JP2011053146A - Detection cable, and monitoring system including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detection cable which can detect a material to be detected always in real time for a long period, and to provide a monitoring system including the cable. <P>SOLUTION: This detection cable 2 for detecting the specific material to be detected by utilizing a Brillouin scattering phenomenon and/or a Rayleigh scattering phenomenon in optical fibers 9, 12 includes: a detection optical fiber 9; a reaction member 10 for applying a pressure and/or heat to the detection optical fiber 9 by being brought into contact with the material to be detected; and a comparison optical fiber 12 disposed along the detection optical fiber 9, whose periphery is surrounded to be in a prescribed reference state. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a detection cable for detecting a specific substance to be detected using an optical fiber, and a monitoring system including the same.

In recent years, the effects of greenhouse gases have been pointed out as one of the causes of global warming, and in particular, efforts to prevent global warming by reducing greenhouse gases such as carbon dioxide (CO ₂ ). Has been made worldwide. As one of such efforts, a technique for reducing CO ₂ emissions by storing CO ₂ emitted from factories, power plants, etc. in the ground to reduce CO ₂ emissions is an effective method for reducing CO ₂ emissions. It is believed that.

In this underground storage, a specific substance (in this case, OC ₂ ) is extracted from exhaust gas discharged from a factory, power plant, etc., and this specific substance is depleted in oil fields, gas fields, and salt water in the deep underground. After being injected into an aquifer or the like, a specific substance is permanently stored in the ground by closing the injection well. In the practical use of underground storage, it is necessary to monitor the storage state of a specific substance stored in the deep underground. Specifically, whether or not a specific material that is injected is stored in the deep underground (that is, there is a specific material that is injected in a storage region in the deep underground where the specific material is to be stored). It is necessary to monitor whether or not certain stored substances are leaking.

  Conventionally, this monitoring method is based on the difference between the velocity of the elastic wave (P wave) in the storage area where the specific substance is stored and the velocity of the elastic wave in the underground area not including the specific substance. A method for confirming the presence of a specific substance is known. Specifically, a microearthquake is generated on the ground surface, and the reflected wave (P wave) is measured to determine whether or not a specific substance is present in the storage region. Moreover, by measuring the range where the specific substance exists in the ground, the leakage of the specific substance from the storage area was judged based on the fluctuation of this range.

A monitoring method described in Patent Document 1 is also known. As shown in FIG. 29, this monitoring method uses a neutron gun 501 that irradiates a neutron beam and a radiation detector 502 that measures γ-rays. The γ-rays emitted when (in this case CO ₂ ) is irradiated with neutrons are measured. And by analyzing this measurement result, while confirming the presence of the specific substance stored, the leak of the specific substance from the storage area was judged based on the fluctuation of the range.

JP-A-2005-127893

  However, with the above method, it is difficult to constantly generate microearthquakes, and it may be dangerous to always irradiate neutrons that require the most attention in handling radiation. It has been difficult to monitor specific substances that have been made for a long period of time (for example, several years or more) constantly and in real time.

  Therefore, in view of the above problems, an object of the present invention is to provide a detection cable capable of detecting a substance to be detected for a long period of time constantly and in real time, and a monitoring system including the same.

  Accordingly, in order to solve the above problems, the present invention provides a detection cable for detecting a specific substance to be detected using the Brillouin scattering phenomenon and / or the Rayleigh scattering phenomenon in an optical fiber, A fiber, a reaction member that applies pressure and / or heat to the detection optical fiber by being in contact with the substance to be detected, a comparison optical fiber disposed along the detection optical fiber, and the comparison light And a protective member for relieving pressure and / or heat applied to the fiber from the outside.

  According to this detection cable, by comparing scattered light based on the Brillouin scattering phenomenon and / or the Rayleigh scattering phenomenon in each optical fiber of the detection optical fiber and the comparison optical fiber, the reaction member can be compared with the substance to be detected. It is possible to accurately measure the pressure and / or heat applied to the optical fiber for detection due to contact, thereby reliably detecting the substance to be detected in the area where the detection cable is arranged (monitoring target area). And it becomes possible to carry out with high precision. In addition, in the detection cable, since the detection target substance can be detected by making the inspection light incident on both optical fibers and measuring the scattered light, the detection target substance can be detected by keeping the inspection light incident on both fibers. It is possible to detect this in a long time, constantly and in real time.

  In the detection cable according to the present invention, the reaction member is preferably provided continuously or intermittently along the detection optical fiber.

  In this case, it becomes possible to detect the substance to be detected in each region where the reaction member is provided in the longitudinal direction of the detection optical fiber. In other words, the detection cable can detect the substance to be detected continuously or intermittently along the longitudinal direction.

  In addition, the reaction member covers the detection optical fiber in the circumferential direction, the volume of the reaction member is changed by coming into contact with the detected substance, and the heat of the contacted detected substance is transmitted to the detection optical fiber It may be constituted by.

  In this case, since the pressure and heat are applied to the detection optical fiber when the reaction member is in contact with the detection target substance, the detection target substance can be detected more reliably.

  That is, in the detection cable, when the reaction member comes into contact with the substance to be detected, its volume changes and the pressure applied to the detection optical fiber (force tightened by the reaction member covered in the circumferential direction) changes and Since the heat of the detected substance in contact with the member is applied to the detection optical fiber, the detected substance is detected from both the change in pressure applied to the detection optical fiber and the change in heat.

  More preferably, the reaction member is deformed according to the concentration of the substance to be detected in contact therewith.

  In this case, since pressure and heat according to the concentration and temperature of the substance to be detected in contact with the reaction member are applied to the optical fiber for detection, the scattered light based on the Brillouin scattering phenomenon and the Rayleigh scattering phenomenon in each optical fiber is compared. Then, by measuring the pressure and heat applied to the detection optical fiber, the concentration and temperature of the substance to be detected in the monitoring target region can be detected with high accuracy.

  In other words, the detection cable is deformed according to the concentration of the detected substance in contact, that is, the amount of change in the volume of the reaction member changes. Therefore, the detection cable is added to the detection optical fiber according to the concentration of the detected substance in contact with the reaction member. As the pressure (force tightened by the reaction member covered in the circumferential direction) changes and the heat applied to the detection optical fiber changes according to the heat of the detection substance in contact with the reaction member, the concentration of the detection substance Both temperature and temperature can be detected.

  A screening member that collectively surrounds the detection optical fiber and the reaction member from the outside, and that allows the detection substance to pass from the outside to the inside where the detection optical fiber and the reaction member exist; Is preferred.

  In this case, the selection member selectively allows the substance to be detected to permeate the inside thereof, so that the contact of the other substance with the reaction member is suppressed and the contact of the substance to be detected with the reaction member is sufficiently ensured. As a result, the detection sensitivity of the substance to be detected is improved.

  Alternatively, since the selection member selectively transmits the substance to be detected, even if it is a material that applies pressure and / or heat to the optical fiber for detection even if it is in contact with another substance other than the substance to be detected, it can be used as a reaction member. This increases the degree of freedom in selecting the reaction member material.

  The reaction member further includes a removing unit capable of heating or pressurizing the reaction member, and the reaction member absorbs or adsorbs the detected substance by being in contact with the detected substance, and is heated or pressurized by the removing unit. Thus, it is preferable to release or desorb the substance to be detected that has been absorbed or adsorbed.

  In this case, the detected substance absorbed or adsorbed on the reaction member by the removing means at regular or arbitrary intervals is released from or desorbed from the reaction member, so that the change in the detected substance over time in the monitoring target region can be detected. It becomes easy.

  The removing means includes a pressurizing tube that circulates fluid inside and expands in a radial direction when the liquid is heated to pressurize the reaction member, and the reaction member is pressurized by the pressurization tube. Thus, the substance to be detected that has been absorbed or adsorbed may be released or desorbed.

  In this case, the removal means can have a simple configuration. In addition, with a simple configuration, maintainability is improved, and sufficient durability that can withstand detection of a substance to be detected for a long time can be secured.

  When the pressurizing tube is disposed, the cable sheath further includes at least the detection optical fiber, the reaction member, the comparison optical fiber, the protection member, and a cable sheath that collectively surrounds the pressurization tube from the outside. It is more preferable to have a communication part that allows the detected substance to pass through by communicating the outside and the inside.

  By being surrounded by the cable sheath in this way, the pressure due to the expansion of the pressurizing tube is efficiently transmitted to the reaction member without escaping outside. In addition, the detection optical fiber, the reaction member, the comparison optical fiber, the protection member, and the pressure tube are protected by the cable sheath by being collectively surrounded from the outside, and the area around the detection cable is specified by the communication portion. Since free entry of the substance into the cable sheath is allowed, contact between the reaction member and the substance to be detected is sufficiently ensured even if the periphery is surrounded by the cable sheath.

  The protective member is preferably a protective pipe that surrounds the comparison optical fiber.

  In this case, the comparative optical fiber can be protected from pressure and / or heat applied from the outside with a simple configuration. In addition, with a simple configuration, maintainability is improved, and sufficient durability that can withstand detection of a substance to be detected for a long time can be secured.

  It is preferable that the optical fiber further includes a slot extending along the detection optical fiber and having a plurality of spiral grooves on the surface, and the detection optical fiber and the comparison optical fiber are accommodated in different grooves.

  In this case, since the relative positions of the detection optical fiber and the comparison optical fiber are fixed, it becomes easy to compare the scattered light based on the Brillouin scattering phenomenon and / or the Rayleigh scattering phenomenon in each optical fiber. In addition, a groove is provided in the slot in a spiral shape, and the detection optical fiber and the comparison optical fiber are accommodated in the groove, so that damage to each optical fiber due to the bending of the detection cable is prevented.

  In order to solve the above problem, the present invention is a monitoring system that monitors a specific substance to be detected using an optical fiber, and includes any one of the detection cables described above and the detection light of the detection cables. A light source for injecting inspection light into the fiber and the comparison optical fiber, and scattered light based on the Brillouin scattering phenomenon and / or the Rayleigh scattering phenomenon caused by the inspection light in the detection optical fiber and the comparison optical fiber, respectively. Measuring means for measuring, and calculating means for detecting the substance to be detected based on the scattered light in the optical fiber for detection measured by the measuring means and the scattered light in the optical fiber for comparison. It is characterized by that.

  According to this monitoring system, by comparing the scattered light based on the Brillouin scattering phenomenon and / or the Rayleigh scattering phenomenon generated by the inspection light incident in each optical fiber of the detection cable disposed in the monitoring target region, It is possible to accurately measure the pressure and / or heat applied to the detection optical fiber due to the reaction member coming into contact with the detected substance, and this enables reliable and highly accurate detection of the detected substance in the monitoring target region. It becomes possible, and based on this detection result, it is possible to monitor the substance to be detected reliably and with high accuracy. Moreover, since the test substance can be monitored by making the test light incident on both optical fibers of the detection cable and measuring the scattered light, the test light can be monitored by continuing to make the test light incident on both fibers. Monitoring can be performed constantly and in real time for a long time.

  The measurement means includes a Brillouin measurement unit for deriving a Brillouin frequency shift amount due to pressure and heat applied to each optical fiber by using a Brillouin scattering phenomenon in the detection optical fiber and the comparison optical fiber, and the detection A Rayleigh measurement unit for deriving a Rayleigh frequency shift amount due to pressure and heat applied to each optical fiber using the Rayleigh scattering phenomenon in the optical fiber for comparison and in the comparative optical fiber, and the calculation means includes the Brillouin frequency shift amount in the detection optical fiber and the comparison optical fiber derived by the Brillouin measurement unit, and Rayleigh frequency shift amount in the detection optical fiber and the comparison optical fiber derived by the Rayleigh measurement unit, Based on the above, the length around the optical fiber for detection Preferably, the is configured to calculate the concentration distribution and temperature distribution of the detected material in countercurrent.

  In this case, since the concentration and temperature of the substance to be detected in each region in the longitudinal direction around the detection cable can be detected simultaneously and independently with high spatial resolution, the detection in the longitudinal direction around the detection cable is possible. It becomes possible to monitor the distribution of substances.

  That is, the Brillouin frequency shift due to strain and temperature generated in each optical fiber is measured using the Brillouin scattering phenomenon, and the Rayleigh frequency shift due to strain and temperature generated in each optical fiber using the Rayleigh scattering phenomenon. By measuring the amount, the strain and temperature generated in each optical fiber can be calculated simultaneously and independently using the two frequency shift amounts, thereby detecting the length in the longitudinal direction around the detection cable. The concentration distribution and temperature distribution of the substance can be measured simultaneously and independently with high spatial resolution.

  The Brillouin measurement unit relates to an actual measurement position determined based on a travel time of light propagating through each optical fiber, and a measurement desired position on the optical fiber that deviates from the actual measurement position as the optical fibers expand and contract. A correction amount is derived, and the Brillouin frequency shift amount is derived using the correction amount, and the Rayleigh measurement unit derives the Rayleigh frequency shift amount using the correction amount derived by the Brillouin measurement unit. Is preferred.

  In this case, even if the detection cable is long, or the temperature change and distortion change in the detection cable are large, the substance to be detected in each region in the longitudinal direction around the detection cable can be accurately detected. As a result, the substance to be detected can be monitored accurately even in the detection target area away from the monitor.

  That is, the expansion / contraction due to the external force and temperature change in each optical fiber in the detection cable is large, and the position in the optical fiber where the Brillouin backscattered light actually measured is generated (measured position) and the Brillouin frequency shift amount. Even if there is a large deviation from the position (desired measurement position) in the optical fiber where the measurement value of the Brillouin backscattered light is desired to be derived, a correction amount relating to this deviation is derived from the Brillouin backscattered light, and this correction amount Can be used to accurately derive the Brillouin frequency shift amount and the Rayleigh frequency shift amount. In addition, by correcting the deviation between the actual measurement position and the measurement desired position corresponding to this actual measurement position using the correction amount, it is possible to reliably derive the Rayleigh frequency shift amount that is easily affected by the deviation.

  As a result, it is possible to measure both the concentration distribution and temperature distribution of the substance to be detected in each region in the longitudinal direction around the detection cable with high accuracy and high spatial resolution.

  As described above, according to the present invention, it is possible to provide a detection cable capable of detecting a substance to be detected for a long period of time, in real time, and a monitoring system including the same.

It is the schematic which shows the installation state of the monitoring system which concerns on 1st Embodiment. It is a figure which shows the cable for a detection of the said monitoring system, Comprising: (A) is an expanded cross-sectional view, (B) is a front view. It is a partially broken perspective view of a sensor fiber portion in the detection cable. It is a block diagram of the monitoring apparatus main body of the monitoring system. It is a block diagram which shows the structure of the measurement means for a detection of the state in which the optical fiber in the said monitoring apparatus main body was connected, and the measurement means for a comparison. It is a figure explaining the relationship between an actual measurement position and a measurement desired position, Comprising: (A) shows the relationship between the actual measurement position in a reference state optical fiber, and a measurement desired position, (B) is an external force to the optical fiber in a reference state. It is a figure which shows the relationship between the actual measurement position of the state which added, and the measurement desired position. It is a block diagram which shows schematic structure of the measurement means for a detection for demonstrating operation | movement of the measurement means for a detection shown in FIG. 5, and the measurement means for a comparison. It is a flowchart for demonstrating the monitoring operation | movement in the said monitoring system. It is a figure for demonstrating the structure and operation | movement of an optical pulse production | generation part shown in FIG. (A) explains the configuration of pump light (sub light pulse and main light pulse), and (B) is a diagram for explaining a matched filter. FIG. 6 is a diagram illustrating an example of pulsed light emitted from the optical pulse generation unit illustrated in FIG. 5, where (A) illustrates the wavelength of the pulsed light and (B) illustrates the waveform of the pulsed light. It is a figure which shows an example of the derivation | leading-out method of correction amount, Comprising: (A) shows a reference area and a correction area, (B) shows the correlation with the waveform in a reference area, and the waveform in each correction area. It is. It is a figure which shows the peak frequency of the Brillouin spectrum in each position in the elongate direction of the optical fiber for detection to which the different kind fiber was connected in the middle. It is a figure which shows an example of the Rayleigh frequency shift amount measured by the said measuring means for a detection, or the measuring means for a comparison, (A) shows the Rayleigh spectrum with and without an optical fiber, (B) Indicates correlation coefficients between when there is distortion and when there is distortion, and (C) is a diagram in which the waveform of one Rayleigh spectrum with and without distortion is moved and superimposed. It is the schematic which shows the installation state of the monitoring system which concerns on 1st Embodiment. It is a block diagram which shows the structure of the measurement means for a detection in the state which the optical fiber in the monitoring apparatus main body of the said monitoring system was connected, and the measurement means for a comparison. It is a block diagram which shows schematic structure of the measurement means for a detection for demonstrating operation | movement of the measurement means for a detection shown in FIG. 16, and the measurement means for a comparison. It is a block diagram which shows the structure of the measurement means for a detection in case the measurement means for a detection shown in FIG.5 and FIG.16 and the measurement means for a comparison are comprised in BOTDR, and a measurement means for a comparison. It is a figure for demonstrating a narrow line | wire width optical bandpass filter, Comprising: (A) is a block diagram which shows the structure of a narrow line | wire width optical bandpass filter, (B) thru | or (D) are narrow line | wire widths. It is a figure for demonstrating operation | movement of an optical band pass filter. FIG. 6 is a diagram for explaining a method for obtaining a Brillouin frequency shift by subtracting components from the whole, wherein (A) shows first to third Brillouin spectra, and (B) shows second and second Brillouin spectra from the whole. It is a figure which shows the result of subtracting a 3rd Brillouin spectrum. It is a figure for demonstrating the other structure of pump light (a sub light pulse and a main light pulse). It is a figure which shows the experimental result of the measurement means for a detection in the case of using the pump light of the structure shown to FIG. 21 (B), and a comparison measurement means, Comprising: (A) shows a Brillouin gain spectrum, (B) Indicates Brillouin frequency shift. It is a figure for demonstrating the further another structure and matching filter of pump light (a sub light pulse and a main light pulse). It is a figure for demonstrating the structure and operation | movement of an optical pulse production | generation part for producing | generating the pump light of the structure shown to FIG. 23 (A). It is a figure which shows the waveform of the sub light pulse of another example, and the main light pulse. It is a figure which shows the waveform of the sub light pulse of another example, and the main light pulse. It is a figure which shows the waveform of the sub light pulse of another example, and the main light pulse. It is a figure which shows the waveform of the sub light pulse of another example, and the main light pulse. Conventional monitoring methods underground pooled CO ₂ is a diagram for explaining the.

  Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the monitoring system according to the present embodiment is a system that monitors CO ₂ (substance to be detected) stored in the ground. Specifically, the monitoring system 1 includes the presence of CO ₂ in the underground reservoir R (in this embodiment, for example, a deep underground saline layer), the amount of CO ₂ stored, the state of stored CO ₂ , and storage. The leakage of CO _{2 from} the reservoir R is monitored, and a detection cable 2 and a monitoring device body 3 are provided.

Detection cable 2 (in the present embodiment, the ground) monitored region for monitoring CO ₂ is disposed in a cable used as a sensor for detecting the CO _2. As shown in FIG. 2A, the detection cable 2 includes a sensor fiber portion 4, a comparison fiber portion 5, a pressurizing tube 6, and the sensor fiber portion 4, the comparative fiber portion 5 and the pressurizing tube 6. A cable sheath 7 that surrounds the cable sheath 7 from the outside, and a slot 8 that positions the sensor fiber portion 4, the comparison fiber portion 5, and the pressure tube 6 in the cable sheath 7.

  As shown in FIG. 3, the sensor fiber portion 4 includes a detection optical fiber 9, a reaction member 10, and a gate member (selection member) 11. The detection optical fiber 9, the reaction member 10, and the gate member 11 are arranged with the reaction member 10 and the gate member 11 in order from the detection optical fiber 9 so as to be coaxial with each other. Is done.

The reaction member 10 is a member that applies pressure to the detection optical fiber 9 by being in contact with a specific substance to be detected (CO _{2 in} this embodiment). The reaction member 10 is provided along the detection optical fiber 9. The reaction member 10 covers the detection optical fiber 9 in the circumferential direction. The reaction member 10 is made of a material that changes its volume when it comes into contact with CO ₂ and transmits heat of the CO ₂ in contact with the detection optical fiber 9.

Specifically, the reaction member 10 is deformed to absorb the CO ₂ by contacting the CO _2. That is, site CO ₂ and contact of the reaction member 10, the volume of the site (larger) varies by absorbing the CO _2. Thus, when the reaction member 10 comes into contact with CO ₂ and the volume increases, the detection optical fiber 9 covered in the circumferential direction by the reaction member 10 is tightened by the reaction member 10, that is, the detection optical fiber 9 is attached to the detection optical fiber 9. On the other hand, pressure is applied toward the center in the radial direction, which causes deformation, distortion, and elongation in the detection optical fiber 9. The amount of change in the volume of the reaction member 10 varies depending on the concentration of CO _{2 with which} the reaction member 10 is in contact. That is, when the concentration of CO ₂ in contact is high, the amount of CO ₂ absorbed is large, so that the amount of change in volume in the reaction member 10 is large (that is, tightening of the detection optical fiber 9 by the reaction member 10 becomes strong), and the concentration is high. If it is low, the amount of CO ₂ to be absorbed is small, so the amount of change in volume is small (that is, the detection optical fiber 9 is loosely tightened by the reaction member 10).

In addition, the reaction member 10 releases the absorbed CO ₂ when pressure is applied. The reaction member 10 of the present embodiment is pressurized by the removing means re having the pressurizing tube 6 and the slot 8, and thereby releases the absorbed CO ₂ .

In this embodiment, since the reaction member 10 releases CO ₂ absorbed when pressure is applied, the detection cable 2 is provided with a removing means re. _In the case where the volume of CO ₂ is absorbed and released in accordance with the fluctuation of the _two concentrations and the volume thereof fluctuates, it is not necessary to provide the removing means re in the detection cable 2.

Further, the reaction member 10 may be made of a material that changes in temperature (for example, generates heat) by being in contact with CO ₂ . In this case, the reaction member 10 is CO ₂ and that heat is applied to the sensing optical fiber 9 in contact, it is possible to detect the CO ₂ by detecting the temperature change of the sensing optical fiber 9 by the heat. Even when such a material is used for the reaction member 10, a material whose calorific value varies according to the concentration of CO ₂ in contact with the reaction member 10 is preferable.

The gate member 11 collectively surrounds the detection optical fiber 9 and the reaction member 10 from the outside, and from the outside (radially outside) to the inside (diameter inside, that is, the detection optical fiber 9 and the reaction member 10 are present. This is a member that allows permeation of CO ₂ to the side).

Specifically, the gate member 11 covers the detection optical fiber 9 covered with the reaction member 10 in the circumferential direction from the outer side of the reaction member 10 in the circumferential direction (see FIG. 3). This gate member 11 allows permeation of CO ₂ from outside to inside and permeation of CO ₂ from inside to outside, while blocking permeation of other substances (molecules). That is, the gate member 11 selectively transmits only CO ₂ to the reaction member 10 side from among a plurality of substances existing around (outside). As a result, the reaction member 10 is prevented from coming into contact with other substances, and sufficient contact with CO ₂ is ensured.

The comparison fiber portion 5 is disposed along the sensor fiber portion 4 and includes a comparison optical fiber 12 and a protection pipe (protection member) 13 surrounding the periphery. In the present embodiment, a metal pipe is used as the protective pipe 13. In the comparison fiber portion 5, the periphery of the comparison optical fiber 12 is surrounded by a metal tube 13, so that the detection cable 2 is disposed in the monitoring target region and the CO ₂ (substance to be detected) around the detection cable 2 is detected. Even if the state (concentration, temperature, etc.) fluctuates, the periphery of the comparison optical fiber 12 is maintained in a predetermined reference state. The comparison fiber portion 5 of the present embodiment is configured by a so-called metal tube coated optical fiber (FIMT: Fiber In Metal Tube).

  The pressurizing tube 6 is a tube body in which a liquid (water in the present embodiment) is sealed, and is configured so that the pressurized tube 6 also expands in the radial direction when the sealed liquid is heated and thermally expanded. The

The cable sheath 7 is a tube body that houses the sensor fiber portion 4, the comparison fiber portion 5, and the pressure tube 6. The cable sheath 7 is a metal tube and includes a sensing unit 14 and a non-sensing unit 15. The sensing unit 14 is a part provided on the peripheral wall with a communication unit 14a that communicates the inside and the outside. In the sensing unit 14 of the present embodiment, a plurality of holes (communication portions) 14a, 14a,... Are provided so as to be arranged in a spiral shape (see FIG. 2B). The specific configuration of the communication portion 14a provided in the sensing portion 14 is not limited, and may be a round hole as in the present embodiment, an irregularly shaped hole, a slit, or the like. That is, the sensing unit 14 freely enters and exits the inside of the cable sheath 7 by a substance existing in the outer periphery of the cable sheath 7 (in this embodiment, a substance containing CO ₂ or CO ₂ (for example, salt water or crude oil)). Any configuration can be used. On the other hand, the non-sensing part 15 is a part that does not have the communication part 14a in the cable sheath 7, that is, a part that is configured so that substances existing around the outside of the cable sheath 7 cannot freely enter and exit inside.

  The cable sheath 7 of the present embodiment has one sensing portion 14 on the distal end side (lower side in FIG. 2B). However, the cable sheath 7 is not limited to this configuration. For example, in the longitudinal direction of the cable sheath 7, the sensing unit 14 may be provided at an intermediate position or may be provided at a plurality of locations. The cable sheath 7 may be configured by the sensing unit 14 in the entire length direction (that is, the non-sensing unit 15 may not be provided).

  The slot 8 is a long body having an outer diameter corresponding to the inner diameter of the cable sheath 7, and a groove 8 a is provided on the surface. The groove 8a is a U groove that is recessed toward the center in the radial direction, and is spirally engraved in the longitudinal direction of the slot so as to be able to cope with the bending of the detection cable 2. The slot 8 of this embodiment is made of aluminum or polytetrafluoroethylene. Three grooves 8a are provided so that the sensor fiber part 4, the comparison fiber part 5, and the pressure tube 6 can be fitted respectively. The groove 8 a is engraved in a spiral shape in the longitudinal direction of the slot 8. The slot 8 is inserted into the cable sheath 7 with the sensor fiber portion 4, the comparison fiber portion 5, and the pressure tube 6 inserted in the groove 8 a, so that the sensor fiber portion 4 and the comparison fiber portion 5 are within the cable sheath 7. And the pressure tube 6 is positioned.

  The slot 8 configured as described above and the pressurizing tube 6 constitute a removing means re. The removing unit re is a unit that applies pressure to the reaction member 10. Specifically, the removing unit re applies pressure to the reaction member 10 as follows.

First, the liquid sealed in the pressurizing tube 6 is heated and thermally expanded by the heating means 23 (see FIG. 4) of the monitoring device main body 3, and the pressurizing tube 6 expands in the radial direction. By this swelling, the groove 8a of the slot 8 in which the pressurizing tube 6 is fitted is pushed and expanded. Since the slot 8 is surrounded by a metal cable sheath 7, the force received from the pressure tube 6 (the force that spreads the groove 8 a) cannot be released to the outside, and is transmitted through the slot 8. Then, it is transmitted to the sensor fiber portion 4 and the comparison fiber portion 5 that are fitted in the groove 8a different from the groove 8a in which the pressurizing tube 6 is fitted. Thereby, a pressure is applied to the sensor fiber portion 4 (specifically, the reaction member 10), and the reaction member 10 releases the absorbed CO ₂ .

  In the present embodiment, the cable sheath 7 is a SUS tube having an inner diameter of 2.8 cm and an outer diameter of 3.2 cm. The detection optical fiber 9 and the comparison optical fiber 12 are each an optical fiber having a diameter of 0.155 cm. The metal tube 13 is a SUS tube having an inner diameter of 0.44 cm and an outer diameter of 0.84.

  As shown in FIG. 4, the monitoring apparatus main body 3 includes a detection measuring unit 20, a comparative measuring unit 21, a comparison calculating unit 22, a heating unit 23, and a control unit 24. The monitoring device main body 3 is provided with a connection portion c for connecting the detection cable 2 to the monitoring device main body 3. A plurality of detection cables 2, 2,... Are connected to the monitoring apparatus main body 3 of the present embodiment. The monitoring device body 3 includes the detection measuring means 20, the comparison measuring means 21, the comparison calculating means 22 and the heating means 23 as one unit, and includes the number of units corresponding to the number of connectable detection cables 2. . A monitor (display means) 26 is connected to the monitoring device main body 3. In the monitoring apparatus main body 3 of the present embodiment, the display means 26 is provided separately, but may be provided integrally with the monitoring apparatus main body 3. The display unit 26 is not limited to a display unit that displays an image as in a CRT display device, and may be a unit that displays by printing such as an XY plotter or a printer.

  The detection measurement means 20 is optically connected to the optical fiber (detection optical fiber) 9 of the sensor fiber portion 4 of the detection cable 2 and measures the Brillouin frequency shift amount and the Rayleigh frequency shift amount in the optical fiber 9. To do. The comparison measurement means 21 is optically connected to the optical fiber (comparison optical fiber) 12 of the comparison fiber portion 5 of the detection cable 2 and measures the Brillouin frequency shift amount and the Rayleigh frequency shift amount in the optical fiber 12. To do. Since the detection measurement means 20 and the comparison measurement means 21 have the same configuration, only the detection measurement means 20 will be described in detail below with reference to FIG. Is omitted. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

  The detection measuring means 20 (or the comparison measuring means 21) is configured to inject inspection light (pump light and Light sources 101 and 120 for injecting probe light) and measuring means for measuring scattered light based on the Brillouin scattering phenomenon and the Rayleigh scattering phenomenon caused by the inspection light in the detection optical fiber 9. Specifically, the measuring means for detection 20 includes a first light source 101, optical couplers 102, 105, 108, 121, 123, 130, an optical pulse generator 103, optical switches 104, 122, and light intensity / polarization. Adjustment unit 106, optical circulators 107 and 112, optical connectors 109, 127 and 128, a first automatic temperature control unit (hereinafter abbreviated as “first ATC”) 110, and a first automatic frequency control unit (hereinafter referred to as “first automatic frequency control unit”). , Abbreviated as “first AFC”) 111, control processing unit 113, strain and temperature detector 114, temperature detection unit 116, reference optical fiber 117, and second automatic temperature control unit (hereinafter “ 118, a second automatic frequency control unit (hereinafter abbreviated as “second AFC”) 119, a second light source 120, a light intensity adjustment unit 124, and a 1 × 2 light switch. And a 129, 131.

  The first and second light sources 101 and 120 are held substantially constant at a predetermined temperature preset by the first and second ATCs 110 and 118, respectively, and a predetermined frequency preset by the first and second AFCs 111 and 119, respectively. Is a light source device that generates and emits continuous light of a predetermined frequency by being held substantially constant. The output terminal (emission terminal) of the first light source 101 is optically connected to the input terminal (incident terminal) of the optical coupler 102. The output terminal (emission terminal) of the second light source 120 is optically connected to the input terminal (incident terminal) of the optical coupler 121.

  Each of the first and second light sources 101 and 120 is, for example, a light emitting element, a temperature detecting element (for example, a thermistor) that detects the temperature of the light emitting element, and a rear side of the light emitting element. One light branched by an optical coupler (for example, a half mirror) that receives back light emitted from the light and splits it into two passes through a Fabry-Perot etalon filter (Fabry-perotetalon Filter) that is a periodic filter. A first light receiving element for receiving light, a second light receiving element for receiving the other light branched by the optical coupler, a temperature adjusting element, the light emitting element, the temperature detecting element, the optical coupler, the first and second light receiving elements, a fabric And a substrate on which a Perot etalon filter and a temperature adjusting element are disposed.

  The light emitting element is an element that emits light of a predetermined frequency with a narrow line width and can change an oscillation wavelength (oscillation frequency) by changing an element temperature or a drive current. For example, a multi-quantum well structure DFB laser And a tunable semiconductor laser (frequency tunable semiconductor laser) such as a tunable wavelength distribution Bragg reflection laser. Therefore, the first light source 101 also functions as a frequency variable light source.

  Each temperature detection element in the first and second light sources 101 and 120 outputs each detected temperature to the first and second ATCs 110 and 118, respectively. The first and second light receiving elements in the first and second light sources 101 and 120 are provided with photoelectric conversion elements such as photodiodes, for example, and each light receiving output corresponding to each light receiving light intensity is output to the first and second AFCs 111 and 119, respectively. To do. The temperature adjustment element is a component that adjusts the temperature of the substrate by generating heat and absorbing heat, and includes, for example, a thermoelectric conversion element such as a Peltier element or a Seebeck element.

  The first and second ATCs 110 and 118 respectively control the temperature adjustment elements based on the detection temperatures of the temperature detection elements in the first and second light sources 101 and 120 according to the control of the control processing unit 113, respectively. This circuit automatically keeps the temperature of each substrate at a predetermined temperature substantially constant. As a result, the temperature of each light emitting element in the first and second light sources 101 and 120 is automatically kept substantially constant at a predetermined temperature. For this reason, when the frequency of the light emitted from the light emitting element has temperature dependency, the temperature dependency is suppressed.

  The first and second AFCs 111 and 119 respectively control the light emitting elements based on the light reception outputs of the first and second light receiving elements in the first and second light sources 101 and 120 according to the control of the control processing unit 113, respectively. Thus, the frequency of the light emitted from each light emitting element is automatically kept substantially constant at a predetermined frequency, or is swept within a predetermined frequency range.

  The optical coupler, the Fabry-Perot etalon filter, the first and second light receiving elements, and the first and second AFCs 111 and 119 in the first and second light sources 101 and 120 are the light emitting elements in the first and second light sources 101 and 120, respectively. So-called wavelength lockers that substantially fix the wavelength (frequency) of the emitted light are configured.

  The optical couplers 102, 105, 121, and 123 are optical components that distribute incident light incident from one input terminal into two lights and emit them to two output terminals, respectively. The optical coupler 108 emits incident light incident from one input terminal of the two input terminals from one output terminal, and transmits incident light incident from the other input terminal from the output terminal. It is an optical component to be emitted. The optical coupler 130 is an optical component that couples two incident lights incident from two input terminals and emits them from the two output terminals. The optical couplers 102, 105, 121, 123, 108, and 130 are, for example, micro optical element type optical branch couplers such as half mirrors, fused fiber optical fiber type optical branch couplers, optical waveguide type optical branch couplers, and the like. Can be used.

  One output terminal of the optical coupler 102 is optically connected to the input terminal of the optical pulse generator 103, and the other output terminal is optically connected to the input terminal of the 1 × 2 optical switch 131. One output terminal of the optical coupler 105 is optically connected to the input terminal of the light intensity / polarization adjustment unit 106, and the other output terminal is optically connected to the input terminal of the strain and temperature detector 114. One output terminal of the optical coupler 121 is optically connected to the input terminal of the optical switch 122, and the other output terminal is optically connected to the other end of the reference optical fiber 117 via the optical connector 128. . One output terminal of the optical coupler 123 is optically connected to the input terminal of the light intensity adjusting unit 124, and the other output terminal is optically connected to the input terminal of the strain and temperature detector 114. One input terminal of the optical coupler 108 is optically connected to the second terminal of the optical circulator 107, the other input terminal is optically connected to the output terminal of the light intensity adjusting unit 124, and the output terminal is monitored. Optically connected to one end of the detection optical fiber 9 in the detection cable 2 via the optical connector 109 at the connection portion c of the apparatus main body 3. One input terminal of the optical coupler 130 is optically connected to the other output terminal of the 1 × 2 optical switch 131, and the other input terminal is optically connected to one output terminal of the 1 × 2 optical switch 129. The two output terminals are optically connected to the input terminals of the strain and temperature detector 114.

  The optical pulse generator 103 is a device that receives continuous light emitted from the first light source 101 and generates main light pulses and sub light pulses as pump light from the continuous light. The main light pulse is an optical pulse using a spread spectrum method. Examples of the spread spectrum method include a frequency chirp method that changes the frequency, a phase modulation method that modulates the phase, and a hybrid method that combines the frequency chirp method and the phase modulation method.

  Examples of the frequency chirp method include a method of changing the frequency monotonously, for example, linearly. Examples of the phase modulation method include a method of modulating the phase using a PN sequence. The PN sequence is a pseudo-random number sequence, and examples of the PN sequence include an M sequence (maximal-length sequences) and a Gold sequence. The M series can be generated by a circuit including a plurality of shift registers and a logic circuit that feeds back a logical combination of each state in each of the plurality of stages to the shift register. In addition, the Gold sequence is defined as M, Mj generated by n-order primitive polynomials F1 (x) and F2 (x), where 0 is -1 and 1 is +1. Can be generated by the product Mi · Mj. Also, a Golay code sequence can be used as a phase modulation type pseudo-random number sequence. This Golay code sequence has an excellent characteristic that the side lobe of the autocorrelation function is strictly zero. The sub light pulse is an unmodulated unmodulated light pulse, the maximum light intensity of which is equal to or less than the light intensity of the main light pulse, and the pulse width is sufficiently longer than the lifetime of the acoustic phonon.

  In the Brillouin spectrum time domain analysis (BOTDA) of the present embodiment, the optical pulse generator 103 detects the optical fiber 9 for detection before the sub optical pulse in time in the Brillouin spectrum time domain analysis (BOTDA) of this embodiment. The sub light pulse and the main light pulse are generated so as not to be incident on the light beam. The sub light pulse and the main light pulse as pump light generated by the light pulse generation unit 103 will be described later.

  The optical switches 104 and 122 are optical components that turn on / off light between the input terminal and the output terminal according to the control of the control processing unit 113. When on, light is transmitted, and when off, light is blocked. In the present embodiment, the optical switches 104 and 122 use a light intensity modulator that modulates the light intensity of incident light, such as an MZ light modulator or a semiconductor electroabsorption optical modulator. The optical switches 104 and 122 include a driver circuit that is controlled by the control processing unit 113 and drives the light intensity modulator. This driver circuit is, for example, a DC power source that generates a DC voltage signal for turning off the light intensity modulator in a normal state, and a pulse generator that generates a voltage pulse for turning on the light intensity modulator that is normally turned off. And a timing generator for controlling the generation timing of the voltage pulse. The output terminal of the optical switch 104 is optically connected to the input terminal of the optical coupler 105. The output terminal of the optical switch 122 is optically connected to the input terminal of the optical coupler 123.

  The light intensity / polarization adjusting unit 106 is a component that is controlled by the control processing unit 113 and adjusts the light intensity of incident light, and randomly changes the polarization plane of incident light and emits the light. The output terminal of the light intensity / polarization adjusting unit 106 is optically connected to the first terminal of the optical circulator 107. For example, the light intensity / polarization adjusting unit 106 attenuates the light intensity of the incident light and emits the light, and changes the amount of attenuation, and changes the polarization plane of the incident light at random. And a polarization controller that can be configured. The light intensity / polarization adjustment unit 106 is commonly used for measurement of stimulated Brillouin scattered light and Rayleigh backscattered light, and randomly changes the polarization plane of the light.

  The optical circulators 107 and 112 are irreversible optical components in which incident light and outgoing light have a cyclic relationship with their terminal numbers. That is, the light incident on the first terminal is emitted from the second terminal and is not emitted from the third terminal, and the light incident on the second terminal is emitted from the third terminal and the first terminal. The light which is not emitted from the first terminal but is incident on the third terminal is emitted from the first terminal and is not emitted from the second terminal. The first terminal of the optical circulator 107 is optically connected to the output terminal of the light intensity / polarization adjustment unit 106, the second terminal is optically connected to one input terminal of the optical coupler 108, and the third terminal is It is optically connected to the input terminal of the 1 × 2 optical switch 129. The first terminal of the optical circulator 112 is optically connected to one output terminal of the 1 × 2 optical switch 131, and the second terminal is optically connected to one end of the reference optical fiber 117 via the optical connector 127. The third terminal is optically connected to the input terminal of the strain and temperature detector 114.

  The optical connectors 109, 127, and 128 are optical components that optically connect optical fibers or optical components and optical fibers.

  The light intensity adjusting unit 124 is a component that is controlled by the control processing unit 113 and adjusts the light intensity of incident light and emits the light. The output terminal of the light intensity adjusting unit 124 is optically connected to the other input terminal of the optical coupler 108. The light intensity adjustment unit 124 includes, for example, a variable optical attenuator that attenuates and emits light intensity of incident light, and an optical isolator that transmits light only in one direction from the input terminal to the output terminal. The incident light incident on the light intensity adjusting unit 124 is emitted through an optical isolator after the light intensity is adjusted to a predetermined light intensity by an optical variable attenuator. This optical isolator plays a role of preventing the propagation of reflected light generated at the connection part of each optical component in the measuring means 20 for detection and the propagation of the sub light pulse and the main light pulse to the second light source 120.

  The 1 × 2 optical switches 129 and 131 are 1-input 2-output optical switches that emit light from one of the two output terminals by switching the optical path, for example, A mechanical optical switch, an optical waveguide switch, or the like is used.

  One output terminal of the 1 × 2 optical switch 129 is optically connected to the other input terminal of the optical coupler 130, and the other output terminal is optically connected to the strain and temperature detector 114. When operating in the Brillouin spectrum time domain analysis (BOTDA) mode according to the control (or manual) of the control processing unit 113, the light incident from the input terminal is incident on the strain and temperature detector 114. When the 1 × 2 optical switch 129 is switched to operate as a coherent optical pulse tester (COTDR) using the Rayleigh scattering phenomenon, light incident from the input terminal is incident on the other input terminal of the optical coupler 130. Thus, the 1 × 2 optical switch 129 is switched.

  One output terminal of the 1 × 2 optical switch 131 is optically connected to the first terminal of the optical circulator 112, and the other output terminal is optically connected to one input terminal of the optical coupler 130. When operating in the Brillouin spectrum time domain analysis (BOTDA) mode according to the control (or manual) of the control processing unit 113, 1 × 2 so that the light incident from the input terminal enters the optical circulator 112. When the optical switch 131 is switched to operate as a coherent optical pulse tester (COTDR) using the Rayleigh scattering phenomenon, the light incident from the input terminal is incident on one input terminal of the optical coupler 130. The 1 × 2 optical switch 131 is switched.

  Here, in the detection optical fiber 9 of the detection cable 2, in BOTDA, the sub light pulse, the main light pulse, and the continuous light are incident, the light subjected to the action of the stimulated Brillouin scattering phenomenon is emitted, and the Rayleigh When utilizing the scattering phenomenon, pulsed light is incident and light subjected to the effect of the Rayleigh scattering phenomenon is emitted.

  The reference optical fiber 117 is an optical fiber used to adjust the frequency of each light emitted from the first and second light sources 101 and 120, and the first and second light causing the stimulated Brillouin scattering phenomenon. The optical fiber has a known relationship between the frequency difference in the light and the light intensity of light related to the stimulated Brillouin scattering phenomenon. Further, the reference optical fiber 117 may be used for adjustment of light used for measurement of Rayleigh backscattered light.

  The temperature detection unit 116 is a circuit that detects the temperature of the reference optical fiber 117, and outputs the detected temperature to the control processing unit 113.

  The strain and temperature detector 114 includes a light receiving element, an optical switch, an amplifier circuit, an analog / digital converter, a signal processing circuit, a spectrum analyzer, a computer (CPU), a memory, and the like. The strain and temperature detector 114 controls each part of the measuring means 20 for detection by inputting and outputting signals to and from the control processing unit 113. The strain and temperature detector 114 obtains the light intensity of the light related to the stimulated Brillouin scattering phenomenon emitted from the reference optical fiber 117, which is incident on the input terminal via the optical connector 127 and the optical circulator 112, and the obtained light. The intensity is output to the control processing unit 113.

  Further, the strain and temperature detector 114 controls each part of the measurement means 20 by inputting / outputting signals to / from the control processing unit 113, and the 1 × 2 optical switch 129 is connected to the optical circulator 107 and detects strain and temperature. The light related to the stimulated Brillouin scattering phenomenon is incident on a light receiving element having one input terminal for stimulated Brillouin scattered light in the strain and temperature detector 114. The strain and temperature detector 114 is connected to a light receiving element for stimulated Brillouin scattered light by an internal switch and an amplifier circuit, and detects light related to the stimulated Brillouin scattering phenomenon received at a predetermined sampling interval. The Brillouin spectrum of each region portion of the detection optical fiber 9 in the longitudinal direction of the detection optical fiber 9 of the cable 2 is obtained, and the Brillouin frequency shift amount of each region portion is calculated based on the obtained Brillouin spectrum of each region portion. Ask for each.

  The strain and temperature detector 114 inputs and outputs signals to and from the control processing unit 113 to control each unit of the detection measuring unit 20. The 1 × 2 optical switch 129 includes the optical circulator 107, the optical coupler 130, and the like. Are connected to each other, and light related to the Rayleigh backscattering phenomenon is incident on a light receiving element having two input terminals for Rayleigh backscattered light in the strain and temperature detector 114 via the optical coupler 130. The strain and temperature detector 114 is connected to a light receiving element for Rayleigh backscattered light and an amplifier circuit by an internal switch, and detects light related to the Rayleigh backscattering phenomenon received at a predetermined sampling interval. The Rayleigh spectrum of each region portion of the detection optical fiber 9 in the longitudinal direction of the detection optical fiber 9 of the cable 2 is obtained, and the Rayleigh frequency shift amount of each region portion is calculated based on the obtained Rayleigh spectrum of each region portion. Ask for each.

  Further, the strain and temperature detector 114 simultaneously and independently calculates the strain distribution and the temperature distribution of the detection optical fiber 9 of the detection cable 2 from the Brillouin frequency shift amount and the Rayleigh frequency shift amount obtained as described above. To detect.

Further, the strain and temperature detector 114 has the detection optical fiber 9 in a state (reference state) before the start of monitoring of CO ₂ in this region after the detection cable 2 is disposed in the region to be monitored. When the light related to the stimulated Brillouin scattering phenomenon is incident on the light receiving element for the stimulated Brillouin scattered light in the temperature detector 114, the light receiving element for the stimulated Brillouin scattered light and the amplifier circuit are connected by an internal switch. The Brillouin spectrum of each region portion (measured position) of the detection optical fiber 9 in the longitudinal direction of the detection optical fiber 9 is detected by detecting the light related to the stimulated Brillouin scattering phenomenon received at a predetermined sampling interval. Ask. Then, the strain and temperature detector 114 obtains a frequency (reference peak frequency) corresponding to the peak from the Brillouin spectrum of each obtained area portion (measured position), and each obtained area portion (measured position) Is stored in the memory.

  Further, when the light related to the Rayleigh backscattering phenomenon from the detection optical fiber 9 in the reference state is incident on the light receiving element for Rayleigh backscattered light in the strain and temperature detector 114, the strain and temperature detector 114, A light receiving element for Rayleigh backscattered light and an amplifier circuit are connected by an internal switch, and light related to the Rayleigh backscattering phenomenon received at a predetermined sampling interval is detected, whereby the detection optical fiber 9 in the longitudinal direction is detected. The Rayleigh spectrum (reference Rayleigh spectrum) of each region portion (measured position) of the detection optical fiber 9 is obtained. Then, the strain and temperature detector 114 stores the obtained reference Rayleigh spectrum of each region (measured position) in a memory.

The strain and temperature detector 114 is a state in which the CPU detects CO _{2 in} the monitoring target region by using the reference peak frequency of each actual measurement position stored in the memory and the detection cable 2 in the CPU (monitoring state). The correction amount is derived from the peak frequency of the Brillouin spectrum obtained from the Brillouin backscattered light from the respective measured positions in the detection optical fiber 9).

  Here, the correction amount, the actual measurement position, and the measurement desired position will be described. FIG. 6 is a diagram for explaining the relationship between the actual measurement position and the measurement desired position. FIG. 6A shows the detection optical fiber 9 in the reference state, and FIG. 6B shows a state in which an external force is applied to the detection optical fiber 9 in the reference state.

  The correction amount corrects the deviation between the actual measurement position and the desired measurement position corresponding to this actual measurement position, and based on the Brillouin spectrum peak frequency obtained from the Brillouin backscattered light from the actual measurement position, the Brillouin backscatter from the measurement desired position It is used when estimating the peak frequency of the Brillouin spectrum obtained from light. The correction amount is used when estimating the Rayleigh spectrum obtained from the Rayleigh backscattered light from the measurement desired position from the Rayleigh spectrum obtained from the Rayleigh backscattered light from the actual measurement position.

  The actual measurement position is a position where the Brillouin spectrum or the Rayleigh spectrum is actually measured in the longitudinal direction of the detection optical fiber 9 by the detection measurement means 20 as described above (FIG. 6A and FIG. 6). (See the black dot in B)). In the present embodiment, for example, in the detection optical fiber 9, the positions are arranged at intervals of 5 cm from one end. The detection measuring means 20 measures the Brillouin backscattered light based on the time during which light propagates through the detection optical fiber 9. Even if the detection optical fiber 9 expands and contracts, the detection measurement means 20 passes through the detection optical fiber 9. Since the speed of the propagating light does not change, the measured position in the detection optical fiber 9 where the Brillouin backscattered light measured based on the time is changed even if the detection optical fiber 9 expands or contracts ( Do not move) (see black circle in FIG. 6B). That is, the distance from one end of the detection optical fiber 9, which is the end connected to the monitoring apparatus main body 3, to each measured position is constant regardless of the expansion and contraction of the detection optical fiber 9.

  On the other hand, the measurement desired position is a position set on the detection optical fiber 9 and is a position that overlaps the actual measurement position in the reference state (see the dotted lines in FIGS. 6A and 6B). . Since this desired measurement position is a position on the detection optical fiber 9, it shifts from the actual measurement position along with the distortion (expansion / contraction) of the detection optical fiber 9 (see the broken line in FIG. 6B). That is, the distance from one end of the detection optical fiber 9, which is the end connected to the monitoring apparatus main body 3, to each measurement desired position changes as the detection optical fiber 9 expands and contracts.

  The strain and temperature detector 114 uses the above correction amount to calculate the peak of the Brillouin spectrum at the measurement desired position corresponding to each measured position from the peak frequency of the Brillouin spectrum at each measured position in the detection optical fiber 9 in the monitoring state. Estimate the frequency. Further, the strain and temperature detector 114 estimates the Rayleigh spectrum of the measurement desired position corresponding to each measured position from the Rayleigh spectrum of each measured position in the monitoring optical fiber 9 in the monitoring state by using the above correction amount. .

  The strain and temperature detector 114 derives (measures) the Brillouin frequency shift amount Δνb based on the reference peak frequency at each actual measurement position and the peak frequency at the measurement desired position corresponding to each actual measurement position. Further, the strain and temperature detector 114 derives (measures) the Rayleigh frequency shift amount Δνr based on the reference Rayleigh spectrum at each actual measurement position and the Rayleigh spectrum at the measurement desired position corresponding to each actual measurement position.

  Each incident light incident from each input terminal of the strain and temperature detector 114 is converted into an electric signal corresponding to the amount of received light by a light receiving element that performs photoelectric conversion. Incident light incident as light related to the stimulated Brillouin scattering phenomenon is directly detected by being converted into an electric signal by a light receiving element, filtered by a matched filter, converted to a digital electric signal by an analog / digital converter, Used to determine Brillouin spectrum. Incident light incident as light related to the Rayleigh backscattering phenomenon is directly detected by being converted into an electric signal by a light receiving circuit, filtered by a matched filter, converted to a digital electric signal by an analog / digital converter, Used to determine the Rayleigh spectrum. Further, if necessary, the electric signal is amplified by the amplifier circuit before being digitally converted.

  The control processing unit 113 includes, for example, a microprocessor, a working memory, and a memory for storing data necessary for measuring the strain and temperature distribution of the detection optical fiber 9 of the detection cable 2 with high spatial resolution. Prepare. The control processing unit 113 inputs and outputs a signal to and from the strain and temperature detector 114 to thereby distribute the strain and temperature distribution of the detection optical fiber 9 in the longitudinal direction of the detection optical fiber 9 of the detection cable 2 in a high space. The first and second light sources 101 and 120, the first and second ATCs 110 and 118, the first and second AFCs 111 and 119, the optical pulse generator 103, the optical switches 104 and 122, so as to measure at a resolution and a longer distance. This is an electronic circuit that controls the light intensity / polarization adjusting unit 106, the 1 × 2 optical switches 129 and 131, and the light intensity adjusting unit 124.

  The control processing unit 113 includes a storage unit in which the relationship between the frequency difference between the first and second lights causing the stimulated Brillouin scattering phenomenon and the light intensity of the light related to the stimulated Brillouin scattering phenomenon in the reference optical fiber 117 is stored. First and second in the first and second light sources 101 and 120 based on the light intensity of the light related to the stimulated Brillouin scattering phenomenon obtained by the strain and temperature detector 114 and the known relationship in the reference optical fiber 117. A frequency setting unit that controls the first AFC 111 and / or the second AFC 119 is functionally provided so that the frequency difference of each light emitted from the light emitting element becomes a predetermined frequency difference set in advance. In addition, the control processing unit 113 functionally includes a frequency setting unit that controls the first AFC 111 so as to emit light that causes the Rayleigh backscattering phenomenon in the reference optical fiber 117.

  Here, the Brillouin frequency shift when the spread spectrum method is used for the light incident on the detection optical fiber 9 will be described below.

  The spread spectrum method or the pulse compression method is used to extend the measurable distance in the so-called radar field. This is because the spectrum of the pulse is diffused by using frequency modulation, phase modulation, etc. inside the pulse radiated to the space to detect the target, and demodulation called pulse compression is applied to the reflected wave reflected by the target. By doing so, the distance to the target is detected. Thereby, the energy of the pulse can be increased, and the measurable distance can be extended. Spread spectrum is generally deliberately increasing the bandwidth that is originally required to transmit a signal.

  When this spread spectrum method is applied to BOTDA, since the Brillouin frequency shift occurs through a non-linear process, the spectrum of the optical pulse is broadened (spread). Secondly, the spectrum in the time-series signal of the reflected wave for each frequency also spreads, and a double spread occurs in the spectrum. For this reason, the spread spectrum code cannot simply be applied to BOTDA. Therefore, the inventor of the present application applies the spread spectrum method to BOTDA by configuring the light pulse from the main light pulse and the sub light pulse and using the spread spectrum method for the main light pulse, as will be analyzed below. I found out that I can. This spread spectrum method can also be applied to BOTDR, which will be described later, and BOTDA in measuring both ends of an optical fiber.

  In the following, the case of BOTDA will be described. Similarly, it is possible to analyze BOTDR.

  In BOTDA, pump light is incident from one end (z = 0) of a detection optical fiber, and probe light having a frequency different from the frequency of the pump light is incident from the other end, and backscattering of excited acoustic phonons occurs. Observed at the end point of z = 0. Brillouin gain spectrum (BGS) is an increase in the power of the probe light.

First, the pump light A _p (0, t) is an optical pulse having a shape in which a complex envelope is expressed by Equation 1.

Here, P _p is the power of the pump light, and f (t) is a function representing the amplitude of the pump light at time t, and is normalized so that the maximum of its absolute value is 1. .

When the function is defined by Expression 2, the Fourier transform is expressed by Expression 3. In this case, the Brillouin gain spectrum V (t, ν) is a two-dimensional convolution and is expressed by Equation 4. The first term on the right side of Equation 4 is a time-varying Lorentz spectrum.

Here, the superscript * represents a complex conjugate, and i is a complex unit (i ² = −1). Further, γ is a gain coefficient, and ν _B (z) is a Brillouin frequency shift at the position z. G (ν) is a Lorentz spectrum, and _vg is a group velocity of pump light. The operator * represents convolution, and the superscripts t and ν represent two-dimensional convolution with respect to these variables. Note that the multiplication operator • is not shown.

  Here, ideally, the time-varying Lorentz spectrum itself of the first term on the right-hand side of Equation 4 is observed, but in reality, it is blurred by convolution with the point spread function ψ (t, ν). The observed Brillouin gain spectrum is observed. Therefore, it is necessary that the point spread function ψ (t, ν) is at or close to the two-dimensional delta function. Therefore, it is preferable that ψ (t, ν) ≈δ (t) δ (ν).

Here, the pump light is composed of the main light pulse f ₁ (t) and the sub light pulse f ₂ (t). That is, the amplitude f (t) of the pump light is expressed by Equation 5.

This sub light pulse functions to excite acoustic phonons for the main light pulse. The pulse width D _sub of the sub light pulse is made sufficiently longer than at least the lifetime of the acoustic phonon. The lifetime of acoustic phonons is usually about 5 ns.

  The main light pulse functions to pass the energy scattered by the acoustic phonon to the probe light. The main light pulse is divided into a plurality of cells with a predetermined time width in the time direction, and is broadened by using a spread spectrum system. Broadband is compared to the spectral linewidth (approximately 30-40 MHz) of acoustic phonons. The time width of this cell determines the spatial resolution of BOTDA, and this reciprocal is the width of the spectrum. For example, when the cell width (cell time width) is 0.1 ns, the spatial resolution is 1 cm and the spectrum width is 10 GHz. The pulse width D of the main light pulse determines the amount of energy given to the pump light in order to extend the measurable distance. Here, since the spatial resolution of BOTDA is determined by the cell width of the main optical pulse as described above, the pulse width D of the main optical pulse can be set independently of the spatial resolution of BOTDA. Therefore, the pulse width D of the main light pulse can be appropriately determined according to a desired measurable distance. For this reason, it becomes possible to extend measurable distance conventionally.

  When the pump light is composed of two components in this way, the Brillouin gain spectrum V (t, ν) is composed of three components, and Equations 6 and 7 (Equations 7-1 to 7-3) Represented by

  The point spread function ψ (t, ν) is expressed by Equation 8, and since the pump light is composed of the main light pulse and the sub light pulse, the point spread function ψ (t, ν) is It is represented by Equation 9 and Equation 10.

Here, in the spread spectrum method, a matched filter (matched filter) corresponding to the spread spectrum method is used for demodulation, and the impulse response h (t) of the matched filter is set to f ₁ (Dt) ( h (t) = f ₁ (D−t)). The matched filter, for example, inverts the signal used for spread spectrum (the code in the case of using a code sequence for spread spectrum) with respect to time and takes the convolution with the input of the matched filter.

The main light pulse uses a spread spectrum system, and the sub light pulse is unmodulated and its pulse width is sufficiently long. Therefore, the components ψ _1,2 (t, ν) can be approximated as in Equation 11 and is the preferred type.

Here, C _p is an amplitude ratio between the main light pulse and the sub light pulse.

  Therefore, the corresponding Brillouin gain spectrum is represented by Equation 12.

The other components V _1,1 (t, ν) and V _2,1 (t, ν) in the Brillouin gain spectrum V (t, ν) are spectrally spread with a main light pulse by pseudorandom numbers. In some cases, the spectrum is flat. The other components V _2,2 (t, ν) are suppressed by the matched filter at the time of demodulation.

Further, the components V _1,1 (t, ν) and V _2,2 (t, ν) in the Brillouin gain spectrum V (t, ν) are composed of only the main light pulse or the sub light pulse. And can be extracted by measuring the Brillouin gain spectrum.

  From the above analysis, in the detection measuring means 20, the light pulse incident on the detection optical fiber is composed of two components of a main light pulse using a spread spectrum method and an unmodulated sub light pulse, Since the spatial resolution and the measurable distance can be set independently, the measurable distance can be extended and further measured while the strain and temperature can be measured with high spatial resolution.

  Moreover, the measurement means 20 for detection shown in FIG. 5 functions as BOTDA when measuring the Brillouin frequency shift amount. FIG. 7 is a block diagram showing a schematic configuration of the detection measurement means 20 when the detection measurement means 20 shown in FIG. 5 is operated as BOTDA.

As shown in FIG. 7, the detection measuring means 20 uses the sub light pulse and the main light pulse generated by the light pulse light source LS _p as pump light, and probes the continuous light generated by the continuous light source LS _CW . Light enters from one end of the detection optical fiber 9 of the detection cable 2. A spread spectrum method is used for the main light pulse.

The detection measuring unit 20 receives light related to the stimulated Brillouin scattering phenomenon generated in the detection optical fiber 9 by the strain and temperature detector 114, and the Brillouin gain spectrum time domain analysis (B ^Gain- OTDA) or Brillouin loss spectrum time domain analysis (B ^Loss- OTDA) is performed to measure the Brillouin frequency shift amount.

In the optical pulse light source LS _p , the laser light emitted from the laser light source LD is phase-modulated by the pseudo random number from the pseudo random number generator RG in the optical signal generator OSG, so that the main optical pulse using the spread spectrum system is generated. Generated. The pseudorandom number generated by the pseudorandom number generator RG is notified to the strain and temperature detector 114 for demodulation. Then, in the strain and temperature detector 114, the light related to the stimulated Brillouin scattering phenomenon emitted from the detection optical fiber 9 is filtered by the matched filter MF corresponding to the pseudo random number from the pseudo random number generator RG, and the signal processing unit By performing BOTDA signal processing at the SP, the Brillouin frequency shift amount is measured.

  Hereinafter, Brillouin gain spectrum time domain analysis or Brillouin loss spectrum time domain analysis is abbreviated as Brillouin spectrum time domain analysis as appropriate. In this Brillouin spectrum time domain analysis, light related to the stimulated Brillouin scattering phenomenon is light that has undergone Brillouin amplification or attenuation.

  Next, the adjustment operation in the detection measuring means 20 will be described. First, before the monitoring operation, each frequency of each continuous light emitted from the first and second light sources 101 and 120 is adjusted (calibrated) using the reference optical fiber 117.

  More specifically, the control processing unit 113 controls the first ATC 110 and the first AFC 111, and the second ATC 118 and the second AFC 119, respectively, so that the first and second light sources 101 and 120 each have continuous light at each predetermined frequency. The light is emitted and the continuous light is incident on the reference optical fiber 117 so as to face each other. The continuous light from the first light source 101 and the continuous light from the second light source 120 cause a stimulated Brillouin scattering phenomenon in the reference optical fiber 117, and the light related to the stimulated Brillouin scattering phenomenon is emitted from the reference optical fiber 117. The light enters the strain and temperature detector 114 via the circulator 112.

  The strain and temperature detector 114 receives the light related to the stimulated Brillouin scattering phenomenon, detects the light intensity of the received light related to the stimulated Brillouin scattering phenomenon, and notifies the control processing unit 113 of the detected light intensity. . In the control processing unit 113, the relationship between the frequency difference between the first and second lights causing the stimulated Brillouin scattering phenomenon and the light intensity of the light related to the stimulated Brillouin scattering phenomenon in the reference optical fiber 117 is stored in advance in the storage unit. Has been. Upon receiving this notification, the control processing unit 113 responds to the predetermined frequency difference fa to be set for each light emitted by the first and second light emitting elements in the first and second light sources 101 and 120 by the frequency setting unit. The first AFC 111 and the second AFC 119 are controlled so that the reference light intensity Pa to be obtained is obtained from the above relationship, and the measured light intensity Pd detected by the strain and temperature detector 114 matches the reference light intensity Pa. As a result, the frequency difference between the lights emitted from the first and second light emitting elements in the first and second light sources 101 and 120 is adjusted to a predetermined frequency difference fa to be set. In the present embodiment, the light intensity Pd is given by a voltage value photoelectrically converted by the light receiving element, and the reference light intensity Pa is a voltage value corresponding to the reference light intensity Pa.

  Here, in the reference optical fiber 117, the relationship between the frequency difference between the first and second lights causing the stimulated Brillouin scattering phenomenon and the light intensity of the light related to the stimulated Brillouin scattering phenomenon generally has temperature dependence. Yes. In this embodiment, at the time of adjustment, the control processing unit 113 detects the temperature of the reference optical fiber 117 by the temperature detection unit 116 and corrects the above-described relationship in the reference optical fiber 117 according to the detected temperature. Yes. For this reason, adjustment can be executed with higher accuracy.

  By operating in this way, each frequency of each continuous light emitted from the first and second light sources 101 and 120 is adjusted. Such adjustment may be performed every time the frequency is changed for the sweep when obtaining the Brillouin spectrum from the viewpoint of further improving the measurement accuracy, or from the viewpoint of shortening the measurement time. The strain and temperature may be executed every measurement, every time a predetermined period elapses, or even when the monitoring apparatus body 3 is activated.

The comparison calculation means 22 is connected to the detection measurement means 20 and the comparison measurement means 21, respectively. Specifically, the distortion and temperature detector 114 of the detection measurement means 20 and the distortion and temperature detection meter of the comparison measurement means 21 are connected. 114, respectively, and the Brillouin frequency shift amount and the Rayleigh frequency shift amount derived by the CPU of each strain and temperature detector 114, and the CO _{2 in} the longitudinal direction around the sensing unit 14 of the sensing cable 2 The concentration distribution and temperature distribution are derived. Specifically, the comparison calculation unit 22 obtains the pressure distribution and temperature distribution in the longitudinal direction of the portion corresponding to the sensing unit 14 in the detection optical fiber 9 obtained by the detection measurement unit 20 and the comparison measurement unit 21. Further, based on the comparison with the longitudinal pressure distribution and the temperature distribution of the portion corresponding to the sensing portion 14 in the comparison optical fiber 12, the sensing cable 2 periphery (specifically, the sensing portion 14 periphery) in the longitudinal direction. The concentration distribution and temperature distribution of CO ₂ are derived.

  The heating means 23 is a means for heating the liquid sealed in the pressure pipe 6 of the detection cable 2 as described above, and performs a heating operation based on a command signal from the control means 24.

The control unit 24 is connected to each comparison calculation unit 22 and controls each unit including the detection measurement unit 20, the comparison measurement unit 21, the comparison calculation unit 22, and the heating unit 23. Further, the control unit 24 receives the CO ₂ concentration distribution and temperature distribution data in the longitudinal direction around the sensing unit 14 of each detection cable 2 derived by the comparison calculation unit 22, and receives various results and data on the monitor 26. Processing for displaying the information is performed, and the processed data is output to the monitor 26.

In the monitoring system 1 configured as described above, a number of detection cables 2 necessary for monitoring are arranged in a monitoring coping area where CO ₂ is monitored, and these arranged detection cables 2 are arranged in the monitoring apparatus main body 3. Connect to. Specifically, as shown in FIG. 1, the monitoring device main body 3 is arranged at a predetermined position on the ground, and the plurality of detection cables 2 pass through the storage layers R in which CO ₂ is stored, respectively. Arranged at intervals. At this time, each of the detection cables 2 is located on the ground and connected to the connection part c of the monitoring apparatus main body 3, and the sensing part 14 on the distal end side is located in an area where the CO _{2 is} to be monitored (monitoring target area). Is arranged. In the present embodiment, the monitoring target region is a deep underground saltwater layer (reservoir) R in which CO ₂ is stored, a cap lock CR above it, and its peripheral region.

  Note that the length of the sensing unit 14 in the longitudinal direction of the sensing cable 2 is set in accordance with the size of the monitoring target area where the sensing cable 2 is disposed. In the present embodiment, the sensing unit 14 of the detection cable 2 is disposed along the vertical direction, but the present invention is not limited to this, and the sensing unit 14 may be disposed along the horizontal direction or the inclination direction. Further, the sensing units 14 do not need to be arranged in a straight line, may be curved, and all the sensing units 14 need not be arranged in parallel or substantially in parallel.

Next, the CO ₂ monitoring operation in the ground using the monitoring system 1 installed in this way will be described. FIG. 8 is a flowchart for explaining the monitoring operation of the CO ₂ stored underground by the monitoring system 1 according to the present embodiment. In the monitoring apparatus main body 3, a plurality of units each having the detection measuring means 20, the comparison measuring means 21, the comparison calculating means 22 and the heating means 23 as one unit perform the same operation. When describing the above, only one unit will be described.

First, before the monitoring system 1 is installed and monitoring of CO _{2 in} the ground is started, the strain and temperature detectors 114 of the measuring means 20 for detection and the measuring means 21 for comparison are detected by the optical fiber 9 for detection or the comparison. Brillouin spectrum peak frequency (reference peak frequency) and Rayleigh spectrum (reference Rayleigh spectrum) at each measured position when the optical fiber 12 is in the reference state (in this embodiment, the state immediately after the detection cable 2 is installed in the ground) ) And store in memory.

  Specifically, in step S1, the distortion and temperature detector 114 of the detection measurement unit 20 (or the comparison measurement unit 21) estimates the Brillouin frequency shift amount Δνb, and the frequency for measuring the Brillouin frequency shift amount Δνb. The control processing unit 113 is instructed to emit continuous light from the first and second light sources 101 and 120 within the determined sweep range. The estimation of the Brillouin frequency shift amount Δνb here is performed based on, for example, the predicted maximum temperature change amount and maximum strain change amount. Since the frequency sweep range for measuring the Brillouin frequency shift amount is narrow, the frequency sweep range can be easily estimated.

  Next, in step S <b> 2, the distortion and temperature detector 114 of the detection measurement unit 20 (or the comparison measurement unit 21) measures the reference peak frequency of the Brillouin spectrum. For example, the reference peak frequency of the Brillouin spectrum is obtained by the following process.

  First, the control processing unit 113 controls the first ATC 110 and the first AFC 111 and the second ATC 118 and the second AFC 119 to cause the first and second light sources 101 and 120 to emit respective continuous lights at respective predetermined frequencies. The continuous light emitted from the first light source 101 is incident on the optical pulse generation unit 103 via the optical coupler 102, and the continuous light emitted from the second light source 120 is incident on the optical switch 122 via the optical coupler 121. Is done.

  Next, the control processing unit 113 controls the optical pulse generation unit 103 to generate predetermined pump light (sub optical pulse and main optical pulse). More specifically, the control processing unit 113 generates pump light by operating the optical pulse generation unit 103 as follows, for example.

  FIG. 9 is a diagram for explaining the configuration and operation of the optical pulse generator 103 shown in FIG. FIG. 10 is a diagram for explaining the configuration of the pump light (sub-light pulse and main light pulse) and the matched filter. FIG. 10A shows the configuration of the pump light, and FIG. It is a figure which shows a matched filter.

  For example, as illustrated in FIG. 9, the optical pulse generation unit 103 includes an LN intensity modulator 201 that modulates the light intensity of incident light, and a DC power source that configures a first drive circuit for driving the LN intensity modulator 201. 202, a multiplier 203 and a timing pulse generator 204, an LN phase modulator 211 that modulates the phase of incident light, a DC power supply 212 that constitutes a second drive circuit for driving the LN phase modulator 211, and a multiplier 213, a pseudorandom number generator 214, an erbium-doped fiber amplifier (EDFA) 221, an LN intensity modulator 231 that modulates the light intensity of incident light, and a third drive circuit for driving the LN intensity modulator 231. A DC power supply 232, a multiplier 233, and a timing pulse generator 234 are configured.

  The LN phase modulator 211 is configured by, for example, forming an optical waveguide, a signal electrode, and a ground electrode on a lithium niobate substrate having an electro-optic effect, and by applying a predetermined signal between both electrodes. The apparatus modulates the phase of incident light by using the phase change accompanying the refractive index change caused by the electro-optic effect as it is.

  The LN intensity modulators 201 and 231 are devices that modulate the light intensity of incident light, for example, by configuring a Mach-Zehnder interferometer and changing a phase change accompanying a refractive index change due to an electro-optic effect to an intensity change. Note that the LN intensity modulators 201 and 231 and the LN phase modulator 211 have other electro-optic effects such as lithium tantalate, lithium niobate, and lithium tantalate intrinsic substance instead of the lithium niobate substrate. A substrate may be used.

  In the first drive circuit, the DC power supply 202 is a power supply circuit that generates a DC voltage to be applied to the signal electrode of the LN intensity modulator 201 in order to modulate the intensity, and the timing pulse generator 204 includes the LN intensity modulator 201. A pulse generation circuit that generates an operation timing pulse to operate, and a multiplier 203 multiplies the DC voltage input from the DC power supply 202 by the operation timing pulse input from the timing pulse generator 204, This is a circuit that outputs a DC voltage corresponding to the operation timing pulse to the LN intensity modulator 201.

  In the second drive circuit, the DC power supply 212 is a power supply circuit that generates a DC voltage to be applied to the signal electrode of the LN phase modulator 211 for phase modulation, and the pseudorandom number generator 214 converts the incident light into a spread spectrum system. The pseudo random number generation circuit generates a pseudo random number at an operation timing in order to operate the LN phase modulator 211 so as to perform modulation with a DC voltage input from the DC power supply 212 and a pseudo random number generator 214. Is a circuit that outputs a DC voltage corresponding to the pseudo-random number to the phase modulator 211.

  The EDFA 221 is an optical component that includes an optical fiber doped with erbium, and amplifies and emits incident light. The EDFA 221 amplifies incident light at a predetermined amplification factor set in advance so as to obtain a light intensity suitable for detecting distortion and temperature in the detection optical fiber 9 or the comparison optical fiber 12. As a result, when a loss occurs during propagation from the first light source 101 to the detection optical fiber 9 or the comparison optical fiber 12, this loss is also compensated, and measurement in a predetermined measurement range becomes possible. .

  In the third drive circuit, the DC power supply 232 is a power supply circuit that generates a DC voltage to be applied to the signal electrode of the LN intensity modulator 231 so as to intensity-modulate the LN intensity modulator 231 so as to perform on / off control. The timing pulse generator 234 is a pulse generation circuit that generates an operation timing pulse in order to operate the LN intensity modulator 231. The multiplier 233 receives the DC voltage input from the DC power source 232 and the timing pulse generator 234. This circuit multiplies the input operation timing pulse and outputs a DC voltage corresponding to the operation timing pulse to the LN intensity modulator 231.

  By operating such an optical pulse generation unit 103, for example, pump light having a configuration shown in FIG. 10A can be generated.

  The pump light shown in FIG. 10A is unmodulated with the main light pulse encoded by the spread spectrum method, and precedes in time without overlapping (without overlapping) the main light pulse. And sub-light pulses. The main optical pulse is divided into a plurality of cells with a predetermined time width (cell width), and in the present embodiment, each cell is modulated (encoded) with an M-sequence binary code. The cell width is set according to the desired spatial resolution, and the pulse width of the main light pulse is set according to the desired measurement distance. Further, the sub light pulse has a pulse width capable of completely raising the acoustic phonon, and in the example shown in FIG. 10A, the light intensity is the same as the light intensity of the main light pulse.

  In the example shown in FIG. 10A, the sub light pulse and the main light pulse are continuous in time, but may be separated in time. In the case of temporal separation, it is preferable to set the time interval at which the main light pulse acts on the acoustic phonon before the acoustic phonon raised by the sub light pulse disappears. Usually, since the acoustic phonon has a lifetime of about 5 ns, the time interval between the sub light pulse and the main light pulse is preferably within about 5 ns.

  In order to generate the pump light having the configuration shown in FIG. 10A, first, in FIG. 9, the continuous light L1 emitted from the first light source 101 is LN intensity of the optical pulse generation unit 103 via the optical coupler 102. The light enters the modulator 201.

In the light pulse generation unit 103, at the generation timing of the pump light, the pulse width (D _{sub + D)} operation timing pulse is a timing pulse generator which corresponds to the pulse width D of the pulse width D _sub and main light pulse of the sub light pulse 204 is output to the multiplier 203, multiplied by the DC voltage input from the DC power supply 202, and a DC voltage having a pulse width (D _sub + D) is applied to the signal electrode of the LN intensity modulator 201. As a result, the LN intensity modulator 201 is turned on for a time width (D _sub + D) corresponding to the pulse width (D _sub + D) according to the operation timing pulse, and the continuous light L1 is turned on. Thus, an optical pulse L2 having a pulse width (D _sub + D) is emitted.

  Then, the optical pulse generator 103 multiplies the pseudo random number from the pseudo random number generator 214 at the time timing of the cell width during the time width D corresponding to the pulse width D of the main optical pulse at the generation timing of the main optical pulse. Sequentially output to 213, multiplied by the DC voltage input from the DC power supply 212, the DC voltage modulated by the M-sequence binary code is LN at the time timing of the cell width, with the time width D from the generation timing of the main optical pulse. The signal is sequentially applied to the signal electrodes of the phase modulator 211.

  That is, the DC voltage modulated by the M-sequence binary code is emitted from the LN phase modulator 211 when the DC voltage corresponding to the case where the M-sequence binary code is “+” is supplied to the LN phase modulator 211. The phase of the light and the phase of the light emitted from the LN phase modulator 211 when the DC voltage corresponding to the case where the M-sequence binary code is “−” are supplied to the LN phase modulator 211 are 180 degrees different from each other. It is a correct voltage value. Thus, the optical pulse L2 is an optical pulse composed of an unmodulated portion (corresponding to the sub optical pulse) and a portion modulated by the M-sequence binary code (corresponding to the main optical pulse) by the LN phase modulator 211. Injected as L3.

  In the EDFA 221, the light pulse L3 is amplified until it reaches a predetermined light intensity, and is emitted as the light pulse L4.

Further, in the optical pulse generation unit 103, an operation timing pulse having a pulse width (D _sub + D) corresponding to the pulse width D _sub of the sub optical pulse and the pulse width D of the main optical pulse is determined according to the generation timing of the pump light. The pulse generator 234 outputs to the multiplier 233 and is multiplied by the DC voltage input from the DC power source 232, and a DC voltage having a pulse width (D _sub + D) is applied to the signal electrode of the LN intensity modulator 231. As a result, the optical pulse L4 is a sub-optical pulse that has an LN intensity modulator 231 to remove noise such as spontaneous emission light (ASE) associated with the optical pulse L4 by the EDFA 221 and has a pulse width D _sub and is not modulated. And pump light L5 having the pulse width D and the main light pulse encoded by the spread spectrum method.

  Then, the control processing unit 113 turns on the optical switch 104 and the optical switch 122 according to the generation timing of the pump light (sub optical pulse, main optical pulse, and optical pulse L4) in the optical pulse generation unit 103. The control processing unit 113 notifies the distortion and temperature detector 114 of the generation timing of the pump light (sub light pulse and main light pulse).

  When the optical switch 104 is turned on, the pump light (sub optical pulse and main optical pulse) is incident on the optical coupler 105 and branched into two. One of the branched pump lights is incident on the light intensity / polarization adjusting unit 106, the light intensity is adjusted by the light intensity / polarization adjusting unit 106, the polarization direction is adjusted randomly (randomly), and the optical circulator. The light is incident on one end of the detection optical fiber 9 (or the comparison optical fiber 12) in the detection cable 2 through the optical coupler 107, the optical coupler 108 and the optical connector 109. On the other hand, the other sub light pulse and main light pulse branched by the optical coupler 105 are incident on the strain and temperature detector 114.

  The strain and temperature detector 114 measures the spectrum of the pump light (sub light pulse and main light pulse) and notifies the control processing unit 113 of the frequency and light intensity of the pump light. Upon receiving this notification, the control processing unit 113 controls the first ATC 110, the first AFC 111, and the light intensity / polarization adjustment unit 106 as necessary so that an optimum measurement result can be obtained.

  On the other hand, when the optical switch 122 is turned on, continuous light (probe light) is incident on the optical coupler 123 and branched into two. One of the branched probe lights (continuous light) is incident on the light intensity adjustment unit 124, the light intensity of which is adjusted by the light intensity adjustment unit 124, and is detected in the detection cable 2 via the optical coupler 108 and the optical connector 109. The light is incident on one end of the detection optical fiber 9 (or the comparison optical fiber 12). On the other hand, the other probe light (continuous light) branched by the optical coupler 123 enters the strain and temperature detector 114.

  The strain and temperature detector 114 measures the spectrum of the probe light (continuous light), and notifies the control processing unit 113 of the frequency and light intensity of the probe light. Upon receiving this notification, the control processing unit 113 controls the second ATC 118, the second AFC 119, and the light intensity adjustment unit 124 as necessary so as to obtain an optimum measurement result.

  In the Brillouin spectrum time domain analysis, the pump light (sub light pulse and main light pulse) incident on one end of the detection optical fiber 9 (or the comparison optical fiber 12) in the detection cable 2 is detected by the detection optical fiber 9 ( Alternatively, a probe that is incident from one end of the comparison optical fiber 12), reflects off the other end of the detection optical fiber 9 (or comparison optical fiber 12), and propagates through the detection optical fiber 9 (or comparison optical fiber 12). It propagates from one end of the detection optical fiber 9 (or the comparison optical fiber 12) to the other end while causing light (continuous light) and stimulated Brillouin scattering. On / off timings of the optical switch 104 and the optical switch 122 are adjusted by the control processing unit 113 based on the interaction between the pump light and the probe light.

  When the Brillouin spectrum time domain analysis (BOTDA) is performed, the 1 × 2 optical switch 129 is switched so that light incident from the input terminal is incident on the strain and temperature detector 114. Therefore, the light related to the stimulated Brillouin scattering phenomenon is emitted from one end of the detection optical fiber 9 (or the comparison optical fiber 12), and passes through the optical connector 109, the optical coupler 108, the optical circulator 107, and the 1 × 2 optical switch 129. And enters the strain and temperature detector 114.

In the strain and temperature detector 114, the light related to the stimulated Brillouin scattering phenomenon is extracted by direct detection as described above, converted into an electric signal by the light receiving element, and filtered by the matched filter. For example, as shown in FIG. 10B, the matched filter is a phase modulation pattern (P ₁ P ₂ P ₃ ... Phase-modulated by an M-sequence binary code by the LN phase modulator 211 of the optical pulse generation unit 103. P _n-1 P _n ) is a filter of an antiphase modulation pattern (P _n P _n-1 ... P ₃ P ₂ P ₁ ) obtained by temporally inverting the P _n-1 P _n ).

  For example, when each cell of the main optical pulse is modulated with an M-sequence binary code with a phase modulation pattern of “+ − ++ − +... + −”, The matched filter temporally converts this phase modulation pattern. The reverse pattern of “− +... + − ++ − +” is inverted. By using such a matched filter, it is possible to accurately detect light related to the stimulated Brillouin scattering phenomenon caused by the spread spectrum encoded main light pulse. The strain and temperature detector 114 performs time domain analysis on the received light related to the stimulated Brillouin scattering phenomenon based on the generation timing notified from the control processing unit 113, and detects the detection optical fiber 9 (or the comparison optical fiber 12). ) To measure the light intensity distribution of the light related to the stimulated Brillouin scattering phenomenon in the longitudinal direction.

  Here, the degree of interaction between pump light (sub light pulse and main light pulse) and probe light (continuous light) related to the stimulated Brillouin scattering phenomenon depends on the relative relationship between the polarization planes of these lights. In the detection measuring means 20 (or the comparison measuring means 21) according to the present embodiment, the light intensity / polarization adjusting unit 106 randomly changes the polarization plane of the pump light for each measurement, so the measurement is executed a plurality of times. By adopting the average value, this dependence can be substantially eliminated. For this reason, the light intensity distribution of the light related to the stimulated Brillouin scattering phenomenon can be obtained with high accuracy.

  The light intensity distribution of the light related to the stimulated Brillouin scattering phenomenon in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12) is, for example, probe light (continuous light) emitted from the second light source 120. Are swept in a predetermined frequency range at predetermined frequency intervals under the control of the control processing unit 113, so that each frequency is measured with high accuracy and high spatial resolution. As a result, the Brillouin spectrum in each region in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12) can be obtained with high accuracy and high spatial resolution.

  As described above, the distortion and temperature detector 114 of the detection measurement unit 20 (or the comparison measurement unit 21) measures the light intensity distribution related to the stimulated Brillouin scattering phenomenon, and detects the detection light from the measurement result. The Brillouin spectrum of each region in the longitudinal direction of the fiber 9 (or the comparison optical fiber 12) is obtained, and the reference peak frequency is derived from each Brillouin spectrum. In the present embodiment, in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12), for example, the reference peak frequency of the Brillouin spectrum at the actually measured positions set at intervals of 5 cm is measured.

  The reference peak frequencies of the Brillouin spectrum at the above-described actually measured positions (measured positions arranged at intervals of 5 cm in this embodiment) are stored in the memory of the strain and temperature detector 114, respectively.

  Next, in step S3, the strain and temperature detector 114 measures the reference Rayleigh spectrum. For example, a reference Rayleigh spectrum is obtained by the following process.

  First, the control processing unit 113 controls the first ATC 110 and the first AFC 111 to cause the first light source 101 to emit continuous light at a predetermined frequency. The continuous light emitted from the first light source 101 is incident on the optical pulse generator 103 and the 1 × 2 optical switch 131 via the optical coupler 102, and the 1 × 2 optical switch 131 is emitted from the first light source 101. Continuous light is output to the optical coupler 130. Note that the optical switch 122 is turned off during the measurement of the reference Rayleigh spectrum.

  Next, the control processing unit 113 controls the light pulse generation unit 103 to generate pulsed light for using the Rayleigh scattering phenomenon. More specifically, the control processing unit 113 generates pulsed light by operating the optical pulse generation unit 103 as follows, for example.

  11 is a diagram illustrating an example of the pulsed light emitted from the optical pulse generation unit 103 illustrated in FIG. 5, FIG. 11A illustrates the wavelength of the pulsed light, and FIG. 11B illustrates the pulsed light. The waveform is shown. The pulsed light shown in FIG. 11 (B) is a rectangular wave of a predetermined level, and as shown in FIG. 11 (A), the cycle is sequentially increased by a predetermined frequency for every predetermined number of pulses. In FIG. 11A, for ease of illustration, the frequency is schematically shown so as to increase linearly, but strictly speaking, the frequency is increased every few pulses, and the pulse The frequency of light is increased in steps. Further, when the averaging described later is not performed, that is, when Rayleigh backscattered light is measured with one pulse, the frequency may be increased for each pulse.

  The pulsed light is not particularly limited to this example, and various forms of light can be used as long as the Rayleigh scattering phenomenon can be used. In addition, various methods such as modulation (encoding) using an M-sequence binary code may be applied to light using the Rayleigh scattering phenomenon, similarly to the light used for the stimulated Brillouin scattering phenomenon.

  In order to generate the pulsed light shown in FIG. 11, the continuous light emitted from the first light source 101 is incident on the LN intensity modulator 201 of the optical pulse generation unit 103 via the optical coupler 102. In the optical pulse generation unit 103, an operation timing pulse corresponding to the pulse width of the pulsed light is output from the timing pulse generator 204 to the multiplier 203 at the generation timing of the pulsed light, and is multiplied by the DC voltage input from the DC power supply 202. Then, a DC voltage having a pulse width is applied to the signal electrode of the LN intensity modulator 201. Accordingly, the LN intensity modulator 201 is turned on for a time width corresponding to the pulse width in accordance with the operation timing pulse, and the continuous light is emitted as an optical pulse having the pulse width shown in FIG. Is done. Thereafter, the pulsed light enters the EDFA 221 via the LN phase modulator 211, is amplified until the optical pulse reaches a predetermined light intensity, and is emitted to the optical switch 104 via the LN intensity modulator 231.

  Then, the control processing unit 113 turns on the optical switch 104 according to the generation timing of the pulsed light in the optical pulse generation unit 103 and notifies the generation timing of the pulsed light to the strain and temperature detector 114.

  When the optical switch 104 is turned on, the pulsed light is incident on the optical coupler 105 and branched into two. One of the branched pulse lights is incident on the light intensity / polarization adjustment unit 106, the light intensity is adjusted by the light intensity / polarization adjustment unit 106, and the polarization direction thereof is adjusted randomly (randomly). The light is incident on one end of the detection optical fiber 9 (or the comparison optical fiber 12) via the optical circulator 107, the optical coupler 108, and the optical connector 109. On the other hand, the other pulsed light branched by the optical coupler 105 enters the strain and temperature detector 114.

  The strain and temperature detector 114 measures the spectrum of the pulsed light and notifies the control processing unit 113 of the frequency and light intensity of the pulsed light. Upon receiving this notification, the control processing unit 113 controls the first ATC 110, the first AFC 111, and the light intensity / polarization adjustment unit 106 as necessary so that an optimum measurement result can be obtained.

  The pulsed light incident on one end of the detection optical fiber 9 (or the comparison optical fiber 12) in the detection cable 2 is scattered in the detection optical fiber 9 (or the comparison optical fiber 12) to cause a Rayleigh scattering phenomenon. The light related to the Rayleigh scattering phenomenon is emitted from one end of the detection optical fiber 9 (or the comparison optical fiber 12), and the optical connector 109, the optical coupler 108, the optical circulator 107, and the 1 × 2 optical switch 129. Through the optical coupler 130. As a result, the two lights mixed by the optical coupler 130 enter the strain and temperature detector 114.

  As described above, the first light source 101 functions as a wavelength variable light source, changes the wavelength of the pulsed light with time, and the optical pulse generator 103 functions as a light intensity modulator, an optical amplifier, and a light intensity modulator. The light intensity / polarization adjusting unit 106 functions as a high-speed polarization scrambler and gives a random polarization plane to each pulsed light. The optical coupler 130 mixes the continuous wave from the first light source 101 and the Rayleigh backscattered light from the detection optical fiber 9 (or the comparison optical fiber 12). Receives homodyne light.

  At this time, since a random polarization plane is given to each pulsed light by the light intensity / polarization adjusting unit 106 for each measurement, the strain and temperature detector 114 adds the Rayleigh backscattered light corresponding to the change in wavelength and averages it. Therefore, smooth Rayleigh backscattered light can be obtained, and loss at each distance can be converted from the level of Rayleigh backscattered light.

  The distribution of the light intensity of the light related to the Rayleigh scattering phenomenon in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12) is controlled within the predetermined frequency range by controlling the frequency of the pulsed light by the control processing unit 113. By sweeping with, measurement is performed with high accuracy and high spatial resolution at each frequency. As a result, the Rayleigh spectrum in each region in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12) can be obtained with high accuracy and high spatial resolution.

  As described above, the distortion and temperature detector 114 of the detection measurement unit 20 (or the comparison measurement unit 21) measures the Rayleigh spectrum. In this embodiment, in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12), for example, reference Rayleigh spectra at actually measured positions set at intervals of 5 cm are measured. In the measurement of the Rayleigh spectrum, the frequency sweep range is preferably set as wide as possible within the range allowed by the memory capacity for storing the obtained data (Rayleigh spectrum or the like).

  The reference Rayleigh spectrum at each actually measured position thus measured is stored in the memory of each strain and temperature detector 114, respectively.

As described above, the reference peak frequency and the reference Rayleigh at each actual measurement position of the detection optical fiber 9 (or comparison optical fiber 12) obtained from the detection optical fiber 9 (or comparison optical fiber 12) in the reference state. After each spectrum is stored in memory, CO ₂ monitoring is started.

This monitoring of CO ₂ is performed as follows. In the monitoring system 1, by detecting the concentration and temperature of the CO ₂ or the like in the reservoir layer R, whether at the time of press-fitting to the reservoir R of the CO ₂ CO ₂ is pressed into the reservoir layer R, the reservoir state of CO ₂ which is pressed into the layer R (stable whether etc.), the amount of CO ₂ in the reservoir R, mainly to monitor the leakage of CO _2, etc. from the reservoir R, the CO ₂ After the injection into the reservoir R is completed, the state of CO ₂ in the reservoir R, the leakage of CO ₂ from the reservoir R, and the like are mainly monitored. In addition, by detecting the presence or concentration of CO ₂ in the peripheral region of the reservoir R, it is monitored whether the CO ₂ stored in the reservoir R has leaked from the reservoir R.

Specifically, monitoring of CO ₂ is performed as follows. In the sensing part 14 of the detection cable 2 located in the reservoir R and the peripheral region thereof, the substance (this book) in which CO ₂ or CO ₂ existing around the detection cable 2 (sensing part 14) is dissolved through the communication part 14a (this book) In the embodiment, the salt water in which CO ₂ is dissolved freely enters and leaves the cable sheath 7. When CO ₂ entering the cable sheath 7 passes through the gate member 11 of the sensor fiber portion 4 and contacts the reaction member 10, the reaction member 10 absorbs this CO ₂ and changes its volume according to its concentration. Arise. Thus, the sensing optical fiber 9 is the pressure corresponding to the concentration of CO ₂ from the reaction member 10 is added. Further, since the reaction member 10 is made of a material that transmits the heat of the absorbed CO _{2 to} the detection optical fiber 9, the heat of the CO ₂ around the sensing unit 14 is applied to the detection optical fiber 9.

On the other hand, in the comparison fiber portion 5, since the comparison optical fiber 12 is surrounded by the metal tube 13, even if the concentration or temperature of CO ₂ around the detection cable 2 fluctuates, the reaction member 10 from the reaction member 10 is caused. The state around the comparison optical fiber 12 is maintained in a predetermined state without any pressure or heat being transmitted.

Therefore, each measuring means 20 and 21 measures the distortion and temperature of the corresponding portions in the longitudinal direction of the detection optical fiber 9 and the comparison optical fiber 12, respectively, and the comparison calculation means 22 measures the detection optical fiber 9. And the comparison optical fiber 12 with respect to each other at positions corresponding to each other (each measured position), the concentration and temperature of CO ₂ around each position are derived. By continuously (or periodically) measuring the concentration and the temperature, the CO ₂ concentration change and temperature change in the reservoir R and its peripheral region are monitored.

In the sensor fiber portion 4 of the detection cable 2 of the present embodiment, since the reaction member 10 is arranged so as to be continuous in the longitudinal direction of the detection optical fiber 9, the longitudinal direction of the detection cable 2 is determined. The concentration distribution and temperature distribution of CO ₂ around the sensing unit 14 in FIG.

  Specifically, the strain and temperature at each measured position in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12) are obtained as follows.

  First, the distortion and temperature detector 114 of the detection measurement means 20 (or the comparison measurement means 21) is switched to the Brillouin measurement mode. Specifically, in step S4, the strain and temperature detector 114 estimates the Brillouin frequency shift amount Δνb and determines the frequency sweep range for measuring the Brillouin frequency shift amount Δνb, as in step S1. The control processing unit 113 is instructed to emit continuous light from the first and second light sources 101 and 120 within the sweep range.

  Next, in step S5, the strain and temperature detector 114 measures the peak frequency of the Brillouin spectrum at each actual measurement position of the detection optical fiber 9 (or the comparison optical fiber 12), as in step S2.

  In step S6, the strain and temperature detector 114 extracts the reference peak frequencies stored in the memory, and obtains the reference peak frequencies from the monitoring detection optical fiber 9 (or the comparison optical fiber 12). The correction amount used when correcting the peak frequency measured from the detection optical fiber 9 (or the comparison optical fiber 12) in the monitoring state is derived from the measured peak frequency. This correction amount is derived, for example, by the following processing. 12A and 12B are diagrams illustrating an example of a method for deriving the correction amount.

  First, the strain and temperature detector 114 divides the detection optical fiber 9 (or the comparison optical fiber 12) in the reference state into a plurality of regions in the longitudinal direction, and sets one as the reference region rz. A correction region sz having a length corresponding to the reference region rz is set in a part of the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12) in the monitoring state. The strain and temperature detector 114 is included in the waveform (see rz in FIG. 12A) in which the values of the reference peak frequencies at the respective actual measurement positions included in the reference region rz are arranged in the longitudinal direction and the correction region sz. A cross-correlation coefficient is calculated with a waveform (see sz in FIG. 12A) in which peak frequency values at each actually measured position are arranged in the longitudinal direction. The strain and temperature detector 114 repeatedly calculates the cross-correlation coefficient while moving the correction region sz along the longitudinal direction at predetermined intervals (sz1, sz2, sz3,... In FIG. 12A), and the result Is plotted (see FIG. 12B). The movement length (offset amount) that maximizes the cross-correlation coefficient is the correction amount.

  As shown in FIG. 13, when the peak frequencies of the Brillouin spectrum at each measured position in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12) are arranged in order in the longitudinal direction, Due to the residual strain (initial residual strain) in the optical fiber 9 (or the comparison optical fiber 12) or the like, the detection optical fiber 9 (or the comparison optical fiber 12) has a unique waveform, and the detection optical fiber 9 ( Alternatively, it is utilized that the characteristics of this waveform are not lost even by expansion and contraction of the comparison optical fiber 12). Here, FIG. 13 is a diagram illustrating an example of the peak frequency of the Brillouin spectrum in each region (measurement position) in the longitudinal direction in the detection optical fiber in which a different type fiber is connected in the middle.

  Note that the method of deriving the correction amount is not limited to the method of deriving using the reference region rz and the correction region sz having the same range in the longitudinal direction as described above. For example, the range in the longitudinal direction of the correction region may be made larger or smaller than the reference region rz based on the expansion and contraction of the detection optical fiber 9 (or the comparison optical fiber 12). Thereby, it becomes possible to measure the Brillouin frequency shift amount and the Rayleigh frequency shift amount with higher accuracy.

  The strain and temperature detector 114 repeats the derivation of the correction amount with the plurality of regions obtained by dividing the detection optical fiber 9 (or the comparison optical fiber 12) in the reference state in the longitudinal direction as reference regions rz. . Thereby, the correction amount with respect to all the actual measurement positions of the detection optical fiber 9 (or the comparison optical fiber 12) is derived.

  In the present embodiment, each of the parts included in the part corresponding to the sensing unit 14 of the detection optical fiber 9 (or the comparison optical fiber 12) that needs to derive the Brillouin frequency shift amount Δνb and the Rayleigh frequency shift amount Δνr. Only the correction amount for the actual measurement position is derived, and the correction amount for each actual measurement position included in the part corresponding to the non-sensing unit 15 that does not require the derivation of the Brillouin frequency shift amount Δνb and the Rayleigh frequency shift amount Δνr is not derived. May be. In this way, the number of actually measured positions from which the correction amount is derived can be limited, and the time required for the arithmetic processing can be shortened.

  Next, in step S7, the strain and temperature detector 114 estimates the peak frequency at the measurement desired position corresponding to each actual measurement value from the peak frequency obtained from each actual measurement value. For example, the peak frequency at the measurement desired position is obtained by the following processing.

  The strain and temperature detector 114 derives a desired measurement position corresponding to the actual measurement position from each actual measurement position based on the correction amount derived for each reference region as described above. On the other hand, the strain and temperature detectors 114 are adjacent to each other so that the peak frequency values obtained discretely in the longitudinal direction (in this embodiment, at intervals of 5 cm in the longitudinal direction) are continuous in the longitudinal direction. Interpolate between the measured values (peak frequency) of the matching actual measurement positions. In the present embodiment, the above-described interpolation is performed by the B-spline interpolation method. However, the present invention is not limited to this, and another interpolation method, a least square method, or the like may be performed.

  The strain and temperature detector 114 estimates the peak frequency obtained from the Brillouin backscattered light from the desired measurement position based on each desired measurement position and the interpolated value thus obtained.

  Next, in step S8, the strain and temperature detector 114 receives the reference peak frequency at each actual measurement position of the detection optical fiber 9 (or the comparison optical fiber 12) in the reference state stored in the memory, and The Brillouin frequency shift amount Δνb is derived (measured) from the difference from the peak frequency at the measurement desired position corresponding to each measured position estimated by the processing.

  When the Brillouin frequency shift amount Δνb is derived in this way, the distortion and temperature detector 114 of the detection measurement unit 20 (or the comparison measurement unit 21) is changed from the Brillouin measurement mode to the Rayleigh measurement mode.

  First, in step S9, the strain and temperature detector 114 estimates the Rayleigh frequency shift amount Δνr from the Brillouin frequency shift amount Δνb obtained by the above processing, and in step S10, Rayleigh backscattering from the estimated Rayleigh frequency shift amount Δνr. The sweep range of the frequency of the pulsed light for measuring light is determined.

Here, the Brillouin frequency shift amount Δνb and the Rayleigh frequency shift amount Δνr are expressed by the following equations, where Δε is the strain change amount and ΔT is the temperature change amount. In the following ^{formulas, B11 ≒ 0.05 × 10 -3 GHz} / με, B12 ≒ 1.07 × 10 -3 GHz / ℃, R11 ≒ -0.15GHz / με, it is R12 ≒ -1.25GHz / ℃.

Δνb = B11 × Δε + B12 × ΔT (13)
Δνr = R11 × Δε + R12 × ΔT (14)
Comparing the above equations, it can be seen that the sensitivity of the Rayleigh frequency shift amount Δνr is much higher than the Brillouin frequency shift amount Δνb. This is very advantageous for improving the measurement accuracy, but determines the frequency sweep range for measuring the Rayleigh frequency shift amount Δνr as well as the frequency sweep range for measuring the Brillouin frequency shift amount Δνb. In this case, the frequency sweep range for measuring the Rayleigh frequency shift amount Δνr becomes very wide, and the measurement takes a long time.

  For this reason, the Rayleigh frequency shift amount Δνr is estimated from the already measured Brillouin frequency shift amount Δνb. For example, when a Brillouin frequency shift amount Δνb = 300 MHz is obtained by measurement, assuming that all changes are due to the influence of temperature, Δε = 0, and ΔT = 300 ° C. is obtained from Equation 13. Substituting this ΔT = 300 ° C. into Equation 14 yields Δνr = −375 GHz.

  Next, assuming that all changes are due to the influence of distortion, ΔT = 0, and Δε = 6000 με is obtained from Equation 13. Substituting this Δε = 6000 με into Equation 14, ΔΔr = −900 GHz is obtained. In this case, a range from −375 GHz to −900 GHz is determined as a frequency sweep range for measuring the Rayleigh frequency shift amount Δνr. Therefore, if the sweep is performed from the vicinity of −375 GHz to the vicinity of −900 GHz, the Rayleigh frequency shift amount Δνr can be measured in a short time. As the frequency sweep range, the two frequencies obtained as described above may be used as they are, or a predetermined measurement margin amount may be added as appropriate, or the sweep range may be set by a predetermined amount in order to shorten the measurement time. Various changes such as narrowing are possible. In this example, the lower limit of the temperature change amount is assumed to be 0 ° C. and the magnitude of the strain is assumed to be unlimited. However, the range of the temperature change amount and the strain magnitude depends on the application target of the apparatus. It may change. When an upper limit and a lower limit are assumed for the temperature change amount and an upper limit is assumed for the magnitude of distortion, the Rayleigh frequency sweep range is determined accordingly.

  Next, in step S11, the strain and temperature detector 114 measures the Rayleigh spectrum at each actual measurement position of the detection optical fiber 9 (or the comparison optical fiber 12), similarly to step S3. In step S12, the strain and temperature detector 114 estimates the Rayleigh spectrum at the measurement desired position corresponding to each measured position from the Rayleigh spectrum obtained at each measured position. For example, the Rayleigh spectrum at the measurement desired position is obtained by the following processing.

  The strain and temperature detector 114 derives a desired measurement position corresponding to the actual measurement position from each actual measurement position based on the correction amount derived for each reference region in step S6. On the other hand, the strain and temperature detectors 114 are adjacent to each other so that Rayleigh spectra obtained discretely in the longitudinal direction (in this embodiment, at intervals of 5 cm in the longitudinal direction) are continuous in the longitudinal direction. Interpolates between measured values (Rayleigh spectra) between measured positions. The strain and temperature detector 114 estimates the Rayleigh spectrum obtained from the Rayleigh backscattered light from each measurement desired position based on each measurement desired position and the interpolated value thus obtained.

  Next, in step S13, the strain and temperature detector 114 detects the reference Rayleigh spectrum at each actual measurement position stored in the memory and the Rayleigh at the measurement desired position corresponding to each actual measurement position estimated by the above processing. By calculating the correlation function coefficient with the spectrum, the Rayleigh frequency shift amount in each part in the longitudinal direction of the detection optical fiber 9 (or the comparison optical fiber 12) is obtained with high accuracy and high spatial resolution.

  FIG. 14 is a diagram showing an example of the Rayleigh frequency shift amount measured by the detection measuring means 20 and the detection optical fiber 9 shown in FIG. FIG. 14A shows the Rayleigh spectrum when there is distortion and when there is no distortion, and FIG. 14B shows the correlation coefficient between when there is distortion and when there is no distortion. As shown in FIG. 14A, the Rayleigh spectrum when there is distortion is a solid line in the figure, and the Rayleigh spectrum when there is no distortion is the broken line in the figure. 14 (B), and the offset amount Δvr of the peak of the correlation coefficient between them is the Rayleigh frequency shift amount.

  When the Rayleigh spectrum (solid line) when there is distortion is moved by this Δvr, it becomes as shown in FIG. 14C, and the Rayleigh spectrum (solid line) when there is distortion and the Rayleigh spectrum (dashed line) when there is no distortion. It is understood that the Rayleigh frequency shift amount can be obtained with high accuracy and high spatial resolution.

  Next, in step S14, the strain and temperature detector 114 determines the detection optical fiber 9 (or the comparison optical fiber 12) from the Brillouin frequency shift amount Δνb and the Rayleigh frequency shift amount Δνr obtained by the above processing. Strain and temperature at each measured position in the longitudinal direction are detected.

  That is, when the strain variation Δε and the temperature variation ΔT are solved from the above equations 13 and 14, the following is obtained. In the following formula, C11≈-12755.102 με / GHz, C12≈-10.918 × με / GHz, C21≈1530.612 ° C./GHz, and C22≈0.510 ° C./GHz.

Δε = C11 × Δνb + C12 × Δνr (15)
ΔT = C21 × Δνb + C22 × Δνr (16)
The strain and temperature detector 114 substitutes the Brillouin frequency shift amount Δνb and the Rayleigh frequency shift amount Δνr of each actual measurement position into the above formula, and each actual measurement position in the longitudinal direction of the detection optical fiber 9 or the comparison optical fiber 12. The strain change amount Δε and the temperature change amount ΔT are obtained, and the obtained strain change amount Δε and the temperature change amount ΔT are added to a predetermined reference strain and reference temperature, and finally the strain and temperature are accurately determined. Obtain with high spatial resolution.

  With the above configuration, the detection measuring means 20 (or the comparison measuring means 21) uses the Brillouin scattering phenomenon to cause a Brillouin frequency shift due to distortion and temperature generated in the detection optical fiber 9 (or the comparison optical fiber 12). As well as measuring the amount of Rayleigh frequency shift due to distortion and temperature generated in the detection optical fiber 9 (or comparison optical fiber 12) using the Rayleigh scattering phenomenon, the two frequency shift amounts are The strain and temperature generated in the detection optical fiber 9 (or the comparison optical fiber 12) can be calculated simultaneously and independently, and are generated in the detection optical fiber 9 (or the comparison optical fiber 12). Strain and temperature change can be measured simultaneously and independently with high spatial resolution. As a result, it becomes possible to detect strain and temperature with a spatial resolution of about 0.1 m and an accuracy of about ± 15 με or less.

  In addition, the detection optical fiber 9 (or the comparison optical fiber 12) is long, or the detection optical fiber 9 (or the comparison optical fiber 12) has a large temperature change and distortion change. Even if the deviation from the position is large, a correction amount related to this deviation is derived from the Brillouin backscattered light, and this correction amount can be used to accurately detect the Brillouin frequency shift amount and the Rayleigh frequency shift amount. In addition, by correcting the deviation between the measured position and the desired measurement position corresponding to the measured position using the correction amount, it is possible to reliably derive the Rayleigh frequency shift amount Δνr that is easily affected by the deviation. . That is, since the Rayleigh spectrum strongly depends on the width of the main pulse light, it is necessary to correct the measured position and the corresponding measurement desired position with an accuracy of about the width of the main pulse light (10 cm in the present embodiment). Although the correlation between the reference state and the measurement state cannot be obtained in the Rayleigh measurement, the correction based on the correction amount described above can be corrected with sufficient accuracy to perform the Rayleigh measurement.

Next, in step S15, the comparison calculation means 22 calculates the respective strains of the detection measurement means 20 and the comparison measurement means 21 and the respective region portions in the longitudinal direction of the detection optical fiber 9 derived by the temperature detector 114. Based on the comparison between the pressure distribution and the temperature distribution and the pressure distribution and the temperature distribution of each region portion in the longitudinal direction of the comparison optical fiber 12 corresponding to each region portion of the detection optical fiber 9, the detection cable 2. to derivation of the temperature distribution of the sensing portion 14 CO ₂ concentration along the longitudinal direction of the peripheral distribution and CO _2.

Specifically, the comparison optical fiber 12 is surrounded by a metal tube 13 so that pressure or heat from the reaction member 10 is not applied. Therefore, the comparison calculation means 22 compares the pressure and heat at the corresponding measured positions of the detection optical fiber 9 and the comparison optical fiber 12, and applies the pressure and heat applied to the comparison optical fiber 12 to the detection optical fiber 9. The difference between the applied pressure and heat is calculated as the pressure and heat received by the detection optical fiber 9 from the reaction member 10 in accordance with the concentration and temperature of CO _{2 at} each measured position. Comparison calculating unit 22 may store in advance in the memory or the like obtained by the relationship between the pressure sensing optical fiber 9 is subjected when contacted reaction member 10 CO ₂ concentration and this CO ₂ in the table, this Based on the table, the concentration of CO _{2 at} each measured position is calculated. In this way, the comparison calculation means 22 derives the CO ₂ concentration distribution and temperature distribution in the longitudinal direction of the detection cable 2.

Comparison calculating unit 22, in this way to derive the concentration distribution and temperature distribution of the CO _2, at step S16, it stores the density distribution and the temperature distribution of the CO ₂ in the memory, and previously the concentration distribution of CO ₂ stored If there is a temperature distribution, determines whether the variation of each is compared with the new density distribution of the derived CO ₂ and temperature distribution already concentration distribution of CO ₂ that stores and temperature distribution values. When a change is recognized by this determination, it can be determined that the state of CO ₂ stored in the reservoir R changes or that CO ₂ leaks from the reservoir R.

Next, in step S17, the control means 24 collects the results from the respective comparison calculation means 22 and stores them in a memory, and outputs an output signal to the monitor 26 in order to display the results on the monitor 26 in a predetermined manner. Output. The monitor 26 displays this on a screen or the like. If the monitoring of CO ₂ is stopped, the process ends here (step S18). If the monitoring is continued, in step S19, the control means 24 continues from the previous measurement or waits for a predetermined time interval. The heating means 23 is instructed to heat the liquid sealed in the pressure tube 6 of the detection cable 2. Thereby, the pressurizing tube 6 expands, the reaction member 10 is pressurized, and CO ₂ absorbed by the reaction member 10 is released. And it returns to step S4 and repeats this step S4 to step S17.

Thereby, the distribution (concentration distribution and temperature distribution) of CO _{2 in} the longitudinal direction around each detection cable 2 can be monitored constantly and in real time for a long time.

According to the monitoring system 1 as described above, the reaction member 10 comes into contact with CO ₂ by comparing scattered light based on the Brillouin scattering phenomenon and the Rayleigh scattering phenomenon in the detection optical fiber 9 and the comparison optical fiber 12. As a result, the pressure and heat applied to the detection optical fiber 9 can be measured easily and reliably, and CO ₂ can be detected in the detection target region where the detection cable 2 is arranged. Moreover, in the detection cable 2, the both optical fibers 9, 12 is incident pump light and the probe light, since it is detected in CO ₂ by measuring the scattered light caused by these light, pumping light and probe By keeping light incident on both optical fibers 9 and 12, CO ₂ can be detected at all times. Moreover, since the detection cable 2 using the optical fibers 9 and 12 is used as a sensor and the light (pump light and probe light) incident on the optical fibers 9 and 12 is used, the detection cable 2 is long. (For example, several hundred m to several tens of km) can be used to instantaneously measure scattered light based on the Brillouin scattering phenomenon and the Rayleigh scattering phenomenon. For example, CO ₂ in a region away from the observer such as the deep underground or the seabed. Can also be monitored in real time.

Further, in the monitoring system 1, by measuring the Brillouin frequency shift amount and the Rayleigh frequency shift amount, the strain and temperature generated in each of the optical fibers 9 and 12 using these two frequency shift amounts simultaneously and independently. Thus, the CO ₂ concentration distribution and temperature distribution in the longitudinal direction around each detection cable 2 can be measured simultaneously and independently with high spatial resolution. As a result, the CO ₂ concentration distribution and temperature distribution in the long direction around each detection cable 2 can be monitored simultaneously and independently with high spatial resolution for a long period of time constantly and in real time.

  Further, in the monitoring system 1, the detection optical fiber 9 and the comparison optical fiber 12 are long, or the temperature change and the distortion change in the optical fibers 9 and 12 are large. Even if the deviation is large, the correction amount relating to this deviation is derived from the Brillouin backscattered light, and the Brillouin frequency shift amount and the Rayleigh frequency shift amount can be accurately detected by using this correction amount. In particular, by using this correction amount, it becomes possible to reliably detect the Rayleigh frequency shift amount (Rayleigh measurement).

Since the reaction member 10 covers the detection optical fiber 9 in the circumferential direction and is in contact with CO ₂ , the volume of the reaction member 10 changes, and the heat of the contacted CO ₂ is transmitted to the detection optical fiber 9. By using the detection cable 2, it is possible to accurately monitor the CO ₂ concentration and temperature in the monitoring target region.

Since the gate member 11 collectively surrounds the detection optical fiber 9 and the reaction member 10 from the outside and is made of a material that allows permeation of CO ₂ , contact of the other substance with the reaction member 10 is suppressed. In addition, as a result of sufficiently ensuring the contact of the CO _{2 with} the reaction member 10, the detection sensitivity of CO ₂ is improved. Or, since the gate member 11 is selectively transmitted through the CO _2, even material also in contact with the CO ₂ addition of substances applying pressure and / or heat to the sensing optical fiber 9 can be used as a reaction member This increases the degree of freedom in selecting the reaction member material.

Also, in the monitor system 1, comprising a removal means re, while the reaction member 10 absorbs this by contacting the CO _2, for releasing CO ₂ absorbed by pressurized by removing means re, monitored It becomes possible to detect a change in CO ₂ over time in the region.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 15 and 16. The same reference numerals are used for the same components as those in the first embodiment, and detailed descriptions are omitted, and different configurations are described. Only the details will be described.

  The monitoring system 1 includes a detection cable 2 and a monitoring device body 3. The detection cable 2 includes a sensor fiber portion 4, a comparison fiber portion 5, a pressurizing tube 6, a cable body 57, and a slot 8, and is configured so that both ends can be connected to the connection portion c of the monitoring device body 3. The

  The cable body 37 has the sensing unit 14 at an intermediate position in the longitudinal direction. That is, the cable body 37 of the present embodiment has the non-sensing units 15 and 15 on both ends so as to sandwich the sensing unit 14.

  As shown in FIG. 15, the detection cable 2 configured in this way is arranged so that the middle sensing unit 14 passes through the monitoring target region including the reservoir R, and both ends thereof are located on the ground surface. The

  The monitoring apparatus main body 3 includes a detection measurement unit 50, a comparison measurement unit 51, a comparison calculation unit 22, a heating unit 23, and a control unit 24. Also in this embodiment, since the detection measuring means 50 and the comparison measuring means 51 have the same configuration as in the first embodiment, only the detection measuring means 50 will be described below. Description is omitted.

  The detection measurement means 50 (or the comparison measurement means 51) further includes an optical connector 126 and a 1 × 2 optical switch 125 in addition to the configuration of the detection measurement means 20 of the first embodiment. The detection measuring means 50 is optically connected at both ends of the detection optical fiber 9 of the detection cable 2 and can operate in the first mode (both ends measurement) of Brillouin spectrum time domain analysis (BOTDA). The second embodiment (one-end measurement) of the Brillouin spectrum time domain analysis (BOTDA) similar to the first embodiment is configured to be operable.

  The optical connector 126 is a component that optically connects optical fibers or optical components and optical fibers.

  The 1 × 2 optical switch 125 is a 1-input 2-output optical switch that emits light incident from an input terminal from one of two output terminals by switching an optical path. The input terminal of the 1 × 2 optical switch 125 is optically connected to the output terminal of the light intensity adjustment unit 124. Also, one output terminal of the 1 × 2 optical switch 125 is optically connected to the other input terminal of the optical coupler 108, and the other output terminal is connected to the other end of the detection optical fiber 9 via the optical connector 126. It is configured to be connectable to. When operating in the first mode (both ends measurement) of BOTDA according to the control (or manual) of the control processing unit 113, the light incident from the input terminal is connected to the other end of the detection optical fiber 9 via the optical connector 126. When the 1 × 2 optical switch 125 is switched so that the light enters the BOTDA and operates in the second mode of BOTDA (one-end measurement), the light incident from the input terminal passes through the optical coupler 1088 and the optical connector 109. Thus, the 1 × 2 optical switch 125 is switched so as to enter one end of the detection optical fiber 9.

  When operating in the first mode of Brillouin spectrum time domain analysis (BOTDA) or the second mode of Brillouin spectrum time domain analysis (BOTDA) according to the control (or manual) of the control processing unit 113, it is incident from the input terminal. The 1 × 2 optical switch 129 is switched so that the reflected light is incident on the strain and temperature detector 114.

  When operating in the first mode of Brillouin spectrum time domain analysis (BOTDA) or the second mode of Brillouin spectrum time domain analysis (BOTDA) according to the control (or manual) of the control processing unit 113, it is incident from the input terminal. The 1 × 2 optical switch 131 is switched so that the incident light enters the optical circulator 112.

  The measuring means 50 for detection according to this embodiment shown in FIG. 16 functions as BOTDA when measuring the Brillouin frequency shift amount, and switches the 1 × 2 optical switches 125, 129, 131 to the first mode (both-end measurement). ). FIG. 17 is a block diagram showing a schematic configuration of the detection measuring means 50 when the detection measuring means 50 shown in FIG. 16 is operated in the first mode.

As shown in FIG. 17, at the time of both-end measurement, the detection measuring unit 50 is incident from one end of the detection optical fiber 9 using the sub light pulse and the main light pulse generated by the light pulse light source LS _p as pump light. At the same time, the continuous light generated by the continuous light source LS _CW is incident from the other end of the detection optical fiber 9 as probe light.

The detection measuring means 50 receives light related to the stimulated Brillouin scattering phenomenon generated in the detection optical fiber 9 by the strain and temperature detector 114, and the Brillouin gain spectrum time domain analysis (B ^Gain- OTDA) or Brillouin loss spectrum time domain analysis (B ^Loss- OTDA) is performed to measure the Brillouin frequency shift amount.

In the optical pulse light source LS _p , the laser light emitted from the laser light source LD is phase-modulated by the pseudo random number from the pseudo random number generator RG in the optical signal generator OSG, so that the main optical pulse using the spread spectrum system is generated. Generated. The pseudorandom number generated by the pseudorandom number generator RG is notified to the strain and temperature detector 114 for demodulation. Then, in the strain and temperature detector 114, the light related to the stimulated Brillouin scattering phenomenon emitted from the detection optical fiber 9 is filtered by the matched filter MF corresponding to the pseudo random number from the pseudo random number generator RG, and the signal processing unit By performing BOTDA signal processing at the SP, the Brillouin frequency shift amount is measured.

Next, the CO ₂ monitoring operation in the ground using the monitoring system 1 configured as described above will be described with reference to FIG. Since the detection measurement unit 50 and the comparison measurement unit 51 have the same configuration, only the detection measurement unit 50 will be described below, and the description of the comparison measurement unit 51 will be omitted.

  In step S1, the strain and temperature detector 114 estimates the Brillouin frequency shift amount, determines the frequency sweep range, and measures the reference peak frequency in step S2. In step S <b> 2, the control processing unit 113 turns on the optical switch 104 and the optical switch 122 according to the generation timing of the pump light in the optical pulse generation unit 103. When the optical switch 122 is turned on, continuous light (probe light) is incident on the optical coupler 123 and branched into two. One of the branched probe lights (continuous light) is incident on the light intensity adjusting unit 124, the light intensity of which is adjusted by the light intensity adjusting unit 124, and incident on the 1 × 2 optical switch 125. When the Brillouin spectrum time domain analysis (BOTDA) is performed in the first mode, the 1 × 2 optical switch 125 is configured such that light incident from the input terminal is connected to the other end of the detection optical fiber 9 via the optical connector 126. The probe light (continuous light) is incident on the other end of the detection optical fiber 9 via the optical connector 126.

  When the Brillouin spectrum time domain analysis (BOTDA) is executed in the second mode, the 1 × 2 optical switch 125 is a detection optical fiber through which the light incident from the input terminal passes through the optical coupler 108 and the optical connector 109. The probe light (continuous light) is incident on one end of the detection optical fiber 9 via the optical coupler 108 and the optical connector 109.

  The strain and temperature detector 114 measures the spectrum of the probe light (continuous light), and notifies the control processing unit 113 of the frequency and light intensity of the probe light. Upon receiving this notification, the control processing unit 113 controls the second ATC 118, the second AFC 119, and the light intensity adjustment unit 124 as necessary so as to obtain an optimum measurement result.

  In the Brillouin spectrum time domain analysis of the first aspect, pump light (sub-light pulse and main light pulse) incident on one end of the detection optical fiber 9 is input from the other end of the detection optical fiber 9 and is detected. Propagation light 9 propagates from one end to the other end of the detection optical fiber 9 while causing a probe light (continuous light) and a stimulated Brillouin scattering phenomenon. In the Brillouin spectrum time domain analysis of the second mode, the pump light (sub light pulse and main light pulse) incident on one end of the detection optical fiber 9 is transmitted from one end of the detection optical fiber 9 as in the first embodiment. Probe light (continuous light) that is incident and reflected by the other end of the detection optical fiber 9 and propagates through the detection optical fiber 9 and propagates from one end to the other end of the detection optical fiber 9 while causing a stimulated Brillouin scattering phenomenon. To do. On / off timings of the optical switch 104 and the optical switch 122 are adjusted by the control processing unit 113 based on the interaction between the pump light and the probe light.

  When the Brillouin spectrum time domain analysis (BOTDA) is executed in the first mode or the second mode, the 1 × 2 optical switch 125 is configured such that light incident from the input terminal is incident on the strain and temperature detector 114. It is switched as follows. Therefore, the light related to the stimulated Brillouin scattering phenomenon is emitted from one end of the detection optical fiber 9, and the strain and temperature detector 114 is passed through the optical connector 109, the optical coupler 108, the optical circulator 107, and the 1 × 2 optical switch 129. Is incident on.

When the reference peak frequency is thus measured, in step S3, the strain and temperature detector 114 measures the reference Rayleigh spectrum, and the detection optical fiber 9 obtained from the detection optical fiber 9 is measured. After the reference peak frequency and the reference Rayleigh spectrum at each actual measurement position are stored in the memory, monitoring of CO ₂ is started.

When the monitoring of CO ₂ is started, in step S4, the strain and temperature detector 114 determines the frequency sweep range in the same manner as in step S1, and in step S5, the peak of the Brillouin spectrum is determined within the determined sweep range. The frequency is measured, and a correction amount is derived in step S6.

  Next, in step S7, the strain and temperature detector 114 derives the peak frequency at the measurement desired position corresponding to each actual measurement value from the peak frequency obtained from each actual value based on the correction amount. In S8, a Brillouin frequency shift amount Δνb is derived.

  Next, in step S9, the strain and temperature detector 114 estimates the Rayleigh frequency shift amount Δνr from the Brillouin frequency shift amount Δνb, and in step S10, the sweep range of the pulsed light frequency from the estimated Rayleigh frequency shift amount Δνr. decide. Within this sweep range, the strain and temperature detector 114 measures the Rayleigh spectrum at step S11, estimates the Rayleigh spectrum at the desired measurement position based on the correction amount at step S12, and shifts the Rayleigh frequency at step S13. The quantity Δνr is derived. In step S <b> 14, the strain and temperature detector 114 detects the strain and temperature at each actually measured position in the longitudinal direction of the detection optical fiber 9.

Next, in step S15, the comparison calculation means 22 derives the CO ₂ concentration distribution and temperature distribution along the longitudinal direction around the sensing unit 14 of the detection cable 2, and in step S16, the already obtained CO 2 is obtained. If there are _two concentration distribution and temperature distribution, which the comparison by fluctuates CO2 states within reservoir R, or CO ₂ makes a determination whether or not leak from the reservoir R.

  Next, in step S <b> 17, the control unit 24 stores the results from the respective comparison calculation units 22 and displays them on the monitor 26.

When monitoring is continued, in step S19, the control means 24 applies pressure to the reaction member 10 in the sensor fiber portion 4 of the detection cable 2 by the removal means re to release CO ₂ from the reaction member 10. And it returns to step S4 and repeats this step S4 to step S17.

Even with the monitoring system 1 as described above, it is possible to monitor CO ₂ for a long period of time constantly and in real time, as in the first embodiment. In addition, by measuring the Brillouin frequency shift amount Δνb and the Rayleigh frequency shift amount Δνr, the strain and temperature generated in each of the optical fibers 9 and 12 can be simultaneously and independently performed using these two frequency shift amounts Δνb and Δνr. Can be calculated. This makes it possible to measure the CO ₂ concentration distribution and temperature distribution in the long direction around each detection cable 2 simultaneously and independently with high spatial resolution. It is possible to monitor the CO ₂ concentration distribution and the temperature distribution in the longitudinal direction around each detection cable 2 simultaneously and independently with high spatial resolution for a period, always and in real time.

  Also, with this monitoring system 1, the detection optical fiber 9 and the comparison optical fiber 12 are long, or the temperature change and strain change in these optical fibers 9 and 12 are large. Even if the deviation is large, the correction amount relating to this deviation is derived from the Brillouin backscattered light, and the Brillouin frequency shift amount Δνb and the Rayleigh frequency shift amount Δνr can be accurately detected by using this correction amount. . In particular, by using this correction amount, it becomes possible to reliably detect the Rayleigh frequency shift amount Δνr (Rayleigh measurement).

  The detection measurement means 20 and 50 and the comparison measurement means 21 and 51 according to the first and second embodiments as described above can constitute a BOTDR by a part of the configuration.

  FIG. 18 is a block diagram in the case where the detection measurement means 20 and 50 and the comparison measurement means 21 and 51 shown in FIGS. 5 and 16 are configured as BOTDR. In FIG. 18, only the blocks necessary for configuring the BOTDR are shown, and some of the blocks are not shown. Since the detection measurement means 20 (50) and the comparison measurement means 21 (51) have the same configuration, only the detection measurement means 20 (50) will be described below, and the comparison measurement means 51 will be described. Description is omitted.

  In FIG. 18, the BOTDR detection measuring means 20 (50) includes a first light source 101, an optical pulse generation unit 103, an optical switch 104, an optical coupler 105, a light intensity / polarization adjustment unit 106, and an optical circulator. 107, an optical connector 109, a first ATC 110, a first AFC 111, a control processing unit 113, a strain and temperature detector 114, and a detection optical fiber 9. In FIG. 18, the optical coupler 102 interposed between the first light source 101 and the optical pulse generator 103 and the optical coupler 108 interposed between the optical circulator 107 and the optical connector 109 are shown in FIGS. In the case where the detection measuring means 20 (50) shown in FIG. 16 is configured as BOTDR, it does not substantially function, so that the illustration is omitted, and the 1 × 2 optical switch 129 that is omitted is connected to the optical circulator 107. A strain and temperature detector 114 is connected.

  In the case of BOTDR, the strain and temperature detector 114 controls each part of the measurement means 20 (50) for detection by inputting and outputting signals to and from the control processing unit 113, and the natural Brillouin scattering received at a predetermined sampling interval. By detecting the light related to the phenomenon, the Brillouin gain spectrum of each region portion of the detection optical fiber 9 in the longitudinal direction of the detection optical fiber 9 is obtained, and the Brillouin gain · Based on the spectrum, the Brillouin frequency shift amount of each region is obtained.

  Each incident light incident from the input terminal of the strain and temperature detector 114 is converted into an electric signal corresponding to the amount of received light by a light receiving element that performs photoelectric conversion, and this electric signal is converted into a digital electric signal by an analog / digital converter. And used to determine the Brillouin gain spectrum. At this time, an optical bandpass filter (hereinafter abbreviated as “optical BPF”) is used, and this optical BPF transmits an optical component having a narrow predetermined transmission frequency band, that is, light having a narrow predetermined frequency band. At the same time, it is an optical component that blocks light in a band other than the predetermined frequency band. For example, the following narrow line width optical bandpass filter is used.

  FIG. 19 is a diagram for explaining a narrow linewidth optical bandpass filter. FIG. 19A is a block diagram showing a configuration of a narrow linewidth optical bandpass filter, and FIGS. 19B to 19D are diagrams for explaining the operation of the narrowlinewidth optical bandpass filter. is there.

  The incident light incident on the input terminal of the strain and temperature detector 114 from the optical circulator 107 is filtered by, for example, the light BPF shown in FIG. 19, and the light related to the natural Brillouin scattering phenomenon is extracted. Further, incident light is converted into an electric signal by a light receiving element, filtered by a matched filter, converted into a digital electric signal by an analog / digital converter, and used for obtaining a Brillouin gain spectrum. Further, if necessary, the electric signal is amplified by the amplifier circuit before being digitally converted.

  For example, as shown in FIG. 19A, the optical BPF 310 includes a first Fabry-Perot etalon filter (hereinafter abbreviated as “EF”) 311 and a second EF 312 optically connected to the first EF 311. Configured. As shown in FIG. 19B, the first EF 311 is set such that the full width at half maximum FWHM1 is a frequency width corresponding to a predetermined transmission frequency band in the optical BPF 310, and the center frequency fa1 of the transmission frequency band is set. Is set to coincide with the center frequency fa of the transmission frequency band in the optical BPF 310.

As shown in FIG. 19C, the second EF 312 has its FSR (Free Spectral Range,
The free spectrum range 2 is set to be wider than the frequency interval between the frequency of the light pulse (sub-light pulse and main light pulse) and the frequency of the natural Brillouin backscattered light, and the transmission frequency band thereof is the first EF 311. The full width at half maximum FWHM2 is set to be equal to or greater than the full width at half maximum FWHM1 of the first EF 311, and one of the center frequencies fa2 of the transmission frequency band is the center frequency of the transmission frequency band in the optical BPF 310. It is set to coincide with fa.

  In the optical BPF 310 having such a configuration, the first EF 311 transmits light having a frequency corresponding to a predetermined transmission frequency band. That is, light having a frequency corresponding to the full width at half maximum FWHM1 is transmitted for each FSR1 of the first EF 311. The light transmitted through the first EF 311 is transmitted through the second EF 312, and only the light having a frequency corresponding to the transmission frequency band of the center frequency fa1 of the first EF 311 is transmitted. For this reason, the transmission frequency characteristic of the narrow-band optical BPF 310 having such a configuration is obtained by combining the transmission frequency characteristic of the first EF 311 shown in FIG. 19B and the transmission frequency characteristic of the second EF 312 shown in FIG. 19C. As shown in FIG. 19D, the center frequency fa of the transmission frequency band is the frequency fa1 (= fa2), the full width at half maximum FWHM is the full width at half maximum FWHM1 of the first EF 311, and the FSR is the second EF 312. FSR2 of Note that the first EF 311 and the second EF 312 may be optically connected in reverse.

  Further, in the case of BOTDR, the control processing unit 113 inputs and outputs a signal to and from the strain and temperature detector 114, thereby calculating the strain and temperature distribution of the detection optical fiber 9 in the longitudinal direction of the detection optical fiber 9. The first light source 101, the first ATC 110, the first AFC 111, the optical pulse generation unit 103, the optical switch 104, and the light intensity / polarization adjustment unit 106 are controlled so as to measure to a far distance with high spatial resolution.

In the BOTDR detection measuring means 20 (50) having such a configuration, the sub light pulse and the main light pulse generated by the first light source 101 and the light pulse generating unit 103 are the optical switch 104, the optical coupler 105, and the light intensity. The light is incident from one end of the detection optical fiber 9 through the polarization adjusting unit 106, the optical circulator 107, and the optical connector 109. A spread spectrum system is used for the main light pulse. The light (natural Brillouin backscattered light) subjected to the natural Brillouin scattering phenomenon in the detection optical fiber 9 is emitted from one end of the detection optical fiber 9 and received by the strain and temperature detector 114. Then, a Brillouin gain spectrum time domain reflection analysis (B ^Gain -OTDR) is performed by the strain and temperature detector 114 to detect the Brillouin frequency shift amount. The light related to the natural Brillouin scattering phenomenon is natural Brillouin backscattered light.

  Even in the BOTDR detection measuring means 20 (50) having such a configuration, the spatial resolution and the measurable distance are independent by configuring the optical pulse with the main optical pulse and the sub optical pulse using the spread spectrum method. Therefore, the strain and temperature can be measured with a high spatial resolution, and the measurable distance can be extended to measure further.

  Next, a method for obtaining the Brillouin frequency shift amount Δνb by subtracting the components from the whole will be described with reference to FIG. Since the detection measurement means 20 (50) and the comparison measurement means 21 (51) have the same configuration, only the detection measurement means 20 (50) will be described below, and the comparison measurement means 21 ( The description of 51) is omitted.

 The horizontal axis in FIG. 20 is the frequency expressed in MHz, and the vertical axis is the Brillouin gain expressed in mW. 20A shows the first to third Brillouin spectra, and FIG. 20B shows the result of subtracting the second and third Brillouin spectra from the whole. The solid line in FIG. 20A is the first Brillouin spectrum, which is the entire Brillouin spectrum, and the broken line is the sum of the second Brillouin spectrum and the third Brillouin spectrum, which are constituent elements.

  In the BOTDA detection measuring means 20 (50) according to the first and second embodiments, first, the sub optical pulse and the main light as pump light are applied to the detection optical fiber 9 under the control of the control processing unit 113. A pulse and continuous light as probe light are incident, and the strain and temperature detector 114 calculates a first Brillouin spectrum based on the light related to the first stimulated Brillouin scattering phenomenon emitted from the detection optical fiber 9 in this case. Ask. Next, under the control of the control processing unit 113, the main light pulse as the pump light and the continuous light as the probe light are made incident on the detection optical fiber 9, and the strain and temperature detector 114 is used for detection in this case. A second Brillouin spectrum is obtained based on the light related to the second stimulated Brillouin scattering phenomenon emitted from the optical fiber 9. Then, the strain and temperature detector 114 may obtain a difference between the first Brillouin spectrum and the second Brillouin spectrum, and measure the strain and temperature generated in the detection optical fiber 9 based on the obtained difference. .

  Alternatively, under the control of the control processing unit 113, the sub optical pulse as the pump light and the continuous light as the probe light are incident on the detection optical fiber 9, and the strain and temperature detector 114 in this case detects the detection light. A third Brillouin spectrum is obtained based on the light related to the third stimulated Brillouin scattering phenomenon emitted from the fiber 9. Then, the strain and temperature detector 114 may obtain a difference between the first Brillouin spectrum and the third Brillouin spectrum and measure the strain temperature generated in the detection optical fiber 9 based on the obtained difference.

  With this configuration, when BOTDA obtains the Brillouin frequency shift amount Δνb, unnecessary components of the Brillouin spectrum can be suppressed, and the Brillouin frequency shift amount Δνb can be obtained more easily and with high accuracy. The strain and temperature generated in the detection optical fiber can be obtained more easily and with higher accuracy.

  Alternatively, for example, in FIG. 20, the first Brillouin spectrum (solid line in FIG. 20A) is first obtained by operating the detection measuring means 20 (50) as described above. Next, the second and third Brillouin spectra are obtained by operating the detection measuring means 20 (50) as described above. Next, the strain and temperature detector 114 determines the difference between the first Brillouin spectrum (solid line in FIG. 20A) and the sum of the second Brillouin spectrum and the third Brillouin spectrum (broken line in FIG. 20A) ( FIG. 20 (B)) is obtained. Then, the strain and temperature detector 114 may measure the strain and temperature generated in the detection optical fiber 9 based on the obtained difference.

  With this configuration, in BOTDA, when the Brillouin frequency shift amount is obtained, an unnecessary component of the Brillouin spectrum can be suppressed, and the Brillouin frequency shift amount Δνb can be obtained more easily and with higher accuracy. As a result, the strain and temperature generated in the detection optical fiber can be determined more easily and with higher accuracy.

  In the BOTDR detection measurement means 20 (50) according to the first and second embodiments, first, the sub optical pulse and the main light pulse are incident on the detection optical fiber 9 under the control of the control processing unit 113. In this case, the strain and temperature detector 114 obtains a first Brillouin gain spectrum based on the light related to the first natural Brillouin scattering phenomenon emitted from the detection optical fiber 9. Next, under the control of the control processing unit 113, the main light pulse is incident on the detection optical fiber 9, and the strain and temperature detector 114 causes the second natural Brillouin scattering emitted from the detection optical fiber 9 in this case. A second Brillouin gain spectrum is obtained based on the light related to the phenomenon. Then, the strain and temperature detector 114 obtains a difference between the first Brillouin gain spectrum and the second Brillouin gain spectrum, and the strain and temperature generated in the detection optical fiber 9 based on the obtained difference. May be measured.

  Alternatively, under the control of the control processing unit 113, the sub optical pulse is incident on the detection optical fiber 9, and the strain and temperature detector 114 causes the third natural Brillouin scattering phenomenon emitted from the detection optical fiber 9 in this case. A third Brillouin gain spectrum is obtained based on the light related to. Then, the strain and temperature detector 114 obtains a difference between the first Brillouin gain spectrum and the third Brillouin gain spectrum, and the strain and temperature generated in the detection optical fiber 9 based on the obtained difference. May be measured.

  With this configuration, when the Brillouin frequency shift amount is obtained in BOTDR, an unnecessary component of the Brillouin gain spectrum can be suppressed, and the Brillouin frequency shift amount Δνb can be obtained more easily and with high accuracy. As a result, the strain and temperature generated in the detection optical fiber 9 can be obtained more easily and with higher accuracy.

  Alternatively, the second and third Brillouin gain spectra are determined, respectively, and the strain and temperature detector 114 determines the first Brillouin gain spectrum, the second Brillouin gain spectrum, and the third Brillouin gain spectrum. Alternatively, the difference and the sum may be obtained, and the strain and temperature generated in the detection optical fiber 9 may be measured based on the obtained difference.

  With this configuration, when obtaining the Brillouin frequency shift amount Δνb in the BOTDR, unnecessary components of the Brillouin gain spectrum can be suppressed, and the Brillouin frequency shift amount Δνb can be more easily and more highly accurate. As a result, the strain and temperature generated in the detection optical fiber 9 can be determined more easily and with higher accuracy.

  In the first and second embodiments described above, the pump light (sub light pulse and main light pulse) of the aspect shown in FIG. 10A is used, but the present invention is not limited to this. For example, Pump light (sub light pulse and main light pulse) having the form shown in FIG. 21 may be used.

  FIG. 21 is a diagram for explaining another configuration of the pump light (sub light pulse and main light pulse). FIG. 21A shows another first configuration of the pump light, and FIG. ) Shows another second configuration of the pump light.

  In the pump light shown in FIG. 10A, the light intensity of the sub light pulse is the same level as the light intensity of the main light pulse. For example, as shown in FIG. The light intensity of the pulse may be smaller than the light intensity of the main light pulse. As described above, the sub-light pulse plays a role in raising the acoustic phonon in advance of the main light pulse in time, so that a large light intensity is not required unlike the main light pulse, and the light intensity of the main light pulse. Smaller than that.

  Each pump light shown in FIGS. 10A and 21A is configured such that the sub light pulse precedes the main light pulse in time without overlapping the main light pulse. As shown in 21 (B), the pump light may have a portion where the main light pulse and the sub light pulse overlap in time. In the pump light having such a configuration, from the viewpoint of starting the acoustic phonon by the sub light pulse temporally preceding the main light pulse, the portion of the sub light pulse that does not overlap the main light pulse is relative to the main light pulse. It is preferable that the time is preceded, and it is more preferable that the portion of the sub light pulse that does not overlap with the main light pulse is longer than the time for which the acoustic phonon is completely activated, for example, about 30 ns or more.

  Here, an experiment in the case where pump light composed of a main light pulse using such a spread spectrum system and a sub light pulse having a portion overlapping with the main light pulse is used for the detection measuring means 20 (or 50). The results will be described. The result of this experiment is, for example, that a difference between the first Brillouin spectrum and the sum of the second Brillouin spectrum and the third Brillouin spectrum in BOTDA is obtained, and the Brillouin frequency due to the distortion generated in the detection optical fiber based on the obtained difference. It is the result of measuring the shift amount.

  FIG. 22 is a diagram illustrating an experimental result of the distributed optical fiber sensor when the pump light having the configuration illustrated in FIG. 21B is used. FIG. 22A shows the Brillouin gain spectrum, and FIG. 22B shows the Brillouin frequency shift. In FIG. 22A, the x-axis is frequency (MHz), the y-axis is Brillouin gain (nW), and the z-axis is the distance (m) in the longitudinal direction of the detection optical fiber 9. The horizontal axis in FIG. 22B is the distance (m) in the longitudinal direction of the detection optical fiber 9, and the vertical axis is the peak frequency (MHz).

  In this experiment, as shown in FIG. 22B, the pump light overlaps the sub-light pulse having a pulse width of 132.3 ns and the sub-light pulse with a time delay of 30 ns from the sub-light pulse. The main optical pulse is divided into 1023 cells having a cell width of 0.1 ns, and each cell is modulated with an M-sequence binary code to be spread spectrum encoded. Has been.

  As shown in Table 1, the detection optical fiber 9 includes a first section from z = 100 cm to z = 101 cm, a second section from z = 200 cm to z = 202 cm, and from z = 300 cm to z = 303 cm. The third section, each section of the fourth section from z = 400 cm to z = 404 cm, is given in advance a distortion of 80 MHz (= about 1600 με) in terms of Brillouin frequency shift.

  When the pump light having the configuration shown in FIG. 21B is made incident on such a detection optical fiber 9 and measured, the Brillouin gain spectrum shown in FIG. 22A is obtained. As a result, FIG. The Brillouin frequency shift shown in FIG. As shown in FIG. 22, the Brillouin frequency shift amount due to a predetermined magnitude of distortion is measured at each distortion position shown in Table 1, and distortion is obtained with high accuracy and high spatial resolution. Understood.

Thus, even when there is a portion where the sub light pulse and the main light pulse overlap, distortion can be obtained with high accuracy and high spatial resolution. As described above, by configuring the pump light with the main light pulse and the sub light pulse using the spread spectrum method, the spatial resolution and the measurable distance can be set independently, so that the distortion is reduced. While being able to measure with high spatial resolution, the measurable distance can be extended to measure farther. As a result, a concentration distribution of CO ₂ (substance to be detected) or the like can be obtained with a high spatial resolution in a wide range of monitoring target areas, and this makes it possible to monitor the CO _{2 with} a high spatial resolution.

  Furthermore, another aspect of the pump light (sub light pulse and main light pulse) used in the detection measurement means 20 (50) and the comparison measurement means 21 (51) of the first and second embodiments will be described.

  FIG. 23 is a diagram for explaining still another configuration of the pump light (sub-light pulse and main light pulse) and a matched filter. FIG. 23A shows the configuration of the pump light, and FIG. ) Is a diagram showing a matched filter. FIG. 24 is a diagram for explaining the configuration and operation of an optical pulse generator for generating pump light having the configuration shown in FIG.

  The pump light configured as shown in FIG. 21B is composed of a sub light pulse having a portion that temporally precedes the main light pulse and having a portion overlapping the main light pulse, and a main light pulse. As shown in FIG. 23A, the pump light has a sub-light pulse that overlaps the main light pulse so as to completely coincide with the main light pulse without having a portion that precedes the main light pulse in time, And an optical pulse. In other words, the rising timing and the falling timing of the sub optical pulse coincide with the rising timing and the falling timing of the main optical pulse, respectively.

  Such pump light having the configuration shown in FIG. 13A can be generated from, for example, the optical pulse generation unit 103 having the configuration shown in FIG. The optical pulse generation unit 103 configured as shown in FIG. 24 has the same configuration as that of the optical pulse generation unit 103 and the optical switch 104 shown in FIG. 9, and its operation is the same as that of the optical pulse generation unit 103 shown in FIG. It is different from the operation. For this reason, description of the structure is abbreviate | omitted here and the operation | movement is demonstrated.

  First, in order to generate pump light having the configuration shown in FIG. 23A, the LN intensity modulator 201 leaks (emits) a predetermined level of light (leakage light) in order to generate a sub-light pulse. ) So that it is on.

  The continuous light L11 (= L1) emitted from the first light source 101 is incident on the LN intensity modulator 201 of the optical pulse generation unit 103 via the optical coupler 102. When the continuous light L11 is incident, the LN intensity modulator 201 emits the leakage light.

  In the optical pulse generation unit 103, an operation timing pulse having a pulse width D corresponding to the pulse width D of the main optical pulse is output from the timing pulse generator 204 to the multiplier 203 and input from the DC power source 202 at the generation timing of the pump light. The DC voltage thus multiplied is applied to the signal electrode of the LN intensity modulator 201. Accordingly, the continuous light L11 is emitted by the LN intensity modulator 201 as an optical pulse L12 in which an optical pulse having a pulse width D is superimposed on leakage light.

  Then, the optical pulse generator 103 multiplies the pseudo random number from the pseudo random number generator 214 at the time timing of the cell width during the time width D corresponding to the pulse width D of the main optical pulse at the generation timing of the main optical pulse. Sequentially output to 213, multiplied by the DC voltage input from the DC power supply 212, the DC voltage modulated by the M-sequence binary code is LN at the time timing of the cell width, with the time width D from the generation timing of the main optical pulse. The signal is sequentially applied to the signal electrodes of the phase modulator 211. As a result, the optical pulse L12 is emitted as an optical pulse L13 in which a portion (corresponding to the main optical pulse) modulated by the M-sequence binary code is superimposed on the leakage light by the LN phase modulator 211.

  In the EDFA 221, the light pulse L13 is amplified until it reaches a predetermined light intensity, and is emitted as a light pulse L14.

Furthermore, in the light pulse generation unit 103, in accordance with the generation timing of the pump light, the operation timing of the pulse width D _sub of corresponding to the pulse width D _sub of the sub light pulse ₍₌ pulse width D of main light pulse) _{(= D)} The pulse is output from the timing pulse generator 234 to the multiplier 233, multiplied by the DC voltage input from the DC power supply 232, and a DC voltage having a pulse width D _sub (= D) is applied to the signal electrode of the LN intensity modulator 231. Is done. As a result, the optical pulse L14 is filtered by the LN intensity modulator 231 to remove noise such as spontaneous emission light accompanying the optical pulse L14 by the EDFA 221 and light caused by leakage light before and after the optical pulse L14 (in the EDFA 221). Amplified leakage light) is removed, a sub-light pulse having a pulse width D _sub (= D) and unmodulated, and a main light pulse having a pulse width D (= D _sub ) and spread spectrum encoded The main light pulse coincides with the sub light pulse in time and overlaps and is emitted as pump light L15.

  These optical pulses (sub optical pulse and main optical pulse) shown in FIG. 10A, FIG. 21A, FIG. 21B, and FIG. The comparison measurement means can be used in the same manner as the BOTDA detection measurement means and the comparison measurement means. Note that, as described above, since BOTDR uses acoustic phonons excited by thermal noise, the sub light pulse does not necessarily precede the main light pulse in terms of time. Of course, the sub light pulse may precede the main light pulse in terms of time.

  Further, as the pump light (sub light pulse and main light pulse), not only the above-mentioned stepped pulse but also the following pulse may be used.

  FIG. 25 is a diagram illustrating waveforms of the sub light pulse and the main light pulse of another example. In each of the following drawings, the horizontal axis represents time (time) expressed in ns, and the vertical axis represents light intensity. In the example shown in FIG. 25, the main light pulse OPm has a first predetermined pulse width D1 and a rectangular shape having a first predetermined light intensity P1 (the light intensity P is constant at the first predetermined light intensity P1 between the first predetermined pulse widths D1. The sub optical pulse OPs has a second predetermined pulse width D2 and a rectangular shape having the second predetermined light intensity P2 (the light intensity P is constant at the second predetermined light intensity P2 between the second predetermined pulse widths D2). . A predetermined time is provided between the sub light pulse OPs and the main light pulse OPm. Accordingly, the second predetermined pulse width D2 of the sub light pulse OPs is shorter than the time from the rise of the sub light pulse OPs to the rise of the main light pulse OPm.

  For example, the main light pulse OPm has a pulse width D1 of 1 ns and a light intensity P1 of 0.062, and the sub light pulse OPs has a pulse width D2 of 5 ns and a light intensity P2 of 0.005. A time of 7 ns is left between the sub light pulse OPs and the main light pulse OPm (from the fall of the sub light pulse OPs to the rise of the main light pulse OPm).

  FIG. 26 is a diagram illustrating waveforms of the sub light pulse and the main light pulse of another example. In the example shown in FIG. 25, the main optical pulse OPm has a rectangular shape with a first predetermined pulse width D1 and a first predetermined light intensity P1, and the sub optical pulse OPs has a second predetermined light intensity with a second predetermined pulse width D2. (Maximum light intensity) The light intensity P rises at P2, and the light intensity P gradually decreases with time, and the main light pulse OPm rises almost immediately after the end of the sub light pulse OPs. For example, the main light pulse OPm has a pulse width D1 of 1 ns and a light intensity P1 of 0.062, and the sub light pulse OPs has a pulse width D2 of 13 ns and a rising light intensity P2 of 0.005. is there.

  FIG. 27 is a diagram illustrating waveforms of the sub light pulse and the main light pulse of another example. In the example shown in FIG. 27A, the main optical pulse OPm has a first predetermined pulse width D1 and a rectangular shape having a first predetermined light intensity P1, and the sub optical pulse OPs has a second predetermined pulse width D2 and a light intensity. P is a right triangle shape that gradually increases with time until the second predetermined light intensity (maximum light intensity) P2, and the first optical pulse OPm rises almost immediately after the end of the second optical pulse OPs. For example, the main light pulse OPm has a pulse width D1 of 1 ns and a light intensity P1 of 0.062, and the sub light pulse OPs has a pulse width D2 of 13 ns and the falling light intensity P2 has a maximum light intensity. And 0.005.

  In the example shown in FIG. 27B, the main light pulse OPm has a first predetermined pulse width D1 and a rectangular shape having a first predetermined light intensity P1, and the sub light pulse OPs has a second predetermined pulse width D2 and a light intensity. P is an isosceles triangle shape that gradually increases to a second predetermined light intensity (maximum light intensity) P2 over time and then gradually decreases over time, and the main light pulse OPm is the end of the sub light pulse OPs. It stands up almost immediately after. For example, the main light pulse OPm has a pulse width D1 of 1 ns and a light intensity P1 of 0.062, and the sub light pulse OPs has a pulse width D2 of 13 ns and the maximum light intensity P2 at the center of the pulse is 0. .005.

  As shown in FIG. 27C, the main optical pulse OPm has a first predetermined pulse width D1 and a rectangular shape having a first predetermined light intensity P1, and the sub optical pulse OPs has a second predetermined pulse width D2 and a light intensity. P is a Gaussian curve shape that gradually increases to the second predetermined light intensity (maximum light intensity) P2 over time and then gradually decreases over time. A predetermined time is provided between the sub light pulse OPs and the main light pulse OPm. Accordingly, the second predetermined pulse width D2 of the sub light pulse OPs is shorter than the time from the rise of the sub light pulse OPs to the rise of the main light pulse OPm. For example, the main light pulse OPm has a pulse width D1 of 1 ns and a light intensity P1 of 0.062, and the sub light pulse OPs has a pulse width D2 of 5 ns and a maximum light intensity P2 of 0.005. A time of 4.5 ns is left between the sub light pulse OPs and the main light pulse OPm (from the fall of the sub light pulse OPs to the rise of the main light pulse OPm).

  FIG. 28 is a diagram illustrating waveforms of the sub light pulse and the main light pulse of another example. In the example shown in FIG. 28, the first and second optical pulses OPw1 and OPw2 have the same pulse width and optical intensity, and a predetermined time is provided between the first optical pulse OPw1 and the second optical pulse OPw2. ing. For example, the first and second optical pulses OPw1 and OPw2 have a pulse width of 1 ns, a light intensity of 0.062, and a predetermined time of 5 ns.

  Note that the detection cable of the present invention and the monitoring system including the detection cable are not limited to the above-described embodiments, and various changes can be made without departing from the scope of the present invention. is there.

The substance to be detected that can be detected by the detection cable and the substance to be detected in the monitoring system are not limited to CO ₂ , but may be other substances, such as butane or propane. In this case, the reaction member is made of a material that applies pressure and / or heat to the detection optical fiber 9 by coming into contact with a substance to be detected such as butane or propane. That is, the detection cable can detect the type of substance to be detected according to the material constituting the reaction member. Also, when the reaction member is a material that reacts with a plurality of substances and changes in volume and heat, the material of the gate member 11 is changed to a material that allows only a specific substance to be detected to pass through. Detection and monitoring are possible.

In the sensor fiber portion 4 of the above embodiment, the gate member 11 surrounds the reaction member 10 from the outside, but if the reaction member 10 is made of a material that absorbs or adsorbs only CO ₂ (detected substance), The gate member 11 may not be provided outside the reaction member 10.

  Although the removal means re of the said embodiment is a structure which applies a pressure to the reaction member 10, it is not limited to this. For example, when releasing or desorbing a substance absorbed or adsorbed by applying heat to the reaction member, the removing means is configured to apply heat to the reaction member.

  Specifically, the removing means arranges a pipe (steam pipe) capable of circulating steam inside the cable sheath 7 instead of the pressurizing pipe 6, and supplies high-temperature steam into the steam pipe. It may be configured. According to such a configuration, the heat of the steam flowing in the steam pipe is transmitted to the reaction member through the pipe wall, and the detected substance absorbed or adsorbed by the reaction member is released or desorbed.

  Further, the removing means is constituted by a metal film that coats the surface of the detection optical fiber 9 or a metal wire (for example, an electric wire) disposed along the detection optical fiber 9, and the metal film or the metal wire. The reaction member may be heated by causing electricity to flow through and generating heat.

The reaction member 10 of the above embodiment is provided on substantially the entire detection optical fiber 9 in the longitudinal direction, but may be provided so as to cover only a part thereof. That is, it is only necessary that at least a portion corresponding to the sensing unit 14 provided in a part of the detection cable 2 is covered with the reaction member 10. If the reaction member 10 is provided at such a site, the substance to be detected can be detected and monitored. This is because the non-sensing part 15 is not provided with the communication part 14a, and therefore the substance to be detected can freely enter and exit the cable sheath 7 even if the substance to be detected exists around the detection cable 2. This is because even if the reaction member 10 is arranged, the concentration of CO ₂ around the detection cable 2 cannot be detected accurately in real time. Moreover, the reaction member 10 does not need to be continuous in the longitudinal direction, and may be intermittent.

  In the monitoring system 1 of the above-described embodiment, detection and monitoring of a target substance are performed using scattered light based on both the Brillouin scattering phenomenon and the Rayleigh scattering phenomenon, but the present invention is not limited to this, and the Brillouin scattering phenomenon is not limited thereto. Alternatively, detection and monitoring may be performed using scattered light based on one of the Rayleigh scattering phenomena. That is, in the monitoring system 1 of the above embodiment, the concentration distribution and the temperature distribution of the substance to be detected can be simultaneously and independently performed with high spatial resolution along the detection cable 2 by using scattered light based on both scattering phenomena. If measurement is performed but only one of the concentration or temperature of the substance to be detected needs to be measured, or if the spatial resolution of the concentration distribution etc. may be low, use scattered light based on one of the scattering phenomena. Thus, a monitoring system that performs detection and monitoring may be used.

  In the BOTDA detection measurement means 20 (50) and the comparison measurement means 21 (51) in the above embodiment, the frequency of the pump light (sub light pulse and main light pulse) is fixed, and the frequency of the probe light (continuous light). However, the Brillouin spectrum may be measured with the probe light frequency fixed and the pump light frequency swept within the predetermined frequency range.

DESCRIPTION OF SYMBOLS 1 Monitoring system 2 Detection cable 3 Monitoring apparatus main body 4 Sensor fiber part 5 Comparison fiber part 9 Optical fiber for detection 10 Reaction member 11 Gate member (sorting member)
12 Optical fiber for comparison 13 Metal tube (protective member)

Claims (13)

A detection cable for detecting a specific target substance using a Brillouin scattering phenomenon and / or a Rayleigh scattering phenomenon in an optical fiber,
Optical fiber for detection;
A reaction member that applies pressure and / or heat to the optical fiber for detection by being in contact with the substance to be detected;
A comparison optical fiber disposed along the detection optical fiber;
And a protective member for relaxing pressure and / or heat applied from the outside to the comparative optical fiber.   The detection cable according to claim 1, wherein the reaction member is provided continuously or intermittently along the detection optical fiber.   The reaction member is made of a material that covers the detection optical fiber in the circumferential direction, changes its volume by contacting the substance to be detected, and transmits the heat of the substance to be detected to the detection optical fiber. The detection cable according to claim 1, wherein the detection cable is provided.   The detection cable according to claim 3, wherein the reaction member is deformed according to a concentration of a substance to be detected in contact therewith.   And further comprising a selection member that collectively surrounds the detection optical fiber and the reaction member from outside and allows the detection target substance to pass from the outside to the inside where the detection optical fiber and the reaction member are present. The detection cable according to any one of claims 1 to 4. It further comprises a removing means capable of heating or pressurizing the reaction member,
The reaction member absorbs or adsorbs the detected substance by being in contact with the detected substance, and releases or desorbs the absorbed or adsorbed detected substance by being heated or pressurized by the removing unit. The detection cable according to any one of claims 1 to 5. The removing means has a pressurizing tube that circulates in the fluid inside and expands in a radial direction when the liquid is heated to pressurize the reaction member,
The detection cable according to claim 6, wherein the reaction member releases or desorbs the absorbed or adsorbed substance to be detected by being pressurized by the pressure tube. At least a cable sheath that collectively surrounds the detection optical fiber, the reaction member, the comparison optical fiber, the protection member, and the pressurizing tube from the outside;
The detection cable according to claim 7, wherein the cable sheath includes a communication portion that allows communication between the outer side and the inner side and allows passage of the substance to be detected.   The detection cable according to claim 1, wherein the protection member is a protection pipe that surrounds the comparison optical fiber. A slot extending along the sensing optical fiber and having a plurality of spiral grooves on the surface;
The detection cable according to claim 1, wherein the detection optical fiber and the comparison optical fiber are accommodated in different grooves. A monitoring system for monitoring a specific substance to be detected using an optical fiber,
The detection cable according to any one of claims 1 to 10,
A light source for injecting inspection light into the detection optical fiber and the comparison optical fiber of the detection cable; and
Measuring means for measuring scattered light based on the Brillouin scattering phenomenon and / or the Rayleigh scattering phenomenon caused by the inspection light in the detection optical fiber and the comparison optical fiber;
Monitoring means comprising: calculating means for detecting the substance to be detected based on the scattered light in the optical fiber for detection measured by the measuring means and the scattered light in the optical fiber for comparison. system. The measurement means includes a Brillouin measurement unit for deriving a Brillouin frequency shift amount due to pressure and heat applied to each optical fiber using the Brillouin scattering phenomenon in the detection optical fiber and the comparison optical fiber, and
A Rayleigh measuring unit for deriving a Rayleigh frequency shift amount due to pressure and heat applied to each optical fiber using the Rayleigh scattering phenomenon in the detection optical fiber and the comparison optical fiber,
The calculation means includes a Brillouin frequency shift amount in the detection optical fiber and the comparison optical fiber derived by the Brillouin measurement unit, and the detection optical fiber and the comparison optical fiber derived by the Rayleigh measurement unit. 12. The monitoring system according to claim 11, wherein the concentration distribution and the temperature distribution of the detected substance in the longitudinal direction around the detection optical fiber can be calculated based on the Rayleigh frequency shift amount in . The Brillouin measurement unit relates to an actual measurement position determined based on a travel time of light propagating in each optical fiber, and a measurement desired position on the optical fiber that deviates from the actual measurement position as the optical fibers expand and contract. Deriving a correction amount and deriving the Brillouin frequency shift amount using this correction amount,
The monitoring system according to claim 12, wherein the Rayleigh measuring unit derives the Rayleigh frequency shift amount using the correction amount derived by the Brillouin measuring unit.