Double-optical-comb-cavity modulated gas measurement system and method based on electro-optical modulation

Abstract

The invention provides a double-optical-comb-cavity modulated gas measurement system and method based on electro-optical modulation, in the use process, a detection optical comb and a reference optical comb which are coherent are generated through a double-optical-comb output module, the detection optical comb enters a resonant cavity to interact with gas to be measured, and the reference optical comb directly reaches a data acquisition and analysis module; the data acquisition and analysis module is communicated with the resonant cavity and the double-optical-comb output module, and is used for receiving the reference optical comb and the detection optical comb output from the resonant cavity, and performing component and concentration analysis on the to-be-detected gas according to the detection optical comb and the reference optical comb; in the measuring process, the electro-optical modulation module is used for acquiring the detection optical comb output from the resonant cavity in real time, and the optical field of the detection optical comb in the resonant cavity is dynamically modulated based on the detection optical comb, so that the optical comb mode is matched with the free spectral range of the resonant cavity in real time, and efficient coupling is formed in the resonant cavity; the influence of the gas dispersion effect on the measurement precision is eliminated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas detection, and particularly relates to a dual-comb cavity modulation gas measurement system and method based on electro-optical modulation. BACKGROUND

[0002] Gas absorption spectrum measurement is a technology based on the selective absorption characteristics of a substance to light, which qualitatively or quantitatively determines the composition and concentration of a gas by analyzing the absorption degree of a specific wavelength of light by gas molecules. The cavity ring-down spectroscopy (CRDS) is a high-sensitivity spectroscopy technology based on the measurement of the ring-down time of a light cavity, which realizes quantitative determination of the concentration of a gas by detecting the light intensity attenuation time of a light comb in an optical resonant cavity due to gas absorption.

[0003] However, in actual use of the CRDS technology, the gas to be measured generally contains multiple gases, and due to the different absorption characteristics and refractive indexes of different gases, the dispersion effect of the gas occurs, which affects the propagation of the light signal, causes nonlinear modulation in the ring-down process, and causes the ring-down characteristics of the detection light comb in the optical resonant cavity to deviate, thereby affecting the measurement accuracy. SUMMARY

[0004] In order to solve the technical problem that the dispersion effect of the gas affects the propagation of the light signal, causes nonlinear modulation in the ring-down process, and affects the measurement accuracy in the background art, the application provides a dual-comb cavity modulation gas measurement system and method based on electro-optical modulation.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0006] In a first aspect, the application provides a dual-comb cavity modulation gas measurement system based on electro-optical modulation, which comprises a dual-comb output module, a resonant cavity, a data acquisition and analysis module, and an electro-optical modulation module.

[0007] The dual-comb output module is used to output coherent detection light combs and reference light combs.

[0008] The resonant cavity is in communication with the dual-comb output module, and is used to accommodate the gas to be measured and receive the detection light combs.

[0009] The data acquisition and analysis module is in communication with the resonant cavity and the dual-comb output module, and is used to receive the reference light combs and the detection light combs output from the resonant cavity.

[0010] The electro-optical modulation module is partially disposed in the resonant cavity, wherein the portion of the electro-optical modulation module disposed outside the resonant cavity is used to obtain the detection light comb output by the resonant cavity and process the detection light comb to obtain the phase drift and frequency deviation of the detection light comb in real time;

[0011] The electro-optical modulation module is provided in the resonant cavity for dynamically modulating the optical field of the detection optical comb in the resonant cavity in real time based on the phase drift and frequency deviation of the detection optical comb, so that the optical comb mode matches the free spectral range of the resonant cavity;

[0012] The data acquisition and analysis module is used to perform composition and concentration analysis on the gas to be measured based on the detection light comb and the reference light comb.

[0013] Optionally, the resonant cavity includes a cavity body, a first cavity mirror, a second cavity mirror and a beam splitter;

[0014] The cavity comprises an input end and an output end which are opposite to each other, wherein the input end is connected to the dual optical comb output module for receiving the detection optical comb; and the output end is connected to the beam splitter;

[0015] The first cavity mirror and the second cavity mirror are both arranged in the cavity, wherein the first cavity mirror is arranged close to the input end, and the second cavity mirror is arranged close to the output end;

[0016] The electro-optical modulation module is partially arranged between the first cavity mirror and the second cavity mirror;

[0017] The beam splitter is connected to the data acquisition and analysis module and the electro-optical modulation module, and is used to output the detection light comb to the data acquisition and analysis module and the electro-optical modulation module.

[0018] Optionally, the electro-optical modulation module includes a photodetector, a phase-locked loop, a signal generator, an electro-optical modulation driving source and an electro-optical modulation crystal electrically connected in sequence;

[0019] The photodetector is in communication with the beam splitter and is configured to receive the detection light comb;

[0020] The electro-optical modulation crystal is disposed in the cavity and located between the first cavity mirror and the second cavity mirror.

[0021] Optionally, the data acquisition and analysis module includes a beam combiner, a balanced photoelectric detector, an acquisition card and an analysis host;

[0022] The beam combiner is connected to the dual-comb output module, the beam splitter and the balanced photodetector, and is used to obtain the reference light comb and the detection light comb output from the beam splitter, combine them to generate a light domain signal, and output the light domain signal to the balanced photodetector;

[0023] The acquisition card is electrically connected to the balanced photoelectric detector and the analysis host.

[0024] Optionally, the system further comprises a first adjustment component and a second adjustment component;

[0025] Wherein, the first adjustment component is arranged between the dual optical comb output module and the input end;

[0026] The second adjustment component is arranged between the dual-comb output module and the beam combining mirror.

[0027] Optionally, the first adjustment component is a first 1 / 2 wave plate;

[0028] The second adjustment component includes a second 1 / 2 wave plate and a 1 / 4 wave plate arranged in sequence.

[0029] Optionally, the dual optical comb output module is any one of an on-chip optical comb, a single-cavity dual comb, and a frequency- and phase-stable dual comb optical comb.

[0030] In a second aspect, the present invention provides a dual-comb cavity modulation gas measurement method based on electro-optical modulation, which is used in the above-mentioned dual-comb cavity modulation gas measurement system based on electro-optical modulation, comprising:

[0031] S1: Select the gas to be measured, input the gas to be measured into the resonant cavity, and assemble the dual-comb cavity modulation gas measurement system;

[0032] S2: Start the dual-comb output module to output coherent detection and reference optical combs;

[0033] S3: During the measurement process, the detection light comb output by the resonant cavity is obtained in real time using the electro-optical modulation module, and the optical comb module of the detection light comb in the resonant cavity is adjusted in real time to dynamically match the detection light comb in the resonant cavity with the free spectral range of the resonant cavity;

[0034] S4: Using the data acquisition and analysis module, collect and analyze the ring-down signal in the resonant cavity to obtain spectral data;

[0035] S5: Based on the acquired spectral data, combined with the adaptive filtering algorithm, analysis is performed to obtain the concentration, composition, molecular structure and spectral characteristics of the target gas in the gas to be measured.

[0036] Optionally, step S3 specifically includes:

[0037] S3.1: Use a photodetector to obtain the detection light comb output from the resonant cavity from the beam splitter and output it to the phase-locked loop;

[0038] S3.2: Utilize a phase-locked loop (PLL) to acquire the phase drift and frequency deviation of the detection optical comb in real time, and output the phase drift and frequency deviation of the detection optical comb to a signal generator.

[0039] S3.3: Use a signal generator and an electro-optical modulation drive source to drive and modulate the electro-optical modulation crystal according to the phase drift and frequency deviation of the detection light comb, so that the detection light comb in the resonant cavity dynamically matches the free spectral range of the resonant cavity.

[0040] Optionally, step S4 specifically includes:

[0041] S4.1: Use a photoelectric balanced detector to collect the ring-down signal in the resonant cavity. Use dual-channel detection to eliminate the common-mode noise of the ring-down signal to form an intermediate signal.

[0042] S4.2: Use asynchronous sampling to obtain asynchronous sampled data of the intermediate signal;

[0043] S4.3: Based on the frequency domain demodulation algorithm and combined with Fourier transform, the spectral data of the target gas is extracted from the asynchronous sampling data.

[0044] The beneficial effects of the present invention are:

[0045] The present invention provides a dual-comb cavity modulation gas measurement system based on electro-optical modulation. During use, a coherent detection light comb and a reference light comb are generated by a dual-comb output module. The detection light comb enters the resonant cavity to interact with the gas to be measured, and the reference light comb directly reaches the data acquisition and analysis module. The resonant cavity and the dual-comb output module are connected through the data acquisition and analysis module to receive the reference light comb and the detection light comb output from the resonant cavity, and the composition and concentration of the gas to be measured are analyzed based on the detection light comb and the reference light comb. During the measurement process, the electro-optical modulation module is used to obtain the detection light comb output from the resonant cavity in real time, and the light field of the detection light comb in the resonant cavity is dynamically modulated based on the detection light comb, so that its light comb mode matches the free spectral range of the resonant cavity in real time, forming efficient coupling in the resonant cavity, so as to eliminate the influence of gas dispersion effect on measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the dual-comb cavity modulation gas measurement system based on electro-optical modulation in the present invention;

[0047] Figure 2 It is a detailed schematic diagram of the dual-comb cavity modulation gas measurement system based on electro-optical modulation in the present invention.

[0048] Among them: 1. Dual-comb output module; 2. Resonant cavity; 21. Cavity; 22. First cavity mirror; 23. Second cavity mirror; 24. Beam splitter; 3. Data acquisition and analysis module; 31. Beam combiner; 32. Balanced photodetector; 33. Acquisition card; 34. Analysis host; 4. Electro-optical modulation module; 41. Photodetector; 42. Phase-locked loop; 43. Signal generator; 44. Electro-optical modulation drive source; 45. Electro-optical modulation crystal; 5. First 1 / 2 wave plate; 6. Second 1 / 2 wave plate; 7. 1 / 4 wave plate. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0051] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0052] In the description of the present application, it should be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or positional relationship are generally based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, without the opposite statement, these orientation words do not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the scope of protection of the present application: the orientation words "inner, outer" refer to the inner and outer of the contour of each component itself.

[0053] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial positional relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0054] In addition, it should be noted that the use of the words "first", "second" and the like to define parts is only for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, and therefore cannot be understood as a limitation on the scope of protection of the present application.

[0055] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with embodiments.

[0056] The traditional CRDS technology is limited by the narrow band characteristics of a single laser source, resulting in a narrow measurement spectral range. At the same time, the method of mechanically scanning the cavity length is easily affected by environmental vibrations, reducing the measurement accuracy and stability. In addition, the cavity dispersion effect will affect the light field distribution, causing the signal ring-down characteristics to deviate from the ideal case, thereby reducing the measurement accuracy. Therefore, how to maintain the high sensitivity of CRDS while improving the measurement spectral range, reducing the influence of dispersion effect, and improving the measurement stability is a technical problem that needs to be solved at present.

[0057] At the same time, existing CRDS technology also has the following technical issues: 1. Limited measurement range of the ring-down cavity: Current cavity ring-down systems can usually only measure the absorption spectrum of a single gas and cannot measure the absorption characteristics of multiple gases simultaneously. Due to the limitations of the light field distribution and cavity mode coupling within the cavity, existing systems are restricted when measuring the absorption spectra of multiple gases or a wide spectral range. 2. Limited measurement efficiency and time resolution: Traditional gas absorption measurements use a stepper mechanical scanning to adjust the cavity length, which has multiple problems, including slow scanning speed, low measurement efficiency, and susceptibility to external vibration and temperature changes, leading to error accumulation, which in turn affects accuracy and stability. Therefore, improving scanning speed and time resolution and reducing error accumulation are key issues that need to be urgently addressed in current technology.

[0058] Example 1

[0059] First, see Figure 1 and Figure 2 , shows a schematic diagram of a dual-comb cavity modulation gas measurement system based on electro-optical modulation in the present invention, the system includes a dual-comb output module 1, a resonant cavity 2, a data acquisition and analysis module 3 and an electro-optical modulation module 4; the dual-comb output module 1 is used to output a coherent detection light comb and a reference light comb; the resonant cavity 2 is connected to the dual-comb output module 1, and is used to accommodate the gas to be measured and receive the detection light comb; the data acquisition and analysis module 3 is connected to the resonant cavity 2 and the dual-comb output module 1, and is used to receive the reference light comb and the detection light comb output from the resonant cavity; the electro-optical modulation module 4 is partially configured It is arranged in the resonant cavity 2, wherein the part of the electro-optical modulation module 4 arranged outside the resonant cavity 2 is used to obtain the detection light comb output by the resonant cavity 2 and process it to obtain the phase drift and frequency deviation of the detection light comb in real time; the part of the electro-optical modulation module 4 arranged inside the resonant cavity 2 is used to dynamically modulate the light field of the detection light comb in the resonant cavity 2 in real time based on the phase drift and frequency deviation of the detection light comb, so that its light comb mode matches the free spectral range of the resonant cavity; the data acquisition and analysis module 3 is used to analyze the composition and concentration of the gas to be measured based on the detection light comb and the reference light comb.

[0060] In this embodiment, when in use, a coherent detection light comb and a reference light comb are generated by the dual-comb output module 1, the detection light comb enters the resonant cavity 2 to interact with the gas to be measured, and the reference light comb directly reaches the data acquisition and analysis module 3; the resonant cavity 2 and the dual-comb output module 1 are connected through the data acquisition and analysis module 3, which is used to receive the reference light comb and the detection light comb output from the resonant cavity 2, and perform composition and concentration analysis on the gas to be measured based on the detection light comb and the reference light comb; during the measurement process, the electro-optical modulation module 4 is used to obtain the detection light comb output from the resonant cavity 2 in real time, and the light field of the detection light comb in the resonant cavity 2 is dynamically modulated based on the detection light comb, so that its light comb mode matches the free spectral range of the resonant cavity 2 in real time, forming efficient coupling in the resonant cavity 2, so as to eliminate the influence of gas dispersion effect on measurement accuracy.

[0061] Furthermore, the detection light comb in this embodiment enters the resonant cavity as a measurement light comb, and its repetition frequency needs to match the free spectral range of the resonant cavity to ensure that its light comb mode is coupled with the cavity mode and interacts with the gas to be measured; the reference light comb directly enters the data acquisition and analysis module 3 as a reference signal, and is used for noise suppression and signal correction during the detection and demodulation process.

[0062] Optionally, refer to Figure 2 The resonant cavity 2 in the present invention includes a cavity 21, a first cavity mirror 22, a second cavity mirror 23 and a beam splitter 24; the cavity 21 includes an input end and an output end that are opposite to each other, the input end is connected to the dual-comb output module 1 for receiving the detection light comb; the output end is connected to the beam splitter 24; the first cavity mirror 22 and the second cavity mirror 23 are both arranged in the cavity 21, wherein the first cavity mirror 22 is arranged close to the input end and the second cavity mirror 23 is arranged close to the output end; the electro-optical modulation module 4 is partially arranged between the first cavity mirror 22 and the second cavity mirror 23; the beam splitter 24 is connected to the data acquisition and analysis module 3 and the electro-optical modulation module 4, and is used to output the detection light comb to the data acquisition and analysis module 3 and the electro-optical modulation module 4.

[0063] Optionally, refer to Figure 2 The electro-optical modulation module 4 in the present invention includes a photodetector 41, a phase-locked loop 42, a signal generator 43, an electro-optical modulation driving source 44 and an electro-optical modulation crystal 45 which are electrically connected in sequence; the photodetector 41 is connected to the beam splitter 24 for receiving the detection light comb; the electro-optical modulation crystal 45 is arranged in the cavity 21 and is located between the first cavity mirror 22 and the second cavity mirror 23.

[0064] In this embodiment, the detection light comb output from the resonant cavity 2 is split by a beam splitter 24, one beam of the detection light comb enters the data acquisition and analysis module 3 for measurement and analysis, and the other beam of the detection light comb enters the photodetector 41 for collection, and the collected detection light comb is input to the phase-locked loop 42, which obtains the phase drift and frequency deviation of the detection light comb in real time, and feeds back the phase drift and frequency deviation of the detection light comb to the signal generator 43 in real time. The signal generator 43 generates a driving signal based on the phase drift and frequency deviation of the detection light comb, and drives the electro-optical modulation crystal 45 to perform modulation through the output of the electro-optical modulation driving source 44 to optimize the modulation frequency and modulation depth, so that the light field of the detection light comb in the resonant cavity 2 is more uniform, the optical signal distortion caused by the dispersion effect is reduced, and the sensitivity and stability of the measurement of the gas to be measured are improved.

[0065] Furthermore, the first cavity mirror 22 and the second cavity mirror 23 in this embodiment are both high-reflectivity cavity mirrors with a reflectivity higher than 99.99%, so as to form a long optical path enhanced resonant cavity to improve the sensitivity of the gas absorption signal.

[0066] Specifically, the performance of the resonant cavity is mainly characterized by FSR (free spectral range) and F value (fineness).

[0067]

[0068] Where c is the speed of light, and FSR is directly related to the cavity length L of the resonant cavity 2. A larger cavity length will result in a smaller FSR, thereby improving the spectral resolution. In actual use, it is necessary to ensure that the repetition frequency f of the detection optical comb is rep1 Satisfy f rep1 =N×FSR, where N is an integer, to ensure that the detection optical comb has the same frequency as the longitudinal mode of the resonant cavity 2, thereby improving the measurement accuracy and stability.

[0069]

[0070] Here, R is the reflectivity of the first cavity mirror 22 and the second cavity mirror 23, and its value is approximately 1. The higher the F value, the longer the light field is stored in the resonant cavity 2, and the longer the time optical path (even up to the kilometer level), thereby significantly enhancing the interaction between light and gas and improving the detection sensitivity of gas absorption signals. This high-fineness characteristic is crucial for achieving high-precision gas absorption measurements.

[0071] Optionally, the data acquisition and analysis module 3 in the present invention includes a beam combiner 31, a balanced photodetector 32, an acquisition card 33 and an analysis host 34; the beam combiner 31 is connected to the dual optical comb output module 1, the beam splitter 24 and the balanced photodetector 32, and is used to obtain the reference optical comb and the detection optical comb output from the beam combiner 31, combine them to generate an optical domain signal, and output the optical domain signal to the balanced photodetector 32; the acquisition card 33 is electrically connected to the balanced photodetector 32 and the analysis host 34.

[0072] In this embodiment, the detection light comb output from the beam splitter 24 is guided to the beam combiner 31, and the reference light comb and the detection grating are combined in the beam combiner 31 to generate an optical domain signal; the balanced photodetector 32 is used to effectively suppress common mode noise, especially laser intensity noise and environmental noise, and significantly improve the signal-to-noise ratio of the signal, which not only optimizes the dynamic range of the system, but also ensures that weak absorption signals in a high background noise environment can be accurately extracted, thereby enhancing the stability and accuracy of the measurement; the output signal of the balanced photodetector 32 is obtained by the acquisition card 33, converted into a digital signal and output to the analysis host 34, and the dual-comb interference signal is demodulated in the analysis host 34 based on the digital signal, and the absorption spectrum is extracted in combination with Fourier transform technology to achieve high-precision gas analysis.

[0073] Optionally, the system of the present invention further includes a first adjustment component and a second adjustment component; wherein the first adjustment component is arranged between the dual-comb output module and the input end; and the second adjustment component is arranged between the dual-comb output module and the beam combiner.

[0074] Optionally, the first adjustment component in the present invention is a first half wave plate 5 ; the second adjustment component includes a second half wave plate 6 and a quarter wave plate 7 that are sequentially arranged.

[0075] In this embodiment, the first 1 / 2 wave plate 5 is used to adjust the polarization state of the detection light comb before it enters the resonant cavity 2, thereby ensuring the coupling efficiency and cavity mode matching of the optical signal in the resonant cavity 2 and improving the stability during the ring-down process. The second 1 / 2 wave plate 6 and the 1 / 4 wave plate 7 are used to adjust the polarization direction of the reference light comb during beat frequency interference in the beam combiner 31, and optimize the coherence to improve the quality and signal-to-noise ratio of the beat frequency signal, thereby ensuring the measurement accuracy and spectral demodulation performance.

[0076] Optionally, the dual optical comb output module 1 in the present invention is any one of an on-chip optical comb, a single-cavity dual comb, and a frequency- and phase-stable dual comb optical comb.

[0077] Example 2

[0078] In a second aspect, the present invention further provides a dual-comb cavity modulation gas measurement method based on electro-optical modulation, which is used in the dual-comb cavity modulation gas measurement system based on electro-optical modulation in Example 1, comprising:

[0079] S1: Select the gas to be measured, input the gas to be measured into the resonant cavity, and assemble the dual-comb cavity modulation gas measurement system;

[0080] S2: Start the dual-comb output module to output coherent detection and reference optical combs;

[0081] S3: During the measurement process, the detection light comb output by the resonant cavity is obtained in real time using the electro-optical modulation module, and the optical comb module of the detection light comb in the resonant cavity is adjusted in real time to dynamically match the detection light comb in the resonant cavity with the free spectral range of the resonant cavity;

[0082] S4: Using the data acquisition and analysis module, collect and analyze the ring-down signal in the resonant cavity 2 to obtain spectral data;

[0083] S5: Based on the acquired spectral data, combined with the adaptive filtering algorithm, analysis is performed to obtain the concentration, composition, molecular structure and spectral characteristics of the target gas in the gas to be measured.

[0084] Optionally, step S3 specifically includes:

[0085] S3.1: Use a photodetector to obtain the detection light comb output from the resonant cavity from the beam splitter and output it to the phase-locked loop;

[0086] S3.2: Utilize a phase-locked loop (PLL) to acquire the phase drift and frequency deviation of the detection optical comb in real time, and output the phase drift and frequency deviation of the detection optical comb to a signal generator.

[0087] S3.3: Use a signal generator and an electro-optical modulation drive source to drive and modulate the electro-optical modulation crystal according to the phase drift and frequency deviation of the detection light comb, so that the detection light comb in the resonant cavity dynamically matches the free spectral range of the resonant cavity.

[0088] Optionally, step S4 specifically includes:

[0089] S4.1: Use a photoelectric balanced detector to collect the ring-down signal in resonant cavity 2. Use dual-channel detection to eliminate the common-mode noise of the ring-down signal to form an intermediate signal.

[0090] S4.2: Use asynchronous sampling to obtain asynchronous sampled data of the intermediate signal;

[0091] S4.3: Based on the frequency domain demodulation algorithm and combined with Fourier transform, the spectral data of the target gas is extracted from the asynchronous sampling data.

[0092] Furthermore, in this embodiment, after the collected cavity ring-down signal is demodulated using asynchronous sampling technology, the various properties of the gas in the cavity, including but not limited to spectrum, dispersion and concentration, can be inverted using the Beer-Lambert law.

[0093] I=I 0· e -αL

[0094] Where I is the attenuated light intensity, I0 is the initial intensity of the incident light, a is the gas absorption coefficient, which is typically related to the gas concentration, light wavelength, and physical properties of the gas, and L is the cavity length of resonant cavity 2, that is, the propagation distance of the light comb in the gas. In resonant cavity 2, as the light comb propagates through the gas, absorption processes will cause light intensity to decay. If multiple absorption processes occur within the cavity, the total absorption effect of different gas components must also be considered, which can be comprehensively expressed by the total absorption coefficient.

[0095] Furthermore, the intermediate signal in this embodiment is a differential signal.

[0096] In this embodiment, a dual optical comb output module 1 generates coherent detection and reference optical combs. A beam splitter 24 splits the detection light output from the resonant cavity 2. One beam enters the data acquisition and analysis module 3 for measurement and analysis of the gas to be measured, while the other beam enters the photodetector 41 for acquisition. A phase-locked loop 42 analyzes the phase drift and frequency deviation of the detection optical comb in real time. Based on the phase drift and frequency deviation of the detection optical comb, a signal generator 43 and an electro-optical modulation drive source 44 modulate the electro-optical modulation crystal 45 to dynamically match the detection optical comb within the resonant cavity with the free spectral range of the resonant cavity. In the present invention, the electro-optical modulation module 4 is used to obtain the detection optical comb output from the resonant cavity 2 in real time. Based on the detection optical comb, the optical field of the detection optical comb in the resonant cavity 2 is dynamically modulated so that its optical comb mode matches the free spectral range of the resonant cavity 2 in real time, forming efficient coupling within the resonant cavity 2 to eliminate the influence of gas dispersion effects on measurement accuracy.

[0097] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0098] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A dual-comb cavity modulation gas measurement system based on electro-optical modulation, characterized in that: The system comprises a dual optical comb output module (1), a resonant cavity (2), a data acquisition and analysis module (3) and an electro-optical modulation module (4); The dual optical comb output module (1) is used to output coherent detection optical comb and reference optical comb; The resonant cavity (2) is in communication with the dual optical comb output module (1) and is used for accommodating the gas to be measured and receiving the detection optical comb; The data acquisition and analysis module (3) is connected to the resonant cavity (2) and the dual optical comb output module (1), and is used to receive the reference optical comb and the detection optical comb output from the resonant cavity (2); The electro-optical modulation module (4) is partially arranged in the resonant cavity (2), wherein the part of the electro-optical modulation module (4) arranged outside the resonant cavity (2) is used to obtain the detection light comb output by the resonant cavity (2), and to process and obtain the phase drift and frequency deviation of the detection light comb in real time; The electro-optical modulation module (4) is arranged in the resonant cavity (2) for dynamically modulating the light field of the detection light comb in the resonant cavity (2) in real time based on the phase drift and frequency deviation of the detection light comb, so that the light comb mode matches the free spectrum range of the resonant cavity (2); The data acquisition and analysis module (3) is used to perform composition and concentration analysis on the gas to be measured based on the detection light comb and the reference light comb.

2. The dual-comb cavity modulation gas measurement system based on electro-optical modulation according to claim 1 is characterized in that: The resonant cavity (2) comprises a cavity (21), a first cavity mirror (22), a second cavity mirror (23) and a beam splitter (24); The cavity (21) comprises an input end and an output end which are separated from each other, wherein the input end is connected to the dual optical comb output module (1) for receiving the detection optical comb; and the output end is connected to the beam splitter (24); The first cavity mirror (22) and the second cavity mirror (23) are both arranged in the cavity (21), wherein the first cavity mirror (22) is arranged close to the input end, and the second cavity mirror (23) is arranged close to the output end; The electro-optical modulation module (4) is partially arranged between the first cavity mirror (22) and the second cavity mirror (23); The beam splitter (24) is connected to the data acquisition and analysis module (3) and the electro-optical modulation module (4), and is used to output the detection light comb to the data acquisition and analysis module (3) and the electro-optical modulation module (4).

3. The dual-comb cavity modulation gas measurement system based on electro-optical modulation according to claim 2 is characterized in that: The electro-optical modulation module (4) comprises a photodetector (41), a phase-locked loop (42), a signal generator (43), an electro-optical modulation driving source (44) and an electro-optical modulation crystal (45) which are electrically connected in sequence; The photodetector (41) is in communication with the beam splitter (24) and is used to receive the detection light comb; The electro-optical modulation crystal (45) is arranged in the cavity (21) and is located between the first cavity mirror (22) and the second cavity mirror (23).

4. The dual-comb cavity modulation gas measurement system based on electro-optical modulation according to claim 3 is characterized in that: The data acquisition and analysis module (3) comprises a beam combiner (31), a balanced photoelectric detector (32), an acquisition card (33) and an analysis host (34); The beam combining mirror (31) is connected to the dual optical comb output module (1), the beam splitter (24) and the balanced photodetector (32), and is used to obtain the reference optical comb and the detection optical comb output from the beam splitter (24), combine them to generate an optical domain signal, and output the optical domain signal to the balanced photodetector (32); The acquisition card (33) is electrically connected to the balanced photoelectric detector (32) and the analysis host (34).

5. The dual-comb cavity modulation gas measurement system based on electro-optical modulation according to claim 4 is characterized in that: The system further includes a first adjustment component and a second adjustment component; Wherein, the first adjustment component is arranged between the dual optical comb output module (1) and the input end; The second adjustment component is arranged between the dual-comb output module (1) and the beam combining mirror (31).

6. The dual-comb cavity modulation gas measurement system based on electro-optical modulation according to claim 5, characterized in that: The first adjustment component is a first 1 / 2 wave plate (5); The second adjustment component comprises a second 1 / 2 wave plate (6) and a 1 / 4 wave plate (7) which are arranged in sequence.

7. The dual-comb cavity modulation gas measurement system based on electro-optical modulation according to claim 6, characterized in that: The dual optical comb output module (1) is any one of an on-chip optical comb, a single-cavity dual comb, and a frequency- and phase-stable dual comb optical comb.

8. A gas measurement method based on electro-optical modulation and dual-comb cavity modulation, used in the gas measurement system based on electro-optical modulation and dual-comb cavity modulation according to claim 7, characterized in that: include: S1: Select the gas to be measured, input the gas to be measured into the resonant cavity (2), and assemble the dual-comb cavity modulation gas measurement system; S2: Start the dual optical comb output module (1) to output coherent detection optical comb and reference optical comb; S3: During the measurement process, the detection light comb output by the resonant cavity (2) is obtained in real time by using the electro-optical modulation module (4), and the light comb module of the detection light comb in the resonant cavity (2) is adjusted in real time so that the detection light comb in the resonant cavity (2) dynamically matches the free spectrum range of the resonant cavity (2); S4: using the data acquisition and analysis module (3), collecting and analyzing the ring-down signal in the resonant cavity (2) to obtain spectrum data; S5: Based on the acquired spectral data, combined with the adaptive filtering algorithm, analysis is performed to obtain the concentration, composition, molecular structure and spectral characteristics of the target gas in the gas to be measured.

9. The gas measurement method based on electro-optical modulation and dual-comb cavity modulation according to claim 8, characterized in that: The step S3 specifically includes: S3.1: Using a photodetector (41) to obtain the detection light comb output by the resonant cavity (2) from the beam splitter (24), and output it to the phase-locked loop (42); S3.2: Utilize the phase-locked loop (42) to acquire the phase drift and frequency deviation of the detection optical comb in real time, and output the phase drift and frequency deviation of the detection optical comb to the signal generator (43); S3.3: Using a signal generator (43) and an electro-optical modulation drive source (44), the electro-optical modulation crystal (45) is driven and modulated according to the phase drift and frequency deviation of the detection light comb, so that the detection light comb in the resonant cavity (2) dynamically matches the free spectral range of the resonant cavity (2).

10. The gas measurement method based on electro-optical modulation and dual-comb cavity modulation according to claim 8, characterized in that: The step S4 specifically includes: S4.1: Use a photoelectric balanced detector to collect the ring-down signal in the resonant cavity (2), and use dual-channel detection to eliminate the common-mode noise of the ring-down signal to form an intermediate signal; S4.2: Use asynchronous sampling to obtain asynchronous sampled data of the intermediate signal; S4.3: Based on the frequency domain demodulation algorithm and combined with Fourier transform, the spectral data of the target gas is extracted from the asynchronous sampling data.

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