Optical fiber vibration sensing device and optical fiber vibration sensing method

Abstract

To provide an optical fiber vibration sensing device capable of identifying a position where vibration is applied with a simple configuration.SOLUTION: An optical fiber vibration sensing device of the present disclosure includes: an optical transmission medium having a plurality of optical transmission paths; a forward Mach-Zehnder interferometer for branching and inputting light from one end of the optical transmission medium into two optical transmission paths, and combining and receiving the light from the two optical transmission paths at the other end of the optical transmission medium; and a backward Mach-Zehnder interferometer for branching and inputting light from the other end of the optical transmission medium into two other optical transmission paths, and combining and receiving the light from the two other optical transmission paths at the one end of the optical transmission medium.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to optical fiber vibration sensing technology using an optical fiber interferometer. [Background technology]

[0002] As a type of optical fiber vibration sensing technology using optical fiber interferometers, a method has been proposed and commercialized in which multiple optical fiber ring interferometers are configured and vibrations are detected on an optical fiber ring interferometer system basis to detect abnormalities such as intrusions (for example, see Non-Patent Document 1).

[0003] As a method for identifying the vibration generation position using an optical fiber interferometer, a method has been proposed in which a sub-loop is added to an optical fiber ring interferometer. By passing through the sub-loop multiple times, multiple optical paths are apparently formed within the same optical fiber ring, and the position can be identified by comparing the interference light output of the light that has passed through each path (for example, see Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Fujikura Engineering Ltd., "Optical Fiber Intrusion Detection System", https: / / www.fen.fujikura.jp / products / pro01 / tel-co-pdf02.pdf (Accessed 2021.1.7) [Non-Patent Document 2] Tatsuya Omori, Hiroaki Ogihara, Kenya Hashimoto, Masatsune Yamaguchi, "Vibration Position Identification Method for Optical Fiber Ring Interferometer Vibration Sensor", IEICE Transactions on Information and Communication Engineers, Vol. J89-B, No. 4, pp. 594-601, 2006 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the device put to practical use in Non-Patent Document 1 requires the installation of a folding device called a branch coupler for each detection section. In order to detect vibrations in a distributed manner, it is necessary to install the required number of branch couplers, which poses a major challenge in terms of installation.

[0006] In addition, in Non-Patent Document 2, it is possible to identify the vibration position. However, since it is premised on applying vibration to one point of the optical fiber ring interferometer, if the entire optical fiber ring interferometer is mounted in a single optical fiber cable that is not in a ring form, vibration will occur in two points, which makes it difficult to apply.

[0007] The present disclosure has been made in light of the above circumstances, and aims to realize optical fiber vibration sensing that has a simple configuration and is capable of identifying the position where vibration is applied. [Means for solving the problem]

[0008] For an optical transmission medium having multiple optical transmission paths, the interference signal is measured using a Mach-Zehnder interferometer from opposite directions, and the location where the vibration was added is identified by detecting the arrival time difference according to the location where the vibration occurred.

[0009] Specifically, the optical fiber vibration sensing device of the present disclosure comprises: an optical transmission medium having a plurality of optical transmission paths; a forward Mach-Zehnder interferometer that splits light from one end of the optical transmission medium into two optical transmission paths and inputs the light into the two optical transmission paths and combines and receives the light from the two optical transmission paths at the other end of the optical transmission medium; a reverse Mach-Zehnder interferometer that splits and inputs light from the other end of the optical transmission medium to two other optical transmission paths and combines and receives the light from the other two optical transmission paths at one end of the optical transmission medium; Equipped with.

[0010] Specifically, the optical fiber vibration sensing device of the present disclosure comprises: the optical transmission medium includes a first optical transmission path, a second optical transmission path, a third optical transmission path, and a fourth optical transmission path; The forward Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a forward measurement light source that emits light; a first optical multiplexer / split coupler that splits the light from the forward direction measurement light source into the first optical transmission path and the second optical transmission path, At the other end of the optical transmission medium, a second optical multiplexer / drop coupler that combines light from the first optical transmission path and light from the second optical transmission path; a forward direction measurement receiver that receives light from the second optical multiplexing / branching coupler, The reverse Mach-Zehnder interferometer comprises: At the other end of the optical transmission medium, a light source for backward measurement that emits light; a third optical multiplexer / split coupler that splits the light from the backward direction measurement light source into the third optical transmission path and the fourth optical transmission path, At one end of the optical transmission medium, a fourth optical multiplexer / drop coupler that combines light from the third optical transmission path and light from the fourth optical transmission path; a backward direction measurement optical receiver that receives light from the fourth optical multiplexing / splitting coupler; It is characterized by:

[0011] Specifically, the optical fiber vibration sensing device of the present disclosure comprises: the optical transmission medium includes a first optical transmission path, a second optical transmission path, a third optical transmission path, a fourth optical transmission path, a fifth optical transmission path, and a sixth optical transmission path; The forward Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a forward measurement light source that emits light; a first optical multiplexer / split coupler that splits light from the forward direction measurement light source into the first optical transmission path and the second optical transmission path; a forward direction measurement light receiver that receives light from the fifth optical transmission line, At the other end of the optical transmission medium, a second optical multiplexer / drop coupler that combines light from the first optical transmission path and light from the second optical transmission path and outputs the combined light to the fifth optical transmission path; The reverse Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a light source for backward measurement that transmits light to the sixth optical transmission line; a fourth optical multiplexer / drop coupler that combines light from the third optical transmission path and light from the fourth optical transmission path; a backward direction measurement optical receiver that receives light from the fourth optical multiplexing / splitting coupler, At the other end of the optical transmission medium, The optical fiber optical system further comprises a third optical multiplexer / brancher that branches the light from the sixth optical transmission path to the third optical transmission path and the fourth optical transmission path.

[0012] Specifically, the optical fiber vibration sensing device of the present disclosure comprises: the optical transmission medium includes a first optical transmission path and a second optical transmission path; the forward Mach-Zehnder interferometer and the backward Mach-Zehnder interferometer share a fourth-terminal fifth optical multiplexer / brancher coupler that multiplexes / branches light at one end of the optical transmission medium, and a fourth-terminal sixth optical multiplexer / brancher coupler that multiplexes / branches light at the other end of the optical transmission medium; The forward Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, A forward measurement light source is provided to emit light, splitting the light from the forward direction measurement light source into the first optical transmission path and the second optical transmission path by the fifth optical multiplexing / splitting coupler; At the other end of the optical transmission medium, a forward direction measurement receiver for receiving light; the light from the first optical transmission path and the light from the second optical transmission path are coupled by the sixth optical multiplexer / splitter coupler, and output to the forward direction measurement optical receiver; The reverse Mach-Zehnder interferometer comprises: At the other end of the optical transmission medium, a backward measurement light source that emits light of a wavelength different from that of the forward measurement light source; splitting the light from the backward direction measurement light source into the first optical transmission path and the second optical transmission path by the sixth optical multiplexing / splitting coupler; At one end of the optical transmission medium, a backward direction measurement receiver that receives light from the fifth optical multiplexing / splitting coupler; The light from the first optical transmission path and the light from the second optical transmission path are combined by the fifth optical multiplexing / branching coupler, and output to the backward direction measurement optical receiver. It is characterized by:

[0013] Specifically, the optical fiber vibration sensing device of the present disclosure comprises: the optical transmission medium includes a first optical transmission path, a second optical transmission path, a fifth optical transmission path, and a sixth optical transmission path; the forward Mach-Zehnder interferometer and the backward Mach-Zehnder interferometer share a fourth-terminal fifth optical multiplexer / brancher coupler that multiplexes / branches light at one end of the optical transmission medium, and a fourth-terminal sixth optical multiplexer / brancher coupler that multiplexes / branches light at the other end of the optical transmission medium; The forward Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a forward measurement light source that emits light; a forward direction measurement light receiver that receives light from the fifth optical transmission line, splitting the light from the forward direction measurement light source into the first optical transmission path and the second optical transmission path by the fifth optical multiplexing / splitting coupler; At the other end of the optical transmission medium, the light from the first optical transmission path and the light from the second optical transmission path are coupled by the sixth optical multiplexing / branching coupler, and output to the fifth optical transmission path; The reverse Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a backward direction measurement light source that transmits light of a wavelength different from that of the forward direction measurement light source to the sixth optical transmission line; a backward direction measurement optical receiver that receives light from the fifth optical multiplexing / splitting coupler, The light from the first optical transmission path and the light from the second optical transmission path are coupled by the fifth optical multiplexing / branching coupler; At the other end of the optical transmission medium, The light from the sixth optical transmission line is branched to the first optical transmission line and the second optical transmission line by the sixth optical multiplexing / branching coupler. It is characterized by:

[0014] Specifically, the optical fiber vibration sensing device of the present disclosure comprises: a first AD converter that converts an electrical signal from the forward direction measurement light receiver into an AD signal; a second AD converter that converts an electrical signal from the reverse direction measurement light receiver into an AD signal; an analysis device that identifies a location where vibration occurs using the signal from the first AD converter and the signal from the second AD converter; The present invention is characterized by further comprising:

[0015] Specifically, the optical fiber vibration sensing device of the present disclosure comprises: The optical transmission medium having the plurality of optical transmission paths is characterized in that it comprises a multi-core optical fiber cable having a plurality of optical fibers or a multi-core optical fiber having a plurality of cores.

[0016] Specifically, the optical fiber vibration sensing method of the present disclosure includes: a fixed-time data acquisition step of acquiring interference wave signals w1(t) and w2(t) from a forward Mach-Zehnder interferometer and a backward Mach-Zehnder interferometer in which the light travels in the opposite direction to that of the forward Mach-Zehnder interferometer, respectively; A cross-correlation calculation step of changing τ in formula (8) and determining τ when the correlation value (w1 * w2) (τ) is maximized as ΔT; (w1*w2)(τ) = Σ w1(t)×w2(τ-t) (8) a vibration generation position calculation step of calculating a distance Lv from the other end of the optical transmission line to the point where the vibration is applied using equation (4); Lv = (L-c2×ΔT)c1 / (c1+c2) (4) where L is the total length of the optical transmission medium having multiple optical transmission paths. c1 is the speed of light in the optical transmission line of the quasi-directional Mach-Zehnder interferometer c2 is the speed of light in the optical transmission line of the reverse Mach-Zehnder interferometer Equipped with. Effect of the Invention

[0017] The optical fiber vibration sensing device and optical fiber vibration sensing method disclosed herein can realize optical fiber vibration sensing capable of identifying the position where vibration is applied with a simple configuration. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing an example of the configuration of an optical fiber vibration sensing device according to the present disclosure. [Diagram 2] 1 is a diagram showing an example of the configuration of an optical fiber vibration sensing device according to the present disclosure. [Diagram 3] 1 is a diagram showing an example of the configuration of an optical fiber vibration sensing device according to the present disclosure. [Figure 4] 1 is a diagram showing an example of the configuration of an optical fiber vibration sensing device according to the present disclosure. [Diagram 5] 1 is a diagram showing an example of the configuration of an optical fiber vibration sensing device according to the present disclosure. [Figure 6] FIG. 2 is a diagram showing an example of processing of the optical fiber vibration sensing method of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings are assumed to indicate the same components.

[0020] (Embodiment of Basic Configuration) The configuration of the optical fiber sensing device of this embodiment is shown in Fig. 1. In Fig. 1, 1 denotes an optical transmission medium having a plurality of optical transmission paths, 10 denotes a forward Mach-Zehnder interferometer, and 11 denotes a backward Mach-Zehnder interferometer.

[0021] Examples include a multi-core optical fiber cable or a ribbon-type optical fiber cable having multiple optical fibers as the optical transmission medium, with multiple optical fibers as the multiple optical transmission paths, and a multi-core optical fiber or a multi-core optical fiber cable having multiple cores as the multiple optical transmission paths, with the cores of a multi-core optical fiber having multiple cores as the multiple optical transmission paths, with the optical transmission medium being a multi-core optical fiber or a multi-core optical fiber cable.

[0022] In the forward Mach-Zehnder interferometer 10, light is branched from one end of the optical transmission medium 1 having multiple optical transmission paths into two optical transmission paths and input, and the light from the two optical transmission paths is combined and received at the other end of the optical transmission medium 1 having multiple optical transmission paths. In the backward Mach-Zehnder interferometer 11, light is branched from the other end of the optical transmission medium 1 having multiple optical transmission paths into two other optical transmission paths and input, and the light from the other two optical transmission paths is combined and received at one end of the optical transmission medium 1 having multiple optical transmission paths. The forward Mach-Zehnder interferometer 10 and the backward Mach-Zehnder interferometer 11 have light traveling directions set to opposite directions.

[0023] In FIG. 1, when vibration is applied to an optical transmission medium 1 having multiple optical transmission paths, the corresponding vibration is also applied to the two optical transmission paths constituting the forward Mach-Zehnder interferometer 10. However, due to differences in the physical positions of the two optical transmission paths, the same vibration is not applied at exactly the same time. This is because there is a large difference between the speed of light transmitted through the two optical transmission paths and the speed of sound propagating in solids such as optical fiber cables, optical fiber coatings, and optical fibers. Here, a multi-core optical fiber is taken as an example of an optical transmission medium having multiple cores as multiple optical transmission paths. The speed of light in quartz constituting an optical fiber is approximately 200,000 km / sec, while the speed of sound in quartz constituting an optical fiber is approximately 5,740 m / sec. If the distance between adjacent cores in a multi-core optical fiber is approximately 20 μm, the time it takes for vibration to propagate between the cores is approximately 3.5×10 -9seconds. The distance that the light travels in the optical fiber during this time is approximately 0.7 m, whereas the wavelength of the light source used in the interferometer is 1.3 μm to 1.6 μm in the communications wavelength band. Therefore, since the light travels a distance equal to or greater than the wavelength while the vibration is propagating between the cores, even when the two optical transmission lines in a Mach-Zehnder interferometer are close to each other, the same vibration is not applied to the two optical transmission lines at the same time.

[0024] For this reason, the forward Mach-Zehnder interferometer observes an interference wave corresponding to the applied vibration. Similarly, the backward Mach-Zehnder interferometer can also observe an interference wave corresponding to the applied vibration.

[0025] The optical fiber sensing device of this embodiment may further include a first AD converter that performs AD conversion on the electric signal from the forward Mach-Zehnder interferometer, a second AD converter that performs AD conversion on the electric signal from the backward Mach-Zehnder interferometer, and an analyzer that identifies the location of vibration generation using the signal from the first AD converter and the signal from the second AD converter. The interference wave signals observed by the forward Mach-Zehnder interferometer and the backward Mach-Zehnder interferometer are input to the analyzer via the first AD converter and the second AD converter, respectively, and the analyzer identifies the location of vibration generation.

[0026] (Application embodiment 1) The configuration of the optical fiber sensing device of this embodiment is shown in Fig. 2. In Fig. 2, 1 is an optical transmission medium having a plurality of optical transmission paths, 20 is a first optical transmission path, 21 is a third optical transmission path, 30 is a second optical transmission path, 31 is a fourth optical transmission path, 100 is a light source for forward direction measurement, 101 is a light source for backward direction measurement, 200 is a photoreceiver for forward direction measurement, 201 is a photoreceiver for backward direction measurement, 300 is a first optical multiplexing / branching coupler, 310 is a second optical multiplexing / branching coupler, 301 is a third optical multiplexing / branching coupler, 311 is a fourth optical multiplexing / branching coupler, 400 is a first AD converter, 401 is a second AD converter, and 500 is an analysis device.

[0027] The optical fiber sensing device includes a forward Mach-Zehnder interferometer and a reverse Mach-Zehnder interferometer, the light of which travels in opposite directions.

[0028] The forward direction Mach-Zehnder interferometer includes, at one end of an optical transmission medium 1 having a plurality of optical transmission paths, a forward direction measurement light source 100 that transmits light, and a first optical multiplexing / branching coupler 300 that branches the light from the forward direction measurement light source 100 to a first optical transmission path 20 and a second optical transmission path 30. At the other end of the optical transmission medium 1 having a plurality of optical transmission paths, a second optical multiplexing / branching coupler 310 that combines the light from the first optical transmission path 20 and the light from the second optical transmission path 30, and a forward direction measurement optical receiver 200 that receives the light from the second optical multiplexing / branching coupler 310.

[0029] In the forward Mach-Zehnder interferometer, a forward measurement light source 100 at one end of an optical transmission medium 1 having a plurality of optical transmission paths transmits light, and a first optical multiplexing / branching coupler 300 branches the light from the forward measurement light source 100 to a first optical transmission path 20 and a second optical transmission path 30. A second optical multiplexing / branching coupler 310 at the other end of the optical transmission medium 1 having a plurality of optical transmission paths combines the light propagated through the first optical transmission path 20 and the light propagated through the second optical transmission path 30, and a forward measurement optical receiver 200 receives the light from the second optical multiplexing / branching coupler 310.

[0030] The backward Mach-Zehnder interferometer is provided with a backward measurement light source 101 that emits light at the other end of an optical transmission medium 1 having a plurality of optical transmission paths, and a third optical multiplexing / branching coupler 301 that branches the light from the backward measurement light source 101 to a third optical transmission path 21 and a fourth optical transmission path 31. At one end of an optical transmission medium 1 having a plurality of optical transmission paths, there are provided a fourth optical multiplexing / branching coupler 311 that combines light from a third optical transmission path 21 and light from a fourth optical transmission path 31, and a reverse direction measurement optical receiver 201 that receives light from the fourth optical multiplexing / branching coupler 311.

[0031] In the backward Mach-Zehnder interferometer, a backward measurement light source 101 at the other end of an optical transmission medium 1 having a plurality of optical transmission lines transmits light, and a third optical multiplexer / brancher coupler 301 branches the light from the backward measurement light source 101 to a third optical transmission line 21 and a fourth optical transmission line 31. A fourth optical multiplexer / brancher coupler 311 at one end of the optical transmission medium 1 having a plurality of optical transmission lines combines the light propagated through the third optical transmission line 21 and the light propagated through the fourth optical transmission line 31, and a backward measurement photoreceiver 201 receives the light from the fourth optical multiplexer / brancher coupler 311.

[0032] The optical fiber vibration sensing device of the present disclosure can realize optical fiber vibration sensing capable of identifying the position where vibration is applied with a simple configuration.

[0033] (Application embodiment 2) The configuration of the optical fiber sensing device of this embodiment is shown in Fig. 3. In Fig. 3, 1 is an optical transmission medium having a plurality of optical transmission paths, 20 is a first optical transmission path, 21 is a third optical transmission path, 30 is a second optical transmission path, 31 is a fourth optical transmission path, 40 is a fifth optical transmission path, 41 is a sixth optical transmission path, 100 is a forward direction measurement light source, 101 is a backward direction measurement light source, 200 is a forward direction measurement light receiver, 201 is a backward direction measurement light receiver, 300 is a first optical multiplexing / branching coupler, 310 is a second optical multiplexing / branching coupler, 301 is a third optical multiplexing / branching coupler, 311 is a fourth optical multiplexing / branching coupler, 400 is a first AD converter, 401 is a second AD converter, and 500 is an analysis device.

[0034] The optical fiber sensing device includes a forward direction Mach-Zehnder interferometer and a backward direction Mach-Zehnder interferometer, each of which has its light traveling in the opposite direction. The basic operating principle is the same as in Application Embodiment 1, but it differs from Application Embodiment 1 in that the forward direction measurement photoreceiver 200 of the forward direction Mach-Zehnder interferometer and the backward direction measurement light source 101 of the backward direction Mach-Zehnder interferometer are disposed at one end of the optical transmission medium 1 having a plurality of optical transmission paths.

[0035] The forward direction Mach-Zehnder interferometer includes a forward direction measurement light source 100 that transmits light at one end of an optical transmission medium 1 having a plurality of optical transmission paths, a first optical multiplexing / branching coupler 300 that branches the light from the forward direction measurement light source 100 to the first optical transmission path 20 and the second optical transmission path 30, and a forward direction measurement optical receiver 200 that receives light from the fifth optical transmission path 40. The other end of the optical transmission medium 1 having a plurality of optical transmission paths includes a second optical multiplexing / branching coupler 310 that combines the light from the first optical transmission path 20 and the light from the second optical transmission path 30 and outputs the combined light to the fifth optical transmission path 40.

[0036] In the forward Mach-Zehnder interferometer, a forward measurement light source 100 at one end of an optical transmission medium 1 having a plurality of optical transmission paths transmits light, and a first optical multiplexer / drop coupler 300 splits the light from the forward measurement light source 100 into a first optical transmission path 20 and a second optical transmission path 30. A second optical multiplexer / drop coupler 310 at the other end of the optical transmission medium 1 having a plurality of optical transmission paths combines the light propagated through the first optical transmission path 20 and the light propagated through the second optical transmission path 30, and outputs the combined light to a fifth optical transmission path 40. A forward measurement optical receiver 200 at one end of the optical transmission medium 1 having a plurality of optical transmission paths receives the light from the fifth optical transmission path 40.

[0037] The backward Mach-Zehnder interferometer includes, at one end of an optical transmission medium 1 having a plurality of optical transmission lines, a backward measurement light source 101 that transmits light to a sixth optical transmission line 41, a fourth optical multiplexing / branching coupler 311 that combines light from the third optical transmission line 21 and light from the fourth optical transmission line 31, and a backward measurement optical receiver 201 that receives light from the fourth optical multiplexing / branching coupler 311. At the other end of the optical transmission medium 1 having a plurality of optical transmission lines, a third optical multiplexing / branching coupler 301 that branches light from the sixth optical transmission line 41 to the third optical transmission line 21 and the fourth optical transmission line 31.

[0038] In the backward Mach-Zehnder interferometer, a backward measurement light source 101 at one end of an optical transmission medium 1 having a plurality of optical transmission lines sends light to a sixth optical transmission line 41. A third optical multiplexing / branching coupler 301 at the other end of the optical transmission medium 1 having a plurality of optical transmission lines branches the light propagated through the sixth optical transmission line 41 to a third optical transmission line 21 and a fourth optical transmission line 31. A fourth optical multiplexing / branching coupler 311 at one end of the optical transmission medium 1 having a plurality of optical transmission lines combines the light propagated through the third optical transmission line 21 and the light propagated through the fourth optical transmission line 31, and a backward measurement photoreceiver 201 receives the light from the fourth optical multiplexing / branching coupler 311.

[0039] The optical fiber vibration sensing device of the present disclosure can realize optical fiber vibration sensing capable of identifying the position where vibration is applied with a simple configuration. Also, the optical fiber vibration sensing device of the present disclosure can arrange the forward direction measurement light source 100, the backward direction measurement light source 101, the forward direction measurement optical receiver 200, and the backward direction measurement optical receiver 201, which are active devices, on the same side (one end of the optical transmission medium 1 having multiple optical transmission paths).

[0040] (Application embodiment 3) The configuration of the optical fiber sensing device of this embodiment is shown in Fig. 4. In Fig. 4, 1 is an optical transmission medium having a plurality of optical transmission paths, 20 is a first optical transmission path, 30 is a second optical transmission path, 100 is a light source for forward direction measurement, 101 is a light source for backward direction measurement, 200 is a photoreceiver for forward direction measurement, 201 is a photoreceiver for backward direction measurement, 320 is a fifth optical multiplexing / branching coupler, 330 is a sixth optical multiplexing / branching coupler, 400 is a first AD converter, 401 is a second AD converter, and 500 is an analysis device.

[0041] The optical fiber sensing device includes a forward Mach-Zehnder interferometer and a backward Mach-Zehnder interferometer, each of which has its light traveling in the opposite direction. The basic operating principle is the same as in Application Embodiment 1, but it differs from Application Embodiment 1 in that the forward Mach-Zehnder interferometer and the backward Mach-Zehnder interferometer share the same optical transmission line by using different wavelengths for the forward measurement light source 100 of the forward Mach-Zehnder interferometer and the backward measurement light source 101 of the backward Mach-Zehnder interferometer.

[0042] The forward Mach-Zehnder interferometer and the reverse Mach-Zehnder interferometer share a four-terminal fifth optical multiplexing / branching coupler 320 that is connected to a first optical transmission line 20 and a second optical transmission line 30 and multiplexes / branches light at one end of the optical transmission medium 1 having a plurality of optical transmission lines, and share a four-terminal sixth optical multiplexing / branching coupler 330 that is connected to the first optical transmission line 20 and the second optical transmission line 30 and multiplexes / branches light at the other end of the optical transmission medium 1 having a plurality of optical transmission lines.

[0043] The forward direction Mach-Zehnder interferometer includes a forward direction measurement light source 100 that transmits light, and a fifth optical multiplexing / branching coupler 320 that branches the light from the forward direction measurement light source 100 to the first optical transmission path 20 and the second optical transmission path 30, at one end of the optical transmission medium 1 having a plurality of optical transmission paths. A sixth optical multiplexing / branching coupler 330 that combines the light from the first optical transmission path 20 and the light from the second optical transmission path 30, and a forward direction measurement optical receiver 200 that receives the light from the sixth optical multiplexing / branching coupler 330, are included at the other end of the optical transmission medium 1 having a plurality of optical transmission paths.

[0044] In the forward direction Mach-Zehnder interferometer, a forward direction measurement light source 100 at one end of an optical transmission medium 1 having a plurality of optical transmission lines transmits light, and a fifth optical multiplexer / brancher coupler 320 branches the light from the forward direction measurement light source 100 to a first optical transmission line 20 and a second optical transmission line 30. A sixth optical multiplexer / brancher coupler 330 at the other end of the optical transmission medium 1 having a plurality of optical transmission lines combines the light propagated through the first optical transmission line 20 and the light propagated through the second optical transmission line 30, and a forward direction measurement photoreceiver 200 receives the light from the second optical multiplexer / brancher coupler 310.

[0045] The backward Mach-Zehnder interferometer is provided with a backward measurement light source 101 that emits light at the other end of an optical transmission medium 1 having a plurality of optical transmission paths, and a sixth optical multiplexing / branching coupler 330 that branches the light from the backward measurement light source 101 to a first optical transmission path 20 and a second optical transmission path 30. At one end of an optical transmission medium 1 having a plurality of optical transmission paths, there are provided a fifth optical multiplexing / branching coupler 320 that combines light from a first optical transmission path 20 and light from a second optical transmission path 30, and a reverse direction measurement optical receiver 201 that receives light from the fifth optical multiplexing / branching coupler 320.

[0046] In the backward Mach-Zehnder interferometer, a backward measurement light source 101 at the other end of an optical transmission medium 1 having a plurality of optical transmission lines transmits light, and a sixth optical multiplexer / brancher coupler 330 branches the light from the backward measurement light source 101 to the first optical transmission line 20 and the second optical transmission line 30. A fifth optical multiplexer / brancher coupler 320 at one end of the optical transmission medium 1 having a plurality of optical transmission lines combines the light propagated through the first optical transmission line 20 and the light propagated through the second optical transmission line 30, and a backward measurement photoreceiver 201 receives the light from the fifth optical multiplexer / brancher coupler 320.

[0047] The optical fiber vibration sensing device disclosed herein can realize optical fiber vibration sensing capable of identifying the position where vibration is applied with a simple configuration. Moreover, the optical fiber vibration sensing device disclosed herein can share the same optical transmission line by using different wavelengths for the forward Mach-Zehnder interferometer and the reverse Mach-Zehnder interferometer.

[0048] (Application embodiment 4) The configuration of the optical fiber sensing device of this embodiment is shown in Fig. 5. In Fig. 5, 1 is an optical transmission medium having a plurality of optical transmission paths, 20 is a first optical transmission path, 30 is a second optical transmission path, 40 is a fifth optical transmission path, 41 is a sixth optical transmission path, 100 is a forward direction measurement light source, 101 is a backward direction measurement light source, 200 is a forward direction measurement light receiver, 201 is a backward direction measurement light receiver, 320 is a fifth optical multiplexing / branching coupler, 330 is a sixth optical multiplexing / branching coupler, 400 is a first AD converter, 401 is a second AD converter, and 500 is an analysis device.

[0049] The optical fiber sensing device includes a forward Mach-Zehnder interferometer and a backward Mach-Zehnder interferometer, in which the travel directions of the light are set to be opposite to each other. The basic operating principle is the same as that of the application embodiment 1, but it differs from the application embodiment 1 in that the forward measurement light receiver 200 of the forward Mach-Zehnder interferometer and the backward measurement light source 101 of the backward Mach-Zehnder interferometer are disposed at one end of the optical transmission medium 1 having a plurality of optical transmission paths. In addition, it differs from the application embodiment 1 in that the forward measurement light source 100 of the forward Mach-Zehnder interferometer and the backward measurement light source 101 of the backward Mach-Zehnder interferometer use different wavelengths, so that the forward Mach-Zehnder interferometer and the backward Mach-Zehnder interferometer share the same optical transmission path.

[0050] The forward Mach-Zehnder interferometer and the reverse Mach-Zehnder interferometer share a four-terminal fifth optical multiplexing / branching coupler 320 that is connected to a first optical transmission line 20 and a second optical transmission line 30 and multiplexes / branches light at one end of the optical transmission medium 1 having a plurality of optical transmission lines, and share a four-terminal sixth optical multiplexing / branching coupler 330 that is connected to the first optical transmission line 20 and the second optical transmission line 30 and multiplexes / branches light at the other end of the optical transmission medium 1 having a plurality of optical transmission lines.

[0051] The forward direction Mach-Zehnder interferometer includes a forward direction measurement light source 100 that transmits light at one end of an optical transmission medium 1 having a plurality of optical transmission paths, a fifth optical multiplexing / branching coupler 320 that branches the light from the forward direction measurement light source 100 to the first optical transmission path 20 and the second optical transmission path 30, and a forward direction measurement optical receiver 200 that receives the light from the fifth optical transmission path 40. The other end of the optical transmission medium 1 having a plurality of optical transmission paths includes a sixth optical multiplexing / branching coupler 330 that combines the light from the first optical transmission path 20 and the light from the second optical transmission path 30 and outputs the combined light to the fifth optical transmission path 40.

[0052] In the forward Mach-Zehnder interferometer, a forward measurement light source 100 at one end of an optical transmission medium 1 having a plurality of optical transmission paths transmits light, and a fifth optical multiplexer / drop coupler 320 splits the light from the forward measurement light source 100 into a first optical transmission path 20 and a second optical transmission path 30. A sixth optical multiplexer / drop coupler 330 at the other end of the optical transmission medium 1 having a plurality of optical transmission paths combines the light propagated through the first optical transmission path 20 and the light propagated through the second optical transmission path 30, and outputs the combined light to a fifth optical transmission path 40. A forward measurement optical receiver 200 at one end of the optical transmission medium 1 having a plurality of optical transmission paths receives the light from the fifth optical transmission path 40.

[0053] The backward Mach-Zehnder interferometer includes, at one end of an optical transmission medium 1 having a plurality of optical transmission paths, a backward measurement light source 101 that transmits light to a sixth optical transmission path 41, a fifth optical multiplexing / branching coupler 320 that combines light from the first optical transmission path 20 and light from the second optical transmission path 30, and a backward measurement photoreceiver 201 that receives light from the fifth optical multiplexing / branching coupler 320. At the other end of the optical transmission medium 1 having a plurality of optical transmission paths, a sixth optical multiplexing / branching coupler 330 that branches light from the sixth optical transmission path 41 to the first optical transmission path 20 and the second optical transmission path 30 is provided.

[0054] In the backward Mach-Zehnder interferometer, a backward measurement light source 101 at one end of an optical transmission medium 1 having a plurality of optical transmission lines sends light to a sixth optical transmission line 41. A sixth optical multiplexing / branching coupler 330 at the other end of the optical transmission medium 1 having a plurality of optical transmission lines branches the light propagated through the sixth optical transmission line 41 to the first optical transmission line 20 and the second optical transmission line 30. A fifth optical multiplexing / branching coupler 320 at one end of the optical transmission medium 1 having a plurality of optical transmission lines combines the light propagated through the first optical transmission line 20 and the light propagated through the second optical transmission line 30, and a backward measurement photoreceiver 201 receives the light from the fifth optical multiplexing / branching coupler 320.

[0055] The optical fiber vibration sensing device of the present disclosure can realize optical fiber vibration sensing capable of identifying the position where vibration is applied with a simple configuration. Moreover, the optical fiber vibration sensing device of the present disclosure can arrange the forward direction measurement light source 100, the backward direction measurement light source 101, the forward direction measurement receiver 200, and the backward direction measurement receiver 201, which are active devices, on the same side (one end of the optical transmission medium 1 having a plurality of optical transmission paths). Furthermore, the optical fiber vibration sensing device of the present disclosure can share the same optical transmission path by using different wavelengths for the forward direction Mach-Zehnder interferometer and the backward direction Mach-Zehnder interferometer.

[0056] (Application embodiment 5) In the basic configuration embodiment and the application embodiments 1 to 4, the optical fiber sensing device may further include a first AD converter 400 that performs AD conversion on an electrical signal from a forward direction Mach-Zehnder interferometer (in embodiments 1 to 4, the forward direction measurement receiver 200), a second AD converter 401 that performs AD conversion on an electrical signal from a reverse direction Mach-Zehnder interferometer (in embodiments 1 to 4, the reverse direction measurement receiver 201), and an analysis device 500 that identifies the location of occurrence of vibration using the signal from the first AD converter 400 and the signal from the second AD converter 401.

[0057] If the total length of the optical transmission medium 1 having a plurality of optical transmission paths is L, and the distance from the other end of the optical transmission path to the point Pv where the vibration is added is Lv, the time T1 required for the interference wave caused by the vibration added at the point Pv to reach the other end of the optical transmission path of the forward Mach-Zehnder interferometer is given by T1 = Lv / c1 (1) Here, c1 is the speed of light in the optical transmission line of the forward Mach-Zehnder interferometer.

[0058] The time T2 required for the interference wave caused by the vibration applied at point Pv to reach one end of the optical transmission line of the reverse Mach-Zehnder interferometer is given by T2 = (L-Lv) / c2 (2) Here, c2 is the speed of light in the optical transmission line of the reverse Mach-Zehnder interferometer.

[0059] As a result, the time difference ΔT between when the interference wave caused by the vibration applied at point Pv reaches the other end of the optical transmission line of the forward Mach-Zehnder interferometer and when it reaches one end of the optical transmission line of the backward Mach-Zehnder interferometer is ΔT = T2-T1 = (L-Lv) / c2-Lv / c1 (3) From this, the distance Lv from the other end of the optical transmission line to the point Pv where the vibration is applied is obtained by equation (4). Lv = (L-c2×ΔT)c1 / (c1+c2) (4)

[0060] If the speed of light in the optical transmission path of both the forward and reverse Mach-Zehnder interferometers is c, then equation (4) becomes Lv = (Lc × ΔT) / 2 (5) For example, when the vibration application point Pv is at the midpoint of the optical transmission medium 1 having a plurality of optical transmission paths, ΔT = 0 (6) Equation (5) is Lv = L / 2 (7) From equation (7), the point Pv where the vibration is applied is located halfway through the optical transmission medium 1 having multiple optical transmission paths, and so the validity of equation (4) is demonstrated.

[0061] In this way, by measuring the time difference ΔT between when the interference wave caused by the vibration applied at point Pv reaches the other end of the optical transmission path of the forward Mach-Zehnder interferometer and when it reaches one end of the optical transmission path of the reverse Mach-Zehnder interferometer, the distance Lv from the other end of the optical transmission path of the forward Mach-Zehnder interferometer to the point Pv where the vibration is applied can be obtained.

[0062] The two interference waves observed at the same time by the forward direction measurement receiver 200 and the reverse direction measurement receiver 201 are denoted as w1(t) and w2(t). ΔT is equal to the shift amount when the cross-correlation value of w1(t) and w2(t) is at its maximum. In other words, it can be found by changing τ in the following equation and setting τ at the time when the correlation value (w1*w2)(τ) is at its maximum as ΔT. (w1*w2)(τ) = Σ w1(t)×w2(τ-t) (8)

[0063] The analysis device 500 takes in the interference wave signal through the first AD converter 400 and the second AD converter 401, calculates the cross-correlation at regular time intervals, and obtains ΔT, thereby making it possible to specify the distance Lv to the vibration occurrence position Pv. Thus, the points where vibration is applied can be obtained sequentially.

[0064] The analysis device 500 identifies the location of the vibration occurrence in consideration of the delay time of the optical signal from the other end of the optical transmission path to the forward direction measurement receiver 200, the delay time of the electrical signal from the forward direction measurement receiver 200 via the first AD converter 400 to the analysis device 500, the delay time of the optical signal from one end of the optical transmission path to the reverse direction measurement receiver 201, and the delay time of the electrical signal from the reverse direction measurement receiver 201 to the analysis device 500 via the second AD converter 401.

[0065] 6 shows a flowchart of the optical fiber position sensing method executed by the analysis device 500. In the fixed time data acquisition process 600, interference wave signals w1(t) and w2(t) are acquired from a forward direction Mach-Zehnder interferometer (forward direction measurement receiver 200 in application embodiments 1 to 4) and a backward direction Mach-Zehnder interferometer (for backward direction measurement receiver 201 in application embodiments 1 to 4) in which the light travels in the opposite direction to that of the forward direction Mach-Zehnder interferometer, respectively.

[0066] In the cross-correlation calculation step 601, τ in the formula (8) is changed, and τ when the correlation value (w1*w2)(τ) is maximized is obtained as ΔT. (w1*w2)(τ) = Σ w1(t)×w2(τ-t) (8)

[0067] In the vibration occurrence position calculation step 603, the distance Lv from the other end of the optical transmission line to the point where the vibration is applied is calculated using equation (4). Lv = (L-c2×ΔT)c1 / (c1+c2) (4) Here, L is the total length of the optical transmission medium having a plurality of optical transmission lines, c1 is the speed of light in the optical transmission line of the directional Mach-Zehnder interferometer, and c2 is the speed of light in the optical transmission line of the reverse Mach-Zehnder interferometer.

[0068] An effective time difference calculation step 602 may be provided between the cross-correlation calculation step 601 and the vibration occurrence position calculation step 603. The interference signals received by the forward direction measurement receiver 200 and the reverse direction measurement receiver 201 may have a poor signal-to-noise ratio (SNR) depending on the interference state, and may not be an effective time difference ΔT. Therefore, in the effective time difference calculation step 602, the maximum time difference ΔTmax expected from the longest distance L of the optical transmission medium 1 having multiple optical transmission paths is compared with the absolute value of ΔT, |ΔT| ≦ ΔTmax (9) If not, the process returns to the data acquisition step 600 for a certain period of time and starts over from data acquisition. Here, ΔTmax is obtained by the following formula. ΔTmax = max{L / c1,L / c2} (10) If the formula (9) is satisfied, the process proceeds to vibration occurrence position calculation step 603 .

[0069] As described above, the optical fiber vibration sensing device and optical fiber vibration sensing method disclosed herein can realize optical fiber vibration sensing that can identify the position where vibration is applied, with a simple configuration.

[0070] The analysis device of the present invention can also be realized by a computer and a program. The program can be recorded on a recording medium or provided via a communication network. [Industrial Applicability]

[0071] The present disclosure can be applied to the information and communications industry. [Explanation of symbols]

[0072] 1: Optical transmission medium having multiple optical transmission paths 10: Forward Mach-Zehnder interferometer 11: Reverse Mach-Zehnder interferometer 20: First optical transmission path 21: Third optical transmission path 30: Second optical transmission path 31: Fourth optical transmission line 40: Fifth optical transmission line 41: Sixth optical transmission line 100: Forward measurement light source 101: Light source for reverse measurement 200: Forward measurement receiver 201: Reverse direction measurement receiver 300: First optical splitter 310: Second optical splitter 301: Third optical splitter 311: 4th optical splitter 320: Fifth optical splitter 330: 6th optical splitter 400: First AD converter 401: Second AD converter 500:Analysis equipment

Claims

1. an optical transmission medium having a plurality of optical transmission paths; a forward direction Mach-Zehnder interferometer that splits light from one end of the optical transmission medium into two optical transmission paths and inputs the light into the two optical transmission paths at the other end of the optical transmission medium, and combines the light from the two optical transmission paths and receives the combined light at a forward direction measurement receiver; a backward Mach-Zehnder interferometer that splits light from the other end of the optical transmission medium into two other optical transmission paths and inputs the light, and combines the light from the other two optical transmission paths at one end of the optical transmission medium and receives the combined light with a backward measurement optical receiver; a first AD converter that performs AD conversion on an electrical signal from the forward direction measurement light receiver; a second AD converter that performs AD conversion on the electrical signal from the reverse direction measurement light receiver; an analysis device that identifies a location where vibration occurs using a signal from the first AD converter and a signal from the second AD converter; Equipped with The analysis device includes: Obtaining interference wave signals w1(t) and w2(t) from the first AD converter and the second AD converter, respectively; The τ in the following formula (8) is changed, and the τ when the correlation value (w1 * w2) (τ) is maximized is obtained as ΔT, an optical fiber vibration sensing device in which, when L is a total length of an optical transmission medium having the plurality of optical transmission paths, c1 is the speed of light in the optical transmission path of the forward direction Mach-Zehnder interferometer, and c2 is the speed of light in the optical transmission path of the reverse direction Mach-Zehnder interferometer, a distance Lv from the other end of the optical transmission path to a point where vibration is applied is calculated using the following equation (4): (w1*w2)(τ) = Σ w1(t)×w2(τ-t) (8) Lv = (L-c2×ΔT)c1 / (c1+c2) (4)

2. the optical transmission medium includes a first optical transmission path, a second optical transmission path, a third optical transmission path, and a fourth optical transmission path; The forward Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a forward measurement light source that emits light; a first optical multiplexer / split coupler that splits the light from the forward direction measurement light source into the first optical transmission path and the second optical transmission path, At the other end of the optical transmission medium, a second optical multiplexer / drop coupler that combines light from the first optical transmission path and light from the second optical transmission path; the forward direction measurement optical receiver that receives light from the second optical multiplexing / branching coupler, The reverse Mach-Zehnder interferometer comprises: At the other end of the optical transmission medium, a light source for backward measurement that emits light; a third optical multiplexing / branching coupler that branches the light from the backward direction measurement light source to the third optical transmission path and the fourth optical transmission path, At one end of the optical transmission medium, a fourth optical multiplexer / drop coupler that combines light from the third optical transmission path and light from the fourth optical transmission path; a backward direction measurement optical receiver that receives light from the fourth optical multiplexing / splitting coupler, 2. The optical fiber vibration sensing device according to claim 1, wherein the optical fiber vibration sensing device is a fiber optic vibration sensing device.

3. the optical transmission medium includes a first optical transmission path, a second optical transmission path, a third optical transmission path, a fourth optical transmission path, a fifth optical transmission path, and a sixth optical transmission path; The forward Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a forward measurement light source that emits light; a first optical multiplexer / split coupler that splits light from the forward direction measurement light source into the first optical transmission path and the second optical transmission path; the forward direction measurement optical receiver that receives light from the fifth optical transmission path, At the other end of the optical transmission medium, a second optical multiplexer / drop coupler that combines light from the first optical transmission path and light from the second optical transmission path and outputs the combined light to the fifth optical transmission path; The reverse Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a light source for backward measurement that transmits light to the sixth optical transmission line; a fourth optical multiplexer / drop coupler that combines light from the third optical transmission path and light from the fourth optical transmission path; the backward direction measurement optical receiver that receives light from the fourth optical multiplexing / branching coupler, At the other end of the optical transmission medium, a third optical multiplexing / branching coupler that branches the light from the sixth optical transmission path to the third optical transmission path and the fourth optical transmission path; 2. The optical fiber vibration sensing device according to claim 1, wherein the optical fiber vibration sensing device is a fiber optic vibration sensing device.

4. the optical transmission medium includes a first optical transmission path and a second optical transmission path; the forward Mach-Zehnder interferometer and the backward Mach-Zehnder interferometer share a fourth-terminal fifth optical multiplexing / branching coupler for multiplexing / branching light at one end of the optical transmission medium, and a fourth-terminal sixth optical multiplexing / branching coupler for multiplexing / branching light at the other end of the optical transmission medium; The forward Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, A forward measurement light source is provided to emit light, splitting the light from the forward direction measurement light source into the first optical transmission path and the second optical transmission path by the fifth optical multiplexing / splitting coupler; At the other end of the optical transmission medium, The forward direction measurement receiver is provided, the light from the first optical transmission path and the light from the second optical transmission path are coupled by the sixth optical multiplexing / branching coupler, and output to the forward direction measurement optical receiver; The reverse Mach-Zehnder interferometer comprises: At the other end of the optical transmission medium, a backward measurement light source that emits light of a wavelength different from that of the forward measurement light source; light from the backward direction measurement light source is split into the first optical transmission path and the second optical transmission path by the sixth optical multiplexing / splitting coupler; At one end of the optical transmission medium, The reverse direction measurement receiver is provided, The light from the first optical transmission path and the light from the second optical transmission path are coupled by the fifth optical multiplexing / branching coupler, and output to the backward direction measurement optical receiver.

2. The optical fiber vibration sensing device according to claim 1, wherein the optical fiber vibration sensing device is a fiber optic vibration sensing device.

5. the optical transmission medium includes a first optical transmission path, a second optical transmission path, a fifth optical transmission path, and a sixth optical transmission path; the forward Mach-Zehnder interferometer and the backward Mach-Zehnder interferometer share a fourth-terminal fifth optical multiplexing / branching coupler for multiplexing / branching light at one end of the optical transmission medium, and a fourth-terminal sixth optical multiplexing / branching coupler for multiplexing / branching light at the other end of the optical transmission medium; The forward Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a forward measurement light source that emits light; the forward direction measurement optical receiver that receives light from the fifth optical transmission path, splitting the light from the forward direction measurement light source into the first optical transmission path and the second optical transmission path by the fifth optical multiplexing / splitting coupler; At the other end of the optical transmission medium, the light from the first optical transmission path and the light from the second optical transmission path are coupled by the sixth optical multiplexing / branching coupler, and output to the fifth optical transmission path; The reverse Mach-Zehnder interferometer comprises: At one end of the optical transmission medium, a backward direction measurement light source that transmits light of a wavelength different from that of the forward direction measurement light source to the sixth optical transmission line; the backward direction measurement optical receiver that receives light from the fifth optical multiplexing / branching coupler, combining the light from the first optical transmission path and the light from the second optical transmission path by the fifth optical multiplexing / branching coupler; At the other end of the optical transmission medium, The light from the sixth optical transmission line is branched to the first optical transmission line and the second optical transmission line by the sixth optical multiplexing / branching coupler.

2. The optical fiber vibration sensing device according to claim 1, wherein the optical fiber vibration sensing device is a fiber optic vibration sensing device.

6. The optical fiber vibration sensing device according to any one of claims 1 to 5, characterized in that the optical transmission medium having the multiple optical transmission paths is a multi-core optical fiber cable having multiple optical fibers or a multi-core optical fiber having multiple cores.

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