Gas sensing system and method based on cyclic incident pumping enhanced photoacoustic cell

Abstract

The invention provides a gas sensing system and method based on a circulating incident pumping enhanced photoacoustic cell, and belongs to the technical field of gas detection, the system comprises an excitation light source 1, a one-way isolator 2, an optical coupler 3, a circulating incident photoacoustic cell 4, an optical amplifier 5, a wavelength division multiplexer 6, a 980nm pumping light source 7, a data acquisition card 8, an upper computer 9 and a signal generator 10, laser enters the circulating incident photoacoustic cell 4 through the optical coupler 3 and generates a photoacoustic effect with gas to be detected, output light passes through the optical amplifier 5, is combined with a 980nm pump light source 7 in the wavelength division multiplexer 6 and is output to the optical coupler 3, and the output light is coupled with initial laser and enters the circulating incident photoacoustic cell 4 to form circulation; and the data acquisition card 8 and the upper computer 9 are used for acquiring and processing photoacoustic signals to obtain a gas concentration result. According to the invention, the intensity of the photoacoustic signal is improved through the circulating pumping structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas detection, and particularly relates to a gas sensing system and method based on a circulating incident pump enhanced photoacoustic cell. BACKGROUND

[0002] Photoacoustic spectroscopy is an indirect gas detection method based on infrared absorption, which has the advantages of high sensitivity and low detection limit, and is widely used in power system fault detection. The technology realizes the measurement of the concentration of the target gas through the photoacoustic effect, and the intensity of the photoacoustic signal is positively correlated with the intensity of the incident laser. In the traditional photoacoustic spectroscopy gas detection system, a distributed feedback (DFB) laser with low output power is usually used as the light source, and the incident light generated in the photoacoustic cell is reflected a limited number of times to enhance the photoacoustic signal. However, due to the limitations of the laser output power and the physical size and consumption of the photoacoustic cell, the light intensity in the cell cannot be effectively accumulated, resulting in that the incident light is still difficult to excite a photoacoustic signal with ideal intensity after multiple reflections, which restricts the further improvement of the detection sensitivity and the minimum detection limit of the system.

[0003] The patent document with the publication number CN119534329A discloses a photoacoustic cell for gas photoacoustic spectroscopy detection, which includes a first photoacoustic cell group and a second photoacoustic cell group. Each acoustic-optic cell group contains two acoustic-optic cells arranged symmetrically and in communication with each other. By filling the two acoustic-optic cells with the gas to be measured and pure gas respectively, first and second sound signals are obtained. A double sound signal is obtained through a differential amplifier. This method improves the sensitivity of detection by connecting two photoacoustic cells in parallel to each photoacoustic cell based on the parallel double photoacoustic cell gas concentration measurement device, thereby obtaining a double sound signal. However, this method of connecting multiple photoacoustic cells in parallel limits the miniaturization of the measurement device. SUMMARY

[0004] To solve the problems in the prior art, the application provides a gas sensing system and method based on a circulating incident pump enhanced photoacoustic cell. The system uses a closed-loop pumping structure to amplify and inject the exiting light of the circulating incident photoacoustic cell again, thereby overcoming the limitation of light intensity in the traditional structure and improving the signal-to-noise ratio and detection sensitivity.

[0005] The technical solution of the application is as follows: In a first aspect, the application provides a gas sensing system based on a circulating incident pump enhanced photoacoustic cell, which includes: An excitation light source connected to a signal generator, the signal generator generates a modulation signal of a specific frequency to drive the excitation light source to emit laser light with the same wavelength as the absorption peak of the gas to be measured; A unidirectional isolator for unidirectional transmission of laser light; A light coupler receives the laser and the circulating amplified light and outputs the circulating amplified light to the circulating incident photoacoustic cell; A circulating incident photoacoustic cell is used for generating a photoacoustic effect of the to-be-detected gas and the laser; A light amplifier is used for light amplification of the output light of the circulating incident photoacoustic cell; A wavelength division multiplexer receives the output light of the light amplifier and the output light of the 980 nm pump light source, combines the two lights and outputs the circulating amplified light; A data acquisition card acquires the photoacoustic effect signal and processes the signal; An upper computer inverses the concentration of the to-be-detected gas through the signal processed by the data acquisition card and sends a control instruction to the signal generator.

[0006] Further, the circulating incident photoacoustic cell comprises: A circulating incident photoacoustic cell main structure, a first collimating mirror mounting module, a second collimating mirror mounting module, an excitation light collimating and incident module and an excitation light collecting module; The circulating incident photoacoustic cell main structure is provided with a first buffer cavity and a second buffer cavity at two ends to reduce photoacoustic noise; A resonance cavity is arranged between the first buffer cavity and the second buffer cavity; The circulating incident photoacoustic cell main structure is provided with an air inlet hole and an air outlet hole at the top to fill the to-be-detected gas into the resonance cavity; The top is also provided with a microphone pickup hole connected to a microphone to detect the photoacoustic signal.

[0007] Further, the first collimating mirror mounting module is provided with an incident collimating guide rail for mounting the excitation light collimating and incident module and adjusting the position thereof; The second collimating mirror mounting module is provided with a receiving collimating guide rail for mounting the excitation light collecting module and adjusting the position thereof.

[0008] Further, the excitation light collimating and incident module comprises a receiving light ceramic plug core, an excitation light collimating base and an incident collimating lens, the receiving light ceramic plug core and the incident collimating lens being installed in the excitation light collimating base along the light path; The excitation light collecting module comprises a receiving light ceramic plug core, a receiving light collimating base and a receiving collimating lens, the receiving light ceramic plug core and the receiving collimating lens being installed in the receiving light collimating base along the light path.

[0009] Further, the light amplifier adopts a doped fiber.

[0010] In a second aspect, the application provides a gas sensing method based on a circulating incident pump enhanced photoacoustic cell, comprising the following steps: The to-be-detected gas is filled into the resonance cavity of the circulating incident photoacoustic cell from the air inlet hole and discharged from the air outlet hole, and the to-be-detected gas flows in the resonance cavity; The host computer sends control commands to the signal generator, which generates a modulation signal of a specific frequency to drive the excitation light source to output laser light. The wavelength of the laser light is the same as the wavelength of the absorption peak of the gas to be measured. A laser is coupled into a cyclic incident photoacoustic cell, which generates a photoacoustic effect with the gas to be tested in the resonant cavity. Collect the emitted laser light from the cyclically incident photoacoustic cell and amplify the power of the emitted laser light; The amplified output laser is combined with the pump light and then coupled with the original laser, and then re-injected into the cyclic incident photoacoustic cell to form a cyclic pump enhancement optical path. The photoacoustic signal generated in the resonant cavity is collected, and the converted data is sent to the host computer. The host computer processes and displays the collected photoacoustic signal to obtain the concentration information of the gas to be measured.

[0011] Furthermore, the process of coupling the laser into the cyclic incident photoacoustic cell specifically involves: The laser passes through a unidirectional isolator to form a unidirectional transmission laser. The unidirectional transmission laser enters the optical coupler. When no cyclic pump enhancement optical path is formed at the beginning of operation, the unidirectional transmission laser is directly output into the cyclic incident photoacoustic cell. Once the cyclic pump-enhanced optical path is formed, the optical coupler couples the laser and the pump-enhanced light into the cyclic incident photoacoustic cell.

[0012] Furthermore, erbium-doped fiber is used to amplify the power of the emitted laser from the cyclic incident photoacoustic cell.

[0013] Furthermore, a wavelength division multiplexer is used to combine the amplified outgoing laser with the pump light wave.

[0014] Furthermore, the pump light source is a 980nm pump light source.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: By introducing a cyclic pumping structure into a traditional photoacoustic cell system, under the condition that the output power of the excitation light source remains unchanged, the closed-loop pumping structure is used to cyclically amplify and re-inject the light emitted from the cyclically incident photoacoustic cell. This is equivalent to increasing the number of times the light interacts with the resonant cavity and the total power, which significantly enhances the effective light intensity in the cell. This improves the photoacoustic signal intensity and the system's detection sensitivity, overcoming the detection performance bottleneck caused by the limited laser power and insufficient reflection times in traditional technologies. Attached Figure Description

[0016] Figure 1 A schematic diagram of a gas sensing system based on a cyclic incident pump-enhanced photoacoustic cell; Figure 2 A three-dimensional view of the cyclic incident photoacoustic cell; Figure 3 This is a side perspective view of the cyclic incident photoacoustic cell; Figure 4 A schematic diagram of the split structure of the cyclic incident photoacoustic cell; Figure 5 Three-dimensional perspective view of the excitation light collimation and excitation light collection module; Figure 6 A schematic diagram showing the disassembled structure of the excitation light collimation and excitation light collection modules; The reference numerals in the figure indicate: 1. Excitation light source; 2. Unidirectional isolator; 3. Optical coupler; 4. Circulating incident photoacoustic cell; 5. Optical amplifier; 6. Wavelength division multiplexer; 7. 980nm pump light source; 8. Data acquisition card; 9. Host computer; 10. Signal generator; 41. Main structure of the circulating incident photoacoustic cell; 42. First collimating lens mounting module; 43. Second collimating lens mounting module; 44. Excitation light collimated incident module; 45. Excitation light collection module; 411. First buffer cavity; 412. Microphone pickup hole; 413. Air inlet; 414. Exhaust port; 415. Resonant cavity; 416. Second buffer cavity; 421. Incident collimation guide rail; 431. Receiver collimation guide rail; 441. Excitation beam ceramic ferrule; 442. Excitation beam collimation base; 443. Incident collimation lens; 451. Receiver beam ceramic ferrule; 452. Receiver beam collimation base; 453. Receiver collimation lens. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Example 1 This embodiment provides a gas sensing system based on a cyclic incident pump-enhanced photoacoustic cell, such as... Figure 1 As shown, the system includes: 1. Excitation light source; 2. Unidirectional isolator; 3. Optical coupler; 4. Circulating incident photoacoustic cell; 5. Optical amplifier; 6. Wavelength division multiplexer; 7. 980nm pump light source; 8. Data acquisition card; 9. Host computer; and 10. Signal generator. The input terminal a of the optical coupler 3 is connected to the output terminal of the unidirectional isolator 2, the input terminal b is connected to the output terminal h of the wavelength division multiplexer 6, and the output terminal c is connected to the cyclic incident photoacoustic cell 4. The original excitation light and the amplified light returning in the cycle are coupled together and incident into the cyclic incident photoacoustic cell 4. The input terminal d of the optical amplifier 5 is connected to the output terminal of the cyclic incident photoacoustic cell 4, the input terminal f of the wavelength division multiplexer 6 is connected to the output terminal e of the optical amplifier 5, and the input terminal g is connected to the output terminal of the 980nm pump light source 7. The optical signal amplified by the optical amplifier 5 is combined with the pump light. Optical coupler 3, cyclic incident photoacoustic cell 4, optical amplifier 5, wavelength division multiplexer 6 and 980nm pump light source 7 together constitute a cyclic pump enhancement structure, which is used to enhance the laser energy circulating inside the cyclic incident photoacoustic cell 4.

[0019] like Figure 2 As shown, the circulating incident photoacoustic cell 4 includes: a circulating incident photoacoustic cell main structure 41, a first collimating lens mounting module 42, a second collimating lens mounting module 43, an excitation light collimating incident module 44, and an excitation light collection module 45; like Figure 3 and Figure 4 As shown, the main structure 41 of the cyclic incident photoacoustic cell is provided with a first buffer cavity 411, a microphone pickup hole 412, an air inlet 413, an exhaust hole 414, a resonant cavity 415, and a second buffer cavity 416; the excitation light collimating incident module 44 is installed at one end of the main structure 41 of the cyclic incident photoacoustic cell via an incident collimating guide rail 421 and is fixed to the first collimating lens mounting module 42, and is used to collimate the incident fiber light signal and couple it into the resonant cavity 415; the excitation light collecting module 45 is installed at the other end of the main structure 41 of the cyclic incident photoacoustic cell via a receiving collimating guide rail 431 and is fixed to the second collimating lens mounting module 43, and is used to collect and couple the light signal emitted from the resonant cavity 415; like Figure 5 and Figure 6 As shown, the excitation light collimating incident module 44 includes an excitation light ceramic ferrule 441, an excitation light collimating base 442, and an incident collimating lens 443. The excitation light ceramic ferrule 441 and the incident collimating lens 443 are installed directly inside the excitation light collimating base 442 along the optical path. The excitation light collecting module 45 includes a receiving light ceramic ferrule 451, a receiving light collimating base 452, and a receiving collimating lens 453. The receiving light ceramic ferrule 451 and the receiving collimating lens 453 are installed directly inside the receiving light collimating base 452 along the optical path. The spatial position of the incident collimating lens 443 is adjusted by the incident collimating guide rail 421, and the spatial position of the receiving collimating lens 453 is adjusted by the receiving collimating guide rail 431 to achieve precise alignment of the optical path.

[0020] The working process of the gas sensing system based on the cyclic incident pump-enhanced photoacoustic cell is as follows: The host computer 9 controls the signal generator 10 to generate a modulation signal of a specific frequency, driving the excitation light source 1 to emit excitation light with a wavelength tuned to the absorption peak of the target gas. This excitation light is transmitted unidirectionally through the unidirectional isolator 2 and enters the input end a of the optical coupler 3. Initially, there is no input light at the input end b. The light output from the output end c enters the excitation light collimation and incidence module 44 through the optical fiber. The collimated light passes through the first buffer cavity 411, the resonant cavity 415, and the second buffer cavity 416 in sequence. It is collected by the excitation light collection module 45 and output to the optical amplifier 5 to achieve optical amplification. It is then combined with the pump light of the 980nm pump light source 7 through the wavelength division multiplexer 6 and fed back to the input end b of the optical coupler 3. It is coupled with the excitation light at the input end a at a power split ratio of 50:50 and re-enters the cyclic incident photoacoustic cell 4 to form a closed-loop cyclic amplification optical path. By reasonably setting the optical path component parameters, the light can be circulated more than 100 times in the cyclic incident photoacoustic cell, and the light intensity can be effectively accumulated. Inside the resonant cavity 415, the cyclically enhanced laser interacts with the gas to be tested entering through the air inlet 413 to produce a photoacoustic effect, generating a sound wave with significantly enhanced intensity. This sound wave is detected by a high-sensitivity condenser microphone mounted on the microphone pickup hole 412 and converted into an electrical signal. The electrical signal is acquired and converted from analog to digital by the data acquisition card 8, and then uploaded to the host computer 9. The signal is processed by algorithms such as digital lock-in amplification to retrieve the gas concentration and display it, thus completing the high-sensitivity gas concentration measurement.

[0021] Preferably, the optical amplifier 5 uses erbium-doped fiber.

[0022] Example 2 This embodiment provides a gas sensing method based on a cyclic incident pump-enhanced photoacoustic cell, comprising the following steps: The gas to be measured is filled into the resonant cavity 415 of the circulating incident photoacoustic cell 4 through the air inlet 413 and discharged from the exhaust port 414 to realize the continuous flow measurement of the gas to be measured. The host computer 9 sends control commands to the signal generator 10 through the human-machine interface. The signal generator 10 generates a modulation signal of a specific frequency to drive the excitation light source 1 to output laser. The wavelength of the laser is the same as the wavelength of the absorption peak of the gas to be measured, so that it can scan the absorption spectrum of the gas to be measured. A laser is coupled into the cyclic incident photoacoustic cell 4, and interacts with the gas to be tested in the resonant cavity 415 to produce a photoacoustic effect. Collect the emitted laser light from the cyclic incident photoacoustic cell 4 and amplify the power of the emitted laser light; The amplified outgoing laser is combined with the pump light and then coupled with the original laser, and then re-injected into the cyclic incident photoacoustic cell 4 to form a cyclic pump enhancement optical path, thereby enhancing the effective laser power in the photoacoustic cell. The photoacoustic signal generated in the resonant cavity 415 is collected, and the converted data is sent to the host computer 9. The host computer 9 processes and displays the collected photoacoustic signal to obtain the concentration information of the gas to be measured.

[0023] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A gas sensing system based on a cyclically incident pumped enhanced photoacoustic cell, characterized in that, The system includes: An excitation light source (1) is connected to a signal generator (10). The signal generator (10) generates a modulation signal of a specific frequency to drive the excitation light source (1) to emit laser light with the same wavelength as the absorption peak of the gas to be measured. One-way isolator (2) is used for one-way laser transmission; Optical coupler (3) receives laser light and cyclic amplified light and couples the output to the cyclic incident photoacoustic cell (4). A circulating incident photoacoustic cell (4) is used to generate a photoacoustic effect between the gas to be tested and the laser. Optical amplifier (5) is used to amplify the output light of the cyclic incident photoacoustic cell (4); The wavelength division multiplexer (6) receives the output light of the optical amplifier (5) and the output light of the 980nm pump light source (7), and outputs the loop-amplified light after combining them. Data acquisition card (8) acquires photoacoustic effect signals and performs signal processing; The host computer (9) retrieves the concentration of the gas to be measured from the signal processed by the data acquisition card (8) and sends control commands to the signal generator (10).

2. The gas sensing system based on a cyclically incident pumped enhanced photoacoustic cell according to claim 1, characterized in that, The circulating incident photoacoustic cell (4) includes: The main structure of the circulating incident photoacoustic cell (41), the first collimating lens mounting module (42), the second collimating lens mounting module (43), the excitation light collimating incident module (44), and the excitation light collection module (45) are all included. The main structure (41) of the circulating incident photoacoustic cell is provided with a first buffer cavity (411) and a second buffer cavity (416) at both ends. The first buffer cavity (411) and the second buffer cavity (416) are used to reduce photoacoustic noise. A resonant cavity (415) is provided between the first buffer cavity (411) and the second buffer cavity (416). An air inlet (413) and an exhaust (414) are opened on the top of the main structure (41) of the circulating incident photoacoustic cell to fill the resonant cavity (415) with the gas to be tested; A microphone pickup hole (412) is also provided at the top to connect a microphone to detect photoacoustic signals.

3. A gas sensing system based on a cyclic incident pump-enhanced photoacoustic cell according to claim 2, characterized in that, The first collimating lens mounting module (42) is provided with an incident collimating guide rail (421) for mounting the excitation light collimating incident module (44) and adjusting its position; The second collimating lens mounting module (43) is provided with a receiving collimating guide rail (431) for mounting the excitation light collecting module (45) and adjusting its position.

4. A gas sensing system based on a cyclically incident pumped enhanced photoacoustic cell according to claim 2, characterized in that, The excitation light collimation incident module (44) includes a receiving light ceramic ferrule (441), an excitation light collimation base (442), and an incident collimation lens (443). The excitation light ceramic ferrule (441) and the incident collimation lens (443) are installed inside the excitation light collimation base (442) along the light path. The excitation light collection module (45) includes a light receiving ceramic ferrule (451), a light receiving collimation base (452), and a light receiving collimation lens (453). The light receiving ceramic ferrule (451) and the light receiving collimation lens (453) are installed inside the light receiving collimation base (452) along the light path.

5. A gas sensing system based on a cyclically incident pumped enhanced photoacoustic cell according to claim 2, characterized in that, The optical amplifier (5) uses erbium-doped fiber.

6. A gas sensing method based on a cyclically incident pump-enhanced photoacoustic cell, characterized in that, Includes the following steps: The gas to be tested is filled into the resonant cavity (415) of the circulating incident photoacoustic cell (4) through the air inlet (413) and discharged through the exhaust port (414). The gas to be tested flows in the resonant cavity (415). The host computer (9) sends control commands to the signal generator (10), and the signal generator (10) generates a modulation signal of a specific frequency to drive the excitation light source (1) to output laser. The wavelength of the laser is the same as the wavelength of the absorption peak of the gas to be measured. The laser is coupled into the cyclic incident photoacoustic cell (4) and generates a photoacoustic effect with the gas to be tested in the resonant cavity (415); Collect the emitted laser from the cyclic incident photoacoustic cell (4) and amplify the power of the emitted laser. The amplified output laser is combined with the pump light and then coupled with the original laser, and then re-injected into the cyclic incident photoacoustic cell (4) to form a cyclic pump enhancement optical path. The photoacoustic signal generated in the resonant cavity (415) is collected, and the converted data is sent to the host computer (9). The host computer (9) processes and displays the collected photoacoustic signal to obtain the concentration information of the gas to be measured.

7. A gas sensing method based on a cyclically incident pumped enhanced photoacoustic cell according to claim 6, characterized in that, The process of coupling the laser into the cyclic incident photoacoustic cell (4) specifically involves: The laser passes through the unidirectional isolator (2) to form a unidirectional transmission laser. The unidirectional transmission laser enters the optical coupler (3). When no cyclic pump enhancement optical path is formed at the beginning of operation, the unidirectional transmission laser is directly output into the cyclic incident photoacoustic cell (4). Once the cyclic pump-enhanced optical path is formed, the optical coupler (3) couples the laser and the pump-enhanced light into the cyclic incident photoacoustic cell (4).

8. A gas sensing method based on a cyclically incident pumped enhanced photoacoustic cell according to claim 6, characterized in that, The power of the emitted laser from the cyclic incident photoacoustic cell (4) is amplified by using erbium-doped fiber.

9. A gas sensing method based on a cyclically incident pumped enhanced photoacoustic cell according to claim 6, characterized in that, A wavelength division multiplexer is used to combine the amplified output laser with the pump light.

10. A gas sensing method based on a cyclically incident pumped enhanced photoacoustic cell according to claim 6, characterized in that, The pump light source is a 980nm pump light source.

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