JPH11248581A - Water pressure sensor using optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water pressure sensor which is provided with an optical fiber grating and measures and monitors the surface level of water by converting the fluctuation of the surface level into the fluctuation of the oscillation wavelength of laser exciting light. SOLUTION: An optical fiber grating 8 is incorporated in a container 7 composed of a soft thin film bag-like body, etc., and, at the same time, the container 7 is filled up with a sufficient amount of viscous liquid 9 so that a water pressure may be applied perpendicularly to the outer peripheral surface of the grating 8. The surface level of water is detected by measuring the oscillation wavelength of laser exiting light by increasing the pitch of the diffraction grating of the grating 8 in such a way that the grating 8 is elongated in the length direction by contracting the diameter of the grating 8 by impressing hydrostatic pressure upon the outer peripheral surface of the grating 8 by applying a water pressure to the container 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water pressure sensor using an optical fiber for measuring a wavelength of an oscillation frequency of a laser beam converted according to a water pressure applied to an optical fiber grating, and detecting a water level or a water level. About.

[0002]

2. Description of the Related Art A cable-type measuring device laid in a trench or the like for observing a change in water level due to a tsunami or sea level rise as a change in bottom pressure includes a pressure-sensitive quartz that is sensitive to seawater pressure. A sensor is provided in which the vibrator 45 and the temperature-compensating crystal vibrator 46 of the vibrator 45 constitute one set. Such an apparatus will be described with reference to FIG. Cable type measuring device 40 installed on the seabed 50
Is a plurality of openings 43 through which seawater 49 flows freely.
A casing 41 having a hole is provided, inside which a pressure-resistant container main body 42 is installed.

[0003] The casing 4 into which seawater 49 flows freely.
1, a pressure-sensitive quartz oscillator 45 for applying the pressure of seawater 49 via, for example, a bellows 44 is provided.
In order to exist in the same temperature atmosphere as the vibrator 45,
A temperature-compensating crystal oscillator 46 is housed in a case 47 provided in a temperature-compensating sensor housing pressure-resistant container 42A having a shape protruding from the pressure-resistant container main body 42 near the oscillator 45. Reference numeral 53 in the figure denotes a partition wall for separating the pressure-resistant container 42A from the pressure-resistant container main body 42, and 57 denotes an optical fiber cable having an optical fiber 56 for transmitting a measurement signal and an optical fiber 58 for transmitting a control signal, and a power line. A power supply / optical signal transmission cable comprising a cable 59 is shown, 60 is a watertight packing having a pressure resistance, 60A is a watertight packing having no pressure resistance, and 65 is an outer peripheral surface of a cylindrical body. A pressure receiving body partially provided with a pressure-sensitive membrane (not shown) is shown.

A pressure-sensitive oscillation circuit formed by a pressure-sensitive quartz oscillator 45 to which the pressure of seawater 49 is applied via a pressure receiving body 65 and an oscillator 51 has an oscillation frequency f corresponding to the applied water pressure.
Outputs 1. An oscillation circuit for temperature compensation formed by the crystal oscillator 46 for temperature compensation to which a constant pressure is applied in the case 47 and the oscillator 52 corresponds to a constant pressure at substantially the same temperature. An oscillating frequency f2 is output, and these oscillating frequencies f1 and f2 are output to the encoder 54 in the next stage.
, Respectively, and this is input to an electric / optical signal converter 55 such as a light emitting diode, for example, and converted into an optical measurement signal, and transmitted to a land station (not shown) via an optical fiber 56 for transmitting the measurement signal. Send. On the other hand, an optical control signal input through an optical fiber 58 for transmitting a control signal is transmitted to an optical-electrical converter 63 such as a photo-transistor via an optical coupler 62, and is converted into an electric signal and the hydraulic pressure is converted. A control signal is supplied to a circuit device of the measurement system. In addition, the DC power input via the power line cable 59 is input to the power supply unit 61, and the power is supplied to the circuit device of the water pressure measurement system as energizing power.

According to the above-described measuring apparatus, the frequencies f1 and f2 of the two oscillation circuits are detected independently of each other. The data is corrected in the station or the like by the oscillation frequency f2 of the temperature-compensating crystal oscillator 46, which is affected by the same temperature fluctuation, so that the temperature-compensated water pressure can be obtained.

[0006] On the other hand, in the technical fields of optical communication and optical information systems, while focusing on the development of optical fiber couplers that execute wavelength selection and branching of optical signals, erbium-doped optical fibers. Attention has been focused on the application of fiber gratings written in.

[0007] An optical fiber grating is formed by forming a Bragg diffraction grating in the core of an optical fiber, and can be used as a reflection filter that reflects only light of a specific wavelength, and also as a wavelength control element, a sensor element, and a dispersion compensation element. Is also widely used.

[0008] The method of forming an optical fiber grating as described above, will be described as an example the two-beam interference method, as shown in FIG. 11 (B), wavelength lambda _UV optical fiber 73
Irradiation of the ultraviolet light 80, 81 at two angles of incidence α from two directions causes a periodic change in the refractive index in the longitudinal direction of a core (not shown) of the optical fiber 73 due to light interference, and a diffraction grating is formed. A grating 75 is formed. When light is irradiated on the optical fiber grating 75, diffracted light is emitted. Here, assuming that the refractive index of the core is n1, the reflection wavelength λ _B of this diffraction grating is λ _B
= Λ indicated by the _UV · n1 / _sinα.

An optical fiber whose oscillation wavelength is variable by tension constituted by the optical fiber grating described above.
The laser device is described with reference to FIG. The excitation light having a wavelength of 1.48 μm from the laser light source 70 is made incident on the isolator 71 via the optical fiber 73, the return of the reflected light is prevented by the isolator 71, the laser light becomes one-way laser light, passes through the optical coupler 72,
The light enters the tension monitor 76 connected to one end of the reference numeral 9.
Further, a reflection plate 74 on which gold is vapor-deposited passes through a fine movement mechanism 77 which is connected to the other end of the CPU 79 through an optical fiber grating 75 and is controlled by the CPU 79 to apply a gradually increasing tension to the optical fiber grating 75. To the data processing device (not shown) via the optical coupler 72 and the optical fiber 80.

Incidentally, the pitch of the diffraction grating of the optical fiber grating 75 increases in response to the sequentially increasing tension applied by the fine movement mechanism 77, and the oscillation wavelength nm increases accordingly. For example, as shown in FIG. 11 (C), when the tension is sequentially increased from 0 to 2500 g, the fluctuation tendency becomes approximately 1552 nm to 1583 nm.
(“Optical fiber and fiber type device”, Kawakami, Shiraishi, Ohashi, Baifukan,
Published July 10, 1996, pp. 189-196).

[0011]

By the way, even if an oscillation circuit for temperature compensation is provided, in order to obtain an accurate measurement result, the quartz oscillators 45 and 46 are kept at the same temperature with respect to a change in external temperature. Ideally, it would be in the affected location,
A quartz oscillator 45 exposed to seawater and a pressure-resistant container 42A
In consideration of the fact that the installation environment with the crystal unit 46 housed in the case 47 is not the same, a liquid 48 having a large heat capacity, for example, called polybutene, is replaced with a pressure-sensitive crystal unit 45.
And a pressure-resistant container 4 containing a crystal resonator 46 for temperature compensation
2A is filled in a pressure receiving body 65 surrounding the pressure receiving body 65. As described above, since the quartz oscillator 45 itself having a function of generating electric charge by applying a water pressure is immersed in the polybutene liquid 48, there is a problem that a countermeasure against electric leakage must be taken. For this reason, an additional mechanism such as covering a plurality of layers of the surfaces of both the crystal units 45 that are in contact with the liquid, the electrode unit, the unit for supporting the unit, and the like with an insulating material such as silicon oil having electrical insulation, and the like. Since an additional circuit such as a "leakage protection circuit" for protecting the voltage oscillation circuit from "leakage" is required, there is a problem that these parts are additionally required and the cost is inevitably increased.

An apparatus for converting tension into an oscillation wavelength using an optical fiber grating is known.
At present, a device for installing an optical fiber grating on the bottom of the sea, such as the bottom of a lake or a lake, and monitoring the fluctuation state of the water surface level has not yet been developed.

Accordingly, an object of the present invention is to provide an optical fiber grating on the seabed or the bottom of a lake without using a crystal oscillator oscillating circuit in which a water level sensor is provided with electrical insulation. It is an object of the present invention to provide a completely new water pressure sensor using an optical fiber, which can measure the fluctuation state of the water level and the water level.

[0014]

According to a first aspect of the present invention, there is provided a water pressure sensor comprising a laser light generation / wavelength measurement unit provided on one half of a casing, and a hole for water inflow and outflow on an outer peripheral surface.
A water pressure sensor provided in the other half of the casing and including a measurement system including a water pressure / oscillation wavelength conversion unit having a built-in optical fiber grating, wherein the laser light generation / wavelength measurement unit includes a laser light source. The laser pumping light is transmitted through the optical fiber to the water pressure / oscillation wavelength conversion unit, and the water pressure / pressure converted according to the water surface level, which is reflected and sent from the water pressure / oscillation wavelength conversion unit side. The wavelength of the oscillation wavelength conversion signal is measured, and the obtained oscillation wavelength measurement signal is configured to be transmitted to a land station via a transmission cable for transmission, and the water pressure / oscillation wavelength conversion unit is formed of a flexible thin film bag or the like. Filled with a sufficient amount of viscous liquid so that it can be applied and applied from the outer peripheral surface to the outer peripheral surface of the optical fiber grating as a hydrostatic pressure. A pressure-sensitive optical fiber grating unit having a built-in optical fiber grating for converting the oscillation wavelength of the laser excitation light incident from the laser light generation / wavelength measurement unit in accordance with the applied water pressure. With this configuration, the water pressure corresponding to the water surface level is converted into a hydrostatic pressure through the viscous liquid-containing container, applied to the optical fiber grating, converted according to the water pressure, and the measured oscillation wavelength of the laser excitation light is measured. It is characterized by transmitting a signal.

According to a second aspect of the present invention, there is provided a laser light generation / wavelength measuring unit provided on a pressure-resistant container attached to one half of a casing, and a hole for water inflow and outflow on an outer peripheral surface, which is provided on the other half of the casing. A water pressure sensor having a measurement system comprising a water pressure / oscillation wavelength conversion unit having a built-in optical fiber grating, wherein the laser light generation / wavelength measurement unit transmits laser excitation light of a laser light source via an optical fiber. A first optical coupler for transmitting light toward the water pressure / oscillation wavelength converter and separating and extracting a water pressure / oscillation wavelength conversion signal reflected and sent from the water pressure / oscillation wavelength converter; A wavelength measuring device for measuring and encoding the wavelength of the hydraulic pressure / oscillation wavelength conversion signal separated from the first optical coupler, and an oscillation wavelength measurement signal from the wavelength measuring device. And a second optical coupler to be superimposed on a carrier wave of the transmission cable for transmitting terrestrial station, the water pressure -
The oscillation wavelength conversion unit is formed of a flexible thin film bag or the like, and has a sufficient amount of water pressure applied from the outer peripheral surface thereof so as to be applied as a hydrostatic pressure to the outer peripheral surface of the optical fiber grating. In a container filled with viscous liquid,
By providing a pressure-sensitive optical fiber grating portion having an optical fiber grating with one end connected to the first optical coupler and the other end written in an optical fiber connected to the light reflecting member, A water pressure corresponding to the water surface level is applied to the optical fiber grating as a hydrostatic pressure via the viscous liquid-containing container, and the oscillation wavelength measurement signal of the laser excitation light converted and measured according to the water pressure is transmitted to the land station. Transmission is performed via a transmission cable for transmission.

According to a third aspect of the present invention, the water pressure sensor is disposed at a plurality of water floors in a measurement water area, and the transmission pressure cable is transmitted from the water pressure sensor to the land station transmission cable. By superposing and transmitting the respective oscillation wavelength measurement signals, a measurement network for monitoring the fluctuation state of the water surface level is formed in the measurement water area.

According to a fourth aspect of the present invention, a plurality of measurement systems each including the laser beam generation / wavelength measurement unit and the water pressure / oscillation wavelength conversion unit are provided in the water pressure sensor. It is characterized in that it is installed.

The invention according to claim 5, which is dependent on claim 1 or 2, is characterized in that the optical fiber grating for pressure sensing in the water pressure / oscillation wavelength converter is, for example, an optical fiber in a pressure vessel filled with an inert gas. Along with accommodating the grating, an ambient temperature compensating optical fiber grating section that converts only the fluctuation of the ambient temperature into the fluctuation of the oscillation wavelength is provided in parallel, and a backup laser light source is provided in parallel with the laser light source, and Excitation light is split into two by a shunt optical coupler, and one of the laser lights is applied to the pressure-sensitive optical fiber grating section,
A light transmitting optical path system for transmitting the other laser light to the ambient temperature compensating optical fiber grating section, and a water pressure / pressure transmitted from the pressure sensitive optical fiber grating section.
The wavelength of the oscillation wavelength conversion signal and the ambient temperature / oscillation wavelength conversion signal sent from the optical fiber grating for ambient temperature compensation are measured by a wavelength measuring instrument, and the obtained oscillation wavelength measurement signals are transmitted to the transmission cable. When the laser light source is turned off, an optical path connecting the laser light source and the light transmitting optical path system is formed, and the backup laser light source ignited by a control signal and the light transmitting optical path system are formed. Characterized in that it is provided with an optical path switching means for switching to an optical path connecting.

The invention according to claim 6 is dependent on claim 5, wherein the N backup laser light sources are arranged in parallel with the laser light source, and the N backup laser light sources are supplied with a control signal. Each time, the ignition signal multi-path switching means for sequentially energizing and igniting, and, when the laser light source is turned off, an optical path connecting the laser light source and the light transmitting optical path system, the backup laser sequentially ignited. An optical path switching means for switching to an optical path connecting the light source and the light transmission optical path system is provided.

[0020] The invention according to claim 7 which depends on claim 1 or 2, wherein the water pressure sensor is installed at the bottom of the water, and
The underwater acoustic wave caused by a natural earthquake or an artificial earthquake is measured by using the optical fiber grating for pressure sensing in the oscillation wavelength conversion unit as an underwater acoustic wave reception sensor.

The invention according to claim 8 is dependent on claim 5, wherein the water pressure sensor is installed at the bottom of the water, and the optical fiber grating for compensating the ambient temperature in the water pressure / oscillation wavelength converter is for detecting the temperature of the underwater near the water bottom. It is characterized in that ambient temperature data near the installation water bottom is collected by using as the temperature sensor.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the measurement principle of a water pressure sensor according to the present invention will be described with reference to FIG. FIG. 1A shows a laser light generation / wavelength measurement unit 201 and a water pressure / oscillation wavelength conversion unit 20.
FIG. 1B is a block diagram of a water pressure sensor 1 of the present invention including a measurement system including a laser beam generation / wavelength measurement unit 201 cut along a dotted line AA in FIG. FIG. 7C is an example of a graph showing a fluctuation relationship between the depth m of fresh water and the oscillation wavelength nm of the optical fiber grating. Here, FIG. 1C shows that, as a material of the optical fiber grating portion, for example, the axial elongation due to the hydrostatic pressure applied from the outside is one-to-one with the elongation due to the axial tension having the same magnitude as the external hydrostatic pressure. 7 is a graph in the case of using the one having the characteristic corresponding to.

As shown in FIG. 1A, a laser light generating / wavelength measuring unit 201 provided on one half of a casing 2 of a water pressure sensor 1 installed on the water bottom includes a laser light source 12 for exciting and emitting laser light. An isolator 13 for preventing the reflected light from being emitted from the side from which the light is emitted, and placing the laser light from the laser light source 12 on the optical fiber 10 and emitting the laser light;
The outgoing light from the isolator 13 is transmitted toward the water pressure / oscillation wavelength converter 202, and is reflected by the gold vapor deposition reflector 11 provided on the water pressure / oscillation wavelength converter 202 side. An optical coupler 14 that separates the hydraulic pressure / oscillation wavelength conversion signal transmitted through the conversion unit 202 and returned to the optical fiber cable 15 is provided.

On the other hand, the water pressure / oscillation wavelength converter 202 is provided in the other half of the casing 2 in which a plurality of holes 3... It has an optical fiber grating for pressure sensing. That is, a viscous liquid 9 such as silicone oil is filled in a container 7 formed in a cylindrical bag shape with a flexible thin film made of a material such as a thin vinyl film.
Even if water pressure is applied in the direction of arrow S from the outer peripheral surface side of
A sufficient amount is filled so that an applied water pressure, that is, a hydrostatic pressure can be applied only in a direction perpendicular to the outer peripheral surface of the built-in optical fiber grating 8. For this reason, no pressure is applied in the direction along the surface of the optical fiber grating 8 in the longitudinal direction, that is, the hydrostatic pressure is applied without applying dynamic pressure, and all the applied water pressure is reduced. Is applied in a direction perpendicular to the outer peripheral surface of the optical fiber grating 8 (in the direction of arrow T), whereby the diameter of the optical fiber grating 8 is contracted, and the optical fiber grating 8 is elongated in the longitudinal direction, so that the pitch of the diffraction grating is elongated. As described above, since all of the applied water pressure is used to extend the pitch of the diffraction grating, the measurement resolution is improved, and an accurate measurement result can be obtained.

In the apparatus configured as described above, when the water surface level fluctuates, the fluctuating pressure S of the water flowing in and out through the hole 3 is applied to the outer peripheral surface of the container 7 exposed to the water. Then, a hydrostatic pressure is applied to the outer peripheral surface of the optical fiber grating 8 from the vertical direction as shown by the arrow S, whereby the diameter of the optical fiber grating 8 contracts, but expands in the longitudinal direction thereof. Accordingly, the pitch of the diffraction grating is increased, and the oscillation wavelength of the laser light is correspondingly increased. As a result, a hydraulic pressure / oscillation wavelength conversion signal having a wavelength corresponding to the applied hydrostatic pressure is output. The oscillation wavelength measurement signal measured by the measuring instrument is transmitted.

Here, referring again to FIG. 11C described above, the relationship between the tension and the oscillation wavelength changes linearly. When the tension is 0 g, the oscillation wavelength becomes, for example, approximately 15
It is 1577 nm at 52 nm and 2000 g.
Calculating and observing the linear gradient a, a = (1577-1552) / (2000-0) = 25
/2000=1.3×10 ⁻² (nm / g). By the way, in fresh water, a change in water depth per unit area of 1 cm is equal to a unit volume weight per square cube of 1 cm ^3.
corresponding to g.

Therefore, as described above, the optical fiber
As a material of the grating portion, for example, when using a material having a characteristic in which the axial elongation due to the hydrostatic pressure applied from the outside corresponds one-to-one with the elongation due to the axial tension having the same magnitude as the external hydrostatic pressure, For example, the above 1.3
The dimension of the oscillation wavelength nm per 1 g of × 10 ^-2 (nm / g) is 1.3 × 10 ^-2 (nm / cm) = 1.
3 (nm / m), and the relationship of the oscillation wavelength per 1 m of water depth is correlated. As a result, FIG.
Can be converted to a water depth of 0 to 25 m, and the oscillation wavelength nm varies according to the water depth. When this relationship is satisfied as an optical fiber grating member, as shown in FIG. 1 (C), the oscillation wavelength varies from 1552 to 1585 nm in response to a water depth variation of about 0 to 30 m. It can be used to detect a change in water pressure, that is, a change in water level.

Then, the optical fiber grating 8
Is a material that can withstand the hydrostatic pressure at a water depth of 6000 m class, for example, and the relationship between the static water applied to the optical fiber grating 8 and the oscillation wavelength is obtained in the same manner as in FIG. For example, it can be used for measuring water pressure up to a depth of 6000 m.

In the case of seawater, since the salt and the like are dissolved, the volume of a cube of 1 g of seawater is smaller than the volume of 1 cm ³ of a cube of 1 g of fresh water. In order for the apparatus to correctly indicate the water depth corresponding to the oscillation wavelength, it is a matter of course that the water surface level is obtained by multiplying the correction coefficient calculated so as to reduce the measured wavelength value.

Next, the first embodiment embodying the principle of the present invention will be described with reference to the attached block diagram shown in FIG. 2 and the sensor casing shown in FIG. This will be described with reference to the perspective view. A water pressure sensor 1 is provided on a water bottom 21 of a water surface 20 such as a sea or a lake. The water pressure sensor 1 is provided on a laser light generation / wavelength measurement unit 201 provided on one half of a casing 2 and on the other half. Water pressure with built-in optical fiber grating 8
A measurement system including the oscillation wavelength converter 202 is provided.

A laser light generation / wavelength measuring unit 20 disposed in a cylindrical pressure-resistant container 4 fixed to one half of the casing 2
1 is a laser light source 12 for exciting and oscillating laser light, an optical isolator 13 for transmitting the emitted laser light via an optical fiber 10, and a water pressure / oscillation wavelength converter 20.
The optical coupler 14 receives and separates the converted hydraulic pressure / oscillation wavelength signal having a wavelength corresponding to the applied hydraulic pressure, which is transmitted from the optical fiber 2, and transmits the converted signal to the optical fiber 15; A wavelength measuring device 16 for measuring and encoding the wavelength of the hydraulic pressure / oscillation wavelength conversion signal,
An optical coupler 17 for superimposing the encoded oscillation wavelength measurement signal on the laser light carrier of the power supply / optical signal transmission cable 18
A gold vapor-deposited reflecting plate 11 which is fixed in the pressure vessel 2 and reflects the water pressure / oscillation wavelength conversion signal sent from the optical fiber grating 8, passes through the optical fiber grating 8 again, and sends it back to the optical coupler 14. And

In the other half of the casing 2 provided with a plurality of water inflow / outflow holes 3... On the outer peripheral surface, a water pressure / oscillation wavelength conversion section 202 having a pressure-sensitive optical fiber grating section is provided. Reference numeral 202 denotes an optical fiber grating 8 connected to the optical fiber 10 drawn out of the optical coupler 14 in the pressure container 4. And this optical fiber grating 8
A viscous liquid 9 such as silicone oil is applied to the inside of the optical fiber grating 8 by applying a water pressure applied from the outside to the outer peripheral surface of the optical fiber grating 8. It is contained in a cylindrical bag-shaped container 7 filled with a sufficient amount to be applied as a hydrostatic pressure. The other end of the optical fiber 10 pulled out from the tip of the container 7 is connected to the pressure-resistant container 4.
It is connected to a gold vapor deposition reflection plate 11 provided therein. Then, a container 7 containing a viscous liquid containing an optical fiber grating, and an optical fiber 10 connected thereto.
Is surrounded by a protective cylinder 5 having a plurality of water outflow / inlet holes 6.

Reference numeral 18 in the drawing denotes a power cable for supplying power from a land station (not shown) to electronic components for exciting the optical elements of the water pressure sensor 1, and a laser beam generation / wavelength measurement unit transmitted from the land station. a control signal cable for transmitting a control signal of the installation equipment in the 201, each of the oscillation wavelength measurement signals measured by each pressure sensor, for example, placed on a carrier frequency F _1, F ₂ ··· F _N transmission A power supply / optical signal transmission cable comprising an optical fiber cable for frequency division multiplexing communication, and 19 denotes a watertight sealing packing portion for preventing water from entering the pressure-resistant container 4.

The operation of the thus constructed water pressure sensor 1 will be described. The wavelength λ excited and emitted from the laser light source 12
Is transmitted to the optical isolator 13 through the optical fiber 10, where the reflected laser light is blocked from entering the reflected light from the optical coupler 14 and the like, and is transmitted toward the optical coupler 14. The laser light from the optical coupler 14 is supplied to a water pressure / oscillation wavelength converter 20.
2 is incident on the optical fiber grating 8. An optical fiber grating 8 is built-in, and an opening 3 of the casing 2 is provided on the outer peripheral surface of the container 7 in which the viscous liquid 9 is filled.
Are applied by the water 22 flowing through the holes 6. Further, since the water pressure is applied only from the vertical direction to the outer peripheral surface of the optical fiber grating 8 via the viscous liquid 9, the viscous liquid 9 does not flow, that is, the dynamic pressure is applied in the direction along the outer peripheral surface of the optical fiber grating 8. Is applied, the hydrostatic pressure is applied to the optical fiber grating 8. Therefore, all of the applied water pressure is applied in the radial direction of the optical fiber grating 8, the diameter of the optical fiber grating 8 shrinks, and is converted into an axial expansion change of the optical fiber grating 8, which increases the pitch of the diffraction grating. Thereby, the measurement resolution is improved.

As described above, the water pressure / oscillation wavelength conversion signal obtained by converting the oscillation wavelength λ of the laser beam into the wavelength λ _i1 corresponding to the magnitude of the applied water pressure is reflected by the reflection plate 11 and returned to the optical fiber grating 8 again. Pass through and pass through the optical coupler 14, the separated signal of the wavelength λ _i1 is incident on the wavelength measuring device 16 via the optical fiber 15, where the wavelength λ _i1 is measured, and the encoded oscillation The wavelength measurement signal enters the optical coupler 17. Then, the signal sent from the optical fiber 15 to the land station (not shown) by the power supply / optical signal transmission cable 18 is placed on, for example, a carrier wave of the frequency FK, and then sent to the land station (not shown) via the water pressure sensor 1 at the next stage. Transmit.

It is to be noted that, in place of the above-described configuration in which the reflecting mirror 11 is provided, a configuration in which a reflecting mirror is attached to the laser light emitting end of the optical fiber 10 is optional. Further, instead of measuring the wavelength, the water surface level can be detected by measuring the frequency spectrum. Then, the above-mentioned water pressure sensor can be installed on the bottom of the water, and its pressure-sensitive optical fiber grating can be used for collecting long-period underwater acoustic data based on seismic motion. For example, at least, since the water pressure fluctuation due to the propagation of underwater sound waves having a long period of about several hundred seconds to several Hz can be measured, the water pressure fluctuations of long-period sound waves based on a large earthquake that occurred near or far away can be measured. It can also be used as a "hydrophone" or "underwater microphone" for detection, or as a "sound pressure sensor" for receiving underwater sound waves, and the detected underwater acoustic data can be used for observation of natural earthquakes or artificial earthquakes. I can do it.

Next, as a second embodiment, when the life of the laser light source 12 for initial operation has expired, the backup laser light source 12A arranged in parallel is turned on, and a water pressure / oscillation wavelength converter 202 is provided. An invention in which an optical fiber grating section 02 for compensating for ambient temperature is provided in parallel with a pressure-sensitive optical fiber grating section 01 for detecting water pressure will be described with reference to FIGS. FIG. 4 is a configuration diagram of the water pressure sensor 1 from which the casing 2 is removed, and FIG. 5 is a perspective view thereof. The same members as those described with reference to FIG. 2 are denoted by the same reference numerals, and newly installed members are denoted by different reference numerals. In FIG. 4, in order to be affected by the same temperature as the external temperature received by the pressure-sensitive optical fiber grating unit 01, the optical fiber grating unit 8 is provided in parallel with the optical fiber grating unit 01.
A description will be given of the optical fiber grating unit 02 for ambient temperature compensation in which A expands and contracts only in response to a change in the ambient temperature, and the oscillation wavelength changes in response to this. The ambient temperature compensating optical fiber grating section 02 is formed to have the same shape as the pressure-sensitive optical fiber grating section 01 for the purpose of improving the reliability of the pressure data measured by the pressure-sensitive optical fiber grating section 01. The optical fiber grating 8 is placed in a pressure-resistant container 7A filled with 9A, such as an inert gas, so as to be affected by the same temperature and enhance corrosion resistance.
A is stored. In the optical fiber grating section 02 for ambient temperature compensation, holes 6
It is, of course, possible to omit the installation of the protection cylinder 5 in which.

Next, the backup laser light source 12A will be described. In a data processing device of a land station (not shown), different carrier frequencies F ₁ , F ₂ ,. · monitoring the presence or absence of the wavelength measurement signals transmitted by F _N. Then, for example, when the wavelength measurement signal from the water pressure sensor that transmits the wavelength measurement signal of the carrier frequency FK is not detected, it is determined that the life of the laser light source 12 for the initial operation of the water pressure sensor has expired, and Laser light source 12
A control signal V on the carrier frequency F _K for igniting A is transmitted via the power supply / optical signal transmission cable 18. The water pressure sensor having a filter (not shown) to pass the carrier frequency F _K, the control signal V of frequency F _K
Take in. When the backup laser light source 12A is ignited by the application of the signal V, the optical path switching optical coupler 14A causes the optical path (optical fiber 10) connecting the initially operating laser light source 12 and the optical isolator 13A to transmit light. An optical path (optical fiber 10A) connecting the backup laser light source 12A and the optical isolator 13A.
Is switched to.

The operation of the thus constructed water pressure sensor will be described. First, the life of the laser light source 12 is exhausted, the optical fiber grating portion 01 of the pressure sensing, because the laser beam is no longer sending to an optical fiber grating portion 02 for temperature compensation, for example, an oscillation having a carrier frequency F _K Power supply / optical signal transmission cable 1 for wavelength measurement signal
8 and no longer transmitted to the land station.

[0040] When the land station detects the disruption of the reception of the oscillation wavelength measurement signal of the carrier frequency F _K, the control signal V of the carrier frequency F _K to ignite the laser light source 12A for backup
And then transmitted on the feed-optical signal transmission cable 18, the water pressure sensor 1 having a filter which passes the carrier frequency F _K takes in this ignites the laser light source 12A.
The laser light source 1 is connected by the connecting optical coupler 14A.
The connection between the optical fiber 10 connected to the light transmitting side of the optical fiber 2 and the optical fiber 10 connected to the light receiving side of the optical isolator 13 is changed to the optical fiber 10A connected to the backup laser light source 12A and the optical fiber connected to the light receiving side of the optical isolator 13. Switch to connection with 10.

Thus, the backup laser light source 1
The laser light of 2A is transmitted to the optical path shunting optical coupler 14B via the optical isolator 13, where the laser light is shunted to two optical paths, one of which is sensed via the optical coupler 14 and the optical fiber 10. The light is transmitted to the pressure optical fiber grating section 01, and the other side is transmitted through the optical coupler 14C and the optical fiber 10A to the temperature compensating optical fiber.
Light is transmitted to the grating unit 02.

Optical fiber grating for pressure sensing 0
The water pressure / oscillation wavelength conversion signal detected at 1 is input to the wavelength measuring device 16 via the optical coupler 14 and the optical fiber 15, and the oscillation wavelength measurement signal λ ₁ measured and sign-converted by the optical measuring device is converted into an optical coupler for synthesis. Light is transmitted to 17. In the optical fiber grating section 02 for temperature compensation,
When the pressure-sensitive optical fiber grating unit 01 receives the same water pressure / oscillation wavelength conversion signal that shows only the same fluctuation of the ambient temperature, it obtains the converted signal by the optical coupler 14C and the optical fiber 1
5A is input to a wavelength measuring device 16A, and an oscillation wavelength measurement signal λ ₂ indicating an oscillation wavelength change based on expansion and contraction of the temperature compensating optical fiber grating 8 due to temperature fluctuation is transmitted to the optical coupler 17. Then, the oscillation wavelength is transmitted to the data processing device of the land station via the power supply / optical signal transmission cable 18 and detected by the optical fiber grating unit 01 for pressure sensing, which indicates the water surface level including the temperature fluctuation. By obtaining a difference (λ ₁ −λ ₂ ) = λ ₃ between the signal λ ₁ and the oscillation wavelength measurement signal λ ₂ indicating only the fluctuation of the ambient temperature, the pressure-sensitive measurement signal on which the fluctuation of the ambient temperature is superimposed , The ambient temperature fluctuation can be removed, and the corrected water level can be detected.

As shown in FIG. 6, a large number of backup laser light sources 12A to 12N can be arranged in parallel with the laser light source 12 provided for each water pressure sensor. In this case, each light transmitting side of the backup laser light sources 12A to 12N and the light receiving side of the optical coupler 14A are connected to the optical fiber 1
.. 10N are connected in parallel. Then, the backup laser light sources 12A to 12N
, LN, and the control signal V
A multi-way switch SW is interposed between the input side and the input side. The closing order of the switches of the multi-way switch SW is performed as follows. That is transmitted in accordance with an instruction of the control program of the data processor land station unlit discovery, for example, a control signal V placed on a carrier frequency F _K, each time to be applied to the step motor SM which is provided to the switch SW The conductive piece MP is driven in the direction of the arrow by a predetermined distance by a switch driving member attached to the drive shaft, whereby the conductive piece MP is driven by the load-side terminal P1 and the input-side terminals Q1, P2 and Q2,.・ 、
PN and QN are short-circuited in order. Thereby, the control signal V
Are sequentially applied to the conductive lines LA, LB,... LN. Thereby, for example, the applied power of the laser light sources 12A to 12N is energized, and the backup laser light source 12A is turned on.
A to 12N are ignited in sequence. Further, in addition to mechanically driving the conductive piece MP, the conductive piece MP may be configured to be electromagnetically driven by a command of a control program of the data processing device. Further, a switching transistor is connected between the load terminal P1 and the input terminal Q1, P2 and Q2,..., PN and QN, and a gate control circuit is provided instead of the step motor SM. Each time the control signal V is applied, the switching transistors may be sequentially turned on by the gate control circuit to ignite the backup laser light sources LA to LN in sequence.

The operation will be described. When the life of the operating initial drive laser light source 12 is over and the light is turned off, the control signal V transmitted from the land station that has identified this is input to the multi-way switch SW. Backup laser light source 1
2A is first ignited. The optical path from the laser light source 12 for the initial drive to the optical coupler 14A via the optical fiber 10 is switched to a new optical path for transmitting the laser light of the backup laser light source 12A to the optical coupler 14A via the optical fiber 10A. The light is transmitted to the optical isolator 13 as shown in FIG. Then, this laser light source 12
When the life of A has expired, the application of the control signal V causes the multi-way switch SW to advance one stage to transmit an ignition signal to the laser light source 12B, and the ignited laser light source 12B is connected to the optical coupler 14A. This process is repeated until the laser light source 12N is ignited, and observation for a long time is continued.

It is also possible to install the above-mentioned water pressure sensor at the bottom of the water and use the pressure-sensitive optical fiber grating unit 01 for collecting underwater acoustic data having a long cycle based on seismic motion. For example, at least a long-period water pressure fluctuation of several hundred seconds to several Hz due to the propagation of an acoustic wave can be measured, so that the water pressure due to the propagation of a long-period sound wave based on a large earthquake generated near or far away. It can also be used as a `` hydrophone '' to detect fluctuations, an `` underwater microphone '', and a `` sound pressure sensor '' to detect water pressure fluctuations due to sound waves.The detected underwater acoustic data can be used to observe natural or artificial earthquakes. Can be used. In addition, the temperature data detected by the temperature compensating optical fiber grating unit 02 is transmitted to a land station, and this data is also used for observing a temperature fluctuation tendency near the installation water bottom. Therefore, it can be used for online temperature data collection in a volcanic earthquake source, for example, a submarine volcanic zone, a crater lake, or the like.

Next, as a third embodiment, FIG. 7 shows a side-by-side type water pressure sensor having a plurality of sets, for example, three sets of measuring systems having an optical fiber grating 8 in a pressure vessel 2. This will be described with reference to the block diagram and the perspective view shown in FIG.

In the third embodiment, the measurement includes a laser light generation / wavelength measurement unit 201 provided in one half of the pressure-resistant container 4 of the casing 2 and a water pressure / oscillation wavelength conversion unit 202 provided in the other half. Systems 101, 102, 103
In order to avoid complication of the drawing, only one set of measurement systems 102 is given the same reference number as that shown in FIG.

Then, the oscillation wavelength of each water pressure / oscillation wavelength converter 202 is measured, and the oscillation wavelength measurement signal is transmitted to the land station (not shown) via the wavelength measuring devices 16, 16, 16 for encoding. The light enters the optical coupler 23 to which the optical signal transmission cable 18 is connected. Each oscillation wavelength measurement signal emitted from the optical coupler 23 is connected to the cable 18.
The measurement system 101, 102, 103 performs the same operation as that shown in FIG. 2, and the description thereof will be the same. Therefore, the reconsideration is omitted.

As described above, according to the third embodiment of the present invention in which a plurality of measurement systems of the water pressure sensor 1 having the optical fiber grating 8 are provided, one of the plurality of measurement systems fails. However, since the remaining measurement systems continue the measurement work, it is possible to continue the fluctuation analysis of the water surface level without causing a loss of the measurement data.

Further, by making the carrier wavelength of the laser light of the plural sets of measurement systems the same and performing statistical processing on each measurement data from the plural sets of measurement systems, the measurement accuracy is improved, and the SN ratio is improved. It is possible to improve the ratio.

Also in the third embodiment, FIG.
Each of the laser light sources 12, 1 provided in the measurement systems 101, 102, 103 is similar to the second embodiment of the invention shown in FIG.
At least one backup laser light source is provided side by side with respect to 2 and 12, and the optical coupler 14A is configured to have a switching capability of at least two optical paths, and provided in the measurement systems 101, 102 and 103. The optical fiber grating for temperature compensation is arranged in parallel with the optical fiber grating for pressure sensing. Thus, not only the laser light source but also the lit backup laser light source is sequentially ignited, and continuous light emission for a long period of time and correction of an error in pressure measurement data due to the influence of the ambient temperature change can be performed.

When a plurality of pressure-sensitive optical fiber grating sections are used, a plurality of temperature-compensating optical fiber grating sections may be provided.
A plurality of the temperature compensation signals may be shared by a plurality of pressure-sensitive optical fiber grating units. In addition, as described above, the pressure-sensitive optical fiber grating can be used as a sensor for detecting long-period underwater acoustic data based on a large earthquake motion generated in the near or distant place. It goes without saying that the temperature data detected by the grating unit can be used for observing the temperature fluctuation tendency of the sensor installation water bottom.

Next, an example in which the measurement systems shown in the first to third embodiments are arranged in the measurement area 30 is shown in FIG.
This will be described with reference to FIG. A relay station 32 and a data transmission line 3 are located at various places on the seabed of a port having several docks shown in FIG.
A plurality of measurement systems 1... Are arranged in a line via a power supply / optical signal transmission cable 18 provided in a land station 31 connected by 3, and a measurement network is constructed in the measurement area 30. In this way, by collecting detection data from measurement system systems installed in a wide port area, it is possible to detect sea level fluctuations of the measurement system and sea level fluctuation conditions such as tsunamis, waves, tide levels, and typhoons. Can be done. In the measurement of waves and the like, mooring is performed by a mooring device including a buoy and an anchor so that the water pressure sensor is positioned at a predetermined level below the sea surface, and the wave surface level from the sinking position of the water pressure sensor to the sea surface is measured. Of course, such a configuration may be adopted. Further, the present invention can be applied to not only the fluctuation of the sea level but also the monitoring of the water level of rivers and lakes, and the liquid level of tanks and the like.

[0054]

As described above, according to the first and second aspects of the present invention, a pressure-sensitive optical fiber grating section can be used without using a quartz oscillator type oscillation circuit requiring electrical insulation measures as a water pressure sensor. Is used to directly convert the fluctuations of the water surface level etc. into the fluctuations of the oscillation wavelength of the laser light, and measure it.Therefore, by obtaining the oscillation wavelength of the laser light generated from the optical fiber grating, the It is possible to detect a fluctuation situation.

Further, the viscous liquid is constituted by a flexible thin film bag or the like, and a sufficient amount of viscous liquid is applied so that an externally applied water pressure can be applied to the outer peripheral surface of the optical fiber grating at a hydrostatic pressure. In the filled container, since the optical fiber grating is built in, the dynamic pressure is not applied to the optical fiber grating, and all of the applied water pressure is applied as a hydrostatic pressure from the vertical direction of the outer peripheral surface, whereby The diameter of the optical fiber grating is contracted and converted into its longitudinal extension, which increases the pitch of the diffraction grating, thereby increasing the measurement resolution and allowing accurate measurement.

Further, according to the third aspect of the present invention, since the water pressure sensors are arranged on the water bottom at a plurality of locations in the measurement water area, a measurement network is formed in the measurement water area.
It is possible to monitor the fluctuation state of the water level in the water area.

According to the fourth aspect of the present invention, a plurality of measurement systems each including a laser light generation / wavelength measurement unit and a water pressure / oscillation wavelength conversion unit are arranged in parallel, so that a failure occurs. However, the remaining sound measurement system can continue the measurement work, and therefore, can continuously measure the water surface level without causing a measurement data missing period.

Further, according to the fifth aspect of the present invention, the pressure-sensitive optical fiber grating section is provided with an ambient temperature compensating optical fiber grating section in which an optical fiber grating is housed in a pressure-resistant container. Since the backup laser light source is arranged side by side with the laser light source, even if the ambient temperature of the external environment fluctuates, it is possible to obtain temperature-compensated measurement data of the water surface level. Even if the laser light source is turned off, the backup laser light source can be operated, and thus measurement data can be obtained for a long period of time.

Further, according to the invention of claim 6, N backup laser light sources are arranged in parallel with the laser light source, and an ignition signal multi-path switching means for sequentially igniting the N backup laser light sources is provided. Therefore, even if the operating laser light source is turned off or the backup laser power supply that is turned on is turned off instead, the remaining backup laser light sources can be ignited in order,
Observation can be continued for a long time, and measurement data can be obtained continuously.

According to the seventh aspect of the present invention, the pressure-sensitive optical fiber grating in the water pressure / oscillation wavelength converter is provided with a hydrophone, an underwater microphone, or an underwater microphone for collecting underwater acoustic data based on underwater seismic motion. The underwater acoustic wave is detected by the optical fiber grating for pressure sensing, and can be used for observation of natural earthquakes or artificial earthquakes.

Further, according to the invention of claim 8, the temperature data near the water bottom where the water pressure sensor is installed is detected by the optical fiber grating for ambient temperature compensation in the water pressure / oscillation wavelength converter, and this is detected. It can be used for observing temperature fluctuation trends.

[Brief description of the drawings]

1A is a block diagram for explaining a measurement principle of a water pressure sensor of the present invention, and FIG. 1B is a laser light source / oscillation wavelength measurement cut along a dotted line AA shown in FIG. 1A. Part 20
FIG. 4C is a cross-sectional view of the first side, and FIG. 4C is a graph showing the relationship between the depth m of fresh water and the oscillation wavelength nm.

FIG. 2 is a block diagram of a water pressure sensor having an optical fiber grating according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing a casing of the water pressure sensor shown in FIG. 2 with a part cut away.

FIG. 4 is a block diagram of a water pressure sensor shown in a second embodiment in which an optical fiber grating for temperature compensation is provided in parallel to the first embodiment shown in FIG.

FIG. 5 is a perspective view of the water pressure sensor with the casing of the water pressure sensor shown in FIG. 4 removed.

6 is a block diagram showing an example in which a number of backup laser light sources are arranged in parallel with the initial drive laser light source shown in FIG. 4;

FIG. 7 is a Bumuk diagram of a third embodiment of a water pressure sensor including a plurality of sets of measurement systems having an optical fiber grating.

8 is a perspective view of a part of the casing 2 of the water pressure sensor shown in FIG. 7, which is cut and removed along a solid line BB.

FIG. 9 is a diagram showing an example in which a number of measurement systems of the present invention are arranged in a measurement area and connected by a power supply / optical signal transmission cable.

FIG. 10 is a block diagram of a conventional water pressure sensor that detects fluctuations in water pressure from a difference in oscillation frequency between a crystal oscillator circuit for pressure sensing and a crystal oscillator circuit for temperature compensation provided in a vessel installed on the sea floor. FIG.

11A is a configuration block diagram of a conventional measurement system showing a relationship between a tension applied to an optical fiber grating and an oscillation wavelength, and FIG. 11B is a diagram showing a situation where a grating is written on an optical fiber by a two-beam interference method. ,
(C) is a graph example of measurement data showing a relationship between the tension and the oscillation wavelength obtained by the measurement system shown in (A).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Water pressure sensor, 2 ... Casing of water pressure sensor, 3 ... Water outflow / inlet hole provided on the outer peripheral surface of casing 2, 4 ... Pressure-resistant container, 5 ... Protective cylinder, 6 ... ..Water outflow / inlet holes provided in protective tube 5; 7. Viscous liquid container containing optical fiber grating 8; 8.
Optical fiber grating, 9 ... viscous liquid filled in container 7, 10 ... optical fiber, 11 ...
・ Gold-evaporated reflector, 12 ・ ・ ・ Laser light source, 13 ・ ・ ・ Optical isolator, 14 ・ ・ ・ First optical coupler, 16 ・ ・
.Wavelength measuring device, 17... Second optical coupler,.
・ Power supply / optical signal transmission cable, 19 ・ ・ ・ Packing for watertight sealing, 21 ・ ・ ・ Water, 20 ・ ・ ・ Water surface, 21 ・ ・ ・
Underwater.

Claims (8)

[Claims] 1. A laser light generation / wavelength measurement unit provided in one half of a casing, and a hole for water inflow and outflow on an outer peripheral surface.
A water pressure sensor provided in the other half of the casing and including a measurement system including a water pressure / oscillation wavelength conversion unit having a built-in optical fiber grating, wherein the laser light generation / wavelength measurement unit includes a laser light source. Along with sending the laser excitation light through the optical fiber to the water pressure / oscillation wavelength converter, the laser excitation light is reflected and sent from the water pressure / oscillation wavelength converter,
It is configured to measure the wavelength of the converted water pressure / oscillation wavelength signal corresponding to the water level, and transmit the obtained oscillation wavelength measurement signal to a land station via a transmission cable for transmission. The portion is formed of a flexible thin film bag or the like, and is filled with a sufficient amount of viscous liquid so that the applied water pressure from the outer peripheral surface can be applied to the outer peripheral surface of the optical fiber grating as a hydrostatic pressure. A pressure-sensitive optical fiber grating unit having a built-in optical fiber grating that converts the oscillation wavelength of the laser excitation light incident from the laser light generation / wavelength measurement unit in accordance with the applied water pressure. With this configuration, a water pressure corresponding to the water surface level is applied to the optical fiber grating as a hydrostatic pressure through the viscous liquid-containing container, Water pressure sensor using an optical fiber, characterized in that sending converting in response to pressure, the oscillation wavelength measurement signals of the measured laser excitation light. 2. An optical fiber, comprising: a laser light generation / wavelength measurement unit provided on a pressure-resistant container attached to one half of a casing; and a hole for water inflow / outflow on an outer peripheral surface. A water pressure sensor having a measurement system including a water pressure / oscillation wavelength conversion unit having a built-in grating, wherein the laser light generation / wavelength measurement unit transmits the laser excitation light of a laser light source to the water pressure / oscillation wavelength via an optical fiber. A first optical coupler that transmits light toward the converter and separates and extracts a hydraulic pressure / oscillation wavelength conversion signal that is reflected and sent from the hydraulic pressure / oscillation wavelength converter; and the first optical coupler. A wavelength measuring device that measures and encodes the wavelength of the water pressure / oscillation wavelength conversion signal separated from the wavelength, and transmits an oscillation wavelength measurement signal from the wavelength measuring device to a land station transmitting signal. A second optical coupler superimposed on a carrier wave of the cable, wherein the water pressure / oscillation wavelength converter is formed of a flexible thin film bag or the like, and applies the applied water pressure from the outer peripheral surface to the optical fiber grating. In a container filled with a sufficient amount of viscous liquid so as to be able to apply hydrostatic pressure to the outer peripheral surface of the container, one end is connected to the first optical coupler side, and the other end is connected to the light reflecting member. By providing a pressure-sensitive optical fiber grating section containing a built-in optical fiber grating written in the optical fiber to be connected, the water pressure corresponding to the water surface level is made hydrostatic pressure through the viscous liquid-containing container to make the optical fiber Applied to the grating, converted in accordance with the water pressure, and converted the measured oscillation wavelength measurement signal of the laser excitation light into a signal for transmitting to the land station. A water pressure sensor using an optical fiber, wherein the water pressure is transmitted via a transmission cable. 3. A configuration in which the water pressure sensors are disposed at a plurality of water bottoms in a measurement water area, and the respective oscillation wavelength measurement signals from the water pressure sensors are transmitted by being superimposed on the transmission cable for land station transmission. The water pressure sensor according to claim 1, wherein a measurement network for monitoring a fluctuation state of a water level is formed in the measurement water area. 4. The laser beam generation / output to the water pressure sensor.
3. The water pressure sensor according to claim 1, wherein a plurality of sets of measurement systems each including a wavelength measurement unit and a water pressure / oscillation wavelength conversion unit are arranged in parallel. 5. The pressure-sensitive optical fiber grating section of the water pressure / oscillation wavelength conversion section houses the optical fiber grating in a pressure-resistant container filled with an inert gas, and only changes in ambient temperature to change in oscillation wavelength. An ambient temperature compensating optical fiber grating part to be converted is arranged in parallel, a backup laser light source is arranged in parallel with the laser light source, and the excitation light from the laser light source is split into two by an optical coupler for shunt, and one of the lasers is used. A light transmitting optical path system for transmitting light to the pressure-sensitive optical fiber grating section and the other laser light to the ambient temperature compensating optical fiber grating section; and a water pressure / oscillation transmitted from the pressure-sensitive optical fiber grating section. Sent from the optical fiber grating for wavelength conversion signal and ambient temperature compensation The wavelength of the converted ambient temperature / oscillation wavelength conversion signal is measured by a wavelength measuring device, and a transmission optical path system for mounting the obtained oscillation wavelength measurement signal on a transmission cable is formed. In this case, an optical path switching means for switching an optical path connecting the laser light source and the light transmitting optical path system to an optical path connecting the backup laser light source ignited by a control signal and the light transmitting optical path system is provided. The water pressure sensor according to claim 1 or 2, wherein: 6. An ignition system for arranging N backup laser light sources in parallel with the laser light source, and energizing and igniting the N backup laser light sources in sequence each time a control signal is applied. Signal multi-path switching means, when the laser light source is turned off, an optical path connecting the laser light source and the light transmitting optical path system to an optical path connecting the backup laser light source sequentially ignited and the light transmitting optical path system. The water pressure sensor according to claim 5, further comprising an optical path switching means for switching. 7. The method according to claim 1, wherein the water pressure sensor is installed at the bottom of the water, and the pressure-sensitive optical fiber grating in the water pressure / oscillation wavelength converter is used as a sound wave receiving sensor for observation of underwater seismic motion. The water pressure sensor according to claim 1 or 2, wherein the underwater acoustic wave is measured. 8. The method according to claim 1, wherein the water pressure sensor is installed on the bottom of the water, and the optical fiber grating for compensating ambient temperature in the water pressure / oscillation wavelength converter is used as a temperature sensor for detecting the underwater temperature near the water bottom. The water pressure sensor according to claim 5, wherein ambient temperature data is collected.