Alcohol gas concentration remote sensing device based on mode division multiplexing transmission

Abstract

An alcohol gas concentration remote sensing device based on mode division multiplexing transmission relates to the field of biomedical measurement technology. It aims to solve the problems of low measurement accuracy and high false alarm rate in the process of non-contact measurement of alcohol content in human exhaled breath. The device comprises a semiconductor laser, an erbium-doped fiber amplifier, a wavelength division multiplexer, a thulium-holmium co-doped double-clad fiber, a few-mode optical isolator, a mode selector, a few-mode optical coupler, a polarization controller, a second optical coupler, a first optical coupler, a first optical fiber collimator, a Kepler beam compressor, a two-color beam splitter, a first receiving lens, a first photodetector, a second receiving lens, a few-mode receiving fiber, a mode demultiplexer, a second photodetector, a third photodetector, a fourth photodetector, an analog-to-digital converter, an FPGA, and a microcomputer. According to the different alcohol absorption laws of different mode light beams during the test or analysis of the alcohol content in human exhaled breath, the receiving end performs multi-mode diversity reception, and the alcohol content is deciphered in multiple modes to improve the measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of biomedical measurement technology, and in particular to an alcohol gas concentration remote sensing device based on mode division multiplexing transmission, which uses the physical property of alcohol's absorption of infrared light of a specific wavelength to test or analyze the alcohol content in human exhaled gas. Background Art

[0002] Exhaled breath alcohol testing is a key component of medical diagnosis and workplace drug testing. It helps doctors understand a patient's drinking patterns and alcohol use. It can also be used to regularly test employees for alcohol use to ensure they are sober at work. Traditional contact testing methods, such as breathalyzers and alcohol test strips, are inefficient and can sometimes prevent testing due to employee non-compliance. Therefore, a non-contact method for measuring exhaled breath alcohol is needed.

[0003] However, the existing commonly used non-contact alcohol gas concentration remote sensing methods mostly use a single light beam or a single light beam array for measurement. The use of single-beam single-beam mode measurement has the problems of low measurement accuracy and high false alarm rate. For example, the Chinese patent application number "ZL202410797187", named "1.7μm band noise-like-Bessel-Gaussian beam alcohol concentration remote sensing device", is characterized in that the device includes a semiconductor laser, an erbium-doped fiber amplifier, a wavelength division multiplexer 1, a thulium-holmium co-doped fiber, a wavelength division multiplexer 2, a single-mode fiber, a polarization controller 1, a coupler, a multi-mode fiber, a polarization controller 2, a fiber collimator 1, a filter, a reflector, a fiber collimator 2, a convex lens 1, a convex lens 2, a polarizer and a near-infrared emitting light source composed of a spatial light modulator, as well as a fiber collimator 3, a photodetector and a data acquisition and processing unit.

[0004] The device uses a noise-like Bessel-Gaussian beam to reduce beam deviation and intensity jitter, which can somewhat mitigate environmental influences. However, its single beam pattern results in low measurement accuracy when detecting alcohol content in human exhaled breath. Furthermore, numerous false positives are difficult to resolve in practice, such as uneven distribution of alcohol vapor, leading to a high false alarm rate during testing. Summary of the Invention

[0005] In order to solve the problems of low measurement accuracy and high false alarm rate in the process of contactless measurement of alcohol content in human exhaled gas, the present invention proposes an alcohol gas concentration remote sensing device based on mode division multiplexing transmission.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] The alcohol gas concentration remote sensing device based on mode division multiplexing transmission includes: a semiconductor laser, an erbium-doped fiber amplifier, a wavelength division multiplexer, a thulium-holmium co-doped double-clad fiber, a few-mode optical isolator, a mode selector, a few-mode optical coupler, a polarization controller, a second optical coupler, a first optical coupler, a first optical fiber collimator, a Kepler beam reducer, a two-color beam splitter, a first receiving lens, a first photodetector, a second receiving lens, a few-mode receiving fiber, a mode demultiplexer, a second photodetector, a third photodetector, a fourth photodetector, and an analog-to-digital converter. converter, FPGA and microcomputer; the semiconductor laser fiber output is sequentially connected to the erbium-doped fiber amplifier and the optical coupler 1; the output of the optical coupler 1 is divided into two, one end is connected to the optical coupler 2, and the other end is connected to the 1550nm fiber end of the wavelength division multiplexer; the beam combining end of the wavelength division multiplexer is sequentially connected to the thulium-holmium co-doped double-clad fiber, the few-mode optical isolator, the polarization controller, the few-mode optical coupler, the mode selector, and the 1700nm fiber end of the wavelength division multiplexer to form a ring structure; the output end of the few-mode optical coupler is connected to the Optical coupler 2 is connected by optical fiber, and the output optical fiber end face of optical coupler 2 is located at the focal plane of optical fiber collimator 1; optical fiber collimator 1, the person being measured and Kepler beam reducer are arranged in a straight line in sequence, wherein the optical axis of optical fiber collimator 1, the front of the nose of the person being measured and the optical axis of Kepler beam reducer are aligned; the normal direction of the two-color beam splitter is rotated 45 degrees clockwise from the output optical axis of the Kepler beam reducer; receiving lens 1 is aligned with the reflection axis of the two-color beam splitter, and photodetector 1 is located at the focal plane of receiving lens 1; the output cable of photodetector 1 is connected to the analog-to-digital converter; receiving lens 2 is aligned with the transmission axis of the two-color beam splitter, and the few-mode receiving optical fiber is located at the focal plane of receiving lens 2; the output optical fiber of the few-mode receiving optical fiber is connected to the mode demultiplexer in sequence, and the three output ends of the mode demultiplexer are respectively connected to photodetector 2, photodetector 3 and photodetector 4 by optical fibers; the output ends of the three photodetectors are connected to the analog-to-digital converter through cables; the multi-channel cable of the analog-to-digital converter is connected to the FPGA; the FPGA is connected to the microcomputer through a cable, and the data generated by the FPGA is collected by the microcomputer.

[0008] The Keplerian beam reducer includes a front lens and a rear lens.

[0009] The semiconductor laser outputs 1550nm pump light, which is amplified by an erbium-doped fiber amplifier. A portion of the light enters the input end of the optical coupler 2 through the optical coupler 1; the other portion of the light is injected into the ring structure through the wavelength division multiplexer, wherein the ring structure components sequentially include a thulium-holmium co-doped double-clad optical fiber, a few-mode optical isolator, a polarization controller, a few-mode optical coupler, a mode selector, and a wavelength division multiplexer. The pump light injected by the wavelength division multiplexer into the thulium-holmium co-doped double-clad optical fiber produces a wide range of gain spectrum, the few-mode optical isolator maintains unidirectional oscillation in the ring structure, the polarization controller controls the polarization state of the light in the ring structure, the mode selector selects the number of modes of oscillation in the ring structure, and the few-mode optical coupler is used to partially output the generated light;

[0010] The 1700nm band few-mode light beam generated by the few-mode optical coupler and the 1550nm pump light output by the optical coupler 1 are input into the optical coupler 2 together and are collimated and emitted through the optical fiber collimator 1. The collimated light passes through the person being measured and is then beam-contracted through the front lens and the rear lens of the Kepler beam reducer. The beam-contracted 1550nm pump light is reflected by the two-color beam splitter and enters the photodetector 1 through the receiving lens 1. The photodetector 1 converts the optical signal into an electrical signal and is collected by the analog-to-digital converter. The 1700nm band few-mode light beam is transmitted through the two-color beam splitter and enters the few-mode receiving optical fiber and the mode demultiplexer. The few-mode light beam is decomposed into three mode lights by the mode demultiplexer and each enters the photodetector 2. The photodetector 3 and the photodetector 4 complete the photoelectric conversion and output electrical signals, which are collected by the analog-to-digital converter. The analog-to-digital converter converts the electrical signals collected by multiple photodetectors into digital signals and transmits them into the FPGA. The microcomputer receives the signal of the FPGA to complete the signal collection.

[0011] The beneficial effects of the present invention are:

[0012] 1) The present invention assumes that the signal distortion of light beams of different wavelengths and modes is approximately the same under the influence of the channel environment. By performing differential detection on light beams of different wavelengths and modes, the error caused by airflow and the like in the actual measurement process can be reduced, thereby improving the measurement accuracy.

[0013] 2) The present invention uses different alcohol absorption patterns when testing or analyzing the alcohol content in human exhaled gas based on different light beam modes. The receiving end performs multi-mode diversity reception and deciphers the alcohol content in multiple modes, thereby improving the accuracy of alcohol measurement.

[0014] 3) This invention constructs a training dataset and a big data model based on the misjudgment and error characteristics of detection signal quality in various scenarios. During actual testing of alcohol content in human exhaled breath, this big data model assists in predicting alcohol concentration and reducing false alarm rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of the alcohol gas concentration remote sensing device based on mode division multiplexing transmission of the present invention.

[0016] Figure 2 A diagram showing the relationship between light intensity amplitude and alcohol concentration in an embodiment of the present invention. DETAILED DESCRIPTION

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

[0018] like Figure 1As shown, the alcohol gas concentration remote sensing device based on mode division multiplexing transmission includes: a semiconductor laser 1, an erbium-doped fiber amplifier 2, a wavelength division multiplexer 3, a thulium-holmium co-doped double-clad fiber 4, a few-mode optical isolator 5, a mode selector 6, a few-mode optical coupler 7, a polarization controller 8, an optical coupler 2 9, an optical coupler 1 10, an optical fiber collimator 1 11, a Kepler beam reducer 12, a two-color beam splitter 13, a receiving lens 1 14, a photodetector 1 15, a receiving lens 2 16, a few-mode receiving fiber 17, a mode demultiplexer 18, a photodetector 2 19, a photodetector 3 20, a photodetector 4 21, an analog-to-digital converter 22, an FPGA 23, and a microcomputer 24. The Kepler beam reducer 12 includes a front lens 12-1 and a rear lens 12-2.

[0019] The semiconductor laser 1 outputs an optical fiber that is sequentially connected to an erbium-doped fiber amplifier 2 and an optical coupler 10. The output of optical coupler 10 is split into two, one end connected to optical coupler 2 9 and the other end connected to the 1550nm fiber end of wavelength division multiplexer 3. The combined end of wavelength division multiplexer 3 is sequentially connected to a thulium-holmium co-doped double-clad fiber 4, a few-mode optical isolator 5, a polarization controller 8, a few-mode optical coupler 7, a mode selector 6, and the 1700nm fiber end of wavelength division multiplexer 3, forming a ring structure. The output end of few-mode optical coupler 7 is optically connected to optical coupler 2 9, and the output fiber end face of optical coupler 2 9 is located at the focal plane of fiber collimator 11. Fiber collimator 11, the person being measured, and Kepler beam reducer 12 are arranged in a straight line in space. The optical axis of fiber collimator 11, the front of the person being measured's nose, and the optical axis of Kepler beam reducer 12 are aligned. The output optical axis of Kepler beam reducer 12, rotated 45° clockwise, is aligned with the normal direction of dichroic beam splitter 13. Receiving lens 14 is aligned with the reflection axis of dichroic beam splitter 13, and photodetector 15 is located at the focal plane of receiving lens 14. The output cable of photodetector 15 is connected to analog-to-digital converter 22. Receiving lens 2 is aligned with the transmission axis of dichroic beam splitter 13, and few-mode receiving fiber 17 is located at the focal plane of receiving lens 2. The output of few-mode receiving fiber 17 is connected to mode demultiplexer 18. The three output ends of mode demultiplexer 18 are connected to photodetector 2 19, photodetector 3 20, and photodetector 4 21, respectively. The output cables of the three photodetectors are connected to analog-to-digital converter 22. The analog-to-digital converter 22 is connected to the FPGA 23 via multiple cables. The FPGA 23 is connected to the microcomputer 24 via cables, and the data generated by the FPGA 23 is collected by the microcomputer 24.

[0020] The working process of the alcohol gas concentration remote sensing device based on mode division multiplexing transmission of the present invention is as follows:

[0021] The semiconductor laser 1 outputs 1550nm pump light, which is amplified by the erbium-doped fiber amplifier 2. A portion of the light then passes through optical coupler 10 and enters the input end of optical coupler 2 9. Another portion of the light is injected into a ring structure via a wavelength division multiplexer 3. The ring structure components sequentially include a thulium-holmium co-doped double-clad fiber 4, a few-mode optical isolator 5, a polarization controller 8, a few-mode optical coupler 7, a mode selector 6, and the wavelength division multiplexer 3. The pump light injected by the wavelength division multiplexer 3 into the thulium-holmium co-doped double-clad fiber 4 produces a wide gain spectrum. The few-mode optical isolator 5 maintains unidirectional oscillation within the ring structure. The polarization controller 8 controls the polarization state of the light within the ring structure. The mode selector 6 selects the number of modes of oscillation within the ring structure. The few-mode optical coupler 7 is used to partially output the generated light.

[0022] The 1700nm band few-mode light beam generated by the few-mode optical coupler 7 and the 1550nm pump light output by the optical coupler 10 are input into the optical coupler 2 9 together and are collimated and emitted through the optical fiber collimator 11. The collimated light passes through the person being measured and is then beam-contracted through the front lens 12-1 and the rear lens 12-2 of the Kepler beam reducer 12. The beam-contracted 1550nm pump light is reflected by the two-color beam splitter 13 and enters the photodetector 15 through the receiving lens 14. The photodetector 15 converts the optical signal into an electrical signal and is collected by the analog-to-digital converter. The 1700nm band few-mode light beam is transmitted through the two-color beam splitter 13 and enters the few-mode receiving optical fiber 17 and the mode demultiplexer 18. The few-mode light beam is decomposed into three mode lights through the mode demultiplexer 18, each of which enters the photodetector 2 19. The photodetector 3 20 and the photodetector 4 21 complete the photoelectric conversion and output the electrical signal, which is collected by the analog-to-digital converter. The analog-to-digital converter 22 converts the electrical signals collected by the multiple photodetectors into digital signals and transmits them to the FPGA 23. The microcomputer 24 receives the signals from the FPGA 23 and completes the signal collection.

[0023] After completing signal acquisition, the discrete values ​​of light intensity and light intensity variance under different modes are obtained. First, differential detection and big data models are used to help eliminate false alarms and interference errors. Secondly, based on the calibration relationship curve between alcohol gas concentration and light intensity and light intensity variance under different modes, the alcohol gas concentration range value is calculated. Finally, the blood alcohol concentration range value is calculated based on the approximate formula of exhaled alcohol gas concentration and blood alcohol concentration.

[0024] Example:

[0025] The alcohol gas concentration remote sensing device based on mode division multiplexing transmission of the present invention was used to detect alcohol gas of different concentrations, verifying the feasibility of the device and method. The specific process is as follows:

[0026] First, the 1.5μm and 1.7μm laser beams have similar absorption peaks for water vapor and are affected similarly by airflow, but their absorption peaks for alcohol differ significantly (1.7μm is the peak absorption peak for alcohol). Differential detection methods are used to minimize the effects of water vapor, airflow, and alcohol variations (within 100 Hz).

[0027] Fiber collimator 11 aligns the transmitting optical axis with the receiving optical axis of Kepler beam reducer 12. Exhaled gas is positioned on the optical axis. Laser beams in the 1.5μm and 1.7μm bands pass through the exhaled gas path. Four photodetectors detect the transmitted light through the exhaled alcohol. The light intensity detected by the photodetectors is proportional to the alcohol absorption concentration in accordance with Beer-Lambert's law. Photodetector 15 detects the 1.5μm laser beam, while photodetector 2 19, photodetector 3 20, and photodetector 4 21 detect the 1.7μm laser beam. Photodetectors 15, 19, 20, and 21 detect the light intensity. Photoelectric conversion generates an analog electrical signal, which is digitally sampled by an analog-to-digital converter 22 (operating at frequencies above MHz). FPGA 23 calculates the discrete values ​​of the light intensity and its variance based on the sampled signals. The effects of water vapor absorption and airflow vibration are extracted by differential detection of the 1.7μm and 1.5μm laser beams.

[0028] Secondly, based on the transmission characteristics of the three modes of light beams in the 1.7μm band, the absorption characteristics of the ambient alcohol gas, and combined with dual-wavelength differential detection, a calibration relationship curve between alcohol gas concentration and light intensity and light intensity variance is given, and the alcohol gas concentration range can be calculated.

[0029] In this example, the experiments were conducted at a constant temperature. 500 light intensity signal amplitude values ​​were collected over 10 seconds, and the amplitude point at the saturation stage was taken and calculated. Five groups of alcohol solutions with different concentrations were measured. The intensity amplitude information of the light beam after passing through the alcohol channel is shown in the following table:

[0030] Table 1 Alcohol test data results

[0031] Alcohol concentration (%) A B C D 9.1 0.072127 0.086197783 1.195083431 0.178216 18.4 0.071931 0.091175145 1.267536179 0.237075 28 0.068764 0.095643272 1.390891627 0.329945 38 0.065282 0.095564876 1.463877885 0.381089 47.1 0.064783 0.099423273 1.534712397 0.428343

[0032] Among them, the average value A of the detection electrical signal after alcohol absorption is , the average value B of the detection electrical signal without alcohol absorption is , the average value of the detection electrical signal after water vapor absorption is The average value of the detection electrical signal without water vapor absorption is , the alcohol gas light intensity amplitude feedback value C is , the logarithm D of the alcohol gas light intensity amplitude feedback is .

[0033] Fitting curve:

[0034] Fitting the functional relationship between alcohol gas x and the logarithm y of the light intensity amplitude feedback in the concentration range of 10%-50% is: y=0.48193x+0.00956, its linear fit is R²=0.9851, and the residual sum of squares RSS=0.000606. The results of the example show that the device can provide a feasible basis for alcohol concentration measurement. The fitting data obtained, such as Figure 2 As shown. In the prior art embodiment, the best fitting curve is 0.48193x-0.00956, which is a linear function, with a linear fit R²=0.96177 and a residual sum of squares RSS=0.00133. Therefore, the linear fit (0.9851) of the present invention is higher than that of the prior art (0.96177), while the residual sum of squares RSS is lower, indicating that the present invention has a smaller measurement error during the alcohol testing process and achieves better technical effects.

[0035] The blood alcohol concentration range can be calculated based on the approximate formula of breath alcohol concentration (BrAC) and blood alcohol concentration (BAC). The specific formula is as follows:

[0036]

[0037]

[0038] Among them, 2200 is the conversion coefficient between blood alcohol content and exhaled breath alcohol content, M is the molecular weight of alcohol, unit is g; T is temperature, unit is ℃; P is atmospheric pressure, unit is kPa; 22.4 is the molar volume of gas under standard conditions, unit is L / mol.

Claims

1. Alcohol gas concentration remote sensing device based on mode division multiplexing transmission, characterized in that include: Semiconductor laser (1), erbium-doped fiber amplifier (2), wavelength division multiplexer (3), thulium-holmium co-doped double-clad fiber (4), few-mode optical isolator (5), mode selector (6), few-mode optical coupler (7), polarization controller (8), optical coupler 2 (9), optical coupler 1 (10), optical fiber collimator 1 (11), Kepler beam reducer (12), two-color beam splitter (13), receiving lens 1 (14), photodetector 1 (15), receiving lens 2 (16), few-mode receiving fiber (17), mode demultiplexer (18), photodetector 2 (19), photodetector 3 (20), photodetector 4 (21), analog-to-digital converter (22), FPGA (23) and microcomputer (24); The semiconductor laser (1) outputs an optical fiber and is sequentially connected to an erbium-doped fiber amplifier (2) and an optical coupler (10); the output of the optical coupler (10) is split into two, one end of which is connected to an optical coupler (9) and the other end is connected to the 1550nm optical fiber end of the wavelength division multiplexer (3); the beam combining end of the wavelength division multiplexer (3) is sequentially connected to a thulium-holmium co-doped double-clad optical fiber (4), a few-mode optical isolator (5), a polarization controller (8), a few-mode optical coupler (7), a mode selector (6), and a wavelength division multiplexer (3). (3) of the 1700nm optical fiber end, forming a ring structure; the output end of the few-mode optical coupler (7) is connected to the optical fiber of the optical coupler 2 (9), and the output optical fiber end face of the optical coupler 2 (9) is located at the focal plane of the optical fiber collimator 1 (11); the optical fiber collimator 1 (11), the person being measured and the Kepler beam reducer (12) are arranged in a straight line in space, wherein the optical axis of the optical fiber collimator 1 (11), the front of the nose of the person being measured and the optical axis of the Kepler beam reducer (12) are aligned; and the Kepler beam reducer (12) The output optical axis is rotated 45° clockwise to be the normal direction of the two-color beam splitter (13); the receiving lens 1 (14) is aligned with the reflection axis of the two-color beam splitter (13), and the photodetector 1 (15) is located at the focal plane of the receiving lens 1 (14); the output cable of the photodetector 1 (15) is connected to the analog-to-digital converter (22); the receiving lens 2 (16) is aligned with the transmission axis of the two-color beam splitter (13), the few-mode receiving optical fiber (17) is located at the focal plane of the receiving lens 2 (16), and the output optical fiber of the few-mode receiving optical fiber (17) is connected to the mode demultiplexer (18), and the three output ends of the mode demultiplexer (18) are respectively connected to the photodetector 2 (19), the photodetector 3 (20) and the photodetector 4 (21); the output cables of the three photodetectors are connected to the analog-to-digital converter (22); the analog-to-digital converter (22) is connected to the FPGA (23) through a multi-channel cable; the FPGA (23) and the microcomputer (24) are connected through a cable, and the data generated by the FPGA (23) is collected by the microcomputer (24); The Kepler beam reducer (12) includes a front lens (12-1) and a rear lens (12-2).

2. The alcohol gas concentration remote sensing device based on mode division multiplexing transmission according to claim 1 is characterized in that: The semiconductor laser (1) outputs 1550nm pump light, which is amplified by the erbium-doped fiber amplifier (2). A portion of the light enters the input end of the optical coupler (9) through the optical coupler (10); the other portion of the light is injected into the ring structure through the wavelength division multiplexer (3), wherein the ring structure components include a thulium-holmium co-doped double-clad fiber (4), a few-mode optical isolator (5), a polarization controller (8), a few-mode optical coupler (7), a mode selector (6) and the wavelength division multiplexer (3) in sequence, wherein the pump light injected by the wavelength division multiplexer (3) into the thulium-holmium co-doped double-clad fiber (4) produces a wide range of gain spectrum, the few-mode optical isolator (5) maintains unidirectional oscillation in the ring structure, the polarization controller (8) controls the polarization state of the light in the ring structure, the mode selector (6) selects the number of modes of oscillation in the ring structure, and the few-mode optical coupler (7) is used to partially output the generated light; The 1700nm band few-mode light beam generated by the few-mode optical coupler (7) and the 1550nm pump light output by the optical coupler 1 (10) are input into the optical coupler 2 (9) and collimated and emitted through the optical fiber collimator 1 (11). The collimated light passes through the person being measured and is then beam-contracted through the front lens (12-1) and the rear lens (12-2) of the Kepler beam reducer (12). The beam-contracted 1550nm pump light is reflected by the two-color beam splitter (13) and enters the photodetector 1 (15) through the receiving lens 1 (14). The photodetector 1 (15) converts the optical signal into an electrical signal and collects it through the analog-to-digital converter. The 700nm band few-mode light beam is transmitted through the two-color beam splitter (13) into the few-mode receiving optical fiber (17) and the mode demultiplexer (18). The few-mode light beam is decomposed into three mode lights by the mode demultiplexer (18), and each mode light enters the photoelectric detector 2 (19). The photoelectric detector 3 (20) and the photoelectric detector 4 (21) complete the photoelectric conversion and output the electrical signal, which is collected by the analog-to-digital converter (22). The analog-to-digital converter (22) converts the electrical signals collected by the multiple photoelectric detectors into digital signals and transmits them into the FPGA (23). The microcomputer (24) receives the signal from the FPGA (23) to complete the signal collection.

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