Optical input / output device

Abstract

To provide an optical input / output device capable of reducing crosstalk that affects communication.SOLUTION: An optical input / output device disclosed herein comprises a fan-in fan-out device configured to optically couple each core to a corresponding transmission core at one ends of first transmission single core fibers, and optically couple each core and a corresponding reception core at one ends of first reception single core fibers.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical input / output device.

Background Art

[0002] Multi-core fibers in which a plurality of cores are arranged in a cladding are known, and devices for injecting light into or emitting light from this multi-core fiber are known. Patent Document 1 below describes an optical connector which is an example of this device. In this optical connector, each core of a multi-core fiber and each core of a plurality of single-core fibers are optically connected via respective waveguides formed in a waveguide substrate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a multi-core fiber, crosstalk is likely to occur because the distance between cores is small. For this reason, it is desirable that an optical signal with reduced crosstalk that affects communication propagates.

[0005] Therefore, an object of the present invention is to provide an optical input / output device capable of reducing crosstalk that affects communication.

[0006] To achieve the above object, the optical input / output device of the present invention includes a plurality of multi-core fibers each including at least one transmission core and at least one reception core, a first single-core fiber for transmission having the same number as the total number of the transmission cores of all the multi-core fibers, a first single-core fiber for reception having the same number as the total number of the reception cores of all the multi-core fibers, and a fan-in / fan-out device having the same number as all the multi-core fibers. The fan-in / fan-out device corresponding to each multi-core fiber optically couples each core at one end of the first single-core fiber for transmission having the same number as the transmission cores of the multi-core fiber and each of the transmission cores of the multi-core fiber, and optically couples each core at one end of the first single-core fiber for reception having the same number as the reception cores of the multi-core fiber and each of the reception cores of the multi-core fiber.

[0007] As described above, according to the present invention, an optical input / output device capable of reducing crosstalk that affects communication can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for implementing the optical input / output device according to the present invention are illustrated together with the accompanying drawings. The embodiments illustrated below are for facilitating the understanding of the present invention and are not for limiting the interpretation of the present invention. The present invention can be changed and improved from the following embodiments without departing from its gist. Also, in this specification, for ease of understanding, the dimensions of each member may be exaggeratedly shown.

[0010] FIG. 1 is a diagram showing an outline of the optical input / output device according to the embodiment. As shown in FIG. 1, the optical input / output device 1 of the present embodiment mainly includes a multi-core fiber 10, a first transmission optical fiber 21, a first reception optical fiber 22, a fan-in / fan-out device 30, a transmission / reception connector 40, and a patch cord 3.

[0011] The optical input / output device 1 of the present embodiment is a device that performs optical transmission and reception with a transceiver 100 having a plurality of transmission ports 101 and a plurality of reception ports 102. The plurality of transmission ports 101 of the transceiver 100 are arranged in a row and transmit optical signals to the optical input / output device 1. Also, the plurality of reception ports 102 of the transceiver 100 are arranged in a row and receive optical signals emitted from the optical input / output device 1. In the present embodiment, the transceiver 100 has a plurality of unused ports 103 that do not perform optical signal transmission and reception, arranged linearly at a predetermined interval. Each transmission port 101 is arranged at the above-mentioned predetermined interval on the extension line of the straight line where the unused port 103 is arranged on one side with respect to the unused port 103. Also, each reception port 102 is arranged at the above-mentioned predetermined interval on the extension line of the straight line where the unused port 103 is arranged on the other side with respect to the unused port 103.

[0012] In the present embodiment, there are a plurality of multi-core fibers 10 included in the optical input / output device 1. In the example shown in FIG. 1, the optical input / output device 1 includes two multi-core fibers 10.

[0013] Each multi-core fiber 10 of the present embodiment includes a transmission core 11 that propagates light from one end side to the other end side, a reception core 12 that propagates light from the other end side to the one end side, and a clad 13 that surrounds the outer peripheral surfaces of the transmission core 11 and the reception core 12. In this example, each multi-core fiber 10 includes a plurality of transmission cores 11 and a plurality of reception cores 12. Specifically, as shown in FIG. 1, each multi-core fiber 10 includes two transmission cores 11 and two reception cores 12, respectively. Each transmission core 11 and each reception core 12 propagate light of a wavelength used for communication in single mode. However, each transmission core 11 and each reception core 12 may propagate light of a wavelength used for communication in multiple modes, and in this case, signals can be superimposed on the light of each mode.

[0014] In each multi-core fiber 10 shown in this example, a pair of transmission cores 11 and a pair of reception cores 12 are arranged at opposite vertices of a square. Since the vertices located on one side and the other side of one side of the square are adjacent vertices at the shortest distance, in each multi-core fiber 10 of this example, the core pair adjacent to each other at the shortest distance is a transmission / reception core pair in which one is a transmission core 11 and the other is a reception core 12.

[0015] The first transmission optical fiber 21 and the first reception optical fiber 22 are each a single-core fiber. Therefore, the first transmission optical fiber 21 and the first reception optical fiber 22 can be understood as a first single-core transmission optical fiber and a first single-core reception optical fiber, respectively. The number of the first transmission optical fibers 21 is the same as the total number of the transmission cores 11 of all the multi-core fibers 10. In the example of FIG. 1, since two multi-core fibers 10 each include two transmission cores 11, the total number of the transmission cores 11 is four, and the number of the first transmission optical fibers 21 is four. Also, the number of the first reception optical fibers 22 is the same as the total number of the reception cores 12 of all the multi-core fibers 10. In the example of FIG. 1, since two multi-core fibers 10 each include two reception cores 12, the total number of the reception cores 12 is four, and the number of the first reception optical fibers 22 is four.

[0016] In addition, in the optical input / output device 1 of the present embodiment, all the multi-core fibers 10 are longer than their respective first transmission optical fibers 21 and their respective first reception optical fibers 22. However, all the multi-core fibers 10 may be shorter than their respective first transmission optical fibers 21 and their respective first reception optical fibers 22.

[0017] The fan-in / fan-out device 30 optically couples each core at one end of each first transmission optical fiber 21 with each transmission core 11, and optically couples each core at one end of each first reception optical fiber 22 with each reception core 12. The fan-in / fan-out device 30 may be a device of a free-space optical system that performs the above coupling via space, or may be a device of a waveguide system that performs the above coupling via a waveguide formed in the device. In FIG. 1, an example of the optical path of transmission light in the fan-in / fan-out device 30 is indicated by a broken line, and an example of the optical path of reception light is indicated by a dotted line. Therefore, it may be understood that the core of the multi-core fiber 10 optically connected to the first transmission optical fiber 21 is the transmission core 11, and the core of the multi-core fiber 10 optically connected to the first reception optical fiber 22 is the reception core 12.

[0018] In a device of a spatial optical system, for example, a lens is used. In this case, one end of each first transmission optical fiber 21 and one end of each first reception optical fiber 22 are arranged in the same manner as the arrangement of each transmission core 11 and each reception core 12 to be coupled to each other, and a lens is arranged between the multi-core fiber 10, the first transmission optical fiber 21, and the first reception optical fiber 22. Then, the positions of each multi-core fiber 10, the lens, the first transmission optical fiber 21, and the first reception optical fiber 22 are adjusted so as to be coupled as described above. Therefore, each light emitted from the core of each first transmission optical fiber 21 is refracted by the lens and enters the transmission core 11 of the multi-core fiber 10, and each light emitted from each reception core 12 of the multi-core fiber 10 is refracted by the lens and enters the core of each first reception optical fiber 22.

[0019] In a device of a waveguide system, for example, a waveguide substrate in which waveguides are three-dimensionally formed is used. In this case, for example, one ends of a plurality of waveguides connected to the cores of each first transmission optical fiber 21 and the cores of each reception core 12 are linearly arranged on one end side of the waveguide substrate, and the position of the waveguide is changed by forming a part of the waveguide in a curved shape in the waveguide substrate, and on the other end side of the waveguide substrate, waveguides are arranged in the same manner as the arrangement of each transmission core 11 and each reception core 12 in each multi-core fiber 10. Thus, the above coupling is made. Therefore, each light emitted from the core of each first transmission optical fiber 21 propagates through the waveguide and enters the transmission core 11 of the multi-core fiber 10, and each light emitted from each reception core 12 of the multi-core fiber 10 propagates through the waveguide and enters the core of each first reception optical fiber 22.

[0020] The transmission / reception connector 40 includes the same number of transmission connector ports 41 as the number of the first transmission optical fibers 21 that are connected in a one-to-one correspondence to the other ends of the respective first transmission optical fibers 21, and the same number of reception connector ports 42 as the number of the first reception optical fibers 22 that are connected in a one-to-one correspondence to the other ends of the respective first reception optical fibers 22. Therefore, the number of the plurality of connector ports including the respective transmission connector ports 41 and the respective reception connector ports 42 is the same as the total number of the first transmission optical fibers 21 and the first reception optical fibers 22. Each of the transmission connector ports 41 can optically couple the core of each of the first transmission optical fibers 21 and the transmission port 101 of the transceiver 100 via the patch cord 3 described later. Also, each of the reception connector ports 42 can optically couple the core of each of the first reception optical fibers 22 and the reception port 102 of the transceiver 100 via the patch cord 3. FIG. 1 shows a state where the core of each of the first transmission optical fibers 21 and the transmission port 101 of the transceiver 100 are optically coupled, and the core of each of the first reception optical fibers 22 and the reception port 102 of the transceiver 100 are optically coupled.

[0021] In addition, the transmission / reception connector 40 includes a dummy port 43 that does not perform optical transmission / reception. In the present embodiment, the number of dummy ports 43 is the same as the number of unused ports 103 of the transceiver 100 and they are arranged linearly. Each transmission connector port 41, each dummy port 43, and each reception connector port 42 are arranged in the same manner as each transmission port 101, each unused port 103, and each reception port 102 in the transceiver 100. Therefore, each transmission connector port 41 is arranged on one side with respect to the dummy port 43, and each reception connector port 42 is arranged on the other side with respect to the dummy port 43. Since each transmission connector port 41 is arranged in a group and each reception connector port 42 is arranged in a group, in the example of FIG. 1, at least a part of the first transmission optical fiber 21 and at least a part of the first reception optical fiber 22 are arranged so as to cross each other. Note that when one end of each first transmission optical fiber 21 is arranged in a group and one end of each first reception optical fiber 22 is arranged in a group, and the core of each first transmission optical fiber 21 and the core of each first reception optical fiber 22 are coupled to the fan-in / fan-out device 30, unlike the example of FIG. 1, the first transmission optical fiber 21 and the first reception optical fiber 22 do not have to be arranged so as to cross each other.

[0022] As shown in FIG. 1, in the present embodiment, the cores of the respective first transmission optical fibers 21 connected to a pair of adjacent transmission connector ports 41 are optically coupled to the transmission cores 11 of different multi-core fibers 10 via the fan-in / fan-out device 30, respectively. Also, the cores of the respective first reception optical fibers 22 connected to a pair of adjacent reception connector ports 42 are optically coupled to the reception cores 12 of different multi-core fibers 10 via the fan-in / fan-out device 30, respectively.

[0023] In this embodiment, a part of each multi-core fiber 10, a fan-in / fan-out device 30, each first transmission optical fiber 21, and each first reception optical fiber 22 are accommodated in the space of the housing 2, and the transmission / reception connector 40 is fixed to the wall surface of the housing 2. The other part of each multi-core fiber 10 is led out from the housing 2. In the optical input / output device 1 of this embodiment, it is preferable that the length of all the multi-core fibers 10 in the housing 2 is longer than that of each first transmission optical fiber 21 and each first reception optical fiber 22 in the housing 2. However, the length of all the multi-core fibers 10 in the housing 2 may be shorter than that of each first transmission optical fiber 21 and each first reception optical fiber 22 in the housing 2. Note that all of each multi-core fiber 10 may be arranged in the housing 2. Further, the transmission / reception connector 40 may be fixed to the wall surface of the housing 2 via an adapter (not shown).

[0024] Next, the patch cord 3 will be described. The patch cord 3 includes the same number of second transmission optical fibers 61 as the first transmission optical fibers 21, the same number of second reception optical fibers 62 as the first reception optical fibers 22, a first intermediate connector 50 connected to one ends of the second transmission optical fibers 61 and the second reception optical fibers 62, and a second intermediate connector 70 connected to the other ends of the second transmission optical fibers 61 and the second reception optical fibers 62.

[0025] The second transmission optical fiber 61 and the second reception optical fiber 62 are each single-core fibers. Therefore, the second transmission optical fiber 61 and the second reception optical fiber 62 can be understood as a second transmission single-core fiber and a second reception single-core fiber, respectively. In the present embodiment, the second transmission optical fiber 61 is longer than the first transmission optical fiber 21, and the second reception optical fiber 62 is longer than the first reception optical fiber 22. Further, the outer diameter of each cladding of the second transmission optical fiber 61 and the second reception optical fiber 62 is larger than the outer diameter of each cladding of the first transmission optical fiber 21 and the first reception optical fiber 22. Therefore, the microbend losses of the second transmission optical fiber 61 and the second transmission optical fiber 61 tend to be smaller than the microbend losses of the first transmission optical fiber 21 and the first reception optical fiber 22. Also, because of the relationship of the outer diameters of the claddings as described above, the bending breakage probabilities of the first transmission optical fiber 21 and the first reception optical fiber 22 tend to be lower than those of the second transmission optical fiber 61 and the second transmission optical fiber 61. Also, the optical confinement force of each of the first transmission optical fiber 21 and the first reception optical fiber 22 is made larger than the optical confinement force of each of the second transmission optical fiber 61 and the second reception optical fiber 62. As a configuration having such a relationship of optical confinement force, for example, a configuration in which the relative refractive index difference of each core of the first transmission optical fiber 21 and the first reception optical fiber 22 is made larger than the relative refractive index difference of each core of the second transmission optical fiber 61 and the second reception optical fiber 62 can be cited. In this case, it is preferable that the refractive index of each core of the first transmission optical fiber 21 and the first reception optical fiber 22 is higher than the refractive index of each core of the second transmission optical fiber 61 and the second reception optical fiber 62. Alternatively, each of the first transmission optical fiber 21 and the first reception optical fiber 22 may have a core, a cladding that surrounds the core and has a refractive index lower than that of the core, and a trench layer that surrounds the core and is surrounded by the cladding and has a refractive index lower than that of the cladding, and each of the second transmission optical fiber 61 and the second reception optical fiber 62 may have a core and a cladding that surrounds the core and has a refractive index lower than that of the core, and may not have a trench layer that surrounds the core and is surrounded by the cladding and has a refractive index lower than that of the cladding.

[0026] The first intermediate connector 50 includes the same number of first intermediate transmission connector ports 51 as the number of the second optical fibers 61 for transmission connected to one end of each of the second optical fibers 61 for transmission, and the same number of first intermediate reception connector ports 52 as the number of the second optical fibers 62 for reception connected to one end of each of the second optical fibers 62 for reception. Therefore, the number of the first intermediate connector ports composed of each of the first intermediate transmission connector ports 51 and each of the first intermediate reception connector ports 52 is the same as the total number of the second optical fibers 61 for transmission and the second optical fibers 62 for reception.

[0027] Also, in the present embodiment, the first intermediate connector 50 includes dummy ports 53 that do not perform optical transmission and reception. In the present embodiment, the number of the dummy ports 53 is the same as the number of the dummy ports 43, and they are arranged in the same manner as the dummy ports 43. Each of the first intermediate transmission connector ports 51, each of the dummy ports 53, and each of the first intermediate reception connector ports 52 are arranged in the same manner as each of the transmission connector ports 41, each of the dummy ports 43, and each of the reception connector ports 42 in the transmission and reception connector 40. Therefore, each of the first intermediate transmission connector ports 51 is arranged on one side with reference to the dummy port 53, and each of the first intermediate reception connector ports 52 is arranged on the other side with reference to the dummy port 53.

[0028] The first intermediate connector 50 is positioned by an adapter (not shown) or the like and connected to the transceiver connector 40. For this reason, each first intermediate transmission connector port 51 is connected to each transmission connector port 41 of the transceiver connector 40, and each first intermediate reception connector port 52 is connected to each reception connector port 42 of the transceiver connector 40. As a result, the core at the other end of the first transmission optical fiber 21 connected to each transmission connector port 41 is optically coupled to the core of the second transmission optical fiber 61 connected to each first intermediate transmission connector port 51, and the core at the other end of the first reception optical fiber 22 connected to each reception connector port 42 is optically coupled to the core of the second reception optical fiber 62 connected to each first intermediate reception connector port 52.

[0029] The second intermediate connector 70 includes the same number of second intermediate transmission connector ports 71 as the number of the second transmission optical fibers 61 connected to the other ends of the respective second transmission optical fibers 61, and the same number of second intermediate reception connector ports 72 as the number of the second reception optical fibers 62 connected to the other ends of the respective second reception optical fibers 62. Therefore, the number of second intermediate connector ports composed of each second intermediate transmission connector port 71 and each second intermediate reception connector port 72 is the same as the total number of the second transmission optical fibers 61 and the second reception optical fibers 62.

[0030] In addition, in the present embodiment, the second intermediate connector 70 includes a dummy port 73 that does not transmit or receive light. In the present embodiment, the number of dummy ports 73 is the same as that of the unused ports 103 of the transceiver 100, and they are arranged in the same manner as the unused ports 103. Each second intermediate transmission connector port 71, each dummy port 73, and each second intermediate reception connector port 72 are arranged in the same manner as each transmission port 101, each unused port 103, and each reception port 102 in the transceiver 100. Therefore, each second intermediate transmission connector port 71 is arranged on one side with respect to the dummy port 73, and each second intermediate reception connector port 72 is arranged on the other side with respect to the dummy port 73.

[0031] The second intermediate connector 70 can be connected to the transceiver 100. For this reason, each second intermediate transmission connector port 71 can be connected to each transmission port 101 of the transceiver 100, and each second intermediate reception connector port 72 can be connected to each reception port 102 of the transceiver 100. FIG. 1 shows a state in which each second intermediate transmission connector port 71 is connected to each transmission port 101 and each second intermediate reception connector port 72 is connected to each reception port 102. In this state, each second intermediate transmission connector port 71 optically couples the core of each second transmission optical fiber 61 and the transmission port 101 of the transceiver 100. In addition, each second intermediate reception connector port 72 optically couples the core of each second reception optical fiber 62 and the reception port 102 of the transceiver 100.

[0032] Therefore, the optical signal transmitted from the transmission port 101 of the transceiver 100 propagates to the transmission core 11 of the multi-core fiber 10 via the second transmission optical fiber 61, the first transmission optical fiber 21, and the fan-in / fan-out device 30. Also, the optical signal propagating through the reception core 12 of the multi-core fiber 10 exits from the reception core 12 and is received at the reception port 102 of the transceiver 100 via the fan-in / fan-out device 30, the first reception optical fiber 22, and the second reception optical fiber 62.

[0033] As described above, the optical input / output device 1 of the present embodiment includes at least one multi-core fiber 10 including at least one transmission core 11 and at least one reception core 12, the same number of first transmission optical fibers 21 as the total number of the transmission cores 11 of all the multi-core fibers 10, the same number of first reception optical fibers 22 as the total number of the reception cores 12 of all the multi-core fibers 10, a fan-in / fan-out device 30 that optically couples each core at one end of each first transmission optical fiber 21 to each transmission core 11, and optically couples each core at one end of each first reception optical fiber 22 to each reception core 12, the same number of transmission connector ports 41 as the number of the first transmission optical fibers 21 that are connected to the other ends of the respective first transmission optical fibers 21 and can optically couple the cores of the respective first transmission optical fibers 21 to the transmission port 101 of the transceiver 100, and the same number of reception connector ports 42 as the number of the first reception optical fibers 22 that are connected to the other ends of the respective first reception optical fibers 22 and can optically couple the cores of the respective first reception optical fibers 22 to the reception port 102 of the transceiver 100.

[0034] According to such an optical input / output device 1, for all the transmission cores 11 in the multi-core fiber 10, the optical signal transmitted from the transmission port 101 of the transceiver 100 propagates through the first optical fiber 21 for transmission, and for the reception core 12, the optical signal received at the reception port 102 of the transceiver 100 propagates through the first optical fiber 22 for reception. Therefore, light propagates in the opposite direction between the transmission core 11 and the reception core 12 in the multi-core fiber 10. Thus, even if crosstalk occurs between the transmission core 11 and the reception core 12, the light that crosstalks from the transmission core 11 to the reception core 12 is not received by the transceiver 100, and the light that crosstalks from the reception core 12 to the transmission core 11 does not propagate to the transmission destination. Therefore, according to the optical input / output device 1 of the present invention, crosstalk that affects communication can be reduced.

[0035] Also, in the multi-core fiber 10 of the present embodiment, the core pair that are adjacent to each other at the shortest distance is a transmission / reception core pair in which one is the transmission core 11 and the other is the reception core 12. Crosstalk tends to increase as the distance between the cores decreases. Therefore, since the core pair that are adjacent to each other at the shortest distance is this transmission / reception core pair, compared with the case where all the core pairs that are adjacent to each other at the shortest distance are core pairs of transmission cores 11 or core pairs of reception cores 12, crosstalk that affects communication can be reduced. In the present embodiment, in each multi-core fiber 10, all the core pairs that are adjacent to each other at the shortest distance are transmission / reception core pairs.

[0036] In addition, the optical input / output device 1 of the present embodiment includes a plurality of multi-core fibers 10. Cores of respective first optical fibers 21 for transmission connected to a pair of adjacent transmission connector ports 41 are optically coupled to transmission cores 11 of different multi-core fibers 10, respectively. Cores of respective first optical fibers 22 for reception connected to a pair of adjacent reception connector ports 42 are optically coupled to reception cores 12 of different multi-core fibers 10, respectively. The first optical fibers 21 for transmission connected to a pair of adjacent transmission connector ports 41 and the first optical fibers 22 for reception connected to a pair of adjacent reception connector ports 42 tend to be optically coupled to a pair of adjacent transmission ports 101 and a pair of adjacent reception ports 102 in the transceiver 100, respectively. By the way, in the transceiver 100, generally, crosstalk easily occurs between lights emitted from adjacent transmission ports 101 or between electrical signals corresponding to these lights, and crosstalk easily occurs between lights emitted from adjacent reception ports 102 or between electrical signals obtained by converting these lights. However, even when such crosstalk occurs, due to such a configuration, crosstalk between respective optical signals propagating through cores of a pair of first optical fibers 21 for transmission in which crosstalk has occurred in the transceiver 100 is suppressed in the multi-core fiber 10, and crosstalk between respective optical signals propagating through cores of a pair of first optical fibers 22 for reception in which crosstalk has occurred in the transceiver 100 is suppressed in the multi-core fiber 10. Therefore, compared with a case where a pair of first optical fibers 21 for transmission connected to a pair of adjacent connector ports are coupled to the transmission core 11 of the same multi-core fiber 10 or a case where a pair of first optical fibers 22 for reception connected to a pair of adjacent connector ports are coupled to the reception core 12 of the same multi-core fiber 10, crosstalk affecting communication can be reduced.

[0037] Also, in the optical input / output device 1 of the present embodiment, all of the multi-core fibers 10 are longer than their respective first transmission optical fibers 21 and their respective first reception optical fibers 22. In the multi-core fiber 10, since it is difficult for a difference to occur in the length of the cores arranged therein, skew is less likely to occur. However, in the first transmission optical fiber 21 and the first reception optical fiber 22, a difference is likely to occur in the length of each core, and skew is likely to occur. Therefore, when all of the multi-core fibers 10 are longer than their respective first transmission optical fibers 21 and their respective first reception optical fibers 22 as in the present embodiment, the ratio of the single-core fiber transmission path can be reduced, and skew can be suppressed as compared with the case where all of the multi-core fibers 10 are shorter than their respective first transmission optical fibers 21 and their respective first reception optical fibers 22. Note that if the length of all of the multi-core fibers 10 in the housing 2 is longer than their respective first transmission optical fibers 21 and their respective first reception optical fibers 22 in the housing 2, skew in the housing 2 can be suppressed.

[0038] In addition, for the optical input / output device 1 of the present embodiment, the light confinement power of each of the first transmission optical fiber 21 and the first reception optical fiber 22 is greater than the light confinement power of each of the second transmission optical fiber 61 and the second reception optical fiber 62. Alternatively, each of the first transmission optical fiber 21 and the first reception optical fiber 22 has a trench layer, and each of the second transmission optical fiber 61 and the second reception optical fiber 62 does not have a trench layer. Further, the outer diameter of the cladding of each of the second transmission optical fiber 61 and the second reception optical fiber 62 is larger than the outer diameter of the cladding of each of the first transmission optical fiber 21 and the first reception optical fiber 22. Therefore, as described above, the microbend loss of the second transmission optical fiber 61 and the second transmission optical fiber 61 tends to be smaller than the microbend loss of the first transmission optical fiber 21 and the first reception optical fiber 22, and the bending breakage probability of the first transmission optical fiber 21 and the first reception optical fiber 22 tends to be smaller than that of the second transmission optical fiber 61 and the second transmission optical fiber 61. The first transmission optical fiber 21 and the first reception optical fiber 22 of the optical input / output device 1, the fan-in fan-out device 30, and at least a part of the multi-core fiber 10 tend to be housed in the housing 2 as in the present embodiment. For this reason, since the first transmission optical fiber 21 and the first reception optical fiber 22 are routed within a limited space, the first transmission optical fiber 21 and the first reception optical fiber 22 arranged in the housing 2 tend to be bent with a smaller bending radius than the second transmission optical fiber 61 and the second reception optical fiber 62 of the patch cord 3 arranged outside the housing 2. Therefore, by the fact that the light confinement power of each of the first transmission optical fiber 21 and the first reception optical fiber 22 is greater than the light confinement power of each of the second transmission optical fiber 61 and the second reception optical fiber 62, the bending loss of light in the first transmission optical fiber 21 and the first reception optical fiber 22 can be suppressed. Also, because of such a relationship of the light confinement power, as described above, the refractive index of each core of the second transmission optical fiber 61 and the second reception optical fiber 62 can be made smaller than the refractive index of each core of the first transmission optical fiber 21 and the first reception optical fiber 22.In this case, the amount of dopant for increasing the refractive index added to the core of each of the second transmission optical fiber 61 and the second reception optical fiber 62 can be suppressed, and the loss due to Rayleigh scattering in the second transmission optical fiber 61 and the second reception optical fiber 62, which tend to be longer than the first transmission optical fiber 21 and the first reception optical fiber 22, can be suppressed. Further, even when the first transmission optical fiber 21 and the first reception optical fiber 22 have a trench layer, the bending loss of light in the first transmission optical fiber 21 and the first reception optical fiber 22 can be suppressed. Further, although the optical fiber having a trench layer can suppress the bending loss as described above, for long-distance light transmission, the transmission loss tends to be larger than that of the optical fiber having no trench layer. Therefore, as described above, since the second transmission optical fiber 61 and the second reception optical fiber 62, which tend to be longer than the first transmission optical fiber 21 and the first reception optical fiber 22, do not have a trench layer, the light transmission loss in the second transmission optical fiber 61 and the second reception optical fiber 62 can be suppressed, and the light loss in the optical input / output device 1 can be suppressed. Further, as described above, since the bending breakage coefficients of the first transmission optical fiber 21 and the first reception optical fiber 22 can be made smaller than the breakage coefficients of the second transmission optical fiber 61 and the second reception optical fiber 62, even if the first transmission optical fiber 21 and the first reception optical fiber 22 are bent at a larger curvature than the second transmission optical fiber 61 and the second reception optical fiber 62, breakage of the first transmission optical fiber 21 and the first reception optical fiber 22 can be suppressed.

[0039] As described above, the present invention has been described by taking the above-described embodiment as an example, but the present invention is not limited to the above-described embodiment.

[0040] For example, in the above-described embodiment, the optical input / output device 1 including two multi-core fibers 10 has been described as an example. However, the optical input / output device of the present invention may include three or more multi-core fibers, or may include only one multi-core fiber.

[0041] Also, an example in which each multi-core fiber 10 includes two transmission cores 11 and two reception cores 12 has been described. However, as long as the multi-core fiber includes at least one transmission core 11 and at least one reception core, the number of transmission cores 11 and reception cores 12 may be one or three or more, and the number of transmission cores 11 and the number of reception cores 12 may be different from each other. Note that since generally in the transceiver 100, the transmission port 101 and the reception port 102 are provided in a one-to-one manner, it is preferable that the total number of transmission cores 11 of all the multi-core fibers 10 is equal to the total number of reception cores 12.

[0042] Also, in the above embodiment, an example has been shown in which, in each multi-core fiber 10, the core pair that are adjacent to each other at the shortest distance is a transmission / reception core pair in which one is a transmission core 11 and the other is a reception core 12. However, for example, at least a part of the core pairs that are adjacent to each other at the shortest distance may be a core pair of transmission cores 11 or a core pair of reception cores 12. As such an example, for example, a multi-core fiber in which odd-numbered cores are arranged in an annular shape and only one pair of each of the core pairs that are adjacent to each other at the shortest distance is a core pair of transmission cores 11 or a core pair of reception cores 12 can be cited. Also, in only some of the multi-core fibers, at least a part of the core pairs that are adjacent to each other at the shortest distance may be transmission / reception core pairs. Also, the example in which all the core pairs that are adjacent to each other at the shortest distance are transmission / reception core pairs is not limited to the above embodiment. For example, there may be three or more transmission cores 11 and three or more reception cores 12, and the transmission cores 11 and the reception cores 12 may be alternately arranged in an annular shape.

[0043] Also, the arrangement of the cores in each multi-core fiber 10 is not limited to the above embodiment. For example, a plurality of cores may be arranged linearly. In this case, the transmission cores 11 and the reception cores 12 may be alternately arranged so that all the core pairs that are adjacent to each other at the shortest distance become transmission / reception core pairs.

[0044] Further, the multi-core fiber 10 in the optical input / output device 1 of the present invention may have a central core disposed at the center of the cladding 13 and a plurality of outer peripheral cores disposed so as to surround the central core. In this case, the central core is a transmission core 11 or a reception core 12, and the plurality of outer peripheral cores include at least one transmission core 11 and at least one reception core 12. FIG. 2 is a diagram showing an example of optical coupling of the multi-core fiber 10, the first transmission optical fiber 21, the first reception optical fiber 22, and the transceiver connector 40 when such a multi-core fiber 10 is used. Regarding the configuration similar to the above embodiment, the same reference numerals as those in the above embodiment are given, and the description thereof is omitted unless otherwise particularly described. In FIG. 2, in order to avoid complication of the figure, the fan-in / fan-out device 30 is omitted, and only the multi-core fiber 10, the first transmission optical fiber 21, the first reception optical fiber 22, and the transceiver connector 40 are shown. Therefore, FIG. 2 does not mean that the first reception optical fiber 22 and the transceiver connector 40 are directly connected to the multi-core fiber 10.

[0045] As shown in FIG. 2, in this example, the optical input / output device 1 includes a plurality of multi-core fibers 10. The number of multi-core fibers 10 in this example is, for example, 8. However, in FIG. 2, in order to avoid complication of the figure, some of the multi-core fibers 10 are indicated by dots. Among each of the multi-core fibers 10, in half of the multi-core fibers 10, the central core disposed at the center of the cladding 13 is the transmission core 11, and in the other half of the multi-core fibers 10, the central core disposed at the center of the cladding 13 is the reception core 12. In each of the multi-core fibers 10, around this central core, two transmission cores 11 are disposed diagonally as a part of the outer peripheral cores, and two reception cores 12 are disposed diagonally as the other part of the outer peripheral cores. Therefore, when only looking at the outer peripheral cores, the transmission core 11 and the reception core 12 are adjacent to each other.

[0046] Also, in this example, the transmission / reception connector 40 is composed of a plurality of partial connectors 45. Each partial connector 45 has two or more of the connector ports among all the connector ports of the transmission / reception connector 40. If the number of the multi-core fibers 10 is 8 as described above, the transmission / reception connector 40 has, for example, five 8-port partial connectors 45. In the example shown in FIG. 2, each partial connector 45 has the same number of transmission connector ports 41 and reception connector ports 42, and the total number of the connector ports of the transmission connector ports 41 and the reception connector ports 42 is the same as the total number of the transmission core 11 and the reception core 12 of the multi-core fiber 10. However, in FIG. 2, some of the partial connectors 45 are indicated by dots in order to avoid complication of the figure.

[0047] The first transmission optical fiber 21 optically coupled to the transmission core 11 which is the central core of half of the multi-core fibers 10 is connected to the transmission connector port 41 of a specific partial connector 45, and the first reception optical fiber 22 optically coupled to the reception core 12 which is the central core of the other half of the multi-core fibers 10 is connected to the reception connector port 42 of the specific partial connector 45. In FIG. 2, this specific partial connector 45 is the partial connector 45 at the right end. Also, each of the first transmission optical fibers 21 connected to each of the transmission cores 11 which are the outer peripheral cores of each multi-core fiber 10 is connected to the transmission connector port 41 of the partial connectors 45 other than the specific partial connector 45, and each of the first reception optical fibers 22 connected to each of the reception cores 12 which are the outer peripheral cores of each multi-core fiber 10 is connected to the reception connector port 42 of the partial connectors 45 other than the specific partial connector 45. In the example of FIG. 2, some of the connection relationships are omitted, but each of the first transmission optical fibers 21 connected to the transmission core 11 which is the outer peripheral core of one multi-core fiber 10 and each of the first reception optical fibers 22 connected to the reception core 12 which is the outer peripheral core are connected to the transmission connector port 41 and the reception connector port 42 of the same partial connector 45.

[0048] Also, although not particularly shown, in the modification of FIG. 2, the central core of each multi-core fiber 10 may be a transmission core 11. In this case, a specific partial connector 45 has the same number of transmission connector ports 41 as the number of multi-core fibers 10, and the first transmission optical fibers 21 connected to the respective transmission connector ports 41 of the specific partial connector 45 are optically coupled to the central cores of the respective multi-core fibers 10. Alternatively, the central core of each multi-core fiber 10 may be a reception core 12. In this case, a specific partial connector 45 has the same number of reception connector ports 42 as the number of multi-core fibers 10, and the first reception optical fibers 22 connected to the respective reception connector ports 42 of the specific partial connector 45 are optically coupled to the central cores of the respective multi-core fibers 10.

[0049] In the example of FIG. 2 and its modification, the first transmission optical fibers 21 or the first reception optical fibers 22 optically coupled to the respective central cores of the respective multi-core fibers 10 are connected to the connector ports of a specific partial connector 45, and the first transmission optical fibers 21 connected to the respective transmission cores 11 which are outer peripheral cores and the first reception optical fibers 22 connected to the respective reception cores 12 which are outer peripheral cores are connected to the connector ports of a partial connector 45 other than the specific partial connector 45. Generally, the light propagating through the central core is affected by crosstalk from each of the surrounding cores arranged around it. Therefore, by collecting and connecting the single-core fibers having cores optically coupled to the central core as described above to the specific partial connector 45, it becomes easier to collect and connect the light with a large crosstalk effect from the specific partial connector 45 to one transceiver. For this reason, it becomes easier to appropriately process crosstalk in the transceiver.

[0050] Also, generally, when a multi-core fiber is connected, the outer peripheral cores are affected by the centering deviation in the rotational direction around the axis of the fiber, and thus tend to have a larger connection loss than the central core. Further, the influence of this centering deviation in the rotational direction is generally the same among the outer peripheral cores arranged at an equal distance from the center of the multi-core fiber. Therefore, as in the example of FIG. 2, each optical fiber connected to the outer peripheral core of one multi-core fiber 10 is connected to the connector ports of the same partial connector 45, thereby suppressing the variation between the connector ports of the connection loss in each partial connector 45. For this reason, in the transceiver 100 to which the partial connector 45 is connected, it is possible to facilitate the processing for the connection loss.

[0051] Also, in the above embodiment, the cores of the respective first transmission optical fibers 21 connected to the pair of adjacent transmission connector ports 41 are optically coupled to the transmission cores 11 of different multi-core fibers 10, respectively, and the cores of the respective first reception optical fibers 22 connected to the pair of adjacent reception connector ports 42 are optically coupled to the reception cores 12 of different multi-core fibers 10, respectively, which has been described as an example. However, the cores of the respective first transmission optical fibers 21 connected to the pair of adjacent transmission connector ports 41 may be optically coupled to the transmission core 11 of one multi-core fiber 10, respectively, and the cores of the respective first reception optical fibers 22 connected to the pair of adjacent reception connector ports 42 may be optically coupled to the reception core 12 of one multi-core fiber 10, respectively.

[0052] FIG. 3 is a diagram showing an example different from the embodiment of the optical coupling of the multi-core fiber 10, the first transmission optical fiber 21, the first reception optical fiber 22, and the transmission / reception connector 40 when such a multi-core fiber 10 is used. As shown in FIG. 3, in the multi-core fiber 10 of this example, the transmission core 11 and the reception core 12 are alternately arranged. Therefore, the core pair adjacent to each other at the shortest distance is the above-mentioned transmission / reception core pair. And the first transmission optical fiber 21 connected to the adjacent transmission connector ports 41 of the transmission / reception connector 40 is optically coupled to a pair of transmission cores 11 other than the core pair adjacent to each other at the shortest distance in the multi-core fiber 10, respectively, and the first reception optical fiber 22 connected to the adjacent reception connector ports 42 is optically coupled to a pair of reception cores 12 other than the core pair adjacent to each other at the shortest distance in the multi-core fiber 10, respectively. Further, in the example of FIG. 3, a reception core 12 is located between a pair of transmission cores 11 in the multi-core fiber 10 where the cores of the respective first transmission optical fibers 21 connected to the adjacent pair of transmission connector ports 41 are optically coupled, and a transmission core 11 is located between a pair of reception cores 12 in the multi-core fiber 10 where the cores of the respective first reception optical fibers 22 connected to the adjacent pair of reception connector ports 42 are optically coupled.

[0053] Note that, although different from FIG. 3, the first transmission optical fiber 21 connected to the adjacent transmission connector ports 41 of the transmission / reception connector 40 may be optically coupled to a pair of adjacent transmission cores 11 via the reception core 12 of the multi-core fiber 10, respectively, and the first reception optical fiber 22 connected to the adjacent reception connector ports 42 may be optically coupled to a pair of adjacent reception cores 12 via the transmission core 11 of the multi-core fiber 10, respectively.

[0054] Thus configured, even when crosstalk occurs between a pair of adjacent connector ports in the transceiver connector 40, between the first transmission optical fibers 21 or between the first reception optical fibers 22, the cores of the pair of first transmission optical fibers 21 where the above crosstalk has occurred are coupled to a pair of transmission cores 11 adjacent to each other at the shortest distance in the multi-core fiber 10, or the cores of the pair of first reception optical fibers 22 where the above crosstalk has occurred are coupled to a pair of reception cores 12 adjacent to each other at the shortest distance in the multi-core fiber 10. Compared with such cases, crosstalk in the multi-core fiber 10 can be suppressed. Further, in this example, a reception core 12 is located between a pair of transmission cores 11 to which the cores of the respective first transmission optical fibers 21 connected to a pair of adjacent transmission connector ports 41 are optically coupled, and a transmission core 11 is located between a pair of reception cores 12 to which the cores of the respective first reception optical fibers 22 connected to a pair of adjacent reception connector ports 42 are optically coupled. Therefore, compared with the case where the reception core 12 is not located between the above pair of transmission cores 11 or the case where the transmission core 11 is not located between the above pair of reception cores 12, crosstalk affecting communication can be suppressed.

[0055] In addition, in the present invention, the patch code 3 is not essential, and the transmission connector port 41 and the reception connector port 42 of the transceiver connector 40 and the transmission port 101 and the reception port 102 of the transceiver 100 may be connected by other means respectively. Also, the transceiver connector 40 is not essential. For example, the first transmission optical fiber 21 and the second transmission optical fiber 61 may be fusion-connected to each other, and the first reception optical fiber 22 and the second reception optical fiber 62 may be fusion-connected to each other. In this case, the fusion connection part may be located inside the housing 2 or outside the housing 2. From the viewpoint of suppressing breakage due to trauma, it is preferably located inside the housing 2. Also, the second transmission optical fiber 61 may be connected to the transmission port 101 of the transceiver 100, and the second reception optical fiber 62 may be connected to the reception port 102 of the transceiver 100. Also, the first transmission optical fiber 21 may be provided in a state where it can be fusion-connected to the second transmission optical fiber 61 without being directly fusion-connected to the second transmission optical fiber 61, and the first reception optical fiber 22 may be provided in a state where it can be fusion-connected to the second reception optical fiber 62 without being fusion-connected to the second reception optical fiber 62. When the housing 2 is provided, the fusion connection point between the first transmission optical fiber 21 and the second transmission optical fiber 61 may be inside the housing 2, or the fusion connection point between the first reception optical fiber 22 and the second reception optical fiber 62 may be outside the housing 2. In any case, at least a part of the first transmission optical fiber 21 is accommodated inside the housing 2, and at least a part of the first reception optical fiber 22 is arranged outside the housing 2. Or, at least a part of the second transmission optical fiber 61 is accommodated inside the housing 2, and at least a part of the second reception optical fiber 62 is arranged outside the housing 2. Also, the transceiver connector 40 may be located outside the housing 2. In this case, the degree of freedom in the arrangement position of the transceiver connector 40 can be increased. Also, when the transceiver connector 40 and the first intermediate connector 50 are connected to each other, the degree of freedom in the arrangement positions of the first intermediate connector 50 and the transceiver connector 40 can be increased.Also, in this case, for example, when the distances between the transceiver 100 and the transmission / reception connector 40 and the first intermediate connector 50 are small, the degree of freedom in the operation of reattaching and connecting the first transmission optical fiber 21, the second transmission optical fiber 61, the first reception optical fiber 22, and the second reception optical fiber 62, which are connected between the ports of the first intermediate connector 50 and the ports of the transceiver 100, to other ports of the first intermediate connector 50 or other ports of the transceiver 100 can be increased. Further, the transmission / reception connector 40 may be located outside the housing 2. Also, the transmission / reception connector 40 may be located outside the housing 2, and the fusion connection portion may be located inside or outside the housing 2. Also, a plurality of transmission / reception connectors 40 may be provided. Further, instead of the transmission / reception connector 40, the first transmission optical fiber 21 and the second transmission optical fiber 61 may be connected to each other by an optical fiber holding member such as a mechanical splice element, and the first reception optical fiber 22 and the second reception optical fiber 62 may be connected to each other.

[0056] In the above-described embodiment, the outer diameter of the cladding of each of the second transmission optical fiber 61 and the second reception optical fiber 62 is larger than the outer diameter of the cladding of each of the first transmission optical fiber 21 and the first reception optical fiber 22, and the optical confinement force of each of the first transmission optical fiber 21 and the first reception optical fiber 22 is made larger than the optical confinement force of each of the second transmission optical fiber 61 and the second reception optical fiber 62, but this is not essential. Alternatively, in at least one of the optical fiber pair composed of the first transmission optical fiber 21 and the second transmission optical fiber 61 that are optically coupled to each other, and the optical fiber pair composed of the first reception optical fiber 22 and the second reception optical fiber 62 that are connected to each other, the outer diameter of the cladding of the second transmission optical fiber 61 or the second reception optical fiber 62 may be larger than the outer diameter of the cladding of the first transmission optical fiber 21 or the first reception optical fiber 22, and the optical confinement force of each of the first transmission optical fiber 21 and the first reception optical fiber 22 may be larger than the optical confinement force of each of the second transmission optical fiber 61 and the second reception optical fiber 62. That is, in at least one of the plurality of single-core fiber pairs composed of a plurality of first single-core fibers each including the first transmission optical fiber 21 and a plurality of second single-core fibers each including the second transmission optical fiber 61 and optically coupled to the respective first single-core fibers, the optical confinement force of the first single-core fiber may be larger than the optical confinement force of the second single-core fiber, and the outer diameter of the cladding of the second single-core fiber may be larger than the outer diameter of the cladding of the first single-core fiber. Similarly, in at least one of such a plurality of single-core fiber pairs, the first single-core fiber may have a trench layer, the second single-core fiber may not have a trench layer, and the outer diameter of the cladding of the second single-core fiber may be larger than the outer diameter of the cladding of the first single-core fiber.

[0057] In the above-described embodiment, an example was described in which a part of each multi-core fiber 10, a fan-in / fan-out device 30, each first transmission optical fiber 21, and each first reception optical fiber 22 are accommodated in the space of the housing 2. However, the housing 2 is not an essential component.

[0058] In addition, the transmission / reception connector 40 is not limited to the above-described form. For example, it may be composed of the same number of single-core transmission connectors as the number of the first transmission optical fibers 21 each having one transmission connector port 41, and the same number of single-core reception connectors as the number of the first reception optical fibers 22 each having one reception connector port 42. Further, for example, if the number of the first transmission optical fibers 21 and the number of the first reception optical fibers 22 are the same, the transmission / reception connector 40 may have one transmission connector port 41 and one reception connector port 42, and may be composed of the same number of dual transmission / reception connectors as the number of the first transmission optical fibers 21.

[0059] As another example of the multi-core fiber 10, there can be mentioned a structure in which a plurality of single-core fibers surrounded by a cladding are bundled with resin.

[0060] In addition, at least a part of the optical fibers, which are the first transmission optical fibers 21 and the first reception optical fibers 22, may be composed of a connector of a plurality of optical fibers. There may be a limit to the fiber length in one optical fiber. Therefore, by forming the first transmission optical fibers 21 and the first reception optical fibers 22 from optical fiber connectors, the first transmission optical fibers 21 and the first reception optical fibers 22 can be made long. In this case, it is preferable that the plurality of optical fibers are connected by fusion. By being connected by fusion, the connection loss can be reduced as compared with the case where a plurality of optical fibers are connected by a connector. Further, at least a part of the optical fibers, which are the second transmission optical fibers 61 and the second reception optical fibers 62, may be composed of a connector of a plurality of optical fibers. Also in this case, the second transmission optical fibers 61 and the second reception optical fibers 62 can be made long. Also in this case, from the viewpoint of reducing the connection loss, it is preferable that the plurality of optical fibers are connected by fusion.

[0061] In addition, in the present embodiment, the first transmission optical fiber 21 and the first reception optical fiber 22 may be bundled together by a single or a plurality of coatings as a ribbon optical fiber, and the second transmission optical fiber 61 and the second reception optical fiber 62 may be bundled together by a single or a plurality of coatings as a ribbon optical fiber. Thereby, the arrangement of the first transmission optical fiber 21 and the first reception optical fiber 22 and the arrangement of the second transmission optical fiber 61 and the second reception optical fiber 62 can be fixed. Therefore, the positional relationship of the end portions in each optical fiber becomes clear, and the connection between the first transmission optical fiber 21 and the second transmission optical fiber 61 and the connection between the first reception optical fiber 22 and the second reception optical fiber 62 can be facilitated. Further, in this case, when the transmission / reception connector 40 is not provided and the first transmission optical fiber 21 and the second transmission optical fiber 61 are fusion-connected to each other, or the first reception optical fiber 22 and the second reception optical fiber 62 are fusion-connected to each other, since the positional relationship of the optical fibers is clear, it is easy to perform the fusion connection. Further, when the first transmission optical fiber 21, the first reception optical fiber 22, the second transmission optical fiber 61, and the second reception optical fiber 62 are composed of an optical fiber connection body in which a plurality of optical fibers are fusion-connected to each other, the optical fibers to be fusion-connected to each other may be included in separate ribbon optical fibers. In this case, since the positional relationship of the plurality of optical fibers respectively included in the separate ribbon optical fibers is clear, when connecting the ribbon optical fibers to each other, it is easy to fusion-connect the plurality of optical fibers to each other to form an optical fiber connection body.

[0062] According to the present invention, an optical input / output device capable of reducing crosstalk that affects communication can be provided, and it can be used, for example, in the field of optical communication and the like.

[0063] (Supplementary Notes) By the way, in a multi-core fiber, since the distance between the cores is small, crosstalk is likely to occur. For this reason, it is desired that an optical signal with reduced crosstalk that affects communication propagates.

[0064] Therefore, an object of the present invention is to provide an optical input / output device capable of reducing crosstalk that affects communication.

[0065] To achieve the above object, the optical input / output device of the present invention includes at least one multi-core fiber including at least one transmission core and at least one reception core, a first single-core fiber for transmission having the same number as the total number of the transmission cores of all the multi-core fibers, a first single-core fiber for reception having the same number as the total number of the reception cores of all the multi-core fibers, a fan-in / fan-out device that optically couples each core at one end of each of the first single-core fibers for transmission to each of the transmission cores and optically couples each core at one end of each of the first single-core fibers for reception to each of the reception cores, and a transmission / reception connector having the same number as the total number of the first single-core fibers for transmission and the first single-core fibers for reception, the transmission / reception connector being connected to the other end of each of the first single-core fibers for transmission and being capable of optically coupling the core of each of the first single-core fibers for transmission to the transmission port of a transceiver, and being connected to the other end of each of the first single-core fibers for reception and being capable of optically coupling the core of each of the first single-core fibers for reception to the reception port of the transceiver.

[0066] According to such an optical input / output device, when the core of each transmission single-core fiber is optically connected to the transmission port of the transceiver, the optical signal transmitted from the transmission port of the transceiver propagates through the transmission single-core fiber to the transmission core in the multi-core fiber. When the core of each reception single-core fiber is optically connected to the reception port of the transceiver, the optical signal received at the reception port of the transceiver propagates through the reception single-core fiber to the reception core. Therefore, light propagates in the opposite direction between the transmission core and the reception core in the multi-core fiber. Accordingly, even when crosstalk occurs between the transmission core and the reception core, the light that crosstalks from the transmission core to the reception core is suppressed from being received by the transceiver, and the light that crosstalks from the reception core to the transmission core is suppressed from propagating to the transceiver at the transmission destination. Therefore, according to the optical input / output device of the present invention, crosstalk that affects communication can be reduced.

[0067] Further, in at least one of the multi-core fibers, it is preferable that at least one of the core pairs adjacent to each other at the shortest distance is a transmission / reception core pair in which one is the transmission core and the other is the reception core.

[0068] Crosstalk tends to increase as the core-to-core distance decreases. Therefore, by having the core pairs adjacent to each other at the shortest distance be the above-described transmission / reception core pairs, crosstalk that affects communication can be reduced as compared with the case where all of the core pairs adjacent to each other at the shortest distance are core pairs of transmission cores or core pairs of reception cores.

[0069] In this case, in at least one of the multi-core fibers, it is preferable that all of the core pairs adjacent to each other at the shortest distance are the transmission / reception core pairs.

[0070] By doing so, crosstalk that affects communication can be further reduced.

[0071] In addition, the optical input / output device according to any one of the above preferably includes a plurality of the multi-core fibers, and the cores of the respective first single-core fibers for transmission connected to a pair of the connector ports adjacent to each other are optically coupled to the transmission cores of different multi-core fibers, respectively, and the cores of the respective first single-core fibers for reception connected to a pair of the connector ports adjacent to each other are optically coupled to the reception cores of different multi-core fibers, respectively.

[0072] The first optical fiber for transmission connected to a pair of adjacent transmission connector ports and the first optical fiber for reception connected to a pair of adjacent reception connector ports tend to be optically coupled to a pair of adjacent transmission ports and a pair of adjacent reception ports in the transceiver, respectively. By the way, in a transceiver, generally, crosstalk easily occurs between lights emitted from adjacent transmission ports or between these lights and the electrical signals that become these lights, and crosstalk easily occurs between lights emitted from adjacent reception ports or between the electrical signals into which these lights are converted. However, even when such crosstalk occurs, the cores of a pair of single-core fibers for the first transmission through which the crosstalk-generated light propagates in the transceiver are coupled to the transmission cores of different multi-core fibers, and the cores of a pair of single-core fibers for the first reception through which the crosstalk-generated light propagates in the transceiver are coupled to the reception cores of different multi-core fibers. Therefore, crosstalk between the respective optical signals propagating through the cores of the pair of single-core fibers for the first transmission where the above crosstalk occurs is suppressed in the multi-core fiber, and crosstalk between the respective optical signals propagating through the cores of the pair of single-core fibers for the first reception where the above crosstalk occurs is suppressed in the multi-core fiber. Therefore, compared with the case where a pair of single-core fibers for the first transmission connected to a pair of adjacent connector ports are coupled to the transmission core of the same multi-core fiber or the case where a pair of single-core fibers for the first reception connected to a pair of adjacent connector ports are coupled to the reception core of the same multi-core fiber, crosstalk that affects communication can be reduced.

[0073] Alternatively, the cores of the respective first single-core fibers for transmission connected to a pair of the connector ports adjacent to each other are optically coupled to a pair of the transmission cores other than a pair of cores adjacent to each other at the shortest distance in one of the multi-core fibers, and the cores of the respective first single-core fibers for reception connected to a pair of the connector ports adjacent to each other are optically coupled to a pair of the reception cores other than a pair of cores adjacent to each other at the shortest distance in one of the multi-core fibers, which is also preferable.

[0074] Even when crosstalk occurs in the transceiver as described above, the cores of these pair of first single-core fibers for transmission are coupled to a pair of transmission cores that are not adjacent to each other at the shortest distance in the multi-core fiber, and the cores of these pair of first single-core fibers for reception are coupled to a pair of reception cores that are not adjacent to each other at the shortest distance in the multi-core fiber. Therefore, compared with the case where the cores of the pair of first single-core fibers for transmission where the above crosstalk occurs are coupled to a pair of transmission cores adjacent to each other at the shortest distance in the multi-core fiber, or the case where the cores of the pair of first single-core fibers for reception where the above crosstalk occurs are coupled to a pair of reception cores adjacent to each other at the shortest distance in the multi-core fiber, crosstalk in the multi-core fiber can be suppressed.

[0075] In this case, it is preferable that a reception core is located between a pair of the transmission cores in the multi-core fiber to which the cores of the respective first single-core fibers for transmission connected to a pair of the connector ports adjacent to each other are optically coupled, and a transmission core is located between a pair of the reception cores in the multi-core fiber to which the cores of the respective first single-core fibers for reception connected to a pair of the connector ports adjacent to each other are optically coupled.

[0076] When a receiving core is not located between the pair of transmitting cores, or when a transmitting core is not located between the pair of receiving cores, crosstalk that affects communication can be suppressed as compared with the case where this is not so.

[0077] Further, in the optical input / output device according to any one of the above, a central core disposed at the center of the cladding is the transmitting core or the receiving core, and a plurality of the multi-core fibers are provided in which at least one of the transmitting cores and at least one of the receiving cores are disposed around the central core. The transmission / reception connector is composed of a plurality of partial connectors each having two or more of the connector ports among all the connector ports. Each of the first single-core fibers for transmission or the first single-core fibers for reception optically coupled to the central core of each of the multi-core fibers is connected to the connector port of a specific one of the partial connectors, and each of the first single-core fibers for transmission connected to each of the transmitting cores disposed around the central core of each of the multi-core fibers and each of the first single-core fibers for reception connected to each of the receiving cores disposed around the central core of each of the multi-core fibers are preferably connected to the connector ports of the partial connectors other than the specific partial connector.

[0078] Light propagating through the central core disposed at the center of the cladding is affected by crosstalk from each of the surrounding cores disposed around it. Therefore, by connecting the single-core fiber having a core optically coupled to the central core as described above to a specific partial connector, when the specific partial connector and the transceiver are optically connected, light with a large crosstalk effect can be easily collected from the specific partial connector and connected to one transceiver. For this reason, it becomes easier to appropriately process crosstalk with the transceiver.

[0079] Further, it is preferable that all of the multi-core fibers are longer than each of the first single-core fibers for transmission and each of the first single-core fibers for reception.

[0080] In optical communication, skew, which causes a difference in the transmission time of light propagating through each core, may be a problem. In a multi-core fiber, since it is difficult for a difference to occur in the lengths of the cores arranged therein, the above-mentioned skew is less likely to occur. On the other hand, in a plurality of single-core fibers, a difference is likely to occur in the lengths of the respective cores, and the above-mentioned skew is likely to occur. Therefore, since all the multi-core fibers are longer than their respective first single-core fibers for transmission and their respective first single-core fibers for reception as described above, the ratio of the transmission paths of the single-core fibers can be reduced. For this reason, skew can be suppressed as compared with the case where all the multi-core fibers are shorter than their respective first single-core fibers for transmission and their respective first single-core fibers for reception.

[0081] In addition, the optical input / output device according to any one of the above includes a housing that houses at least a part of each of the first single-core fibers for transmission and each of the first single-core fibers for reception, and the same number as the first single-core fibers for transmission. A second single-core fiber for transmission having a core that is optically coupled to the core at the other end of each of the first single-core fibers for transmission and is optically coupled to the transmission port of the transceiver, and at least a part of which is disposed outside the housing; and the same number as the first single-core fibers for reception, having a core that is optically coupled to the core at the other end of each of the first single-core fibers for reception and is optically coupled to the reception port of the transceiver, and at least a part of which is disposed outside the housing. And a plurality of first single-core fibers each composed of each of the first single-core fibers for transmission and each of the first single-core fibers for reception, and a plurality of second single-core fibers each composed of each of the second single-core fibers for transmission and each of the second single-core fibers for reception and optically coupled to each of the first single-core fibers. Assume a plurality of single-core fiber pairs. In this case, in at least one of the plurality of single-core fiber pairs, the light confinement power of the first single-core fiber is preferably greater than the light confinement power of the second single-core fiber, and the outer diameter of the cladding of the second single-core fiber is preferably greater than the outer diameter of the cladding of the first single-core fiber. Alternatively, in this case, the first single-core fiber has the core, a cladding that surrounds the core and has a refractive index lower than that of the core, and a trench layer that surrounds the core and is surrounded by the cladding and has a refractive index lower than that of the cladding. The second single-core fiber has the core, a cladding that surrounds the core and has a refractive index lower than that of the core, and does not have a trench layer that surrounds the core and is surrounded by the cladding and has a refractive index lower than that of the cladding. The outer diameter of the cladding of the second single-core fiber is preferably greater than the outer diameter of the cladding of the first single-core fiber.

[0082] In this case, each single-core fiber pair is composed of a first single-core fiber for transmission and a second single-core fiber for transmission, or is composed of a first single-core fiber for reception and a second single-core fiber for reception. Since the first single-core fiber for transmission and the first single-core fiber for reception are routed within the limited space in the housing, the first single-core fiber for transmission and the first single-core fiber for reception arranged in the housing tend to be bent with a larger curvature than the second single-core fiber for transmission and the second single-core fiber for reception arranged outside the housing. Therefore, by making the light confinement force of the first single-core fiber assumed as above larger than the light confinement force of the second single-core fiber optically coupled to the first single-core fiber, the bending loss of light in the first single-core fiber can be suppressed. Also, when the light confinement force of the second single-core fiber is smaller than the light confinement force of the first single-core fiber, the refractive index of the core of the second single-core fiber can be made smaller than the refractive index of the core of the first single-core fiber. In this case, the amount of dopant added to the core of the second single-core fiber to increase the refractive index can be suppressed, and in the second single-core fiber, the loss due to Rayleigh scattering can be suppressed more than in the first single-core fiber. Incidentally, the second single-core fiber arranged outside the housing is generally connected to a transceiver arranged at a position away from the input / output device, and thus tends to be longer than the first single-core fiber. Therefore, by being able to suppress the loss due to Rayleigh scattering in the second single-core fiber more than in the first single-core fiber, the light loss in the optical input / output device can be suppressed.

[0083] Also, even when the first single-core fiber has a trench layer, the bending loss of light in the first single-core fiber can be suppressed. Further, although an optical fiber having a trench layer can suppress bending loss as described above, for long-distance light transmission, the transmission loss tends to be larger than that of an optical fiber having no trench layer. Therefore, as described above, since the second single-core fiber, which tends to be longer than the first single-core fiber, has no trench layer, the transmission loss of light in the second single-core fiber can be suppressed, and the light loss of the optical input / output device can be suppressed.

[0084] Also, by making the outer diameter of the cladding of the first single-core fiber smaller than the outer diameter of the cladding of the second single-core fiber, the breaking coefficient of the first single-core fiber can be made smaller than the breaking coefficient of the second single-core fiber. Therefore, even if the first single-core fiber is bent at a larger curvature than the second single-core fiber, breakage of the first single-core fiber can be suppressed.

[0085] Further, the core of each of the first single-core fibers for transmission may be optically coupled to the transmission port of the transceiver, and the core of each of the first single-core fibers for reception may be optically coupled to the reception port of the transceiver.

Claims

1. a plurality of multi-core fibers including at least one transmitting core and at least one receiving core; a first transmitting single-core fiber having the same number as the total number of the transmitting cores of all the multi-core fibers; a first receiving single-core fiber having the same number as the total number of the receiving cores of all the multi-core fibers; a fan-in fan-out device having the same number as all the multi-core fibers, the fan-in fan-out device corresponding to each multi-core fiber optically coupling each core at one end of the first transmitting single-core fibers, the number of which is the same as the transmitting cores of the multi-core fiber, to each of the transmitting cores of the multi-core fiber, and optically coupling each core at one end of the first receiving single-core fibers, the number of which is the same as the receiving cores of the multi-core fiber, to each of the receiving cores of the multi-core fiber.

1. An optical input / output device comprising:

2. a second transmitting single-core fiber, the number of which is the same as that of the first transmitting single-core fibers, the second transmitting single-core fibers being connected to the other end of each of the first transmitting single-core fibers and optically coupling a core of each of the first transmitting single-core fibers and a transmitting port of a transceiver; and a second receiving single-core fiber, the number of which is the same as the first receiving single-core fibers, the second receiving single-core fibers being connected to the other end of each of the first receiving single-core fibers and optically coupling a core of each of the first receiving single-core fibers to a receiving port of the transceiver, The first transmitting single-core fiber and the first receiving single-core fiber are bundled together as a ribbon core wire, and the second transmitting single-core fiber and the second receiving single-core fiber are bundled together as a ribbon core wire.

2. The optical input / output device according to claim 1.

3. a housing in which at least a portion of each of the first transmitting single-core fibers and each of the first receiving single-core fibers is housed; In at least one of a plurality of single-core fiber pairs including a plurality of first single-core fibers each consisting of the first transmitting single-core fiber and the first receiving single-core fiber, and a plurality of second single-core fibers each consisting of the second transmitting single-core fiber and the second receiving single-core fiber and optically coupled to the first single-core fiber, a light confinement force of the first single-core fiber is greater than a light confinement force of the second single-core fiber, and an outer diameter of a clad of the second single-core fiber is greater than an outer diameter of a clad of the first single-core fiber.

3. The optical input / output device according to claim 2.

4. In at least one of a plurality of single-core fiber pairs consisting of a plurality of first single-core fibers each consisting of the first transmitting single-core fiber and the first receiving single-core fiber, and a plurality of second single-core fibers each consisting of the second transmitting single-core fiber and the second receiving single-core fiber and optically coupled to the first single-core fibers, the first single-core fiber has the core, a cladding surrounding the core and having a lower refractive index than the core, and a trench layer surrounding the core, surrounded by the cladding, and having a lower refractive index than the cladding, the second single-core fiber has the core, a cladding surrounding the core and having a lower refractive index than the core, does not have a trench layer surrounding the core, surrounded by the cladding, and having a lower refractive index than the cladding, and an outer diameter of the cladding of the second single-core fiber is larger than an outer diameter of the cladding of the first single-core fiber.

3. The optical input / output device according to claim 2.

5. a single transmitting / receiving connector that is connected to the other end of each of the first transmitting single-core fibers and is capable of optically coupling a core of each of the first transmitting single-core fibers with a transmitting port of a transceiver, and that has connector ports that are connected to the other end of each of the first receiving single-core fibers and are capable of optically coupling a core of each of the first receiving single-core fibers with a receiving port of the transceiver, the number of which is the same as the total number of the first transmitting single-core fibers and the first receiving single-core fibers; a housing in which a portion of each of the multi-core fibers, the fan-in fan-out devices in the same number as the number of the multi-core fibers, and each of the first transmitting single-core fibers and the first receiving single-core fibers are accommodated; The connector port of the transmitting / receiving connector is A single-core transmitting connector and a single-core receiving connector fixed to the housing, the single-core transmitting connector having one transmitting connector port and the number of single-core transmitting connectors being the same as the first transmitting single-core fibers, and the single-core receiving connector having one receiving connector port and the number of single-core receiving connectors being the same as the first receiving single-core fibers, or The number of the first transmitting single-core fibers is equal to the number of the first receiving single-core fibers, and the connector ports of the transmitting and receiving connectors are A dual transmitting / receiving connector fixed to the housing, the dual transmitting / receiving connector having one transmitting connector port and one receiving connector port, the dual transmitting / receiving connectors being the same number as the first transmitting single-core fibers.

2. The optical input / output device according to claim 1.

6. the cores of the first transmitting single-core fibers connected to a pair of the connector ports adjacent to each other are optically coupled to the transmitting cores of different ones of the multi-core fibers, The cores of the first receiving single-core fibers connected to a pair of adjacent connector ports are optically coupled to the receiving cores of different multi-core fibers, respectively.

6. The optical input / output device according to claim 5.

7. the cores of the first transmitting single-core fibers connected to a pair of adjacent connector ports are optically coupled to a pair of transmitting cores other than the adjacent core pair at the shortest distance in one of the multi-core fibers, The cores of the first receiving single-core fibers connected to a pair of adjacent connector ports are optically coupled to a pair of receiving cores other than the adjacent core pair at the shortest distance in one of the multi-core fibers.

6. The optical input / output device according to claim 5.

8. the receiving core is located between a pair of the transmitting cores in the multicore fiber to which the cores of the first transmitting single-core fibers connected to a pair of the connector ports adjacent to each other are optically coupled, The transmitting core is located between a pair of the receiving cores in the multi-core fiber to which the cores of the first receiving single-core fibers connected to a pair of the connector ports adjacent to each other are optically coupled.

8. The optical input / output device according to claim 7.

9. In at least one of the multicore fibers, at least one of the core pairs adjacent to each other at the shortest distance is a transmitting / receiving core pair, one of which is the transmitting core and the other of which is the receiving core.

9. The optical input / output device according to claim 2, wherein the optical input / output device is a semiconductor device.

10. In at least one of the multicore fibers, all of the core pairs adjacent to each other at the shortest distance are the transmitting / receiving core pairs.

10. The optical input / output device according to claim 9.

11. All of the multi-core fibers are longer than each of the first transmitting single-core fibers and each of the first receiving single-core fibers.

11. The optical input / output device according to claim 2,

12. The core of each of the first transmitting single-core fibers is optically coupled to the transmitting port of the transceiver, and the core of each of the first receiving single-core fibers is optically coupled to the receiving port of the transceiver.

12. The optical input / output device according to claim 2, wherein the optical input / output device is a semiconductor device.

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