Gas pressure measurement device and method based on femtosecond double optical combs

Abstract

The invention discloses a gas pressure measurement device and method based on femtosecond double optical combs, and belongs to the field of laser measurement. The gas pressure measuring device comprises a light source module, a measuring module, a detection module and a data processing module. The light source module comprises a first optical frequency comb and a second optical frequency comb. The first 1 * 2 optical fiber beam splitter divides laser energy into 70%-90% and 10%-30%, and 70%-90% of the laser energy is transmitted to the beam expander. The femtosecond double-optical-comb spectrum system has the advantages of broadband spectrum, extremely high spectral resolution, rapid laser spectrum and the like, the broadband spectrum of the double-optical-comb spectrum simultaneously collects a plurality of absorption spectral lines of the same gas, and the measurement precision of gas partial pressure is improved; the broadband spectrum simultaneously collects absorption spectral lines of various gases, simultaneous measurement of pressures of various gas components is realized, and the total pressure of the gases is obtained through summation measurement of partial pressures of mixed gases. The gas partial pressure measurement speed is improved through higher spectral resolution and higher double-optical-comb spectral sampling rate, and the requirement for online dynamic measurement is met.

Description

Technical Field

[0001] The invention relates to a device and a method for measuring gas pressure based on a femtosecond double optical comb, belonging to the technical field of laser measurement. Background Art

[0002] Pressure measurement has a wide range of application needs in aerospace, biomedicine, nuclear energy and other fields. Gas pressure measurement is an important part of it, and accurate gas pressure measurement technology is an indispensable technical means. At present, the main method of gas pressure measurement is to rely on traditional pressure sensors for detection. Although the measurement accuracy is high and the cost is low, there are problems such as wear caused by repetitive and long-term work, decreased measurement accuracy, and abnormal calibration. Mass spectrometers, represented by quadrupole mass spectrometers, are also widely used for gas partial pressure measurement. However, this technology has certain disadvantages: 1. Changes in the ionization probability of different gases lead to inconsistent output gain, making calibration very complicated and difficult; 2. The measured value of gas partial pressure often depends on the partial pressure and total pressure of other gases, so it is almost impossible to independently calibrate the gas mixture and total pressure; 3. This technology cannot be used in low vacuum (10 -2 The non-invasive measurement of optics, especially laser, provides a very good technical solution to solve the above problems. Exploring how to apply laser technology to the field of pressure measurement and calibration is an important research direction at present.

[0003] Optical non-contact pressure measurement methods can be roughly divided into laser interferometry and laser spectroscopy. Laser interferometry mainly uses the changes in physical properties such as gas density and refractive index caused by changes in gas pressure to correlate with changes in optical path length, and uses a laser interferometer to measure changes in optical path length to achieve gas pressure measurement. Laser interferometry is mainly aimed at the measurement of non-polar gas molecules. Laser spectroscopy mainly uses gas absorption spectroscopy for pressure measurement. Interferometry and spectroscopy have different technical principles, and the two are complementary in application. Among spectroscopy methods, adjustable diode laser absorption spectroscopy (TDLAS) is widely used in gas concentration measurement, which can realize the identification and concentration measurement of gas molecules in mixed gases. At the same time, the absorption spectrum of the gas also contains the pressure information of the gas molecules, so TDLAS technology can also realize the measurement of gas pressure. Although TDLAS avoids most of the problems of mass spectrometer pressure measurement, the bandwidth of the spectrum generated by the diode laser is limited, so TDLAS technology can generally only measure a single gas component. Therefore, the multi-gas measurement capability and measurement accuracy of TDLAS technology are affected. In addition, the slow speed of obtaining spectral information by scanning also affects its measurement speed, so its measurement speed is also significantly reduced, which cannot meet the needs of online dynamic measurement. In essence, these shortcomings of TDLAS are mainly due to its extremely narrow spectral band and slow electronic tuning spectrum acquisition method. In summary, the current gas pressure measurement technology has more or less technical deficiencies and defects. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for measuring gas pressure based on a femtosecond double-comb, which utilizes the advantages of a femtosecond double-comb spectroscopy system such as broadband spectrum, extremely high spectral resolution and fast laser spectrum, and simultaneously collects multiple absorption lines of the same gas to improve the measurement accuracy of gas partial pressure; the broadband spectrum simultaneously collects the absorption lines of multiple gases to achieve simultaneous measurement of the pressures of multiple gas components, and the total gas pressure is obtained by summing the partial pressures of the mixed gases, thereby achieving simultaneous online dynamic measurement of the pressures of multiple gas components.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The present invention discloses a gas pressure measurement device based on a femtosecond dual optical comb, comprising a light source module, a measurement module, a detection module and a data processing module. The light source module comprises a first optical frequency comb and a second optical frequency comb, and the light source module outputs two near-infrared broadband optical frequency combs for measurement, and the light source module uses an optical fiber to output the two lasers to the measurement module. The measurement module adjusts and couples the lasers to form a measurement path and a reference path of the measurement optical path. After the measurement module receives two laser beams from the light source module, the laser beam of the first optical frequency comb is connected to the first power amplifier using an optical fiber to amplify the laser energy, and the laser beam of the second optical frequency comb is connected to the second power amplifier using an optical fiber to amplify the laser energy; the first power amplifier is connected to the first wavelength division multiplexer using an optical fiber to filter the laser beam and reduce the spectral line width to improve the measurement resolution, sampling rate and measurement speed. Similarly, the second power amplifier is connected to the second wavelength division multiplexer using an optical fiber to reduce the spectral line width; the first wavelength division multiplexer is connected to the first 1×2 optical fiber beam splitter using an optical fiber to divide the laser beam into two beams, beam 1 and beam 2. Similarly, the second wavelength division multiplexer is connected to the second 1×2 optical fiber beam splitter using an optical fiber to divide the laser beam into two beams, beam 3 and beam 4. Finally, the beat frequency of beam 1 and beam 4 forms a measurement path signal, and the beat frequency of beam 2 and beam 3 forms a reference path signal. The split beam 1 of the first 1×2 fiber beam splitter is connected to a beam expander using an optical fiber. The beam expander outputs a spatial laser as a measurement optical path, expands the laser beam to increase the contact volume between the laser and the gas, inputs the spatial laser into a collimator, couples the laser into an optical fiber, and inputs the laser into a second 2×2 fiber coupler using an optical fiber; the split beam 2 of the first 1×2 fiber beam splitter is input into the first 2×2 fiber coupler using an optical fiber. The beam 3 of the second 1×2 fiber beam splitter is input into the first 2×2 fiber coupler using an optical fiber, and the beam 4 of the second 1×2 fiber beam splitter is input into the second 2×2 fiber coupler using an optical fiber. The first 2×2 fiber coupler and the second 2×2 fiber coupler couple the two input laser beams and then output them into the detection module using an optical fiber. The detection module includes a first balanced detector and a second balanced detector, which convert the input beat frequency signal into an electrical signal output for easy signal acquisition. The first 2×2 optical fiber coupler is connected to the first balanced detector to output a reference path signal, and the second 2×2 optical fiber coupler is connected to the second balanced detector to output a measurement path signal, and is connected to the data processing module using a data transmission line. The data processing module includes a data processing host computer of a data acquisition card to solve and process the collected signals to obtain the gas pressure value.

[0007] In order to increase the laser energy of the measurement path, to improve the signal-to-noise ratio of the measurement signal of the measurement path, and to optimize the utilization of laser energy, preferably, the first 1×2 fiber optic beam splitter divides the laser energy into 70% to 90% and 10% to 30%, and 70% to 90% of the laser energy is transmitted to the beam expander.

[0008] In order to maximize the laser energy of the measurement path and maximize the signal-to-noise ratio of the measurement signal of the measurement path, as a further preferred embodiment, the first 1×2 fiber optic beam splitter divides the laser energy into 90% and 10%, and 90% of the laser energy is transmitted to the beam expander.

[0009] The present invention discloses a gas pressure measurement method based on a femtosecond double optical comb, which is implemented based on a gas pressure measurement device based on a femtosecond double optical comb. A gas pressure measurement method based on a femtosecond double optical comb comprises the following steps:

[0010] Step 1: Build a gas pressure measurement device according to the gas pressure measurement device based on femtosecond dual optical comb. The near-infrared laser emitted by the first optical frequency comb is increased in measurement energy by the first power amplifier. The laser passes through the first wavelength division multiplexer and the first 1×2 optical fiber beam splitter to split the laser energy into beam 1 and beam 2. Beam 2 is transmitted to the first 2×2 optical fiber coupler. The laser energy of beam 1 is transmitted to the beam expander as the measurement path signal. The measurement path laser passes through the high-pressure gas chamber and is absorbed by the gas molecules to obtain the gas absorption signal, which is then received by the collimator and transmitted to the second 2×2 optical fiber coupler. The first wavelength division multiplexer and the second wavelength division multiplexer are the same. The first wavelength division multiplexer and the second wavelength division multiplexer reduce the spectral line width to improve the measurement resolution, sampling rate and measurement speed. The second optical frequency comb emits near-infrared laser, and its repetition frequency is not much different from that of the first optical frequency comb. The second power amplifier increases the measurement energy, passes through the second wavelength division multiplexer, and then passes through the second 1×2 fiber splitter to split the laser energy into beam 3 and beam 4. Beam 3 is transmitted to the first 2×2 fiber coupler, and beam 4 is transmitted to the second 2×2 fiber coupler. The first 2×2 fiber coupler is transmitted to the first balanced detector, and the time domain interference pattern after the beat frequency is collected as the measurement path signal. The second 2×2 fiber coupler is transmitted to the second balanced detector, and the time domain interference pattern after the beat frequency is collected as the reference path signal. The measurement path signal and the reference path signal are transmitted to the data processing host computer for data processing. After Fourier transform, filtering and other data processing are performed on the interference signal, the spectral line results of the measurement path and the reference path are obtained in the frequency domain.

[0011] Step 2: Based on the measured results of the two spectral lines, the gas partial pressure value is calculated to achieve gas pressure measurement based on the femtosecond dual-comb.

[0012] Step 2.1: Spectral calibration is performed on the light intensity I0(ν) of the measurement path spectrum line and the light intensity I(ν) of the reference path spectrum line.

[0013] Step 2.2: Preprocess the spectral absorption data, filter out low-frequency and high-frequency noise, then normalize the spectral data, extract the characteristic absorption peak and calculate the integrated absorption amount A of the target gas using formula (1): absWhere, I(ν) is the light intensity of the measurement path, mW; I0(ν) is the light intensity of the reference path, mW.

[0014]

[0015] Step 2.3: Determine the absorption length L of the light beam interacting with the sample gas and determine the absorption line intensity S of the target gas, cm -1 / (molec·cm -2 ).

[0016] Step 2.4: Calculate the molecular density n of the target gas according to the formula, and then calculate the partial pressure P of the target gas according to formula (3): partial .

[0017]

[0018] P partial =nkL (3)

[0019] Where: k is the Boltzmann constant; T is the gas temperature, K.

[0020] Step 2.5: The first optical frequency comb and the second optical frequency comb have a wide near-infrared spectrum band, and obtain a broadband measurement path and reference path spectrum line. At the same time, multiple absorption peaks of the same gas are obtained. A value of partial pressure is calculated for each absorption peak, and multiple pressure values ​​are obtained in parallel. These values ​​are averaged to obtain a more accurate measurement result P. p , calculated using formula (4):

[0021]

[0022] Where N is the number of pressure values ​​calculated using the absorption peaks of the same gas.

[0023] The broadband spectral output of the dual optical comb covers the wavelength band from 1.3μm to 1.7μm, covering the absorption spectra of multiple gases (methane, carbon dioxide, etc.). The partial pressures of different gases in the mixed gas are measured in parallel, and the total pressure P of the mixed gas is obtained by summing the gas partial pressures. The calculation adopts formula (5):

[0024]

[0025] Where: P pi is the partial pressure of the i-th gas in the mixed gas.

[0026] The multiple gases include methane and carbon dioxide.

[0027] Beneficial effects:

[0028] 1. The present invention discloses a device and method for measuring gas pressure based on a femtosecond dual-comb. The device and method perform gas pressure measurement based on a near-infrared dual-comb, making full use of the advantages of the dual-comb broadband spectrum, obtaining multiple absorption peaks of the same gas molecule at the same time, and obtaining multiple measurement results in parallel. The average of multiple measurement values ​​is used to reduce the random error of pressure measurement and improve the measurement accuracy of gas pressure.

[0029] 2. The present invention discloses a device and method for measuring gas pressure based on a femtosecond dual-optical comb, which fully utilizes the advantages of the dual-optical comb broadband spectral output. The spectral width ranges from 1.3μm to 1.7μm, covering the absorption spectra of multiple gases (methane, carbon dioxide, etc.). Therefore, the present invention can accurately measure the partial pressures of different gases in the mixed gas in parallel, and the total pressure of the mixed gas is obtained by summing the partial pressures. Higher spectral resolution and faster dual-optical comb spectral sampling rate increase the speed of gas partial pressure measurement and meet the requirements of online dynamic measurement.

[0030] 3. The present invention discloses a device and method for measuring gas pressure based on a femtosecond dual-comb, which fully utilizes the advantages of the dual-comb broadband spectral output, acquires molecular broadband spectral information in real time in a system without mechanical scanning components, and improves measurement speed and efficiency.

[0031] 4. The present invention discloses a device and method for measuring gas pressure based on a femtosecond dual optical comb. The first 1×2 optical fiber beam splitter divides the laser energy into 70% to 90% and 10% to 30%. 70% to 90% of the laser energy is transmitted to the beam expander 9, which can increase the laser energy of the measurement path, thereby improving the signal-to-noise ratio of the measurement signal of the measurement path and improving the laser energy utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of a gas pressure measurement device based on a femtosecond dual optical comb. Among them, 1-first optical frequency comb, 2-second optical frequency comb, 3-first power amplifier, 4-second power amplifier, 5-first wavelength division multiplexer, 6-second wavelength division multiplexer, 7-first 1×2 fiber beam splitter, 8-second 1×2 fiber beam splitter, 9-beam expander, 10-high pressure gas chamber, 11-collimator, 12-first 2×2 fiber coupler, 13-second 2×2 fiber coupler, 14-first balanced detector, 15-second balanced detector, 16-data processing host computer. DETAILED DESCRIPTION

[0033] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0034] Embodiment 1:

[0035] like Figure 1As shown, a gas pressure measurement device based on a femtosecond dual optical comb disclosed in this embodiment includes a light source module, a measurement module, a detection module and a data processing module. The light source module includes a first optical frequency comb 1 and a second optical frequency comb 2. The light source module outputs two near-infrared broadband optical frequency combs for measurement. The light source module uses optical fiber to output the two lasers to the measurement module. The measurement module adjusts and couples the lasers to form a measurement path and a reference path of the measurement optical path. After the measurement module receives the two laser beams from the light source module, the laser beam of the first optical frequency comb 1 is connected to the first power amplifier 3 using an optical fiber to amplify the laser energy, and the laser beam of the second optical frequency comb 2 is connected to the second power amplifier 4 using an optical fiber to amplify the laser energy; the first power amplifier 3 is connected to the first wavelength division multiplexer 5 using an optical fiber to filter the laser and reduce the spectral line width to improve the measurement resolution, sampling rate and measurement speed. Similarly, the second power amplifier 4 is connected to the second wavelength division multiplexer 6 using an optical fiber to reduce the spectral line width; the first wavelength division multiplexer 5 is connected to the first 1×2 optical fiber beam splitter 7 using an optical fiber to divide the laser beam into two beams, beam 1 and beam 2. Similarly, the second wavelength division multiplexer 6 and the second 1×2 optical fiber beam splitter 8 are connected using an optical fiber to divide the laser beam into two beams, beam 3 and beam 4. Finally, the beat frequency of beam 1 and beam 4 forms a measurement path signal, and the beat frequency of beam 2 and beam 3 forms a reference path signal, wherein the laser energy divided by beam 1 is 90%, the laser energy divided by beam 2 is 10%, the laser energy divided by beam 3 is 50%, and the laser energy divided by beam 4 is 50%. Figure 1 As shown. The split beam 1 of the first 1×2 fiber beam splitter 7 is connected to the beam expander 9 by using an optical fiber. The beam expander 9 outputs a spatial laser as a measuring optical path, expands the laser beam to increase the contact volume between the laser and the gas, and inputs the spatial laser into the collimator 11, couples the laser into the optical fiber, and inputs the laser into the second 2×2 fiber coupler 13 by using an optical fiber; the split beam 2 of the first 1×2 fiber beam splitter 7 is input into the first 2×2 fiber coupler 12 by using an optical fiber. The beam 3 of the second 1×2 fiber beam splitter 8 is input into the first 2×2 fiber coupler 12 by using an optical fiber, and the beam 4 of the second 1×2 fiber beam splitter 8 is input into the second 2×2 fiber coupler 13 by using an optical fiber. The first 2×2 fiber coupler 12 and the second 2×2 fiber coupler 13 couple the two input laser beams and output them into the detection module by using an optical fiber. The detection module includes a first balanced detector 14 and a second balanced detector 15, which convert the input beat frequency signal into an electrical signal output for signal collection. The first 2×2 optical fiber coupler 12 is connected to the first balanced detector 14 to output a reference path signal, and the second 2×2 optical fiber coupler 13 is connected to the second balanced detector 15 to output a measurement path signal, and is connected to the data processing module using a data transmission line. The data processing module includes a data processing host computer 16 of a data acquisition card to solve and process the collected signal to obtain the gas pressure value.

[0036] The present embodiment discloses a gas pressure measurement method based on a femtosecond dual-optical comb, which is implemented based on a gas pressure measurement device based on a femtosecond dual-optical comb. A gas pressure measurement method based on a femtosecond dual-optical comb comprises the following steps:

[0037] Step 1: Build a gas pressure measuring device according to the gas pressure measuring device based on femtosecond dual optical comb. The near-infrared laser emitted by the first optical frequency comb 1 is increased in measurement energy by the first power amplifier 3. The laser passes through the first wavelength division multiplexer 5 and the first 1×2 optical fiber beam splitter 7 to split the laser energy into beam 1 and beam 2. The beam 2 is transmitted to the first 2×2 optical fiber coupler 12. The laser energy of beam 1 is transmitted to the beam expander 9 as a measurement path signal. The measurement path laser passes through the high-pressure gas chamber 10 and is absorbed by the gas molecules to obtain a gas absorption signal, which is then received by the collimator 11 and transmitted to the second 2×2 optical fiber coupler 13. The first wavelength division multiplexer 5 and the second wavelength division multiplexer 6 are the same. The first wavelength division multiplexer 5 and the second wavelength division multiplexer 6 reduce the spectral line width to improve the measurement resolution, sampling rate and measurement speed. The second optical frequency comb 2 emits near-infrared laser light, and its repetition frequency is not much different from that of the first optical frequency comb 1. The second power amplifier 4 increases the measurement energy, passes through the second wavelength division multiplexer 6, and then passes through the second 1×2 fiber splitter 8 to split the laser energy into beam 3 and beam 4. The beam 3 is transmitted to the first 2×2 fiber coupler 12, and the beam 4 is transmitted to the second 2×2 fiber coupler 13. The first 2×2 fiber coupler 12 is transmitted to the first balanced detector 14, and the time domain interference pattern after the beat frequency is collected as the measurement path signal. The second 2×2 fiber coupler 13 is transmitted to the second balanced detector 15, and the time domain interference pattern after the beat frequency is collected as the reference path signal. The measurement path signal and the reference path signal are transmitted to the data processing host computer 16 for data processing. After Fourier transform, filtering and other data processing are performed on the interference signal, the spectral line results of the measurement path and the reference path are obtained in the frequency domain.

[0038] Step 2: Based on the measured results of the two spectral lines, calculate and obtain the gas partial pressure value.

[0039] Step 2.1: Spectral calibration is performed on the light intensity I0(ν) of the measurement path spectrum line and the light intensity I(ν) of the reference path spectrum line.

[0040] Step 2.2: Preprocess the spectral absorption data, filter out low-frequency and high-frequency noise, then normalize the spectral data, extract the characteristic absorption peak and calculate the integrated absorption amount A of the target gas using formula (1): abs Where, I(ν) is the light intensity of the measurement path, mW; I0(ν) is the light intensity of the reference path, mW.

[0041]

[0042] Step 2.3: Determine the absorption length L of the light beam interacting with the sample gas and determine the absorption line intensity S of the target gas, cm -1 / (molec·cm -2 ).

[0043] Step 2.4: Calculate the molecular density n of the target gas according to formula (2), and then calculate the partial pressure P of the target gas according to formula (3): partial .

[0044]

[0045] P partial =nkL (3)

[0046] Where: k is the Boltzmann constant; T is the gas temperature, K.

[0047] Step 2.5: The first optical frequency comb 1 and the second optical frequency comb 2 use a wide near-infrared spectrum to obtain a broadband measurement path and a reference path spectrum line, and simultaneously obtain multiple absorption peaks of the same gas. For each absorption peak, a value of partial pressure is calculated, and multiple pressure values ​​are obtained in parallel. These values ​​are averaged to obtain a final more accurate measurement result P. p , calculated using formula (4):

[0048]

[0049] Where N is the number of pressure values ​​calculated using the absorption peaks of the same gas.

[0050] The broadband spectral output of the dual optical comb covers the wavelength band from 1.3μm to 1.7μm, covering the absorption spectra of multiple gases (methane, carbon dioxide, etc.). The partial pressures of different gases in the mixed gas are measured in parallel, and the total pressure P of the mixed gas is obtained by summing the gas partial pressures. The calculation adopts formula (5):

[0051]

[0052] Where: P pi is the partial pressure of the i-th gas in the mixed gas.

[0053] The various gases include methane, carbon dioxide, and the like.

[0054] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A gas pressure measurement device based on a femtosecond dual-comb, characterized in that: The invention comprises a light source module, a measuring module, a detection module and a data processing module; the light source module comprises a first optical frequency comb (1) and a second optical frequency comb (2); the light source module outputs two near-infrared wide-band optical frequency combs for measurement; the light source module uses optical fiber to output the two lasers to the measuring module; the measuring module adjusts and couples the lasers to form a measuring path and a reference path of the measuring optical path; after the measuring module receives the two lasers from the light source module, the laser of the first optical frequency comb (1) is connected to a first power amplifier (3) using an optical fiber to amplify the laser energy, and the laser of the second optical frequency comb (2) is connected to a second power amplifier (4) using an optical fiber to amplify the laser energy; the first power amplifier (3) uses optical fiber and a first wavelength division multiplexing The method comprises connecting the first wavelength division multiplexer (5) to the second wavelength division multiplexer (6) to filter the laser light and reduce the spectral line width, so as to improve the measurement resolution, sampling rate and measurement speed; connecting the second power amplifier (4) to the second wavelength division multiplexer (6) by using an optical fiber to reduce the spectral line width; connecting the first wavelength division multiplexer (5) to the first 1×2 optical fiber beam splitter (7) by using an optical fiber to split the laser light into two beams, beam 1 and beam 2; similarly, connecting the second wavelength division multiplexer (6) to the second 1×2 optical fiber beam splitter (8) by using an optical fiber to split the laser light into two beams, beam 3 and beam 4; the beat frequency of beam 1 and beam 4 forms a measurement path signal, and the beat frequency of beam 2 and beam 3 forms a reference path signal; connecting the split beam 1 of the first 1×2 optical fiber beam splitter (7) to the expansion device (6) by using an optical fiber to reduce the spectral line width; connecting the first wavelength division multiplexer (5) to the first 1×2 optical fiber beam splitter (7) by using an optical fiber to split the laser light into two beams, beam 1 and beam 2; connecting the second wavelength division multiplexer (6) to the second 1×2 optical fiber beam splitter (8) by using an optical fiber to split the laser light into two beams, beam 3 and beam 4; the beat frequency of beam 1 and beam 4 forms a measurement path signal, and the beat frequency of beam 2 and beam 3 forms a reference path signal; connecting the split beam 1 of the first 1×2 optical fiber beam splitter (7) to the expansion device (6) by using an optical fiber to reduce the spectral line width; connecting the first wavelength division multiplexer (5) to the first 1×2 optical fiber beam splitter (7) to the expansion device (6) by using an optical fiber to split the laser light into two beams, beam 3 and beam 4; connecting the second wavelength division multiplexer (6) to the second 1 The beam expander (9) outputs a spatial laser as a measuring optical path, expands the laser beam to increase the contact volume between the laser and the gas, inputs the spatial laser into a collimator (11), couples the laser into an optical fiber, and inputs the optical fiber into a second 2×2 optical fiber coupler (13); the light beam 2 split by the first 1×2 optical fiber beam splitter (7) is input into a first 2×2 optical fiber coupler (12) using an optical fiber; the light beam 3 of the second 1×2 optical fiber beam splitter (8) is input into the first 2×2 optical fiber coupler (12) using an optical fiber, and the light beam 4 of the second 1×2 optical fiber beam splitter (8) is input into the second 2×2 optical fiber coupler (13) using an optical fiber; the first 2×2 optical fiber coupler (12 ) and a second 2×2 optical fiber coupler (13) couple the input two laser beams and output them to the detection module using optical fiber; the detection module comprises a first balanced detector (14) and a second balanced detector (15), which convert the input beat frequency signal into an electrical signal output to facilitate signal acquisition; the first 2×2 optical fiber coupler (12) is connected to the first balanced detector (14) to output a reference path signal; the second 2×2 optical fiber coupler (13) is connected to the second balanced detector (15) to output a measurement path signal, and is connected to the data processing module using a data transmission line; the data processing module comprises a data processing host computer (16) of a data acquisition card to perform calculation processing on the collected signal to obtain a gas pressure value.

2. A gas pressure measurement device based on a femtosecond dual-comb according to claim 1, characterized in that: The first 1×2 optical fiber beam splitter (7) divides the laser energy into 70% to 90% and 10% to 30%, and 70% to 90% of the laser energy is transmitted to the beam expander (9).

3. A gas pressure measurement device based on a femtosecond dual-comb according to claim 2, characterized in that: The first 1×2 optical fiber beam splitter (7) divides the laser energy into 90% and 10%, and 90% of the laser energy is transmitted to the beam expander (9).

4. A gas pressure measurement method based on a femtosecond dual-comb, implemented based on a gas pressure measurement device based on a femtosecond dual-comb as claimed in claim 1, 2 or 3, characterized in that: The following steps are included: Step 1: A gas pressure measuring device is constructed according to the gas pressure measuring device based on a femtosecond dual optical comb; the near-infrared laser emitted by the first optical frequency comb (1) is passed through a first power amplifier (3) to increase the measurement energy; the laser passes through a first wavelength division multiplexer (5) and a first 1×2 optical fiber beam splitter (7) to split the laser energy into a beam 1 and a beam 2; the beam 2 is transmitted to a first 2×2 optical fiber coupler (12); the laser energy of the beam 1 is transmitted to a beam expander (9) as a measurement path signal; the measurement path laser passes through a high-pressure gas chamber (10) and is absorbed by gas molecules to obtain a gas absorption signal, which is then received by a collimator (11) and transmitted to a second 2×2 optical fiber coupler (13); the first wavelength division multiplexer (5) and the second wavelength division multiplexer (6) are the same; the first wavelength division multiplexer (5) and the second wavelength division multiplexer (6) reduce the spectral line width to improve the measurement resolution, sampling rate and measurement speed; the second optical frequency comb (2) emits A near-infrared laser, whose repetition frequency is not much different from that of the first optical frequency comb (1), is passed through a second power amplifier (4) to increase the measurement energy, passed through a second wavelength division multiplexer (6), and then passed through a second 1×2 optical fiber splitter (8) to split the laser energy into a beam 3 and a beam 4, wherein the beam 3 is transmitted to a first 2×2 optical fiber coupler (12), and the beam 4 is transmitted to a second 2×2 optical fiber coupler (13); the first 2×2 optical fiber coupler (12) is transmitted to a first balanced detector (14), and a time domain interference pattern after the beat frequency is collected as a measurement path signal; the second 2×2 optical fiber coupler (13) is transmitted to a second balanced detector (15), and a time domain interference pattern after the beat frequency is collected as a reference path signal; the measurement path signal and the reference path signal are transmitted to a data processing host computer (16) for data processing, and after Fourier transform, filtering and other data processing are performed on the interference signal, the spectral line results of the measurement path and the reference path are obtained in the frequency domain; Step 2: According to the results of the two measured spectral lines, the gas partial pressure value is calculated to achieve gas pressure measurement based on the femtosecond dual-comb; Step 2.1: spectrally calibrate the light intensity I0(ν) of the measurement path spectrum line and the light intensity I(ν) of the reference path spectrum line; Step 2.2: Preprocess the spectral absorption data, filter out low-frequency and high-frequency noise, then normalize the spectral data, extract the characteristic absorption peak and calculate the integrated absorption amount A of the target gas using formula (1): abs ; Where, I(ν) is the light intensity of the measurement path, mW; I0(ν) is the light intensity of the reference path, mW; Step 2.3: Determine the absorption length L of the light beam interacting with the sample gas and determine the absorption line intensity S of the target gas, cm -1 / (molec·cm -2 ); Step 2.4: Calculate the molecular density n of the target gas according to formula (2), and then calculate the partial pressure P of the target gas according to formula (3): partial ; P partial =nkL (3) Where: k is the Boltzmann constant; T is the gas temperature, K; Step 2.5: The first optical frequency comb (1) and the second optical frequency comb (2) use a wide near-infrared spectrum to obtain a broadband measurement path and a reference path spectrum line, and simultaneously obtain multiple absorption peaks of the same gas. For each absorption peak, a partial pressure value is calculated, and multiple pressure values ​​are obtained in parallel. These values ​​are averaged to obtain a final more accurate measurement result P. p , calculated using formula (4): Where N is the number of pressure values ​​calculated using the absorption peaks of the same gas; The broadband spectral output of the dual optical comb covers the wavelength range from 1.3 μm to 1.7 μm, covering the absorption spectra of multiple gases. The partial pressures of different gases in the mixed gas are measured in parallel, and the total pressure P of the mixed gas is obtained by summing the gas partial pressures. The calculation adopts formula (5): Where: P pi is the partial pressure of the i-th gas in the mixed gas.

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