An open-core anti-resonant hollow fiber based quasi-distributed gas monitoring apparatus and method

Abstract

The application discloses a kind of quasi-distributed gas monitoring device and method based on hollow anti-resonance optical fiber, the device includes the first laser and hollow anti-resonance optical fiber connected in turn, N micro-holes are provided on the hollow anti-resonance optical fiber;The micro-hole is set in the position to be monitored, and each micro-hole is close to the setting of N acoustic sensors with preset distance;The acoustic sensor is optical fiber film microcavity pressure sensor, adopts end face elastic diaphragm structure;The application utilizes acoustic sensor to detect the sound wave signal excited by the thermal effect of the gas molecules to be measured into the hollow core part of hollow anti-resonance optical fiber through micro-hole and absorb excitation light energy, solve the problem that the existing gas detection technology based on photoacoustic spectroscopy involves more complex acoustic sensing unit and higher manufacturing cost, signal transmission is susceptible to electromagnetic interference, it is difficult to realize the miniaturization, high sensitivity, long distance quasi-distributed gas detection.

Description

Technical Field

[0001] This invention belongs to the technical field of optical gas detection, specifically relating to a quasi-distributed gas monitoring device and method based on hollow anti-resonant optical fiber. Background Technology

[0002] Optical gas detection technology is a class of gas detection methods based on optical principles. It utilizes the interaction between light and gas molecules to achieve real-time monitoring of gas concentration or composition. Optical gas detection technologies include absorption spectroscopy, fluorescence spectroscopy, and photoacoustic spectroscopy.

[0003] Photoacoustic spectroscopy-based gas detection technology is a highly sensitive method for gas detection. It utilizes the thermal effect generated when gas molecules absorb light energy of a specific wavelength, which in turn excites an acoustic signal. The gas concentration is then determined by detecting this acoustic signal. Photoacoustic spectroscopy-based gas detection technologies include cantilever-enhanced and quartz-enhanced types. The cantilever-enhanced type utilizes the principle that the acoustic signal causes a slight deformation in a micro-cantilever beam, using the micro-cantilever beam as an acoustic sensor to determine the gas concentration by detecting its deformation. However, due to the complexity of its acoustic sensing unit, large-scale deployment of multiple sensing points increases the size and cost of the sensing system, making it difficult to achieve miniaturized, highly sensitive quasi-distributed gas detection.

[0004] Currently, most gas detection technologies based on photoacoustic spectroscopy utilize the piezoelectric effect of acoustic sensors to convert acoustic signals into electrical signals and use cables for signal transmission. This makes the signal transmission susceptible to electromagnetic interference and difficult to achieve long-distance detection. Summary of the Invention

[0005] The purpose of this invention is to address the problems in existing photoacoustic spectroscopy-based gas detection technologies, such as the complexity and high manufacturing cost of acoustic sensing units, susceptibility to electromagnetic interference in signal transmission, and difficulty in achieving miniaturized, highly sensitive, and long-distance quasi-distributed gas detection. This invention provides a quasi-distributed gas monitoring device and method based on hollow-core anti-resonant optical fiber.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In one aspect, the present invention provides a quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber, comprising a first laser and a hollow anti-resonant optical fiber connected in sequence, wherein the hollow anti-resonant optical fiber is provided with N micro-holes; the micro-holes are disposed at the monitoring position, and each micro-hole is provided with N acoustic sensors close to it at a preset distance;

[0008] The acoustic sensor is an optical fiber thin-film microcavity pressure sensor with an end-face diaphragm structure.

[0009] As a preferred technical solution, the hollow core portion of the hollow anti-resonant optical fiber is provided with several capillaries close to the inner wall.

[0010] As a preferred technical solution, the spacing L between two adjacent micropores is set according to the acoustic wave velocity v and the excitation light modulation frequency f, specifically as follows: m is a positive integer.

[0011] As a preferred technical solution, the acoustic sensor includes a second laser and a single-mode optical fiber connected in sequence; a hollow cylindrical structure is provided at the laser outlet of the single-mode optical fiber, and an elastic diaphragm is attached to the end of the hollow cylindrical structure away from the single-mode optical fiber, so that a microcavity is formed inside the hollow cylindrical structure.

[0012] As a preferred technical solution, the elastic diaphragm is made of polymer, quartz, silicon or metal, with a thickness of 0.1-10µm and several through holes symmetrically arranged on the edge.

[0013] As a preferred technical solution, the micropores are obtained through the following steps:

[0014] A rectangular groove with a length of 10-200 μm, a width of 10-200 μm, and a depth of 10-60 μm was fabricated on a hollow antiresonant fiber using a femtosecond laser.

[0015] The hollow anti-resonant optical fiber after one processing is immersed in anhydrous ethanol, ultrasonically cleaned at room temperature, and then air-dried naturally.

[0016] A femtosecond laser was used to process a groove with a length of a-5μm, a width of b-5μm, and a depth reaching the hollow part of the hollow anti-resonant fiber at the center of a rectangular groove.

[0017] Another aspect of the present invention provides a quasi-distributed gas monitoring method based on hollow-core anti-resonant optical fiber, characterized by comprising the following steps;

[0018] A quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber, as described above, is deployed to the location to be monitored.

[0019] The first laser emits excitation light, which is transmitted through a hollow anti-resonant optical fiber.

[0020] The second laser emits detection light, which is transmitted through an acoustic sensor and forms an interference spectrum at the end microcavity.

[0021] The gas molecules to be tested enter the hollow core of the hollow anti-resonant optical fiber through the micropores and absorb the excitation light energy, generating a thermal effect to excite the acoustic signal.

[0022] The acoustic sensor receives the sound wave signal excited by the gas molecules to be measured, which in turn causes the interference spectrum of the acoustic sensor to change.

[0023] The changing interference spectrum signal is demodulated using a demodulation system to obtain real-time concentration information of the gas molecules to be measured.

[0024] As a preferred technical solution, the acoustic sensor end microcavity is obtained by sequentially setting up: single-mode optical fiber - hollow cylindrical structure - elastic diaphragm. The reflected light of the detection light on the two end faces of the microcavity interferes to form an interference spectrum; the acoustic wave signal excited by the gas molecules to be measured causes the elastic diaphragm to deform, thereby changing the interference spectrum.

[0025] As a preferred technical solution, the excitation wavelength is consistent with the absorption peak wavelength of the gas molecules to be measured.

[0026] As a preferred technical solution, the detection light wavelength range is 1500-1650nm.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] (1) The quasi-distributed gas monitoring method based on hollow-core anti-resonant optical fiber of the present invention is low in cost, small in size, and light in weight, and can meet the real-time monitoring of gas concentration in different application scenarios. It reduces optical loss by utilizing the anti-resonance mechanism of hollow-core anti-resonant optical fiber, supports long-distance multi-point gas measurement, and enhances the acoustic signal generated by the gas by utilizing the longitudinal acoustic resonance mode inside the optical fiber, thereby improving the sensitivity of distributed gas detection. The gas pump light and the probe light are transmitted through all-fiber optics, which has strong anti-electromagnetic interference capability. Combined with optical fiber multiplexing technology, long-distance and large-scale networking can be realized to achieve high-performance distributed gas monitoring. Attached Figure Description

[0029] Figure 1 This is a device diagram of the quasi-distributed gas monitoring device and method based on hollow anti-resonant optical fiber disclosed in the embodiments of the present invention.

[0030] Figure 2 This is a schematic diagram of an acoustic sensor structure disclosed in an embodiment of the present invention;

[0031] Figure 3 This is a flowchart of a quasi-distributed gas monitoring method based on hollow anti-resonant optical fiber disclosed in an embodiment of the present invention.

[0032] The following are the symbols and their meanings: 1. Hollow-core anti-resonant optical fiber; 2. Acoustic sensor; 3. Hollow core section; 4. Micropore; 21. Single-mode optical fiber; 22. Microcavity; 23. Hollow cylindrical structure; 24. Elastic diaphragm; 25. Through hole. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0034] Example 1:

[0035] like Figure 1 As shown, this embodiment provides a quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber, including a first laser and a hollow anti-resonant optical fiber 1 connected in sequence, and also includes an acoustic sensor 2.

[0036] N micro-holes 4 are provided at different positions on the hollow anti-resonant optical fiber 1; the micro-holes 4 are set at the positions to be monitored, and each micro-hole 4 is closely attached to an acoustic sensor 2 at a preset distance;

[0037] The acoustic sensor 2 is an optical fiber thin-film microcavity pressure sensor with an end-face diaphragm structure.

[0038] In one or more preferred embodiments, such as Figure 1 As shown, the hollow core portion 3 of the hollow anti-resonant optical fiber 1 is an approximately cylindrical hollow structure with several capillaries (more preferably, 7 capillaries) arranged close to the inner wall. The excitation light mainly propagates in the hollow core portion 3, and the gas molecules to be measured absorb the excitation light energy in the hollow core portion 3, generating a thermal effect to excite the acoustic signal.

[0039] In one or more preferred embodiments, the spacing L between two adjacent micropores 4 is set according to the acoustic wave velocity v and the excitation light modulation frequency f, specifically as follows: m is a positive integer.

[0040] In one or more preferred embodiments, such as Figure 2 As shown, the acoustic sensor 2 includes a second laser, a single-mode fiber 21, a hollow cylindrical structure 23, and an elastic diaphragm 24. The second laser is connected to the single-mode fiber 21. One end of the hollow cylindrical structure 23 is connected to the laser exit of the single-mode fiber 21, and the other end of the hollow cylindrical structure 23 away from the single-mode fiber is attached to the elastic diaphragm 24, forming a microcavity 22 inside the hollow cylindrical structure 23. Further, the elastic diaphragm 24 is processed with a number of symmetrical through holes 25 (more preferably, four arc-shaped through holes spaced 90° apart) at its edges using a femtosecond laser to enhance airflow inside and outside the microcavity, thereby enhancing the stability of the elastic diaphragm 24.

[0041] In one or more preferred embodiments, the elastic diaphragm 24 is made of a polymer, quartz, silicon or metal, and has a thickness of 0.1-10µm.

[0042] In one or more preferred embodiments, the micropores 4 are obtained by the following steps:

[0043] A rectangular groove with a length a = 10-200 μm, a width b = 10-200 μm, and a depth of 10-60 μm was fabricated on a hollow anti-resonant fiber 1 using a femtosecond laser.

[0044] The hollow anti-resonant fiber 1 after one processing was immersed in anhydrous ethanol, ultrasonically cleaned at room temperature, and then naturally air-dried.

[0045] A femtosecond laser was used to process a groove with a length of a-5μm, a width of b-5μm, and a depth reaching the hollow core portion 3 of the hollow anti-resonant fiber 1 at the center of the rectangular groove.

[0046] As a more preferred technical solution, in the processing steps of micropore 4, the power of the femtosecond laser is set to 60mW, the length of the first processing is a=100μm, the width is b=200μm, the depth is 50μm, and the ultrasonic cleaning time is 1 minute.

[0047] It should be noted that the device provided in the above embodiments is only an example of the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure can be divided into different functional modules to complete all or part of the functions described above. The device can be applied to a quasi-distributed gas monitoring method based on hollow anti-resonant optical fiber in the following embodiments.

[0048] Example 2:

[0049] like Figure 3 As shown, this embodiment provides a quasi-distributed gas monitoring method based on hollow-core anti-resonant optical fiber, which can be applied to the quasi-distributed gas monitoring device based on hollow-core anti-resonant optical fiber described in the above embodiment, and includes the following steps:

[0050] S1. Arrange a quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber as described in Example 1 at the location to be monitored;

[0051] S2. Start the first laser to emit excitation light, which is transmitted through the hollow anti-resonant fiber 1.

[0052] S3. Start the second laser, emit detection light and transmit it through the acoustic sensor 2, and form an interference spectrum at the microcavity 22 at the end;

[0053] S4. The gas molecules to be tested enter the hollow core part 3 of the hollow anti-resonant optical fiber 1 through the micropore 4 and absorb the excitation light energy, generating a thermal effect to excite the sound wave signal.

[0054] S5. Acoustic sensor 2 receives the acoustic wave signal excited by the gas molecules to be measured, causing the interference spectrum of acoustic sensor 2 to change.

[0055] S6. The changing interference spectrum signal is demodulated using a demodulation system to obtain the real-time concentration information of the gas molecules to be measured.

[0056] In one or more preferred embodiments, the microcavity 22 at the end of the acoustic sensor 2 is obtained by sequentially arranging: single-mode optical fiber 21 - hollow cylindrical structure 23 - elastic diaphragm 24. The reflected light of the detection light on the two end faces of the microcavity 22 interferes to form an interference spectrum; the acoustic wave signal excited by the gas molecules to be measured causes the elastic diaphragm 24 to deform, thereby changing the interference spectrum.

[0057] In one or more preferred embodiments, the excitation wavelength is consistent with the absorption peak wavelength of the gas molecules to be measured.

[0058] In one or more preferred embodiments, the detection light wavelength range is 1500-1650 nm.

[0059] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0060] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A quasi-distributed gas monitoring device based on hollow-core anti-resonant optical fiber, characterized in that, It includes a first laser and a hollow anti-resonant optical fiber connected in sequence. The hollow anti-resonant optical fiber is provided with N micro-holes. The micro-holes are set at the position to be monitored, and each micro-hole is closely arranged with N acoustic sensors at a preset distance. The acoustic sensor is an optical fiber thin-film microcavity pressure sensor, which adopts an end-face elastic diaphragm structure.

2. The quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber according to claim 1, characterized in that, The hollow core portion of the hollow anti-resonant optical fiber has several capillaries attached to its inner wall.

3. The quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber according to claim 1, characterized in that, The spacing L between two adjacent micropores is set according to the acoustic wave velocity v and the excitation light modulation frequency f, specifically as follows: m is a positive integer.

4. The quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber according to claim 1, characterized in that, The acoustic sensor includes a second laser and a single-mode optical fiber connected in sequence; a hollow cylindrical structure is provided at the laser exit of the single-mode optical fiber, and an elastic diaphragm is attached to the end of the hollow cylindrical structure away from the single-mode optical fiber, so that a microcavity is formed inside the hollow cylindrical structure.

5. A quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber according to claim 4, characterized in that, The elastic diaphragm is made of polymer, quartz, silicon or metal, with a thickness of 0.1-10µm and several through holes symmetrically arranged on its edge.

6. A quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber according to claim 1, characterized in that, The micropores are obtained through the following steps: A rectangular groove with a length of 10-200 μm, a width of 10-200 μm, and a depth of 10-60 μm was fabricated on a hollow antiresonant fiber using a femtosecond laser. The hollow anti-resonant optical fiber after one processing is immersed in anhydrous ethanol, ultrasonically cleaned at room temperature, and then air-dried naturally. A femtosecond laser was used to process a groove with a length of a-5μm, a width of b-5μm, and a depth reaching the hollow part of the hollow anti-resonant fiber at the center of a rectangular groove.

7. A quasi-distributed gas monitoring method based on hollow-core anti-resonant optical fiber, characterized in that, Includes the following steps; A quasi-distributed gas monitoring device based on hollow anti-resonant optical fiber, as described in any one of claims 1-6, is deployed to the location to be monitored; The first laser emits excitation light, which is transmitted through a hollow anti-resonant optical fiber. The second laser emits detection light, which is transmitted through an acoustic sensor and forms an interference spectrum at the end microcavity. The gas molecules to be tested enter the hollow core of the hollow anti-resonant optical fiber through the micropores and absorb the excitation light energy, generating a thermal effect to excite the acoustic signal. The acoustic sensor receives the sound wave signal excited by the gas molecules to be measured, which in turn causes the interference spectrum of the acoustic sensor to change. The changing interference spectrum signal is demodulated using a demodulation system to obtain real-time concentration information of the gas molecules to be measured.

8. The quasi-distributed gas monitoring method based on hollow-core anti-resonant optical fiber according to claim 7, characterized in that, The acoustic sensor's end microcavity is formed by sequentially arranging a single-mode optical fiber, a hollow cylindrical structure, and an elastic diaphragm. The reflected light from the detection light on the two end faces of the microcavity interferes to form an interference spectrum. The acoustic wave signal excited by the gas molecules to be measured causes the elastic diaphragm to deform, thereby changing the interference spectrum.

9. A quasi-distributed gas monitoring method based on hollow-core anti-resonant optical fiber according to claim 7, characterized in that, The excitation wavelength is consistent with the absorption peak wavelength of the gas molecules to be measured.

10. A quasi-distributed gas monitoring method based on hollow-core anti-resonant optical fiber according to claim 7, characterized in that, The detection light wavelength range is 1500-1650nm.

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