WO2023160079A1 - Dispositif de mesure de concentration de gaz et procédé de mesure de concentration de gaz - Google Patents

Dispositif de mesure de concentration de gaz et procédé de mesure de concentration de gaz Download PDF

Info

Publication number
WO2023160079A1
WO2023160079A1 PCT/CN2022/135178 CN2022135178W WO2023160079A1 WO 2023160079 A1 WO2023160079 A1 WO 2023160079A1 CN 2022135178 W CN2022135178 W CN 2022135178W WO 2023160079 A1 WO2023160079 A1 WO 2023160079A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical fiber
light
signal
gas
detection
Prior art date
Application number
PCT/CN2022/135178
Other languages
English (en)
Chinese (zh)
Inventor
罗海鹏
李锋
Original Assignee
华为技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Publication of WO2023160079A1 publication Critical patent/WO2023160079A1/fr

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N2021/0106—General arrangement of respective parts
    • G01N2021/0112—Apparatus in one mechanical, optical or electronic block
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Definitions

  • the present application relates to the field of gas sensors, in particular to a gas concentration detection device and a gas concentration detection method.
  • High-precision gas sensors are widely used in many fields such as petroleum, coal mines, chemical industry, mining, metallurgy, power plants, substations, and atmospheric monitoring.
  • Current solutions usually use single-point gas sensors, such as methane gas sensors based on tunable diode laser absorption spectroscopy (Tunable Diode Laser Absorption Spectrum, TDLAS), which use the characteristics of narrow linewidth and wavelength of tunable semiconductor lasers that change with injection current , to achieve the measurement of single or several absorption lines that are very close and difficult to distinguish.
  • TDLAS tunable Diode Laser Absorption Spectrum
  • the application provides a gas concentration detection device and a gas concentration detection method, the system structure is simpler, and it is convenient to realize multi-point deployment and monitoring.
  • the embodiment of the present application provides a gas concentration detection device.
  • the gas concentration detecting device includes: a signal emitting device, an optical fiber sensing device and a signal processing device.
  • the optical fiber sensing device includes an optical fiber and at least one air hole on the optical fiber, and the gas to be measured enters the optical fiber through the air hole.
  • the signal transmitting device is used for outputting the detection signal to the optical fiber.
  • the detection signal includes pump light, the wavelength of the pump light is periodically tuned, and the pump light has an oscillation frequency.
  • the signal processing device is used to receive the echo signal of the detection signal reflected at the air hole, determine the amplitude of the oscillation frequency according to the echo signal, and determine the concentration of the gas to be measured according to the amplitude of the oscillation frequency.
  • a distributed gas concentration detection device based on optical fiber sensing is provided, and the optical fiber can be extended and deployed close to the area to be measured (such as an oil and gas pipeline).
  • one or more air holes may be opened on the optical fiber to facilitate the free diffusion of gas into the optical fiber.
  • the position of each air hole on the optical fiber can be used as a gas sensor. All gas sensors share a set of signal transmitting device and signal processing device.
  • the system structure is simpler and it is convenient for multi-point deployment and monitoring.
  • the signal transmitting device and the signal processing device can be placed in the remote computer room, far away from the area to be tested, and the security is better.
  • the signal transmitting device includes a pumping light source, a laser and a pulsed light generator.
  • the pump light source is used to output pump light to the optical fiber.
  • the laser is used to output the first light beam to the pulsed light generator, and output the second light beam to the signal processing device.
  • the pulsed light generator is used for generating pulsed detection light according to the first light beam, and outputting the pulsed detection light to the optical fiber.
  • the detection signal includes pump light and pulsed detection light.
  • the signal processing module includes a coherent demodulation module and a lock-in amplification module.
  • the echo signal includes pulsed probe light reflected at the air hole.
  • the coherent demodulation module is used to coherently demodulate the echo signal according to the second light beam to obtain the phase of the echo signal.
  • the lock-in amplification module is used to determine the amplitude of the oscillation frequency according to the phase of the echo signal, and determine the concentration of the gas to be measured according to the amplitude of the oscillation frequency.
  • a specific implementation of the signal processing module is provided, which uses an optical coherent demodulation method, which can more effectively amplify the gas absorption phase, so it can also be detected when the gas concentration value is very low.
  • the concentration range of the gas is larger.
  • this kind of photothermal detection does not need to limit the working wavelength of the photodetector, and has a higher tolerance for the photodetector.
  • the signal transmitting device includes a pumping light source and a pulsed light generator.
  • the pump light source is used to output pump light to the pulse light generator.
  • the pulse light generator is used to generate pulse probe light according to the pump light, and output the pulse probe light to the optical fiber.
  • the detection signal includes pulsed detection light.
  • the signal processing module includes a photodetector and a lock-in amplifier module.
  • the echo signal includes pulsed probe light reflected at the air hole.
  • a photodetector is used to detect the strength of the echo signal.
  • the lock-in amplification module is used to determine the amplitude of the oscillation frequency according to the intensity of the echo signal, and determine the concentration of the gas to be measured according to the amplitude of the oscillation frequency.
  • another specific implementation of the signal processing module is provided. The amplitude of the oscillation frequency is determined by detecting the intensity of the echo signal, and then the concentration of the gas to be measured is determined according to the amplitude of the oscillation frequency, which improves the The flexibility of the program.
  • this implementation method uses fewer components, the system is simpler, and the cost is lower.
  • the signal processing device is also used to determine the position of the gas to be measured according to the echo signal, so as to know the gas concentration at different monitoring positions.
  • the optical fiber is a hollow-core optical fiber.
  • the hollow-core optical fiber is characterized in that the center of the optical fiber is a hollow-core structure, and the gas can be pressurized or freely diffused into the hollow-core optical fiber.
  • the diameter, its special optical waveguide structure limits the radial diffusion of the light field in terms of electromagnetic characteristics, and the transmission of the light field in the hollow core enhances the interaction with the gas, so it can be applied to gas sensing and monitoring.
  • the optical fiber sensing device further includes at least one coupler, the optical fiber includes a trunk fiber and at least one branch fiber, the branch fiber is connected to the trunk fiber through the coupler, and the coupler is used to detect the detection signal transmitted in the trunk fiber Splitting is performed to obtain the first detection signal and the second detection signal.
  • the first detection signal continues to be transmitted along the trunk fiber, and the second detection signal is transmitted along the branch fiber.
  • the trunk fiber is a solid core fiber
  • the branch fiber includes a solid core fiber and a hollow core fiber, the air hole is located on the hollow core fiber.
  • the optical fiber includes a solid-core optical fiber and a hollow-core optical fiber, the solid-core optical fiber and the hollow-core optical fiber are connected in series, and the air hole is located on the hollow-core optical fiber. It should be noted that, since the cost of solid-core optical fiber is lower than that of hollow-core optical fiber, this embodiment can only use hollow-core optical fiber in a section adjacent to the area to be tested, and use solid-core optical fiber in other areas, which can effectively save costs.
  • the types of hollow-core fibers include anti-resonant hollow-core fibers, hollow-core photonic bandgap fibers, and hollow fibers, which improves the scalability of the solution.
  • the embodiment of the present application provides a method for detecting a gas concentration.
  • the detection method of the gas concentration comprises the following steps. First, a detection signal is output to an optical fiber.
  • the detection signal includes pump light, the wavelength of the pump light is periodically tuned, and the pump light has an oscillation frequency.
  • the optical fiber includes at least one air hole, and the gas to be measured enters the optical fiber through the air hole. Afterwards, an echo signal in which the detection signal is reflected at the air hole is received. Furthermore, the amplitude of the oscillation frequency is determined according to the echo signal, and the concentration of the gas to be measured is determined according to the amplitude of the oscillation frequency.
  • outputting the detection signal to the optical fiber includes: generating pump light, and outputting the pump light to the optical fiber. Generate pulsed probe light from the first beam from the laser, and output the pulsed probe light to the optical fiber.
  • the detection signal includes pump light and pulsed detection light.
  • determining the amplitude of the oscillation frequency according to the echo signal includes: coherently demodulating the echo signal according to the second beam from the laser to obtain the phase of the echo signal.
  • the amplitude of the oscillation frequency is determined according to the phase of the echo signal.
  • outputting the detection signal to the optical fiber includes: generating pump light, and generating pulsed detection light according to the pump light.
  • the pulsed detection light is output to the optical fiber, wherein the detection signal includes the pulsed detection light.
  • determining the amplitude of the oscillation frequency according to the echo signal includes: detecting the strength of the echo signal.
  • the amplitude of the oscillation frequency is determined according to the strength of the echo signal.
  • the method further includes: determining the position of the gas to be measured according to the echo signal.
  • the optical fiber is a hollow core optical fiber.
  • the optical fiber includes a trunk fiber and at least one branch fiber
  • the branch fiber is connected to the trunk fiber through a coupler
  • the detection signal transmitted in the trunk fiber is split to obtain the first detection signal and the second detection signal
  • the first detection signal continues to transmit along the trunk fiber
  • the second detection signal transmits along the branch fiber
  • the trunk fiber is a solid-core fiber
  • the branch fiber includes a solid-core fiber and a hollow-core fiber
  • the air hole is located on the hollow-core fiber.
  • the optical fiber includes a solid-core optical fiber and a hollow-core optical fiber, the solid-core optical fiber and the hollow-core optical fiber are connected in series, and the air hole is located on the hollow-core optical fiber.
  • the types of hollow-core fibers include anti-resonant hollow-core fibers, hollow-core photonic bandgap fibers, and hollow fibers.
  • a distributed gas concentration detection device based on optical fiber sensing
  • the optical fiber can be extended to be deployed close to the area to be measured (such as an oil and gas pipeline).
  • one or more air holes may be opened on the optical fiber to facilitate the free diffusion of gas into the optical fiber.
  • the signal transmitting device in the gas concentration detection device is used to output a detection signal to the optical fiber, the detection signal includes pump light, and the pump light is absorbed by the gas to be measured to produce a change in refractive index, thereby causing a change in the intensity of the echo signal and phase changes.
  • the wavelength of the pump light is periodically tuned and the pump light has an oscillation frequency.
  • the signal processing device receives the echo signal reflected by the detection signal at the air hole, first determines the amplitude of the oscillation frequency according to the echo signal, and then determines the concentration of the gas to be measured according to the amplitude of the oscillation frequency.
  • a distributed gas concentration detection device based on optical fiber sensing
  • the optical fiber can be extended to be deployed close to the area to be measured (such as an oil and gas pipeline).
  • one or more air holes may be opened on the optical fiber to facilitate the free diffusion of gas into the optical fiber.
  • the signal transmitting device in the gas concentration detection device is used to output a detection signal to the optical fiber, the detection signal includes pump light, and the pump light is absorbed by the gas to be measured to produce a change in refractive index, thereby causing a change in the intensity of the echo signal and phase changes.
  • the wavelength of the pump light is periodically tuned and the pump light has an oscillation frequency.
  • the signal processing device receives the echo signal reflected by the detection signal at the air hole, first determines the amplitude of the oscillation frequency according to the echo signal, and then determines the concentration of the gas to be measured according to the amplitude of the oscillation frequency.
  • Figure 1 is a schematic diagram of an application scenario of a gas concentration detection device in the present application
  • Fig. 2 is the first structural schematic diagram of the gas concentration detection equipment in the present application
  • Figure 3(a) is a schematic diagram of the pump light scanning the gas absorption line in the present application.
  • Figure 3(b) is a schematic diagram of the first harmonic generated by the pump light absorbed by the gas in the present application
  • Figure 3(c) is a schematic diagram of the second harmonic generated by the pump light absorbed by the gas in the present application.
  • Fig. 4 is the second structural schematic diagram of the gas concentration detection equipment in the present application.
  • FIG. 5 is a schematic structural view of the pump light source in the present application.
  • FIG. 6 is a schematic structural diagram of a coherent demodulation module in the present application.
  • FIG. 7 is a schematic diagram of the third structure of the gas concentration detection device in the present application.
  • FIG. 8 is a schematic diagram of the fourth structure of the gas concentration detection device in the present application.
  • FIG. 9 is a schematic diagram of the fifth structure of the gas concentration detection device in the present application.
  • Fig. 10 is a schematic diagram of an embodiment of the gas concentration detection method in the present application.
  • the present application provides a gas concentration detection device and a gas concentration detection method, which can extend the optical fiber and deploy it close to the area to be measured (such as an oil and gas pipeline).
  • a gas concentration detection device and a gas concentration detection method which can extend the optical fiber and deploy it close to the area to be measured (such as an oil and gas pipeline).
  • one or more air holes may be opened on the optical fiber to facilitate the free diffusion of gas into the optical fiber.
  • the position of each air hole on the optical fiber can be used as a gas sensor. All gas sensors share a set of signal transmitting device and signal processing device.
  • the system structure is simpler and it is convenient for multi-point deployment and monitoring.
  • FIG. 1 is a schematic diagram of an application scenario of a gas concentration detection device in this application.
  • the gas concentration detection equipment is applied to the scene of oil and gas pipeline monitoring.
  • the length of oil and gas pipelines is more than one kilometer, and multi-point monitoring along the pipeline is required.
  • the gas concentration detection equipment provided by this application only needs to extend one optical fiber, so that the optical fiber can be deployed close to the oil and gas pipeline to realize multi-point gas leakage monitoring at the pipeline, and can locate the leakage location and gas concentration of the oil and gas pipeline.
  • other components in the gas concentration detection equipment except the optical fiber can be placed in the remote computer room, away from the oil and gas pipeline, and the safety is better.
  • the gas concentration detection device provided by the present application will be introduced in detail below.
  • Fig. 2 is a schematic structural diagram of the first type of gas concentration detection device in the present application.
  • the gas concentration detection device includes a signal transmitting device 10 , a signal processor device 20 and an optical fiber sensing device 30 .
  • the optical fiber sensing device 30 includes an optical fiber 301 and at least one air hole 302 located on the optical fiber 301 .
  • the gas to be measured can enter the optical fiber 301 through the air hole 302 .
  • the signal transmitting device 10 is used for outputting detection signals to the optical fiber 301 . If the gas to be measured enters the optical fiber 301 , the detection signal will be reflected from the air hole 302 .
  • the signal processing device 20 is used for receiving the reflected echo signal, and determining the concentration of the gas to be measured and the position of the gas to be measured according to the echo signal. It should be understood that the present application does not limit the length of the optical fiber 301, for example, the length of the optical fiber 301 is greater than or equal to 2 km.
  • the air holes 302 can be drilled in the cladding of the hollow-core optical fiber by laser, mechanical or chemical corrosion. The distance between every two adjacent air holes 302 can be equal or unequal, for example, one air hole can be selected every 10m.
  • the detection signal output by the signal transmitting device 10 includes pump light.
  • the signal transmitting device 10 generates two paths of light, one path is pumping light, and the other path is pulsed detection light, and the pulsed detection light and pumping light will be coupled into the optical fiber 301 together.
  • the signal transmitting device 10 generates pump light, and generates pulsed detection light according to the pump light, and then the pulsed detection light is coupled into the optical fiber 301 . That is to say, no matter which implementation is adopted, the signal transmitting device 10 has a pumping light source.
  • the signal processing device 20 can determine the concentration of the gas to be measured according to the phase or intensity of the echo signal. These two implementations will be described in detail later.
  • the signal processing device 20 can use a commonly used laser ranging method to determine the position of the gas to be measured, for example, using a method similar to time of flight (Time of Flight, TOF) for ranging, which is not limited here.
  • the present application requires that the wavelength of the pump light be modulated, so that the wavelength of the pump light can be tuned periodically.
  • an oscillation frequency must be applied to the pump light to generate a specific frequency component, which is used to reduce low-frequency noise interference in the test environment, thereby improving the signal-to-noise ratio.
  • the wavelength of the pump light is tuned slowly, for example, the tuning frequency is 0.01 Hz-100 Hz.
  • the pump light has a fast oscillation frequency, for example, the oscillation frequency can be in the order of KHz-MHz.
  • Fig. 3(a) is a schematic diagram of pump light scanning gas absorption lines in this application.
  • the gas absorption line refers to the dark spectral line formed in the spectrum when light of a certain wavelength is absorbed by the gas. Since the pump light periodically tunes the wavelength, its wavelength can slowly scan the phase envelope generated by the absorption peak of the gas to be measured. It should be understood that it takes time for the thermal motion of gas absorbing light to reach a stable state. In the process of periodic tuning of the pump light wavelength, it is necessary to ensure that the refractive index of the gas in the optical fiber reaches a stable state before changing the pump light wavelength from the current wavelength value. to the next wavelength value.
  • Fig. 3(b) is a schematic diagram of the first harmonic generated by the pump light absorbed by the gas in this application.
  • Fig. 3(c) is a schematic diagram of the second harmonic generated by the pump light absorbed by the gas in this application.
  • the frequency of the first harmonic is equal to the oscillation frequency
  • the second harmonic is equal to twice the oscillation frequency, and so on.
  • the peak-to-peak values of the first harmonic and the second harmonic are proportional to the gas concentration, and both the peak-to-peak values of the first harmonic and the second harmonic can represent the amplitude of the oscillation frequency of the pump light. Therefore, the signal processing device 20 can determine the concentration of the gas to be measured by calculating the amplitude of the oscillation frequency.
  • the purpose of applying the oscillation frequency to the pump light is to generate the first harmonic and second harmonic related to the gas concentration, as shown in Figure 3(b) and Figure 3(c ) shown.
  • the purpose of periodically tuning the wavelength of the pump light as shown in Figure 3(a) is to generate the phase envelope of the first harmonic as shown in Figure 3(b) or the phase envelope of the second harmonic as shown in Figure 3(c) network. Therefore, the amplitude of the oscillation frequency of the pump light can be determined according to the peak-to-peak value of the first harmonic or the second harmonic, and then the amplitude of the oscillation frequency can determine the concentration of the gas to be measured.
  • Embodiment 1 The amplitude of the oscillation frequency is determined by demodulating the phase of the echo signal, and then the concentration of the gas to be measured is determined according to the amplitude of the oscillation frequency.
  • Fig. 4 is a second structural schematic diagram of the gas concentration detection device in the present application.
  • the signal transmitting device 10 includes: a pumping light source 101 , a laser 102 , a pulsed light generator 103 and a circulator 104 .
  • the signal transmitting device 10 may further include an optical amplifier 105 .
  • the signal processing device 20 includes: a coherent demodulation module 201 and a lock-in amplification module 202 .
  • the pump light source 101 is used to output pump light
  • the optical amplifier 105 is used to amplify the pump light and output the amplified pump light to the optical fiber 301 .
  • the laser 102 is used to output the first light beam to the pulsed light generator 103 and output the second light beam to the coherent demodulation module 201 .
  • the pulsed light generator 103 generates pulsed detection light according to the first light beam, and the pulsed detection light output by the pulsed light generator 103 is transmitted to the optical fiber 301 through the circulator 104 .
  • the detection signal output by the signal transmitting device 10 includes the pump light and the pulsed detection light coupled into the optical fiber 301 , and the echo signal includes the pulsed detection light reflected at the air hole 302 .
  • the echo signal is transmitted to the coherent demodulation module 201 after passing through the circulator 104 .
  • the coherent demodulation module 201 can coherently demodulate the echo signal according to the second light beam to obtain the phase of the echo signal.
  • the lock-in amplification module 202 demodulates the oscillation frequency of the pump light and the integer multiple of the oscillation frequency according to the phase of the echo signal, and determines the amplitude of the oscillation frequency. Since the amplitude of the oscillation frequency is directly proportional to the gas concentration, the lock-in amplifier module 202 can determine the concentration of the gas to be measured according to the amplitude of the oscillation frequency.
  • the above-mentioned circulator 104 is only an example, and other similar devices can also be used in practical applications. For example, a three-port device is used, wherein two ports are unidirectional optical ports, and two unidirectional ports transmit The direction of light is opposite. The other port is a bidirectional transmission multiplexed port, which supports optical bidirectional transmission.
  • phase of the echo signal ( ⁇ 1(t), ⁇ 2(t), ⁇ 3(t)7) includes the tuning frequency of the periodic tuning of the wavelength of the pump light, the oscillation frequency of the pump light, the oscillation frequency of the pump light 2 times that of the pump light, 3 times the oscillation frequency of the pump light... and phase changes caused by external disturbances.
  • the gas absorption phase ( ⁇ 12(t), ⁇ 23(t)7) is the phase change caused by the transmission of the light field in the gas due to the change of the refractive index of the gas due to the absorption of the pump light by the gas.
  • This phase change is related to the frequency of the pump light and thus varies periodically.
  • the lock-in amplification module 202 demodulates any one of the oscillation frequency of the pump light, twice the oscillation frequency of the pump light, three times the oscillation frequency of the pump light... That is, the oscillation frequency of the pump light or twice the oscillation frequency of the pump light is usually selected.
  • FIG. 5 is a schematic structural diagram of a pumping light source in the present application.
  • the pumping light source includes a signal generator 101a, a temperature current controller 101b and a DC laser 101c.
  • the sawtooth wave and the sine wave generated by the signal generator 101a jointly modulate the temperature current controller 101b.
  • the frequency of the sawtooth wave can be 0.01 Hz-100 Hz
  • the frequency of the sine wave can be in the order of KHz-MHz.
  • the temperature current controller 101b generates a corresponding frequency modulated current signal and sends it to the DC laser 101c.
  • the DC laser 101c then generates pump light with periodically tuned wavelength, and the pump light has an oscillation frequency.
  • the tuning frequency is in the range of 0.01 Hz-100 Hz
  • the oscillation frequency is in the order of KHz-MHz.
  • FIG. 6 is a schematic structural diagram of a coherent demodulation module in this application.
  • the coherent demodulation module 201 includes a polarization beam splitter 2011, a polarization beam splitter 2012, a 2 ⁇ 2 coupler 2013, a 2 ⁇ 2 coupler 2014, a balanced photodetector 2015, a balanced photodetector 2016, An analog-to-digital converter 2017 , an analog-to-digital converter 2018 and a data processing unit 2019 .
  • the polarization beam splitter 2011 is used to receive the second light beam from the laser 102 and divide the second light beam into x1 polarized light and y1 polarized light, and the x1 polarized light and y1 polarized light are orthogonal to each other.
  • the polarization beam splitter 2011 is used to receive the echo signal from the optical fiber sensing device 30 and divide the echo signal into x2 polarized light and y2 polarized light, and the x2 polarized light and y2 polarized light are orthogonal to each other.
  • the x1 polarized light and the x2 polarized light are coupled into the 2 ⁇ 2 coupler 2013 to generate interference optical signals and then coupled into the balanced photodetector 2015.
  • the balanced photodetector 2015 converts the optical signal into an electrical signal and outputs it to the analog-to-digital converter 2017.
  • the y1 polarized light and y2 polarized light are coupled into the 2 ⁇ 2 coupler 2014, and the interference optical signal is generated and then coupled into the balanced photodetector 2016.
  • the balanced photodetector 2016 converts the optical signal into an electrical signal and outputs it to the modulus Converter 2018.
  • the analog-to-digital converter 2017 and the analog-to-digital converter 2018 respectively convert input analog signals into digital signals, and respectively output the digital signals to the data processing unit 2019 .
  • the data processing unit 2019 demodulates the phase of the echo signal according to the input digital signal.
  • Embodiment 2 The amplitude of the oscillation frequency is determined by detecting the intensity of the echo signal, and then the concentration of the gas to be measured is determined according to the amplitude of the oscillation frequency.
  • Fig. 7 is a schematic diagram of the third structure of the gas concentration detection device in the present application.
  • the signal transmitting device 10 includes: a pump light source 101 , a pulse light generator 103 and a controller 106 .
  • the signal processing device 20 includes: a photodetector 203 and a lock-in amplifier module 202 .
  • the optical fiber sensing device 30 also includes a circulator 303 .
  • the pumping light source 101 outputs pumping light to the pulsed light generator 103 .
  • the pulsed light generator 103 generates pulsed probe light based on the input pump light.
  • the pulsed detection light output by the pulsed light generator 103 is output to the optical fiber 301 after passing through the circulator 303 .
  • the controller 106 is used to control the pulsed light generator 103 to be turned on or off. In the process of periodically tuning the pump light wavelength by the pump light source 101, whenever the pump light wavelength is fixed at a wavelength value, the controller 106 controls the pulse light generator 103 to turn on; otherwise, the controller 106 controls the pulse light generator 103 off.
  • the detection signal output by the signal transmitting device 10 is the pulsed detection light
  • the echo signal includes the pulsed detection light reflected at the air hole 302 .
  • the echo signal is transmitted to the photodetector 203 after passing through the circulator 303 .
  • the photodetector 203 is used to convert the input echo signal into an electrical signal, and detect the intensity of the electrical signal, and the intensity of the electrical signal can reflect the intensity of the echo signal.
  • the lock-in amplification module 202 demodulates the oscillation frequency of the pump light and the integer multiple of the oscillation frequency according to the intensity of the echo signal, and determines the amplitude of the oscillation frequency. Since the amplitude of the oscillation frequency is directly proportional to the gas concentration, the lock-in amplifier module 202 can determine the concentration of the gas to be measured according to the amplitude of the oscillation frequency.
  • the pump light source 101 in Embodiment 2 may use a pump light source similar to that in Embodiment 1 above.
  • the circulator 303 may be disposed in the signal transmitting device 10, which is not specifically limited here.
  • the controller 106 may be built into the signal transmitting device 10, or may be used as an independent module to control the pulsed light generator 103, which is not specifically limited here.
  • Embodiment 1 adopts the optical coherent demodulation method, which can more effectively amplify the gas absorption phase, so it can also be detected when the gas concentration value is very low, that is, the above-mentioned Embodiment 1 is compared with Embodiment 2
  • the concentration range of the detected gas is wider.
  • another advantage of Embodiment 1 over Embodiment 2 is that it has a higher tolerance for photodetectors.
  • the photothermal detection adopted in Embodiment 1 does not need to limit the working wavelength of the photodetector, while the intensity detection in Embodiment 2 requires light
  • the working wavelength of the detector is consistent with that of the pump laser.
  • the above-mentioned Embodiment 2 uses fewer components, the system is simpler, and the cost is lower.
  • optical fiber 301 used in the optical fiber sensing device 30 may be implemented in various manners, which will be introduced respectively below.
  • the entire section of the optical fiber 301 is a hollow-core optical fiber.
  • the characteristic of the hollow core fiber is that the center of the fiber is a hollow core structure, and the gas can be pressurized or freely diffused into the hollow core fiber.
  • the diameter of the hollow core fiber is about tens of ⁇ m, its special optical waveguide structure is limited in electromagnetic The light field diffuses radially, and the transmission of the light field in the hollow core enhances the interaction with the gas, so it can be applied to gas sensing and monitoring.
  • types of hollow-core fibers include, but are not limited to, anti-resonant hollow-core fibers, hollow-core photonic bandgap fibers, and hollow fibers.
  • the anti-resonant hollow core fiber includes a cladding and a plurality of micro-ring structures.
  • the cladding surrounds and forms an internal space, and multiple micro-ring structures are located in the internal space.
  • the area surrounded by multiple micro-ring structures is the core area, and the core area is The region where light waves travel.
  • the hollow-core photonic bandgap fiber includes a cladding and regularly arranged air holes.
  • the cladding surrounds and forms an inner space, and the regularly arranged air holes are located in the inner space.
  • the air holes surround and form a central hollow area, which is the area for light wave transmission.
  • the hollow optical fiber includes a cladding and a silver reflective film.
  • the cladding surrounds the inner space, and the silver film is plated on the inner surface of the cladding to form a hollow area. The total reflection of the light field at the silver film is limited to the hollow area.
  • FIG. 8 is a schematic diagram of a fourth structure of the gas concentration detection device in this application.
  • the optical fiber sensing device 30 further includes at least one coupler 304 .
  • the optical fiber 301 includes a trunk optical fiber 3011 and at least one branch optical fiber 3012 .
  • the backbone optical fiber 3011 is a solid core optical fiber.
  • the branch fiber 3012 can be divided into two sections, one section is a solid core fiber 3012a, and the other section is a hollow core fiber 3012b. The following uses one of the branch fibers as an example to introduce, and the connection methods of other branch fibers are similar.
  • the solid-core fiber 3012a on the branch fiber 3012 is connected in series with the hollow-core fiber 3012b, the air hole 302 is located on the hollow-core fiber 3012b, and the solid-core fiber 3012a is connected to the trunk fiber 3011 through a coupler 304 .
  • the coupler 304 is used for splitting the detection signal transmitted in the trunk optical fiber to obtain a first detection signal and a second detection signal.
  • the first detection signal is continuously transmitted along the trunk optical fiber 3011
  • the second detection signal is transmitted along the branch optical fiber 3012 .
  • the types of solid-core optical fibers in this embodiment include but not limited to multimode optical fibers, single-mode optical fibers and multi-core optical fibers.
  • Types of the hollow-core fiber in this embodiment include, but are not limited to, anti-resonant hollow-core fibers, hollow-core photonic bandgap fibers, and hollow fibers.
  • the above-mentioned segmented optical fiber may also use a hollow-core optical fiber in its entirety, and the hollow-core optical fiber may also be coated to increase reflection efficiency, which is not limited here.
  • the length of the solid-core optical fiber is usually in the range of 1 m-100 km, and the length of the hollow-core optical fiber is usually in the range of 1 cm-100 m.
  • the optical fiber provided by this embodiment can be applied to the scene where the area to be tested is long and the distribution of the area to be tested is scattered.
  • FIG. 9 is a schematic diagram of a fifth structure of the gas concentration detection device in this application.
  • the optical fiber 301 includes a solid-core optical fiber and a hollow-core optical fiber, wherein the solid-core optical fiber and the hollow-core optical fiber are connected in series, and the air hole is located on the hollow-core optical fiber.
  • the air hole may be located at the end face where the hollow-core fiber is connected to the solid-core fiber.
  • the detection signal is transmitted along the solid-core fiber 301a to the hollow-core fiber 301b, and an air hole 302a is provided at the end face of the hollow-core fiber 301b connected to the solid-core fiber 301c.
  • the detection signal passing through the air hole 302a will also be transmitted along the solid-core fiber 301c to the hollow-core fiber 301d, and the end face of the hollow-core fiber 301d connected to the solid-core fiber 301e is provided with an air hole 302b, and so on.
  • the types of solid-core optical fibers in this embodiment include but not limited to multimode optical fibers, single-mode optical fibers and multi-core optical fibers.
  • Types of the hollow-core fiber in this embodiment include, but are not limited to, anti-resonant hollow-core fibers, hollow-core photonic bandgap fibers, and hollow fibers.
  • this embodiment can only use hollow-core optical fiber in a section adjacent to the area to be tested, and use solid-core optical fiber in other areas, which can effectively save costs.
  • the present application provides a distributed gas concentration detection device based on optical fiber sensing, which can extend the optical fiber and deploy it close to the area to be measured (such as oil and gas pipelines).
  • one or more air holes may be opened on the optical fiber to facilitate the free diffusion of gas into the optical fiber.
  • the signal transmitting device in the gas concentration detection device is used to output a detection signal to the optical fiber, the detection signal includes pump light, and the pump light is absorbed by the gas to be measured to produce a change in refractive index, thereby causing a change in the intensity of the echo signal and phase changes.
  • the wavelength of the pump light is periodically tuned and the pump light has an oscillation frequency.
  • the signal processing device receives the echo signal reflected by the detection signal at the air hole, first determines the amplitude of the oscillation frequency according to the echo signal, and then determines the concentration of the gas to be measured according to the amplitude of the oscillation frequency.
  • the gas concentration detecting device provided in the present application is introduced above, and the gas concentration detecting method provided in the present application is introduced below.
  • Fig. 10 is a schematic diagram of an embodiment of the gas concentration detection method in the present application. It should be noted that the detection method of the gas concentration is realized based on the gas concentration detection equipment introduced in any of the implementations in FIG. 2 , FIG. 4 , FIG. 7 , FIG. 8 and FIG. 9 .
  • the gas concentration detection method includes the following steps.
  • the detection signal includes pump light.
  • the detection signal includes one path of pump light and one path of pulsed probe light coupled into the optical fiber.
  • the probe signal includes pulsed probe light generated from the pump light, the pulsed probe light coupled into the optical fiber. It should be noted that the wavelength of the pump light is periodically tuned, and the pump light has an oscillation frequency. For a detailed introduction of the detection signal and the pump light, reference may be made to the relevant descriptions of the embodiments of the above-mentioned gas concentration detection device, and details will not be repeated here.
  • the optical fiber is provided with at least one air hole. If the gas to be measured enters the optical fiber through the air hole, the detection signal will be reflected at the air hole, and the reflected signal can be called an echo signal.
  • the air holes can be drilled in the cladding of the hollow-core optical fiber by laser, mechanical or chemical corrosion. The distance between every two adjacent air holes can be equal or unequal.
  • the phase of the echo signal can be demodulated first, or the intensity of the echo signal can be detected. Furthermore, the oscillation frequency of the pump light is demodulated according to the phase of the echo signal or the intensity of the echo signal, and the amplitude of the oscillation frequency is determined. Since the amplitude of the oscillation frequency is directly proportional to the gas concentration, the concentration of the gas to be measured can be determined. It should be noted that, for a detailed introduction on determining the concentration of the gas to be measured according to the echo signal, reference may be made to the relevant descriptions of the embodiments of the above-mentioned gas concentration detection device, and details will not be repeated here.

Abstract

L'invention concerne un dispositif de mesure de concentration de gaz et un procédé de mesure de concentration de gaz, dans lesquels une structure de système est plus simple, et qui facilitent la mise en oeuvre d'un déploiement et d'une surveillance multipoint. Le dispositif de mesure de concentration de gaz comprend : un appareil de transmission de signal (10), un appareil de détection à fibre optique (30) et un appareil de traitement de signal (20) ; l'appareil de détection à fibre optique (30) comprend une fibre optique (301) et au moins un trou d'air (302) se situant sur la fibre optique (301), et un gaz à mesurer entre dans la fibre optique (301) au moyen d'un trou d'air (302) ; l'appareil de transmission de signal (10) est utilisé pour fournir en sortie un signal de détection à la fibre optique (301) ; le signal de détection comprend une lumière de pompage, dont la longueur d'onde est réglée périodiquement, la lumière de pompage comportant une fréquence d'oscillation ; l'appareil de traitement de signal (20) est utilisé pour recevoir un signal d'écho du signal de détection réfléchi dans le trou d'air (302), pour déterminer l'amplitude d'une fréquence d'oscillation selon le signal d'écho et pour déterminer la concentration d'un gaz à mesurer selon l'amplitude de la fréquence d'oscillation.
PCT/CN2022/135178 2022-02-22 2022-11-29 Dispositif de mesure de concentration de gaz et procédé de mesure de concentration de gaz WO2023160079A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN202210162901.5 2022-02-22
CN202210162901.5A CN116678851A (zh) 2022-02-22 2022-02-22 一种气体浓度检测设备和气体浓度的检测方法

Publications (1)

Publication Number Publication Date
WO2023160079A1 true WO2023160079A1 (fr) 2023-08-31

Family

ID=87764578

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2022/135178 WO2023160079A1 (fr) 2022-02-22 2022-11-29 Dispositif de mesure de concentration de gaz et procédé de mesure de concentration de gaz

Country Status (2)

Country Link
CN (1) CN116678851A (fr)
WO (1) WO2023160079A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117175045A (zh) * 2023-11-02 2023-12-05 安徽中科中涣智能装备股份有限公司 一种基于光谱的电池箱热失控探测装置

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101387608A (zh) * 2008-05-27 2009-03-18 重庆大学 超长珐-珀干涉式气体传感器及基于传感器的气体测试仪
KR20130019889A (ko) * 2011-08-18 2013-02-27 한국과학기술연구원 할로우 코어를 갖는 광섬유를 이용한 반사형 프로브 타입의 기체 검출 장치 및 기체 검출 방법
CN104359892A (zh) * 2014-11-20 2015-02-18 福建师范大学 一种不同模态分子振动光谱检测与成像装置及方法
CN104596996A (zh) * 2015-01-06 2015-05-06 香港理工大学深圳研究院 基于空芯光纤光热效应的气体检测方法和系统
CN110376160A (zh) * 2019-08-05 2019-10-25 江苏禾吉新材料科技有限公司 一种基于频分复用的分布式光纤气体检测装置及检测方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101387608A (zh) * 2008-05-27 2009-03-18 重庆大学 超长珐-珀干涉式气体传感器及基于传感器的气体测试仪
KR20130019889A (ko) * 2011-08-18 2013-02-27 한국과학기술연구원 할로우 코어를 갖는 광섬유를 이용한 반사형 프로브 타입의 기체 검출 장치 및 기체 검출 방법
CN104359892A (zh) * 2014-11-20 2015-02-18 福建师范大学 一种不同模态分子振动光谱检测与成像装置及方法
CN104596996A (zh) * 2015-01-06 2015-05-06 香港理工大学深圳研究院 基于空芯光纤光热效应的气体检测方法和系统
CN110376160A (zh) * 2019-08-05 2019-10-25 江苏禾吉新材料科技有限公司 一种基于频分复用的分布式光纤气体检测装置及检测方法

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117175045A (zh) * 2023-11-02 2023-12-05 安徽中科中涣智能装备股份有限公司 一种基于光谱的电池箱热失控探测装置
CN117175045B (zh) * 2023-11-02 2024-03-22 安徽中科中涣智能装备股份有限公司 一种基于光谱的电池箱热失控探测装置

Also Published As

Publication number Publication date
CN116678851A (zh) 2023-09-01

Similar Documents

Publication Publication Date Title
US11802789B2 (en) Method and apparatus for optical sensing
CN101242224B (zh) 一种光纤管线监控系统
Zornoza et al. Long-range hybrid network with point and distributed Brillouin sensors using Raman amplification
CN105674905B (zh) 脉冲预泵浦单端矢量botda动态应变测量方法及装置
Muanenda et al. Hybrid distributed acoustic and temperature sensor using a commercial off-the-shelf DFB laser and direct detection
CN101634571A (zh) 光纤脉栅分布传感装置
AU2022203823B2 (en) Method and apparatus for optical sensing
WO2023160079A1 (fr) Dispositif de mesure de concentration de gaz et procédé de mesure de concentration de gaz
CN115200691A (zh) 一种少模光纤分布式声传感系统及其信号处理方法
Jiang et al. Channel-multiplexing for quasi-distributed acoustic sensing with orthogonal codes
Ma et al. Fiber-optic distributed acoustic sensor utilizing LiNbO 3 straight through waveguide phase modulator
CN115452020A (zh) 实现振动和温度同时测量的分布式光纤传感系统及方法
US20240012760A1 (en) Method and Apparatus for Optical Sensing
Farhadiroushan et al. Polarimetric coherence multiplexing using high-birefringence optical-fiber sensors and short coherence sources
Lee et al. Proof of concept for brillouin optical correlation-domain reflectometry assisted by spectral slope

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22928339

Country of ref document: EP

Kind code of ref document: A1