An ultrafast microwave frequency measurement method and device based on optical chirped chain and gas absorption

Abstract

The application discloses a kind of based on optical chirp chain and gas absorption ultrafast microwave frequency measurement method and device, it is related to microwave frequency measurement technical field.The technical points of the present application include: light source is as carrier wave and is formed optical chirp chain after frequency modulation;Extract the lower sideband of optical chirp chain;The lower sideband of optical chirp chain is loaded to be measured microwave signal, after gas absorption, conversion obtains the time-domain electric signal of to-be-measured microwave;To-be-measured microwave time-domain electric signal is demodulated, including obtaining the absorption peak position of time-domain electric signal, the absorption peak position can be demodulated to obtain the microwave frequency to be measured in each sampling period.The present application utilizes optical chirp chain to realize the continuous measurement of microwave frequency, and the gas absorption signal produced is connected head to tail in time domain, and direct collection time-domain signal can complete the real-time monitoring of microwave frequency measurement;Further, introduce reference microwave frequency to compensate the wavelength fluctuation of light source.The present application has strong measurement stability, and can realize ultrafast microwave frequency measurement.

Description

Technical Field

[0001] This invention relates to the field of microwave frequency measurement technology, specifically to an ultrafast microwave frequency measurement method and apparatus based on optical chirp chains and gas absorption. Background Technology

[0002] Microwave frequency measurement is one of the most fundamental applications of microwave measurement theory and technology. It has been widely used in many fields, such as astronomy, communications, radar, electronic warfare, and even healthcare. Parameters characterizing the performance of a microwave frequency measurement system include measurement speed, accuracy and resolution, instantaneous bandwidth, and frequency coverage. Currently, the most direct method for microwave frequency measurement still uses electrical methods. With the increase in data volume and the development of high-speed communication, photonic microwave measurement technology is becoming increasingly prominent. It not only overcomes the bandwidth limitations of traditional electrical methods to analyze microwave signals in the high-frequency domain, but also features low loss and resistance to electromagnetic interference.

[0003] For photonic microwave frequency measurement, the most widely used method currently is to construct a frequency-amplitude mapping curve using the complementary responses of two filters, mapping the microwave frequency to the probe signal intensity. Therefore, this method offers fast response and a wide frequency coverage. However, as a measurement element, the complementary filter is susceptible to noise from temperature, light source wavelength drift, vibration, and other factors. This not only affects the system's stability but also reduces the accuracy of microwave frequency measurement.

[0004] To improve frequency measurement accuracy, stimulated Brillouin scattering (SBS) has been introduced into photonic microwave frequency measurements in recent years. Here, the Brillouin gain spectrum acts like a narrowband filter; microwaves falling within the gain range are amplified, thus compressing the Brillouin gain spectrum width can further improve frequency measurement accuracy. Furthermore, wavelength drift from the light source is canceled out by SBS. However, microwave frequency measurements based on SBS require a frequency sweep process to measure the Brillouin spectrum, resulting in slow measurement speed. Additionally, when using ordinary single-mode fiber as the SBS medium, the measuring element is affected by temperature and environmental vibration noise, requiring careful temperature and vibration isolation for storage. To generate a stable SBS effect, a strong pump light injection is typically needed, increasing system performance requirements.

[0005] In summary, existing microwave frequency measurement technologies have poor stability, are greatly affected by environmental noise such as temperature and vibration, and have low measurement efficiency. Summary of the Invention

[0006] To address this, the present invention proposes an ultrafast microwave frequency measurement method and apparatus based on optical chirp chains and gas absorption, in an attempt to solve or at least alleviate at least one of the problems mentioned above.

[0007] According to one aspect of the present invention, an ultrafast microwave frequency measurement method based on optical chirp chains and gas absorption is provided, the method comprising the following steps:

[0008] The light source acts as a carrier wave, and frequency modulation is used to form an optical chirp chain;

[0009] Extract the lower sideband of the optical chirp chain;

[0010] The microwave signal to be measured is loaded onto the lower sideband of the optical chirped chain, and after absorption by the gas, it is converted into the time-domain electrical signal of the microwave to be measured.

[0011] The microwave time-domain electrical signal to be tested is demodulated, including obtaining the absorption peak position of the time-domain electrical signal. The microwave frequency to be tested in each sampling period can be obtained by demodulating the absorption peak position.

[0012] Furthermore, the microwave frequency to be measured within each sampling period is calculated as follows:

[0013] ν mi =ν a -ν c +α·t pi

[0014] In the formula, ν a Indicates the frequency of gas absorption peaks; ν c The frequency of the light source carrier wave is represented by α; the chirp rate is represented by t. pi This indicates the time-domain position where the light intensity decreases within the i-th optical chirp segment, i.e., the position of the absorption peak generated by the microwave under test within the i-th sampling period.

[0015] Furthermore, after extracting the lower sideband of the optical chirp chain, the measured microwave time-domain electrical signal is compensated using a reference microwave time-domain electrical signal to eliminate errors caused by light source frequency fluctuations, thus obtaining the compensated measured microwave frequency. Specifically, this includes:

[0016] The lower sideband of the optical chirped chain is loaded with the microwave signal to be measured and the reference microwave signal, respectively. The microwave signal to be measured and the reference microwave signal are absorbed by the gas and then converted to obtain the corresponding microwave time-domain electrical signal to be measured and the reference microwave time-domain electrical signal.

[0017] Since the light source frequency fluctuates, the reference microwave frequency in the i-th sampling period obtained by demodulation based on the absorption peak position in the reference microwave time-domain electrical signal is:

[0018] ν ri =ν a -ν c +α·t pr +Δν i =ν r +Δνi

[0019] In the formula, t pr Indicates the position of the absorption peak generated by the reference microwave; ν r Indicates the reference microwave frequency standard value; Δν i This represents the fluctuation of the light source frequency within the i-th sampling period;

[0020] The microwave time-domain electrical signal to be measured is compensated using a reference microwave time-domain electrical signal. The compensated microwave frequency in the i-th sampling period is then:

[0021] ν cmi =ν mi '-ν ri +ν r =α·(t) pi -t pr )+ν r

[0022] In the formula, ν mi '=ν a -ν c +α·t pi +Δν i This indicates the frequency of the microwave under test obtained by demodulation, which is affected by fluctuations in the frequency of the light source.

[0023] Furthermore, the gas is acetylene.

[0024] According to another aspect of the present invention, an ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption is provided. The device includes: a first laser, a first electro-optic modulator, a chirp chain module, a first circulator, a second laser, a second electro-optic modulator, a microwave signal to be measured, a second circulator, a gas cell, a third circulator, a first detector, and a data acquisition module; wherein,

[0025] The output light from the first laser enters the first electro-optic modulator, and the optical signal output from the first laser is modulated by the modulation signal loaded by the chirped chain module, and modulated into an optical chirped chain signal with upper and lower sidebands.

[0026] The optical chirped chain signals of the upper and lower sidebands are injected into the second laser through the first circulator to extract the lower sideband of the optical chirped chain, and then output through the first circulator.

[0027] The lower sideband of the optical chirped chain enters the second electro-optic modulator, and the lower sideband of the optical chirped chain is modulated by the applied microwave signal to be tested;

[0028] The modulated optical signal passes through the second circulator, the air cell, and the third circulator, and is received by the first detector, converting the optical signal into an electrical signal; finally, it is acquired by the data acquisition module.

[0029] Furthermore, it also includes: a coupler, a reference microwave signal, a third electro-optic modulator, and a second detector; among which,

[0030] The output light from the first laser enters the first electro-optic modulator, and the optical signal output from the first laser is modulated by the modulation signal loaded by the chirped chain module, and modulated into an optical chirped chain signal with upper and lower sidebands.

[0031] The optical chirped chain signals of the upper and lower sidebands are injected into the second laser through the first circulator to extract the lower sideband of the optical chirped chain, and then output through the first circulator.

[0032] The lower sideband of the optical chirped chain is split into two beams by the coupler. One beam enters the second electro-optic modulator, where the lower sideband of the optical chirped chain is modulated by the applied microwave signal to be tested. The modulated optical signal passes through the second circulator, the air cell, and the third circulator, and is received by the first detector, which converts the optical signal into an electrical signal. Finally, the signal is acquired by the data acquisition module.

[0033] Another beam enters the third electro-optic modulator, modulating the lower sideband of the optical chirped chain with a loaded reference microwave signal; the modulated optical signal passes through the third circulator, the gas cell, and the second circulator, and is received by the second detector, converting the optical signal into an electrical signal; finally, it is acquired by the data acquisition module.

[0034] Furthermore, the first laser and the second laser are distributed feedback fiber lasers.

[0035] Furthermore, it also includes a demodulation module, and the data acquisition module is connected to the demodulation module; the demodulation module is used to demodulate the microwave time-domain electrical signal to be tested and the reference microwave time-domain electrical signal acquired by the data acquisition module, and to compensate the microwave time-domain electrical signal to be tested using the reference microwave time-domain electrical signal to obtain the compensated microwave frequency to be tested.

[0036] Furthermore, the compensated frequency of the microwave under test is expressed as:

[0037] ν cmi =ν mi '-ν ri +ν r =α·(t) pi -t pr )+ν r

[0038] In the formula, ν cmi ν represents the measured microwave frequency in the i-th sampling period after compensation; mi '=ν a -ν c +α·t pi +Δνi This represents the demodulated microwave frequency obtained under test, which is affected by fluctuations in the light source frequency; ν ri ν represents the reference microwave frequency within the i-th sampling period; r Indicates the reference microwave frequency standard value; α represents the chirp rate; t pi t represents the position of the absorption peak generated by the microwave under test during the i-th sampling period; pr This indicates the position of the absorption peak generated by the reference microwave.

[0039] Furthermore, the reference microwave frequency ν in the i-th sampling period ri Represented as:

[0040] ν ri =ν a -ν c +α·t pr +Δν i =ν r +Δν i

[0041] In the formula, ν a Indicates the frequency of gas absorption peaks; ν c Indicates the frequency of the light source carrier wave; Δν i This represents the frequency fluctuation of the light source during the i-th sampling period.

[0042] The beneficial technical effects of this invention are:

[0043] This invention proposes an ultrafast microwave frequency measurement method and apparatus based on optical chirped chains and gas absorption to achieve ultrafast microwave frequency measurement. This invention utilizes optical chirped chains to achieve continuous microwave frequency measurement, and the generated gas absorption signals are concatenated in the time domain, allowing for real-time monitoring of microwave frequency measurement by directly acquiring the time-domain signals.

[0044] This invention offers strong measurement stability. Since the frequency of the gas absorption peak is only related to the gas composition, when the gas composition is determined, the absorption peak frequency is absolutely fixed and will not be affected by environmental noise such as temperature and vibration, thus ensuring measurement stability. Furthermore, the gas absorption spectrum is symmetrical, making demodulation of the gas absorption spectrum simpler and less prone to introducing demodulation errors. In addition, the introduction of a reference frequency to compensate for the wavelength fluctuation of the light source can also eliminate the fluctuation noise of other instruments in the system, enhancing the stability and robustness of the system. Attached Figure Description

[0045] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein:

[0046] Figure 1 This is a schematic diagram illustrating the principle of an ultrafast microwave frequency measurement method based on optical chirp chains and gas absorption according to an embodiment of the present invention.

[0047] Figure 2 This is a structural diagram of an ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption according to an embodiment of the present invention;

[0048] Figure 3 This is another structural diagram of an ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption according to an embodiment of the present invention. Detailed Implementation

[0049] The principles and spirit of the invention will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are given merely to enable those skilled in the art to better understand and implement the invention, and are not intended to limit the scope of the invention in any way. Rather, these embodiments are provided to make this disclosure more thorough and complete, and to fully convey the scope of this disclosure to those skilled in the art.

[0050] This invention proposes an ultrafast microwave frequency measurement method based on optical chirp chains and gas absorption, which can achieve ultrafast and high-performance microwave frequency measurement.

[0051] Gas absorption is a phenomenon related to the physical properties of gas molecules. When the emission spectrum of a light source overlaps with the absorption spectrum of gas molecules, it induces transitions in gas particles, leading to a decrease in the intensity of light at the response wavelength and the formation of a definite gas absorption spectral line. When the gas composition is fixed, the absorption peak position of the gas absorption spectrum is absolutely stable and unaffected by environmental noise such as temperature and vibration. Therefore, gas absorption peaks are often used for wavelength calibration in many applications. The spectral standard for gas absorption peaks is also relevant. By changing the gas concentration or pressure, narrow-spectrum gas absorption spectra can be obtained. Furthermore, the gas absorption process is independent of the injected light intensity, eliminating the need for high-intensity light detection. In recent years, optical chirped chain technology has been proposed, enabling ultrafast (tens of ns) frequency sweeps over a wide frequency range (several GHz), showing great potential in ultrafast measurements. Therefore, combining these two technologies can achieve microwave frequency measurements with high stability, resistance to environmental noise such as temperature and vibration, and ultrafast measurement capabilities.

[0052] An ultrafast microwave frequency measurement method based on optical chirp chains and gas absorption includes the following steps:

[0053] The light source acts as a carrier wave, and frequency modulation is used to form an optical chirp chain;

[0054] Extract the lower sideband of the optical chirp chain;

[0055] The microwave signal to be measured is loaded onto the lower sideband of the optical chirped chain, and after absorption by the gas, it is converted into the time-domain electrical signal of the microwave to be measured.

[0056] Demodulating the microwave time-domain electrical signal to be tested involves obtaining the absorption peak position of the time-domain electrical signal. The microwave frequency to be tested in each sampling period can be obtained by using the absorption peak position.

[0057] Specifically, the principle of ultrafast microwave frequency measurement based on optical chirp chains and gas absorption is as follows: Figure 1 As shown. The light source frequency is ν. c As a carrier wave, frequency modulation forms an optical chirp chain. The optical chirp chain consists of n chirp segments connected in series in the time domain. The frequency distribution is a sawtooth or triangular waveform, and more complex frequency distributions can also be generated to achieve a large-range frequency sweep in a short time. The frequency range swept by the chirp segment is called the chirp width ν. chirp The duration of a chirping segment is called the chirping period t. chirp The ratio of the two is called the chirping rate α = ν. chirp / t chirp Here, the lower sideband of the frequency modulation is chosen as the optical chirp chain, such as... Figure 1 As shown in (a), the time-frequency relationship of each chirped segment is expressed as follows:

[0058] ν c -α·t(0≤t≤t chirp (1)

[0059] In the formula, ν c α represents the carrier frequency of the light source; α represents the chirping rate of the optical chirp chain; t represents time; t chirp This indicates the chirping period.

[0060] The frequency of the microwave under test varies continuously in the time domain. Each chirped segment in the optical chirped chain is equivalent to one sampling of the frequency of the microwave under test in the time domain, and the sampling period is equal to the chirped period t. chirp .like Figure 1 As shown in (b), the frequency ν is obtained by sampling within the sampling period. si (i = 1, 2, ..., n). The lower sideband of the optical chirped chain is used to load the microwave signal to be measured, such as... Figure 1 As shown in (c), the time-frequency relationship of the i-th optical chirp segment is expressed as:

[0061] ν c -α·t+ν si (i = 1, 2, ..., n, 0 ≤ t ≤ t) chirp (2)

[0062] In the formula, ν si This represents the microwave frequency to be measured during the i-th sampling period.

[0063] When the optical chirp chain of the microwave to be measured sweeps through the gas absorption peak ν... a At that time, due to the effect of gas absorption, at frequency ν a A decrease in light intensity occurs at that location. For example... Figure 1 As shown in (d), the time-domain location where the light intensity decreases within the i-th optical chirp segment is:

[0064] ν a =ν c -α·t pi +ν si (i=1,2,...,n) (3)

[0065] In the formula, ν a Indicates the frequency of gas absorption peaks; t pi This indicates the time-domain position where the light intensity decreases within the i-th optical chirp segment, i.e., the position of the absorption peak generated by the microwave under test within the i-th sampling period.

[0066] Light source carrier frequency ν c and gas absorption peak ν a The sampling frequency ν is fixed, due to the corresponding sampling frequency ν in each sampling period. si (i = 1, 2, ..., n) changes, such as Figure 1 As shown in (d), the temporal position t of the absorption peak pi (i = 1, 2, ..., n) will change with the sampling frequency. Therefore, by acquiring the time-domain signal and determining the absorption peak position, the sampling frequency within each sampling period can be obtained through demodulation.

[0067] ν mi =ν a -ν c +α·t pi (i = 1, 2, ..., n) (4)

[0068] In the formula, ν mi This represents the frequency of the microwave to be measured in the i-th sampling period obtained by demodulation.

[0069] Finally, the microwave frequency to be measured is recovered based on the sampling time sequence (i = 1, 2, ..., n), thus realizing real-time microwave frequency monitoring.

[0070] It should be noted that the upper sideband of frequency modulation can also be selected as the optical chirp chain.

[0071] However, in practice, distributed feedback lasers are commonly used as the light source, and the frequency of the light source fluctuates randomly: ν c ±Δν will introduce measurement error. Therefore, using a reference microwave of a known frequency to measure simultaneously with the microwave under test will eliminate the error caused by fluctuations in the light source frequency.

[0072] Assuming the reference microwave frequency ν r The reference microwave frequency demodulated from the absorption peak position in the time-domain signal can be expressed as a combination of the standard value of the reference microwave frequency and the fluctuation of the light source frequency:

[0073] ν ri =ν a -ν c +α·t pr +Δν i =ν r +Δν i (i=1,2,...,n) (5)

[0074] In the formula, ν ri t represents the reference microwave frequency within the i-th sampling period obtained by demodulation; pr Indicates the position of the absorption peak generated by the reference microwave; ν r Indicates the reference microwave frequency standard value; Δν i This represents the frequency fluctuation of the light source during the i-th sampling period.

[0075] The demodulated microwave frequency is also affected by fluctuations in the light source frequency.

[0076] ν mi =ν a -ν c +α·t pi +Δν i (i = 1, 2, ..., n) (6)

[0077] Simultaneously acquiring time-domain signals generated by the reference microwave and the microwave under test, the light source frequency fluctuations are identical at the same time. After compensation, the influence caused by the light source frequency fluctuations can be directly eliminated.

[0078] ν cmi =ν mi -ν ri +ν r =α·(t) pi -t pr )+ν r (i=1,2,...,n) (7)

[0079] In the formula, ν cmi ν represents the measured microwave frequency in the i-th sampling period after compensation; mi ν represents the frequency of the microwave to be measured within the i-th sampling period obtained by demodulation; ri t represents the reference microwave frequency within the i-th sampling period obtained by demodulation; pi t represents the position of the absorption peak generated by the microwave under test during the i-th sampling period; pr Indicates the position of the absorption peak generated by the reference microwave; νr This indicates the reference microwave frequency standard value.

[0080] Another embodiment of the present invention proposes an ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption, such as... Figure 2 As shown, the device includes: a first laser 1, a first electro-optic modulator 2, a chirped chain module 3, a first circulator 4, a second laser 5, a second electro-optic modulator 7, a microwave signal to be measured 8, a second circulator 11, a gas cell 12, a third circulator 13, a first detector 16, and a data acquisition module 15; the measurable frequency range of the device is ν. c -α·t chirp ~ν c .in,

[0081] The output light from the first laser 1 enters the first electro-optic modulator 2, and the optical signal output from the first laser 1 is modulated by the modulation signal loaded by the chirped chain module 3, and modulated into an optical chirped chain signal with upper and lower sidebands.

[0082] The optical chirped chain signals of the upper and lower sidebands are injected into the second laser 5 through the first circulator 4 to extract the lower sideband of the optical chirped chain, and then output through the first circulator 4.

[0083] The lower sideband of the optical chirped chain enters the second electro-optic modulator 7, and the lower sideband of the optical chirped chain is modulated by the applied microwave signal 8.

[0084] The modulated optical signal passes through the second circulator 11, the air cell 12, and the third circulator 13, and is received by the first detector 16, which converts the optical signal into an electrical signal; finally, it is acquired by the data acquisition module 15.

[0085] The device also includes: a coupler 6, a reference microwave signal 9, a third electro-optic modulator 10, and a second detector 14; as shown below. Figure 3 As shown, a first laser 1 with a wavelength around 1530nm, namely a distributed feedback fiber laser, is used as the light source to facilitate the tuning of the light source wavelength.

[0086] The output light from the first laser 1 first passes through the first electro-optic modulator 2, and is modulated into optical chirped chain signals for the upper and lower sidebands by the modulation signal loaded by the chirped chain module 3. The first electro-optic modulator 2 operates at its lowest operating point. The chirped chain module 3 generates the modulation signal, which is loaded onto the first electro-optic modulator 2 to produce the optical chirped chain signals. The optical chirped chain signals for the upper and lower sidebands are injected into the distributed feedback laser (second laser 5) without an internal isolator via the first circulator 4, locking the lower sideband to achieve extraction of the optical chirped chain modulation sideband. This injection-locking technique not only enables the extraction of filtered sidebands with high extinction ratios but also effectively suppresses the intensity modulation noise of the electro-optic modulator 1. The injection-locked optical chirped chain sideband is used to load the microwave signal under test and is output via the first circulator 4.

[0087] Furthermore, due to the generally poor stability of the distributed feedback fiber laser 1, its output wavelength fluctuates, introducing significant measurement errors. Therefore, a microwave of a known frequency is used as a reference signal to compensate for the wavelength drift of the first laser 1. Thus, the injected and locked optical chirped chain sideband is split into two beams by coupler 6. One beam, after being loaded with the microwave signal 8 to be measured by the second electro-optic modulator 7 and absorbed by the gas in the gas cell 12, is received by the first detector 16, converting the optical signal into an electrical signal. The other beam, after being loaded with the reference microwave signal 9 of a known frequency by the third electro-optic modulator 10, is also absorbed by the gas in the gas cell 12 and received by the second detector 14, converting the optical signal into an electrical signal. The electrical signals generated by the first detector 16 and the second detector 14 are simultaneously acquired by the data acquisition module 15, obtaining the time-domain signals of the microwave to be measured and the reference microwave, respectively.

[0088] Furthermore, it also includes a demodulation module, with the data acquisition module 15 connected to the demodulation module. The demodulation module is used to demodulate the time-domain electrical signal of the microwave under test and the reference microwave time-domain electrical signal acquired by the data acquisition module 15. During signal demodulation, the time-domain signal generated by the reference microwave is used to compensate for the time-domain signal generated by the microwave under test, so as to eliminate the influence caused by the wavelength drift of the first laser 1, and at the same time, it can also eliminate the influence of other noise in the system.

[0089] First, the absorption peak positions of the microwave under test and the reference microwave are obtained by demodulating the time-domain signals of the collected microwave under test and reference microwave. Then, the frequency value of the microwave under test after compensation is finally obtained according to formula (7).

[0090] It should be noted that acetylene was chosen as the gas for gas absorption because it has abundant absorption peaks in the communication band and has strong absorption intensity.

[0091] The function of the ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption described in this embodiment can be explained by the aforementioned ultrafast microwave frequency measurement method based on optical chirp chains and gas absorption. For parts not described in detail in this embodiment, please refer to the above method embodiments.

[0092] While the spirit and principles of the invention have been described with reference to several specific embodiments, it should be understood that the invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that features in these aspects cannot be combined for benefit; such division is merely for ease of description. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for measuring ultrafast microwave frequencies based on optical chirp chains and gas absorption, characterized in that, Includes the following steps: The light source acts as a carrier wave, and frequency modulation is used to form an optical chirp chain; Extract the lower sideband of the optical chirp chain; The microwave signal to be measured is loaded onto the lower sideband of the optical chirped chain, and after absorption by the gas, it is converted into the time-domain electrical signal of the microwave to be measured. The microwave time-domain electrical signal to be tested is demodulated, including obtaining the absorption peak position of the time-domain electrical signal. The microwave frequency to be tested in each sampling period can be obtained by demodulating the absorption peak position.

2. The ultrafast microwave frequency measurement method based on optical chirp chains and gas absorption according to claim 1, characterized in that, The microwave frequency to be measured in each sampling period is calculated as follows: ； In the formula, Indicates the frequency of gas absorption peaks; Indicates the frequency of the light source carrier wave; Indicates the chirping rate; This indicates the time-domain position where the light intensity decreases within the i-th optical chirp segment, i.e., the position of the absorption peak generated by the microwave under test within the i-th sampling period.

3. The ultrafast microwave frequency measurement method based on optical chirp chains and gas absorption according to claim 2, characterized in that, After extracting the lower sideband of the optical chirp chain, the time-domain electrical signal of the microwave under test is compensated using a reference microwave time-domain electrical signal to eliminate errors caused by fluctuations in the light source frequency, thus obtaining the compensated microwave frequency under test. Specifically, this includes: The lower sideband of the optical chirped chain is loaded with the microwave signal to be measured and the reference microwave signal, respectively. The microwave signal to be measured and the reference microwave signal are absorbed by the gas and then converted to obtain the corresponding microwave time-domain electrical signal to be measured and the reference microwave time-domain electrical signal. Since the light source frequency fluctuates, the reference microwave frequency in the i-th sampling period obtained by demodulation based on the absorption peak position in the reference microwave time-domain electrical signal is: ； In the formula, Indicates the position of the absorption peak generated by the reference microwave; This indicates the reference microwave frequency standard value; This represents the fluctuation of the light source frequency within the i-th sampling period; The microwave time-domain electrical signal to be measured is compensated using a reference microwave time-domain electrical signal. The compensated microwave frequency in the i-th sampling period is then: ； In the formula, This indicates the frequency of the microwave under test obtained by demodulation, which is affected by fluctuations in the frequency of the light source.

4. A method for measuring ultrafast microwave frequencies based on optical chirp chains and gas absorption according to any one of claims 1-3, characterized in that, The gas is acetylene.

5. An ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption, characterized in that, include: The system comprises a first laser (1), a first electro-optic modulator (2), a chirped chain module (3), a first circulator (4), a second laser (5), a second electro-optic modulator (7), a microwave signal to be measured (8), a second circulator (11), a gas cell (12), a third circulator (13), a first detector (16), and a data acquisition module (15); among which, The output light of the first laser (1) enters the first electro-optic modulator (2), and the optical signal output by the first laser (1) is modulated by the modulation signal loaded by the chirped chain module (3) to form an optical chirped chain signal with upper and lower sidebands. The optical chirped chain signals of the upper and lower sidebands are injected into the second laser (5) through the first circulator (4) to extract the lower sideband of the optical chirped chain and output through the first circulator (4); The lower sideband of the optical chirped chain enters the second electro-optic modulator (7), and the lower sideband of the optical chirped chain is modulated by the loaded microwave signal to be tested (8); The modulated optical signal passes through the second circulator (11), the air cell (12), and the third circulator (13), and is received by the first detector (16), converting the optical signal into an electrical signal; finally, it is collected by the data acquisition module (15).

6. The ultrafast microwave frequency measurement device based on optical chirp chain and gas absorption according to claim 5, characterized in that, Also includes: Coupler (6), reference microwave signal (9), third electro-optic modulator (10), second detector (14); wherein, The output light of the first laser (1) enters the first electro-optic modulator (2), and the optical signal output by the first laser (1) is modulated by the modulation signal loaded by the chirped chain module (3) to form an optical chirped chain signal with upper and lower sidebands. The optical chirped chain signals of the upper and lower sidebands are injected into the second laser (5) through the first circulator (4) to extract the lower sideband of the optical chirped chain and output through the first circulator (4); The lower sideband of the optical chirped chain is split into two beams by the coupler (6). One beam enters the second electro-optic modulator (7), which modulates the lower sideband of the optical chirped chain by the applied microwave signal (8). The modulated optical signal passes through the second circulator (11), the gas cell (12), and the third circulator (13), and is received by the first detector (16), which converts the optical signal into an electrical signal. Finally, the signal is acquired by the data acquisition module (15). Another beam enters the third electro-optic modulator (10) and modulates the lower sideband of the optical chirped chain by the loaded reference microwave signal (9); the modulated optical signal passes through the third circulator (13), the gas cell (12), the second circulator (11), and is received by the second detector (14) to convert the optical signal into an electrical signal; finally, it is collected by the data acquisition module (15).

7. An ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption according to claim 5 or 6, characterized in that, The first laser (1) and the second laser (5) are distributed feedback fiber lasers.

8. An ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption according to claim 5 or 6, characterized in that, It also includes a demodulation module, and the data acquisition module (15) is connected to the demodulation module; the demodulation module is used to demodulate the microwave time-domain electrical signal to be tested and the reference microwave time-domain electrical signal acquired by the data acquisition module (15), and to use the reference microwave time-domain electrical signal to compensate the microwave time-domain electrical signal to be tested, so as to obtain the compensated microwave frequency to be tested.

9. The ultrafast microwave frequency measurement device based on optical chirp chain and gas absorption according to claim 8, characterized in that, The compensated microwave frequency to be measured is expressed as: ； In the formula, This represents the frequency of the microwave to be measured in the i-th sampling period after compensation. This represents the measured microwave frequency obtained through demodulation, which is affected by fluctuations in the light source frequency. Indicates the frequency of gas absorption peaks. Indicates the frequency of the light source carrier wave. This represents the fluctuation of the light source frequency within the i-th sampling period; This represents the reference microwave frequency during the i-th sampling period; This indicates the reference microwave frequency standard value; Indicates the chirping rate; This indicates the position of the absorption peak generated by the microwave under test during the i-th sampling period; This indicates the position of the absorption peak generated by the reference microwave.

10. The ultrafast microwave frequency measurement device based on optical chirp chains and gas absorption according to claim 9, characterized in that, Reference microwave frequency in the i-th sampling period Represented as: 。

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