Linear cavity gas concentration measuring device and method based on light feedback cavity enhancement

Abstract

The application provides a linear cavity gas concentration measuring device and method based on light feedback cavity enhancement, comprising a DFB laser, a first photodetector, a second photodetector, a fiber collimator, a polarization beam splitter, a first 1 / 4 wave plate, a second 1 / 4 wave plate, a linear resonant cavity, a piezoelectric ceramic, a transmissive-reflection mirror, a first total reflection plane mirror, a second total reflection plane mirror, an optical isolator and a gas filling assembly. The application separates the light output by the DFB laser according to the polarization state through the polarization beam splitter, feeds back the part of the output light of the linear resonant cavity into the DFB laser through the feedback light path by the transmissive-reflection mirror, and realizes the light feedback effect. The 1 / 4 wave plate arranged between the polarization beam splitter and the linear resonant cavity isolates the transmission light and the first reflection light of the front end mirror of the linear resonant cavity, so that the light does not return to the DFB laser, the influence of the light on the output mode of the laser is avoided, and the measurement precision of the gas concentration is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas concentration measurement, and particularly relates to a linear cavity gas concentration measurement device and method based on light feedback cavity enhancement. BACKGROUND

[0002] The gas concentration measurement device is an instrument device for accurately measuring gas concentration, which mainly detects gas concentration by using chemical or optical methods. The detection principles of existing gas concentration measurement devices are mainly gas chromatography, electrochemical detection method, semiconductor sensing method and gas tube detection method. However, these methods have some defects, for example, the gas chromatography needs to pretreat the gas sample; the electrochemical detection method has poor selectivity and is easily interfered by cross interference; the semiconductor sensing method has poor long-term stability due to the aging of the sensor; and the gas tube detection method is easily disturbed by changes in operating conditions, so that it cannot meet the demand of rapid and accurate detection of respiratory gas concentration in the clinic.

[0003] The light feedback cavity enhancement absorption spectrum technology based on Beer-Lambert law measures gas concentration information by directly measuring the intensity change of the output light intensity of the resonant cavity, and has the advantages of fast response, good long-term stability and high selectivity. In the past gas measurement method based on the light feedback cavity enhancement principle, the commonly used resonant cavity shape is a V-shaped cavity; however, the linear resonant cavity has a simpler structure, lower loss in theory and higher detection accuracy. However, in the past linear cavity light feedback enhancement method, the first reflected light at the incident end of the linear resonant cavity returns to the laser, which affects the normal operation of the laser and does not produce the light feedback effect, so as to affect the accuracy of the measurement system. How to avoid the influence of the first reflected light on the output mode of the laser in the process of measuring the gas concentration, optimize the overall structure of the optical path and improve the accuracy of the measurement system is a problem to be solved for realizing more accurate and efficient gas concentration measurement. SUMMARY

[0004] In view of the defects in the prior art, the present application provides a linear cavity gas concentration measurement device and method based on light feedback cavity enhancement.

[0005] To achieve the above technical purpose, the specific technical scheme adopted by the present application is as follows:

[0006] On the one hand, the present application provides a linear cavity gas concentration measurement device based on light feedback cavity enhancement, which comprises a DFB laser, a first photodetector, a second photodetector, a fiber collimator, a polarization beam splitter, a first 1 / 4 wave plate, a second 1 / 4 wave plate, a linear resonant cavity, a piezoelectric ceramic, a catadioptric mirror, a first total reflection plane mirror, a second total reflection plane mirror, an optical isolator and a gas filling assembly.

[0007] The laser output by the DFB laser is converted into a spatial Gaussian light beam by a fiber collimator and then is incident on a polarization beam splitter, the polarization beam splitter separates the incident light beam according to the polarization state, the s-polarization state light is isolated by a light isolator after passing through a second full reflection plane mirror and a second 1 / 4 wave plate, the p-polarization state light is incident on a linear resonant cavity as detection light after passing through a first 1 / 4 wave plate, the light beam output by the linear resonant cavity is divided into two light beams by a transmissive-reflection mirror, one light beam is incident on a second photodetector as an optical intensity signal, the optical intensity signal is converted into an electrical signal by the second photodetector and then is output; the other light beam passes through a first full reflection plane mirror, a light isolator, a second 1 / 4 wave plate, and a second full reflection plane mirror in sequence and then is incident on the polarization beam splitter, the light beam output by the polarization beam splitter is incident on the DFB laser through a fiber collimator to realize optical feedback frequency stabilization;

[0008] The output end of the DFB laser is also connected with a first photodetector, which is used for observing the output power of the DFB laser in real time.

[0009] A piezoelectric ceramic is arranged on the cavity mirror of the linear resonant cavity, which is used for adjusting the cavity length of the linear resonant cavity.

[0010] One end of the linear resonant cavity is provided with an air inlet, and the other end is provided with an air outlet, and the gas filling assembly is connected with the linear resonant cavity through the air inlet and the air outlet.

[0011] Further, the gas filling assembly comprises a flow meter, a gas filter, a sampling bag, and a gas suction pump.

[0012] One end of the flow meter is connected with the air inlet of the linear resonant cavity, and the other end of the flow meter is connected with the gas filter and the sampling bag in sequence; the gas suction pump is connected with the air outlet of the linear resonant cavity; the gas with the to-be-measured concentration in the sampling bag is continuously filled into the linear resonant cavity through the gas filter and the flow meter under the action of the gas suction pump.

[0013] Further, a laser controller is further included, the laser controller is connected with the DFB laser, and is used for controlling the output wavelength of the DFB laser.

[0014] Further, the to-be-measured gas comprises carbon monoxide.

[0015] Further, the first 1 / 4 wave plate is used for isolating the transmitted light and the once-reflected light of the front end mirror of the linear resonant cavity; and the second 1 / 4 wave plate is used for changing the received laser into s-polarization state light, so as to ensure that the s-polarization state light can be fed back into the DFB laser through the polarization beam splitter.

[0016] On the other hand, the application further provides a linear cavity gas concentration measurement method based on light feedback cavity enhancement applied to the measurement device, comprising the following steps:

[0017] S1, building an optical path according to a linear cavity gas concentration measurement device based on light feedback cavity enhancement;

[0018] S2, adjusting the optical path setting to make the DFB butterfly laser output laser effectively coupled into the linear resonant cavity, and form a resonant phenomenon in the linear resonant cavity; at the same time, ensure that the light beam output by the linear resonant cavity is fed back to the DFB laser, and realize the light feedback effect;

[0019] S3, filling nitrogen into the linear resonant cavity, and at the same time, tuning the output voltage of the DFB laser and the piezoelectric ceramic on the linear resonant cavity mirror, collecting the light intensity signals without gas absorption through the first and second photodetectors, and after the collection is completed, the linear resonant cavity is evacuated;

[0020] S4, filling a certain concentration of the gas to be measured into the linear resonant cavity, and at the same time, tuning the output voltage of the DFB laser and the piezoelectric ceramic on the linear resonant cavity mirror, collecting the light intensity signals with gas absorption through the first and second photodetectors;

[0021] S5, calculating the absorption coefficient of the gas to be measured according to the light intensity signals collected in S3 and S4, and obtaining the absorption curve of the gas to be measured;

[0022] S6, curve fitting the absorption curve of the gas to be measured to calculate the concentration of the gas to be measured.

[0023] Further, the S2 further comprises the following steps:

[0024] S21, adjusting the optical fiber collimator to make the DFB laser output laser effectively coupled into the linear resonant cavity; and then adjusting the piezoelectric ceramic on the linear resonant cavity mirror to make the cavity length of the linear resonant cavity match the output laser frequency of the DFB laser, so that a resonant peak appears in the linear resonant cavity;

[0025] S22, adjusting the first and second full reflection plane mirrors until the second photodetector detects that the resonant peak appears to be widened, indicating that the light feedback effect is realized; continue to adjust the first and second full reflection plane mirrors until the second photodetector detects that the resonant peak appears to be the maximum, keep the resonant peak at the maximum, and make the light feedback effect reach the best effect.

[0026] Further, in S5, the calculation of the absorption coefficient of the gas to be measured based on the light intensity signals collected in S3 and S4 comprises the following steps:

[0027] S51, based on the light intensity signal collected by the first photodetector in S3 and S4, normalizing the light intensity signal collected by the corresponding second photodetector in S3 and S4 to obtain the normalized light intensity signal when there is no gas to be measured in the linear resonant cavity And the normalized light intensity signal when the linear resonant cavity has the gas to be measured ;

[0028] S52, calculate the absorption coefficient a of the gas to be measured according to the following formula

[0029]

[0030] Wherein, The speed of light is, The decay time of the linear resonant cavity is, The normalized light intensity signal when the linear resonant cavity has no gas to be measured, The normalized light intensity signal when the linear resonant cavity has the gas to be measured.

[0031] Further, in S6, the concentration of the gas to be measured is calculated according to the following formula

[0032]

[0033] Wherein, The molecular number density of the gas to be measured is, The absorption line intensity under the selected absorption line of the gas to be measured is, The gas normalized absorption line line function.

[0034] Further, the The integral value of the absorption coefficient a can be obtained by the fitting area of the Voigt curve.

[0035] Compared with the prior art, the present application has the beneficial technical effects as follows:

[0036] The linear cavity gas concentration measuring device based on light feedback cavity enhancement provided by the present application utilizes the beam splitting processing of the light beam output by the linear resonant cavity through the transmissive-reflection mirror, separates the light output by the DFB laser according to the polarization state through the polarization beam splitter, utilizes the transmissive-reflection mirror to feed back the part of the output light of the linear resonant cavity into the DFB laser through the feedback light path, realizes the light feedback effect, enhances the output power of the DFB laser, narrows the output line width of the DFB laser, and improves the detection precision of the device. By arranging the 1 / 4 wave plate between the polarization beam splitter and the linear resonant cavity, the transmission light and the first reflection light of the front end mirror of the linear resonant cavity are isolated, so that they no longer return to the DFB laser, and the influence of this part of light on the output mode of the laser is avoided.

[0037] Through the above setting, the influence of the first reflection light of the linear resonant cavity on the operation of the DFB laser is completely eliminated, the coupling efficiency between the laser and the linear resonant cavity is further improved, and the measurement precision of the gas concentration is improved. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from the structures shown in the drawings without creative labor.

[0039] Figure 1 The structure schematic diagram of the linear cavity gas concentration measuring device based on optical feedback cavity enhancement provided by an embodiment is shown in the figure.

[0040] Figure 2 The structure schematic diagram of the linear resonant cavity and gas filling assembly provided by an embodiment is shown in the figure.

[0041] Figure 3 The Voigt line type of the gas absorption coefficient when measuring the gas concentration provided by an embodiment is shown in the figure.

[0042] Figure 4 The light intensity signal diagram of the resonant phenomenon in the linear resonant cavity provided by an embodiment is shown in the figure.

[0043] Figure 5 The light intensity signal diagram when the optical feedback effect is optimal provided by an embodiment is shown in the figure.

[0044] The figure caption is shown in the figure.

[0045] 1, DFB laser; 2, first photodetector; 3, optical fiber collimator; 4, polarization beam splitter; 5, first 1 / 4 wave plate; 6, linear resonant cavity; 7, second photodetector; 8, computer; 9, first total reflection plane mirror; 10, optical isolator; 11, second 1 / 4 wave plate; 12, second total reflection plane mirror; 13, transmissive mirror; 14, piezoelectric ceramic; 15, sampling bag; 16, gas filter; 17, flow meter; 18, air pump. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0047] Reference Figure 1In one embodiment, a linear cavity gas concentration measuring device based on optical feedback cavity enhancement is provided, comprising a DFB laser 1, a first photodetector 2, a second photodetector 7, a fiber collimator 3, a polarization beam splitter 4, a first 1 / 4 wave plate 5, a second 1 / 4 wave plate 11, a linear resonant cavity 6, a piezoelectric ceramic 14, a transmissive-refractive mirror 13, a first total reflection plane mirror 9, a second total reflection plane mirror 12, an optical isolator 10, a computer 8, and a gas filling assembly.

[0048] The laser output by the DFB laser 1 is converted into a spatial Gaussian light beam by the fiber collimator 3 and then enters the polarization beam splitter 4. The polarization beam splitter 4 separates the incident light beam according to the polarization state. The s-polarization state light is isolated by the optical isolator 10 after passing through the second total reflection plane mirror 12 and the second 1 / 4 wave plate 11. The p-polarization state light is detected as a light intensity signal and enters the linear resonant cavity 6 after passing through the first 1 / 4 wave plate 5. The light beam output by the linear resonant cavity 6 is divided into two paths by the transmissive-refractive mirror 13. One light beam is used as a light intensity signal and enters the second photodetector 7. The light intensity signal is converted into an electrical signal by the second photodetector 7 and output to the computer 8. The other light beam passes through the first total reflection plane mirror 9, the optical isolator 10, the second 1 / 4 wave plate 11, and the second total reflection plane mirror 12 in sequence and then enters the polarization beam splitter 4. The light beam output by the polarization beam splitter 4 enters the DFB laser 1 through the fiber collimator 3 to realize optical feedback frequency stabilization.

[0049] The output end of the DFB laser 1 is also connected with the first photodetector 2, which is used to observe the output power of the DFB laser 1 in real time. The output power of the DFB laser is used for subsequent data normalization processing. The other end of the DFB laser 1 is connected with the computer 8.

[0050] The piezoelectric ceramic 14 is arranged on the cavity mirror of the linear resonant cavity 6. The piezoelectric ceramic 14 is connected with the computer 8 and is used to adjust the cavity length of the linear resonant cavity 6.

[0051] One end of the linear resonant cavity 6 is provided with an air inlet, and the other end is provided with an air outlet. The gas filling assembly is connected with the linear resonant cavity 6 through the air inlet and the air outlet.

[0052] Referring to Figure 2 The gas filling assembly comprises a flow meter 17, a gas filter 16, a sampling bag 15, and a gas suction pump 18.

[0053] One end of the flow meter 17 is connected with the air inlet of the linear resonant cavity 6. The other end of the flow meter 17 is connected with the gas filter 16 and the sampling bag 15 in sequence. The gas suction pump 18 is connected with the air outlet of the linear resonant cavity 6. The gas with the concentration to be measured in the sampling bag 15 is subjected to the action of the gas suction pump 18 and then continuously fills into the linear resonant cavity 6 through the gas filter 16 and the flow meter 17.

[0054] The sampling bag 15 is used to collect the gas of the concentration to be measured for detection; the gas filter 16 is used to filter the small particle pollutants in the gas, preventing the small particle pollutants from entering the straight-line resonant cavity 6 to cause cavity damage and lead to inaccurate measurement data; the flow meter 17 is used to monitor the gas flow rate to avoid excessive gas flow rate causing damage to the straight-line resonant cavity 6; and the air pump 18 is used to provide power to make the gas of the concentration to be measured in the sampling bag 15 continuously pass through the straight-line resonant cavity 6.

[0055] The first 1 / 4 wave plate 5 is used to isolate the transmitted light and the once-reflected light of the front mirror of the straight-line resonant cavity 6; and the second 1 / 4 wave plate 11 is used to change the received laser into s-polarized light to ensure that the s-polarized light can be fed back into the DFB laser 1 through the polarization beam splitter 4.

[0056] The computer 8 is used to collect the electrical signal information for data processing and output a driving signal to control the DFB laser 1 and the piezoelectric ceramic 14; and the optical isolator 10 is used to avoid the influence of the s-polarized light in the incident light on the output signal.

[0057] In an embodiment, the straight-line cavity gas concentration measurement device based on light feedback cavity enhancement further comprises a laser controller, one end of the laser controller is connected with the DFB laser 1, and the other end of the laser controller is connected with the computer 8, and the laser controller is used to control the output wavelength of the DFB laser 1.

[0058] In an embodiment, a straight-line cavity gas concentration measurement method based on light feedback cavity enhancement is provided, which is applied to the above device and comprises the following steps:

[0059] S1, an optical path is built according to the straight-line cavity gas concentration measurement device based on light feedback cavity enhancement;

[0060] S2, the optical path is adjusted to make the DFB butterfly laser output laser effectively coupled into the straight-line resonant cavity and form a resonant phenomenon in the straight-line resonant cavity; and at the same time, the light beam output from the straight-line resonant cavity is fed back to the DFB laser to realize the light feedback effect;

[0061] S3, nitrogen is filled into the straight-line resonant cavity, and the output voltage of the DFB laser and the piezoelectric ceramic on the straight-line resonant cavity mirror are tuned, the output voltage of the DFB laser is tuned from 40 mA to 120 mA, the output wavelength of the DFB laser is continuously tuned, and the piezoelectric ceramic on the straight-line resonant cavity mirror is continuously applied with a triangular wave signal, and the light intensity signals without gas absorption are collected through the first photodetector and the second photodetector;

[0062] S4, fill a certain concentration of the gas to be measured into the linear resonant cavity, while tuning the output voltage of the DFB laser and the piezoelectric ceramic on the linear resonant cavity mirror, the output voltage of the DFB laser is tuned from 40mA to 120mA, the output wavelength of the DFB laser is continuously tuned, and the piezoelectric ceramic on the linear resonant cavity mirror is continuously applied with a triangular wave signal, and the light intensity signals with gas absorption are collected by the first and second photodetectors;

[0063] S5, according to the light intensity signals collected in S3 and S4, the absorption coefficient of the gas to be measured is calculated, and the absorption curve of the gas to be measured is obtained;

[0064] S6, curve fitting is performed on the absorption curve of the gas to be measured, and the concentration of the gas to be measured is calculated.

[0065] The light intensity signals detected by the photodetector are converted into electrical signals and output to the computer, and the data is processed by the computer to generate a light intensity signal graph, and the appearance of the resonance peak and whether the resonance peak is at the maximum value are judged by the light intensity signal graph.

[0066] The S2 further comprises the following steps:

[0067] S21, adjust the optical fiber collimator to make the DFB laser output laser effectively coupled into the linear resonant cavity; then adjust the piezoelectric ceramic on the linear resonant cavity mirror, apply a triangular wave signal with a frequency of 10Hz, an amplitude of 100V and a bias voltage of 50V to the piezoelectric ceramic, match the cavity length of the linear resonant cavity with the output laser frequency of the DFB laser, so that the resonance peak appears in the linear resonant cavity, as shown in Figure 4 ;

[0068] S22, adjust the first and second full reflection plane mirrors until the second photodetector detects that the resonance peak appears to be widened, indicating that the optical feedback effect is achieved; continue to adjust the first and second full reflection plane mirrors until the second photodetector detects that the resonance peak appears to be at the maximum value, keep the resonance peak at the maximum value, and make the optical feedback effect reach the best effect, as shown in Figure 5 .

[0069] In S5, the light intensity signals collected in S3 and S4 to calculate the absorption coefficient of the gas to be measured comprise the following steps:

[0070] S51, based on the light intensity signals collected by the first photodetector in S3 and S4, the light intensity signals collected by the corresponding second photodetector in S3 and S4 are normalized to obtain the normalized light intensity signals without the gas to be measured in the linear resonant cavity and the normalized light intensity signals with the gas to be measured in the linear resonant cavity .

[0071] S52, calculate the absorption coefficient of the gas to be measured according to the following formula

[0072]

[0073] wherein, is the speed of light, is the ring-down time of the linear resonant cavity, is the normalized light intensity signal when there is no gas to be measured in the linear resonant cavity, is the normalized light intensity signal when there is gas to be measured in the linear resonant cavity.

[0074] In S6, the concentration of the gas to be measured is calculated according to the following formula

[0075]

[0076] wherein, is the number density of the gas to be measured, is the absorption line intensity under the selected absorption line of the gas to be measured, is the absorption line line shape function of the gas to be measured.

[0077] The The integral value of the absorption coefficient a can be obtained by the fitting area of the Voigt curve.

[0078] In an embodiment, the central wavelength of the laser output by the DFB laser is 1564 nm, the gas to be measured is CO, and the standard concentration of the CO to be measured is 1000 ppm. The light feedback cavity enhanced linear cavity gas concentration measurement device based on the above is used to measure the CO, and the result is shown in Figure 3 .

[0079] The curve obtained from Figure 3 is fitted by the Voigt curve, and the concentration of 1022 ppm is calculated, which is different from the labeled concentration by 22 ppm. The minimum detectable absorption coefficient is 1.06*10 -9 cm -1 , and the minimum detectable limit is 0.53 ppm.

[0080] The remaining matters of the present application are the known art.

[0081] The technical features of the above embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0082] The above embodiments only express several implementation ways of the present application, and the description is more specific and detailed, but it should not be understood as a limitation to the scope of the application. It should be pointed out that for ordinary skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

[0083] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A linear cavity gas concentration measuring device based on optical feedback cavity enhancement, characterized in that, The device comprises a DFB laser, a first photodetector, a second photodetector, a fiber collimator, a polarization beam splitter, a first 1 / 4 wave plate, a second 1 / 4 wave plate, a linear resonant cavity, a piezoelectric ceramic, a transmissive-refractive mirror, a first full-reflection plane mirror, a second full-reflection plane mirror, an optical isolator, and a gas filling assembly. The laser output by the DFB laser is converted into a spatial Gaussian light beam by the fiber collimator and then enters the polarization beam splitter, which separates the incident light beam according to the polarization state. The s-polarized light is isolated by the optical isolator after passing through the second full-reflection plane mirror and the second 1 / 4 wave plate. The p-polarized light, as the detection light, enters the linear resonant cavity after passing through the first 1 / 4 wave plate. The light beam output by the linear resonant cavity is divided into two paths by the transmissive-refractive mirror. One path of the light beam, as the light intensity signal, enters the second photodetector, which converts the light intensity signal into an electrical signal and outputs the electrical signal. The other path of the light beam enters the polarization beam splitter after passing through the first full-reflection plane mirror, the optical isolator, the second 1 / 4 wave plate, and the second full-reflection plane mirror. The light beam output by the polarization beam splitter enters the DFB laser through the fiber collimator to realize the light feedback frequency stabilization. The output end of the DFB laser is also connected with the first photodetector, which is used for monitoring the output power of the DFB laser in real time. The piezoelectric ceramic is arranged on the cavity mirror of the linear resonant cavity, which is used for adjusting the cavity length of the linear resonant cavity. One end of the linear resonant cavity is provided with an air inlet, and the other end is provided with an air outlet. The gas filling assembly is connected with the linear resonant cavity through the air inlet and the air outlet. The gas filling assembly comprises a flow meter, a gas filter, a sampling bag, and a gas suction pump. One end of the flow meter is connected with the air inlet of the linear resonant cavity. The other end of the flow meter is connected with the gas filter and the sampling bag in sequence. The gas suction pump is connected with the air outlet of the linear resonant cavity. The to-be-detected gas in the sampling bag is continuously filled into the linear resonant cavity through the gas filter and the flow meter under the action of the gas suction pump. The first 1 / 4 wave plate is used for isolating the transmitted light and the once-reflected light of the front mirror of the linear resonant cavity. The second 1 / 4 wave plate is used for converting the received laser into s-polarized light, so as to ensure that the s-polarized light can be fed back into the DFB laser through the polarization beam splitter.

2. The linear cavity gas concentration measurement device based on optical feedback cavity enhancement of claim 1, wherein, The device further comprises a laser controller, which is connected with the DFB laser and is used for controlling the output wavelength of the DFB laser.

3. The linear cavity gas concentration measurement device based on optical feedback cavity enhancement of claim 2, wherein, The to-be-detected gas is carbon monoxide.

4. The method of linear cavity gas concentration measurement based on optical feedback cavity enhancement, applied to the device of any one of claims 1-3, characterized in that, The device comprises the following steps: S1. An optical path is built according to the linear cavity gas concentration measuring device based on the light feedback cavity enhancement. S2. The optical path is adjusted to make the DFB laser output laser effectively coupled into the linear resonant cavity and form a resonance phenomenon in the linear resonant cavity. At the same time, the light beam output by the linear resonant cavity is fed back into the DFB laser to realize the light feedback effect. S3. Nitrogen is filled into the linear resonant cavity. At the same time, the output voltage of the DFB laser and the piezoelectric ceramic on the cavity mirror of the linear resonant cavity are tuned. The light intensity signal without gas absorption is collected by the first photodetector and the second photodetector. After the collection is completed, the linear resonant cavity is evacuated. S4, filling a certain concentration of the gas to be measured into the linear resonant cavity, while tuning the output voltage of the DFB laser and the piezoelectric ceramic on the linear resonant cavity mirror, collecting the light intensity signal under the condition of gas absorption through the first photodetector and the second photodetector; S5, calculating the absorption coefficient of the gas to be measured according to the light intensity signal collected in S3 and S4, and obtaining the absorption curve of the gas to be measured; S51, based on the first photodetector in S3, S4 collected light intensity signal, the corresponding second photodetector in S3, S4 collected light intensity signal is normalized to obtain the normalized light intensity signal without the gas to be measured in the straight line resonant cavity And the normalized light intensity signal when there is a gas to be measured in the straight line resonant cavity ; S52, calculating the absorption coefficient of the gas to be measured according to the following formula: wherein, c is the speed of light, is the ring-down time of the linear resonator, is the normalized light intensity signal without the gas to be measured in the linear resonator, is the normalized light intensity signal with the gas to be measured in the linear resonator; S6, curve fitting the absorption curve of the gas to be measured, and calculating the concentration of the gas to be measured; The concentration of the gas to be measured is calculated according to the following formula : wherein, is the number density of the gas to be measured, is the absorption line intensity under the selected absorption line of the gas to be measured, is the normalized absorption line shape function of the gas.

5. The optical feedback cavity enhanced linear cavity gas concentration measurement method according to claim 4, wherein, The S2 further includes the following steps: S21, adjusting the optical fiber collimator to make the DFB laser output laser effectively coupled into the linear resonant cavity; then adjusting the piezoelectric ceramic on the linear resonant cavity mirror to make the cavity length of the linear resonant cavity match the output laser frequency of the DFB laser, so that the resonance peak appears in the linear resonant cavity; S22, adjusting the first and second total reflection plane mirrors until the second photodetector detects that the resonance peak appears to be widened, indicating that the optical feedback effect is achieved; continue to adjust the first and second total reflection plane mirrors until the second photodetector detects that the resonance peak appears to be the maximum, keep the resonance peak at the maximum, and make the optical feedback effect reach the best effect.

6. The optical feedback cavity enhanced linear cavity gas concentration measurement method according to claim 4, wherein, The The area under the Voigt curve can be obtained by fitting, is the integral value of the absorption coefficient α.

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