Fiber sensing system, relay device, fiber sensing method, and program

Abstract

To acquire DAS data that represents vibration in a high frequency band underwater.SOLUTION: A fiber sensing system according to the present disclosure includes a submarine cable 60 and a plurality of relay devices 70 connected in series with each other via the submarine cable 60. The relay device 70 comprises: a DAS interrogator 71 which is connected to the relay device 70 in a rear stage via a sensing optical fiber 61 in the submarine cable 60; and a terminator 72 which is connected to the relay device 70 in the front stage via the sensing optical fiber 61. The DAS interrogator 71 outputs probe light to the sensing optical fiber 61. The terminator 72 terminates the probe light output from the DAS interrogator 71 in the relay device 70 in the front stage to the sensing optical fiber 61. The DAS interrogator 71 receives back scattered light of the probe light from the sensing optical fiber 61 and acquires the DAS data from the received back scattered light.SELECTED DRAWING: Figure 8

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a fiber sensing system, a relay device, a fiber sensing method, and a program. BACKGROUND ART

[0002] In recent years, fiber sensing systems using a DAS (Distributed Acoustic Sensing) interrogator that acquires environmental information representing the environment of an optical fiber have been researched and developed. Specifically, the DAS interrogator receives backscattered light in an optical fiber, and uses the received backscattered light to acquire DAS data representing vibration (including sound; the same applies hereinafter) applied to the optical fiber as the environmental information.

[0003] Furthermore, since the sensitivity of optical fibers has improved in recent years, research is progressing toward the practical application of fiber sensing systems using DAS interrogators as environmental monitoring systems for land use.

[0004] Research is also progressing on applying fiber sensing systems using DAS interrogators to underwater environments (for example, Patent Document 1). In this case, the DAS interrogator acquires DAS data using backscattered light in an optical fiber included in a submarine cable. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0005] Patent Document 1 International Publication No. 2021 / 153142 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0006] Here, when applying a fiber sensing system using a DAS interrogator to the ocean to monitor sounds from aquatic organisms and noise from maritime traffic, high-precision monitoring can be achieved by utilizing feature elements that exist in higher frequency bands.

[0007] However, due to the principles of fiber sensing, there was a limitation that if the length of the submarine cable over which the DAS interrogator acquires DAS data was increased, it would be impossible to acquire DAS data representing vibrations in the high-frequency band. Furthermore, there were limitations on where the DAS interrogator could be installed underwater. As a result, fiber sensing systems related to this technology had the problem of frequency limitations on the DAS data that could be acquired underwater.

[0008] Therefore, the purpose of this disclosure is to provide a fiber sensing system, a relay device, a fiber sensing method, and a program that can acquire DAS data representing high-frequency vibrations in the ocean, in view of the above-mentioned problems. [Means for solving the problem]

[0009] A fiber sensing system according to one embodiment is: Submarine cables and It includes a plurality of relay devices connected in series to each other via the aforementioned submarine cable, The aforementioned submarine cable includes a sensing optical fiber, Each of the aforementioned relay devices is A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via the aforementioned sensing optical fiber, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device. The terminator terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator receives backscattered light from the sensing optical fiber connected to the downstream relay device, and acquires DAS data from the received backscattered light that represents the vibrations applied to the sensing optical fiber connected to the downstream relay device.

[0010] A relay device in one embodiment is: One of several relay devices connected in series to each other via a submarine cable, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device. The terminator terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator receives backscattered light from the sensing optical fiber connected to the downstream relay device, and acquires DAS data from the received backscattered light that represents the vibrations applied to the sensing optical fiber connected to the downstream relay device.

[0011] One embodiment of a fiber sensing method is: A fiber sensing method performed by one of several relay devices connected in series to each other via a submarine cable, The relay device is, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The aforementioned fiber sensing method is The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device, The termination device terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator includes receiving backscattered light from the sensing optical fiber connected to the downstream relay device, and obtaining DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light.

[0012] A program according to one aspect is: A program for causing one of several relay devices connected in series to each other via a submarine cable to perform a fiber sensing method, The relay device is, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The aforementioned fiber sensing method is The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device, terminating, by the terminator, the probe light output from the DAS interrogator in the upstream repeater to the sensing optical fiber connected to the upstream repeater, such that the probe light is not reflected at an end of the sensing optical fiber; receiving, by the DAS interrogator, backscattered light of the probe light from the sensing optical fiber connected to the downstream repeater, and acquiring, from the received backscattered light, DAS data representing vibration applied to the sensing optical fiber connected to the downstream repeater.

Effects of the Invention

[0013] According to the above aspect, an effect is obtained that a fiber sensing system, a repeater, a fiber sensing method, and a program capable of acquiring DAS data representing high-frequency band vibration in the sea can be provided.

Brief Description of Drawings

[0014] [Figure 1] It is a diagram showing a configuration example of the fiber sensing system according to Embodiment 1. [Figure 2] It is a diagram showing a configuration example of a submarine cable and an optical amplification repeater according to Embodiment 1. [Figure 3] It is a diagram showing a configuration example of components used for communication related to fiber sensing in the fiber sensing system according to Embodiment 1. [Figure 4] It is a diagram showing an example of signal processing and information processing executed by an information processing apparatus in a ground station according to Embodiment 1. [Figure 5] It is a diagram showing an example of a setting screen for setting an acquisition section of DAS data, which is displayed on the information processing apparatus in the ground station according to Embodiment 1. [Figure 6] It is a flowchart showing an example of a schematic operation flow of the optical amplification repeater according to Embodiment 1. [Figure 7] It is a diagram showing a configuration example of a fiber sensing system according to Embodiment 2. [Figure 8] This figure shows an example configuration of a fiber sensing system according to Embodiment 3. [Figure 9] This is a block diagram showing an example of the hardware configuration of an optical amplification relay device and a computer that implements the relay device according to Embodiments 1 to 3. [Modes for carrying out the invention]

[0015] Embodiments of the present disclosure will be described below with reference to the drawings. Note that the following description and drawings have been omitted and simplified as appropriate for clarity of explanation. Furthermore, in the following drawings, the same elements are denoted by the same reference numerals, and redundant explanations have been omitted where necessary.

[0016] <Embodiment 1> Figure 1 shows an example of the configuration of a fiber sensing system according to this first embodiment. The fiber sensing system according to this embodiment 1 includes a submarine cable 10, a plurality of optical amplification relay devices 20-1 to 20-N (where N is a natural number of 2 or more), and ground stations 30-1 and 30-2. In the following, when the specific optical amplification relay device 20-1 to 20-N is not identified, it will simply be referred to as "optical amplification relay device 20." Similarly, ground stations 30-1 and 30-2 will simply be referred to as "ground station 30." In the following drawings, optical amplification relay devices 20-1 to 20-N will be appropriately referred to as optical amplification relay device #1 to #N, respectively.

[0017] The submarine cable 10 and the optical amplification relay devices 20-1 to 20-N are installed in the sea, more specifically on the seabed. The optical amplification relay devices 20-1 to 20-N are connected in series to each other via the submarine cable 10. Furthermore, the optical amplification relay devices 20-1 to 20-N are installed at regular intervals along the submarine cable 10. A ground station 30-1 is connected to one end of the submarine cable 10, and a ground station 30-2 is connected to the other end of the submarine cable 10.

[0018] As described later, the submarine cable 10 is a multi-core cable that includes communication optical fibers, sensing optical fibers, and power lines. As will be described later, the optical amplification relay devices 20-1 to 20-N are equipped with optical amplifiers, which were also installed in optical amplification relay devices related to the same technology, as well as components for fiber sensing and components for communication related to fiber sensing.

[0019] Figure 2 shows an example configuration of the submarine cable 10 and optical amplification relay devices 20-1 to 20-N according to this embodiment 1.

[0020] First, let's explain an example of the configuration of the submarine cable 10. As described above, the submarine cable 10 is a multi-core cable. The submarine cable 10 includes a communication optical fiber 11 used for communication between ground stations 30-1 and 30-2, a power line 12 for power supply, a communication optical fiber 13 used for fiber sensing communication between ground stations 30-1 and 30-2 and optical amplification relay devices 20-1 to 20-N, and a sensing optical fiber 14 used for fiber sensing.

[0021] The sensing optical fiber 14 can be the same type of optical fiber used for optical communication as the communication optical fibers 11 and 13. In addition, the sensing optical fiber 14 can also be a fiber specifically designed for fiber sensing, to which impurities have been added to enhance sensitivity.

[0022] Next, we will describe the configuration examples of optical amplification relay devices 20-1 to 20-N. The configuration of optical amplification relay device 20-2 will be described below, but the other optical amplification relay devices 20-1, 20-3 to 20-N have a similar configuration to optical amplification relay device 20-2.

[0023] The optical amplification relay device 20-2 includes an optical amplifier 21, a power supply 22, a network switch 23, a DAS control / data processing device 24, a terminator 25, and a DAS interrogator 26.

[0024] The optical amplifier 21 is connected to the communication optical fiber 11 in the submarine cable 10. The optical amplifier 21 amplifies the signal transmitted through the communication optical fiber 11.

[0025] The power supply unit 22 is connected to the power line 12 inside the submarine cable 10. The power supply unit 22 supplies power, which is supplied via the power line 12, to each component inside the optical amplification relay device 20-2.

[0026] The network switch 23 is connected to the communication optical fiber 13 inside the submarine cable 10. The network switch 23 transmits the DAS data (described later) acquired by the DAS interrogator 26 to the ground station 30-1 or 30-2 via the communication optical fiber 13. The network switch 23 also receives control information for controlling the DAS control / data processing device 24 from the ground station 30-1 or 30-2 via the communication optical fiber 13, and outputs the received control information to the DAS control / data processing device 24. If there are many optical amplification relay devices 20 installed in the fiber sensing system, the network switch 23 can increase the amount of DAS data and other communications by performing optical wavelength division multiplexing communication.

[0027] The DAS control / data processing unit 24 is connected to the network switch 23 and the DAS interrogator 26. The DAS control / data processing unit 24 controls the DAS interrogator 26 based on control information from the ground station 30-1 or 30-2. Specifically, if the control information indicates that the submarine cable 10 between optical amplification relay devices 20-2 and 20-3 is a section for acquiring DAS data, the DAS control / data processing unit 24 controls the DAS interrogator 26 to acquire DAS data. At this time, the DAS control / data processing unit 24 controls the operating state of the DAS interrogator 26 and generates a reference clock necessary for the operation of the DAS interrogator 26. The DAS control / data processing unit 24 also temporarily stores the DAS data acquired by the DAS interrogator 26 and then outputs it to the network switch 23. The DAS control / data processing unit 24 can also compress and encrypt the DAS data before outputting it to the network switch 23, if necessary.

[0028] The termination unit 25 is connected to the sensing optical fiber 14 in the submarine cable 10. Specifically, the termination unit 25 is connected to the DAS interrogator 26 in the preceding optical amplification relay device 20-1 via the sensing optical fiber 14. Here, if the submarine cable 10 between optical amplification relay devices 20-1 and 20-2 is the section for acquiring DAS data, probe light is output from the DAS interrogator 26 in the preceding optical amplification relay device 20-1 to the sensing optical fiber 14. In this case, the termination unit 25 terminates the probe light output to the sensing optical fiber 14 so that it is not reflected at the fiber end of the sensing optical fiber 14.

[0029] The DAS interrogator 26 is connected to the sensing optical fiber 14 in the submarine cable 10. Specifically, the DAS interrogator 26 is connected to the terminator 25 in the downstream optical amplification relay device 20-3 via the sensing optical fiber 14. Here, if the submarine cable 10 between optical amplification relay devices 20-2 and 20-3 is the section for acquiring DAS data, the DAS interrogator 26 outputs probe light to the sensing optical fiber 14, receives the backscattered light of the probe light from the sensing optical fiber 14, and acquires DAS data representing the vibrations applied to the sensing optical fiber 14 from the received backscattered light. The DAS interrogator 26 also outputs the DAS data acquired from the backscattered light to the DAS control / data processing device 24.

[0030] In the optical amplification relay device 20-1, the terminator 25 is connected to the ground station 30-1 via the sensing optical fiber 14 in the submarine cable 10. Furthermore, in the optical amplification relay device 20-N, the DAS interrogator 26 is connected to the ground station 30-2 via the sensing optical fiber 14 in the submarine cable 10.

[0031] Figure 3 is a diagram showing an example of the configuration of components used for communication related to fiber sensing in the fiber sensing system according to this embodiment 1. Optical amplification relay devices 20-1 to 20-N include a network switch 23 and a DAS control / data processing device 24 as components used for communication related to fiber sensing. Note that in Figure 3, other components of optical amplification relay devices 20-1 to 20-N shown in Figure 2 have been omitted.

[0032] The configuration of ground station 30-1 will be described below, but ground station 30-2 has the same configuration as ground station 30-1. The ground station 30-1 includes an information processing device 31, an NTP (Network Time Protocol) server 32, a DAS control / data processing device 33, and a network switch 34.

[0033] The information processing device 31 generates control information for controlling the DAS control / data processing device 33 in the ground station 30-1 and the DAS control / data processing devices 24 in the optical amplification relay devices 20-1 to 20-N. This control information is transmitted via the network switch 34 to the DAS control / data processing device 33 in the ground station 30-1 and the DAS control / data processing devices 24 in the optical amplification relay devices 20-1 to 20-N. The information processing device 31 also receives DAS data temporarily stored in the DAS control / data processing devices 24 in the optical amplification relay devices 20-1 to 20-N via the network switch 34 and performs signal processing and information processing on the received DAS data.

[0034] The NTP server 32 is a time server for aligning the time of the DAS control / data processing device 33 in the ground station 30-1 and the DAS control / data processing devices 24 in the optical amplification relay devices 20-1 to 20-N.

[0035] The network switch 34 is connected to the communication optical fiber 13 in the submarine cable 10. Specifically, the network switch 34 is connected to each of the network switches 23 in the optical amplification relay devices 20-1 to 20-N via the communication optical fiber 13.

[0036] Figure 4 shows an example of signal processing and information processing performed in the information processing device 31 within the ground station 30-1 or 30-2 according to this embodiment 1. In Figure 4, the DAS data 40-1 to 40-(N-1) are DAS data temporarily stored in the DAS control / data processing devices 24 within the optical amplification relay devices 20-1 to 20-(N-1). These DAS data 40-1 to 40-(N-1) are acquired by the information processing device 31 via the network switch 34.

[0037] The information processing device 31 performs acoustic signal generation processing 41, acoustic signal processing 42, and detection processing 43 on the DAS data 40-1. The acoustic signal generation process 41 is a process that generates an acoustic signal from the DAS data 40-1. The acoustic signal processing 42 and detection processing 43 are processes that detect a target by performing frequency analysis and pattern patching on the acoustic signal generated by the acoustic signal generation processing 41. Furthermore, the information processing device 31 also performs acoustic signal generation processing 41, acoustic signal processing 42, and detection processing 43 on DAS data 40-2 to 40-(N-1) in the same manner.

[0038] Subsequently, the information processing device 31 performs integrated information processing 44, which combines the detection processing results obtained from the detection processing 43 for each of the DAS data 40-1 to 40-(N-1). Then, the information processing device 31 outputs information regarding the characteristics of the signals detected by the entire fiber sensing system and the location of the detected targets.

[0039] Figure 5 shows an example of a setting screen for setting the DAS data acquisition interval, which is displayed on the information processing device 31 in the ground station 30-1 or 30-2 according to this embodiment 1. In this embodiment 1, it is possible to select whether or not to acquire DAS data for each submarine cable 10 separated by the DAS interrogator 26 and the terminator 25. In the example shown in Figure 5, the submarine cable 10 between optical amplification relay devices 20-1 and 20-2, and the submarine cable 10 between optical amplification relay devices 20-2 and 20-3 are set as sections for acquiring DAS data.

[0040] Figure 6 is a flowchart illustrating an example of the general operation flow of the optical amplification relay device 20 according to this embodiment 1. Figure 6 shows an example of the operation of optical amplification relay device 20-2, one of the optical amplification relay devices 20-1 to 20-N that are operating based on control information transmitted by the ground station 30-1. In Figure 6, it is assumed that the control information transmitted by the ground station 30-1 notifies that the submarine cable 10 between optical amplification relay devices 20-1 and 20-2, and the submarine cable 10 between optical amplification relay devices 20-2 and 20-3 are set as DAS data acquisition sections, and that DAS data should be transmitted to the ground station 30-1.

[0041] Here, the submarine cable 10 between optical amplification relay devices 20-2 and 20-3 is the section for acquiring DAS data. Therefore, the DAS control / data processing device 24 controls the DAS interrogator 26 to acquire DAS data using the sensing optical fiber 14 in the submarine cable 10 between the optical amplification relay devices 20-2 and 20-3.

[0042] Specifically, the DAS interrogator 26 outputs probe light to the sensing optical fiber 14 under the control of the DAS control / data processing device 24 (step S11), receives backscattered light from the sensing optical fiber 14 (step S12), and obtains DAS data representing the vibration applied to the sensing optical fiber 14 from the received backscattered light (step S13).

[0043] The DAS control and data processing device 24 temporarily stores the DAS data acquired by the DAS interrogator 26, and then transmits it to the ground station 30-1 via the communication optical fiber 13 from the network switch 23 (step S14).

[0044] On the other hand, the submarine cable 10 between optical amplification relay devices 20-1 and 20-2 is also part of the DAS data acquisition section. Therefore, probe light is output from the DAS interrogator 26 in the preceding optical amplification relay device 20-1 to the sensing optical fiber 14 in the submarine cable 10 between optical amplification relay devices 20-1 and 20-2.

[0045] Therefore, the termination unit 25 terminates the probe light output from the DAS interrogator 26 in the preceding optical amplification relay device 20-1 to the sensing optical fiber 14 so that it is not reflected at the fiber end of the sensing optical fiber 14 (step S15).

[0046] As described above, according to this embodiment 1, each of the multiple optical amplification relay devices 20 includes a terminator 25 and a DAS interrogator 26. The DAS interrogator 26 is connected to the terminator 25 in the downstream optical amplification relay device 20 via a sensing optical fiber 14, and the terminator 25 is connected to the DAS interrogator 26 in the upstream optical amplification relay device 20 via the sensing optical fiber 14. The DAS interrogator 26 outputs probe light to the sensing optical fiber 14. The probe light is terminated by the terminator 25 in the downstream optical amplification relay device 20, and the backscattered light of the probe light is received by the DAS interrogator 26. From the received backscattered light, the DAS interrogator 26 acquires DAS data indicating the vibrations applied to the sensing optical fiber 14.

[0047] In other words, according to this embodiment 1, the sensing optical fiber 14 is divided between the DAS interrogator 26 and the terminator 25, and then the DAS interrogator 26 performs fiber sensing. As a result, even when the cable length of the entire submarine cable 10 of the fiber sensing system is long, DAS data representing vibrations in a high frequency band corresponding to the installation interval of the optical amplification relay device 20 can be acquired.

[0048] Furthermore, according to this embodiment 1, each of the multiple optical amplification relay devices 20 includes a network switch 23 that transmits DAS data to the ground station 30 via the communication optical fiber 13. This allows the DAS data acquired by the DAS interrogator 26 in the optical amplification relay device 20 to be transmitted to the ground station 30. In addition, the DAS data acquired by the DAS interrogator 26 in the multiple optical amplification relay devices 20 can be aggregated at the ground station 30.

[0049] Furthermore, according to this embodiment 1, each of the multiple optical amplification relay devices 20 includes a DAS control / data processing device 24 that controls the DAS interrogator 26 and temporarily stores the DAS data acquired by the DAS interrogator 26. This eliminates the need to synchronize the ground station 30 with the DAS interrogator 26, making it possible to construct a highly redundant fiber sensing system.

[0050] Furthermore, according to this embodiment 1, the DAS control / data processing device 24 compresses the DAS data as needed, and the network switch 23 transmits the compressed DAS data via the communication optical fiber 13. As a result, even if the number of DAS interrogators 26 in the fiber sensing system increases, the DAS data can be transmitted without increasing the number of cores in the communication optical fiber 13.

[0051] Furthermore, according to this embodiment 1, the sensing optical fiber 14 is provided separately from the communication optical fiber 11. Therefore, as the sensing optical fiber 14, a fiber specifically for fiber sensing can be used, which has impurities added to enhance its sensitivity.

[0052] Furthermore, according to this embodiment 1, the sensing optical fiber 14 can also be an optical fiber used for optical communication, similar to the communication optical fibers 11 and 13. In this case, a fiber sensing system can be constructed by utilizing existing submarine cables for optical communication.

[0053] Furthermore, according to this embodiment 1, the ground station 30 includes an information processing device 31 that performs signal processing and information processing on DAS data acquired by the DAS interrogators 26 in the multiple optical amplification relay devices 20. In this way, high-load processing is consolidated at the ground station 30. This makes it possible to reduce the size of the optical amplification relay devices 20, which are installed underwater and have poor maintainability.

[0054] Furthermore, according to this embodiment 1, the information processing device 31 can select whether or not to acquire DAS data for each section of the submarine cable 10 separated by the DAS interrogator 26 and the terminator 25. This allows, for example, if the total length of the submarine cable 10 is long and the amount of DAS data would strain communication via the communication optical fiber 13, the acquisition of DAS data for any section can be stopped. As a result, data loss due to network congestion can be prevented.

[0055] <Embodiment 2> This second embodiment is an example of using a fiber sensing system for underwater acoustic communication. Figure 7 shows an example configuration of the fiber sensing system according to Embodiment 2. The configuration of the fiber sensing system according to Embodiment 2 is the same as that of the fiber sensing system according to Embodiment 1 described above.

[0056] The underwater drone 51 is equipped with an underwater communication device 52, and transmits data from within the underwater drone 51 using the underwater communication device 52. The underwater communication device 52 is a device that performs underwater acoustic communication using an acoustic signal as a carrier wave. Underwater acoustic communication is characterized by the fact that the communication distance changes greatly depending on the temperature gradient in the sea.

[0057] The DAS interrogator 26 in the optical amplification relay device 20 acquires DAS data representing vibrations applied to the sensing optical fiber 14 due to the acoustic signal transmitted as a carrier wave from the underwater drone 51. The information processing device 31 in the ground station 30 detects the acoustic signal transmitted from the underwater drone 51 by performing signal processing and information processing on the DAS data.

[0058] As described above, according to this embodiment 2, if an acoustic signal is transmitted from the underwater drone 51 in the vicinity of the submarine cable 10, that acoustic signal can be detected. Therefore, although underwater acoustic communication has the characteristic that the communication distance changes greatly depending on the temperature gradient in the sea, if the underwater drone 51 is located in the vicinity of the submarine cable 10, underwater acoustic communication can be performed between the underwater drone 51 and the underwater drone 51. Other effects are the same as those of Embodiment 1 described above.

[0059] <Embodiment 3> This third embodiment corresponds to an embodiment that expands upon the above-described embodiments 1 and 2. Figure 8 shows an example of the configuration of a fiber sensing system according to this third embodiment. The fiber sensing system according to this third embodiment includes a submarine cable 60 and a plurality of relay devices 70-1 to 70-N (where N is a natural number of 2 or more). In the following, when it is not necessary to specify which relay device 70-1 to 70-N is being referred to, it will simply be referred to as "relay device 70".

[0060] The submarine cable 60 and relay devices 70-1 to 70-N are installed in the sea, more specifically on the seabed. The relay devices 70-1 to 70-N are connected in series to each other via the submarine cable 60. Furthermore, the relay devices 70-1 to 70-N are installed at regular intervals along the submarine cable 10.

[0061] The submarine cable 60 includes a sensing optical fiber 61. The configuration of relay device 70-2 will be described below, but the other relay devices 70-1, 70-3 to 70-N have a similar configuration to relay device 70-2.

[0062] The relay device 70-2 includes a DAS interrogator 71 and a termination device 72. The DAS interrogator 71 is connected to a sensing optical fiber 61 within the submarine cable 60. Specifically, the DAS interrogator 71 is connected via the sensing optical fiber 61 to a downstream relay device 70-3 (more specifically, to a terminator 72 within the relay device 70-3).

[0063] The termination device 72 is connected to the sensing optical fiber 61 in the submarine cable 60. Specifically, the termination device 72 is connected to the preceding relay device 70-1 (more specifically, the DAS interrogator 71 in the relay device 70-1) via the sensing optical fiber 61.

[0064] Here, the DAS interrogator 71 outputs probe light to the sensing optical fiber 61 connected to the subsequent relay device 70-3. The termination device 72 terminates the probe light output from the DAS interrogator 71 in the preceding relay device 70-1 to the sensing optical fiber 61 connected to the preceding relay device 70-1, so as not to be reflected at the end of the sensing optical fiber 61.

[0065] The DAS interrogator 71 receives backscattered light from the sensing optical fiber 61 connected to the downstream relay device 70-3, and acquires DAS data representing the vibrations applied to the sensing optical fiber 61 connected to the downstream relay device 70-3 from the received backscattered light.

[0066] In other words, according to this embodiment 3, the sensing optical fiber 61 is divided between the DAS interrogator 71 and the termination unit 72, and then the DAS interrogator 71 performs fiber sensing. As a result, even when the cable length of the entire submarine cable 60 of the fiber sensing system is long, DAS data representing vibrations in a high frequency band corresponding to the installation interval of the relay devices 70-1 to 70-N can be acquired.

[0067] The submarine cable 60 may further include a communication optical fiber. The relay device 70 may further include a network switch connected to the communication optical fiber and transmitting DAS data to a predetermined destination via the communication optical fiber. The predetermined destination may be, for example, the ground station 30 according to the embodiments 1 and 2 described above.

[0068] The relay device 70 may also further include a control unit that controls the DAS interrogator 71 to acquire DAS data and temporarily stores the DAS data acquired by the DAS interrogator 71. In this case, the network switch may transmit the temporarily stored DAS data to a predetermined destination.

[0069] Furthermore, the sensing optical fiber 61 may be an optical fiber to which impurities have been added to enhance its sensitivity. Furthermore, the DAS data may also represent vibrations applied to the sensing optical fiber 61 due to an acoustic signal transmitted as a carrier wave from an underwater communication device mounted on an underwater unmanned vehicle.

[0070] <Hardware configuration of the position evaluation device according to the embodiment> Figure 9 is a block diagram showing an example of the hardware configuration of a computer 90 that implements the optical amplification relay device 20 and relay device 70 according to the embodiments 1 to 3 described above.

[0071] The computer 90 includes a processor 91, memory 92, storage 93, input / output interface (I / F) 94, and communication interface (Communication I / F) 95. The processor 91, memory 92, storage 93, input / output interface 94, and communication interface 95 are connected to each other by a data transmission path for sending and receiving data.

[0072] The processor 91 is a processing unit such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The memory 92 is a type of memory such as RAM (Random Access Memory) or ROM (Read Only Memory). The storage 93 is a storage device such as an HDD (Hard Disk Drive), SSD (Solid State Drive), or memory card. The storage 93 may also be a type of memory such as RAM or ROM.

[0073] A program is stored in the storage 93. This program includes a set of instructions (or software code) that, when loaded into a computer, causes the computer 90 to perform one or more functions of the optical amplification relay device 20 and relay device 70 described above. The components of the optical amplification relay device 20 and relay device 70 described above may also be realized by the processor 91 loading and executing the program stored in the storage 93. Furthermore, the storage function of the optical amplification relay device 20 and relay device 70 described above may be realized by memory 92 or storage 93.

[0074] Furthermore, the programs described above may be stored on non-temporary computer-readable media or tangible storage media. Examples, but not limited to, include RAM, ROM, flash memory, SSD or other memory technologies, CD (Compact Disc)-ROM, DVD (Digital Versatile Disc), Blu-ray® disc or other optical disc storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices. The programs may also be transmitted over temporary computer-readable media or communication media. Examples, but not limited to, include electrical, optical, acoustic or other forms of propagating signals.

[0075] The input / output interface 94 is connected to a display device 941, an input device 942, a sound output device 943, and the like. The display device 941 is a device that displays a screen corresponding to the drawing data processed by the processor 91, such as an LCD (Liquid Crystal Display), a CRT (Cathode Ray Tube) display, or a monitor. The input device 942 is a device that receives operator input, such as a keyboard, mouse, and touch sensor. The display device 941 and the input device 942 may be integrated and implemented as a touch panel. The sound output device 943 is a device that outputs sound corresponding to the acoustic data processed by the processor 91, such as a speaker.

[0076] The communication interface 95 transmits and receives data to and from external devices. For example, the communication interface 95 communicates with external devices via a wired communication path or a wireless communication path.

[0077] In the above description, examples were given in which the optical amplification relay device 20 and relay device 70 according to Embodiments 1 to 3 described above are implemented by the computer 90 shown in Figure 9. However, the explanation is not limited to this, and the ground station 30 according to Embodiments 1 and 2 described above may also be implemented by the computer 90 shown in Figure 9.

[0078] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure are possible, as can be understood by those skilled in the art within the scope of the present disclosure. For example, some or all of the embodiments described above may be used in combination with each other.

[0079] Furthermore, some or all of the embodiments described above may also be described as follows, but are not limited to these. (Note 1) Submarine cables and It includes a plurality of relay devices connected in series to each other via the aforementioned submarine cable, The aforementioned submarine cable includes a sensing optical fiber, Each of the aforementioned relay devices is A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via the aforementioned sensing optical fiber, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device. The terminator terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator receives backscattered light from the sensing optical fiber connected to the downstream relay device, and acquires DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light. Fiber sensing system. (Note 2) The aforementioned submarine cable further includes a communication optical fiber, Each of the plurality of relay devices further includes a network switch connected to the communication optical fiber and transmitting the DAS data to a predetermined destination via the communication optical fiber. The fiber sensing system described in Appendix 1. (Note 3) Each of the plurality of relay devices further includes a control unit that controls the DAS interrogator to acquire the DAS data and temporarily stores the DAS data acquired by the DAS interrogator, The network switch transmits the temporarily stored DAS data to the predetermined destination. The fiber sensing system described in Appendix 2. (Note 4) The aforementioned sensing optical fiber is an optical fiber whose sensitivity has been enhanced by adding impurities. The fiber sensing system described in Appendix 1. (Note 5) The DAS data represents vibrations applied to the sensing optical fiber due to an acoustic signal transmitted as a carrier wave from an underwater communication device mounted on an underwater unmanned vehicle. The fiber sensing system described in Appendix 1. (Note 6) One of several relay devices connected in series to each other via a submarine cable, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device. The terminator terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator receives backscattered light from the sensing optical fiber connected to the downstream relay device, and acquires DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light. Relay device. (Note 7) The network switch is connected to a communication optical fiber included in the submarine cable and transmits the DAS data to a predetermined destination via the communication optical fiber. The relay device described in Appendix 6. (Note 8) The system further includes a control unit that controls the DAS interrogator to acquire the DAS data and temporarily stores the DAS data acquired by the DAS interrogator, The network switch transmits the temporarily stored DAS data to the predetermined destination. The relay device described in Appendix 7. (Note 9) The DAS data represents vibrations applied to the sensing optical fiber due to an acoustic signal transmitted as a carrier wave from an underwater communication device mounted on an underwater unmanned vehicle. The relay device described in Appendix 6. (Note 10) A fiber sensing method performed by one of several relay devices connected in series to each other via a submarine cable, The relay device is, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The aforementioned fiber sensing method is The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device, The termination device terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator includes receiving backscattered light from the sensing optical fiber connected to the downstream relay device, and obtaining DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light. Fiber sensing method. (Note 11) A program for causing one of several relay devices connected in series to each other via a submarine cable to perform a fiber sensing method, The relay device is, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The aforementioned fiber sensing method is The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device, The termination device terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator includes receiving backscattered light from the sensing optical fiber connected to the downstream relay device, and obtaining DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light. program. [Explanation of Symbols]

[0080] 10 Submarine Cables 11. Optical fibers for communications 12 Power lines 13. Optical fibers for communications 14. Optical fibers for sensing 20-1~20-N Optical Amplification and Relay Device 21 Optical Amplifier 22 Power supply 23 Network Switches 24 DAS Control and Data Processing Equipment 25 Terminator 26 DAS Interrogator 30-1, 30-2 Ground station 31 Information Processing Device 32 NTP servers 33 DAS Control and Data Processing Equipment 34 Network Switches 40-1 to 40-(N-1) DAS data 41. Acoustic signal generation process 42. Acoustic signal processing 43 Detection process 44. Integrated Information Processing 51 Underwater drone 52 Underwater communication devices 60 Submarine Cables 61 Optical fiber for sensing 70-1~70-N Relay Device 71 DAS Interrogator 72 Terminator 90 Computer 91 processors 92 memory 93 Storage 94 Input / Output Interfaces 941 Display device 942 Input device 943 Sound output device 95 Communication Interface

Claims

1. Submarine cables and It includes a plurality of relay devices connected in series to each other via the aforementioned submarine cable, The aforementioned submarine cable includes a sensing optical fiber, Each of the aforementioned relay devices is A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via the aforementioned sensing optical fiber, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device. The terminator terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator receives backscattered light from the sensing optical fiber connected to the downstream relay device, and acquires DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light. Fiber sensing system.

2. The aforementioned submarine cable further includes a communication optical fiber, Each of the plurality of relay devices further includes a network switch connected to the communication optical fiber and transmitting the DAS data to a predetermined destination via the communication optical fiber. The fiber sensing system according to claim 1.

3. Each of the plurality of relay devices further includes a control unit that controls the DAS interrogator to acquire the DAS data and temporarily stores the DAS data acquired by the DAS interrogator, The network switch transmits the temporarily stored DAS data to the predetermined destination. The fiber sensing system according to claim 2.

4. The DAS data represents vibrations applied to the sensing optical fiber due to an acoustic signal transmitted as a carrier wave from an underwater communication device mounted on an underwater unmanned vehicle. The fiber sensing system according to claim 1.

5. One of several relay devices connected in series to each other via a submarine cable, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device. The terminator terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator receives backscattered light from the sensing optical fiber connected to the downstream relay device, and acquires DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light. A relay device.

6. The network switch is connected to a communication optical fiber included in the submarine cable and transmits the DAS data to a predetermined destination via the communication optical fiber. The relay device according to claim 5.

7. The system further includes a control unit that controls the DAS interrogator to acquire the DAS data and temporarily stores the DAS data acquired by the DAS interrogator, The network switch transmits the temporarily stored DAS data to the predetermined destination. The relay device according to claim 6.

8. The DAS data represents vibrations applied to the sensing optical fiber due to an acoustic signal transmitted as a carrier wave from an underwater communication device mounted on an underwater unmanned vehicle. The relay device according to claim 5.

9. A fiber sensing method performed by one of several relay devices connected in series to each other via a submarine cable, The relay device is, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The aforementioned fiber sensing method is The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device, The termination device terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator includes receiving backscattered light from the sensing optical fiber connected to the downstream relay device, and obtaining DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light. Fiber sensing method.

10. A program for causing one of several relay devices connected in series to each other via a submarine cable to perform a fiber sensing method, The relay device is, A DAS (Distributed acoustic sensing) interrogator connected to a downstream relay device via a sensing optical fiber included in the aforementioned submarine cable, Includes a terminator connected to a preceding relay device via the sensing optical fiber, The aforementioned fiber sensing method is The DAS interrogator outputs probe light to the sensing optical fiber connected to the downstream relay device, The termination device terminates the probe light output from the DAS interrogator in the preceding relay device to the sensing optical fiber connected to the preceding relay device, so as not to be reflected at the end of the sensing optical fiber. The DAS interrogator includes receiving backscattered light from the sensing optical fiber connected to the downstream relay device, and obtaining DAS data representing vibrations applied to the sensing optical fiber connected to the downstream relay device from the received backscattered light. program.

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