Optical fiber sensing system and optical fiber sensing method

Abstract

The objective of the present disclosure is to enable optical fiber sensing based on measurement of backscattered light to be carried out with respect to an optical pathway that employs different optical fibers depending on a communication direction.　The present disclosure provides an optical fiber sensing system comprising a pathway selection optical switch, an optical test device, and a first optical circulator inserted into an optical fiber being measured, wherein: if communication light is directed toward the pathway selection optical switch, the first optical circulator is used to input test light into the optical fiber being measured, and the pathway selection optical switch is used to separate backscattered light from a communication network; and if the communication light is exiting the pathway selection optical switch, the pathway selection optical switch is used to input the test light from the optical test device into the optical fiber being measured, and the first optical circulator is used to divide the backscattered light from the communication network.

Description

[Technical Field]

[0001] The present disclosure relates to estimating the environment surrounding the optical fiber cables by utilizing the vibration of optical fiber cables already installed throughout the city. [Background technology]

[0002] An optical fiber sensing technology using backscattered light of test light has been proposed (see, for example, Non-Patent Document 1). Non-Patent Document 1 is an optical measurement technology for observing the state of an optical fiber, and the measurement is performed at only one end. Therefore, no opposing device is required. In Non-Patent Document 1, pulsed or continuous test light is input, and the backscattered light generated when the test light is scattered in the optical fiber is observed.

[0003] The relay optical fiber is configured as a network (NW: short for network) that combines a route-selective optical switch with an optical amplifier for long-distance transmission. The optical amplifier uses an erbium-doped fiber amplifier (EDFA) that can amplify WDM (Wavelength Division Multiplexing) signals all at once, and an optical isolator is used to limit transmission to one direction, a necessary characteristic of EDFA. Therefore, to achieve bidirectional communication, the relay optical fiber uses two optical fibers to carry the communication light back and forth.

[0004] Optical fiber sensing using test light as described in Non-Patent Document 1 is based on the premise that backscattered light propagates in the opposite direction to the test light in the same optical fiber, and optical fiber sensing cannot be performed in relay optical fibers in which the propagation direction is limited to one direction by an optical isolator. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] “Advances in distributed vibration sensing for optical communication fiber state visualization”, Optical Fiber Technology, Vol.57, 102263. 2020 [Non-patent document 2] NTT Information Network Research Laboratories, "World's first demonstration of communication equipment monitoring technology using vibration sensing in communication optical fiber as a sensor ~ Aims to grasp city environmental information comprehensively and utilize it for disaster prevention ~," NTT News Release, https: / / group.ntt / jp / newsrelease / 2021 / 09 / 27 / 210927a.html Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure aims to make it possible to perform optical fiber sensing based on measuring backscattered light for optical paths that use different optical fibers depending on the communication direction. [Means for solving the problem]

[0007] The optical fiber sensing system of the present disclosure comprises: a path-selective optical switch included in a communication network that propagates communication light; an optical testing device that emits test light and receives backscattered light that is the test light scattered in an optical fiber to be measured in the communication network; a first optical circulator inserted in the optical fiber to be measured; Equipped with The optical fiber sensing method of the present disclosure is carried out.

[0008] In the optical fiber sensing method disclosed herein, when the optical fiber to be measured is an optical fiber through which communication light is directed toward the path-selecting optical switch, the first optical circulator is used to input the test light into the optical fiber to be measured, and the path-selecting optical switch is used to separate the backscattered light from the communication network.

[0009] In the optical fiber sensing method disclosed herein, when the optical fiber to be measured is an optical fiber through which communication light exits the path selection optical switch, the path selection optical switch is used to input test light from the optical testing device into the optical fiber to be measured, and the first optical circulator is used to separate the backscattered light from the communication network.

[0010] The optical testing device may include an optical switch connected to the optical testing device, the first optical circulator, and the path selection optical switch, and the optical switch may output test light from the optical testing device to one of the first optical circulator and the path selection optical switch, and output the backscattered light separated by the other of the first optical circulator and the path selection optical switch to the optical testing device. In this case, a second optical circulator with three ports may be provided between the optical switch and the optical testing device, and the second optical circulator may output backscattered light input from the optical switch to a first port to a second port, and output test light input to the second port to the optical switch.

[0011] The propagation direction of communication light in each optical fiber connected to the path selecting optical switch may be only one direction. In this case, the optical fiber may include a first optical amplifier that amplifies communication light incident on the path selecting optical switch and a second optical amplifier that amplifies communication light output from the path selecting optical switch, wherein the first optical amplifier is connected to the first optical circulator, the first optical amplifier, and the path selecting optical switch in this order along the propagation direction of the communication light, and the second optical amplifier is connected to the path selecting optical switch, the second optical amplifier, and the first optical circulator in this order along the propagation direction of the communication light.

[0012] The above disclosures can be combined as much as possible. [Effects of the Invention]

[0013] The present disclosure can enable optical fiber sensing based on measuring backscattered light to be performed for optical paths that use different optical fibers depending on the communication direction. [Brief explanation of the drawings]

[0014] [Figure 1] An example of a network configuration using both a route-selective optical switch and an optical amplifier for long-distance transmission is shown. [Figure 2] 1 illustrates an example configuration of an optical fiber sensing system according to the present disclosure. [Figure 3] An example of optical fiber sensing using a communication optical fiber is shown below. [Figure 4] 1 illustrates an example configuration of an optical fiber sensing system according to the present disclosure. [Figure 5] 1 illustrates an example configuration of an optical fiber sensing system according to the present disclosure. [Figure 6] 1 illustrates an example configuration of an optical fiber sensing system according to the present disclosure. [Figure 7] 1 illustrates an example configuration of an optical fiber sensing system according to the present disclosure. [Figure 8] 1 illustrates an example configuration of an optical fiber sensing system according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, 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 indicate the same components.

[0016] (Network configuration) FIG. 1 shows an example of a network configuration that uses both a route-selecting optical switch and an optical amplifier for long-distance transmission. The route-selecting optical switch 11 is included in a communication network that propagates communication light and has a function of switching the path of the communication light, such as a wavelength switch. In this embodiment, an example is shown in which the route-selecting optical switch 11 connects optical fibers 12 and 13 of a first path on the NW side, optical fibers 14 and 15 of a second path on the NW side, and optical fibers 16 and 17 on the add / drop side. Optical amplifiers A12-1, A12-2, A13-1, A13-2, A14, A15, A16, and A17 are connected to the respective optical fibers.

[0017] The optical fibers 12 and 13 have different communication directions, the optical fibers 14 and 15 have different communication directions, and the optical fibers 16 and 17 have different communication directions. For example, the route selection optical switch 11 inputs communication light from the optical fiber 12 into the optical fiber 14 or 17, and inputs communication light from the optical fiber 15 into the optical fiber 13 or 17. The optical fiber 16 is used for communication in the Add direction, where light is added to the NW. The optical fiber 17 is used for communication in the Drop direction, where light is removed from the NW.

[0018] The path selection optical switch 11 has a plurality of ports for each path, and is capable of switching the connection of the ports. In this embodiment, an example is shown in which ports P12 and P13 for connection to optical fibers 12 and 13 are provided on the first path side, ports P14 and P15 for connection to optical fibers 14 and 15 are provided on the second path side, and ports P17 and P18 for connection to optical fibers 16 and 17 are provided on the add / drop side.

[0019] The communication light output by the path selection optical switch 11 to the optical fiber 17 is amplified by the optical amplifier A17. The communication light propagating through the optical fiber 16 is amplified by the optical amplifier A16 before being input to the path selection optical switch 11. The optical amplifier A16 functions as a first optical amplifier, and the optical amplifier A17 functions as a second optical amplifier.

[0020] The optical fibers 12 and 13 are connected to the adjacent path selection optical switch 26. The communication light output by the path selection optical switch 11 to the optical fiber 13 is amplified by the optical amplifier A13-1. The communication light propagating through the optical fiber 13 is amplified by the optical amplifier A13-2 before being input to the path selection optical switch 26. The communication light output by the path selection optical switch 26 to the optical fiber 12 is amplified by the optical amplifier A12-2. The communication light propagating through the optical fiber 12 is amplified by the optical amplifier A12-1 before being input to the path selection optical switch 11. For the path selection optical switch 11, the optical amplifier A12-1 functions as a first optical amplifier, and the optical amplifier A13-1 functions as a second optical amplifier. The optical fibers 14 and 15 are also connected to the adjacent path selection optical switch (not shown) and have a configuration similar to that of the optical fibers 12 and 13.

[0021] In this disclosure, optical fiber sensing by measuring backscattered light can be implemented for a communication optical fiber using two optical fibers for a round trip, utilizing a route-selective optical switch and an optical amplifier, as shown in FIG.

[0022] (Summary of the Disclosure) In the present disclosure, an optical circulator set in a specific direction for a specific wavelength corresponding to the test light is inserted outside the optical amplifiers A12-1, A13-1, A14, A15, A16, and A17 that are provided adjacent to the ports of the path selection optical switch 11.

[0023] When measuring an optical fiber such as optical fiber 12, in which communication light is directed toward the route-selecting optical switch 11, an optical circulator is used to input test light into the optical fiber, since test light cannot be input using the route-selecting optical switch 11. Backscattered light returns to the route-selecting optical switch 11, so it is extracted by the route-selecting optical switch 11 as is.

[0024] When measuring an optical fiber such as optical fiber 13, where communication light exits from the route-selecting optical switch 11, the communication light is input using the route-selecting optical switch 11, but the backscattered light does not return to the route-selecting optical switch 11. Therefore, an optical circulator is used to extract the backscattered light.

[0025] In this way, by using an optical circulator and a path-selecting optical switch 11 in combination, the present disclosure can separate communication light, fiber sensing test light, and backscattered light without causing any loss to them, thereby avoiding the directional propagation limitations of the optical amplifier and enabling optical fiber sensing.

[0026] (First embodiment) 2 shows an example of the configuration of the optical fiber sensing system of this embodiment. The optical fiber sensing system of this embodiment includes an optical testing device 21. The optical testing device 21 emits test light and receives backscattered light that is produced when the test light is scattered in the optical fiber.

[0027] When an optical fiber is subjected to a disturbance (bending, temperature change, strain, vibration, etc.), its state changes, and the state of the backscattered light also changes in response to this state change. By observing the state change of the backscattered light measured by the optical testing device 21, it is possible to observe the state change of the optical fiber, and the state of the disturbance applied to the optical fiber. In other words, by treating the optical fiber laid out for communication as a sensor and observing the backscattered light, it is possible to measure / estimate the disturbance applied to the optical fiber (bending, temperature change, strain change, vibration, etc.). The disturbance that can be measured depends on the measurement method and the type of scattered light being observed. The present disclosure can adopt any measurement method and observation target that can be used by the optical testing device 21.

[0028] FIG. 3 shows an example of optical fiber sensing using a communication optical fiber (see, for example, Non-Patent Document 2). FIG. 3(a) shows an example of vibrations propagating through an optical fiber laid underground when a car passes by. FIG. 3(b) shows an example of vibrations propagating through an optical fiber laid underground when a worker is performing construction or equipment inspection. FIG. 3(c) shows an example of vibrations of an optical fiber when an optical fiber or closure laid in the air on a utility pole is swayed by wind or other factors. As shown in FIGS. 3(a) to 3(c), the measurement results obtained by the optical testing device 21 are different. Communication optical fibers are already laid throughout a city, and simply by measuring them, the state of the surrounding environment can be estimated, and the information obtained by the estimation can be used for various purposes.

[0029] In this embodiment, in order to perform optical fiber sensing in the optical fiber 12, an optical circulator C12 is inserted into the optical fiber 12. The optical circulator C12 functions as a first optical circulator, and ports p11, p12, and p13 function as a first, second, and third port, respectively.

[0030] The optical fiber sensing system executes the optical fiber sensing method of the present disclosure. In the optical fiber sensing method of the present disclosure, when the optical fiber to be measured is an optical fiber from which communication light is directed to the path-selecting optical switch 11, the optical circulator C12 is used to input test light into the optical fiber 12 to be measured, and the path-selecting optical switch 11 is used to separate the backscattered light from the communication network.

[0031] In this embodiment, the measurement target is optical fiber 12. Communication light in optical fiber 12 propagates from an adjacent route selecting optical switch toward route selecting optical switch 11. In this case, port p11 of optical circulator C12 is connected to optical testing equipment 21, and port p13 of optical circulator C12 is connected to route selecting optical switch 11.

[0032] The optical circulator C12 outputs the test light that is incident on port p11 to port p12. This causes the test light to be incident on the optical fiber 12. The backscattered light scattered by the optical fiber 12 is incident on port p12 of the optical circulator C12. The optical circulator C12 outputs the test light that is incident on port p12 to port p13. This causes the backscattered light to be incident on the path selecting optical switch 11. The path selecting optical switch 11 outputs the backscattered light that is incident from the optical fiber 12 to port P24.

[0033] Thus, in this embodiment, the test light is input to port p11 of the optical circulator C12, and the backscattered light returns to port p12 of the optical circulator C12, exits from port p13, and is input to the path selecting optical switch 11. The backscattered light passes through port P24 of the path selecting optical switch 11 and is received by the optical testing equipment 21.

[0034] For selection of the path selection optical switch 11 and the optical circulator C12, an optical circulator 23 and an optical switch 22 may be used as necessary. The optical circulator 23 functions as a second optical circulator, and ports p21, p22, and p23 function as the first, second, and third ports, respectively.

[0035] The test light emitted from the optical testing device 21 is incident on port p22 of the optical circulator 23 and is emitted from port p23 of the optical circulator 23. Port p23 of the optical circulator 23 is connected to the optical switch 22, and the test light is incident on the optical switch 22. Meanwhile, backscattered light from the optical switch 22 is incident on port p21 and is emitted from port p22.

[0036] Furthermore, in this embodiment, different ports P31 and P32 of the optical switch 22 are connected to the path selection optical switch 11 and the optical circulator C12. The optical switch 22 outputs the test light input from port P33 to port P32, and outputs the backscattered light input from port P31 to port P34. As a result, in this embodiment, the test light from port p23 of the optical circulator 23 is incident on the optical circulator C12, and the backscattered light from port P24 of the path selection optical switch 11 is incident on port p21 of the optical circulator 23. In this way, by utilizing the optical circulator 23 and the optical switch 22, this embodiment enables the test light and backscattered light to propagate with low loss.

[0037] 4, the optical fibers 12 and 13 may be connected to a path-selecting optical switch 26 that is different from the path-selecting optical switch 11. In this case, the propagation of the test light can be blocked by the optical amplifier A12-2 on the opposite side.

[0038] If the test light and communication light have different wavelengths, a path-selecting optical switch 11 with a wavelength selection function may be used. This allows the path-selecting optical switch 11 to separate the communication light and the backscattered light, making it possible to perform communication and optical fiber sensing simultaneously.

[0039] Furthermore, the test light and the communication light may have the same wavelength. In this case, optical fiber sensing using the test light may be performed when no communication is taking place on the optical fiber 12 to be measured.

[0040] (Second embodiment) 5 shows an example of the configuration of the optical fiber sensing system of this embodiment. In this embodiment, an optical circulator C13 is inserted into the optical fiber 13 to perform optical fiber sensing in the optical fiber 13. The optical circulator C13 functions as a first optical circulator, and ports p11, p12, and p13 function as the first, second, and third ports, respectively.

[0041] In this embodiment, the object to be measured is the optical fiber 13. The communication light of the optical fiber 13 propagates from the route selecting optical switch 11 toward the adjacent route selecting optical switch. Therefore, the optical fiber to be measured is the optical fiber through which the communication light exits the route selecting optical switch 11. In this case, the port p11 of the optical circulator C13 is connected to the route selecting optical switch 11, and the port p13 of the optical circulator C13 is connected to the optical testing equipment 21.

[0042] When test light is input to any port P24 of the route selecting optical switch 11, the route selecting optical switch 11 outputs the test light to the optical fiber 13 under measurement. The test light is input to port p11 of the optical circulator C13 and output from port p12. This causes the test light to be input to the optical fiber 13. Backscattered light in the optical fiber 13 returns to port p12 of the optical circulator C13, is output from port p13, and is received by the optical testing equipment 21.

[0043] The optical circulator 23 and the optical switch 22 may be used as needed to select the path selection optical switch 11 and the optical circulator C13. In this embodiment, different ports P35 and P36 of the optical switch 22 are connected to the optical circulator C12 and the path selection optical switch 11. The optical switch 22 outputs the test light input from port P33 to port P36, and outputs the backscattered light input from port P35 to port P34. As a result, in this embodiment, the test light output from port p23 of the optical circulator 23 is input to port P24 of the path selection optical switch 11, and the backscattered light output from the optical circulator C13 is input to port p21 of the optical circulator 23. In this way, this embodiment makes it possible to propagate the test light and backscattered light with low loss by using the optical circulator 23 and the optical switch 22.

[0044] As shown in FIG. 6, the optical fibers 12 and 13 may be connected to a path-selecting optical switch 26 that is different from the path-selecting optical switch 11.

[0045] Furthermore, the test light and the communication light may have the same wavelength. In this case, optical fiber sensing using the test light may be performed when no communication is taking place on the optical fiber 13 to be measured.

[0046] Furthermore, an optical amplifier 25 may be provided at port P24 of the route selection optical switch 11.

[0047] (Third embodiment) 7 shows an example of the configuration of the optical fiber sensing system of this embodiment. In this embodiment, an optical circulator C16 is inserted into the optical fiber 16 to perform optical fiber sensing in the optical fiber 16. The optical circulator C16 functions as a first optical circulator, and ports p11, p12, and p13 function as the first, second, and third ports, respectively.

[0048] Communication light in optical fiber 16 propagates from a user terminal (not shown) toward route selecting optical switch 11. Therefore, the optical fiber to be measured is the optical fiber from which communication light heads toward route selecting optical switch 11. In this case, port p11 of optical circulator C16 is connected to optical testing equipment 21, and port p13 of optical circulator C16 is connected to route selecting optical switch 11.

[0049] The operation of the optical circulator C16 is similar to that of the optical circulator C12 of the first embodiment, if the optical fiber 12 is replaced with the optical fiber 16. However, in this embodiment, the path selection optical switch 11 outputs the backscattered light incident from the optical fiber 16 to the port P24.

[0050] In this embodiment, too, the optical circulator 23 and the optical switch 22 may be used as necessary to select the path selection optical switch 11 and the optical circulator C16. In this embodiment, different ports P31 and P37 of the optical switch 22 are connected to the path selection optical switch 11 and the optical circulator C16. The optical switch 22 outputs the test light input from port P33 to port P37, and outputs the backscattered light input from port P31 to port P34. As a result, in this embodiment, the test light output from port p23 of the optical circulator 23 is input to the optical circulator C16, and the backscattered light output from port P24 of the path selection optical switch 11 is input to port p21 of the optical circulator 23. In this way, this embodiment makes it possible to propagate the test light and backscattered light with low loss by using the optical circulator 23 and the optical switch 22.

[0051] If the test light and communication light have different wavelengths, a path-selecting optical switch 11 with a wavelength selection function may be used. This allows the path-selecting optical switch 11 to separate the communication light and the backscattered light, making it possible to perform communication and optical fiber sensing simultaneously.

[0052] Furthermore, the test light and the communication light may have the same wavelength. In this case, optical fiber sensing using the test light may be performed when no communication is taking place on the optical fiber 16 to be measured.

[0053] (Fourth embodiment) 8 shows an example of the configuration of the optical fiber sensing system of this embodiment. In this embodiment, an optical circulator C17 is inserted into the optical fiber 17 to perform optical fiber sensing using the optical fiber 17. The optical circulator C17 functions as a first optical circulator, and ports p11, p12, and p13 function as the first, second, and third ports, respectively.

[0054] The communication light of the optical fiber 17 propagates from the route selecting optical switch 11 toward a user terminal (not shown). Therefore, the optical fiber to be measured is the optical fiber from which the communication light exits the route selecting optical switch 11. In this case, port p11 of the optical circulator C17 is connected to the route selecting optical switch 11, and port p13 of the optical circulator C17 is connected to the optical testing equipment 21.

[0055] In this embodiment, the path selection optical switch 11 outputs the test light input to the port P24 to the optical fiber 17. This causes the test light to be incident on the optical fiber 17 under measurement. The operation of the optical circulator C17 is similar to that of the optical circulator C13 of the second embodiment, provided that the optical fiber 13 is replaced with the optical fiber 17.

[0056] In this embodiment, too, the optical circulator 23 and the optical switch 22 may be used as necessary to select the path selection optical switch 11 and the optical circulator C17. In this embodiment, different ports P36 and P38 of the optical switch 22 are connected to the path selection optical switch 11 and the optical circulator C17. The optical switch 22 outputs the test light input from port P33 to port P36, and outputs the backscattered light input from port P38 to port P34. As a result, in this embodiment, the test light output from port p23 of the optical circulator 23 is input to port P24 of the path selection optical switch 11, and the backscattered light output from port P13 of the optical circulator C17 is input to port p21 of the optical circulator 23. In this way, this embodiment makes it possible to propagate the test light and backscattered light with low loss by using the optical circulator 23 and the optical switch 22.

[0057] Furthermore, the test light and the communication light may have the same wavelength. In this case, optical fiber sensing using the test light may be performed when no communication is taking place on the optical fiber 17 to be measured.

[0058] Furthermore, an optical amplifier 25 may be provided at port P24 of the route selection optical switch 11. [Explanation of symbols]

[0059] 11, 26: Route selection optical switch 12, 13, 14, 15, 16, 17: Optical fiber A12-1, A12-2, A13-1, A13-2, A14, A15, A16, A17, A24, A25: Optical amplifiers 21: Optical test equipment 22: Optical switch 23, C12, C13, C16, C17: Optical circulator

Claims

1. a path-selective optical switch included in a communication network that propagates communication light; an optical testing device that emits test light and receives backscattered light that is the test light scattered in an optical fiber to be measured in the communication network; a first optical circulator inserted in the optical fiber to be measured; Equipped with When the optical fiber to be measured is an optical fiber through which communication light is directed to the path selection optical switch, Using the first optical circulator, the test light is incident on the optical fiber to be measured; separating the backscattered light from the communication network using the routing optical switch; When the optical fiber to be measured is an optical fiber through which communication light exits the route selection optical switch, Using the path-selecting optical switch, the test light from the optical testing device is input into the optical fiber under test; using the first optical circulator to separate the backscattered light from the communication network; Fiber optic sensing system.

2. an optical switch connected to the optical testing device, the first optical circulator, and the path selection optical switch; the optical switch outputs the test light from the optical testing device to one of the first optical circulator and the path selecting optical switch, and outputs the backscattered light separated by the other of the first optical circulator and the path selecting optical switch to the optical testing device; The optical fiber sensing system of claim 1 .

3. a second three-port optical circulator is provided between the optical switch and the optical testing device; the second optical circulator outputs the backscattered light incident on a first port from the optical switch to a second port, and outputs the test light incident on the second port to the optical switch; The optical fiber sensing system of claim 2 .

4. The propagation direction of communication light in each optical fiber connected to the path selection optical switch is only one direction. The optical fiber sensing system of claim 1 .

5. a first optical amplifier for amplifying communication light incident on the path selection optical switch; a second optical amplifier that amplifies the communication light output from the path selection optical switch; Equipped with the first optical amplifier is connected to the first optical circulator, the first optical amplifier, and the path selection optical switch in this order along the propagation direction of communication light; the second optical amplifier is connected in the order of the path selection optical switch, the second optical amplifier, and the first optical circulator along the propagation direction of communication light; The optical fiber sensing system of claim 4 .

6. a path-selective optical switch included in a communication network that propagates communication light; an optical testing device that emits test light and receives backscattered light that is the test light scattered in an optical fiber to be measured in the communication network; a first optical circulator inserted in the optical fiber to be measured; An optical fiber sensing method performed by an optical fiber sensing system comprising: When the optical fiber to be measured is an optical fiber through which communication light is directed to the path selection optical switch, Using the first optical circulator, the test light is incident on the optical fiber to be measured; separating the backscattered light from the communication network using the routing optical switch; When the optical fiber to be measured is an optical fiber through which communication light exits the route selection optical switch, Using the path-selecting optical switch, the test light from the optical testing device is input into the optical fiber under test; using the first optical circulator to separate the backscattered light from the communication network; Fiber optic sensing methods.

Images