JP6654595B2 - Optical fiber communication system using multi-core optical fiber and core identification method - Google Patents

Description

  The present invention relates to an optical fiber communication system and a core identification method using a multi-core optical fiber having a plurality of cores in one optical fiber among spatial multiplexing techniques for increasing the transmission capacity of the optical fiber.

  A multi-core optical fiber is an optical fiber that has multiple cores in a single clad.Compared to a conventional optical fiber that has only a single core, multiple cores are multiplexed in the space inside the clad. It can be said that this is an optical fiber using spatial multiplexing technology. Therefore, in a multi-core optical fiber, the transmission capacity can be increased by the number of cores multiplexed in a single clad. Various proposals and studies have been made on the structure of the multi-core optical fiber (for example, Patent Document 1) and the manufacturing method (for example, Patent Document 2), and practical application is expected in the near future.

  In a multi-core optical fiber, a part called a marker is usually provided to identify a plurality of cores arranged in a single clad (for example, FIG. 9 of Non-Patent Document 1). Further, connection of optical fibers with each other using such a marker has been studied (for example, Patent Document 3).

Japanese Patent No. 5808767 JP 2015-160784 A International Publication No. 2012/121027

T. Hayashi, T. Taru, O. Shimakawa, T. Sasaki, and E. Sasaoka, "Design and fabrication of ultra-low crosstalk and low-loss multi-core fiber," Opt. Express 19, 16576-16592 (2011 )

  In a multi-core optical fiber provided with a marker as described above, the number of cores that can be accommodated in a clad having a limited cross-sectional area decreases due to the presence of the marker. Further, when connecting the optical fibers, in order to align the position of the marker on the connecting surface of the optical fibers, it is necessary to twist the optical fibers to be connected at a maximum of 180 °. Such twisting not only increases the possibility that the optical fiber itself is broken, but also increases the time required for fusion splicing of the connection surface. Further, in the case of fusion splicing with a twist, a rotational stress due to the twist is applied to the connection point, so that there is a high possibility that the connection point is broken, which causes a problem in long-term reliability.

  On the other hand, if the multi-core optical fiber used for the optical fiber transmission line is made markerless in order to cope with the above-described problem, it may not be possible to uniquely identify each core from the state of the cross section of the optical fiber. That is, when a markerless multi-core optical fiber is used, the correspondence between each core at the input end of the optical fiber transmission line and each core at the output end may be unclear. However, for the operation management of the optical fiber communication system using the multi-core optical fiber, it is necessary to grasp the correspondence between each core at the input end and each core at the output end.

  The present invention has been made in view of the above problems. The present invention relates to a technology for identifying, after introducing the system, which core at the output end of an optical fiber transmission line corresponds to which core at the input end in an optical fiber communication system using a multi-core optical fiber. It is intended to provide.

An optical fiber communication system according to an aspect of the present invention is an optical fiber communication system including a transmission device and a reception device at an input end and an output end of an optical fiber transmission line, respectively, wherein the optical fiber transmission line is a markerless multi-core. The multi-core optical fiber is composed of a plurality of cores, each of which has an individual terminal device connected to each core at each of the input end and the output end. Having a plurality of cores arranged rotationally symmetric with respect to a central axis, the transmitting device is configured such that an optical signal for core identification is input to at least one of the plurality of cores at the input end, Control means for controlling transmission of an optical signal, wherein the receiving device outputs the optical signal output from the multi-core optical fiber at the output end. Acquisition means for acquiring the reception result of the optical signal for identification, and based on the reception result, each of the plurality of cores used at the output end corresponds to any core used at the input end Identification means for performing core identification for identifying whether or not the optical signal for core identification is input to the plurality of cores one at a time at the input end. The core identification is performed based on an output order of the core identification optical signals output from each of the plurality of cores at the output end .

  According to the present invention, in an optical fiber communication system using a multi-core optical fiber, it is possible to identify, after introduction of the system, which core at the output end of the optical fiber transmission line corresponds to which core at the input end. Will be possible.

Diagram showing a schematic configuration example of an optical fiber communication system Diagram showing an example of core arrangement in the cladding of a multi-core optical fiber FIG. 4 is a diagram showing an example of an input / output end and an intermediate state of an optical fiber transmission line. Diagram showing an example of core identification of a multi-core optical fiber Diagram showing an example of a protocol for core identification Diagram showing a schematic configuration example of an optical fiber communication system FIG. 3 is a diagram illustrating an example of core identification of a multi-core optical fiber (Embodiments 2 and 3). FIG. 9 is a diagram illustrating a schematic configuration example of an optical fiber communication system (Embodiment 5). Diagram showing an example of core identification of a multi-core optical fiber (Embodiment 5) Diagram showing an example of a protocol for core identification (Embodiment 5) FIG. 9 is a diagram illustrating a schematic configuration example of an optical fiber communication system (Embodiment 6).

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the following drawings, components that are not necessary for the description of the embodiment are omitted from the drawings.

[Embodiment 1]
<Optical fiber communication system>
FIG. 1 is a diagram illustrating a schematic configuration example of the optical fiber communication system according to the first embodiment. The multi-core optical fiber transmission line (hereinafter, referred to as “optical fiber transmission line”) 1 shown in FIG. 1 includes a multi-core optical fiber and an optical amplifier. The optical amplifier may be a multi-core optical amplifier or a single-core amplifier in parallel with the number of cores of the multi-core optical fiber (the number of cores N). The number of cores N is an integer of 2 or more, and each embodiment will be described below with an example where N = 4 (ie, 4 cores).

  In the present embodiment, the optical fiber communication system includes a transmitting station 10 (transmitting device) at the input end of the optical fiber transmission line 1 and a receiving station 20 (receiving device) at the output end. The multi-core optical fiber that forms the optical fiber transmission line 1 has a plurality of (N) cores in which individual terminal stations are connected to each core at each of an input end and an output end. The transmitting station 10 includes terminal equipments (hereinafter, referred to as “terminals”) Tx1 to Tx4 equal to the number N of cores of the multicore optical fiber, and a single / multi conversion unit for coupling a single core to the multicore. 12 and a control unit 11. Each of the terminal stations Tx1 to Tx4 is a transmitting terminal apparatus for a single-core optical fiber transmission line, and is used for transmitting an optical signal. The terminal stations Tx1 to Tx4 are connected to each core of the multi-core optical fiber constituting the optical fiber transmission line 1. The control unit 11 functions as a common control unit for the terminal stations Tx1 to Tx4, and controls each terminal station.

  The receiving station 20 includes a number of terminal stations Rx1 to Rx4 equal to the number N of cores of the multi-core optical fiber, a multi-to-single converter 22 for coupling the multi-core to a single core, and an output from the multi-to-single converter 22. An optical switch 23 for switching connection with the terminal stations Rx1 to Rx4 and a control unit 21 are provided. Each of the terminal stations Rx1 to Rx4 is a receiving terminal device for a single-core optical fiber transmission line, and is used for receiving an optical signal. The terminal stations Rx1 to Rx4 are connected to respective cores of a multi-core optical fiber constituting the optical fiber transmission line 1. The control unit 21 functions as a common control unit for the terminal stations Rx1 to Rx4 and the optical switch 23, and controls each terminal station and the optical switch 23. In the present embodiment, the control units 11 and 21 identify each core of the multi-core optical fiber as described later.

<Structure of multi-core optical fiber>
Next, the structure and effects of the multi-core optical fiber according to the present embodiment and the identification of the core of the multi-core optical fiber will be described with reference to FIGS. In the present embodiment, the optical fiber transmission line 1 is configured by a marker-less (having no marker) multi-core optical fiber. The multi-core optical fiber is characterized in that it has a plurality of cores arranged rotationally symmetrically with respect to the center axis of the clad in the cross section of the multi-core optical fiber.

  FIG. 2A shows a comparative example in which the core arrangement in the clad is trapezoidal and the core arrangement is rotationally asymmetric with respect to the center axis of the clad. To connect two optical fibers in such a case, it is necessary to twist the optical fibers at a maximum of 180 ° with respect to the center axis of the clad. Even when a twist is applied to both optical fibers to be connected, it is necessary to twist each optical fiber by up to 90 °.

  When the two optical fibers to be connected have a configuration as shown in FIG. 2A, there are the following problems. The centering operation for aligning the central axes for the fusion splicing of the optical fiber is started after the optical fiber is twisted. For this reason, the time required for fusion splicing increases, and the time required for laying and maintaining the optical fiber transmission line increases, leading to an increase in cost. Furthermore, a large angle twist is applied to the optical fiber, so that the optical fiber itself is broken, or a rotational stress is generated at the fusion splicing point, thereby causing the fracture of the splicing point. Problems also arise.

  FIG. 2B shows a comparative example in which the core arrangement in the clad has a square shape, the core arrangement is rotationally symmetric with respect to the center axis of the clad, and a marker is present. I have. In the case of connecting two optical fibers in the case of FIG. 2B, it is necessary to apply a twist of up to 180 ° to the optical fiber as in the case of FIG. 2A.

  FIG. 2C illustrates the structure of the optical fiber according to the present embodiment, in which the core arrangement in the clad is rotationally symmetric with respect to the center axis of the clad and has no marker. In this case, when connecting two optical fibers, if a twist of at most 45 ° is applied to the optical fibers, the positions of the cores on the connecting surfaces of the two optical fibers can be matched. In the case where both optical fibers are twisted, the required twist angle is half (ie, 22.5 ° at the maximum).

  Therefore, according to the structure of the optical fiber according to the present embodiment, a twist that needs to be added to the optical fiber when two optical fibers are connected is different from the comparative example illustrated in FIGS. 2A and 2B. Is greatly reduced. For this reason, the time required for fusion splicing of optical fibers can be reduced. In addition, it is possible to shorten the time required for construction and maintenance, and to reduce the possibility of fiber breakage. This leads to an improvement in the reliability of the optical fiber.

  As shown in FIG. 2 (C), when a multi-core optical fiber having rotational symmetry with respect to the core arrangement and having no marker is used for the optical fiber transmission line 1, the cladding is changed from the state of the cross section of the optical fiber. Each core within can not be uniquely identified.

  Here, FIG. 3A shows an input / output end of the optical fiber transmission line and a state in the middle when a marker is present in the optical fiber. The presence of the marker makes it possible to uniquely identify each core at an arbitrary position on the transmission line from the state of the cross section of the optical fiber. On the other hand, FIG. 3B shows an input / output end and an intermediate state of an optical fiber transmission line using a multi-core optical fiber having the structure according to the present embodiment. In this case, it is not possible to identify which of the cores X1 to X4 at the input end corresponds to each of the cores Y1 to Y4 at a position in the middle of the transmission line from the state of the cross section of the optical fiber. Further, it is not possible to identify which of the cores X1 to X4 corresponds to the cores Z1 to Z4 at the output end from the state of the cross section of the optical fiber.

  Therefore, in the present embodiment, as described in detail below, each of the plurality of cores specified (used) at the output end of the optical fiber transmission line 1 is replaced with any of the cores specified (used) at the input end. The transmitting station has a function (core identification function) for automatically performing core identification for identifying whether the input terminal corresponds to a plurality of cores (that is, determining the correspondence between a plurality of cores at an input end and a plurality of cores at an output end). 10 and the receiving station 20.

<Core identification method for multi-core optical fiber>
An example of a method for identifying a core of a multi-core optical fiber will be described with reference to FIG. FIG. 4A shows an initial state immediately after the introduction of the optical fiber communication system using the multi-core optical fiber. In FIG. 4 (A), each terminal on the transmitting side (transmitting station 10) and the receiving side (receiving station 20) has a multi-core optical fiber constituting the optical fiber transmission line 1 at an input end and an output end of the optical fiber transmission line. It is connected to one of a plurality of cores in the fiber. In this initial state, the correspondence between the core (transmitting core) specified (used) on the transmitting side and the core (receiving core) specified (used) on the receiving side is unknown. For this reason, terminal stations to which the same number is assigned on the transmitting side and the receiving side are not necessarily connected to each other.

  In the optical fiber communication system of the present embodiment, the correspondence between the transmission core and the reception core is determined, and as an example, the terminal stations assigned the same number on the transmission side and the reception side communicate with each other. Perform initial settings. Specifically, initial settings are performed so that the terminal stations Tx1 and Rx1, the terminal stations Tx2 and Rx2, the terminal stations Tx3 and Rx3, the terminal stations Tx4 and Rx4 perform communication, respectively.

  First, as shown in FIG. 4B, the control unit 11 on the transmitting side causes only one of the terminal stations Tx1 to Tx4 to transmit an optical signal for core identification. Here, as an example, only the terminal station Tx1 transmits a signal. On the receiving side, the control unit 21 determines which of the terminal stations Rx1 to Rx4 has received (detected) the signal transmitted from Tx1. The control unit 21 determines the terminal station that has received the optical signal for core identification based on, for example, whether or not an LOS (Loss of Signal) alarm occurs when there is no signal input to the terminal stations Rx1 to Rx4. Can be determined. Specifically, the control unit 21 can determine, from Rx1 to Rx4, the terminal station in which the LOS alarm has not occurred to be the terminal station that has received the signal. FIG. 4B shows an example in which the terminal station Rx3 has received a signal.

  Next, the control unit 11 on the transmitting side causes only the terminal station Tx2 to transmit an optical signal for core identification, and the control unit 21 on the receiving side determines the terminal station that has received the signal. By repeating such processing for all the terminal stations Tx1 to Tx4 (that is, for all the cores), it is possible to determine which of the terminal stations Rx1 to Rx4 is connected to each of the terminal stations Tx1 to Tx4. . As a result, it is possible to determine the correspondence between the transmission core and the reception core.

  As described above, in the present embodiment, the control unit 11 on the transmission side controls the transmission of the optical signal by the terminal stations Tx1 to Tx4, and controls the plurality of (all) cores at the input end of the optical fiber transmission line 1. The optical signals for the core identification are sequentially input one by one. The control unit 21 on the receiving side obtains, from the terminal stations Rx1 to Rx4, reception results of optical signals for core identification output from the multi-core optical fiber at the output end of the optical fiber transmission line 1. Further, based on the obtained reception result, the control unit 21 associates each of the plurality of (N) cores used at the output end of the optical fiber transmission line 1 with any of the cores used at the input end. Identify what to do. Specifically, the control unit 21 performs core identification at the output end of the optical fiber transmission line 1 based on the output order of the core identification optical signals output from each of the (N) cores. .

  The control unit 11 on the transmission side controls the transmission of the optical signal by the terminal stations Tx1 to Tx4, and performs the core identification for only one of the plurality of cores at the input end of the optical fiber transmission line 1. May be input. In this case, the control unit 21 on the receiving side determines the relative position of the plurality of cores with respect to the position of the core at the output end of the optical fiber transmission line 1 where the optical signal for core identification is output in the cross section of the multi-core optical fiber. Core identification may be performed based on a strategic position. For example, using the example shown in FIG. 3B, when the optical signal for core identification is output from the core Z1, the control unit 21 determines the relative position of the cores Z2 to Z4 with respect to the position of the core Z1. It is possible to perform core identification for the cores Z2 to Z4 based on the strategic position.

  Accordingly, the control unit 11 on the transmission side transmits the terminal stations Tx1 to Tx1 to input the core identification optical signal to at least one of the plurality of (N) cores at the input end of the optical fiber transmission line 1. 4 may be used to control the transmission of the optical signal. By such a method, the receiving station 20 can automatically perform the core identification. That is, by the above-described processing in the transmitting station 10 and the receiving station 20, after the introduction of the optical fiber communication system, it is possible to identify which core at the output end of the optical fiber transmission line 1 corresponds to which core at the input end. Will be possible.

  When the determination of the correspondence between the transmission core and the reception core is completed, the control unit 21 on the reception side, as shown in FIG. The switching setting of the optical switch 23 is performed so that the connection is made (switch setting function). This setting is performed for the terminal stations Tx1 to Tx4 and the terminal stations Rx1 to Rx4 through a predetermined combination of terminal stations (transmitting terminal station apparatus and receiving terminal station apparatus) via a plurality of cores of a multi-core optical fiber. It is an example of a switching setting for connection. As a result of such a switching setting, the terminal station Tx1 and the terminal station Rx1, the terminal station Tx2 and the terminal station Rx2, the terminal station Tx3 and the terminal station Rx3, and the terminal station Tx4 and the terminal station Rx4 are connected via the optical switch 23. .

  When performing the above-described core identification, there is a possibility that information (control information) needs to be exchanged between the control unit 11 of the transmitting station 10 and the control unit 21 of the receiving station 20. In this case, the control units 11 and 21 use another line, an opposite line, or an optical supervisory channel (OSC, an optical signal used for monitoring a transmission line using a wavelength outside the band of the wavelength multiplexed signal). Thus, it is possible to exchange such information. In addition, as described below, by defining a protocol for core identification in advance, there is no need to exchange between the control units 11 and 21, and only transmission of a signal from the transmission side to the reception side is performed. It is also possible to complete the core identification.

<Protocol for core identification>
FIG. 5 is a diagram illustrating an example of a core identification protocol according to the present embodiment. In this example, the control unit 11 of the transmitting station 10 performs the core identification by the terminal stations Tx1 to Tx4 according to a predetermined protocol that defines the input order and the input timing of the core identification optical signals to a plurality of cores. Controls the transmission of optical signals.

  In the present protocol, before the start of core identification, the control unit 11 of the transmitting station 10 cuts off all optical signals transmitted from the terminal stations Tx1 to Tx4, thereby allowing the receiving station 20 to transmit a signal from any core. Make it unreceivable. Thereby, the core identification function in the control units 11 and 21 is reset. When the reset of the core identification function is completed, the control unit 11 transmits optical signals from all of the terminal stations Tx1 to Tx4. When confirming the reception of the signals by all of the terminal stations Rx1 to Rx4, the control unit 21 interprets this as the start of the core identification.

  Next, the control unit 11 causes each terminal station to transmit an optical signal in the order of the terminal stations Tx1 to Tx4. The control unit 21 determines the correspondence between the transmitting core and the receiving core based on the reception results of the optical signals by the terminal stations Rx1 to Rx4. Thereby, the execution of the core identification function according to the present protocol in the transmitting station 10 and the receiving station 20 is completed. After that, the control unit 21 performs switching setting of the optical switch 23 based on the determination result of the correspondence between the transmission core and the reception core.

  As described above, according to the present embodiment, in an optical fiber communication system using a multi-core optical fiber, it is determined which core at the output end of the optical fiber transmission line 1 corresponds to which core at the input end. It can be identified after introduction.

  During operation of the optical fiber transmission line 1, the optical fiber may be broken. In this case, in the connection repair work of the fiber required for the broken portion, as shown in FIG. 2C, the connection with a small twist angle can be realized at the time of connecting the optical fiber. It is possible to improve and shorten the repair time. After the connection repair work is completed, the correspondence between the transmission core and the reception core in the optical fiber transmission line 1 becomes unknown again, but by using the above-described core identification function of the transmission station 10 and the reception station. The system can be restarted without any problem.

  Also, in FIG. 1, the optical switch 23 is provided on the receiving side (receiving station 20), but the optical switch may be provided on the transmitting side (transmitting station 10), or on both the transmitting side and the receiving side. It may be provided. FIG. 6A shows a schematic configuration example of an optical fiber communication system in which an optical switch is arranged on the transmission side, and FIG. 6B shows an example in which the optical switch is arranged on both the transmission side and the reception side. 2 shows a schematic configuration example of an optical fiber communication system in such a case. When the optical switch 13 is arranged on the transmission side, the optical switch 13 is arranged between the terminal stations Tx1 to Tx4 and the single / multi conversion unit 15, as shown in FIGS. As described above, when the optical switch 13 is provided, the control unit 11 may perform the switching setting of the optical switch 13 based on the feedback from the receiving station 20 including the result of the core identification by the control unit 21. . If an optical switch is placed on both the transmitting side and the receiving side, even if one of the optical switches fails, the switching setting can be made using the other optical switch, so the reliability of the system Improvements are possible.

[Embodiment 2]
In the first embodiment, the terminal stations Tx1 to Tx4 sequentially transmit optical signals to the optical fiber transmission line 1, thereby enabling the receiving station 20 to identify the core. In the present embodiment, a method will be described in which the terminal stations Tx1 to Tx4 transmit optical signals each including a unique test pattern, thereby enabling the receiving station 20 to identify the core.

  Specifically, the control unit 11 on the transmission side causes the plurality of cores at the input end of the optical fiber transmission line 1 to input optical signals including different test patterns as optical signals for core identification. On the other hand, the control unit 21 on the receiving side performs core identification based on the detection result of the test pattern included in the optical signal for core identification output from each of the plurality of cores at the output end of the optical fiber transmission line 1. . In this method, even if all the terminal stations of the transmitting station 10 transmit the optical signal at the same time, the core identification at the receiving station 20 is possible. In the present embodiment and embodiments 3 to 7 to be described later, description of portions common to the first embodiment will be omitted, and portions different from the first embodiment will be mainly described.

  FIG. 7A is a diagram illustrating an example of core identification according to the present embodiment. As shown in FIG. 7A, the control unit 11 of the transmitting station 10 instructs each of the terminal stations Tx1 to Tx4 to transmit an optical signal (test pattern signal) including a test pattern unique to each terminal station. . For example, an orthogonal random sequence is used as a test pattern different for each terminal station. The test pattern is determined in advance for each terminal station of the transmitting station 10, and may be held in advance by each terminal station, or may be stored in advance by the control unit 11 and the test pattern used for each terminal station. You may instruct. Further, the receiving station 20 (the terminal stations Rx1 to Rx4 or the control unit 21) knows in advance a test pattern used for core identification.

  The terminal stations Rx1 to Rx4 of the receiving station 20 identify the terminal station of the transmission source of the signal among the terminal stations Tx1 to Tx4 based on the received test pattern signal, and transmit identification information indicating the identified terminal station. Output to the control unit 21. Alternatively, the terminal stations Rx1 to Rx4 may output the test pattern included in the received test pattern signal to the control unit 21, and the control unit 21 may identify the terminal station that is the source of each test pattern signal. In any case, the control unit 21 determines the correspondence between the transmission core and the reception core based on the identification result of the terminal stations Tx1 to Tx4, and performs the switching setting of the optical switch 23 as in the first embodiment. . Thus, the core identification in the receiving station 20 is completed.

  In the above-described procedure, it is not necessary to exchange information between the control units 11 and 21. However, when a communication line is secured between the control units 11 and 21, a test pattern used for core identification is used. Communication for setting may be performed between the control units 11 and 21. In this case, it is possible to realize the core identification using an arbitrary test pattern after the system is introduced.

[Embodiment 3]
Embodiments 1 and 2 show an example in which an optical fiber (FIG. 2C) having rotational symmetry with respect to the core arrangement and having each core arranged on concentric circles is used for the optical fiber transmission line 1. However, it is also possible to use an optical fiber in which a core is arranged on the central axis of the cladding. In the present embodiment, an example of a core identification function applied when an optical fiber having a core disposed on the central axis of a clad is used for the optical fiber transmission line 1 will be described.

  FIG. 7B is a diagram illustrating a schematic configuration example of the optical fiber communication system according to the present embodiment. In the multi-core optical fiber used in the optical fiber transmission line 1 of the present embodiment, a core (center core) is also arranged on the center axis of the clad. The position of the central core does not change even when the optical fiber is rotated about the central axis of the clad. For this reason, regarding the central core, the correspondence between the core specified on the transmission side and the core specified on the reception side is fixed, and the transmission side and the reception side can uniquely identify the core.

  In the present embodiment, as shown in FIG. 7B, the transmitting station 10 is further provided with a terminal station Tx5 connected to the central core, and the receiving station 20 is provided with a terminal station Tx connected to the central core. Rx5 is further provided. Note that the terminal stations Tx5 and Rx5 are connected without passing through the optical switch 23 because there is no need to identify the core. The terminal stations Tx5 and Rx5 each have a function of a control unit. In the present embodiment, the terminal station Tx5 controls the terminal stations Tx1 to Tx4, which are other terminal stations, and the terminal station Rx5 controls the terminal stations Rx1 to Rx4, which are the other terminal stations. The core identification function according to the embodiment is realized. As the core identification method, any of the methods described in the first and second embodiments may be adopted.

  Further, in the present embodiment, the connection between the transmitting station 10 and the receiving station 20 via the central core is guaranteed before the core identification function is executed. Therefore, information is exchanged between the transmitting station 10 and the receiving station 20 using the central core (for example, the control unit 11 receives control information used for core identification using the central core). Station 20). In transmitting information from the receiving station 20 to the transmitting station 10, a transmission path for transmitting an optical signal from the receiving station 20 to the transmitting station 10 that is opposed to the optical fiber transmission line 1 (provided in parallel). (Not shown) may be used. In transmitting information, signal overhead may be used, or OSC may be used.

  In the present embodiment, as shown in FIG. 5 of the first embodiment, it is also possible to complete the core identification without exchanging a control signal or the like between the transmitting station 10 and the receiving station 20. However, each time the terminal station Rx5 receives a signal by any of the terminal stations Rx1 to Rx4, the terminal station Rx5 feeds back the determination result to the terminal station Tx5, and the terminal station Tx5 checks the feedbacked determination result, Optical signals may be transmitted from the terminal stations Tx1 to Tx4. As a result, core identification with fewer failures can be realized.

[Embodiment 4]
ITU-T G. In the 709 standard, the interface and overhead of terminal stations in an optical transmission network (OTN) are standardized, and SAPI / DAPI are used as identifiers for distinguishing transmitting and receiving terminal apparatuses from other apparatuses in the network. (Source Access Point Identifier / Destination Access Point Identifier) is defined. In this embodiment, an example in which the SAPI / DAPI is used for core identification in the first to third embodiments will be described.

  In the present embodiment, as the configuration of the optical fiber communication system, any of the configurations shown in FIGS. 1, 6A and 6B can be adopted, but the configuration of FIG. 6B will be described. . SAPI corresponds to the identifier of the source terminal device (terminal stations Tx1 to Tx4), and DAPI corresponds to the identifier of the destination terminal device (terminal stations Rx1 to Rx4). In the present embodiment, similarly to the first embodiment, the terminal stations assigned the same number (terminal station Tx1 and terminal station Rx1, terminal station Tx2 and terminal station Rx2, terminal station Tx3 and terminal station Rx3, and terminal station Tx4. The terminal station Rx4) is determined in advance as a combination of terminal stations that perform communication. The two terminal stations of each combination know in advance the identifier of the own device and the identifier of the corresponding device (that is, SAPI and DAPI). In the present embodiment, for example, SAPI and DAPI may be included in the optical signals for core identification transmitted from the terminal stations Tx1 to Tx4, respectively. The control unit 21 may perform core identification based on SAPI and DAPI included in an optical signal for core identification output from each of the plurality of cores at the output end of the optical fiber transmission line 1.

  In a state where the core identification function is not executed, each terminal station of the transmitting station 10 and each terminal station of the receiving station 20 are not necessarily connected in a correct combination. Each terminal of the transmitting station 10 and each terminal of the receiving station 20 exchange optical signals including the SAPI and the DAPI to detect whether or not the connection of the correct combination is made, and the connection of the correct combination is established. If not performed, it is transmitted to the control units 11 and 21. The control units 11 and 21 perform the switching setting of the optical switches 13 and 23 so as to change the connection of the terminal station in which the connection of the correct combination is not performed. By repeating such a procedure, each terminal station of the transmitting station 10 and each terminal station of the receiving station 20 can be connected in a correct combination.

  Note that the control units 11, 21 instead of the terminal stations Tx1 to Tx4 and Rx1 to 4 know SAPIs and DAPIs corresponding to all the terminal stations in advance, and use the SAPIs and DAPIs to realize the above-described procedure. Is also good.

[Embodiment 5]
In the first to fourth embodiments, for each of the transmitting side and the receiving side, a configuration is adopted in which the terminal stations connected to the optical fiber transmission line 1 are installed in the same place, but they are installed in different places. A configuration in which the connected terminal stations are connected to the optical fiber transmission line 1 may be employed. In the present embodiment, a case where such a configuration is adopted will be described.

<Optical fiber communication system>
FIG. 8A is a diagram illustrating a schematic configuration example of the optical fiber communication system according to the present embodiment. In the present embodiment, the transmitting-side terminal stations Tx1 to Tx4 are installed at different locations, respectively, and connected to an MDF (Main Distribution Frame, main distribution frame) 100 via an optical access line configured by a single-core optical fiber. ing. The connection between the single-core optical fiber connected to the terminal stations Tx1 to Tx4 and the multi-core optical fiber is performed via the MDF. The terminal stations Rx1 to Rx4 on the receiving side are installed at different locations, respectively, and are connected to the MDF 200 via an optical access line constituted by a single-core optical fiber. The connection between the single-core optical fiber connected to the terminal stations Rx1 to Rx4 and the multi-core optical fiber is performed via the MDF.

  In the system configuration shown in FIG. 8A, it is difficult to directly control the terminal stations Tx1 to Tx4 and Rx1 to 4 to realize the core identification function as in the first to fourth embodiments. Therefore, in the present embodiment, the core identification function and the connection switching function are mounted on the MDFs 100 and 200.

  FIG. 8B is a diagram illustrating a schematic configuration example of the MDF 100. The MDF 100 includes a single-core optical fiber termination unit 101, an optical switch 102, a single / multi conversion unit 103, a multi-core optical fiber termination unit 104, an optical transmission / reception unit 105, and a control unit 106. The MDF 200 on the receiving side has the same configuration as the MDF 100 on the transmitting side.

  The single core optical fiber terminating unit 101 accommodates a single core optical fiber constituting an optical access line, and connects the optical fiber and the optical switch 102. The optical switch 102 changes the connection between the single-core optical fiber termination unit 101 and the single / multi conversion unit 103, and connects or disconnects the optical transmission / reception unit 105 to / from the single / multi conversion unit 103. The single / multi converter 103 couples optical signals output from a plurality of single-core optical fibers to a multi-core optical fiber, or vice versa. The multi-core optical fiber terminating unit 104 accommodates a multi-core optical fiber constituting the optical fiber transmission line 1 and connects the optical fiber with the single / multi conversion unit 103. The optical transceiver 105 transmits and receives an optical signal used for core identification. The control unit 106 controls the optical switch 102 and the optical transmission / reception unit 105 to identify the cores of the multi-core optical fibers constituting the optical fiber transmission line 1, and based on the result of the core identification, the single-core optical fiber and the multi-core optical fiber And change the connection.

<Core identification method for multi-core optical fiber>
With reference to FIG. 9, an example of a method for identifying a core of a multi-core optical fiber using the MDFs 100 and 200 will be described. The core of the multi-core optical fiber constituting the optical fiber transmission line 1 is identified between the MDFs 100 and 200 installed at both ends of the optical fiber transmission line 1. Note that, in the MDF 100 of the present embodiment, the optical transmitting and receiving unit 105 functions as an example of an optical transmitting unit that transmits an optical signal for core identification. The optical switch 102 functions as an example of a first optical switch that switches the connection between the terminal stations Tx1 to Tx4 and the optical transceiver 105 for a plurality of cores. Further, in the MDF 200 of the present embodiment, the optical transmitting / receiving unit 205 functions as an example of an optical receiving unit that receives an optical signal for core identification. The optical switch 202 functions as an example of a second optical switch that switches the connection between the terminal stations Rx1 to Rx4 and the optical transmission / reception unit 205 to a plurality of cores.

  In the present embodiment, the control unit 106 controls transmission of the optical signal for core identification by the optical transmission / reception unit 105 and switching of the optical switch 102. On the other hand, the control unit 206 acquires the result of reception of the optical signal for core identification by the optical transmitting and receiving unit 205 via the optical switch 202. Further, control unit 206 performs core identification based on the obtained reception result.

  First, in the MDF 100 on the transmission side, the control unit 106 connects the optical transmission / reception unit 105 for core identification to one core in the multi-core optical fiber connected to the multi-core optical fiber termination unit 104 by switching the optical switch 102. I do. On the other hand, in the MDF 200 on the receiving side, the control unit 206 sequentially connects the optical transmitting and receiving unit 205 for core identification to each core of the multi-core optical fiber connected to the multi-core optical fiber termination unit 204 by switching the optical switch 202. . As a result, the control unit 206 of the MDF 200 identifies a receiving core corresponding to the transmitting core connected to the optical transmitting / receiving unit 105 on the transmitting side. By repeating such processing, the control unit 206 can determine the correspondence between the core specified on the transmission side (transmission core) and the core specified on the reception side (reception core). Further, the control unit 206 can set the optical switch 202 by the connection switching function described above.

  Note that the optical signal transmitted by the optical transmitting / receiving unit 105 may be CW light for detecting only optical power, or may be modulated light modulated by any signal. Further, when performing the above-mentioned core identification, when it is necessary to exchange information between the control unit 106 on the transmission side and the control unit 206 on the reception side, a separate line, a counter line, or OSC is used. You may. Alternatively, when a multi-core optical fiber in which a core (center core) is disposed on the center axis of the clad is used as in the third embodiment, the center core is used to transmit information between the control units 106 and 206. May be used for exchange. In this case, the transmission of the information from the control unit 206 to the control unit 106 is performed by transmitting the optical signal from the control unit 206 to the control unit 106 that is opposed to the optical fiber transmission line 1 (provided in parallel). Transmission path (not shown) may be used.

  As described above, when information can be exchanged between the control units 106 and 206, the control unit 106 may set the optical switch 102 by the connection switching function in the MDF 100, or the control units 106 and 206 May set the optical switches 102 and 202, respectively. Further, as described below, by defining a protocol for core identification in advance, the core identification can be completed only by transmitting a signal from the MDF 100 to the MDF 200 without requiring exchange between the MDFs 100 and 200. It is also possible.

<Protocol for core identification>
FIG. 10 is a diagram illustrating an example of a core identification protocol according to the present embodiment. As the first stage of this protocol, in the MDF 100 on the transmitting side, the control unit 106 causes the optical transmitting / receiving unit 105 to transmit a start notification signal (sequence) for notifying the MDF 200 on the receiving side of the start of core identification. The optical transmitting and receiving unit 105, for example, sequentially inputting a predetermined signal to all the cores is repeated a plurality of times. In the MDF 200 on the receiving side, the control unit 206 connects the specific core to the optical transmitting and receiving unit 205 in advance by switching the optical switch 202 so that the optical transmitting and receiving unit 205 can receive a signal from the specific core. To In this state, when the optical transmission / reception unit 205 receives a signal periodically, the control unit 206 recognizes the start of the core identification.

  Next, as the second stage, the control unit 106 on the transmission side continues the signal cutoff state in which no signal is input to any of the cores for a sufficiently long period of time equal to or longer than one cycle of the start notification signal. The control unit 206 on the receiving side recognizes that the core identification has proceeded to the next stage by determining that the start notification signal has not been received for one cycle or more. As a result, the control unit 206 starts switching the optical switch 202 so that the optical transmitting and receiving unit 205 is sequentially connected to all the cores of the multi-core optical fiber.

  Next, as a third stage, the transmission-side control unit 106 controls the optical switch 102 and the optical transmission / reception unit 105 to transmit / receive light to / from the first core (core 1) among the plurality of cores of the multi-core optical fiber. A signal is input from the unit 105. Thereafter, the control unit 106 shuts off the output of the signal from the optical transmission / reception unit 105 after a sufficient time has passed so that the reception state of the signals from all the cores can be checked, and the signal is cut off. Keep the state for a certain period of time.

  The control unit 206 on the receiving side sequentially checks the reception states of the signals from all the cores by the optical transmitting and receiving unit 205 while switching the optical switch 202. Accordingly, control unit 206 confirms reception of the signal input to core 1 on the transmission side, and thereby sets the reception-side core (reception core) corresponding to the transmission-side first core (transmission core). Identify. After that, the control unit 206 recognizes a signal interruption state that continues for a certain period of time as a trigger for starting identification of the next core, and starts switching the optical switch 202 again. By repeating such processing by the control units 106 and 206 on the transmission side, the control unit 206 can determine the correspondence between the transmission core and the reception core.

  In the present embodiment and a sixth embodiment to be described later, similarly to the fourth embodiment, the ITU-TG. The above-described core identification function can be realized by using SAPI / DAPI of the 709 standard.

[Embodiment 6]
In the fifth embodiment, only one section of the optical fiber transmission line (optical fiber transmission path 1) is provided. However, a plurality of sections of the optical fiber transmission path may be provided.

  FIG. 11 is a diagram showing a schematic configuration example of an optical fiber communication system provided with a plurality of sections of optical fiber transmission lines. As shown in FIG. 11, the optical fiber transmission line 1 is terminated by MDFs 100 and 300, and the optical fiber transmission line 2 is terminated by MDFs 200 and 300. The optical fiber transmission lines 1 and 2 are connected by wiring in the MDF 300. Out of the outputs of the optical fiber transmission line 1 (inputs to the MDF 300), those not connected to the input of the optical fiber transmission line 2 are connected from the MDF 300 to the optical access line. Note that the number of MDFs is not limited to the number shown in FIG.

  In the system as shown in FIG. 11, the cores of the multi-core optical fibers constituting the optical fiber transmission lines 1 and 2 are identified by the MDF for each section. Based on the identification information, the upper-level network monitoring device 400 manages the identification state of the core in each section. It should be noted that the network operator can manually perform the operation instead of the network monitoring device 400.

  Core identification for each section of the optical fiber transmission line is performed in the same manner as in the fifth embodiment. In the fifth and sixth embodiments, since the MDF performs the core identification of the multi-core optical fiber, unlike the first to fourth embodiments, the terminal station (terminal apparatus) does not need to be connected to the optical fiber transmission line. . Further, it is not necessary that all the cores of the optical fiber transmission line are operated commercially, and there may be a core that is not operated commercially.

1: optical fiber transmission line 10: transmission station, 11: control unit, 12: single / multi conversion unit, 13: optical switch 20: reception station, 21: control unit, 22: multi / single conversion unit, 23: optical switch Tx1, Tx2, Tx3, Tx4: Terminal stations Rx1, Rx2, Rx3, Rx4: Terminal stations 100, 200, 300: MDF
101, 201: single-core optical fiber termination units 102, 202: optical switches 103, 203: single / multi conversion units 104, 204: multi-core optical fiber termination units 105, 205: optical transmission / reception units 106, 206: control unit

Claims (11)

An optical fiber communication system including a transmitting device and a receiving device at an input end and an output end of an optical fiber transmission line, respectively,
The optical fiber transmission line is configured by a marker-less multi-core optical fiber, the multi-core optical fiber is a plurality of cores in which individual terminal devices are connected to each core at each of the input end and the output end, Having a plurality of cores arranged rotationally symmetrically with respect to the center axis of the clad in the cross section of the multi-core optical fiber,
The transmission device,
Control means for controlling transmission of an optical signal, such that an optical signal for core identification is input to at least one of the plurality of cores at the input end,
The receiving device,
Acquisition means for acquiring a reception result of the optical signal for core identification output from the multi-core optical fiber at the output end,
Based on the reception result, each of the plurality of cores used at the output end, identification means for performing core identification to identify which core used at the input end corresponds to,
The control means causes the input end to input the optical signal for core identification one by one to the plurality of cores sequentially.
Said identifying means, based on the output order of the optical signal for the core identifier that is output from each of said plurality of cores at the output end, an optical fiber communication system that comprises carrying out the core identifier. The control means controls the transmission of the optical signal for core identification according to a predetermined protocol that defines an input sequence and an input timing of the optical signal for core identification for the plurality of cores. The optical fiber communication system according to claim 1 . An optical fiber communication system including a transmitting device and a receiving device at an input end and an output end of an optical fiber transmission line, respectively,
The optical fiber transmission line is configured by a marker-less multi-core optical fiber, the multi-core optical fiber is a plurality of cores in which individual terminal devices are connected to each core at each of the input end and the output end, Having a plurality of cores arranged rotationally symmetrically with respect to the center axis of the clad in the cross section of the multi-core optical fiber,
The transmission device,
Control means for controlling transmission of an optical signal, so that an optical signal for core identification is input to at least one of the plurality of cores at the input end,
The receiving device,
Acquisition means for acquiring a reception result of the optical signal for core identification output from the multi-core optical fiber at the output end,
Based on the reception result, each of the plurality of cores used at the output end, identification means for performing core identification to identify which core used at the input end corresponds to,
The control means, at the input end, to the plurality of cores to input optical signals including different test patterns as the core identification optical signal,
Said identifying means, based on a detection result of the test patterns included in the optical signal for the core identifier that is output from each of said plurality of cores at the output end, you and performs the core identification light Fiber communication system. The multi-core optical fiber has a central core that is a core disposed on the central axis of the clad in the cross section,
The optical fiber communication according to any one of claims 1 to 3 , wherein the control unit transmits control information used for the core identification to the receiving device using the central core. system. An optical fiber communication system including a transmitting device and a receiving device at an input end and an output end of an optical fiber transmission line, respectively,
The optical fiber transmission line is configured by a marker-less multi-core optical fiber, the multi-core optical fiber is a plurality of cores in which individual terminal devices are connected to each core at each of the input end and the output end, Having a plurality of cores arranged rotationally symmetrically with respect to the center axis of the clad in the cross section of the multi-core optical fiber,
The transmission device,
A plurality of transmitting terminal apparatuses each connected to one of the plurality of cores at the input end;
Control means for controlling transmission of the optical signal for core identification by the plurality of transmitting terminal stations, such that an optical signal for core identification is input to at least one of the plurality of cores at the input end; ,
The receiving device,
A plurality of receiving terminal devices connected to one of the plurality of cores at the output end,
Acquisition means for acquiring the core identification optical signal output from the multi-core optical fiber at the output end, and acquiring the core identification optical signal reception result by the plurality of receiving terminal devices. ,
Based on the reception result, each of the plurality of cores used at the output end, identification means for performing core identification to identify which core used at the input end corresponds to,
The transmission device,
And row Cormorant optical switch switches connection of said plurality of transmission terminal apparatus for the plurality of cores,
Including the results of the core identification by the identifying means, based on feedback from the receiving device, and rows Cormorant setting means switch setting before Symbol optical switch,
Further an optical fiber communication system that further comprising a. An optical fiber communication system including a transmitting device and a receiving device at an input end and an output end of an optical fiber transmission line, respectively,
The optical fiber transmission line is configured by a marker-less multi-core optical fiber, the multi-core optical fiber is a plurality of cores in which individual terminal devices are connected to each core at each of the input end and the output end, Having a plurality of cores arranged rotationally symmetrically with respect to the center axis of the clad in the cross section of the multi-core optical fiber,
The transmission device,
A plurality of transmitting terminal apparatuses each connected to one of the plurality of cores at the input end;
Control means for controlling transmission of the optical signal for core identification by the plurality of transmitting terminal stations, such that an optical signal for core identification is input to at least one of the plurality of cores at the input end; ,
The receiving device,
A plurality of receiving terminal devices connected to one of the plurality of cores at the output end,
Acquisition means for acquiring the core identification optical signal output from the multi-core optical fiber at the output end, and acquiring the core identification optical signal reception result by the plurality of receiving terminal devices. ,
Based on the reception result, each of the plurality of cores used at the output end, identification means for performing core identification to identify which core used at the input end corresponds to,
The receiving device,
And row Cormorant optical switch switches connection of said plurality of receiving terminal device for said plurality of cores,
Based on the core of the identification result by the identifying means, a row Cormorant setting means switch setting before Symbol optical switch,
Further an optical fiber communication system that further comprising a. An optical fiber communication system including a transmitting device and a receiving device at an input end and an output end of an optical fiber transmission line, respectively,
The optical fiber transmission line is configured by a marker-less multi-core optical fiber, the multi-core optical fiber is a plurality of cores in which individual terminal devices are connected to each core at each of the input end and the output end, Having a plurality of cores arranged rotationally symmetrically with respect to the center axis of the clad in the cross section of the multi-core optical fiber,
The transmission device,
Control means for controlling transmission of an optical signal, so that an optical signal for core identification is input to at least one of the plurality of cores at the input end,
The receiving device,
Acquisition means for acquiring a reception result of the optical signal for core identification output from the multi-core optical fiber at the output end,
Based on the reception result, each of the plurality of cores used at the output end, identification means for performing core identification to identify which core used at the input end corresponds to,
The transmitting device and the receiving device are an MDF to which a plurality of transmitting terminal devices and a plurality of receiving terminal devices are respectively connected,
The transmission device,
An optical transmission unit for transmitting the optical signal for core identification,
A first optical switch that switches connection of the plurality of transmitting terminal devices and the optical transmitting unit to the plurality of cores,
The receiving device,
Optical receiving means for receiving the optical signal for core identification,
A second optical switch that switches connection of the plurality of reception terminal devices and the optical reception unit to the plurality of cores,
The control unit controls transmission of the optical signal for core identification by the optical transmission unit and switching of the first optical switch,
The acquisition unit, an optical fiber communication system that is characterized in that acquires the reception result of the light signal for the core identifier through the second optical switch according to the light receiving means. The transmission device further includes a first setting unit configured to perform switching setting of the first optical switch based on feedback from the reception device including a result of the core identification by the identification unit. Item 8. An optical fiber communication system according to Item 7 . The receiving device, on the basis of the result of the core identification by the identification means, the optical fiber according to claim 7 or 8, further comprising a second setting means for switching the setting of the second optical switch Communications system. The switching setting is for connecting the transmission terminal station apparatus and the reception terminal station apparatus of a predetermined combination through the plurality of cores, respectively, for the plurality of transmission terminal station apparatuses and the plurality of reception terminal station apparatuses. The optical fiber communication system according to any one of claims 5 , 6 , 8, and 9 , wherein: A core identification method in an optical fiber communication system including a transmission device and a reception device at an input end and an output end of an optical fiber transmission line, respectively,
The optical fiber transmission line is configured by a marker-less multi-core optical fiber, the multi-core optical fiber is a plurality of cores in which individual terminal devices are connected to each core at each of the input end and the output end, Having a plurality of cores arranged rotationally symmetrically with respect to the center axis of the clad in the cross section of the multi-core optical fiber,
A control step of controlling the transmission of the optical signal, so that the transmitting device receives an optical signal for core identification at least at one of the plurality of cores at the input end,
The receiving apparatus, the step of acquiring the reception result of the optical signal for core identification output from the multi-core optical fiber at the output end,
An identification step in which the receiving device performs a core identification to identify which of the plurality of cores used at the output end corresponds to which core used at the input end, based on the reception result; And having
In the control step, at the input end, the core identification optical signal is sequentially input to the plurality of cores one by one,
In the identification step, the core identification is performed based on an output order of the core identification optical signals output from each of the plurality of cores at the output end.
Core identification wherein a call.

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