mark of the second multi-core optical fiber is connected to a portion other than the first mark of the first multi-core optical fiber, or connecting at least a portion of the first mark of the first multi-core optical fiber to a portion other than the second mark of the second multi-core optical fiber.

[0240] Regarding the manufacturing method of the optical fiber connector according to embodiment 22 of the present invention, the method of manufacturing an optical fiber connector according to any one of embodiments 16 to 18 of the present invention is characterized in that, when the end face of one of the multiple multi-core optical fibers that are adjacent to each other is set as a first end face and the end face of the other multi-core optical fiber is set as a second end face, the multiple multi-core optical fibers are connected in such a way that the number of connection points satisfying the following conditions is an odd number: (1) the multiple cores of the first end face coincide with any one of the multiple cores of the second end face; and (2) the mark of the first end face coincides with a position in the second end face that is linearly symmetrical with respect to the virtual axis of symmetry with respect to the mark of the second end face.

[0241] Regarding the optical fiber connector of embodiment 23 of the present invention, in addition to the structure of any one of embodiments 2 to 12 or 15, the following structure is also adopted: In the one end face of the first multi-core optical fiber, the center of the first mark is disposed in the area (hereinafter also referred to as region F) enclosed by the following three (1) to (3): (1) a virtual circumscribed circle circumscribed in the plurality of cores of the first multi-core optical fiber, the core closest to the first mark and the second closest core, that is, a virtual circumscribed circle centered on the center of the cladding of the first multi-core optical fiber; (2) a virtual bisecting line of the angle formed by a virtual straight line passing through the center of the core closest to the first mark and the center of the second closest core and a virtual straight line connecting the center of the core closest to the first mark and the center of the cladding; (3) a virtual bisecting line of the virtual straight line connecting the core closest to the first mark and the center of the cladding. The virtual straight line connecting the center of the core and the center of the cladding, or, in one end face of the second multi-core optical fiber, the center of the second mark is disposed in the area enclosed by the following three (1) to (3) (hereinafter also referred to as area G): (1) a virtual circumscribed circle circumscribed in the plurality of cores of the second multi-core optical fiber, the core closest to the second mark and the second closest core, i.e., a virtual circumscribed circle centered on the center of the cladding of the second multi-core optical fiber; (2) a virtual bisecting line of the angle formed by the virtual straight line passing through the center of the core closest to the second mark and the center of the second closest core and the virtual straight line connecting the center of the core closest to the second mark and the center of the cladding; (3) a virtual straight line connecting the center of the core closest to the second mark and the center of the cladding. In this embodiment, in addition to the structures described in (1) to (3) above, the structure of the outer periphery of cladding 111b or the outer periphery of cladding 112b (4) can also be used. In this case, the center of the first mark or the center of the second mark is located within the area enclosed by the four elements (1) to (4) described above (hereinafter referred to as areas H and I, respectively). Alternatively, the center of the first mark may be located across the boundary between area F and area H, or the center of the second mark may be located across the boundary between area G and area I. Furthermore, the center of the first mark or the center of the second mark may be the entire first mark or the entire second mark as described above.

[0242] Regarding the optical fiber connector of embodiment 24 of the present invention, in addition to the structure of any one of embodiments 2 to 12, 14, 15 or 23, the following structure is also adopted: In one end face of the first multi-core optical fiber, the center of the first mark coincides with the virtual vertical bisecting line of the virtual line segment connecting the center of the virtual core closest to the first mark and the center of the second virtual core among the plurality of cores of the first multi-core optical fiber; In one end face of the second multi-core optical fiber, the center of the second mark coincides with the virtual vertical bisecting line of the virtual line segment connecting the center of the virtual core closest to the second mark and the center of the second virtual core among the plurality of cores of the second multi-core optical fiber; The distance between the center of the first mark and the center of the virtual core closest to the first mark, the distance between the second virtual core closest to the first mark and the center of the second virtual core, and the distance between the center of the second mark and the center of the virtual core closest to the second mark and the center of the second virtual core closest to the second mark are approximately the same. In this approach, the following structure can also be adopted: the second mark of the second multi-core optical fiber is only partially connected to the portion other than the first mark of the first multi-core optical fiber, or the first mark of the first multi-core optical fiber is only partially connected to the portion other than the second mark of the second multi-core optical fiber. Alternatively, the following structure can also be adopted: the second mark of the second multi-core optical fiber is entirely connected to the portion other than the first mark of the first multi-core optical fiber, or the first mark of the first multi-core optical fiber is entirely connected to the portion other than the second mark of the second multi-core optical fiber.

[0243] According to the above structure, the distances between the first marker and the two fiber cores, and the distances between the second marker and the two fiber cores, are approximately the same. Therefore, the degradation of signal light transmitted in the two fiber cores 111 of the first multi-core fiber 111, or the degradation of signal light transmitted in the two fiber cores 112 of the second multi-core fiber 112, can be made more uniform. As a result, the possibility of errors occurring in communications using signal light transmitted in the two fiber cores 111 of the first multi-core fiber 111, or the two fiber cores 112 of the second multi-core fiber 112, can be further reduced. Furthermore, the aforementioned effect of reducing crosstalk can be achieved. Since crosstalk between the two fiber cores near the first marker and the two fiber cores near the second marker may worsen, pairs of fiber cores with poor crosstalk characteristics can be dispersed. Therefore, the degradation of crosstalk can be made more uniform, thereby achieving the effect of suppressing crosstalk in the two multi-core fibers.

[0244] (Appendix Item 4) The first and second aspects of the present invention are not limited to the embodiments or variations described above. Various modifications can be made within the scope shown in this specification. Any combination of the technical means disclosed in the embodiments or variations of the first aspect and the technical means disclosed in the embodiments or variations of the second aspect is also included in the technical scope of the present invention.

[0245] Confirmed, to the extent that there is no technical contradiction, the technical scope of the present invention may also include the following structures (1) to (10).

[0246] (1) The structure of any one of the embodiments 1 to 15, 21, 23 and 24 of the present invention.

[0247] (2) The structure formed by combining any two or more of the embodiments 1 to 15, 21, 23 and 24 of the present invention.

[0248] (3) The structure formed by combining at least one of the embodiments 1 to 15, 21, 23, 24 of the present invention or any two or more embodiments of the first aspect of the present invention.

[0249] (4) The structure formed by combining at least one of the embodiments 1 to 15, 21, 23, 24 of the present invention or any two or more embodiments of the second aspect of the present invention.

[0250] (5) The structure of any one of the embodiments 1, 16 to 20, 22 of the present invention.

[0251] (6) The structure formed by combining any two or more of the embodiments 1, 16 to 20, and 22 of the present invention.

[0252] (7) A structure formed by combining at least one of the embodiments 1, 16 to 20, 22 of the present invention or any two or more embodiments of the first aspect of the present invention.

[0253] (8) A structure formed by combining at least one of the embodiments 1, 16 to 20, 22 of the present invention or any two or more embodiments of the second aspect of the present invention.

[0254] (9) A structure formed by combining any two or more of the structures in (1) to (8) above.

[0255] (10) A structure formed by combining any of the above-mentioned technical means in any of the structures in (1) to (9).

[0256] In addition, confirming that, to the extent that there is no technical contradiction, the technical scope of the present invention may also include the following structures (1) to (18).

[0257] (1) A structure formed by adding the structure of the optical fiber connector of the first aspect of the present invention, or the structure of the optical fiber connector of the present invention, to the structure of the optical fiber connector of the present invention, or the structure of the optical fiber connector of the first aspect of the present invention, or ... second aspect of the present invention, or the structure of the optical fiber connector of the third aspect of

[0258] (2) A structure formed by adding the structure of the optical fiber connector of the first aspect of the present invention to the structure of the optical fiber connector of embodiment 1 or 4 of the present invention.

[0259] (3) A structure formed by adding the structure of the optical fiber connector of the first aspect of the present invention, or the structure of the optical fiber connector of any one of the optical fiber connectors of the present invention, from aspect 1 to aspect 6, to the structure of the optical fiber connector of the present invention.

[0260] (4) A structure formed by adding the structure of the optical fiber connector of the first aspect of the present invention to the structure of any one of the optical fiber connectors of embodiments 1 to 7 of the present invention.

[0261] (5) A structure formed by adding the structure of the optical fiber connector of the first aspect of the present invention to the structure of any one of the optical fiber connectors of embodiments 1 to 18 of the present invention.

[0262] (6) A structure formed by adding the structure of the fiber optic connector manufacturing method of the first aspect of the present invention to the structure of the fiber optic connector manufacturing method of the first aspect of the present invention, which adopts the structure of any one of the fiber optic connectors of the present invention 1 to 15, 23 or 24, or a structure formed by adding the structure of the first aspect of the present invention 9 to the structure of the fiber optic connector manufacturing method of the first aspect of the present invention.

[0263] (7) A structure formed by adding the structure of the optical fiber connector of the second aspect of the present invention to the structure of any one of the optical fiber connectors of the present invention in embodiments 1 to 15, 23 or 24.

[0264] (8) A structure formed by adding the structure of the optical fiber connector of the second aspect of the present invention to the structure of any one of the optical fiber connectors of the present invention in embodiments 1 to 16, 23 or 24.

[0265] (9) A structure formed by adding the structure of the optical fiber connector of the second aspect of the present invention to the structure of any one of the optical fiber connectors of the present invention, from aspect 1 to 17, aspect 23 or aspect 24.

[0266] (10) A structure formed by adding the structure of the optical fiber connector of the second aspect of the present invention to the structure of any one of the optical fiber connectors of the present invention, from aspect 1 to 18, aspect 23 or aspect 24.

[0267] (11) A structure formed by adding the structure of the optical communication system of the second aspect of the present invention to the structure of the optical fiber connector of any one of the optical fiber connectors of the present invention (1 to 18, 23 or 24) or the structure of the optical communication system of the present invention (19).

[0268] (12) A structure formed by adding the structure of the optical device of the second aspect of the present invention to the structure of the optical device of the second aspect of the present invention of the form 6, which adopts the structure of the optical fiber connector of any one of the forms 1 to 18, 23 or 24 of the present invention, or the structure of the optical device of the second aspect of the present invention of the form 20.

[0269] (13) A structure formed by adding the structure of the fiber optic connector manufacturing method of the second aspect of the present invention to the structure of the fiber optic connector manufacturing method of any one of the fiber optic connectors of the present invention (16 to 18), or a structure formed by adding the structure of the second aspect of the present invention (7) to the structure of the fiber optic connector manufacturing method of the present invention (22).

[0270] (14) A structure formed by adding the structure of any one of the optical fiber connectors of the present invention, namely, ...

[0271] (15) A structure formed by adding the structure of the optical fiber connector of the present invention ...

[0272] (16) The structure of the optical communication system of embodiment 19 of the present invention, which adopts the structure of the optical fiber connector of embodiment 8 of the first aspect of the present invention, embodiment 3 of the second aspect of the present invention, or embodiment 23 or 24 of the present invention.

[0273] (17) The structure of the optical device of the present invention of embodiment 20, which adopts the structure of the optical fiber connector of the first aspect of the present invention, embodiment 3 of the second aspect of the present invention, or embodiment 23 or 24 of the present invention.

[0274] (18) A structure formed by combining any of the technical means disclosed in the embodiments or variations of the first aspect and at least one of the technical means disclosed in the embodiments or variations of the second aspect in any of the structures (1) to (17) above.

[0275] Confirmedly, the structures of the optical fiber connectors of embodiments 2 to 4 of the present invention can also be interpreted as higher-level concepts than the structures of the optical fiber connectors of embodiments 1 to 3 of the first aspect of the present invention. Furthermore, the structures of the optical fiber connectors of embodiments 6 to 8 of the present invention can also be interpreted as higher-level concepts than the structures of the optical fiber connectors of embodiments 5 to 7 of the first aspect of the present invention. Furthermore, the structure of the optical fiber connector of embodiment 16 of the present invention can also be interpreted as a higher-level concept than the structure of the optical fiber connector of embodiment 1 of the second aspect of the present invention. Furthermore, the structure of the optical communication system of embodiment 19 of the present invention can also be interpreted as a higher-level concept than the structure of the optical communication system of embodiment 5 of the second aspect of the present invention. Furthermore, the structure of the optical device of embodiment 20 of the present invention can also be interpreted as a higher-level concept than the structure of the optical device of embodiment 6 of the second aspect of the present invention. Furthermore, the structure of the method for manufacturing the optical fiber connector of embodiment 21 of the present invention can also be interpreted as a higher-level concept than the structure of the method for manufacturing the optical fiber connector of embodiment 9 of the first aspect of the present invention. Furthermore, the structure of the method for manufacturing the optical fiber connector of embodiment 22 of the present invention can also be interpreted as a higher-level concept than the structure of the method for manufacturing the optical fiber connector of embodiment 7 of the second aspect of the present invention.

[0276] Furthermore, it is confirmed that the optical fiber connector of the first or second aspect of the present invention can be composed of two interconnected multi-core optical fibers. Furthermore, it is confirmed that the position of the first mark or the position of the second mark of the optical fiber connector of the first aspect of the present invention is not particularly limited as long as it satisfies at least one of the embodiments 1 or 2 of the present invention; for example, it can be a structure as follows: In one end face of the first multi-core optical fiber, with respect to the first mark, which is arranged relative to a virtual vertical bisecting line connecting the center of the virtual line segment connecting the center of the fiber closest to the first mark and the center of the second closest fiber among the plurality of fiber cores of the first multi-core optical fiber; and in one end face of the second multi-core optical fiber, with respect to the second mark, which is arranged relative to a virtual vertical bisecting line connecting the center of the virtual line segment connecting the center of the fiber closest to the second mark and the center of the second closest fiber among the plurality of fiber cores of the second multi-core optical fiber, it can be linearly symmetrical with respect to either of the aforementioned vertical bisecting lines, or rotationally symmetrical, or asymmetrical. Explanation of reference numerals in the attached figures

[0277] 101 - Fiber optic connector; 111 - First multi-core fiber; 111a1~111an - Fiber core; 111b - Cladding; 111c - Marking; 112 - Second multi-core fiber; 112a1~112an - Fiber core; 112b - Cladding; 112c - Marking; 113 - Third multi-core fiber; 113a1~113an - Fiber core; 113b - Cladding; 113c - Marking; 102 - Fiber optic connector; 121 - First multi-core fiber; 121 a1~121an - Fiber core; 121b - Cladding; 121c - Marking; 122 - Second multi-core fiber; 122a1~122an - Fiber core; 122b - Cladding; 122c - Marking; 201 - Fiber connector; MF, MF1~MFm - Multi-core fiber; a1~an - Fiber core; b - Cladding; c - Marking; 210 - Optical communication system; 202, 203 - Transceiver; 220 - Optical equipment; 204, 205 - Fan-in / fan-out devices.

Claims

1. An optical fiber connector, comprising multiple multi-core optical fibers, characterized in that, The plurality of multi-core optical fibers each have an end face that includes a cladding, a plurality of fiber cores, and a marker. The plurality of fiber cores are arranged linearly symmetrically within the cladding relative to a virtual axis of symmetry. The center of the marker is located outside the virtual axis of symmetry. The plurality of fiber cores are identified from each other on both end faces of the optical fiber connector based on the distance from the marker. For the connection points of two adjacent multi-core optical fibers in the plurality of multi-core optical fibers, when the end face of one multi-core optical fiber is set as the first end face and the end face of the other multi-core optical fiber is set as the second end face, the number of connection points that satisfy the following conditions is odd, and both end faces of the optical fiber connector are the same type of end face of the multi-core optical fiber, the conditions being: (1) the plurality of fiber cores of the first end face coincide with any one of the plurality of fiber cores of the second end face; and (2) the mark of the first end face coincides with the position in the second end face that is linearly symmetrical with respect to the virtual axis of symmetry with respect to the mark of the second end face.

2. The optical fiber connector according to claim 1, characterized in that, The plurality of fiber cores are all positioned outside the virtual axis of symmetry.

3. The optical fiber connector according to claim 1, characterized in that, In the two end faces of the optical fiber connector, the fiber cores for input optical signals are arranged diagonally opposite each other, and the fiber cores for output optical signals are arranged diagonally opposite each other.

4. An optical communication system, characterized in that, It comprises: the optical fiber connector as described in claim 1, a first transceiver disposed at one end of the optical fiber connector, and a second transceiver disposed at the other end of the optical fiber connector. The port configuration structure described in (1) below is the same as the port configuration structure described in (2) below: (1) A port configuration structure relating to the port of the first transceiver, where the fiber core capable of conducting signal light in a multi-core optical fiber connected to the first transceiver at one end of the optical fiber connector is located; or, a port configuration structure relating to the port of the first transceiver, where the fiber core capable of conducting signal light in a multi-core optical fiber connected between the first transceiver and one end of the optical fiber connector is located. (2) A port configuration structure relating to the port of the second transceiver, in which the fiber core capable of conducting signal light in the multi-core optical fiber connected to the second transceiver is located at the other end of the optical fiber connector; or, a port configuration structure relating to the port of the second transceiver, in which the fiber core capable of conducting signal light in the multi-core optical fiber connected between the second transceiver and the other end of the optical fiber connector is connected to the port of the second transceiver.

5. An optical device, characterized in that, have: The optical fiber connector of claim 1, the first fan-in / fan-out device disposed at one end of the optical fiber connector, and the second fan-in / fan-out device disposed at the other end of the optical fiber connector. The port configuration structure described in (1) below is the same as the port configuration structure described in (2) below: (1) A port configuration structure relating to the port of the first fan-in / fan-out device, where the core of the multi-core optical fiber capable of conducting signal light is connected to the first fan-in / fan-out device at one end of the optical fiber connector; or, a port configuration structure relating to the port of the first fan-in / fan-out device, where the core of the multi-core optical fiber capable of conducting signal light is connected to the port of the first fan-in / fan-out device, which is connected between the first fan-in / fan-out device and one end of the optical fiber connector. (2) A port configuration structure relating to the port of the second fan-in / fan-out device, in which the fiber core capable of conducting signal light is connected to the multi-core optical fiber connected to the second fan-in / fan-out device at the other end of the optical fiber connector; or, a port configuration structure relating to the port of the second fan-in / fan-out device, in which the fiber core capable of conducting signal light is connected to the multi-core optical fiber connected between the second fan-in / fan-out device and the other end of the optical fiber connector.

6. A method for manufacturing an optical fiber connector, wherein the optical fiber connector of claim 1 is manufactured, characterized in that, When the end face of one of the multi-core optical fibers that are adjacent to each other is set as the first end face and the end face of the other multi-core optical fiber is set as the second end face, the multi-core optical fibers are connected in such a way that the number of connection points that satisfy the following conditions is odd and both end faces of the optical fiber connector are the same type of end face of the multi-core optical fiber, the conditions being: (1) the multiple cores of the first end face coincide with any one of the multiple cores of the second end face; and (2) the mark of the first end face coincides with the position of the mark of the second end face that is linearly symmetrical with respect to the virtual axis of symmetry in the second end face.

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