JPH011935A - Optical fiber flood detection sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is applicable to, for example, computer rooms, semiconductor factories,
The present invention relates to an optical fiber water immersion detection sensor that is installed in places where water is averse, such as inside important document rooms and telecommunication cables, and that can accurately and quickly detect water damage in such places.

``Prior art and its problems'' Conventionally, this type of water immersion detection sensor has wired a W silver wire such as a bare wire, a paper insulated wire, or a plastic insulated wire in a predetermined position, and the warning wire is partially short-circuited. Electric type sensors that detect water intrusion are often used. Moreover, most of these electrical type water immersion detection sensors are point detection sensors in which a number of water immersion detection sensor parts are attached to a conductive wire.

However, such point detection systems have a problem in that they cannot accurately and quickly detect flooded areas because the number of locations where water can be detected is limited.

Additionally, because the warning wire has low sensitivity for detecting water intrusion, there was a problem that the water intrusion detection ability of the water intrusion detection sensor was poor.

Additionally, warning wires using metal conductors have a problem in that they cannot be used in sections where electromagnetic induction exists.

On the other hand, there is also a method described in Japanese Utility Model Application Laid-Open No. 62-25845, which uses an optical fiber and detects water immersion from its transmission loss. However, the conventional flood detection sensor using this optical fiber is a human detection sensor, and cannot solve the problem of not being able to accurately or quickly detect a flooded area. In addition, in this water immersion detection sensor, if a smooth plate is placed in contact with the optical fiber and is provided over the entire length of the optical fiber, water immersion can be detected over the entire length of the optical fiber, and the location of flooding can be detected. This can solve the problem of not being able to detect accurately and quickly to some extent, but if a plate is installed over the entire optical fiber line, the water intrusion detection area will become a large area, and it will not be flexible and flexible. This results in a sensor lacking in quality.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a flood detection sensor that can accurately and quickly detect a flooded area.

[Means for Solving the Problems] The present invention includes an optical fiber, a tension member attached to the optical fiber, and a water-absorbing material that expands in volume when water is absorbed, covering the entire circumference of the optical fiber and the tension member. and an expansion suppressing material provided on the outside of the water-absorbing material to suppress volumetric expansion of the water-absorbing material and to guide water from entering the outside air to the water-absorbing material, the optical fiber is connected from the center of the water-absorbing material. The solution to this problem was to configure the water intrusion detection sensor by placing it eccentrically.

``Function J'' The optical fiber water immersion detection sensor of the present invention has the following effects due to the above-described configuration.

That is, in the event of a flooding accident, the water-absorbing material near the flooded portion absorbs moisture and swells, causing volumetric expansion, or the volumetric expansion is suppressed in the portion where the expansion-suppressing material comes into contact. This pressing applies lateral pressure to the optical fiber, causing bending such as micro-hending in the optical fiber. Therefore, the increased loss of transmitted light due to microbending that occurs in the optical fiber can be detected by measuring reflected light such as backscattered light of the light incident from the input end of the optical fiber, and can be used to detect the occurrence of flooding accidents and their occurrence. Position can be detected accurately and quickly.

"Example" Hereinafter, a detailed explanation of the present invention will be given with reference to the drawings.

FIG. 1 is a diagram showing a first embodiment of the present invention, and reference numeral 1 in the figure indicates an optical fiber water immersion detection sensor (hereinafter abbreviated as sensor). This sensor 1 includes an optical fiber 2,
A tension member 3 attached to this optical fiber 2,
The optical fiber 2 and the tension member 3 are coated with a water absorbing material 4, and an expansion suppressing material 5 is provided on the outside of the water absorbing material 4. A tension member 3 is placed at the center of the water absorbing material 4, and the optical fiber 2 is placed eccentrically from the center of the water absorbing material 4 by the amount of the tension member 3. 'The above optical fiber 2
For this purpose, silica glass fiber, multi-component glass fiber or plastic fiber is used, and this bare optical fiber is coated with one or more layers of thermosetting silicone, urethane, ultraviolet curing polymer, etc. Optical fiber strands subjected to this process are preferably used. Further, as the optical fiber 2, it is particularly preferable to use a low-loss optical fiber used for ordinary communications. The sensor 1 shown in FIG. 1 may be configured with one optical fiber 2, or two or more optical fibers 2 may be arranged so as not to contact each other.

The tension member 3 is made of a bundle of high-tensile thin wires such as steel wire, glass fiber, or aromatic polyamide fiber. The outer diameter of the tension member 3 is preferably the same as or smaller than the outer diameter of the optical fiber 2.

The water-absorbing material 4 is preferably made of a synthetic VJJ fat echelastomer base mixed with a water-absorbing swelling material that expands in volume when it absorbs water, absorbs water from the outside, and causes the water-absorbing portion to expand in volume. It looks like this. Examples of materials suitable for the base of the water absorbing material 4 include styrene-butadiene rubber (SDR), ethylene-propylene rubber (EPR), isoprene rubber, butadiene rubber,
These include hydrocarbon synthetic rubbers such as butyl rubber, silicone rubber, fluororubber, elastomers of polyester compounds, and 6-type plastics. Also, water absorption 4
As the water-absorbing and swelling material, a material whose volume increases several hundred times by absorbing water is preferably used.

Examples of suitable water-absorbing and swelling materials include KI Gel (trade name, manufactured by Kuraray Co., Ltd.) and Acryhope (registered trademark, manufactured by Nippon Shokubai Kagaku Kogyo Ajishiki Co., Ltd.).

The above-mentioned expansion suppressing material 5 is a string-like material that does not expand when water is absorbed and has a certain tension that does not break due to the volumetric expansion of the water-absorbing material 4. For example, a material made of synthetic resin such as Tetoron thread is used. It is particularly suitable for use. Also,
The expansion suppressing material 5 may be wound around the surface of the water absorbing material 4 at a constant pitch as shown in FIG. 2, or may be provided in a woven structure as shown in FIG. It may be provided in a mesh shape as shown in the figure.

Next, an example of a method for manufacturing the sensor I having such a configuration will be described. First, an optical fiber 2 such as a long optical fiber strand or bare optical fiber having a predetermined inner and outer diameter and mode is held in contact with a tension member 3, and the tension member 3 is Then, a water absorbing material 4 of a predetermined thickness is coated. optical fiber 2
As a method for coating the water absorbing material 4 on the tension member, a melt extrusion coating method or the like is suitably used.

At this time, the optical fiber 2 and the tension member 3 are connected so that the tension member 3 is located at the center of the water absorbing material 4.
Adjust the position of. Next, a filamentous expansion suppressing material 5 is wound on the water absorbing material 4 at a constant pitch. This winding operation can be performed using a winding device or the like that winds the coating thread around the electric wire, optical fiber, etc. at an arbitrary pitch. Through the above operations, the desired sensor 1 is obtained.

The sensor I configured as described above detects the occurrence of a flooding accident in the following manner. First, a flooding accident occurs at the installation location of the sensor 1, and this moisture passes through the expansion suppressing material 5 and is adsorbed by the water absorbing material 4. The water-absorbing material 4 that has absorbed water swells and undergoes volumetric expansion, but since the expansion-suppressing material 5 is wound around the water-absorbing material 4, the volumetric expansion of the portion in contact with the expansion-suppressing material 5 is suppressed. As a result, the optical fiber 2 placed apart from the center of the sensor 1 is pressed and bent in accordance with the pressing of the expansion suppressing material 5, and microbending occurs in the area where the water intrusion accident occurred. In the portion where this microbending occurs, the transmission loss of the transmission light transmitted through the fiber 2 becomes large, so the occurrence of a flooding accident can be detected by sensing this increase in loss.

To measure the transmission loss of transmitted light transmitted through the optical fiber 2, as shown in FIG. 5, a light source is connected to one end of the optical fiber 2 in the sensor 1, and a light receiver is connected to the other end. However, as shown in FIG. It is used as a method to detect the location where microbending occurs.

FIG. 7 is a diagram showing an example of such a water immersion detection device 6, and this water immersion detection device 6 includes a pulse generator 7 and an L which input optical pulses from the input end of the optical fiber 2 in the sensor 1.
D (laser diode) and LED (light emitting diode)
a light-emitting section 9 consisting of a light-emitting element 8 such as a light-emitting element 8; a light-detecting section 10 having a light-receiving element such as an APD (avalanche photodiode) that receives reflected light pulses such as backscattered light from the optical fiber 2; an optical directional coupler (1) that controls the flow of the optical pulses from the optical fiber 2 and the optical pulses reflected from the optical fiber 2 in the sensor I; Arithmetic unit 12 that performs arithmetic processing
and a display section 13 that displays the processing results.

Next, a method of operating the water immersion detection device having such a configuration will be explained. For example, if a flooding accident occurs in the area indicated by X in Figure 7, the sensor
Water permeates into the water-absorbing material 4 in the X area, and the water-absorbing material 4 in the X area absorbs water and swells, causing volumetric expansion, but this expansion is suppressed because the filamentous expansion suppressing material 5 is wound around it. The volumetric expansion of the portion in contact with the stopper 45 is suppressed. As a result, the optical fiber 2 placed apart from the center of the sensor l is pressed and bent in accordance with the pressing of the expansion suppressing material 5, and
Microphone [j bending occurs in the optical fiber 2 within the area. The water immersion detection device 6 detects the increase in the loss of transmitted light due to the bending of the optical fiber 2 based on the time delay of reflected light pulses such as backscattered light returning to the input end of the optical fiber 2 and changes in the received light level. Detection. Then, the calculation unit 12 of the water immersion detection device 6 analyzes the measurement data of the reflected light pulses and determines the distance from the input end of the optical fiber 2 to the water immersion occurrence position. Next, by displaying this data on the display unit 13, a flooding accident in area X can be detected.

Next, in response to the occurrence of this flooding accident, immediate measures will be taken to deal with the flooding accident in Area X.

In such a flood detection system, at the position of the display part I3 of the flood detection device 6, it is possible to accurately and quickly detect a flood accident in a cable or room where the sensor 1 is installed in advance, such as in the X area. It is possible to do so.

Moreover, this sensor I has a tennoyon member 3 attached to the optical fiber 2, and the optical fiber 2 and the tennoyon member 3 are attached to each other.
The entire circumference is covered with a water-absorbing material 4 that expands in volume when water is absorbed, and an expansion-suppressing material 5 is provided on this water-absorbing material 4, so that the water absorption material 4/14 expands due to the penetration of water, and the expansion is suppressed (the fifth This volumetric expansion is partially suppressed to apply lateral pressure to the optical fiber 2, thereby causing bending such as micro-hending in the optical fiber 2, thereby increasing the transmission loss of the optical fiber 2. Therefore, bf is applied to all lines of optical fiber 2.
Since it is possible to detect water intrusion by itself, and water intrusion is detected by measuring the increase in the loss of transmitted light, it is possible to detect water intrusion with extremely high sensitivity. It is also possible to adapt tJ in areas where there is electromagnetic induction. Furthermore, as the fiber 2, it is used for normal communications, such as radar soto index, step index,
By using a low-loss optical fiber such as a single-mode optical fiber, long-distance installation is possible, and it can also be applied to water intrusion detection in long-distance cables.

In addition, since the tension member 3 is attached to the optical fiber 2, the loss of the optical fiber 2 after being coated with the water absorbing material 4 increases (
Initial loss) can be reduced, and the influence of expansion and contraction of the water absorbing material 4 due to temperature changes can be reduced, so resistance to environmental changes such as temperature changes can be improved. Furthermore, even when the sensor 1 receives tension, the tension member 3 shares a certain amount of the tension, thereby increasing the tensile strength of the optical fiber 2 and making it difficult for the optical fiber 2 to break.

Further, since the optical fiber 2 is arranged eccentrically from the center of the water absorbing material 4, the bending of the optical fiber 2 becomes large when the volume of the water absorbing material 4 expands, thereby increasing the sensitivity of water intrusion detection.

FIG. 8 is a diagram showing a second embodiment of the invention.

The sensor I according to the previous example had a structure in which the tennoyon member 3 was arranged at the center of the water absorbing material 4 and the optical fiber 2 was arranged eccentrically from the center of the water absorbing material 4.
4 has a structure in which both the optical fiber 2 and the tension member 3 are arranged eccentrically from the center of the water absorbing material 4.

The sensor 14 according to this example not only provides the same effect as the previous example, but also further improves the sensitivity of water intrusion detection because the optical fiber 2 is placed at a position further away from the center of the water absorbing material 4 than in the previous example. I can do it.

FIGS. 9 to 11 are diagrams showing a third embodiment of the present invention. In the first embodiment, the optical fiber 2 and the tension member 3 were arranged in parallel, but the sensor 15 according to this example is arranged with the tension saw/member 3 in the center, as shown in FIG. 1O. , this tension member 3 to 6
The optical fibers 2 are twisted together to form a 6-core unit, the outside of this unit is coated with a water-absorbing material 4, and the surface of this water-absorbing material 4 is wound with a thread-like expansion suppressing material 5. There is. The tension member 3 is arranged at the center of the water-absorbing material 4, and the optical fiber 2 is arranged eccentrically from the center of the water-absorbing material 4. Moreover, all six of the six-core optical fibers 2 twisted together in the tension member 3 may be optical fibers 2, or the optical fibers 2 and dummy wires may be used in combination.

Therefore, the number of optical fibers can be selected between 1 and 6.

Note that the surface of the 6-core unit may be directly coated with the water-absorbing material 4, but if it is covered with a material such as soft silicone rubber or compound and the 6-core unit is fixed in advance, Even after coating the water absorbing material 4, the loss value (i.e.,
There is an effect that can reduce the increase in (initial loss). Moreover, in this sensor 15, as shown in FIG.
Although the structure is such that the thread-like expansion suppressing material 5 is wound at a constant pitch on the surface of the water absorbing material 4, the expansion suppressing material 5 can be arranged in other ways, such as winding the expansion suppressing material 5 at a constant pitch. , as shown in FIG. 3 and FIG.
Alternatively, they may be arranged in a mesh pattern.

The sensor 15 according to this example has the same effect as the first embodiment described above, and also has six cores each having at least one optical fiber twisted around the tension member 3.
Since it is a core unit, it is possible to make the optical fiber 2 less likely to be damaged than in the first embodiment. In addition, even if the water absorbing material 4 expands or contracts due to temperature changes,
The influence on the transmission loss of the optical fiber 2 can be further reduced, and the resistance to environmental changes such as temperature changes can be further improved.

"Experiment example l" As an optical fiber, the core diameter is 50 μm and the cladding diameter is 125 μm.
A quartz-based graded index type multimode optical fiber with a relative refractive index difference of 1.0% in μm1 is coated with urethane acrylate and has an outer diameter of 10.3 mII+. A steel wire (tension member) is attached, and Acryhop (registered trademark, manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) is applied to 100 parts by weight of styrene-butadiene rubber over the entire circumference of these wires and steel wires.
The outer diameter of the water-absorbing material made by adding 5 parts by weight of
It was coated so that it became nun. At this time, a steel wire was placed in the center of the water absorbing material.

Next, an expansion suppressing material made of hard plastic and having a thickness of 0.311IIR was wound around the surface of this water-absorbing material.

The pitch interval of the expansion suppressing material at this time was 2.5 mm. Through the above operations, a sensor configured almost the same as that of the first embodiment described above was created.

Using the sensor with a total length of 2000 m thus created, a portion of it was immersed in water as shown in FIG. 12, and the increase in transmission loss was measured using an 0TDR (backscatter loss measuring device). That is, connect one end A of the sensor to 0TDR, and connect 30cI1 to position B, which is 500m away from this A.
1 was installed, the other end C of the sensor was connected to a power meter, and the increase in loss from the start of flooding was measured at 0 TDR.

0TDR used a light wavelength in the 1.3 μm band. Further, the initial transmission loss of this sensor was 0.82 dB/Km.

As a result, as shown in Figure 13, the loss begins to increase immediately after the sensor is immersed in water, and the loss increases rapidly from the start of immersion to about 10 minutes, and after that, it gradually increases and reaches a saturated state of deafness. reached. In this way, the above sensor was able to detect water intrusion very sensitively and quickly. In addition, when monitoring with 0TDR, 15
We were able to accurately confirm the flooded area located at 00m.

"Experiment Example 2" Using six of the same optical fiber strands as B used in Experiment Example 1, the six strands were twisted around a glass fiber tension member with an outer diameter of 0.3III11. Te6
It was made into a core unit. Next, the surface of this unit was coated with silicone rubber (hardness: Shore A36). The outer diameter of this coating was 1.5i+n+.

Next, apply the previous experimental example to the surface of this coating! A water-absorbing material having the same composition as the water-absorbing material used in was coated with an outer diameter of 4III11. Next, on the surface of this water-absorbing material, a thickness of 0.3 mm was applied.
+ Hard plastic deck expansion suppressing material with a pitch interval of 3
It was wound at a constant pitch of mm. Through the above operations, a sensor configured almost the same as that of the third embodiment described above was created.

A sensor with a total length of 1000 m created in this way is
As shown in FIG. 14, the increase in transmission loss was measured using almost the same method as in Experimental Example I above. That is,
Select one of the six optical fibers in the sensor, and connect one end of it to 0TDr (700m from E) to position F, with a 30cm submerged area. and connect the other end G of the sensor to the power meter.
The increase in loss from the start of flooding was measured by OTDR. O
'r' I) For rj, a light wavelength in the 1.371 m band was used. Also, the initial 1υ1 transmission loss of this sensor is 0.72
It was dr3/Km.

As a result, as shown in Figure 15, the loss increases immediately after the start of flooding, and the loss increases rapidly for about 10 minutes after the start of flooding, after which it increases steadily and reaches saturation. reached.

In this way, the above sensor was able to detect water intrusion very quickly and with high sensitivity. Furthermore, in the OT D R monitoring, it was possible to accurately confirm the flooded area 700 m away from point E.

"Effects of the Invention" As explained above, the sensor according to the present invention includes an optical fiber, a ten-no-yon member attached to the optical fiber, and a coating on the entire circumference of these optical fibers and the ten-no-yon member. The optical fiber is provided with a water-absorbing material that expands in volume, and an expansion-suppressing material that is provided outside the water-absorbing material to suppress the volumetric expansion of the water-absorbing material and to guide water intrusion from the outside to the water-absorbing material. The water absorbing material is arranged eccentrically from the center of the optical fiber, and the water absorbing material expands due to the penetration of water, and the expansion suppressing material partially suppresses this volumetric expansion, causing bends such as micro-henging in the optical fiber. Since the method of detecting water ingress is to increase the transmission loss of the optical fiber by 1 bit, it is possible to detect water intrusion over the entire length of the optical fiber.Also, it is possible to detect water intrusion by measuring the increase in the loss of transmitted light. This makes it possible to detect water intrusion with extremely high sensitivity.Also, electromagnetic induction can be applied in certain areas.Furthermore, it is possible to use low-loss optical fibers such as those used for normal communications. By using optical fibers, long-distance installation is possible, and it can also be applied to water intrusion detection in long-distance cables.

Further, by using a water immersion detection device such as a backscatter loss measuring device (OTDR) as a means for measuring the increase in optical fiber loss, it is possible to accurately detect the location of water inundation.

In addition, since a tension member is attached to the optical fiber,
It is possible to reduce the increase in loss (initial loss) of the optical fiber after coating with the water-absorbing material, and it is also possible to reduce the effect of expansion and contraction of the water-absorbing material due to temperature changes, etc. The resistance to environmental changes can be improved. Furthermore, even when the sensor is subjected to tension, the tensile member shares some of the tension, thereby increasing the tensile strength of the optical fiber and making it difficult for the optical fiber to break.

Furthermore, since the optical fiber is arranged eccentrically from the center of the water-absorbing material, the bending of the tip fiber increases when the volume of the water-absorbing material expands, thereby increasing the sensitivity of water intrusion detection.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the invention. FIGS. 2 to 4 are cross-sectional views of the sensor, and are diagrams for explaining an example of a method for arranging the expansion suppressing material in the sensor shown in FIG. 1, and FIG. FIG. 3 is a side view showing the second example of the method, FIG. 4 is a side view showing the third example, and FIGS. 5 and 6 are the sensors shown in FIG. 1. FIG. 7 is a schematic configuration diagram showing an example of a water immersion detection means using the water immersion detection means. FIG. 7 is a construction diagram showing a water immersion detection device used in the water immersion detection means shown in FIG. FIG. 8 is a diagram showing a second embodiment of the present invention, and is a cross-sectional view of the sensor. 9 to 11 are diagrams showing a third embodiment of the present invention, in which FIG. 9 is a cross-sectional view of the sensor, and FIG. 10 is a cross-sectional view of the sensor.
FIG. 11 is an enlarged perspective view of the main parts of the sensor shown in the figure, and FIG. 11 is a perspective view of the sensor shown in FIG. 9. FIG. 12 is a diagram for explaining an experimental example in which water intrusion detection was carried out using the sensor shown in FIG. 1. FIG. 13 is a diagram for explaining the results of the experimental example shown in FIG. 12, and is a graph showing the relationship between sensor immersion time and increase in loss. FIG. 15 is a diagram for explaining an experimental example in which water intrusion detection was carried out using the sensor shown in FIG. FIG. 2 is a graph showing the relationship between sensor immersion time and loss increase. 1, +4, +5...Sensor, 2...Optical fiber, 3
...Tennyon member, 4...Water absorption H15...Expansion suppressing material.

Claims (1)

[Claims] An optical fiber, a tension member attached to the optical fiber, a water-absorbing material that covers the entire circumference of the optical fiber and the tension member and expands in volume when water is absorbed, and a water-absorbing material provided outside the water-absorbing material that expands in volume when water is absorbed. An optical fiber water immersion detection sensor comprising: an expansion suppressing material that suppresses volumetric expansion and guides water intrusion from the outside to the water absorbing material, the optical fiber being arranged eccentrically from the center of the water absorbing material. .