Optical fiber sensing system for temperature, pressure and sound multi-parameter synchronous measurement and measurement method

Abstract

The invention relates to an optical fiber sensing system for temperature, pressure and sound multi-parameter synchronous measurement and a measurement method. The optical fiber sensing system comprises a light output assembly, a circulator, an optical fiber assembly and a demodulation assembly. The optical output assembly is connected with a first port of the circulator, the optical fiber assembly is connected with a second port of the circulator, and the demodulation assembly is connected with a third port of the circulator; a plurality of Bragg gratings are carved on the optical fiber assembly; the measuring method comprises the following steps of: injecting laser into the optical fiber and demodulating to obtain a distributed acoustic signal, a temperature value and a pressure value; by arranging the optical fiber assembly, compared with a traditional sensing system, pressure measurement is achieved at the tail end of the optical fiber assembly; the Bragg grating realizes quasi-distributed measurement of the temperature; rayleigh backscattered light is used for realizing distributed measurement of sound waves, so that the construction difficulty is reduced; and meanwhile, during in-situ monitoring of the natural gas hydrate production well, the installation difficulty is reduced, and the installation efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to an optical fiber sensing system and a measuring method for synchronously measuring multiple parameters of temperature, pressure and sound. Background Art

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

[0003] Specifically, changes in saturation during hydrate production can lead to changes in key geophysical properties of the reservoir, such as temperature, pressure, acoustic response, and mechanical properties. Using these physical property characteristics, geophysical means can be used to remotely measure, monitor, and warn of changes in the properties of hydrate reservoirs and possible environmental impacts such as surface deformation.

[0004] However, currently, independent sensors are used to monitor temperature, pressure and sound waves. In order to achieve simultaneous measurement of the three, the three sensors need to be used in combination, which increases the difficulty of construction. In addition, the in-situ monitoring of natural gas hydrate production wells increases the difficulty of installation. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a fiber optic sensing system and measurement method for synchronous measurement of temperature, pressure and acoustic multi-parameters, which has the advantage of reducing the difficulty of construction; at the same time, during the in-situ monitoring of natural gas hydrate production wells, the installation efficiency is improved and the installation difficulty is reduced.

[0006] The above-mentioned inventive object of the present invention is achieved through the following technical solutions: On the one hand, the present invention provides an optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters, including 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; a plurality of Bragg gratings are engraved on the optical fiber component, and the plurality of Bragg gratings are arranged at intervals 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 grating on the optical fiber component is used to realize quasi-distributed measurement of temperature; and the Rayleigh backscattered light in the optical fiber component is used to realize distributed measurement of sound waves.

[0007] Preferably, in the fiber optic sensing system for simultaneous measurement of multiple parameters of temperature, pressure and sound provided by the present invention, the fiber optic 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 the Bragg gratings are engraved on the optical fiber, and the plurality of the Bragg gratings are arranged at intervals along the extension direction of the optical fiber; the pressure gauge is used to measure pressure; and the Rayleigh backscattered light in the optical fiber is used to achieve distributed measurement of sound waves.

[0008] Preferably, in the fiber optic sensing system for simultaneous measurement of multiple parameters of temperature, pressure and sound provided by the present invention, 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, the end of the modulation unit facing away from the narrow linewidth laser is connected to the coupling unit, and the end of the coupling unit facing 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 of a preset wavelength.

[0009] Preferably, in the fiber optic sensing system for simultaneous measurement of temperature, pressure and acoustic multi-parameters provided by the present invention, 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 the modulation module and the first erbium-doped fiber amplifier are both connected to the coupling unit.

[0010] Preferably, in the fiber optic sensing system for synchronous measurement of temperature, pressure and acoustic multi-parameters provided by the present invention, 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, 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, in the fiber optic sensing system for simultaneous measurement of multiple parameters of temperature, pressure and sound provided by the present invention, the coupling unit includes 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, in the optical fiber sensing system for synchronous measurement of multiple parameters of temperature, pressure and sound provided by the present invention, 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.

[0013] Preferably, in the optical fiber sensing system for synchronous measurement of multiple parameters of temperature, pressure and sound provided by the present invention, the detection unit includes a photoelectric detector and a high-speed data acquisition card, the photoelectric detector is connected to the high-speed data acquisition card, the end of the high-speed data acquisition card away from the photoelectric detector is connected to the computer, and the end of the photoelectric detector 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 method for measuring a fiber optic sensing system for synchronously measuring temperature, pressure and sound multi-parameters, comprising the following steps:

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

[0016] The Rayleigh backscattered light in the optical fiber and the reflected light of the Bragg grating and the pressure gauge reach the demodulation component through the circulator, and the demodulation component demodulates to obtain a distributed acoustic wave signal, a temperature value, and a pressure value.

[0017] Preferably, the measurement method of the optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters provided by the present invention, the optical output component injects the output laser into the optical fiber through the circulator, including: the narrow-linewidth laser outputs 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 radiation light, the output light of the acousto-optic modulator and the first erbium-doped fiber amplifier is combined by the optical 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 optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters provided by the present invention, the Rayleigh backscattered light in the optical fiber and the reflected light of the Bragg grating and the pressure gauge reach the demodulation component through the circulator, and the demodulation component demodulates to obtain a distributed sound wave signal, a temperature value and a pressure value, including:

[0019] The Rayleigh backscattered light in the optical fiber and the reflected light of the Bragg grating and the pressure gauge reach the wavelength division multiplexer through the third port of the circulator;

[0020] The Rayleigh backscattered light reaches the photoelectric detector and is converted into an electrical signal, the electrical signal is collected by the high-speed data acquisition card and converted into a digital signal, the digital signal is transmitted to the computer for heterodyne data demodulation, and a distributed acoustic wave signal in the optical fiber is obtained;

[0021] The reflected light reaches the spectrometer, and the spectrum 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 the present invention are as follows: the present application provides an optical fiber sensing system and a measuring method for synchronously measuring multiple parameters of temperature, pressure and sound, wherein the optical fiber sensing system comprises 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; a plurality of Bragg gratings are engraved on the optical fiber component, and the plurality of Bragg gratings are arranged at intervals 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 measurement of temperature; the Rayleigh backscattered light in the optical fiber component is used to realize distributed measurement of sound waves; the measuring 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 measurement of temperature; the Rayleigh backscattered light is used to realize distributed measurement of sound waves, thereby reducing the construction difficulty; at the same time, when monitoring the natural gas hydrate production well in situ, the installation difficulty is reduced and the installation efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of an optical fiber sensing system for synchronously measuring multiple parameters of temperature, pressure and sound provided in an embodiment of the present invention.

[0024] Figure 2 It is a spectrum diagram of a fiber optic sensing system for synchronous measurement of temperature, pressure and sound multi-parameters provided by another embodiment of the present invention.

[0025] Figure 3 It is a flow chart of a measurement method of an optical fiber sensing system for synchronously measuring temperature, pressure and sound multiple parameters provided by another embodiment of the present invention.

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

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0028] Reference Figure 1 , is a fiber optic sensing system 1 for synchronous measurement of temperature, pressure and sound multi-parameters disclosed in the present invention, 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 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; a plurality of Bragg gratings 311 are engraved on the optical fiber component 30, and the plurality of Bragg gratings 311 are arranged at intervals along the extension direction of the optical fiber component 30; the tail end of the optical fiber component 30 is used to measure pressure; the Bragg gratings 311 on the optical fiber component 30 1 is used to realize quasi-distributed measurement of temperature; Rayleigh backscattered light in the optical fiber assembly 30 is used to realize distributed measurement of sound waves; by setting the optical fiber assembly 30, compared with the traditional sensing system, the tail end of the optical fiber assembly 30 realizes pressure measurement; the Bragg grating 311 realizes quasi-distributed measurement of temperature; Rayleigh backscattered light is used to realize distributed measurement of sound waves, thereby reducing the difficulty of construction; at the same time, when monitoring the natural gas hydrate production well in situ, the optical fiber assembly 30 is small in size and is easy to be installed between the production pipe string and the casing, thereby reducing the difficulty of installation and improving the installation efficiency.

[0029] It should be noted that Figure 1 Taking the shown orientation 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 lower end of the circulator 20; the tail end of the optical fiber assembly 30 is the right end of the optical fiber assembly 30.

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

[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, and a plurality of Bragg gratings 311 are engraved on the optical fiber 31, and the plurality of Bragg gratings 311 are arranged at intervals along the extension direction of the optical fiber 31; the pressure gauge 32 is used to realize pressure measurement; and the Rayleigh backscattered light in the optical fiber 31 is used to realize distributed measurement of sound waves.

[0032] Specifically, Figure 1 Taking the shown orientation 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 and the reflected light of the Bragg grating 311 and the pressure gauge 32 reach the demodulation component 40 through the circulator 20.

[0034] Exemplarily, the optical fiber 31 may be a common single-mode optical fiber. Of course, the optical fiber 31 may also be other types of optical fibers.

[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, the end of the modulation unit 12 away from the narrow linewidth laser 11 is connected to the coupling unit 13, and the 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 narrow-linewidth continuous laser light of a preset wavelength λc, and the narrow-linewidth connection laser light 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 the modulation module 121 and the first erbium-doped fiber amplifier are both connected to the coupling unit 13 .

[0038] During use, the narrow-linewidth laser 11 outputs a narrow-linewidth continuous laser of 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 radiation light, and the output light of the modulation module 121 and the first erbium-doped fiber amplifier (that is, the narrow-linewidth connecting laser after pulse and frequency shift modulation output by the modulation module 121 and the radiation light output by the first erbium-doped fiber amplifier) ​​is combined and amplified by the coupling unit 13, and then injected into the optical 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 of a preset wavelength λc, the narrow-linewidth connecting laser reaches the acousto-optic modulator 1211 for pulse and frequency shift modulation, the first erbium-doped fiber amplifier generates spontaneous radiation light, and 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 optical fiber 31 through the circulator 20.

[0041] Continue to refer to Figure 1 In this embodiment, the coupling unit 13 includes a fiber coupler 131 and a second erbium-doped fiber amplifier, the fiber coupler 131 is connected to the second erbium-doped fiber amplifier, and the end of the second erbium-doped fiber amplifier away from the 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 fiber amplifier are both connected to the end of the fiber coupler 131 away from the second erbium-doped fiber amplifier.

[0042] During use, the output light of the AOM 1211 and the first EDF amplifier is combined by the fiber coupler 131 , amplified by the second EDF amplifier, and then injected into the optical 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 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 away from the wavelength division multiplexer 41 is connected to the computer 44.

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

[0045] by Figure 1 Taking the shown orientation 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 the optical fiber 31 and the reflected light of the Bragg grating 311 and the pressure gauge 32 reach the wavelength division multiplexer 41 through the circulator 20. Since the reflection 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, and the detection unit 42 finally converts the Rayleigh backscattered light into a digital signal. The detection unit 42 transmits the digital signal to the computer 44 for data demodulation to obtain the distributed acoustic wave signal in the optical fiber 31; the direct light (i.e., the reflected light) of the wavelength division multiplexer 41 reaches the spectrometer 43, and the spectral signal obtained by the spectrometer 43 is also transmitted to the computer 44 for demodulation processing to obtain the temperature value and the pressure value.

[0047] 8. The optical fiber sensing system 1 for synchronous measurement of multiple parameters of temperature, pressure and sound according to claim 7 is characterized in that: 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, and 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, the Rayleigh backscattered light first reaches the photodetector 421 and is converted into an electrical signal, and then is collected 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 a distributed acoustic wave signal in the optical fiber 31.

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

[0050] Continue to refer to Figure 1 and Figure 3 Another embodiment provides a method for measuring a temperature, pressure, and sound multi-parameter synchronous measurement using an optical fiber sensing system 1, 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] Among them, S101, the optical output component 10 injects the output laser into the optical fiber 31 through the circulator 20, including: the 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, the first erbium-doped fiber amplifier generates spontaneous radiation light, the output light of the acousto-optic modulator 1211 and the first erbium-doped fiber amplifier is combined by the optical fiber coupler 131 and 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 the optical fiber 31, and the reflected light of the Bragg grating 311 and the pressure gauge 32 reach the demodulation component 40 through the circulator 20, and the demodulation component 40 demodulates to obtain the distributed acoustic wave signal, temperature value and pressure value.

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

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

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

[0057] Specifically, since the reflection 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, and the detection unit 42 finally converts the Rayleigh backscattered light into a digital signal. The detection unit 42 transmits the digital signal to the computer 44 for data demodulation to obtain a distributed acoustic wave signal in the optical fiber 31.

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

[0059] Specifically, the direct light (ie, the reflected light) of the wavelength division multiplexer 41 reaches the spectrometer 43 , and the spectrum signal obtained by the spectrometer 43 is transmitted to the computer 44 for demodulation processing to obtain the temperature value and the pressure value.

[0060] Continue to refer to Figure 2 , taking λc=1550nm, the starting wavelength λ1=1520nm, the ending wavelength λ2=1600nm, and λ3=1530nm, that is, 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, 1600nm], and the detection wavelength of Rayleigh backscattering is 1550nm as an example, the specific process of the optical fiber sensing system 1 for synchronous measurement of pressure and sound multi-parameters is as follows: the Rayleigh backscattered light in the optical fiber 31 is The reflected light of the Bragg grating 311 and the pressure gauge 32 reaches the wavelength division multiplexer 41 through the third port of the circulator 20. The reflection wavelength of the wavelength division multiplexer 41 is 1550nm, corresponding 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 collected 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] The direct light (ie, the reflected light) of the wavelength division multiplexer 41 reaches the spectrometer 43 , and the spectrum signal obtained by the spectrometer 43 is transmitted to the computer 44 for demodulation processing to obtain the temperature value and the pressure value.

[0062] Specifically, the wavelength range of 1520nm to 1530nm includes reflected light of multiple Bragg gratings 311. Different Bragg gratings 311 are distinguished by wavelength values, and the temperature value is obtained by the fluctuation of the central wavelength of the Bragg grating 311 with temperature. The wavelength range of 1530nm to 1600nm realizes the demodulation of the pressure gauge 32 of the optical fiber 31. The pressure gauge 32 adopts a Fabry-Perot interferometer, and the pressure value can be obtained by using white light demodulation technology.

[0063] The present application provides a measurement method of an optical fiber sensing system 1 for synchronous measurement of temperature, pressure and sound multi-parameters, wherein the optical fiber sensing system 1 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; a plurality of Bragg gratings 311 are engraved on the optical fiber component 30, and the plurality of Bragg gratings 311 are arranged at intervals along the extension direction of the optical fiber component 30; the tail end of the optical fiber component 30 is used to realize pressure measurement; the Bragg gratings on the optical fiber component 30 The grating 311 is used to realize quasi-distributed measurement of temperature; the Rayleigh backscattered light in the optical fiber assembly 30 is used to realize distributed measurement of sound waves; the measurement method is: laser is injected into the optical fiber 31 - demodulation is performed to obtain distributed sound wave signals, temperature values ​​and pressure values; by setting the optical fiber assembly 30, compared with the traditional sensing system, the tail end of the optical fiber assembly 30 realizes pressure measurement; the Bragg grating 311 realizes quasi-distributed measurement of temperature; the Rayleigh backscattered light is used to realize distributed measurement of sound waves, thereby reducing the difficulty of construction; at the same time, when conducting in-situ monitoring of natural gas hydrate production wells, the installation difficulty is reduced and the installation efficiency is improved.

[0064] The optical fiber sensing system 1 for synchronous measurement of temperature, pressure and sound multi-parameters provided by the present invention has the following advantages: the system has a simple structure, is easy to manufacture and is convenient to install.

[0065] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0066] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present invention.

Claims

1. An optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters, characterized in that: It includes 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; A plurality of Bragg gratings are engraved on the optical fiber component, and the plurality of Bragg gratings are arranged at intervals along the extension direction of the optical fiber component; 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 measurement of temperature; The Rayleigh backscattered light in the optical fiber assembly is used to realize the distributed measurement of the acoustic wave.

2. The optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters according to claim 1 is characterized in that: 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 engraved on the optical fiber, and the plurality of Bragg gratings are arranged at intervals along the extension direction of the optical fiber; The pressure gauge is used to measure the pressure; The Rayleigh backscattered light in the optical fiber is used to realize the distributed measurement of the acoustic wave.

3. The optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters according to claim 1 is characterized in that: The optical output assembly comprises a narrow linewidth laser, a modulation unit and a coupling unit, wherein the narrow linewidth laser is connected to the modulation unit, an end of the modulation unit away from the narrow linewidth laser is connected to the coupling unit, and an 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 light of a preset wavelength.

4. The optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters according to claim 3 is characterized in that: The modulation unit comprises 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.

5. The optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters according to claim 4 is characterized in that: The modulation module includes an acousto-optic modulator and a radio frequency driver, the narrow line width 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.

6. The optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters according to claim 5 is characterized in that: The coupling unit comprises a fiber coupler and a second erbium-doped fiber amplifier, the fiber coupler is connected to the second erbium-doped fiber amplifier, and one end of the second erbium-doped fiber amplifier away from the fiber coupler is connected to the first port of the circulator; The third end of the AOM and the first EDF amplifier are both connected to an end of the fiber coupler away from the second EDF amplifier.

7. The optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters according to claim 1, characterized in that: The demodulation component includes a wavelength division multiplexer, a detection unit, a spectrometer and a computer, wherein 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 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 one end of the spectrometer away from the wavelength division multiplexer is connected to the computer.

8. The optical fiber sensing system for synchronous measurement of temperature, pressure and sound multi-parameters according to claim 7, characterized in that: The detection unit includes a photoelectric detector and a high-speed data acquisition card, the photoelectric detector is connected to the high-speed data acquisition card, one end of the high-speed data acquisition card away from the photoelectric detector is connected to the computer, and one end of the photoelectric detector away from the high-speed data acquisition card is connected to the second interface of the wavelength division multiplexer.

9. A method for measuring a temperature, pressure and sound multi-parameter synchronous measurement using an optical fiber sensing system, characterized in that: The following steps are involved: The optical output component injects the output laser into the optical fiber through the circulator; The Rayleigh backscattered light in the optical fiber and the reflected light of the Bragg grating and the pressure gauge reach the demodulation component through the circulator, and the demodulation component demodulates to obtain a distributed acoustic wave signal, a temperature value, and a pressure value.

10. The measuring method of the optical fiber sensing system for synchronously measuring temperature, pressure and sound multi-parameters according to claim 9, characterized in that: The optical output component injects the output laser into the optical fiber through the circulator, comprising: The narrow linewidth laser outputs narrow linewidth continuous laser of preset wavelength, and the narrow linewidth continuous laser reaches the acousto-optic modulator for pulse and frequency shift modulation. The first erbium-doped fiber amplifier generates spontaneous radiation light. The output light of the acousto-optic modulator and the first erbium-doped fiber amplifier is combined by the fiber coupler and amplified by the second erbium-doped fiber amplifier. The amplified light is injected into the optical fiber through the circulator.

11. The measuring method of the optical fiber sensing system for synchronously measuring temperature, pressure and sound multi-parameters according to claim 10, characterized in that: The Rayleigh backscattered light in the optical fiber and the reflected light of the Bragg grating and the pressure gauge reach the demodulation component through the circulator, and the demodulation component demodulates to obtain a distributed acoustic wave signal, a temperature value, and a pressure value, including: The Rayleigh backscattered light in the optical fiber and the reflected light of the Bragg grating and the pressure gauge reach the wavelength division multiplexer through the third port of the circulator; The Rayleigh backscattered light reaches the photoelectric detector and is converted into an electrical signal, the electrical signal is collected by the high-speed data acquisition card and converted into a digital signal, the digital signal is transmitted to the computer for heterodyne data demodulation, and a distributed acoustic wave signal in the optical fiber is obtained; The reflected light reaches the spectrometer, and the spectrum 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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