A fiber-optic sensing system and a measurement method for simultaneously measuring multiple parameters of a warm pressure sound

Abstract

The present application relates to a kind of temperature pressure acoustic multi-parameter synchronous measurement with optical fiber sensing system and measurement method, optical fiber sensing system includes light output component, circulator, optical fiber component and demodulation component;Light output component is connected with the first port of circulator, optical fiber component is connected with the second port of circulator, demodulation component is connected with the third port of circulator;Multiple bragg gratings are engraved on optical fiber component;Measurement method is: laser injection is obtained in optical fiber-distributed acoustic signal, temperature value and pressure value by demodulation;Compared with traditional sensing system, by setting optical fiber component, the tail end of optical fiber component realizes the measurement of pressure;Bragg grating realizes the quasi-distributed measurement of temperature;Rayleigh backscattering light is used to realize the distributed measurement of acoustic wave, thereby, reduce construction difficulty;At the same time, when monitoring in situ to natural gas hydrate production well, reduce installation difficulty, improve installation efficiency.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and in particular to a fiber optic sensing system and method for synchronous measurement of multiple parameters including temperature, pressure, and acoustics. Background Technology

[0002] Currently, the development of marine natural gas hydrates mainly adopts the formation fluid extraction method for depressurization production. During the development process, the decomposition and transfer of hydrates will inevitably disturb various physical properties of the attached sediments. Therefore, the process changes of marine natural gas hydrate development can be monitored by detecting changes in the physical properties (temperature, pressure, sound) of sediments and the properties of production products (gas, water).

[0003] Specifically, changes in saturation during hydrate production can alter key geophysical properties of the reservoir, such as temperature, pressure, acoustic response, and mechanical properties. Utilizing these physical characteristics, geophysical methods can be used for remote sensing, monitoring, and early warning of changes in hydrate reservoir properties and potential environmental impacts such as surface deformation.

[0004] However, current monitoring of temperature, pressure, and sound waves uses independent sensors. To achieve simultaneous measurement of all three, it is necessary to use all three sensors together, which increases the difficulty of construction. In addition, it increases the difficulty of installation when monitoring natural gas hydrate production wells. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a fiber optic sensing system and measurement method for simultaneous measurement of multiple parameters (temperature, pressure, and acoustic). Its advantages include reducing construction difficulty; at the same time, it improves installation efficiency and reduces installation difficulty when monitoring natural gas hydrate production wells in situ.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution: In one aspect, this invention provides a fiber optic sensing system for simultaneous measurement of multiple parameters (temperature, pressure, and sound), comprising an optical output component, a circulator, an optical fiber component, and a demodulation component; the optical output component is connected to a first port of the circulator, the optical fiber component is connected to a second port of the circulator, and the demodulation component is connected to a third port of the circulator; a plurality of Bragg gratings are etched on the optical fiber component, and the plurality of Bragg gratings are spaced apart along the extension direction of the optical fiber component; the tail end of the optical fiber component is used for pressure measurement; the Bragg gratings on the optical fiber component are used for quasi-distributed temperature measurement; and the Rayleigh backscattered light in the optical fiber component is used for distributed sound wave measurement.

[0007] Preferably, the fiber optic sensing system for simultaneous measurement of multiple parameters (temperature, pressure, and sound) provided by the present invention includes an optical fiber assembly comprising an optical fiber and a pressure gauge. One end of the optical fiber is connected to the second port of the circulator, and the other end of the optical fiber is connected to the pressure gauge. A plurality of Bragg gratings are etched on the optical fiber, and the plurality of Bragg gratings are spaced apart along the extension direction of the optical fiber. The pressure gauge is used to measure pressure. Rayleigh backscattered light in the optical fiber is used to achieve distributed measurement of sound waves.

[0008] Preferably, the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided by the present invention includes a narrow-linewidth laser, a modulation unit, and a coupling unit in the optical output component. The narrow-linewidth laser is connected to the modulation unit, and one end of the modulation unit away from the narrow-linewidth laser is connected to the coupling unit. The one end of the coupling unit away from the modulation unit is connected to the first port of the circulator. The narrow-linewidth laser is used to output a narrow-linewidth continuous laser of a preset wavelength.

[0009] Preferably, the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided by the present invention includes a modulation unit comprising a modulation module and a first erbium-doped fiber amplifier, a narrow linewidth laser connected to the modulation module, and both the modulation module and the first erbium-doped fiber amplifier connected to the coupling unit.

[0010] Preferably, the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided by the present invention includes an acousto-optic modulator and a radio frequency driver in the modulation module. The narrow linewidth laser is connected to the first end of the acousto-optic modulator, the radio frequency driver is connected to the second end of the acousto-optic modulator, and the third end of the acousto-optic modulator and the first erbium-doped fiber amplifier are both connected to the coupling unit. The radio frequency driver is used to control the working state of the acousto-optic modulator.

[0011] Preferably, the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided by the present invention includes a coupling unit comprising a fiber optic coupler and a second erbium-doped fiber amplifier. The fiber optic coupler is connected to the second erbium-doped fiber amplifier, and the end of the second erbium-doped fiber amplifier facing away from the fiber optic coupler is connected to the first port of the circulator. The third end of the acousto-optic modulator and the first erbium-doped fiber amplifier are both connected to the end of the fiber optic coupler facing away from the second erbium-doped fiber amplifier.

[0012] Preferably, the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided by the present invention includes a demodulation component comprising a wavelength division multiplexer (WDM), a detection unit, a spectrometer, and a computer. The first interface of the WDM is connected to the third port of the circulator; the second interface of the WDM is connected to the detection unit; and the end of the detection unit facing away from the WDM is connected to the computer. The third interface of the WDM is connected to the spectrometer, and the end of the spectrometer facing away from the WDM is connected to the computer.

[0013] Preferably, the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided by the present invention includes a detection unit comprising a photodetector and a high-speed data acquisition card. The photodetector is connected to the high-speed data acquisition card, the end of the high-speed data acquisition card away from the photodetector is connected to the computer, and the end of the photodetector away from the high-speed data acquisition card is connected to the second interface of the wavelength division multiplexer.

[0014] On the other hand, the present invention provides a measurement method for a fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters, comprising the following steps:

[0015] The optical output component injects the output laser into the optical fiber through the circulator;

[0016] Rayleigh backscattered light in the optical fiber, as well as the reflected light from the Bragg grating and the pressure gauge, reaches the demodulation component through the circulator. The demodulation component demodulates the distributed acoustic signal, temperature value, and pressure value.

[0017] Preferably, the measurement method of the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided by the present invention includes the following steps: the optical output component injects the output laser into the optical fiber through the circulator; the narrow linewidth laser outputs a narrow linewidth continuous laser of a preset wavelength; the narrow linewidth continuous laser reaches the acousto-optic modulator for pulse and frequency shift modulation; the first erbium-doped fiber amplifier generates spontaneous emission light; the output light of the acousto-optic modulator and the first erbium-doped fiber amplifier are combined by the fiber coupler and amplified by the second erbium-doped fiber amplifier; and the amplified light is injected into the optical fiber through the circulator.

[0018] Preferably, the measurement method of the fiber optic sensing system for synchronous measurement of temperature, pressure, and acoustic parameters provided by the present invention, wherein the Rayleigh backscattered light in the optical fiber and the reflected light from the Bragg grating and the pressure gauge reach the demodulation component through the circulator, and the demodulation component demodulates to obtain distributed acoustic signals, temperature values, and pressure values, including:

[0019] Rayleigh backscattered light in the optical fiber, as well as the reflected light from the Bragg grating and the pressure gauge, reaches the wavelength division multiplexer through the third port of the circulator;

[0020] The Rayleigh backscattered light reaches the photodetector and is converted into an electrical signal. The electrical signal is acquired by the high-speed data acquisition card and converted into a digital signal. The digital signal is transmitted to the computer for heterodyne demodulation to obtain the distributed acoustic wave signal in the optical fiber.

[0021] The reflected light reaches the spectrometer, and the spectral signal obtained by the spectrometer is transmitted to the computer for demodulation processing to obtain the temperature value and the pressure value.

[0022] In summary, the beneficial technical effects of this invention are as follows: The fiber optic sensing system and measurement method for synchronous measurement of multiple parameters (temperature, pressure, and sound) provided in this application include an optical output component, a circulator, an optical fiber component, and a demodulation component; the optical output component is connected to the first port of the circulator, the optical fiber component is connected to the second port of the circulator, and the demodulation component is connected to the third port of the circulator; multiple Bragg gratings are etched on the optical fiber component, and the multiple Bragg gratings are spaced apart along the extension direction of the optical fiber component; the tail end of the optical fiber component is used to realize pressure measurement; the Bragg gratings on the optical fiber component are used to realize quasi-distributed temperature measurement; the Rayleigh backscattered light in the optical fiber component is used to realize distributed sound wave measurement; the measurement method is: laser injection into the optical fiber - demodulation to obtain distributed sound wave signals, temperature values, and pressure values; by setting the optical fiber component, compared with the traditional sensing system, the tail end of the optical fiber component realizes pressure measurement; the Bragg grating realizes quasi-distributed temperature measurement; and the Rayleigh backscattered light is used to realize distributed sound wave measurement, thereby reducing the construction difficulty; at the same time, in the in-situ monitoring of natural gas hydrate production wells, the installation difficulty is reduced and the installation efficiency is improved. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the fiber optic sensing system for synchronous measurement of multiple parameters (temperature, pressure, and acoustic) provided in an embodiment of the present invention.

[0024] Figure 2 This is a spectral diagram of an optical fiber sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided in another embodiment of the present invention.

[0025] Figure 3 This is a flowchart of a measurement method for a fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters provided in another embodiment of the present invention.

[0026] In the diagram, 1 is the fiber optic sensing system; 10 is the optical output component; 11 is the narrow linewidth laser; 12 is the modulation unit; 121 is the modulation module; 1211 is the acousto-optic modulator; 1212 is the radio frequency driver; 122 is the first erbium-doped fiber amplifier; 13 is the coupling unit; 131 is the fiber optic coupler; 132 is the second erbium-doped fiber amplifier; 20 is the circulator; 30 is the fiber optic assembly; 31 is the fiber optic cable; 311 is the Bragg grating; 32 is the pressure gauge; 40 is the demodulation component; 41 is the wavelength division multiplexer; 42 is the detection unit; 421 is the photodetector; 422 is the high-speed data acquisition card; 43 is the spectrometer; and 44 is the computer. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Reference Figure 1 This invention discloses a fiber optic sensing system 1 for synchronous measurement of multiple parameters (temperature, pressure, and acoustic), comprising an optical output component 10, a circulator 20, an optical fiber component 30, and a demodulation component 40. The optical output component 10 is connected to a first port of the circulator 20, the optical fiber component 30 is connected to a second port of the circulator 20, and the demodulation component 40 is connected to a third port of the circulator 20. Multiple Bragg gratings 311 are etched on the optical fiber component 30, and the multiple Bragg gratings 311 are spaced apart along the extension direction of the optical fiber component 30. The tail end of the optical fiber component 30 is used for pressure measurement. The Bragg gratings 311 on the optical fiber component 30... 1. Used to achieve quasi-distributed temperature measurement; Rayleigh backscattered light in fiber optic assembly 30 is used to achieve distributed sound wave measurement; by setting fiber optic assembly 30, compared with traditional sensing systems, pressure measurement is achieved at the tail end of fiber optic assembly 30; Bragg grating 311 achieves quasi-distributed temperature measurement; Rayleigh backscattered light is used to achieve distributed sound wave measurement, thereby reducing construction difficulty; at the same time, when monitoring natural gas hydrate production wells in situ, fiber optic assembly 30 is small in size and easy to install between the production tubing and casing, thereby reducing installation difficulty and improving installation efficiency.

[0029] It should be noted that, with Figure 1 Taking the orientation shown as an example, the first port of the circulator 20 is located on the left side of the circulator 20, the second port of the circulator 20 is located on the right side of the circulator 20, and the third port of the circulator 20 is located at the bottom of the circulator 20; the tail end of the fiber optic assembly 30 is the right end of the fiber optic assembly 30.

[0030] The measurement process of the fiber optic sensing system 1 for simultaneous measurement of temperature, pressure and sound parameters provided in this embodiment is as follows: the narrow linewidth continuous laser output by the optical output component 10 is injected into the fiber optic component 30 through the circulator 20. The Rayleigh backscattered light and reflected light in the fiber optic component 30 reach the demodulation component 40 through the circulator 20. The demodulation component 40 demodulates to obtain the distributed acoustic wave signal, temperature value and pressure value.

[0031] Furthermore, in this embodiment, the optical fiber assembly 30 includes an optical fiber 31 and a pressure gauge 32. One end of the optical fiber 31 is connected to the second port of the circulator 20, and the other end of the optical fiber 31 is connected to the pressure gauge 32. A plurality of Bragg gratings 311 are etched on the optical fiber 31, and the plurality of Bragg gratings 311 are spaced apart along the extension direction of the optical fiber 31. The pressure gauge 32 is used to measure pressure. The Rayleigh backscattered light in the optical fiber 31 is used to realize the distributed measurement of sound waves.

[0032] Specifically, with Figure 1 Taking the orientation shown as an example, the left end of the optical fiber 31 is connected to the second port of the circulator 20, and the right end of the optical fiber 31 is connected to the pressure gauge 32.

[0033] During use, the Rayleigh backscattered light in the optical fiber 31, as well as the reflected light from the Bragg grating 311 and the pressure gauge 32, reaches the demodulation assembly 40 through the circulator 20.

[0034] For example, fiber 31 can be a common single-mode fiber, but of course, fiber 31 can also be other types of fiber.

[0035] Furthermore, in this embodiment, the optical output component 10 includes a narrow linewidth laser 11, a modulation unit 12, and a coupling unit 13. The narrow linewidth laser 11 is connected to the modulation unit 12, one end of the modulation unit 12 away from the narrow linewidth laser 11 is connected to the coupling unit 13, and one end of the coupling unit 13 away from the modulation unit 12 is connected to the first port of the circulator 20. The narrow linewidth laser 11 is used to output a narrow linewidth continuous laser with a preset wavelength λc.

[0036] During use, the narrow linewidth laser 11 outputs a narrow linewidth continuous laser with a preset wavelength λc. The narrow linewidth continuous laser is injected into the optical fiber 31 through the modulation unit 12, the coupling unit 13 and the circulator 20 in sequence.

[0037] Furthermore, in this embodiment, the modulation unit 12 includes a modulation module 121 and a first erbium-doped fiber amplifier, the narrow linewidth laser 11 is connected to the modulation module 121, and both the modulation module 121 and the first erbium-doped fiber amplifier are connected to the coupling unit 13.

[0038] During use, the narrow linewidth laser 11 outputs a narrow linewidth continuous laser with a preset wavelength λc. The narrow linewidth connecting laser reaches the modulation module 121 for pulse and frequency shift modulation. The first erbium-doped fiber amplifier generates spontaneous emission light. The output light of the modulation module 121 and the first erbium-doped fiber amplifier (i.e., the pulse and frequency shift modulated narrow linewidth connecting laser output by the modulation module 121 and the emission light output by the first erbium-doped fiber amplifier) ​​are combined and amplified by the coupling unit 13 and then injected into the fiber 31 through the circulator 20.

[0039] Furthermore, in this embodiment, the modulation module 121 includes an acousto-optic modulator 1211 and a radio frequency driver 1212. The narrow linewidth laser 11 is connected to the first end of the acousto-optic modulator 1211, the radio frequency driver 1212 is connected to the second end of the acousto-optic modulator 1211, and the third end of the acousto-optic modulator 1211 and the first erbium-doped fiber amplifier are both connected to the coupling unit 13. The radio frequency driver 1212 is used to control the working state of the acousto-optic modulator 1211.

[0040] During use, the narrow linewidth laser 11 outputs a narrow linewidth continuous laser with a preset wavelength λc. The narrow linewidth laser reaches the acousto-optic modulator 1211 for pulse and frequency shift modulation. The first erbium-doped fiber amplifier generates spontaneous emission light. The output light of the acousto-optic modulator 1211 and the first erbium-doped fiber amplifier is combined and amplified by the coupling unit 13, and then injected into the fiber 31 through the circulator 20.

[0041] Continue to refer to Figure 1 In this embodiment, the coupling unit 13 includes an optical fiber coupler 131 and a second erbium-doped optical fiber amplifier. The optical fiber coupler 131 is connected to the second erbium-doped optical fiber amplifier. The end of the second erbium-doped optical fiber amplifier away from the optical fiber coupler 131 is connected to the first port of the circulator 20. The third end of the acousto-optic modulator 1211 and the first erbium-doped optical fiber amplifier are both connected to the end of the optical fiber coupler 131 away from the second erbium-doped optical fiber amplifier.

[0042] During use, the output light of the acousto-optic modulator 1211 and the first erbium-doped fiber amplifier is combined by the fiber coupler 131 and then amplified by the second erbium-doped fiber amplifier before being injected into the fiber 31 through the circulator 20.

[0043] Furthermore, in this embodiment, the demodulation component 40 includes a wavelength division multiplexer 41, a detection unit 42, a spectrometer 43, and a computer 44. The first interface of the wavelength division multiplexer 41 is connected to the third port of the circulator 20, the second interface of the wavelength division multiplexer 41 is connected to the detection unit 42, and the end of the detection unit 42 facing away from the wavelength division multiplexer 41 is connected to the computer 44; the third interface of the wavelength division multiplexer 41 is connected to the spectrometer 43, and the end of the spectrometer 43 facing away from the wavelength division multiplexer 41 is connected to the computer 44.

[0044] The reflected wavelength of wavelength division multiplexer 41 corresponds to the preset wavelength λc of narrow linewidth laser 11.

[0045] by Figure 1 Taking the orientation shown as an example, the first interface of the wavelength division multiplexer 41 is the upper end of the wavelength division multiplexer 41, the second interface of the wavelength division multiplexer 41 is the left end of the wavelength division multiplexer 41, and the third interface of the wavelength division multiplexer 41 is the lower end of the wavelength division multiplexer 41.

[0046] During use, the Rayleigh backscattered light in optical fiber 31, as well as the reflected light from Bragg grating 311 and pressure gauge 32, reaches wavelength division multiplexer 41 through circulator 20. Since the reflected wavelength of wavelength division multiplexer 41 corresponds to the preset wavelength λc of narrow linewidth laser 11, the Rayleigh backscattered light first reaches detection unit 42. Detection unit 42 converts the Rayleigh backscattered light into a digital signal and transmits the digital signal to computer 44 for data demodulation to obtain distributed acoustic wave signal in optical fiber 31. The direct light (i.e., reflected light) of wavelength division multiplexer 41 reaches spectrometer 43. The spectral signal obtained by spectrometer 43 is also transmitted to computer 44 for demodulation processing to obtain temperature and pressure values.

[0047] The detection unit 42 includes a photodetector 421 and a high-speed data acquisition card 422. The photodetector 421 is connected to the high-speed data acquisition card 422. The end of the high-speed data acquisition card 422 away from the photodetector 421 is connected to the computer 44. The end of the photodetector 421 away from the high-speed data acquisition card 422 is connected to the second interface of the wavelength division multiplexer 41.

[0048] During use, Rayleigh backscattered light first reaches photodetector 421 and is converted into an electrical signal, which is then acquired by high-speed data acquisition card 422 and converted into a digital signal. High-speed data acquisition card 422 transmits the digital signal to computer 44 for heterodyne data demodulation to obtain the distributed acoustic wave signal in optical fiber 31.

[0049] In this embodiment, the fiber optic sensing system 1 for synchronous measurement of multiple temperature, pressure, and acoustic parameters utilizes signals of different wavelengths to synchronously measure different physical quantities. The spectral range of the fiber optic sensing system 1 is [λ1, λ2], where λ1 < λ2. The wavelength range of the Bragg grating 311 is set to [λ1, λ3] (where λ1 < λ3 < λ2). The center wavelengths of multiple Bragg gratings 311 on the fiber 31 are all located within [λ1, λ3], thereby enabling temperature measurement at multiple points. The preset wavelength (i.e., center wavelength) λc of the narrow-linewidth laser 11 satisfies λ1 < λc < λ2. λc is the detection wavelength of Rayleigh backscattered light. Only the signal of wavelength λc is obtained through the reflection end of the wavelength division multiplexer 41. Heterodyne demodulation of this signal yields the distributed acoustic wave signal on the fiber 31. Among them, the pressure gauge 32 of the optical fiber 31 has a wavelength range of [λ3, λ2]. The pressure gauge 32 of the optical fiber 31 adopts the form of a Fabry-Poirot interferometer, and the pressure value can be obtained by using white light demodulation technology in the wavelength range of [λ3, λ2].

[0050] Continue to refer to Figure 1 and Figure 3 Another embodiment provides a measurement method for a fiber optic sensing system 1 for synchronous measurement of multiple temperature, pressure, and acoustic parameters, comprising the following steps:

[0051] S101, the optical output component 10 injects the output laser into the optical fiber 31 through the circulator 20.

[0052] S101, the optical output component 10, injects the output laser into the optical fiber 31 through the circulator 20, including: a narrow linewidth laser 11 outputs a narrow linewidth continuous laser with a preset wavelength λc, the narrow linewidth continuous laser reaches the acousto-optic modulator 1211 for pulse and frequency shift modulation, a first erbium-doped fiber amplifier generates spontaneous emission light, the output light of the acousto-optic modulator 1211 and the first erbium-doped fiber amplifier are combined by the fiber coupler 131 and then amplified by the second erbium-doped fiber amplifier, and the amplified light is injected into the optical fiber 31 through the circulator 20.

[0053] S102, the Rayleigh backscattered light in optical fiber 31, and the reflected light from Bragg grating 311 and pressure gauge 32 reach demodulation component 40 through circulator 20. Demodulation component 40 demodulates to obtain distributed acoustic signal, temperature value and pressure value.

[0054] Among them, the Rayleigh backscattered light in S102 and optical fiber 31, as well as the reflected light from Bragg grating 311 and pressure gauge 32, reach demodulation component 40 through circulator 20. Demodulation component 40 demodulates to obtain distributed acoustic signal, temperature value, and pressure value, including:

[0055] The Rayleigh backscattered light in S1021 and fiber 31, as well as the reflected light from Bragg grating 311 and pressure gauge 32, reach wavelength division multiplexer 41 through the third port of circulator 20.

[0056] S1022, Rayleigh backscattered light reaches photodetector 421 and is converted into an electrical signal. The electrical signal is acquired by high-speed data acquisition card 422 and converted into a digital signal. The digital signal is transmitted to computer 44 for heterodyne data demodulation to obtain distributed acoustic wave signal in optical fiber 31.

[0057] Specifically, since the reflected wavelength of the wavelength division multiplexer 41 corresponds to the preset wavelength λc of the narrow linewidth laser 11, the Rayleigh backscattered light first reaches the detection unit 42. The detection unit 42 converts the Rayleigh backscattered light into a digital signal and transmits the digital signal to the computer 44 for data demodulation to obtain the distributed acoustic wave signal in the optical fiber 31.

[0058] S1023, the reflected light reaches the spectrometer 43, and the spectral signal obtained by the spectrometer 43 is transmitted to the computer 44 for demodulation processing to obtain the temperature and pressure values.

[0059] Specifically, the direct light (i.e., reflected light) from the wavelength division multiplexer 41 reaches the spectrometer 43, and the spectral signal obtained by the spectrometer 43 is transmitted to the computer 44 for demodulation processing to obtain the temperature and pressure values.

[0060] Continue to refer to Figure 2 With λc = 1550nm, the starting wavelength of the spectrum λ1 = 1520nm, the ending wavelength λ2 = 1600nm, and λ3 = 1530nm, the wavelength range of the Bragg grating 311 is [1520nm, 1530nm]. The wavelength range of the pressure gauge 32 of the optical fiber 31 is [1530nm, ...]. Taking the Rayleigh backscattering detection wavelength of 1550nm as an example, the specific process of the optical fiber sensing system 1 for synchronous measurement of pressure sound multi-parameters is as follows: the Rayleigh backscattered light in the optical fiber 31 and the reflected light from the Bragg grating 311 and the pressure gauge 32 reach the wavelength division multiplexer 41 through the third port of the circulator 20. The reflection wavelength of the wavelength division multiplexer 41 is 1550nm, which corresponds to the preset wavelength of the narrow linewidth laser 11. The Rayleigh backscattered light first reaches the photodetector 421 and is converted into an electrical signal, and then is acquired by the high-speed data acquisition card 422 and converted into a digital signal. The high-speed data acquisition card 422 transmits the digital signal to the computer 44 for heterodyne data demodulation to obtain the distributed acoustic wave signal in the optical fiber 31.

[0061] In this process, the direct light (i.e., reflected light) from the wavelength division multiplexer 41 reaches the spectrometer 43, and the spectral signal obtained by the spectrometer 43 is transmitted to the computer 44 for demodulation processing to obtain the temperature and pressure values.

[0062] Specifically, the wavelength range of 1520nm to 1530nm contains reflected light from multiple Bragg gratings 311. Different Bragg gratings 311 are distinguished by their wavelength values, and the temperature value is obtained by observing the drift of the center wavelength of the Bragg grating 311 with temperature. The wavelength range of 1530nm to 1600nm is used to demodulate the pressure gauge 32 of the optical fiber 31. The pressure gauge 32 uses a Fabry-Poirot interferometer, and the pressure value can be obtained by using white light demodulation technology.

[0063] The measurement method of the fiber optic sensing system 1 for synchronous measurement of multiple parameters (temperature, pressure, and acoustic) provided in this application includes an optical output component 10, a circulator 20, an optical fiber component 30, and a demodulation component 40. The optical output component 10 is connected to the first port of the circulator 20, the optical fiber component 30 is connected to the second port of the circulator 20, and the demodulation component 40 is connected to the third port of the circulator 20. Multiple Bragg gratings 311 are etched on the optical fiber component 30, and the multiple Bragg gratings 311 are spaced apart along the extension direction of the optical fiber component 30. The tail end of the optical fiber component 30 is used for pressure measurement. The Bragg gratings on the optical fiber component 30... The grating 311 is used to achieve quasi-distributed temperature measurement; the Rayleigh backscattered light in the fiber optic assembly 30 is used to achieve distributed sound wave measurement; the measurement method is as follows: laser is injected into the fiber optic 31 and demodulated to obtain distributed sound wave signals, temperature values, and pressure values; by setting the fiber optic assembly 30, compared with the traditional sensing system, the tail end of the fiber optic assembly 30 achieves pressure measurement; the Bragg grating 311 achieves quasi-distributed temperature measurement; the Rayleigh backscattered light is used to achieve distributed sound wave measurement, thereby reducing the construction difficulty; at the same time, when monitoring natural gas hydrate production wells in situ, the installation difficulty is reduced and the installation efficiency is improved.

[0064] The fiber optic sensing system 1 for synchronous measurement of temperature, pressure, and acoustic parameters provided by this invention has the following advantages: the system has a simple structure, is easy to manufacture, and is easy to install.

[0065] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0066] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters, characterized in that: This includes optical output components, circulators, fiber optic components, and demodulation components; The optical output component is connected to the first port of the circulator, the optical fiber component is connected to the second port of the circulator, and the demodulation component is connected to the third port of the circulator; The optical fiber assembly is provided with a plurality of Bragg gratings, and the plurality of Bragg gratings are spaced apart along the extension direction of the optical fiber assembly; The tail end of the optical fiber assembly is used to measure pressure. The Bragg grating on the optical fiber assembly is used to achieve quasi-distributed temperature measurement; Rayleigh backscattered light in the optical fiber assembly is used to achieve distributed measurement of acoustic waves. The optical fiber assembly includes an optical fiber and a pressure gauge. One end of the optical fiber is connected to the second port of the circulator, and the other end of the optical fiber is connected to the pressure gauge. A plurality of Bragg gratings are etched on the optical fiber, and the plurality of Bragg gratings are spaced apart along the extension direction of the optical fiber. The pressure gauge is used to measure pressure; Rayleigh backscattered light in the optical fiber is used to achieve distributed measurement of sound waves; The optical output component includes a narrow linewidth laser, a modulation unit, and a coupling unit. The narrow linewidth laser is connected to the modulation unit. One end of the modulation unit away from the narrow linewidth laser is connected to the coupling unit. One end of the coupling unit away from the modulation unit is connected to the first port of the circulator. The narrow linewidth laser is used to output narrow linewidth continuous laser with a preset wavelength; The demodulation component includes a wavelength division multiplexer, a detection unit, a spectrometer, and a computer. The first interface of the wavelength division multiplexer is connected to the third port of the circulator, the second interface of the wavelength division multiplexer is connected to the detection unit, and the end of the detection unit facing away from the wavelength division multiplexer is connected to the computer. The third interface of the wavelength division multiplexer is connected to the spectrometer, and the end of the spectrometer facing away from the wavelength division multiplexer is connected to the computer; The reflected wavelength of the wavelength division multiplexer corresponds to the preset wavelength λc of the narrow linewidth laser; The spectral range of the fiber optic sensing system is [λ1, λ2], where λ1 < λ2. The wavelength range of the Bragg grating is set to [λ1, λ3], where λ1 < λ3 < λ2. The center wavelengths of multiple Bragg gratings on the fiber are all within [λ1, λ3], thus enabling temperature measurement at multiple points. The preset wavelength, i.e., the center wavelength λc, of the narrow-linewidth laser satisfies λ1 < λc < λ2. λc is the detection wavelength of Rayleigh backscattered light. Only the signal of wavelength λc is obtained through the reflection end of the wavelength division multiplexer. Heterodyne demodulation of this signal yields the distributed acoustic wave signal on the fiber. The wavelength range of the fiber optic pressure gauge is [λ3, λ2]. The fiber optic pressure gauge adopts the form of a Fabry-Poirot interferometer, and the pressure value can be obtained using white light demodulation technology within the wavelength range of [λ3, λ2].

2. The fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters according to claim 1, characterized in that: The modulation unit includes a modulation module and a first erbium-doped fiber amplifier. The narrow linewidth laser is connected to the modulation module, and both the modulation module and the first erbium-doped fiber amplifier are connected to the coupling unit.

3. The fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters according to claim 2, characterized in that: The modulation module includes an acousto-optic modulator and a radio frequency driver. The narrow linewidth laser is connected to the first end of the acousto-optic modulator, the radio frequency driver is connected to the second end of the acousto-optic modulator, and the third end of the acousto-optic modulator and the first erbium-doped fiber amplifier are both connected to the coupling unit. The radio frequency driver is used to control the operating state of the acousto-optic modulator.

4. The fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters according to claim 3, characterized in that: The coupling unit includes an optical fiber coupler and a second erbium-doped optical fiber amplifier. The optical fiber coupler is connected to the second erbium-doped optical fiber amplifier, and the end of the second erbium-doped optical fiber amplifier facing away from the optical fiber coupler is connected to the first port of the circulator. The third end of the acousto-optic modulator and the first erbium-doped fiber amplifier are both connected to the end of the fiber coupler that is away from the second erbium-doped fiber amplifier.

5. The fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters according to claim 4, characterized in that: The detection unit includes a photodetector and a high-speed data acquisition card. The photodetector is connected to the high-speed data acquisition card. The end of the high-speed data acquisition card away from the photodetector is connected to the computer. The end of the photodetector away from the high-speed data acquisition card is connected to the second interface of the wavelength division multiplexer.

6. A measurement method using the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters as described in claim 5, characterized in that: Includes the following steps: The optical output component injects the output laser into the optical fiber through the circulator; Rayleigh backscattered light in the optical fiber, as well as the reflected light from the Bragg grating and the pressure gauge, reaches the demodulation component through the circulator. The demodulation component demodulates the distributed acoustic signal, temperature value, and pressure value.

7. The measurement method of the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters according to claim 6, characterized in that: The optical output component injects the output laser into the optical fiber through the circulator, including: The narrow linewidth laser outputs a narrow linewidth continuous laser with a preset wavelength. The narrow linewidth continuous laser reaches the acousto-optic modulator for pulse and frequency shift modulation. The first erbium-doped fiber amplifier generates spontaneous emission light. The output light of the acousto-optic modulator and the first erbium-doped fiber amplifier are combined by the fiber coupler and then amplified by the second erbium-doped fiber amplifier. The amplified light is injected into the fiber through the circulator.

8. The measurement method of the fiber optic sensing system for synchronous measurement of multiple temperature, pressure, and acoustic parameters according to claim 7, characterized in that: Rayleigh backscattered light in the optical fiber, as well as the reflected light from the Bragg grating and the pressure gauge, reaches the demodulation component through the circulator. The demodulation component demodulates the distributed acoustic signal, temperature value, and pressure value, including: Rayleigh backscattered light in the optical fiber, as well as the reflected light from the Bragg grating and the pressure gauge, reaches the wavelength division multiplexer through the third port of the circulator; The Rayleigh backscattered light reaches the photodetector and is converted into an electrical signal. The electrical signal is acquired by the high-speed data acquisition card and converted into a digital signal. The digital signal is transmitted to the computer for heterodyne demodulation to obtain the distributed acoustic wave signal in the optical fiber. The reflected light reaches the spectrometer, and the spectral signal obtained by the spectrometer is transmitted to the computer for demodulation processing to obtain the temperature value and the pressure value.

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