Gas detection device and method based on hollow-core optical fiber

Abstract

The invention discloses a gas detection device and method based on a hollow-core optical fiber, and relates to the technical field of gas detection.The device comprises a laser used for emitting a laser beam with the wavelength corresponding to the absorption spectrum characteristic wavelength of gas to be detected; the beam splitter is connected with the laser and is used for splitting the laser beam into a first laser beam and a second laser beam; the hollow-core optical fiber is arranged on one side of the beam splitter and is used for bearing the gas to be detected and allowing the first laser beam to pass through; the reference gas chamber is arranged on one side of the beam splitter and used for allowing the second laser beam to pass through. The hollow-core optical fiber is used for replacing a traditional gas chamber, and the problems that the gas chamber is large in size, low in gas replacement efficiency and the like are solved. And the reference gas chamber is added, and the wavelength of the laser may drift due to factors such as driving current and environment temperature, so that the reference gas chamber can help to monitor and calibrate the wavelength of the laser in real time, and high measurement precision is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection, and in particular to a gas detection device and method based on hollow-core optical fiber. Background Art

[0002] Sulfur hexafluoride (SF6) is widely used in gas-insulated equipment (GIE) due to its excellent insulating properties. However, defects such as metal particles, surface burrs, and tiny air gaps can alter the internal electric field distribution, potentially leading to partial discharge (PD) and local overheating, and in severe cases, sparks or arcs. Furthermore, GIE can also experience local overheating due to factors such as uneven silver plating on contact surfaces, poor contact, high temperatures at the arc center when switching high currents, and magnetic short circuits caused by insulation damage in the core silicon steel sheets. If these defects are not detected promptly, they can lead to insulation failures during operation, posing a threat to the safe and reliable operation of the GIE and the entire power system. Insulation failures caused by these potential defects typically begin as low-energy failures, during which SF6 decomposes to form a series of unstable low-fluorine sulfides, including but not limited to SO2F2, SOF2, and SO2. These react with impurities in the equipment, including but not limited to H2O, O2, and organic matter, degrading the SF6's insulating properties, further exacerbating PD and local overheating, creating a vicious cycle. Ultimately, this phenomenon can lead to insulation breakdown or high-temperature ablation, potentially endangering the safe operation of gas-insulated equipment. Therefore, detecting defects in gas-insulated equipment is an important part of electrical equipment maintenance.

[0003] Conventional tunable diode laser absorption spectroscopy uses a conventional gas chamber as the space for the laser and gas reaction. However, these chambers are bulky, have low gas exchange efficiency, and are susceptible to environmental fluctuations, including but not limited to temperature and pressure changes, which can affect measurement results. Therefore, a gas detection device and method with a compact size and high gas exchange efficiency is needed, which can eliminate the impact of environmental fluctuations on measurement results. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that the traditional gas chamber has a large volume, low gas replacement efficiency, and is easily affected by environmental fluctuations.

[0005] The above technical problems are solved by the following technical solutions:

[0006] The present invention provides a gas detection device based on hollow-core optical fiber, which comprises a laser, a beam splitter, a hollow-core optical fiber and a reference gas chamber.

[0007] In a preferred embodiment of the hollow-core optical fiber-based gas detection device of the present invention: a laser is configured to emit a laser beam having a wavelength corresponding to a characteristic wavelength of the absorption spectrum of the gas to be detected;

[0008] a beam splitter connected to the laser and configured to split the laser beam into a first laser beam and a second laser beam;

[0009] A hollow-core optical fiber, disposed on one side of the beam splitter, for carrying the gas to be measured and passing the first laser beam;

[0010] A reference gas chamber is provided on one side of the beam splitter and is used for passing the second laser beam.

[0011] In a preferred embodiment of the hollow-core optical fiber-based gas detection device of the present invention, a gas pool is provided between the hollow-core optical fiber and the beam splitter, and one end of the hollow-core optical fiber is sealed in the gas pool.

[0012] In a preferred embodiment of the hollow-core optical fiber-based gas detection device of the present invention: a first optical calibration component is disposed between the beam splitter and the gas pool, and the first optical calibration component focuses the first laser beam into the core of the hollow-core optical fiber.

[0013] In a preferred embodiment of the hollow-core optical fiber-based gas detection device of the present invention: a second optical calibration component is provided on a side of the hollow-core optical fiber away from the gas pool, and is used to focus the first laser beam passing through the hollow-core optical fiber;

[0014] A first photodetector faces the second optical calibration component, and the photodetector receives the first laser beam and generates first data.

[0015] In a preferred embodiment of the hollow-core optical fiber-based gas detection device of the present invention: a third optical calibration component is disposed between the beam splitter and the reference gas chamber, and the third optical calibration component focuses the second laser beam into the reference gas chamber;

[0016] The second photodetector is disposed on a side of the reference gas cell away from the third optical calibration component, and receives the second laser beam passing through the reference gas cell and generates second data.

[0017] In a preferred embodiment of the hollow-core optical fiber-based gas detection device of the present invention: a phase-locked amplifier is connected to the first photodetector and the second photodetector, amplifies the signal in the first data having the same frequency and phase as the second data, and generates third data.

[0018] In a preferred embodiment of the hollow-core optical fiber-based gas detection device of the present invention: a data acquisition component is connected to the lock-in amplifier and the data processing component, and samples third data;

[0019] The data processing component receives the third data and obtains a second harmonic signal according to the Lambert-Beer law.

[0020] In a preferred embodiment of the hollow-core optical fiber-based gas detection device of the present invention, the laser is a quantum cascade laser, and the central wavelength of the laser beam is 1504 cm -1 , the gas to be measured is SO2F2.

[0021] The present invention also proposes a gas detection method based on hollow-core optical fiber, which includes emitting and splitting a laser beam, generating first data and second data, processing the first data and the second data, and calculating the concentration of the gas to be measured.

[0022] In a preferred embodiment of the hollow-core optical fiber-based gas detection method of the present invention, a laser beam is emitted and split, wherein the emitted laser beam has a wavelength corresponding to a characteristic wavelength of the absorption spectrum of the gas to be measured, and a beam splitter is used to split the laser beam into at least two beams, one of which is used as a measurement beam and passes through the hollow-core optical fiber, and the other is used as a reference beam and passes through a reference gas chamber;

[0023] generating first data and second data, using a photodetector to detect the light intensities of the measuring beam and the reference beam respectively, and generating the first data and the second data;

[0024] Processing first data and second data, processing the first data and the second data using a lock-in amplifier, amplifying a signal in the first data having the same frequency and phase as the second data, to generate third data;

[0025] The concentration of the gas to be measured is calculated using a data processing component based on the third data and in combination with the Lambert-Beer law to obtain the concentration of the gas to be measured.

[0026] In a preferred embodiment of the hollow-core optical fiber-based gas detection method of the present invention: the generation of the first data and the second data includes using a photodetector to respectively detect the light intensities of the measuring light beam passing through the hollow-core optical fiber and the reference light beam passing through the reference gas chamber, and converting the optical signal into an electrical signal, thereby generating first data representing the measuring light intensity and second data representing the reference light intensity.

[0027] The beneficial effects of the present invention are as follows: the present invention utilizes hollow-core optical fiber to replace the traditional air chamber, effectively solving the problems of large air chamber volume and low gas replacement efficiency. Compared with the traditional air chamber, the hollow-core optical fiber air chamber eliminates optical devices such as optical collimators or high-reflection mirrors in the traditional air chamber, which not only helps to reduce light path noise, but also has significant advantages such as small size, light weight, easy winding and easy extension of the effective absorption path of the gas. In addition, the present invention adds a reference air chamber. Since the wavelength of the laser may drift due to factors such as the driving current and ambient temperature, the reference air chamber can help monitor and calibrate the wavelength of the laser in real time to ensure high-precision measurements. In addition, the reference air chamber can also eliminate the impact of environmental fluctuations, including but not limited to temperature and pressure changes, on the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention. Obviously, the drawings described below only relate to some embodiments of the present invention, and are not intended to limit the present invention.

[0029] Figure 1 A schematic diagram of a gas detection device based on a hollow-core optical fiber is shown;

[0030] Figure 2 shows a structural diagram of a hollow core optical fiber;

[0031] Figure 3 A flow chart of a gas detection method based on hollow-core optical fiber is shown. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to specific embodiments and the accompanying drawings.

[0033] The terms used in the present invention are those commonly used in the art in view of the functions of the present invention, but these terms may vary according to the intentions of those skilled in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the present invention. Therefore, the terms used in the specification should not be understood as simple names, but rather as the meanings of the terms and the overall description of the present invention.

[0034] Example 1, reference Figure 1 , provides a gas detection device based on hollow-core optical fiber, including a laser 2, a beam splitter 3, a hollow-core optical fiber 7 and a reference gas chamber 6.

[0035] Specifically, Laser 2 is used to emit a laser beam with a wavelength corresponding to the characteristic wavelength of the absorption spectrum of the gas to be measured; Laser 2 uses a new type of quantum cascade laser. Compared with distributed feedback lasers, quantum cascade lasers have higher output power and better temperature stability, and can achieve stable operation at room temperature without complex temperature control. The spectral linewidth of the continuous wave quantum cascade laser can be compressed to the kilohertz level, which significantly improves the spectral resolution compared to traditional megahertz-level lasers. This enables the laser to accurately distinguish the absorption peaks of SF6 decomposition products and other interfering gases, reducing cross-interference and making it more advantageous in the detection of trace gases in gas-insulated equipment.

[0036] The beam splitter 3 is connected to the laser 2 and is used to split the laser beam into a first laser beam and a second laser beam; the first laser beam is a measuring beam, which is used to interact with the gas to be measured and obtain gas absorption information by measuring its light intensity change; the second laser beam is a reference beam, which is used to provide a reference signal to eliminate the influence of the laser's own fluctuations and changes in environmental factors on the measurement results, thereby improving the accuracy and stability of the measurement.

[0037] Hollow-core fiber 7, positioned on one side of beam splitter 3, carries the gas to be measured and passes the first laser beam. The first laser beam, serving as the measurement beam, is focused into the core of hollow-core fiber 7. Both the first laser beam and the gas to be measured pass through the core. The light field intensity of hollow-core fiber 7 then exhibits a ring-shaped distribution, with the light intensity primarily concentrated in the core layer and weaker in the hollow core region and cladding. A 2 kPa pressure differential is established across hollow-core fiber 7, enabling rapid filling and replacement of the gas to be measured.

[0038] The reference gas chamber 6 is provided on one side of the beam splitter 3 and is used to pass the second laser beam. The second laser beam is used as a reference beam and is absorbed by the photodetector after passing through the reference gas chamber 6.

[0039] Example 2, reference Figure 1 and Figure 2 This embodiment is based on the first embodiment. This embodiment provides a gas detection device based on hollow-core optical fiber, including a laser 2, a beam splitter 3, a hollow-core optical fiber 7 and a reference gas chamber 6.

[0040] Specifically, Laser 2 is used to emit a laser beam with a wavelength corresponding to the characteristic wavelength of the absorption spectrum of the gas to be measured; Laser 2 uses a new type of quantum cascade laser. Compared with distributed feedback lasers, quantum cascade lasers have higher output power and better temperature stability, and can achieve stable operation at room temperature without complex temperature control. The spectral linewidth of the continuous wave quantum cascade laser can be compressed to the kilohertz level, which significantly improves the spectral resolution compared to traditional megahertz-level lasers. This enables the laser to accurately distinguish the absorption peaks of SF6 decomposition products and other interfering gases, reducing cross-interference and making it more advantageous in the detection of trace gases in gas-insulated equipment.

[0041] The beam splitter 3 is connected to the laser 2 and is used to split the laser beam into a first laser beam and a second laser beam; the first laser beam is a measuring beam, which is used to interact with the gas to be measured and obtain gas absorption information by measuring its light intensity change; the second laser beam is a reference beam, which is used to provide a reference signal to eliminate the influence of the laser's own fluctuations and changes in environmental factors on the measurement results, thereby improving the accuracy and stability of the measurement.

[0042] Hollow-core fiber 7, positioned on one side of beam splitter 3, carries the gas to be measured and passes the first laser beam. This first laser beam, acting as the measurement beam, is focused into the core of hollow-core fiber 7. The light field intensity of hollow-core fiber 7 then exhibits a ring-shaped distribution, with the light intensity primarily concentrated in the core layer and weaker in the hollow core region and cladding. The hollow core region confines light to the low-refractive-index core region while also enhancing structural stability. A 2 kPa pressure differential is established between the two ends of hollow-core fiber 7, enabling rapid filling and replacement of the gas to be measured.

[0043] The gas pool 5 is arranged between the hollow-core optical fiber 7 and the beam splitter 3 . One end of the hollow-core optical fiber 7 is sealed in the gas pool 5 , which facilitates the flow of the gas to be measured in the gas pool 5 into the hollow-core optical fiber 7 .

[0044] A first optical calibration component 4 is provided between the beam splitter 3 and the gas pool 5 . The first optical calibration component 4 focuses the first laser beam into the core of the hollow-core optical fiber 7 . The first optical calibration component 4 may be a plano-convex lens with a focal length of 40 mm.

[0045] The reference gas cell 6 is provided on one side of the beam splitter 3 and is used to pass the second laser beam. The second laser beam, serving as a reference beam, is absorbed by the photodetector after passing through the reference gas cell 6.

[0046] Second optical calibration component 12, located on the side of hollow-core fiber 7 away from gas pool 5, is used to focus the first laser beam passing through hollow-core fiber 7. Second optical calibration component 12, which can be a lens with a focal length of 20 mm, is used to fine-tune the propagation direction of the first laser beam, ensuring that the laser beam accurately strikes the effective photosensitive surface of the photodetector. First photodetector 8, facing second optical calibration component 12, receives the first laser beam and generates first data.

[0047] The third optical calibration component 13 is arranged between the beam splitter 3 and the reference gas chamber 6. The third optical calibration component 13 focuses the second laser beam into the reference gas chamber 6. The third optical calibration component 13 can also be a lens to improve the efficiency of the second laser beam, i.e., the reference beam, entering the reference gas chamber and reduce the spot size, thereby improving the efficiency and accuracy of the subsequent photodetector receiving the reference beam.

[0048] The second photodetector 14 is disposed on a side of the reference gas cell 6 away from the third optical calibration component 13 , and receives the second laser beam passing through the reference gas cell 6 and generates second data.

[0049] Two photodetectors convert the laser beam's optical signal into an electrical signal, which is then transmitted to a lock-in amplifier 9. Connected to the first photodetector 8 and the second photodetector 14, the lock-in amplifier 9 amplifies signals within the first data that share the same frequency and phase as the second data, generating third data. The lock-in amplifier 9 is capable of extracting very weak signals in a noisy environment, effectively suppressing noise and improving signal quality. By comparing the phases of the first and second data, and utilizing phase-sensitive detection technology, it amplifies only those signals within the first data that share the same frequency and phase as the second data, generating third data. This data is then transmitted to a data acquisition unit 10, which can be a 485 transmission line. The data acquisition unit 10 samples the third data at a set sampling rate and transmits it to a data processing unit 11, which can be a computer. According to the Lambert-Beer law, the degree of light intensity reduction is proportional to the gas concentration. Analysis of the third data by the data processing unit 11 generates a concentration-dependent second harmonic signal, enabling more accurate and sensitive gas concentration detection.

[0050] Example 3, reference Figure 3 This embodiment provides a gas detection method based on hollow-core optical fiber, including emitting and splitting a laser beam, generating first data and second data, processing the first data and the second data, and calculating the concentration of the gas to be measured.

[0051] Specifically, a laser beam is emitted and split, with the wavelength corresponding to the characteristic wavelength of the absorption spectrum of the gas to be measured. A beam splitter is then used to split the laser beam into at least two beams, one of which serves as the measurement beam and passes through a hollow-core optical fiber. The measurement beam uses a laser beam with a wavelength that matches the characteristic wavelength of the absorption spectrum of the gas molecules to ensure that the gas molecules can effectively absorb the laser energy, thereby facilitating the measurement of gas concentration based on the degree of intensity reduction of the measurement beam. The hollow-core optical fiber is also used to guide the interaction between the laser beam and the gas to be measured, improving the efficiency of the interaction between the laser and the gas.

[0052] The other beam serves as a reference beam and passes through a reference gas chamber. The reference beam is used to provide a light intensity benchmark to eliminate the influence of laser fluctuations.

[0053] The first data and the second data are generated by detecting the light intensities of the measuring beam and the reference beam using photodetectors, respectively. The photodetector is a light sensor that measures the light intensity of a light beam and converts the light signal into an electrical signal. The light intensity of the measuring beam is converted into the first data, and the light intensity of the reference beam is converted into the second data. These data reflect the degree of light absorption by the gas.

[0054] The first and second data are processed using a lock-in amplifier, which amplifies signals in the first data that have the same frequency and phase as the second data, generating third data. A lock-in amplifier is a signal processing instrument that can extract signals of a specific frequency from a strong noise background. The lock-in amplifier only amplifies signals that have the same frequency and phase as the reference signal, the second data, thereby filtering out noise and generating a more accurate signal. This processed signal, the third data, has a higher signal-to-noise ratio and more accurately reflects gas absorption information.

[0055] The concentration of the gas to be measured is calculated using a data processing unit based on the third data and the Lambert-Beer law. The data processing unit is used to perform data analysis and calculations. By measuring the light intensity attenuation, the gas concentration can be calculated.

[0056] Specifically, generating the first data and the second data includes using a photodetector to respectively detect the light intensity of the measurement light beam passing through the hollow-core optical fiber and the reference light beam passing through the reference gas chamber, converting the optical signal into an electrical signal, thereby generating the first data representing the measurement light intensity and the second data representing the reference light intensity.

[0057] Finally, it should be pointed out that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways without departing from the scope of the present invention.

Claims

1. A gas detection device based on hollow-core optical fiber, characterized by: include, A laser (2) is used to emit a laser beam having a wavelength corresponding to a characteristic wavelength of the absorption spectrum of the gas to be measured; a beam splitter (3), connected to the laser (2), and configured to split the laser beam into a first laser beam and a second laser beam; A hollow-core optical fiber (7), arranged on one side of the beam splitter (3), for carrying the gas to be measured and passing the first laser beam; A reference gas chamber (6) is provided on one side of the beam splitter (3) and is used for passing the second laser beam.

2. The hollow-core optical fiber-based gas detection device according to claim 1, characterized in that: Also includes, A gas pool (5) is arranged between the hollow-core optical fiber (7) and the beam splitter (3), and one end of the hollow-core optical fiber (7) is sealed in the gas pool (5).

3. The hollow-core optical fiber-based gas detection device according to claim 2, characterized in that: Also includes, A first optical calibration component (4) is arranged between the beam splitter (3) and the gas pool (5), and the first optical calibration component (4) focuses the first laser beam into the core of the hollow-core optical fiber (7).

4. The hollow-core optical fiber-based gas detection device according to claim 3, characterized in that: Also includes, a second optical calibration component (12), arranged on a side of the hollow-core optical fiber (7) away from the gas pool (5), and used for focusing the first laser beam passing through the hollow-core optical fiber (7); A first photodetector (8) faces the second optical calibration component (12), and the photodetector (8) receives the first laser beam and generates first data.

5. The hollow-core optical fiber-based gas detection device according to claim 4, characterized in that: Also includes, a third optical calibration component (13) disposed between the beam splitter (3) and the reference gas chamber (6), the third optical calibration component (13) focusing the second laser beam into the reference gas chamber (6); The second photodetector (14) is arranged on a side of the reference gas chamber (6) away from the third optical calibration component (13), receives the second laser beam passing through the reference gas chamber (6) and generates second data.

6. The hollow-core optical fiber-based gas detection device according to claim 5, characterized in that: Also includes, A lock-in amplifier (9) is connected to the first photodetector (8) and the second photodetector (14), and amplifies a signal in the first data having the same frequency and phase as the second data to generate third data.

7. The hollow-core optical fiber-based gas detection device according to claim 6, characterized in that: Also includes, A data acquisition component (10) is connected to the lock-in amplifier (9) and the data processing component (11) and samples the third data; The data processing unit (11) receives the third data and obtains a second harmonic signal according to the Lambert-Beer law.

8. The hollow-core optical fiber-based gas detection device according to claim 7, characterized in that: The laser (2) is a quantum cascade laser, and the central wavelength of the laser beam is 1504 cm -1 , the gas to be measured is SO2F2.

9. A gas detection method based on hollow-core optical fiber, characterized by: ， emitting and splitting a laser beam, emitting a laser beam with a wavelength corresponding to a characteristic wavelength of the absorption spectrum of the gas to be measured, and using a beam splitter to split the laser beam into at least two beams, one as a measurement beam passing through a hollow-core optical fiber, and the other as a reference beam passing through a reference gas chamber; generating first data and second data, using a photodetector to detect the light intensities of the measuring beam and the reference beam respectively, and generating the first data and the second data; Processing first data and second data, processing the first data and the second data using a lock-in amplifier, amplifying a signal in the first data having the same frequency and phase as the second data, to generate third data; The concentration of the gas to be measured is calculated using a data processing component based on the third data and in combination with the Lambert-Beer law to obtain the concentration of the gas to be measured.

10. The hollow-core optical fiber-based gas detection device according to claim 9, characterized in that: The generating of the first data and the second data includes using a photodetector to respectively detect the light intensity of the measuring light beam passing through the hollow-core optical fiber and the reference light beam passing through the reference gas chamber, converting the optical signals into electrical signals, thereby generating first data representing the measuring light intensity and second data representing the reference light intensity.

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