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

[0004] ,

[0006] , ,

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[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 as 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 on 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. Therefore, 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. <​​To achieve the above objective, the optical input / output device of the present invention comprises a plurality of multicore fibers including at least one transmitting core and at least one receiving core; a number of first transmitting single-core fibers equal to the total number of transmitting cores of all the multicore fibers; a number of first receiving single-core fibers equal to the total number of receiving cores of all the multicore fibers; and a number of fan-in / fan-out devices equal to the number of all the multicore fibers, wherein each multicore fiber is a fan-in / fan-out device that optically couples each core at one end of the same number of first transmitting single-core fibers equal to the number of transmitting cores of the multicore fiber with each of the transmitting cores of the multicore fiber, and a fan-in / fan-out device that optically couples each core at one end of the same number of first receiving single-core fibers equal to the number of receiving cores of the multicore fiber with each of the receiving cores of the multicore fiber.

[0007] As described above, the present invention provides an optical input / output device that can reduce crosstalk that affects communication. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of an optical input / output device according to an embodiment of the present invention. [Figure 2] This figure shows a different example of an optical coupling embodiment of a multicore fiber, a single core fiber, and a transceiver connector. [Figure 3] This figure shows other examples different from the embodiments of optical coupling of multicore fiber, single core fiber, and transceiver connectors. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments for carrying out the optical input / output device according to the present invention are illustrated with accompanying drawings. The embodiments illustrated below are for the purpose of facilitating understanding of the present invention and are not intended to limit the interpretation of the present invention. The present invention can be modified and improved from the following embodiments without departing from its spirit. In addition, in this specification, the dimensions of each component may be exaggerated in order to facilitate understanding.

[0010] Figure 1 is a schematic diagram of an optical input / output device according to an embodiment. As shown in Figure 1, the optical input / output device 1 of this embodiment mainly comprises a multicore fiber 10, a first transmitting optical fiber 21, a first receiving optical fiber 22, a fan-in / fan-out device 30, a transmit / receive connector 40, and a patch cord 3.

[0011] The optical input / output device 1 of this embodiment is a device that transmits and receives light with a transceiver 100 having a plurality of transmit ports 101 and a plurality of receive ports 102. The plurality of transmit ports 101 of the transceiver 100 are arranged in a line and transmit optical signals to the optical input / output device 1. The plurality of receive ports 102 of the transceiver 100 are also arranged in a line and receive optical signals emitted from the optical input / output device 1. In this embodiment, the transceiver 100 has a plurality of unused ports 103 that do not transmit or receive optical signals and are arranged in a straight line at predetermined intervals. Each transmit port 101 is arranged at the predetermined interval on the extension of the straight line in which the unused ports 103 are located, on one side with respect to the unused ports 103. Similarly, each receive port 102 is arranged at the predetermined interval on the extension of the straight line in which the unused ports 103 are located, on the other side with respect to the unused ports 103.

[0012] In this embodiment, the optical input / output device 1 has multiple multicore fibers 10. In the example shown in Figure 1, the optical input / output device 1 has two multicore fibers 10.

[0013] Each multicore fiber 10 in this embodiment comprises a transmitting core 11 that propagates light from one end to the other, a receiving core 12 that propagates light from the other end to the one end, and a cladding 13 that surrounds the outer surfaces of the transmitting core 11 and the receiving core 12. In this example, each multicore fiber 10 comprises a plurality of transmitting cores 11 and a plurality of receiving cores 12. Specifically, as shown in Figure 1, each multicore fiber 10 comprises two transmitting cores 11 and two receiving cores 12. Each transmitting core 11 and receiving core 12 propagates light of the wavelength used for communication in single mode. However, each transmitting core 11 and receiving core 12 may propagate light of the wavelength used for communication in several modes, in which case a signal can be superimposed on the light of each mode.

[0014] In this example, in each multicore fiber 10, the pair of transmitting cores 11 and the pair of receiving cores 12 are arranged on opposite vertices of a square. Since the vertices located on one side of a square are adjacent vertices at the shortest distance from each other, in each multicore fiber 10 in this example, the pair of cores adjacent to each other at the shortest distance is a transmitting / receiving core pair where one is a transmitting core 11 and the other is a receiving core 12.

[0015] The first transmitting optical fiber 21 and the first receiving optical fiber 22 are both single-core fibers. Therefore, the first transmitting optical fiber 21 and the first receiving optical fiber 22 can be understood as the first transmitting single-core fiber and the first receiving single-core fiber, respectively. The number of first transmitting optical fibers 21 is the same as the total number of transmitting cores 11 in all the multi-core fibers 10. In the example in Figure 1, since each of the two multi-core fibers 10 has two transmitting cores 11, the total number of transmitting cores 11 is four, and the number of first transmitting optical fibers 21 is four. Similarly, the number of first receiving optical fibers 22 is the same as the total number of receiving cores 12 in all the multi-core fibers 10. In the example in Figure 1, since each of the two multi-core fibers 10 has two receiving cores 12, the total number of receiving cores 12 is four, and the number of first receiving optical fibers 22 is four.

[0016] Furthermore, in the optical input / output device 1 of this embodiment, all multicore fibers 10 are longer than their respective first transmitting optical fibers 21 and their respective first receiving optical fibers 22. However, all multicore fibers 10 may also be shorter than their respective first transmitting optical fibers 21 and their respective first receiving optical fibers 22.

[0017] The fan-in-fan-out device 30 optically couples each core at one end of each first transmitting optical fiber 21 with each transmitting core 11, and optically couples each core at one end of each first receiving optical fiber 22 with each receiving core 12. The fan-in-fan-out device 30 may be a spatial optical system device that performs the above coupling through space, or it may be a waveguide system device that performs the above coupling through a waveguide formed within the device. In Figure 1, an example of the optical path of the transmitted light in the fan-in-fan-out device 30 is shown by a dashed line, and an example of the optical path of the received light is shown by a dotted line. Therefore, it may be understood that the core of the multicore fiber 10 optically connected to the first transmitting optical fiber 21 is the transmitting core 11, and the core of the multicore fiber 10 optically connected to the first receiving optical fiber 22 is the receiving core 12.

[0018] In a spatial optical system device, for example, a lens is used. In this case, one end of each first transmitting optical fiber 21 and one end of each first receiving optical fiber 22 are arranged in the same way as the arrangement of each transmitting core 11 and each receiving core 12 that are to be coupled to each other, and a lens is placed between the multicore fiber 10 and the first transmitting optical fiber 21 and the first receiving optical fiber 22. The positions of each multicore fiber 10, lens, first transmitting optical fiber 21, and first receiving optical fiber 22 are adjusted so that they are coupled as described above. Therefore, each light emitted from the core of each first transmitting optical fiber 21 is refracted by the lens and incident on the transmitting core 11 of the multicore fiber 10, and each light emitted from each receiving core 12 of the multicore fiber 10 is refracted by the lens and incident on the core of each first receiving optical fiber 22.

[0019] In waveguide-based devices, for example, a waveguide substrate in which waveguides are formed three-dimensionally is used. In this case, for example, one end of a plurality of waveguides connected to the cores of each first transmitting optical fiber 21 and each receiving core 12 is arranged linearly at one end of the waveguide substrate, and the position of the waveguide is changed by forming a curved part of the waveguide within the waveguide substrate, so that at the other end of the waveguide substrate, waveguides are arranged in the same way as the arrangement of each transmitting core 11 and each receiving core 12 in each multicore fiber 10. Thus, the above coupling is achieved. Consequently, the light emitted from the core of each first transmitting optical fiber 21 propagates through the waveguide and enters the transmitting core 11 of the multicore fiber 10, and the light emitted from each receiving core 12 of the multicore fiber 10 propagates through the waveguide and enters the core of each first receiving optical fiber 22.

[0020] The transmit / receive connector 40 comprises the same number of transmit connector ports 41 as the number of first transmit optical fibers 21, each connected in one-to-one correspondence to the other end of each first transmit optical fiber 21, and the same number of receive connector ports 42 as the number of first receive optical fibers 22, each connected in one-to-one correspondence to the other end of each first receive optical fiber 22. Therefore, the number of connector ports, each consisting of a transmit connector port 41 and each receive connector port 42, is the same as the total number of first transmit optical fibers 21 and first receive optical fibers 22. Each transmit connector port 41 can be optically coupled to the transmit port 101 of the transceiver 100 via a patch cord 3, which will be described later. Similarly, each receive connector port 42 can be optically coupled to the receive port 102 of the transceiver 100 via a patch cord 3, each receiving optical fiber 22. Figure 1 shows the state in which the core of each first transmitting optical fiber 21 is optically coupled to the transmitting port 101 of the transceiver 100, and the core of each first receiving optical fiber 22 is optically coupled to the receiving port 102 of the transceiver 100.

[0021] In addition, the transmission / reception connector 40 includes a dummy port 43 that does not perform optical transmission and 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. 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.

[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. Another 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 transmitting optical fiber 61 and the second receiving optical fiber 62 are both single-core fibers. Therefore, the second transmitting optical fiber 61 and the second receiving optical fiber 62 can be understood as the second transmitting single-core fiber and the second receiving single-core fiber, respectively. In this embodiment, the second transmitting optical fiber 61 is longer than the first transmitting optical fiber 21, and the second receiving optical fiber 62 is longer than the first receiving optical fiber 22. Furthermore, the outer diameter of the cladding of the second transmitting optical fiber 61 and the second receiving optical fiber 62 is larger than the outer diameter of the cladding of the first transmitting optical fiber 21 and the first receiving optical fiber 22. Therefore, the microbend loss of the second transmitting optical fiber 61 and the second receiving optical fiber 62 tends to be smaller than that of the first transmitting optical fiber 21 and the first receiving optical fiber 22. Also, due to the relationship of the outer diameters of the cladding as described above, the bending break probability of the first transmitting optical fiber 21 and the first receiving optical fiber 22 tends to be lower than that of the second transmitting optical fiber 61 and the second receiving optical fiber 62. Furthermore, the optical confinement forces of the first transmitting optical fiber 21 and the first receiving optical fiber 22 are greater than the optical confinement forces of the second transmitting optical fiber 61 and the second receiving optical fiber 62. One example of a configuration that achieves this relationship of optical confinement forces is one in which the difference in relative refractive index of the cores of the first transmitting optical fiber 21 and the first receiving optical fiber 22 is greater than the difference in relative refractive index of the cores of the second transmitting optical fiber 61 and the second receiving optical fiber 62. In this case, it is preferable that the refractive index of the cores of the first transmitting optical fiber 21 and the first receiving optical fiber 22 is higher than the refractive index of the cores of the second transmitting optical fiber 61 and the second receiving optical fiber 62. Alternatively, each of the first transmitting optical fiber 21 and the first receiving optical fiber 22 may have a core, a cladding surrounding the core with a lower refractive index than the core, and a trench layer surrounding the core and the cladding with a lower refractive index than the cladding, while each of the second transmitting optical fiber 61 and the second receiving optical fiber 62 may have a core, a cladding surrounding the core with a lower refractive index than the core, but without a trench layer surrounding the core and the cladding with a lower refractive index than the cladding.

[0026] The first intermediate connector 50 includes the same number of first intermediate transmit connector ports 51 as the number of second transmit optical fibers 61 connected to one end of each second transmit optical fiber 61, and the same number of first intermediate receive connector ports 52 as the number of second receive optical fibers 62 connected to one end of each second receive optical fiber 62. Therefore, the number of first intermediate connector ports, consisting of each first intermediate transmit connector port 51 and each first intermediate receive connector port 52, is the same as the total number of second transmit optical fibers 61 and second receive optical fibers 62.

[0027] Furthermore, in this embodiment, the first intermediate connector 50 includes dummy ports 53 that do not transmit or receive light. In this embodiment, the number of dummy ports 53 is the same as that of the dummy ports 43, and they are arranged in the same way as the dummy ports 43. Each first intermediate transmit connector port 51, each dummy port 53, and each first intermediate receive connector port 52 are arranged in the same way as each transmit connector port 41, each dummy port 43, and each receive connector port 42 in the transmit / receive connector 40. Therefore, each first intermediate transmit connector port 51 is located on one side relative to the dummy port 53, and each first intermediate receive connector port 52 is located on the other side relative to the dummy port 53.

[0028] The first intermediate connector 50 is positioned by an adapter (not shown) and connected to the transmit / receive connector 40. As a result, each first intermediate transmit connector port 51 is connected to the respective transmit connector port 41 of the transmit / receive connector 40, and each first intermediate receive connector port 52 is connected to the respective receive connector port 42 of the transmit / receive connector 40. Consequently, the core at the other end of the first transmit optical fiber 21 connected to each transmit connector port 41 is optically coupled to the core of the second transmit optical fiber 61 connected to each first intermediate transmit connector port 51, and the core at the other end of the first receive optical fiber 22 connected to each receive connector port 42 is optically coupled to the core of the second receive optical fiber 62 connected to each first intermediate receive connector port 52.

[0029] The second intermediate connector 70 includes the same number of second intermediate transmit connector ports 71 as the number of second transmit optical fibers 61 connected to the other end of each second transmit optical fiber 61, and the same number of second intermediate receive connector ports 72 as the number of second receive optical fibers 62 connected to the other end of each second receive optical fiber 62. Therefore, the number of second intermediate connector ports, consisting of each second intermediate transmit connector port 71 and each second intermediate receive connector port 72, is the same as the total number of second transmit optical fibers 61 and second receive optical fibers 62.

[0030] Furthermore, in this embodiment, the second intermediate connector 70 includes dummy ports 73 that do not transmit or receive light. In this embodiment, the number of dummy ports 73 is the same as the number of unused ports 103 of the transceiver 100, and they are arranged in the same way as the unused ports 103. Each second intermediate transmit connector port 71, each dummy port 73, and each second intermediate receive connector port 72 are arranged in the same way as each transmit port 101, each unused port 103, and each receive port 102 of the transceiver 100. Therefore, each second intermediate transmit connector port 71 is located on one side relative to the dummy port 73, and each second intermediate receive connector port 72 is located on the other side relative to the dummy port 73.

[0031] The second intermediate connector 70 is connectable to the transceiver 100. Therefore, each second intermediate transmit connector port 71 is connectable to each transmit port 101 of the transceiver 100, and each second intermediate receive connector port 72 is connectable to each receive port 102 of the transceiver 100. Figure 1 shows the state in which each second intermediate transmit connector port 71 is connected to each transmit port 101, and each second intermediate receive connector port 72 is connected to each receive port 102. In this state, each second intermediate transmit connector port 71 optically couples the core of each second transmit optical fiber 61 with the transmit port 101 of the transceiver 100. Similarly, each second intermediate receive connector port 72 optically couples the core of each second receive optical fiber 62 with the receive port 102 of the transceiver 100.

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

[0033] As described above, the optical input / output device 1 of this embodiment comprises at least one multicore fiber 10 including at least one transmitting core 11 and at least one receiving core 12, first transmitting optical fibers 21 in the same number as the total number of transmitting cores 11 in all multicore fibers 10, first receiving optical fibers 22 in the same number as the total number of receiving cores 12 in all multicore fibers 10, and optically coupling each core at one end of each first transmitting optical fiber 21 with each transmitting core 11, and each core at one end of each first receiving optical fiber 22 with each receiving core 12 The system includes a fan-in / fan-out device 30 that optically couples the two, and a transceiver connector 40 having the same number of transmit connector ports 41 as the first transmit optical fiber 21, which are connected to the other end of each first transmit optical fiber 21 and capable of optically coupling the core of each first transmit optical fiber 21 with the transmit port 101 of the transceiver 100, and the same number of receive connector ports 42 as the first receive optical fiber 22, which are connected to the other end of each first receive optical fiber 22 and capable of optically coupling the core of each first receive optical fiber 22 with the receive port 102 of the transceiver 100.

[0034] With this optical input / output device 1, the optical signal transmitted from the transceiver 100's transmission port 101 propagates through the first transmission optical fiber 21 to the transmission core 11 in all multicore fibers 10, and the optical signal received at the transceiver 100's reception port 102 propagates through the first reception optical fiber 22 to the reception core 12. Therefore, light propagates in opposite directions between the transmission core 11 and the reception core 12 within the multicore fiber 10. Consequently, even if crosstalk occurs between the transmission core 11 and the reception core 12, the light crosstalking from the transmission core 11 to the reception core 12 is not received by the transceiver 100, and the light crosstalking from the reception core 12 to the transmission core 11 is not propagated to the destination. Therefore, the optical input / output device 1 of the present invention can reduce crosstalk that affects communication.

[0035] Furthermore, in this embodiment, the core pairs adjacent to each other at the shortest distance in the multicore fiber 10 are transmit / receive core pairs, where one is a transmit core 11 and the other is a receive core 12. Crosstalk tends to increase as the distance between cores decreases. Therefore, by having the core pairs adjacent to each other at the shortest distance be this transmit / receive core pair, crosstalk affecting communication can be reduced compared to the case where all the core pairs adjacent to each other at the shortest distance are either transmit cores 11 or receive cores 12. In this embodiment, in each multicore fiber 10, all core pairs adjacent to each other at the shortest distance are transmit / receive core pairs.

[0036] Furthermore, the optical input / output device 1 of this embodiment includes a plurality of multicore fibers 10, and the cores of each first transmitting optical fiber 21 connected to a pair of adjacent transmitting connector ports 41 are optically coupled to the transmitting core 11 of a different multicore fiber 10, respectively, and the cores of each first receiving optical fiber 22 connected to a pair of adjacent receiving connector ports 42 are optically coupled to the receiving core 12 of a different multicore fiber 10, respectively. The first transmitting optical fiber 21 connected to a pair of adjacent transmitting connector ports 41 and the first receiving optical fiber 22 connected to a pair of adjacent receiving connector ports 42 tend to be optically coupled to a pair of adjacent transmitting ports 101 and a pair of adjacent receiving ports 102, respectively, in the transceiver 100. Incidentally, in transceiver 100, crosstalk is generally likely to occur between the light emitted from adjacent transmit ports 101 and between the electrical signals that become this light, and between the light emitted from adjacent receive ports 102 and between the electrical signals that are converted from this light. However, even when such crosstalk occurs, this configuration suppresses crosstalk in the multicore fiber 10 between the respective optical signals propagating through the cores of the pair of first transmit optical fibers 21 in transceiver 100 where crosstalk occurs, and also suppresses crosstalk in the multicore fiber 10 between the respective optical signals propagating through the cores of the pair of first receive optical fibers 22 in transceiver 100 where crosstalk occurs. Therefore, compared to cases where a pair of first transmit optical fibers 21 connected to a pair of adjacent connector ports are coupled to the transmit core 11 of the same multicore fiber 10, or where a pair of first receive optical fibers 22 connected to a pair of adjacent connector ports are coupled to the receive core 12 of the same multicore fiber 10, crosstalk that affects communication can be reduced.

[0037] Furthermore, in the optical input / output device 1 of this embodiment, all multicore fibers 10 are longer than their respective first transmitting optical fibers 21 and their respective first receiving optical fibers 22. In multicore fibers 10, differences in the lengths of the cores are less likely to occur, thus reducing skew. However, in the first transmitting optical fibers 21 and the first receiving optical fibers 22, differences in the lengths of their respective cores are more likely to occur, making skew more likely. Therefore, by having all multicore fibers 10 longer than their respective first transmitting optical fibers 21 and their respective first receiving optical fibers 22, as in this embodiment, the proportion of single-core fiber transmission paths can be reduced, and skew can be suppressed compared to the case where all multicore fibers 10 are shorter than their respective first transmitting optical fibers 21 and their respective first receiving optical fibers 22. Note that if the length of all multicore fibers 10 within the housing 2 is longer than the length of their respective first transmitting optical fibers 21 and their respective first receiving optical fibers 22 within the housing 2, skew within the housing 2 can be suppressed.

[0038] Furthermore, in the optical input / output device 1 of this embodiment, the optical confinement force of the first transmitting optical fiber 21 and the first receiving optical fiber 22 is greater than the optical confinement force of the second transmitting optical fiber 61 and the second receiving optical fiber 62. Alternatively, the first transmitting optical fiber 21 and the first receiving optical fiber 22 each have a trench layer, while the second transmitting optical fiber 61 and the second receiving optical fiber 62 each do not have a trench layer. Moreover, the outer diameter of the cladding of the second transmitting optical fiber 61 and the second receiving optical fiber 62 is greater than the outer diameter of the cladding of the first transmitting optical fiber 21 and the first receiving optical fiber 22. For this reason, as described above, the microbend loss of the second transmitting optical fiber 61 and the second receiving optical fiber 62 tends to be smaller than that of the first transmitting optical fiber 21 and the first receiving optical fiber 22, and the bending fracture probability of the first transmitting optical fiber 21 and the first receiving optical fiber 22 tends to be smaller than that of the second transmitting optical fiber 61 and the second receiving optical fiber 62. As in this embodiment, the first transmitting optical fiber 21 and the first receiving optical fiber 22 of the optical input / output device 1, the fan-in / fan-out device 30, and at least a portion of the multicore fiber 10 tend to be housed within the housing 2. Therefore, because the first transmitting optical fiber 21 and the first receiving optical fiber 22 are routed within a limited space, the first transmitting optical fiber 21 and the first receiving optical fiber 22 located within the housing 2 tend to be bent with a smaller bending radius than the second transmitting optical fiber 61 and the second receiving optical fiber 62 of the patch cord 3 located outside the housing 2. Consequently, the optical confinement force of the first transmitting optical fiber 21 and the first receiving optical fiber 22 is greater than the optical confinement force of the second transmitting optical fiber 61 and the second receiving optical fiber 62, respectively, thereby suppressing the bending loss of light in the first transmitting optical fiber 21 and the first receiving optical fiber 22. Furthermore, due to this relationship of optical confinement force, as described above, the refractive index of the cores of the second transmitting optical fiber 61 and the second receiving optical fiber 62 can be made smaller than the refractive index of the cores of the first transmitting optical fiber 21 and the first receiving optical fiber 22.In this case, the amount of dopant added to the cores of the second transmitting optical fiber 61 and the second receiving optical fiber 62 to increase the refractive index can be reduced, thereby reducing the loss due to Rayleigh scattering in the second transmitting optical fiber 61 and the second receiving optical fiber 62, which tend to be longer than the first transmitting optical fiber 21 and the first receiving optical fiber 22. Furthermore, even if the first transmitting optical fiber 21 and the first receiving optical fiber 22 have a trench layer, the bending loss of light in the first transmitting optical fiber 21 and the first receiving optical fiber 22 can be suppressed. In addition, although optical fibers with a trench layer can suppress bending loss as described above, they tend to have a greater transmission loss than optical fibers without a trench layer for long-distance light transmission. Therefore, as described above, by not having a trench layer in the second transmitting optical fiber 61 and the second receiving optical fiber 62, which tend to be longer than the first transmitting optical fiber 21 and the first receiving optical fiber 22, the transmission loss of light in the second transmitting optical fiber 61 and the second receiving optical fiber 62 can be suppressed, and the optical loss in the optical input / output device 1 can be reduced. Furthermore, as described above, the bending fracture coefficients of the first transmitting optical fiber 21 and the first receiving optical fiber 22 can be made smaller than the fracture coefficients of the second transmitting optical fiber 61 and the second receiving optical fiber 62. Therefore, even if the first transmitting optical fiber 21 and the first receiving optical fiber 22 are bent with a greater curvature than the second transmitting optical fiber 61 and the second receiving optical fiber 62, the fracture of the first transmitting optical fiber 21 and the first receiving optical fiber 22 can be suppressed.

[0039] Although the present invention has been described above using the above embodiments as examples, the present invention is not limited to the above embodiments.

[0040] For example, in the above embodiment, an optical input / output device 1 equipped with two multicore fibers 10 was described as an example. However, the optical input / output device of the present invention may be equipped with three or more multicore fibers, or it may be equipped with only one multicore fiber.

[0041] Furthermore, an example was described in which each multicore fiber 10 has two transmitting cores 11 and two receiving cores 12. However, as long as a multicore fiber has at least one transmitting core 11 and at least one receiving core, the number of transmitting cores 11 and receiving cores 12 can be one or three or more, and the number of transmitting cores 11 and the number of receiving cores 12 can be different from each other. Generally, in a transceiver 100, a transmitting port 101 and a receiving port 102 are provided in a one-to-one relationship, so it is preferable that the total number of transmitting cores 11 and the total number of receiving cores 12 of all multicore fibers 10 are equal.

[0042] Furthermore, in the above embodiment, an example was shown in which, in each multicore fiber 10, the core pairs adjacent to each other at the shortest distance are transceiver core pairs, where one is a transmit core 11 and the other is a receive core 12. However, for example, at least some of the core pairs adjacent to each other at the shortest distance may be core pairs of transmit cores 11 or core pairs of receive cores 12. An example of this is a multicore fiber in which an odd number of cores are arranged in a ring, and only one pair of each adjacent core pair at the shortest distance is a core pair of transmit cores 11 or a core pair of receive cores 12. Also, in some multicore fibers, at least some of the core pairs adjacent to each other at the shortest distance may be transceiver core pairs. Moreover, the example in which all core pairs adjacent to each other at the shortest distance are transceiver core pairs is not limited to the above embodiment. For example, there may be three or more transmit cores 11 and three or more receive cores 12, and the transmit cores 11 and receive cores 12 may be arranged alternately in a ring.

[0043] Furthermore, the arrangement of cores in each multicore fiber 10 is not limited to the above embodiment. For example, multiple cores may be arranged in a straight line. In this case, the transmitting cores 11 and receiving cores 12 may be arranged alternately such that all core pairs adjacent to each other at the shortest distance become transmitting and receiving core pairs.

[0044] Furthermore, the multicore fiber 10 in the optical input / output device 1 of the present invention may have a central core located at the center of the cladding 13 and a plurality of outer cores arranged to surround the central core. In this case, the central core is a transmitting core 11 or a receiving core 12, and the plurality of outer cores include at least one transmitting core 11 and at least one receiving core 12. Figure 2 shows an example of optical coupling of the multicore fiber 10, the first transmitting optical fiber 21, the first receiving optical fiber 22, and the transceiver connector 40 when such a multicore fiber 10 is used. Components similar to those in the above embodiment are denoted by the same reference numerals as in the above embodiment, and their descriptions are omitted unless specifically explained. In Figure 2, to avoid complexity of the figure, the fan-in / fan-out device 30 is omitted, and only the multicore fiber 10, the first transmitting optical fiber 21, the first receiving optical fiber 22, and the transceiver connector 40 are shown. Therefore, Figure 2 does not mean that the first receiving optical fiber 22 and the transceiver connector 40 are directly connected to the multicore fiber 10.

[0045] As shown in Figure 2, in this example, the optical input / output device 1 is equipped with multiple multicore fibers 10. The number of multicore fibers 10 in this example is, for example, 8. However, in Figure 2, to avoid complicating the diagram, some of the multicore fibers 10 are shown as dots. Of each multicore fiber 10, in half of the multicore fibers 10, the central core located in the center of the cladding 13 is the transmitting core 11, and in the other half of the multicore fibers 10, the central core located in the center of the cladding 13 is the receiving core 12. In each multicore fiber 10, two transmitting cores 11 are arranged diagonally around this central core as part of the outer core, and two receiving cores 12 are arranged on the other diagonal as part of the other outer core. Therefore, when looking only at the outer core, the transmitting cores 11 and the receiving cores 12 are adjacent to each other.

[0046] In this example, the transmit / receive connector 40 consists of multiple subconnectors 45. Each subconnector 45 has two or more connector ports from among all the connector ports of the transmit / receive connector 40. As described above, if the number of multicore fibers 10 is 8, the transmit / receive connector 40 has, for example, five 8-port subconnectors 45. In the example shown in Figure 2, each subconnector 45 has an equal number of transmit connector ports 41 and receive connector ports 42, and the total number of connector ports, including the transmit connector ports 41 and receive connector ports 42, is the same as the total number of transmit cores 11 and receive cores 12 of the multicore fiber 10. However, in Figure 2, to avoid complicating the diagram, some of the subconnectors 45 are shown as dots.

[0047] Then, the first transmitting optical fiber 21, which is optically coupled to the transmitting core 11, which is the central core of half of the multicore fibers 10, is connected to the transmitting connector port 41 of a specific subconnector 45, and the first receiving optical fiber 22, which is optically coupled to the receiving core 12, which is the central core of the other half of the multicore fibers 10, is connected to the receiving connector port 42 of a specific subconnector 45. In Figure 2, this specific subconnector 45 is the rightmost subconnector 45. In addition, each first transmitting optical fiber 21 connected to each transmitting core 11, which is the outer core of each multicore fiber 10, is connected to the transmitting connector port 41 of a subconnector 45 other than the specific subconnector 45, and each first receiving optical fiber 22 connected to each receiving core 12, which is the outer core of each multicore fiber 10, is connected to the receiving connector port 42 of a subconnector 45 other than the specific subconnector 45. In the example shown in Figure 2, some connection details are omitted, but each first transmitting optical fiber 21 connected to the transmitting core 11, which is the outer core of a single multicore fiber 10, and each first receiving optical fiber 22 connected to each receiving core 12, which is also an outer core, are connected to the transmitting connector port 41 and the receiving connector port 42 of the same partial connector 45.

[0048] Furthermore, although not specifically shown in the diagram, in the modified version of Figure 2, the central core of each multicore fiber 10 may be a transmitting core 11. In this case, the specific subconnector 45 has the same number of transmitting connector ports 41 as the number of multicore fibers 10, and the first transmitting optical fiber 21 connected to each transmitting connector port 41 of the specific subconnector 45 is optically coupled to the central core of each multicore fiber 10. Alternatively, the central core of each multicore fiber 10 may be a receiving core 12. In this case, the specific subconnector 45 has the same number of receiving connector ports 42 as the number of multicore fibers 10, and the first receiving optical fiber 22 connected to each receiving connector port 42 of the specific subconnector 45 is optically coupled to the central core of each multicore fiber 10.

[0049] In the example and modified version shown in Figure 2, the first transmitting optical fiber 21 or first receiving optical fiber 22, which is optically coupled to the respective central core of each multicore fiber 10, is connected to the connector port of a specific subconnector 45. The first transmitting optical fiber 21 connected to each transmitting core 11, which is the outer core, and the first receiving optical fiber 22 connected to each receiving core 12, which is the outer core, are connected to the connector ports of subconnectors 45 other than the specific subconnector 45. Generally, light propagating through the central core is affected by crosstalk from each of the surrounding cores arranged around it. Therefore, by gathering and connecting single-core fibers having cores optically coupled to the central core as described above to a specific subconnector 45, it becomes easier to gather and connect light with a large crosstalk effect from the specific subconnector 45 to a single transceiver. This makes it easier to perform appropriate processing against crosstalk in the transceiver.

[0050] Furthermore, generally, when multicore fibers are connected, the outer core tends to have a greater connection loss than the central core due to the effect of rotational misalignment of the fiber's axis. Moreover, the effect of this rotational misalignment is roughly the same for outer cores that are equidistant from the center of the multicore fiber. Therefore, as shown in the example in Figure 2, by connecting each optical fiber connected to the outer core of a single multicore fiber 10 to the connector port of the same subconnector 45, the variation in connection loss between connector ports in each subconnector 45 can be suppressed. This makes it easier to process connection loss in the transceiver 100 to which the subconnector 45 is connected.

[0051] Furthermore, in the above embodiment, the cores of each first transmitting optical fiber 21 connected to a pair of adjacent transmitting connector ports 41 are optically coupled to the transmitting cores 11 of different multicore fibers 10, and the cores of each first receiving optical fiber 22 connected to a pair of adjacent receiving connector ports 42 are optically coupled to the receiving cores 12 of different multicore fibers 10. However, the cores of each first transmitting optical fiber 21 connected to a pair of adjacent transmitting connector ports 41 may be optically coupled to the transmitting cores 11 of one multicore fiber 10, and the cores of each first receiving optical fiber 22 connected to a pair of adjacent receiving connector ports 42 may be optically coupled to the receiving cores 12 of one multicore fiber 10.

[0052] Figure 3 shows an example of an embodiment of optical coupling between the multicore fiber 10, the first transmitting optical fiber 21, the first receiving optical fiber 22, and the transceiver connector 40, when such a multicore fiber 10 is used. As shown in Figure 3, in the multicore fiber 10 of this example, the transmitting cores 11 and the receiving cores 12 are arranged alternately. Therefore, the pair of cores adjacent to each other at the shortest distance is the aforementioned transmitting core pair. The first transmitting optical fiber 21 connected to adjacent transmitting connector ports 41 of the transceiver connector 40 is optically coupled to a pair of transmitting cores 11 of the multicore fiber 10 other than the pair of cores adjacent to each other at the shortest distance, and the first receiving optical fiber 22 connected to adjacent receiving connector ports 42 is optically coupled to a pair of receiving cores 12 of the multicore fiber 10 other than the pair of cores adjacent to each other at the shortest distance. Furthermore, in the example shown in Figure 3, a receiving core 12 is located between a pair of transmitting cores 11 in a multicore fiber 10, where the cores of each first transmitting optical fiber 21 connected to a pair of adjacent transmitting connector ports 41 are optically coupled, and a transmitting core 11 is located between a pair of receiving cores 12 in a multicore fiber 10, where the cores of each first receiving optical fiber 22 connected to a pair of adjacent receiving connector ports 42 are optically coupled.

[0053] Although different from Figure 3, the first transmitting optical fiber 21 connected to adjacent transmitting connector ports 41 of the transmitting / receiving connector 40 may be optically coupled to an adjacent pair of transmitting cores 11 via the receiving core 12 of the multicore fiber 10, and the first receiving optical fiber 22 connected to adjacent receiving connector ports 42 may be optically coupled to an adjacent pair of receiving cores 12 via the transmitting core 11 of the multicore fiber 10.

[0054] With this configuration, even if crosstalk occurs between the first transmitting optical fibers 21 or between the first receiving optical fibers 22 at adjacent connector ports in the transmitting / receiving connector 40, crosstalk in the multicore fiber 10 can be suppressed compared to cases where the cores of the pair of first transmitting optical fibers 21 experiencing the crosstalk are coupled to a pair of adjacent transmitting cores 11 in the multicore fiber 10 at the shortest distance, or where the cores of the pair of first receiving optical fibers 22 experiencing the crosstalk are coupled to a pair of adjacent receiving cores 12 in the multicore fiber 10 at the shortest distance. Furthermore, in this example, a receiving core 12 is located between a pair of transmitting cores 11, which are optically coupled to the cores of each first transmitting optical fiber 21 connected to a pair of adjacent transmitting connector ports 41, and a transmitting core 11 is located between a pair of receiving cores 12, which are optically coupled to the cores of each first receiving optical fiber 22 connected to a pair of adjacent receiving connector ports 42. Therefore, crosstalk affecting communication can be suppressed compared to cases where a receiving core 12 is not located between the pair of transmitting cores 11, or where a transmitting core 11 is not located between the pair of receiving cores 12.

[0055] Furthermore, in this invention, the patch cord 3 is not essential, and the transmit connector port 41 and receive connector port 42 of the transmit / receive connector 40 and the transmit port 101 and receive port 102 of the transceiver 100 may be connected by other means. Also, the transmit / receive connector 40 is not essential, and for example, the first transmit optical fiber 21 and the second transmit optical fiber 61 may be fusion spliced ​​together, or the first receive optical fiber 22 and the second receive optical fiber 62 may be fusion spliced ​​together. In this case, the fusion splice may be located inside or outside the housing 2, and it is preferable that it be located inside the housing 2 in order to suppress breakage due to trauma. Also, the second transmit optical fiber 61 may be connected to the transmit port 101 of the transceiver 100, and the second receive optical fiber 62 may be connected to the receive port 102 of the transceiver 100. Furthermore, the first transmitting optical fiber 21 may not be directly fusion-spliced ​​with the second transmitting optical fiber 61, but may be provided in a state where it can be fusion-spliced ​​with the second transmitting optical fiber 61, and the first receiving optical fiber 22 may not be fusion-spliced ​​with the second receiving optical fiber 62, but may be provided in a state where it can be fusion-spliced ​​with the second receiving optical fiber 62. If a housing 2 is provided, the fusion splice point between the first transmitting optical fiber 21 and the second transmitting optical fiber 61 may be inside the housing 2, and the fusion splice point between the first receiving optical fiber 22 and the second receiving optical fiber 62 may be outside the housing 2. In either case, at least a portion of the first transmitting optical fiber 21 is housed inside the housing 2, and at least a portion of the first receiving optical fiber 22 is located outside the housing 2. Alternatively, at least a portion of the second transmitting optical fiber 61 is housed inside the housing 2, and at least a portion of the second receiving optical fiber 62 is located outside the housing 2. The transmitting and receiving connector 40 may also be located outside the housing 2. In this case, the degree of freedom in the placement of the transmit / receive connector 40 may increase. Also, if the transmit / receive connector 40 and the first intermediate connector 50 are connected to each other, the degree of freedom in the placement of the first intermediate connector 50 and the transmit / receive connector 40 may increase.Furthermore, in this case, for example, when the distance between the transmit / receive connector 40 and the first intermediate connector 50 and the transceiver 100 is small, the degree of freedom in the work of switching and connecting the first transmitting optical fiber 21, second transmitting optical fiber 61, first receiving optical fiber 22 and second receiving optical fiber 62, which are connected between each port of the first intermediate connector 50 and each port of the transceiver 100, to other ports of the first intermediate connector 50 or other ports of the transceiver 100 can be increased. Also, the transmit / receive connector 40 may be located outside the housing 2. Also, the transmit / receive connector 40 may be located outside the housing 2, and the fusion splice may be located inside or outside the housing 2. Also, multiple transmit / receive connectors 40 may be provided. Also, instead of the transmit / receive connector 40, the first transmitting optical fiber 21 and the second transmitting optical fiber 61 may be connected to each other by an optical fiber holding member such as a mechanical splice element, and the first receiving optical fiber 22 and the second receiving optical fiber 62 may be connected to each other.

[0056] Furthermore, in the above embodiment, the outer diameters of the cladding of the second transmitting optical fiber 61 and the second receiving optical fiber 62 are larger than the outer diameters of the cladding of the first transmitting optical fiber 21 and the first receiving optical fiber 22, and the optical confinement forces of the first transmitting optical fiber 21 and the first receiving optical fiber 22 are larger than the optical confinement forces of the second transmitting optical fiber 61 and the second receiving optical fiber 62, respectively, but this is not essential. Alternatively, in at least one of the optical fiber pairs consisting of the first transmitting optical fiber 21 and the second transmitting optical fiber 61 that are optically coupled to each other, and the optical fiber pairs consisting of the first receiving optical fiber 22 and the second receiving optical fiber 62 that are connected to each other, the outer diameters of the cladding of the second transmitting optical fiber 61 and the second receiving optical fiber 62 are larger than the outer diameters of the cladding of the first transmitting optical fiber 21 and the first receiving optical fiber 22, respectively, and the optical confinement forces of the first transmitting optical fiber 21 and the first receiving optical fiber 22 are larger than the optical confinement forces of the second transmitting optical fiber 61 and the second receiving optical fiber 62, respectively. In other words, in at least one of a plurality of single-core fiber pairs, each consisting of a plurality of first single-core fibers, each comprising a first transmitting optical fiber 21 and a plurality of first receiving optical fibers 22, and a plurality of second single-core fibers, each comprising a second transmitting optical fiber 61 and a plurality of second receiving optical fibers 62, which are optically coupled to each first single-core fiber, the optical confinement force of the first single-core fiber may be greater than that of the second single-core fiber, and the outer diameter of the cladding of the second single-core fiber may be greater than that 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 greater than that of the cladding of the first single-core fiber.

[0057] Furthermore, in the above embodiment, a portion of each multicore fiber 10, the fan-in / fan-out device 30, each first transmitting optical fiber 21, and each first receiving optical fiber 22 were described as being housed within the space of the housing 2, but the housing 2 is not an essential component.

[0058] Furthermore, the transceiver connector 40 is not limited to the above configuration. For example, it may consist of the same number of single-core transceiver connectors as the number of first transceiver optical fibers 21 having one transceiver port 41, and the same number of single-core receiver connectors as the number of first receiver optical fibers 22 having one receiver connector port 42. Alternatively, if the number of first transceiver optical fibers 21 and the number of first receiver optical fibers 22 are the same, the transceiver connector 40 may consist of the same number of dual transceiver connectors as the number of first transceiver optical fibers 21, each having one transceiver port 41 and one receiver connector port 42.

[0059] Another example of a multicore fiber 10 is one in which multiple single-core fibers, each with a cladding, are bundled together with resin.

[0060] Furthermore, at least a portion of the optical fibers that are the first transmitting optical fiber 21 and the first receiving optical fiber 22 may consist of connectors for multiple optical fibers. A single optical fiber may have a limited fiber length. Therefore, by having the first transmitting optical fiber 21 and the first receiving optical fiber 22 consist of optical fiber connectors, the first transmitting optical fiber 21 and the first receiving optical fiber 22 can be made longer. In this case, it is preferable that the multiple optical fibers are connected by fusion splicing. By connecting by fusion splicing, connection loss can be reduced compared to when multiple optical fibers are connected by connectors. Furthermore, at least a portion of the optical fibers that are the second transmitting optical fiber 61 and the second receiving optical fiber 62 may consist of connectors for multiple optical fibers. In this case as well, the second transmitting optical fiber 61 and the second receiving optical fiber 62 can be made longer. In this case as well, from the viewpoint of reducing connection loss, it is preferable that the multiple optical fibers are connected by fusion splicing.

[0061] Furthermore, in this embodiment, the first transmitting optical fiber 21 and the first receiving optical fiber 22 may be bundled together as a ribbon fiber with one or more coatings, and the second transmitting optical fiber 61 and the second receiving optical fiber 62 may be bundled together as a ribbon fiber with one or more coatings. This allows the arrangement of the first transmitting optical fiber 21 and the first receiving optical fiber 22, and the arrangement of the second transmitting optical fiber 61 and the second receiving optical fiber 62 to be fixed. Therefore, the positional relationship of the ends of each optical fiber becomes clear, and the connection between the first transmitting optical fiber 21 and the second transmitting optical fiber 61, and the connection between the first receiving optical fiber 22 and the second receiving optical fiber 62 can be made easier. Also, in this case, if a transceiver connector 40 is not provided, and the first transmitting optical fiber 21 and the second transmitting optical fiber 61 are fusion spliced ​​together, or the first receiving optical fiber 22 and the second receiving optical fiber 62 are fusion spliced ​​together, the positional relationship of the optical fibers is clear, making fusion splicing easier. Furthermore, if the first transmitting optical fiber 21, the first receiving optical fiber 22, the second transmitting optical fiber 61, and the second receiving optical fiber 62 consist of an optical fiber connector in which multiple optical fibers are fused together, the optical fibers that are fused together may be included in separate ribbon cables. In this case, since the positional relationship of the multiple optical fibers included in each of the separate ribbon cables is clear, it is easy to form an optical fiber connector by fusion splicing the multiple optical fibers together when connecting ribbon cables to each other.

[0062] According to the present invention, an optical input / output device capable of reducing crosstalk affecting communication can be provided, which can be used, for example, in fields such as optical communication.

[0063] (Additional notes) Incidentally, in multicore fibers, crosstalk is likely to occur due to the small distance between cores. Therefore, it is desirable for optical signals with reduced crosstalk, which affects communication, to propagate.

[0064] Therefore, the present invention aims to provide an optical input / output device that can reduce crosstalk that affects communication.

[0065] To achieve the above objective, the optical input / output device of the present invention comprises: at least one multicore fiber including at least one transmitting core and at least one receiving core; a number of first transmitting single-core fibers equal to the total number of transmitting cores in all the multicore fibers; a number of first receiving single-core fibers equal to the total number of receiving cores in all the multicore fibers; a fan-in / fan-out device that optically couples each core at one end of each first transmitting single-core fiber with each of the transmitting cores, and optically couples each core at one end of each first receiving single-core fiber with each of the receiving cores; and a transmit / receive connector having a number of connector ports equal to the total number of first transmitting single-core fibers and first receiving single-core fibers, which are connected to the other end of each first transmitting single-core fiber and capable of optically coupling the core of each first transmitting single-core fiber with the transmit port of the transceiver, and which are connected to the other end of each first receiving single-core fiber and capable of optically coupling the core of each first receiving single-core fiber with the receive port of the transceiver.

[0066] With such an optical input / output device, when the core of each transmitting single-core fiber is optically connected to the transmit port of the transceiver, the optical signal transmitted from the transceiver's transmit port propagates to the transmitting core in the multi-core fiber via the transmitting single-core fiber. When the core of each receiving single-core fiber is optically connected to the transceiver's receive port, the optical signal received at the transceiver's receive port propagates to the receiving core via the receiving single-core fiber. Therefore, light propagates in opposite directions between the transmitting core and the receiving core in the multi-core fiber. Consequently, even if crosstalk occurs between the transmitting core and the receiving core, the light crosstalking from the transmitting core to the receiving core is suppressed from being received by the transceiver, and the light crosstalking from the receiving core to the transmitting core is suppressed from propagating to the destination transceiver. Therefore, the optical input / output device of the present invention can reduce crosstalk that affects communication.

[0067] Furthermore, in at least one of the multicore fibers, it is preferable that at least one of the core pairs adjacent to each other at the shortest distance is a transceiver-receiver core pair in which one is the transmit core and the other is the receive core.

[0068] Crosstalk tends to increase as the distance between cores decreases. Therefore, by having the shortest distance adjacent core pairs be the aforementioned transmit / receive core pairs, crosstalk affecting communication can be reduced compared to cases where all shortest distance adjacent core pairs are either transmit cores or receive cores.

[0069] In this case, it is preferable that in at least one of the multicore fibers, all of the core pairs adjacent to each other at the shortest distance are the transmitting and receiving core pairs.

[0070] This approach can further reduce crosstalk that affects communication.

[0071] Furthermore, it is preferable that the optical input / output device described in any of the above includes a plurality of multicore fibers, and that the cores of each of the first transmitting single-core fibers connected to a pair of adjacent connector ports are optically coupled to the transmitting cores of different multicore fibers, and that the cores of each of the first receiving single-core fibers connected to a pair of adjacent connector ports are optically coupled to the receiving cores of different multicore fibers.

[0072] In a transceiver, first transmitting optical fibers connected to adjacent transmitting connector ports and first receiving optical fibers connected to adjacent receiving connector ports tend to be optically coupled to adjacent transmitting ports and adjacent receiving ports, respectively. In a transceiver, crosstalk is generally likely to occur between the light emitted from adjacent transmitting ports and between the electrical signals that become this light, and between the light emitted from adjacent receiving ports and between the electrical signals that convert this light. However, even when such crosstalk occurs, in a transceiver, the cores of the pair of first transmitting single-core fibers that propagate the crosstalked light are coupled to the transmitting cores of different multi-core fibers, and the cores of the pair of first receiving single-core fibers that propagate the crosstalked light are coupled to the receiving cores of different multi-core fibers. Therefore, crosstalk between the optical signals propagating through the cores of the pair of first transmitting single-core fibers where the above-mentioned crosstalk occurs is suppressed in the multicore fiber, and crosstalk between the optical signals propagating through the cores of the pair of first receiving single-core fibers where the above-mentioned crosstalk occurs is suppressed in the multicore fiber. Consequently, crosstalk affecting communication can be reduced compared to cases where a pair of first transmitting single-core fibers connected to adjacent connector ports are coupled to the transmitting core of the same multicore fiber, or where a pair of first receiving single-core fibers connected to adjacent connector ports are coupled to the receiving core of the same multicore fiber.

[0073] Alternatively, it is preferable that the cores of each of the first transmitting single-core fibers connected to a pair of adjacent connector ports are optically coupled to a pair of transmitting cores in one multicore fiber other than the pair of cores adjacent to each other at the shortest distance, and the cores of each of the first receiving single-core fibers connected to a pair of adjacent connector ports are optically coupled to a pair of receiving cores in one multicore fiber other than the pair of cores adjacent to each other at the shortest distance.

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

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

[0076] This configuration suppresses crosstalk that affects communication, compared to cases where a receiving core is not located between the pair of transmitting cores described above, or where a transmitting core is not located between the pair of receiving cores described above.

[0077] Furthermore, the optical input / output device described in any of the above descriptions comprises a plurality of multicore fibers, each having a central core located in the center of the cladding which is either the transmitting core or the receiving core, and each multicore fiber having at least one transmitting core and at least one receiving core arranged around the central core, wherein the transmitting and receiving connector consists of a plurality of subconnectors, each having two or more of some of the connector ports, and each of the first transmitting single-core fibers or first receiving single-core fibers optically coupled to the central core of each multicore fiber is connected to the connector port of a specific subconnector, and each first transmitting single-core fiber connected to each transmitting core arranged around the central core of each multicore fiber and each first receiving single-core fiber connected to each receiving core arranged around the central core of each multicore fiber are preferably connected to the connector ports of subconnectors other than the specific subconnector.

[0078] Light propagating through the central core located in the center of the cladding is affected by crosstalk from each of the surrounding cores. Therefore, when a single-core fiber having a core that optically couples with the central core, as described above, is connected to a specific subconnector, and the specific subconnector is optically connected to a transceiver, it becomes easier to collect and connect light with a large crosstalk effect from the specific subconnector to a single transceiver. This makes it easier to perform appropriate processing of crosstalk in that transceiver.

[0079] Furthermore, it is preferable that all of the multicore fibers are longer than each of the first single-core fibers for transmitting and each of the first single-core fibers for receiving.

[0080] In optical communications, skew, which occurs when there is a difference in the transmission time of light propagating through each core, can be a problem. In multicore fibers, differences in the lengths of the cores are less likely to occur, thus reducing the likelihood of skew. On the other hand, in multiple single-core fibers, differences in the lengths of the cores are more likely to occur, making skew more likely. Therefore, by having all multicore fibers longer than each first transmitting single-core fiber and each first receiving single-core fiber, as described above, the proportion of single-core fiber transmission paths can be reduced. As a result, skew can be suppressed compared to the case where all multicore fibers are shorter than each first transmitting single-core fiber and each first receiving single-core fiber.

[0081] Furthermore, the optical input / output device described in any of the above further comprises: a housing that accommodates at least a portion of each of the first transmitting single-core fibers and each of the first receiving single-core fibers; second transmitting single-core fibers, the same number as the first transmitting single-core fibers, each having a core that is optically coupled to the core at the other end of each of the first transmitting single-core fibers and optically coupled to the transmitting port of the transceiver, with at least a portion of them located outside the housing; and second receiving single-core fibers, the same number as the first receiving single-core fibers, each having a core that is optically coupled to the core at the other end of each of the first receiving single-core fibers and optically coupled to the receiving port of the transceiver, with at least a portion of them located outside the housing.The device also assumes a plurality of single-core fiber pairs, each consisting of a plurality of first single-core fibers, each consisting of a first transmitting single-core fiber and each of the first receiving single-core fibers; and a plurality of second single-core fibers, each consisting of a second transmitting single-core fiber and each of the second receiving single-core fibers, which are optically coupled to each of the first single-core fibers. In this case, it is preferable that in at least one of the multiple single-core fiber pairs, the optical confinement force of the first single-core fiber is greater than that of the second single-core fiber, and the outer diameter of the cladding of the second single-core fiber is greater than that of the cladding of the first single-core fiber. Alternatively, in this case, the first single-core fiber has the core, a cladding surrounding the core with a lower refractive index than the core, and a trench layer surrounding the core and the cladding with a lower refractive index than the cladding, and the second single-core fiber has the core, a cladding surrounding the core with a lower refractive index than the core, but does not have a trench layer surrounding the core and the cladding with a lower refractive index than the cladding, and the outer diameter of the cladding of the second single-core fiber is greater than that of the cladding of the first single-core fiber.

[0082] In this case, each single-core fiber pair consists of either a first transmitting single-core fiber and a second transmitting single-core fiber, or a first receiving single-core fiber and a second receiving single-core fiber. Because the first transmitting single-core fiber and the first receiving single-core fiber are routed within the limited space of the housing, the first transmitting single-core fiber and the first receiving single-core fiber located inside the housing tend to be bent with a greater curvature than the second transmitting single-core fiber and the second receiving single-core fiber located outside the housing. Therefore, if the optical confinement force of the first single-core fiber assumed as described above is greater than the optical 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. Furthermore, if the optical confinement force of the second single-core fiber is smaller than that of the first single-core fiber, the refractive index of the core of the second single-core fiber can be made smaller than that 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 its refractive index can be reduced, and the loss due to Rayleigh scattering can be reduced in the second single-core fiber compared to the first single-core fiber. Incidentally, the second single-core fiber, which is located outside the housing, is generally longer than the first single-core fiber because it is connected to a transceiver located at a distance from the input / output device. Therefore, by reducing the loss due to Rayleigh scattering in the second single-core fiber compared to the first single-core fiber, optical loss can be reduced in the optical input / output device.

[0083] Furthermore, 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. While optical fibers with a trench layer can suppress bending loss as described above, they tend to have greater transmission loss over long distances than optical fibers without a trench layer. Therefore, as described above, by having the second single-core fiber, which tends to be longer than the first single-core fiber, lack a trench layer, the transmission loss of light in the second single-core fiber can be suppressed, thereby reducing the optical loss in optical input / output devices.

[0084] Furthermore, because the outer diameter of the cladding of the first single-core fiber is smaller than that of the cladding of the second single-core fiber, the fracture coefficient of the first single-core fiber can be made smaller than that of the second single-core fiber. Therefore, even if the first single-core fiber is bent with a larger curvature than the second single-core fiber, the fracture of the first single-core fiber can be suppressed.

[0085] Furthermore, the core of each of the first transmitting single-core fibers and the transmitting port of the transceiver may be optically coupled, and the core of each of the first receiving single-core fibers and the receiving port of the transceiver may be optically coupled.

Claims

1. Multiple multicore fibers, each including at least one transmitting core and at least one receiving core, A first single-core fiber for transmission, the same number as the total number of transmission cores in all of the multi-core fibers, A first receiving single-core fiber, the same number as the total number of receiving cores in all of the multi-core fibers, A fan-in / fan-out device comprising the same number of fan-in / fan-out devices as all of the multicore fibers, wherein each fan-in / fan-out device corresponding to a multicore fiber optically couples each core at one end of the same number of first transmitting single-core fibers as the number of transmitting cores of the multicore fiber with each of the transmitting cores of the multicore fiber, and optically couples each core at one end of the same number of first receiving single-core fibers as the number of receiving cores of the multicore fiber with each of the receiving cores of the multicore fiber. A second single-core transmission fiber, the same number as the first single-core transmission fiber, the second single-core transmission fiber connected to the other end of each of the first single-core transmission fibers, and optically coupling the core of each of the first single-core transmission fibers with the transmission port of the transceiver, The system further comprises the same number of second receiving single-core fibers as the first receiving single-core fibers, each of which is connected to the other end of the first receiving single-core fiber and optically couples the core of each first receiving single-core fiber with the receiving port of the transceiver. The first transmitting single-core fiber and the first receiving single-core fiber are bundled together as a ribbon cable, and the second transmitting single-core fiber and the second receiving single-core fiber are bundled together as a ribbon cable. An optical input / output device characterized by the following features.

2. A housing that houses at least a portion of each of the first transmitting single-core fibers and each of the first receiving single-core fibers, In at least one of a plurality of single-core fiber pairs, each consisting of a plurality of first single-core fibers comprising a first transmitting single-core fiber and a plurality of first receiving single-core fibers, and a plurality of second single-core fibers comprising a second transmitting single-core fiber and a plurality of second receiving single-core fibers optically coupled to each of the first single-core fibers, the optical confinement force of the first single-core fiber is greater than the optical confinement force of the second single-core fiber, and the outer diameter of the cladding of the second single-core fiber is greater than the outer diameter of the cladding of the first single-core fiber. The optical input / output device according to feature 1.

3. In at least one of a plurality of single-core fiber pairs, each consisting of a plurality of first single-core fibers comprising a plurality of first single-core fibers each comprising a first transmitting single-core fiber and a plurality of first receiving single-core fibers, and a plurality of second single-core fibers each comprising a second transmitting single-core fiber and a plurality of second receiving single-core fibers optically coupled to each of the first single-core fibers, the first single-core fiber having the core, a cladding surrounding the core with a lower refractive index than the core, and a trench layer surrounding the core and the cladding with a lower refractive index than the cladding, the second single-core fiber having the core, a cladding surrounding the core with a lower refractive index than the core, and not having a trench layer surrounding the core and the cladding with a lower refractive index than the cladding, and the outer diameter of the cladding of the second single-core fiber being greater than the outer diameter of the cladding of the first single-core fiber The optical input / output device according to feature 1.

4. A plurality of multicore fibers, each including at least one transmitting core and at least one receiving core, A first single-core fiber for transmission, the same number as the total number of transmission cores in all of the multi-core fibers, A first receiving single-core fiber, the same number as the total number of receiving cores in all of the multi-core fibers, A fan-in / fan-out device comprising the same number of fan-in / fan-out devices as all of the multicore fibers, wherein each fan-in / fan-out device corresponding to a multicore fiber optically couples each core at one end of the same number of first transmitting single-core fibers as the number of transmitting cores of the multicore fiber with each of the transmitting cores of the multicore fiber, and optically couples each core at one end of the same number of first receiving single-core fibers as the number of receiving cores of the multicore fiber with each of the receiving cores of the multicore fiber. A transceiver connector having the same number of connector ports as the total number of first transmit single-core fibers and first receive single-core fibers, each of which is connected to the other end of each first transmit single-core fiber and is capable of optically coupling the core of each first transmit single-core fiber with the transmit port of the transceiver, and each of which is connected to the other end of each first receive single-core fiber and is capable of optically coupling the core of each first receive single-core fiber with the receive port of the transceiver, Each of the multicore fibers comprises a portion of the multicore fiber, the same number of fan-in / fan-out devices as the multicore fiber, and a housing that houses each of the first transmitting single-core fiber and the first receiving single-core fiber. The connector port of the aforementioned transmit / receive connector is A single-core transmit connector and a single-core receive connector fixed to the housing, comprising: one transmit connector port and the same number of single-core transmit connectors as the first transmit single-core fiber; and one receive connector port and the same number of single-core receive connectors as the first receive single-core fiber; or The number of first single-core fibers for transmission and the number of first single-core fibers for reception are the same, and the connector ports of the transmit / receive connector are, A dual transceiver connector fixed to the housing, having one transmit connector port and one receive connector port, and consisting of the same number of dual transceiver connectors as the first single-core fiber for transmission. An optical input / output device characterized by the following features.

5. The cores of each of the first single-core transmitting fibers connected to a pair of adjacent connector ports are optically coupled to the transmitting cores of different multi-core fibers, respectively. The cores of each 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. The optical input / output device according to feature 4.

6. The cores of each of the first single-core transmit fibers connected to a pair of adjacent connector ports are optically coupled to a pair of transmit cores in one multi-core fiber that are not adjacent to each other by the shortest distance. The cores of each of the first receiving single-core fibers connected to a pair of adjacent connector ports are optically coupled to a pair of receiving cores in a single multi-core fiber that are not adjacent to each other at the shortest distance. The optical input / output device according to feature 4.

7. Between the pair of transmitting cores in the multicore fiber, the cores of each of the first transmitting single-core fibers connected to a pair of adjacent connector ports are optically coupled, and the receiving core is located there. Between the pair of receiving cores in the multicore fiber, the cores of each of the first receiving single-core fibers connected to a pair of adjacent connector ports are optically coupled, and the transmitting core is located therein. The optical input / output device according to feature 6.

8. 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 transceiver-receiver core pair in which one is the transmit core and the other is the receive core. The optical input / output device according to any one of claims 1 to 7.

9. In at least one of the multicore fibers, all of the core pairs adjacent to each other at the shortest distance are the transmit / receive core pairs. The optical input / output device according to feature 8.

10. All of the multicore fibers are longer than each of the first transmitting single-core fibers and each of the first receiving single-core fibers. The optical input / output device according to any one of claims 1 to 9.

11. The core of each of the first transmitting single-core fibers and the transmitting port of the transceiver are optically coupled, and the core of each of the first receiving single-core fibers and the receiving port of the transceiver are optically coupled. The optical input / output device according to any one of claims 1 to 10.

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