JP2879676B1 - Pressure sensor - Google Patents

Abstract

An object of the present invention is to provide a pressure sensor which has a simple structure of a container for accommodating a sensor section of an optical fiber cable, and which facilitates its manufacture. A circuit device is not stored in storage containers 5a, 5b,... 5n. For example, only single-core optical fiber sensors 3a, 3b,. The storage container is sealed by a synthetic resin covering 11 that freely deforms the surface shape in response to an externally applied stress and accurately applies an external pressure to the internal single-core optical fiber sensor. It is configured to For this reason, it is not necessary for the storage container itself to have pressure resistance, and it is sufficient if the storage container has a strength enough not to be damaged during transportation or laying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical fiber sensor disposed in a measurement area, in which light propagation characteristics are at sea level,
The present invention relates to a pressure sensor that detects a state of a pressure fluctuation such as a change in water level and a pressure change such as an atmospheric pressure, thereby detecting a pressure fluctuation state exerted on a measurement target.

[0002]

2. Description of the Related Art Displacement at the sea level is detected by applying pressure fluctuations corresponding to the rise and fall of the sea level to a quartz oscillator housed in a pressure vessel disposed on the sea floor, and detecting a change in the oscillation frequency. A quartz crystal type water pressure gauge is provided with a large number of circuit devices such as an AD converter, a transmission circuit including a counter circuit, and a power supply circuit system in a pressure-resistant container. For this reason, the number of components constituting the device in the pressure vessel is inevitably increased, and the pressure vessel itself has a considerable weight of, for example, 400 kg in air weight and 300 kg in water weight, and has a diameter of 26 cm, The axial length has a size as large as 2.2 m.

[0003]

Since the size of the pressure vessel containing such a crystal oscillator type water pressure gauge is large and considerable, the work of laying a large number of pressure vessels connected to the transmission cable on the sea floor is required. Is large and time-consuming. Furthermore, since the measuring instrument housed in the pressure vessel is made up of a number of components, not only is it time-consuming to manufacture, but also has the problem of increased manufacturing costs.Furthermore, maintenance for these many components is difficult. There is a problem that it is necessary.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a container for accommodating an optical fiber sensor, which does not require pressure resistance and which can respond to the applied measurement pressure. It is an object of the present invention to provide a pressure sensor which has a simple structure that causes distortion and is easy to manufacture.

[0005]

According to a first aspect of the present invention, there is provided a pressure sensor having at least one function of varying backscattered light intensity in response to an applied pressure. The optical fiber sensors are connected in series to a single-core optical fiber cable for light guiding, and the optical fiber sensors are stored one by one in each of the storage containers arranged in the measurement area. Wherein the storage container is provided with an optical fiber sensor serving as a pressure observation point on a non-metallic support, and is covered with a synthetic resin coating that is deformed by an externally applied pressure. , The optical fibers connected in series to each container except the last container
The sensors are stored individually, and in the final storage container,
The fiber optic sensor with the tail end is housed, and the incident light from the input end of the fiber optic cable is
After passing through the optical fiber sensors one after another, the light is guided to the last optical fiber sensor, and each backscattered light intensity corresponding to the pressure fluctuation applied to each optical fiber sensor of the multi-point observation array is detected at the incident end. , And is configured to detect a pressure fluctuation based on the detected value.

According to a second aspect of the present invention, there is provided a pressure sensor according to the present invention, wherein at least one optical fiber sensor having a function of changing the backscattered light intensity in accordance with the applied pressure is replaced with a multi-core optical fiber cable for guiding light. Are connected in series to each of the fiber lines constituting the optical fiber sensor, and the optical fiber sensors connected in series to each of the fiber lines are stored one by one in each of the storage container rows arranged in the measurement area, and as a whole, A pressure sensor forming a multi-point observation array, wherein the storage container is provided with an optical fiber sensor serving as a pressure observation point on a non-metallic support, and a synthetic resin covering that is deformed by an externally applied pressure. The optical fiber sensors connected in series for each fiber line are connected to each container except for the last container in each container row. And the last stage of the storage container houses the last, terminated optical fiber sensor, and the incident light from each input end of the multi-core optical fiber cable passes through the optical fiber sensor one after another. , Each backscattered light intensity corresponding to the pressure fluctuation applied to each optical fiber sensor of the multi-point observation array is detected at the input end, and the pressure fluctuation is determined based on the detected value. Is detected.

According to a third aspect of the present invention, there is provided a pressure sensor having a function of storing backscattered light intensities corresponding to the applied pressure while being housed one by one in storage containers arranged at n positions in a measurement area. A plurality of optical fiber cables for light guide formed by serially connecting n optical fiber sensors having the following formulas, and the first to nth optical fiber cables respectively connected to the plurality of optical fiber cables.
Among the sensors, the first and second optical fiber sensors are stored in a first storage container, the second and the second optical fiber sensors are stored in a second storage container, and the third and the third optical fiber sensors are stored in a third storage container. The optical fiber sensors are stored in a third storage container,..., The n-th optical fiber sensors having an end are stored in the n-th storage container, and each storage container is made of a non-metallic material. Each of the support members is provided with the optical fiber sensors, and is covered with a coating made of a synthetic resin that is deformed by an externally applied pressure, and the incident light from each incident end of each optical fiber cable passes through the optical fiber sensors one after another. Via
The light is guided to a fiber optic sensor having an end in the storage container at the last stage, and at each incidence end, a backscattered light intensity corresponding to a pressure fluctuation applied to each fiber optic sensor is detected, and based on the detected value, The pressure fluctuation is detected.

The pressure sensors according to the present invention are housed one by one in storage containers arranged in the measurement area, and
A single optical fiber with the function of varying the backscattered light intensity in response to the applied pressure and having a termination
A plurality of optical fiber cables in which sensors are connected in series are arranged side by side, and the storage container is provided with an optical fiber sensor individually on a non-metallic support, and is covered with a synthetic resin covering that is deformed by an externally applied pressure. And each incident end of the optical fiber cable is configured to face each light source, and the incident light of each incident end of each optical fiber cable is guided to each optical fiber sensor via each optical fiber cable, At each incident end, the backscattered light intensity of each optical fiber sensor that fluctuates according to the pressure fluctuation applied to each storage container is detected, and the pressure fluctuation is detected based on the detected value.

According to a fifth aspect of the present invention, there is provided a pressure sensor which is housed one by one in a storage container arranged in a measurement area, and has a function of varying transmitted light intensity in accordance with applied pressure. A plurality of optical fiber cables for light guiding in which the optical fiber sensors are connected in series are arranged in parallel, and the storage container stores the optical fiber sensors,
Each of the outgoing optical fiber cables having a light incident end opposed to the light source, each of which is covered with a synthetic resin covering that is distorted by an externally applied pressure, is connected to one end of an optical fiber sensor in each storage container. In addition, by configuring the respective light emitting portions of the return optical fiber cable connected to the other end of the optical fiber sensor to face the photodetector, the pressure applied to the container via the cover is reduced. , Based on the detection value of the transmitted light intensity from the optical fiber sensor that changes in response to the pressure.

According to the pressure sensor of the present invention, a single optical fiber sensor having a function of displacing the phase in accordance with the applied pressure is connected in series to the optical fiber cable for guiding light, and the optical fiber is connected to the optical fiber cable. A pressure sensor of a type in which sensors are stored one by one in storage containers arranged at multiple positions in a measurement area, wherein the storage container includes the optical fiber sensor on a non-metallic support and has an externally applied pressure. One end of the optical fiber sensor is covered with a synthetic resin covering that is distorted by the end of the optical fiber cable for outgoing light guide of length L from the light incident end facing the light source to the storage container, Optical fiber
The other end of the sensor is connected to an end of an optical fiber cable for returning light guiding of the same length L from the storage container to the light emitting end facing the phase comparison device, and provided for the reference light guide provided in the storage container. Each end of the folded portion of the optical fiber cable is connected to the end of the optical fiber cable for the reference light going path having the length L from the light incident end facing the light source to the storage container, and from the storage container to the phase comparison device. It is configured to be connected to the end of an optical fiber cable for the reference optical return path of the same length L to the light emitting end, and the phase displacement light from the optical fiber sensor and the reference from the optical fiber cable for the reference optical return path By comparing the phase of the light with the phase of the optical fiber cable, the measurement error due to the external stimulus generated in the optical fiber cable for the light guide can be compared with the optical fiber cable for the reference light guide. Clear the measurement error based on external stimuli that occur, and detecting a phase shift light only fiber optic sensor accommodating container.

According to a third aspect of the present invention, there is provided a pressure sensor according to the third aspect, wherein the plurality of light sources have the same carrier wavelength or different carrier wavelengths.

The pressure sensor of the present invention according to claim 8 is characterized in that the carrier wavelengths of the light sources are the same carrier wavelength or different carrier wavelengths.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the pressure sensor of the present invention will be described below.
The embodiment will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention, in which a backscattered light intensity is measured to detect a fluctuation state of a stress applied to, for example, a single-core optical fiber sensor connected in series. , FIG. 2A is a cross-sectional view of the storage container as viewed from the broken line AA in FIG. 1, and FIG.
For example, a perspective view of the storage container connected to the single-core armored cable 1 and FIG. 2 (C) receives pulsed light, for example, the input end and the end of a single-core optical fiber cable, and a part of the cable. FIG. 3 is a diagram schematically showing the generation of backscattered light from, for example, a single-core optical fiber sensor.

In FIG. 1, storage containers 5a, 5a laid at multiple locations on the sea floor to form a measurement network.
Each of b,... 5n has a closed loop connected in series to a single-core light guiding optical fiber cable 2 formed in a loop shape or a meandering shape provided in an armored cable or a non-armored cable 1. Multiple single-core optical fibers
Each of the sensors 3a, 3b,... And the single-core optical fiber sensor 3n having the terminal end 42 is housed therein. The single-core optical fiber cable 2 is connected to the single-core optical fiber sensor 3a of the first storage unit 5a.
End 5a ', its closed loop 3a, and the other end 5a "
Through the end of the fiber optic sensor 3b, the closed loop 3b, and the other end 5b ", and finally the n-th container 5b". 5n is connected to one end 5n 'of a single-core optical fiber sensor 3n having a termination 42.

Referring to FIGS. 2A and 2B, the exterior,
Or, a storage container 5 connected to a non-exterior, for example, a single-core cable 1 via a T-shaped light branching member 6.
a, 5b,..., 5n are for storing, for example, only a single-core optical fiber sensor, and the space of the storage container is exterior or non-exterior,
It is isolated from the space of the single-core cable 1. As described above, the storage containers 5a, 5b,..., 5n store, for example, only a single-core optical fiber sensor, and apply a measurement pressure to the single-core optical fiber sensor via a cover 11 described later. It is not necessary to provide the container itself with pressure resistance as in the case of a container for accommodating a circuit device or the like. For this reason, a single-core optical fiber sensor that forms a closed loop on the surface of a non-metallic material, for example, a synthetic resin frame or a substrate 10 made of a synthetic resin having a strength not to be damaged during transportation or installation. 3a, the surface shape is freely deformed in response to an externally applied stress,
An end of the cover 11 is fastened to the substrate 10 by a fastening member 12 by a cover 11 made of a synthetic resin configured to accurately apply an external pressure to an internal single-core optical fiber sensor.
Is firmly fixed so as to be sealed in a liquid-tight manner on the side surface.

A light source 7 for generating pulsed light is provided at each branch end of the Y-type optical fiber 9 facing the incident end 41 of the single-core optical fiber cable 2 in the single-core armored cable 1.
Detector 8 for detecting backscattered light sequentially transmitted from single-core optical fiber sensors 3a, 3b,.
Are provided respectively.

Although the above-described optical fiber sensor has been described as an example in which the optical fiber sensor is formed in a meandering shape, a roll shape, or a loop shape, it can be formed as described below. That is, after winding a single-core optical fiber cable around the outer periphery of a cylindrical body or a square columnar body, this cylindrical body,
Alternatively, the rectangular column is removed, and then the outer surface of a single-core optical fiber cable having a cylindrical or rectangular column is molded, and this is formed as a single-core optical fiber sensor. Can be configured to be installed on a non-metallic substrate. At this time, the detection sensitivity can be improved by increasing the length of a single-core optical fiber cable wound around a cylindrical body or a rectangular columnar body.

The operation of the pressure sensor constructed as described above will be described. As shown in FIG. 2C, the incident pulse light generated from the light source 7 is applied to the incident end 41 of the single-core optical fiber cable 2. When the light pulse is incident, it is backscattered at the incident end 41, and a part of the light pulse that has traveled along the single-core optical fiber cable 2 is partially stored in the storage containers 5a, 5b,.
, a single optical fiber sensor 3a, 3b,...
3n, the light is backscattered and finally attenuated in response to the external stress applied to each of the single-core optical fiber sensors 3a, 3b,. The pulse is backscattered at terminal 42.
In this way, by detecting the intensity of the light scattered one after another by the detector 8, each of the storage containers 5a, 5b,
... It is possible to detect for each sensor a pressure change based on a sea level displacement due to a tsunami, a wave, or the like on the sea surface above the 5n installation position. For this reason, for example, a change in the sea level in a wide area can be detected for each sensor installation position.

Although a measurement sequence in which a plurality of optical fiber sensors are connected in series to a single-core optical fiber cable has been described, at least one or more optical fiber sensors are provided for each fiber line constituting a multi-core optical fiber cable. By connecting them, a plurality of measurement columns can be formed. In this case, each optical fiber sensor connected in series to each of the plurality of measurement rows is configured to be individually stored in each of the storage container rows, and a light source and a light source are provided at each incidence end of the multi-core optical fiber cable 2. Obviously, the arrangement of the backscattered light detector for measurement is the same as in the case of the single-core optical fiber cable described above.

Next, referring to FIG. 3 showing a second embodiment which is a modified example of the first embodiment, for example, ten fiber wires arranged side by side in the multi-core armored cable 1A. Fiber optic cables 2a, 2b,
.. 1st to 1st connected in series to each of 2j
Multi-core optical fiber sensors 3a, 3 belonging to the 0th
A pressure sensor in which b,..., 3j are stored in ten storage containers will be described.

The first storage container 5a has ten first optical fiber sensors (3a, 3a,...) Connected in series to ten optical fiber cables 2a, 2b,. 3a) is stored and the second
Similarly, the tenth container 5b has the tenth container 5b belonging to the second container.
The three optical fiber sensors (3b, 3b,..., 3b) are housed, and the tenth storage container 5j also includes ten optical fiber sensors (3j, 3j,. 3j) is stored.
Therefore, each of the storage containers 5a to 5j has ten optical fiber sensors 3a of the optical fiber cables 2a, 2b,.
.. 3j are stored in units of ten. Note that the method shown in FIG. 3 employs the same measurement method as that shown in FIG. 1, and therefore, description thereof will be omitted to avoid redundant description of its operation.

As shown in FIG. 3, a continuous waveform signal having the same carrier wavelength, that is, the same frequency, is intermittently used as the light source light.
Each optical fiber sensor group (3a, 3a,... 3)
a), (3b, 3b,... 3b),.
3j,... 3j) incident ends 41a, 41b,.
1j is simultaneously incident on the light to detect it. FIG. 4A shows an example in which, when the incident light is detected and the backscattered light is detected, the accuracy and reliability of the detection value for each optical fiber sensor group described above are determined. The data processing apparatus will be described with reference to a functional block diagram and a flowchart for executing the control shown in FIG.

FIG. 4A has a keyboard, CRT, printer, etc. (not shown) as input / output devices.
FIG. 4 is a functional block diagram of an ordinary microcomputer or a personal computer having a memory and executing a data processing control program described below. As shown in FIG. 4B, detectors 8a, 8b,. 5j, the optical fiber sensors (3a, 3a,... 3a) for each of the storage containers 5a, 5b,.
.. 3b) and... (3j, 3j,... 3j) are collectively stored in memory for each storage container, and then stored in a memory for each storage container. From the pressure detection signal of the optical fiber sensor
.. J are calculated for each storage container (step S1), and a total pressure value for each storage container is obtained by statistical processing (step S2). The value and the standard deviation are output to a printer or the like, and the accuracy and reliability of the detection value for each optical fiber sensor group are determined.

In the apparatus shown in FIG.
Light with different carrier wavelengths is incident, and measurement accuracy and
It is possible to evaluate the secular change of the pressure dependency of the used fiber wire and the like. In this case, the incident ends 41a, 41
When light having different carrier wavelengths is simultaneously incident on each of b,... 41j, the ten optical fiber sensors (3a, 3a,.
4), the backscattered light having different carrier wavelengths is input to the data processor shown in FIG. 4A, and the pressure dependence of the backscattered light intensity of each optical fiber sensor (3a, 3a... 3a) is determined. Perform a mutual check to compare each other. Such a mutual check method is applied to an optical fiber sensor (3b, 3b).
b, 3b),..., optical fiber sensors (3
j, 3j... 3j) and make a comparison, and perform statistical processing to evaluate the reliability and the like of the pressure detection data.

In this case, especially when the optical fiber used has a different pressure dependency depending on the carrier wavelength, light having a different carrier wavelength is transmitted to each fiber cable 2a, 2a, 2b, 2c.
b,... 2n, each optical fiber sensor (3
a, 3a,... 3a) and (3b, 3b,.
b),..., (3n, 3n,... 3n), so that S is further increased than when the same carrier wavelength is used.
It can be expected that the N ratio will be improved.

Next, a third embodiment of the present invention will be described in detail with reference to FIG. FIG. 5 shows a configuration diagram of a pressure sensor that measures the intensity of backscattered light of an optical fiber sensor that is connected to each of the optical fiber cables arranged in parallel and that has an end. Each of the storage containers 5a, 5b,... 5n having the same configuration as that described above is, for example, an optical fiber wound in a meandering shape or a roll shape and having ends 42a, 42b,. -The sensors 3a, 3b, ... 3n are stored one by one. These optical fiber sensors 3a, 3b,
The optical fiber cables 2a, 2b,... 2n housed in the sheathed or non-sheathed multicore cable 15 are respectively provided at the ends 5a ′, 5b ′,. Articulated and their light incident ends 41a, 41
.. 41n have Y-type optical fibers 9a, 9b,.
..9n are provided opposite to each other. This Y-type optical fiber 9
, 9n, light pulse generators 7a, 7b,... 7n and photodetectors 8a, 8b,.
8n is provided. It is needless to say that the storage containers 5a, 5b,... 5n of the present embodiment are also configured in the same manner as the storage containers shown in FIGS.

To explain the operation, the light sources 7a, 7b,
... Each pulse light of 7n is transmitted through an optical fiber cable 2.
a, 2b,... 2n incident ends 41a, 41b,.
The pulse light which is reflected at 41n and continues to travel is further provided with the optical fiber sensors 3a, 3b,.
..Introduced into 3n. And the storage containers 5a, 5b,
... Stress corresponding to the sea level fluctuation on 5n is applied to each of the optical fiber sensors 3a, 3b, ... 3n via the cover 11, and backscattered light corresponding to the stress is generated. And the detectors 8a, 8
At b,... 8n, the backscattered light intensity is detected for each installation position of the storage container.

The one shown in FIG. 5 is different from a single-core optical fiber cable in which a plurality of optical fiber sensors are connected in series, like the pressure sensor shown in FIG. In this configuration, a single optical fiber sensor is connected, and transmission light enters the single optical fiber sensor and detects backscattered light from the single optical fiber sensor. Therefore, compared to a system in which a large number of optical fiber sensors are connected in series, transmission light enters one optical fiber cable, and backscattered light is detected, for example, multiple scattered light between a plurality of optical fiber sensors is used. It is considered that the accuracy of the measured value is good because the influence of the reflected light and the multiple reflected light is small. However, the system shown in FIG. 5 is an expensive system because there are more light sources and detectors than in the case of FIG.

Also in the third embodiment, as a light source, a continuous waveform signal having the same carrier wavelength is intermittently input, or carrier lights having different carrier wavelengths are intermittently input. An improvement in the SN ratio of the measured value can be expected.

Next, a fourth embodiment of the present invention will be described in detail with reference to FIG. Figure 6 shows the optical fiber
FIG. 3 is an example of a configuration diagram of a pressure sensor that detects a pressure fluctuation due to a sea level displacement on a storage container installation position based on a detection value obtained by detecting a transmitted light intensity transmitted through a sensor at an emission end of an optical fiber.

The optical fiber cables 2a, 2b,... 2n for light guide arranged side by side are housed in the multi-core cable 21 with or without the light guide shown in FIG. Each of the cables 2a, 2b,... 2n has an optical fiber sensor 3 formed in a loop shape.
., 3n are connected in series one by one.
Then, the optical fiber sensors 3a, 3b,.
As described above, the optical fiber sensor is coated with a synthetic resin coating, and the optical fiber sensor changes its axial direction and radial direction in response to the pressure applied through the coating. Correspondingly, each of the incident ends 41a to 41n
The incident light 65 from the light source 7 that is incident on the optical fiber sensors 3a to 3n passes through the optical fiber sensors 3a to 3n and exits 41a ′ to 41a.
The transmitted light intensity 67 emitted from n ′ and detected by the photodetectors 8a to 8n fluctuates.

Further, in the example of the embodiment of detecting the transmitted light intensity shown in FIG. 6, the intensity of the forward scattered light is measured so that, for example, the fluctuation state of the sea level at the installation position of the storage container. Can, of course, be detected.

Next, a fifth embodiment of the present invention will be described in detail with reference to FIG. FIG. 7 is a configuration diagram of a pressure sensor that detects, for example, a pressure fluctuation due to a fluctuation in the sea level at the storage container installation position based on the phase displacement amount of the optical output of the optical fiber sensor.

The storage containers 71a, 7 provided in the measurement area
1b,... 71n have light sources 74a, 74b,.
Outgoing optical fiber cables 77a, 77 having a length L from the light incident end for guiding the 74n incident light to the storage container.
.. 77n and storage containers 71a, 71b.
1n closed-loop optical fiber sensor 72
, 72n, and phase comparison devices 75a, 7a
75b are connected to return optical fiber cables 77a ', 77b',... 77n 'each having a length L reaching an emission end for transmitting measurement light toward a light incidence end (not shown) of 5b,. . Also, the reference optical fiber cables 73a, 73b,... 73 for the forward path having a length L for transmitting the divided light from the light sources 74a, 74b,.
, a folded portion 70a of the optical fiber cable folded at the storage containers 71a, 71b,.
70b,... 70n, and the phase comparison device 7
75a, 75b,... 75n, return length reference optical fiber cables 73a ', 73b',.
73n 'is provided. In addition, the storage container 71a,
71n are configured in the same manner as the configuration described in the description related to FIG.
Of course, each of the four optical fiber sensors connected to each of 71b,... 71n is housed by a non-exterior or unextended cable (not shown).

The operation will be described below.
Stress fluctuations due to sea level fluctuations at the installation positions of 71b,...
.. 72n, the phase of the carrier light is displaced in accordance with the stress. This displacement light is transmitted to the phase comparators 75a, 75b,... 75n together with the reference light. In the phase comparison device that has performed the photoelectric conversion of the carrier light and the reference light, the phase difference is obtained, so that the reference optical fiber cables 73a, 73b for the forward path at the distance L can be obtained.
73n and the external stimulus exerted on the reference optical fiber cables 73a ', 73b',... 73n 'for the return path, and similarly the optical fiber cables 77a, 77b,. , And return optical fiber cables 77a ', 77b', ...
The external stimulus similarly exerted on 77n 'is canceled.

For this reason, the phase comparison devices 75a, 75b,
.. 75n, the storage containers 71a, 71b,.
The optical fiber sensors 72a, 72b,.
72n is detected only, and an accurate signal indicating only the phase difference is detected by the detectors 76a, 76b,.
76n.

The second to fifth embodiments of the present invention
In the second embodiment, similarly to the first embodiment, for example, an optical fiber roll formed by molding a cylinder or a rectangular column can be used as an optical fiber sensor. At this time, it goes without saying that the detection sensitivity of the optical fiber sensor can be increased by increasing the length of the optical fiber sensor stored in the storage container.

Next, an example in which the pressure sensors shown in the first to fifth embodiments of the present invention are laid in a measurement area will be described.
This will be described with reference to FIG. At each location on the seabed of the harbor with several docks shown in FIG. 8, there are a number of storage vessels 83 connected to fiber optic cables provided at a land station 82 connected to a central office 81 by data transmission lines.・ ・ Are arranged to construct a network for sea level displacement detection. Thus, the storage container 8 installed in a wide harbor area
By collecting detection data from the network for monitoring sea level displacement in 3 ..., it is possible to grasp in detail the sea level displacement caused by tsunamis, typhoons, typhoons, etc. on storage containers installed in large port areas. Can be done. At that time, the above-described measurement of the backscattered light intensity of the present invention, the measurement of the transmitted light intensity, the measurement of the forward scattered light intensity, or the optical fiber sensor applied to the measurement of the amount of phase displacement are stored in each storage container. By comparing the measured values with each other, it is possible to determine the accuracy and reliability of the measured values.

Of course, the application examples of the above-described first to fifth embodiments of the present invention are applicable to a water pressure gauge, a tsunami gauge, a wave gauge, and the like. Etc., or for educational purposes or at home. Further, the three water meters can be applied to the measurement of the water level of a reactor cooling water tank, the detection of the oil level of an oil tank, and the like. Each of the above-mentioned measuring instruments monitors the water level unattended, and enables measurement of a tsunami on the order of, for example, cm.

As shown in FIG. 9, the present invention is also applicable to an anemometer. That is, for example, a single optical fiber sensor 94 is provided on the bottom surface of a U-shaped tube filled with mercury 91 and having one end 90 sealed and the other end 92 open to the atmosphere.
Is arranged. Then, when the wind blows in the direction of the arrow at the open end 92, the air pressure at that portion decreases, and the liquid level rises as shown by the dotted line. The rise in the liquid level due to the rise in the liquid level can be detected as pressure fluctuation by the optical fiber sensor 94, and the signal processing of the detection signal can be performed to calculate the wind speed.

Next, FIG. 10A shows an example in which the light quantity for measurement and the light quantity of the reference light carried by the optical fiber cable and the optical fiber cable for carrying the reference light are amplified by an optical amplifier. This will be described with reference to FIG.

Referring to FIG. 10A showing an example in which an optical amplifier is provided in a stage preceding the optical fiber sensor, the weak measuring light carried by the optical fiber cable 102 and
The weak reference light carried by the reference optical fiber cable 102 is amplified by the optical amplifier 100 installed before the optical fiber sensor 105. By transmitting the optically amplified measurement light and reference light to the optical fiber sensor 105, the detection sensitivity can be improved.

Referring to FIG. 10B showing an example in which an optical amplifier is provided at the subsequent stage of the optical fiber sensor, the weak measuring light carried by the optical fiber cable 102 and the weak measuring light carried by the reference optical fiber cable 102. After obtaining a phase difference from the weak reference light, the signal is amplified by an optical amplifier 100 installed at the subsequent stage of the optical fiber sensor 105. In this case, since the input phase difference signal is weak, if it is not used in the linear portion of the input / output characteristics of the optical amplifier 100, a detection signal with reduced accuracy will be detected. Although the shape of the optical fiber sensor 105 shown in FIGS. 10A and 10B is shown in a square wave shape for convenience, it is needless to say that the optical fiber sensor 105 is formed in a roll shape or a meandering shape.

[0044]

As described above, according to the first to sixth aspects of the present invention, there is provided an optical fiber sensor having a function of varying backscattered light intensity, transmitted light intensity, or phase in accordance with applied pressure. Connected in series to the optical fiber cable for light guiding, only the optical fiber sensor is arranged in each of the storage containers arranged in the measurement area, and covered with a synthetic resin covering that is deformed by an externally applied pressure. With such a configuration, there is no need to provide a circuit device that receives power supply therein or an element such as an electronic component as in a conventional storage container, and external pressure is applied via the cover. Because it only contains fiber optic sensors, it is not necessary to make the container robust enough to withstand pressure, it is not necessary to increase the size, and it is compact. It is sufficient container of simple structure. Therefore, the production of the storage container is simplified, and the production cost can be significantly reduced.

According to the first aspect of the present invention, since at least one optical fiber sensor is connected in series to a single-core optical fiber cable, the structure of the pressure sensor is simplified and the manufacturing cost is reduced. It has the effect of doing.

Further, in the invention according to claim 4, since a single optical fiber sensor is connected in series to each of the plurality of optical fiber cables, light enters the single optical fiber sensor and is rearward. It is sufficient to detect the scattered light intensity, and compared to the case of measurement using only a single optical fiber sensor, a measurement value can be statistically obtained using a large number of pressure measurement data, so that the measurement with a good SN ratio is performed. It becomes possible.

According to the sixth aspect of the present invention, at the time of phase comparison, a measurement error due to an external stimulus generated in the optical fiber cable for light guide is transmitted to the optical fiber cable for reference light guide provided therewith. Since erasure can be performed by a measurement error based on the generated external stimulus, measurement accuracy can be improved.

According to a seventh aspect of the present invention, in the pressure sensor according to the third aspect, the carrier wavelength of the incident light of the optical fiber sensor is configured to be the same wavelength or the carrier wavelength is different, so that the measured value SN is improved. It can be expected that the ratio will be improved.

Further, the invention according to claim 8 provides the invention according to claim 4.
In the pressure sensor described above, it is expected that the carrier wavelength of the incident light of the optical fiber sensor is configured to be the same or different, and the SN ratio of the measured value can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a pressure sensor that measures the intensity of backscattered light according to a first embodiment of the present invention.

2A is a sectional side view of the storage container as viewed from section line AA in FIG. 1, FIG. 2B is a perspective view of the storage container connected to an exterior or non-exterior cable, and FIG. Optical fiber
FIG. 4 is a diagram schematically showing generation of backscattered light by connecting an optical fiber sensor to an entrance end of a cable, an open end, and an optical fiber cable.

FIG. 3 shows a second embodiment which is a modification of the first embodiment for measuring the intensity of backscattered light according to the present invention. In the pressure sensor shown in FIG. 1, a plurality of light sources are used. FIG. 4 is a configuration diagram of a pressure sensor in which a plurality of optical fiber sensors are stored in a storage container.

FIG. 4A is a functional block diagram of a data processing device that compares the detection output values of the pressure sensor shown in FIG. 3 with each other and determines whether or not the detection value is correct based on an average value and a standard deviation value; (B) is a flowchart of the data processing device.

FIG. 5 shows a third embodiment of the present invention, in which a single open-ended optical fiber sensor is housed in each of the storage containers arranged side by side in the measurement area and connected to each optical fiber cable. FIG. 3 is a configuration diagram of a pressure sensor that measures the intensity of backscattered light.

FIG. 6 shows a fourth embodiment of the present invention, and based on a detected value of transmitted light intensity of an optical fiber sensor,
It is a block diagram of the pressure sensor which detects the stress fluctuation | variation by the fluctuation | variation of the sea level at the storage container installation position.

FIG. 7 shows a fifth embodiment of the present invention, and detects a pressure fluctuation corresponding to a fluctuation in sea level at a storage container installation position based on a phase displacement amount of an optical fiber sensor. FIG.

FIG. 8 shows a storage container storing the pressure sensor of the present invention,
It is a top view showing the state where it distributed and arranged on the seabed of a harbor.

FIG. 9 is a conceptual diagram of an anemometer in which the optical fiber sensor of the present invention is installed in a U-shaped liquid level detector.

FIG. 10A is a circuit diagram of a device for providing an optical amplifier in front of an optical fiber sensor and comparing the phase between reference light and the optical fiber sensor, and FIG. 10B is a diagram illustrating an optical amplifier provided in the latter stage of the optical fiber sensor; FIG. 3 is a circuit diagram of an apparatus for performing a phase comparison between a reference light and an optical fiber sensor.

[Explanation of symbols]

1 ... Single-core armored or non-armored cable, 1A ...
Multi-core or non-core cable, 2 ... single-core or multi-core optical fiber cable, 3a, 3b, 3n ...
· Optical fiber sensors, 5a, 5b, 5n ··· storage container, 7 ··· light source, 8 ··· photodetector, 10 ··· synthetic resin substrate, 11 ··· coating body made of synthetic resin.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01L 11/00

Claims (8)

(57) [Claims] At least one optical fiber sensor having a function of varying the backscattered light intensity according to an applied pressure is connected in series to a single-core optical fiber cable for guiding light, and the optical fiber sensor is connected to the optical fiber sensor. Are stored one by one in each of the storage containers arranged in the measurement area,
A pressure sensor forming a linear multi-point observation array as a whole, wherein the storage container includes the optical fiber sensor serving as a pressure observation point on a non-metallic support, and a synthetic resin deformable by an externally applied pressure. The series-connected optical fiber sensors are individually housed in each of the containers except for the last-stage container, and the last-stage terminal is placed in the last-stage container. An optical fiber sensor comprising:
After passing through the optical fiber sensors one after another, the light is guided to the last optical fiber sensor, and each backscattered light intensity corresponding to the pressure fluctuation applied to each optical fiber sensor of the multi-point observation array is detected at the incident end. And a pressure sensor configured to detect a pressure change based on the detected value. 2. A method according to claim 1, wherein at least one optical fiber sensor having a function of varying the intensity of the backscattered light corresponding to the applied pressure is connected in series with each of the fiber lines constituting the multi-core optical fiber cable. At the same time, the pressure is set so that each optical fiber sensor connected in series for each fiber line is stored one by one in each of the storage container rows arranged in the measurement area, and a linear multipoint observation array is formed as a whole. A sensor, wherein the storage container is provided with the optical fiber sensor serving as a pressure observation point on a non-metallic support, and is covered with a synthetic resin coating that is deformed by an externally applied pressure. The optical fiber sensors connected in series for each of the fiber lines are individually stored in each of the storage containers except the last storage container in the container row, and In the storage container, the last optical fiber sensor having an end is stored, and the incident light from each input end of the multi-core optical fiber cable passes through the optical fiber sensor one after another, and the last optical fiber sensor is received. The backscattered light intensity corresponding to the pressure fluctuation applied to each optical fiber sensor of the multi-point observation array guided by the sensor is detected at the incident end, and the pressure fluctuation is detected based on the detected value. Pressure sensor characterized in that: 3. A series connection of n optical fiber sensors which are housed one by one in storage containers arranged at n positions in a measurement area and have a function of varying the backscattered light intensity in accordance with the applied pressure. Optical fiber for light guide connected
A plurality of cables are provided, and among the first to n-th optical fiber sensors connected to each of the plurality of optical fiber cables, the first optical fiber sensors are housed in the first housing. The optical fiber sensors belonging to the second are stored in the second storage container, the optical fiber sensors belonging to the third are stored in the third storage container,. The n-th optical fiber sensors having an end are housed in an n-th housing, and each of the housings includes the optical fiber sensors on a non-metallic support, and is changed by an externally applied pressure. The incident light from each incident end of each of the optical fiber cables is covered with a distorting synthetic resin covering. , One after another, is guided to the fiber optic sensor having a termination in the final stage storage container, and detects the backscattered light intensity corresponding to the pressure fluctuation applied to each fiber optic sensor at each of the incident ends. And a pressure sensor configured to detect a pressure change based on the detected value. 4. A single optical fiber sensor having a function of varying backscattered light intensity in accordance with the applied pressure and being terminated one by one in storage containers disposed in a measurement area. Optical fiber
A plurality of cables are juxtaposed, and the storage container is provided with the optical fiber
A sensor is individually provided, and the optical fiber cable is covered with a synthetic resin covering that is deformed by an externally applied pressure, and each incident end of the optical fiber cable is configured to face each light source. The incident light at the entrance end is
The light is guided to each optical fiber sensor via each optical fiber cable, and at each of the incident ends, the backscattered light intensity of each optical fiber sensor that fluctuates in response to the pressure fluctuation applied to each of the storage containers is measured. A pressure sensor, which detects and detects a pressure fluctuation based on the detected value. 5. A light guide in which a single optical fiber sensor is housed one by one in a storage container arranged in a measurement area, and has a function of changing a transmitted light intensity according to an applied pressure in series. A plurality of optical fiber cables are arranged side by side, and the storage container houses the optical fiber sensor and is covered with a synthetic resin covering that is deformed by an externally applied pressure, and the light incident on the light source is provided. Each of the outgoing optical fiber cables having an end is connected to one end of the optical fiber sensor in each of the storage containers, and the respective light emitting portions of the return optical fiber cable connected to the other end of the optical fiber sensor. Is configured to face the photodetector, and the pressure applied to the container via the cover is bent in accordance with the pressure. A pressure sensor for detecting based on a detected value of transmitted light intensity from the optical fiber sensor. 6. A single optical fiber sensor having a function of displacing the phase according to the applied pressure is connected in series to the optical fiber cable for guiding light, and the optical fiber sensors are connected at multiple points in the measurement area. A pressure sensor of a type that is stored one by one in a storage container provided, wherein the storage container includes a non-metallic support and the optical fiber
A forward light guide having a length of L from the light incident end facing the light source to the storage container at one end of the optical fiber sensor, the sensor being covered with a synthetic resin covering that is deformed by an externally applied pressure; The end of the optical fiber cable for returning light guide of the same length L from the storage container to the light emitting end facing the phase comparison device is connected to the other end of the optical fiber sensor at the other end of the optical fiber sensor. Each end of the folded portion of the optical fiber cable for reference light guide provided in the storage container is connected to an optical fiber for a reference light outward path having a length L from the light incident end facing the light source to the storage container. The end of the cable and the end of an optical fiber cable for the reference optical return path having the same length L from the storage container to the light emitting end facing the phase comparison device. The phase displacement light from the optical fiber sensor and the reference light from the optical fiber cable for the reference light return path are compared in phase by a phase comparison device, so that the optical fiber cable for the light guide is formed. The measurement error based on the external stimulus generated is eliminated by the measurement error based on the external stimulus generated in the optical fiber cable for reference light guiding, and the phase displacement light of only the optical fiber sensor in the storage container is detected. Pressure sensor. 7. The pressure sensor according to claim 3, wherein the carrier wavelengths of the plurality of light sources are the same carrier wavelength or different carrier wavelengths. 8. The pressure sensor according to claim 4, wherein the carrier wavelengths of the light sources are the same carrier wavelength or different carrier wavelengths.