JP2010019814A - Submergence detection module and submergence detection device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a submergence detection module for accurately detecting the water immersed position of an optical fiber cable, and to provide a submergence detecting device which uses the module. <P>SOLUTION: The submergence detection module 40 includes, inside a closure 30, at least one position detection optical fiber 41, having ends connected to two transmission path optical fibers 21A, 21B, respectively, and detecting the submergence of the inside of the closure 30 and a water-immersed position. The position detection optical fiber 41 is an optical fiber whose maximum value of the frequency of the Brillouin scattering light is in the range of 10.0-10.4 GHz. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inundation detection module for the purpose of improving the efficiency of maintenance and operation of an optical fiber cable and an inundation detection method using the same, and more particularly, to detect inundation in a closure provided in the middle of an optical fiber cable. The present invention relates to a water immersion detection module and a water immersion detection method using the same.

Conventionally, as a method of detecting water immersion in a closure that accommodates a connection portion provided in an optical fiber cable and a position where the submerged position is detected (an optical fiber cable immersion detection method), the optical fiber cable is immersed in the closure. There has been proposed a method of providing a means for bending the optical fiber core constituting the optical fiber and monitoring the optical loss generated in the optical fiber core due to the bending (see, for example, Patent Documents 1 and 2).
Means for bending the optical fiber core in the closure by water immersion is called a water immersion detection module.
JP 2006-38559 A JP 2006-139195 A

In the conventional method for detecting water immersion of an optical fiber cable, detection is performed by an optical pulse test method using OTDR (Optical Fiber Time Domain Reflectometry).
However, when the closure provided with the inundation detection module is close, it is difficult to detect the position of the closure, that is, the detection of the inundated position in the optical fiber core wire by the conventional inundation detection method using the OTDR.

  The present invention has been made in view of the above circumstances, and provides an inundation detection module capable of detecting a flooded position in an optical fiber cable with high accuracy and an inundation detection method using the same. Objective.

  In order to achieve the above object, the present invention provides at least a position detecting optical fiber that is connected to two transmission line optical fibers in a closure and detects water immersion and a water immersion position in the closure. There is provided an inundation detection module using an optical fiber having a maximum frequency of Brillouin scattered light of 10.0 GHz or more and 10.4 GHz or less as the position detecting optical fiber.

In the closure, apart from the position detection optical fiber, both ends are connected to two optical fiber for transmission line, respectively, and when the water is immersed in the closure, a pressing means for pressing the optical fiber is provided. It is preferable that at least one optical fiber for detecting inundation is provided.
The length of the position detecting optical fiber is preferably 4 m or more and 10 m or less.

  The present invention is an inundation detection method for detecting inundation and inundation position in a closure using the inundation detection module of the present invention, wherein the frequency of Brillouin scattered light of the position detecting optical fiber is detected using BOTDR. Inundation that detects the inundation position using the difference in the Brillouin frequency between the optical fiber that constitutes the transmission path and the optical fiber for position detection, while judging the inundation into the closure by detecting the amount of change in the maximum value Provide a detection method.

  The inundation detection method of the present invention is an inundation detection method for detecting the inundation and the inundation position in the closure using the inundation detection module of the present invention, and the position of the optical fiber constituting the transmission line using the BOTDR Using the fact that the Brillouin frequency of the detection optical fiber is different, the inundation position in the closure is detected, and using OTDR, the loss of the optical fiber for inundation detection is detected, and the inundation position together with the inundation in the closure is detected. It is characterized by detecting.

According to the submergence detection module of the present invention, at least one position detection optical fiber for detecting the submergence and the submergence position in the closure is connected to the two transmission line optical fibers in the closure. Since the optical fiber whose maximum value of the frequency of the Brillouin scattered light is 10.0 GHz or more and 10.4 GHz or less is used as the position detecting optical fiber, the Brillouin scattered light of the position detecting optical fiber is used using BOTDR. It is possible to detect the amount of change in the maximum value of the frequency and to detect the inundation position in the closure with high accuracy.
Further, at least one submerged detection optical fiber provided with a pressing means for pressing the optical fiber when both ends are connected to the two optical fibers for the transmission line in the closure and the submerged water enters the closure. Then, using OTDR, the loss of the optical fiber for water immersion detection can be detected, and the water immersion position in the closure can be detected with higher accuracy.

According to the inundation detection method of the present invention, the inundation detection method for detecting the inundation and the inundation position in the closure using the inundation detection module of the present invention, wherein the Brillouin of the position detecting optical fiber using BOTDR is provided. The amount of change in the maximum value of the frequency of the scattered light can be detected, and the inundation position can be detected with high accuracy together with the inundation into the closure.
Furthermore, if the loss of the optical fiber for inundation detection is detected using OTDR, the inundation position can be detected with higher accuracy together with the inundation into the closure.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode of a flood detection module and a flood detection method using the same according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing a first embodiment of an inundation detection module of the present invention and an inundation detection system using the same.
The inundation detection system 10 of this embodiment includes an optical fiber cable 20, a closure 30 provided in the middle thereof, an inundation detection module 40 provided in the closure 30, and light for transmission path that constitutes the optical fiber cable 20. A BOTDR (Brillouin Optical Fiber Time Domain Reflectometry) 50 is connected to one end of the fiber 21.

The inundation detection module 40 includes a position detection optical fiber 41 that detects inundation into the closure 30 and the inundation position.
Further, both ends of the position detecting optical fiber 41 are connected to the two transmission path optical fibers 21 </ b> A and 21 </ b> B in the closure 30. That is, the optical fiber cable 20 is composed of an optical fiber 22 including a transmission path optical fiber 21 (21A, 21B) and a position detection optical fiber 41.

  As the position detecting optical fiber 41, a Brillouin shift fiber in which the maximum value of the frequency of the Brillouin scattered light is different from the maximum value of the frequency of the rear Brillouin scattered light in an optical fiber generally laid as an optical transmission line. Specifically, an optical fiber having a maximum value of the frequency of the Brillouin scattered light of 10.0 GHz to 10.4 GHz is used.

The reason why an optical fiber having a maximum Brillouin scattered light frequency of 10.0 GHz to 10.4 GHz is used as the position detecting optical fiber 41 is, for example, that the maximum Brillouin scattered light frequency is 10.2 GHz. By using a Brillouin shift fiber, the BOTDR 50 is used to detect the change in the maximum value of the frequency of the Brillouin scattered light, and to accurately detect the installation position of the inundation detection module 40 and eventually the inundation position in the closure 30. be able to. In addition, when the inundation position in the closure 30 is detected, since the inside of the closure 30 is naturally inundated, the inundation into the closure 30 can be detected.
Here, the amount of change in the maximum value of the frequency of the Brillouin scattered light is based on the peak intensity of the maximum value of the frequency of the Brillouin scattered light in a specific frequency range (10.0 GHz to 10.4 GHz). It is the amount that has changed with respect to the peak intensity of the maximum value of the frequency of Brillouin scattered light. In addition, the peak intensity of the maximum value of the frequency of the Brillouin scattered light serving as a reference is the frequency of the Brillouin scattered light in a specific frequency range (10.0 GHz or more and 10.4 GHz or less) when there is no water immersion in the closure 30. It is the peak intensity of the local maximum value.

In the position detecting optical fiber 41, when the maximum value of the frequency of the Brillouin scattered light is less than 10.0 GHz, the measurement frequency range of BOTDR currently on the market is generally 9.9 GHz or more and 11.9 GHz or less. Therefore, it is difficult to detect the flooded position in the closure 30 by detecting the amount of change in the maximum value of the frequency of the Brillouin scattered light using the BOTDR 50. On the other hand, in the position detection optical fiber 41, when the maximum value of the Brillouin scattered light frequency exceeds 10.4 GHz, the maximum value of the Brillouin scattered light frequency of the standard optical fiber is 10.7 GHz or more and 10.9 GHz or less. Therefore, the frequency spectra overlap, and it becomes difficult to detect the amount of change in the maximum value of the frequency of the Brillouin scattered light in the position detecting optical fiber 41.
In this embodiment, a standard optical fiber having a maximum value of the frequency of Brillouin scattered light of 10.7 GHz or more and 10.9 GHz or less is used as the transmission line optical fiber 21.

  As the Brillouin shift fiber constituting the position detecting optical fiber 41, an optical fiber formed by doping a standard quartz optical fiber core with appropriate amounts of germanium (Ge) and fluorine (F) is used.

Furthermore, the length of the position detecting optical fiber 41 is 4 m or more and 10 m or less.
If the length of the position detection optical fiber 41 is less than 4 m, highly accurate position detection becomes difficult due to the relationship between the distance resolution of the BOTDR and the dynamic range. On the other hand, when the length of the position detecting optical fiber 41 exceeds 10 m, it is disadvantageous in terms of downsizing and cost of the module.

  According to the inundation detection module 40, the closure 30 includes the position detection optical fibers 41 having both ends connected to the two transmission path optical fibers 21 </ b> A and 21 </ b> B. Since an optical fiber having a maximum Brillouin scattered light frequency of 10.0 GHz or more and 10.4 GHz or less is used, the Brillouin frequency of the optical fiber constituting the transmission line and the position detecting optical fiber 41 of the BOTDR 50 are used. A difference in Brillouin frequency can be detected, and a flooded position in the closure 30 can be detected with high accuracy.

  In this embodiment, the inundation detection module 40 including the position detection optical fibers 41 respectively connected to the two transmission line optical fibers 21A and 21B in the closure 30 is illustrated. The inundation detection module of the invention is not limited to this. In the inundation detection module of the present invention, two or more position detection optical fibers having both ends connected to two transmission line optical fibers may be provided in the closure. When two or more position detection optical fibers are provided, the position detection optical fibers are connected in series at predetermined intervals and at equal intervals through the transmission line optical fibers.

Next, a flood detection method using the flood detection module 40 will be described.
The peak intensity of the maximum value of the frequency of the Brillouin scattered light of the position detection optical fiber 41 is detected using the BOTDR 50 in a state where the closure 30 is not immersed in advance. Then, the peak intensity of the maximum value of the frequency of the Brillouin scattered light is used as a reference value.
Next, the peak intensity of the maximum value of the frequency of the Brillouin scattered light of the position detection optical fiber 41 is detected every predetermined time or always using the BOTDR 50, and at the time of the detection with respect to the reference value of the peak intensity. When the peak intensity changes, that is, when the peak intensity change amount of the maximum value of the frequency of the Brillouin scattered light is detected, it is determined that the closure 30 has been submerged.

  In the measurement of the maximum value of the frequency of the Brillouin scattered light of the position detection optical fiber 41 using BOTDR, the wavelength of light input to the transmission line optical fiber 21 and the position detection optical fiber 41 is set to 1540 nm or more and 1560 nm or less, The pulse width of light is 10 nm or more and 100 nm or less.

  By the way, when the water is immersed in the closure 30, the peak intensity of the maximum value of the frequency of the Brillouin scattered light of the position detecting optical fiber 41 changes due to a temperature change caused by the water immersion or a strain change applied to the fiber.

  According to the inundation detection method of this embodiment, since the amount of change in the maximum value of the frequency of the Brillouin scattered light of the position detection optical fiber 41 is detected using the BOTDR 50, the inundation position is increased along with the inundation into the closure 30. It can be detected with accuracy.

  In this embodiment, the amount of change in the maximum value of the Brillouin scattered light of the single position detecting optical fiber 41 is detected by the BOTDR 50 using the inundation detection module 40, together with the inundation into the closure 30. Although the inundation detection method which detects an inundation position was illustrated, the inundation detection method of this invention is not limited to this. In the inundation detection method of the present invention, a BOTDR is used by using an inundation detection module having two or more position detection optical fibers each connected to two transmission line optical fibers in a closure. Thus, the amount of change in the maximum value of the frequency of the Brillouin scattered light of the two or more position detection optical fibers can be detected, and the submerged position can be detected together with the submerged water in the closure. In this case, the maximum values of the Brillouin scattered light frequencies of all the position detection optical fibers are detected every predetermined time or at all times, and the position detection optical fibers in which the peak intensity of the maximum value has changed are observed. It is determined that inundation has occurred at the location.

(Second embodiment)
FIG. 2 is a schematic configuration diagram showing a second embodiment of the inundation detection module of the present invention and an inundation detection system using the second embodiment.
In FIG. 2, the same components as those in the inundation detection system 10 shown in FIG.
The inundation detection system 60 of this embodiment includes an optical fiber cable 70, a closure 30 provided in the middle thereof, an inundation detection module 80 provided in the closure 30, and a transmission path light that constitutes the optical fiber cable 70. A BOTDR 50 connected to one end of the fiber 21 and an OTDR (Optical Fiber Time Domain Reflectometry) 90 connected to one end of a transmission line optical fiber 71 constituting the optical fiber cable 70 are schematically shown.

The immersion detection module 80 includes a position detection optical fiber 41 and an immersion detection optical fiber 81 provided with a pressing means 82 for pressing the optical fiber when it is immersed in the closure 30.
Further, both ends of the water immersion detection optical fiber 81 are connected to the two transmission path optical fibers 71A and 71B in the closure 30. In other words, the optical fiber cable 70 includes an optical fiber 72 including the optical fiber 22, the transmission path optical fiber 71 (71 </ b> A, 71 </ b> B), and the water immersion detection optical fiber 81.

As the transmission line optical fiber 71, a standard optical fiber having a maximum value of the frequency of Brillouin scattered light of 10.7 GHz or more and 10.9 GHz or less is used.
In addition, as the immersion detection optical fiber 81, a standard optical fiber having a maximum value of the frequency of Brillouin scattered light of 10.7 GHz or more and 10.9 GHz or less is used.
Furthermore, it is preferable that the length of the water optical fiber 81 for detecting immersion is equal to the length of the optical fiber 41 for position detection.

As shown in FIG. 3, the pressing means 82 is disposed between the portions of the water immersion detection optical fiber 81 that are fixed by the two optical fiber fixing members 85, 85.
Further, the pressing means 82 is roughly constituted by a swelling material 83 and a pressing member 84 provided on one surface of the swelling material 83.
The swelling material 83 is made of a material that swells when it absorbs water. When the water immersed in the closure 30 is absorbed, the pressing member 84 extends in a direction perpendicular to the longitudinal direction of the optical fiber 81 for water detection. Extrude (press).
The pressing member 84 is provided with a convex portion 84 a perpendicular to the longitudinal direction of the water detection optical fiber 81 in order to directly press a predetermined portion of the water detection optical fiber 81.

  Examples of the material forming the swelling material 83 include polyether-based urethane.

  According to the inundation detection module 80, the closure 30 includes the position detection optical fibers 41 having both ends connected to the two transmission line optical fibers 21A and 21B, respectively. While using the optical fiber whose maximum value of the frequency of the Brillouin scattered light is 10.0 GHz or more and 10.4 GHz or less, both ends are connected to the two optical fibers 71A and 71B for the transmission line in the closure 30, When the water is immersed in the closure 30, the optical fiber 81 for infiltration detection provided with the pressing means 82 for pressing the optical fiber is provided. Therefore, the maximum value of the frequency of the Brillouin scattered light of the position detecting optical fiber 41 using the BOTDR 50 is provided. The amount of change in water can be detected, and the loss of the optical fiber 81 for inundation detection can be reduced by using the OTDR90. Since it is possible to output, than the first embodiment described above, it is possible to detect the flooded position in the closure 30 with higher accuracy.

In this embodiment, in the closure 30, the position detection optical fiber 41 having both ends connected to the two transmission path optical fibers 21A and 21B, and the two transmission path optical fibers 71A and 71B, respectively. Although the inundation detection module 80 provided with the inundation detection optical fiber 81 having both ends connected to each other is illustrated, the inundation detection module of the present invention is not limited to this. In the inundation detection module of the present invention, two or more position detection optical fibers connected at both ends to the two transmission line optical fibers are provided in the closure, and for the two transmission lines. Two or more optical fibers for water immersion detection each having both ends connected to the optical fiber may be provided.
When two or more position detection optical fibers are provided, the position detection optical fibers are connected in series at predetermined intervals and at equal intervals through the transmission line optical fibers.
Similarly, when two or more inundation detection optical fibers are provided, the infiltration detection optical fibers are connected in series at predetermined intervals and at equal intervals through the transmission line optical fibers. .

Next, a flood detection method using the flood detection module 80 will be described.
The transmission loss of the flood detection optical fiber 81 is detected in advance using the OTDR 90 in a state where the closure 30 is not flooded. Then, the transmission loss of the flood detection optical fiber 81 is set as a reference value.
OTDR90 is used to detect the transmission loss of the inundation detection optical fiber 81, and when the transmission loss at the time of detection changes (increases) with respect to the reference value of the transmission loss, When the swelling material 83 that has absorbed the water swells, it is determined that the pressure applying member 84 has pressed the optical fiber 81 for water immersion detection.
Further, the BOTDR 50 is used to detect the Brillouin frequency of the position detection optical fiber 41, and the transmission path is determined by the difference between the Brillouin frequency of the optical fiber 21 and the Brillouin frequency of the position detection optical fiber 41 constituting the transmission path. Detect the location of the inundation detection module inside. By detecting the maximum value of the Brillouin frequency of the position detection optical fiber 41 located closest to the water immersion detection optical fiber 81 whose transmission loss has changed during the water immersion, the water immersion installed at what position from the BOTDR incident side It can be determined whether the module is a detection module, and the position can be detected.

  In the measurement of the maximum value of the frequency of the Brillouin scattered light of the position detection optical fiber 41 using BOTDR, the wavelength of light input to the transmission line optical fiber 21 and the position detection optical fiber 41 is set to 1540 nm or more and 1560 nm or less, The pulse width of light is 10 nm or more and 100 nm or less.

  In the measurement of the transmission loss of the water optical fiber 81 for detecting flooding using OTDR, the wavelength of the input light is set to 1500 nm to 1700 nm and the light pulse width is set to 5 nm to 2000 nm.

  According to the inundation detection method of this embodiment, the BOTDR 50 is used to detect the amount of change in the maximum value of the Brillouin scattered light of the position detection optical fiber 41, and the OTDR 90 is used to detect the inundation detection optical fiber 81. Since the change amount of the loss is detected, it is possible to detect the inundation position together with the inundation into the closure 30 with higher accuracy than in the first embodiment.

  In this embodiment, the amount of change in the maximum value of the frequency of the Brillouin scattered light of one optical fiber 41 for position detection is detected by the BOTDR 50 using the inundation detection module 80, and for inundation detection by the OTDR 90. Although the inundation detection method of detecting the amount of change in the loss of the optical fiber 81 and detecting the inundation position together with the inundation into the closure 30 is illustrated, the inundation detection method of the present invention is not limited to this. In the inundation detection method of the present invention, two or more position detection optical fibers each connected to the two transmission path optical fibers are provided in the closure, and the two transmission path optical fibers are used. Changes in the maximum value of the frequency of Brillouin scattered light of two or more position detection optical fibers by BOTDR using an inundation detection module having two or more inundation detection optical fibers each connected to both ends of the optical fiber. In addition to detecting the amount, the BOTDR can detect the amount of change in the transmission loss of two or more optical fibers for inundation detection, and detect the inundation position together with the inundation into the closure. In this case, the maximum value of the Brillouin scattered light frequency of all the position detection optical fibers and the transmission loss of all the submerged detection optical fibers are detected every predetermined time or at all times, and the peak of the maximum value is detected. It is determined that flooding has occurred at the position of the position detection optical fiber where the intensity is changed and the position of the water immersion detection optical fiber where the transmission loss is changed.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

"Example 1"
A standard transmission line optical fiber having a maximum Brillouin scattered light frequency of 10.7 GHz is prepared as 5 km (referred to as optical fiber A), a BOTDR is connected to one end thereof, and a water immersion detection module is connected to the other end. A plurality of them were connected in series at a predetermined interval. The interval between these inundation detection modules was set to an equal interval of 10 m.
As an inundation detection module, a position detection optical fiber having both ends connected to two transmission path optical fibers (optical fiber A) and two transmission path optical fibers (optical fiber A) in a closure. ), Both ends are connected to each other, and when the water is immersed in the closure, an optical fiber for detecting water provided with a pressing means for pressing the optical fiber is used.
As the position detecting optical fiber, a Brillouin shifted fiber having a length of 4 m and a maximum value of the frequency of the Brillouin scattered light of 10.0 GHz was used.
As the infiltration detection optical fiber, a standard optical fiber having a length of 4 m and a maximum value of the frequency of the Brillouin scattered light of 10.7 GHz was used.
Each submergence detection module is submerged and light with a wavelength of 1550 nm and a pulse width of 50 nm is input from one end of the optical fiber A by BOTDR, and backscattered light is observed to evaluate whether each submergence detection module position can be detected. did.
The evaluation results are shown in Table 1.

"Example 2"
The position detection optical fiber can be detected in the same manner as in Example 1 except that a Brillouin shift fiber having a length of 4 m and a maximum Brillouin scattered light frequency of 10.4 GHz is used as the position detection optical fiber. Was evaluated.
The evaluation results are shown in Table 1.

"Example 3"
As the position detection optical fiber, a Brillouin shift fiber having a length of 10 m and a maximum value of the frequency of the Brillouin scattered light of 10.0 GHz is used. As the inundation detection optical fiber, the length of 10 m, the frequency of the Brillouin scattered light is used. Except for using a standard optical fiber having a maximum value of 10.7 GHz, it was evaluated in the same manner as in Example 1 whether or not each inundation detection module position could be detected.
The evaluation results are shown in Table 1.

Example 4
As the position detection optical fiber, a Brillouin shift fiber having a length of 10 m and a maximum value of the Brillouin scattered light frequency of 10.4 GHz is used. As the inundation detection optical fiber, the length of 10 m and the frequency of the Brillouin scattered light is used. Except for using a standard optical fiber having a maximum value of 10.7 GHz, it was evaluated in the same manner as in Example 1 whether or not each inundation detection module position could be detected.
The evaluation results are shown in Table 1.

“Comparative Example 1”
A standard transmission line optical fiber having a maximum Brillouin scattered light frequency of 10.7 GHz is prepared as 5 km (referred to as optical fiber A), an OTDR is connected to one end thereof, and a water immersion detection module is connected to the other end. A plurality of them were connected in series at a predetermined interval. The interval between these inundation detection modules was set to an equal interval of 10 m.
As the inundation detection module, in the closure, both ends are respectively connected to the two optical fibers for transmission path (optical fiber A), and the inundation detection module is provided with a pressing means for pressing the optical fiber when it enters the closure. The one provided with a detection optical fiber was used.
As the infiltration detection optical fiber, a standard optical fiber having a length of 4 m and a maximum value of the frequency of the Brillouin scattered light of 10.7 GHz was used.
Each submergence detection module was submerged, and it was evaluated whether or not the submergence detection module position could be detected by detecting the amount of change in transmission loss of the submergence detection optical fiber from one end of the optical fiber A by OTDR.
The evaluation results are shown in Table 1.

“Comparative Example 2”
As the position detection optical fiber, a Brillouin shift fiber having a length of 3 m and a maximum value of the frequency of the Brillouin scattered light of 10.0 GHz is used. As the inundation detection optical fiber, the length of 3 m and the frequency of the Brillouin scattered light is used. Except for using a standard optical fiber having a maximum value of 10.7 GHz, it was evaluated in the same manner as in Example 1 whether or not each inundation detection module position could be detected.
The evaluation results are shown in Table 1.

“Comparative Example 3”
As the position detection optical fiber, a Brillouin shift fiber having a length of 10 m and a maximum value of the frequency of the Brillouin scattered light of 10.5 GHz is used. As the inundation detection optical fiber, the length of 10 m, the frequency of the Brillouin scattered light is used. Except for using a standard optical fiber having a maximum value of 10.7 GHz, it was evaluated in the same manner as in Example 1 whether or not each inundation detection module position could be detected.
The evaluation results are shown in Table 1.

“Comparative Example 4”
A standard transmission line optical fiber having a maximum Brillouin scattered light frequency of 10.7 GHz is prepared as 5 km (referred to as optical fiber A), a BOTDR is connected to one end thereof, and a water immersion detection module is connected to the other end. A plurality of them were connected in series at a predetermined interval. The interval between these inundation detection modules was set to an equal interval of 10 m.
As the inundation detection module, a position where both ends are connected to the two optical fibers for transmission path (optical fiber A) in the closure, and a pressing means is provided to press the optical fiber when it is submerged in the closure. The one provided with a detection optical fiber was used.
As the position detecting optical fiber, a Brillouin shifted fiber having a length of 10 m and a maximum value of the frequency of the Brillouin scattered light of 10.2 GHz was used.
Each submergence detection module is submerged and light with a wavelength of 1550 nm and a pulse width of 50 nm is input from one end of the optical fiber A by BOTDR, and backscattered light is observed to evaluate whether each submergence detection module position can be detected. did.
The evaluation results are shown in Table 1.

Here, the OK / NG determination regarding the position detection result of the inundation detection module according to the BOTDR method will be described.
4A and 4B are graphs showing Brillouin frequency data by BOTDR. FIG. 4A shows a case where position detection is OK determination, and FIG. 4B shows a case where position detection is NG determination. In FIG. 4, the horizontal axis represents distance, and the vertical axis represents the gain value when the Brillouin frequency is 10.2 GHz.
From FIG. 4A, it can be seen that when the position detection is OK, a high gain is obtained at the location where the position detection optical fiber is installed, and position detection is possible. On the other hand, FIG. 4B shows that when position detection is NG determination, a sufficient gain cannot be obtained at the position where the position detection optical fiber is installed, and position detection is difficult.

FIG. 5 is a graph showing a Brillouin frequency spectrum by BOTDR at a distance at which a position detection optical fiber is installed. FIG. 5A shows a case where the position detection is OK determination, and FIG. 5B is a case where the position detection is NG determination. Indicates.
FIG. 5A shows that when the position detection is OK determination, a Brillouin frequency spectrum that can determine the maximum value of the gain is obtained. On the other hand, FIG. 5B shows that when the position detection is NG determination, the Brillouin frequency spectrum cannot be obtained.

From the results of Table 1, in Examples 1 to 4, it was confirmed that each inundation detection module position can be detected.
In Comparative Example 1, the position of each inundation detection module could not be detected.
In Comparative Example 2, the peak intensity of the maximum value of the frequency of the Brillouin scattered light was not sufficient, and the position of each inundation detection module could not be detected.
In Comparative Example 3, the maximum value of the frequency of the Brillouin scattered light of the optical fiber A and the maximum value of the frequency of the Brillouin scattered light of the optical fiber for position detection overlap, and each inundation detection module position can be detected. There wasn't.
In Comparative Example 4, the position of each infiltration detection module could be detected before the position detection optical fiber was pressed by the pressing means, but the position detection optical fiber by the pressing means was detected by water immersion in the module. After the pressing, a sufficient peak intensity of the maximum Brillouin scattered light frequency could not be obtained, and the position of each inundation detection module could not be detected.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows 1st embodiment of the inundation detection module of this invention, and an inundation detection system using the same. It is a schematic block diagram which shows 2nd embodiment of the inundation detection module of this invention, and an inundation detection system using the same. It is a schematic block diagram which shows the press means which comprises 2nd embodiment of the inundation detection module of this invention. It is a graph which shows the Brillouin frequency data by BOTDR, (a) shows the case where position detection is OK determination, (b) shows the case where position detection is NG determination. It is a graph which shows the Brillouin frequency spectrum by BOTDR in the distance which installed the optical fiber for position detection, (a) shows the case where position detection is OK determination, (b) shows the case where position detection is NG determination.

Explanation of symbols

10, 60 ... Inundation detection system, 20, 70 ... Optical fiber cable, 21, 71 ... Optical fiber for transmission path, 30 ... Closure, 40, 80 ... Inundation detection module, 41. ..Optical fiber for position detection, 50 ... BOTDR, 81 ... Optical fiber for water detection, 82 ... Pressing means, 83 ... Swelling material, 84 ... Pressurizing member, 84a ... Convex part, 85 ... optical fiber fixing member, 90 ... OTDR.

Claims (5)

In the closure, at least one position detection optical fiber is connected to each of the two transmission line optical fibers, and detects water immersion and the water immersion position in the closure,
An infiltration detection module using an optical fiber having a maximum value of the frequency of Brillouin scattered light of 10.0 GHz to 10.4 GHz as the position detecting optical fiber.   In the closure, apart from the position detection optical fiber, both ends are connected to two optical fiber for transmission line, respectively, and when the water is immersed in the closure, a pressing means for pressing the optical fiber is provided. The flood detection module according to claim 1, comprising at least one optical fiber for flood detection.   3. The inundation detection module according to claim 1, wherein a length of the position detecting optical fiber is 4 m or more and 10 m or less. An inundation detection method for detecting inundation and inundation position in a closure using the inundation detection module according to claim 1,
The BOTDR is used to detect the amount of change in the maximum value of the Brillouin scattered light of the position detection optical fiber, thereby determining whether the closure is flooded, and the position detection optical fiber and the optical fiber constituting the transmission path. An inundation detection method characterized by detecting an inundation position using the fact that the Brillouin frequencies of optical fibers are different. An inundation detection method for detecting inundation and inundation position in a closure using the inundation detection module according to claim 2,
Using BOTDR, the position of the water in the closure is detected by utilizing the fact that the Brillouin frequency of the optical fiber constituting the transmission line and the optical fiber for position detection are different.
An inundation detection method comprising detecting a loss of the optical fiber for inundation detection using OTDR and detecting an inundation position together with inundation into the closure.

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