An ultra-low phase noise microwave signal generation method and system based on electro-optical comb

Abstract

The application discloses a kind of ultra-low phase noise microwave signal generation method and system based on electro-optical comb.The method is: 1) two wavelength continuous tunable lasers are locked in the same FP cavity through two links with different modulation frequencies to realize the dual-wavelength laser with frequency interval (v2-v1);2) use residual amplitude modulation noise control technology to suppress the electronic noise of each link to the quantum noise limit;3) the laser with center frequency v1 and v2 is coupled as an input to electro-optical frequency comb generator, to generate two sets of electro-optical frequency comb with spectral overlap;4) obtain the beat signal of two electro-optical frequency combs;The reference signal from the reference signal source is input into the phase detector for phase detection;The output signal of the phase detector is sent to the proportional-integral-derivative control circuit;5) use the output feedback control of proportional-integral-derivative control circuit to control the phase noise of radio frequency source, to obtain ultra-low phase noise microwave signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave photonics, in particular to a method and system for generating ultra-low phase noise microwave signal based on electro-optic comb. The present application uses electro-optic comb as frequency divider to transfer the ultra-low relative phase noise of high-coherence dual-wavelength laser to microwave signal. The ultra-low phase noise microwave signal generated by the present method is suitable for time measurement, radio astronomy, radar, navigation and other fields. BACKGROUND

[0002] Ultra-low phase noise microwave is widely used in basic scientific research and industrial application fields. In basic scientific research, ultra-low phase noise microwave is expected to replace the local oscillator signal in the current fountain atomic clock system, and promote the development of time-frequency science. In the industrial application field, the phase noise of microwave in Doppler radar system will directly determine the positioning accuracy of the system, and ultra-low phase noise microwave can meet the detection requirements of "low, slow and small" targets in Doppler radar system. The microwave signal generated by traditional pure electrical method is generated by frequency multiplication of low-frequency crystal oscillator, and the frequency multiplication process will inevitably worsen the phase noise power spectral density. The space for reducing the phase noise of crystal oscillator is very limited, and it is very challenging to further generate ultra-low phase noise microwave signal by traditional frequency multiplication scheme. With the development of optoelectronic technology, many low-noise optical microwave generation schemes have been proposed and developed. Common optical microwave generation schemes include optoelectronic hybrid oscillator and optical frequency division technology.

[0003] Due to the limitation of 1 / f noise and Leeson effect, the near-carrier frequency offset phase noise of optoelectronic hybrid oscillator is usually 1 / f 3The slope of the phase noise decreases, so the near-carrier frequency offset (1 Hz) phase noise is usually poor [Reference: D. Eliyahu, et al., “Phase noise of a high performance OEO and an ultra-low noise floor cross-correlation microwave photonic homodyne system,” in Proceedings of 2002 IEEE International Frequency Control Symposium (2008), pp. 811-814.]. The optical frequency division technology uses an optical frequency comb as a large coefficient frequency divider to divide the low-noise laser into a microwave, and the generated microwave signal can have ultra-low phase noise at both near-carrier frequency offset (1 Hz) and far-carrier frequency offset (10 kHz). The traditional optical frequency division scheme uses a fiber optical frequency comb to divide a single-wavelength laser into a microwave, and in 2017, the Paris Observatory in France and Menlo Company in Germany cooperated to achieve a record-breaking ultra-low phase noise 12 GHz microwave, with a single sideband phase noise better than -107 dBc / Hz@1 Hz, -173 dBc / Hz@10 kHz [Reference: Xie, Xiaopeng, et al. “Photonic microwave signals withzeptosecond-level absolute timing noise.” Nature Photonics 11.1 (2017): 44-47.]. However, the traditional optical frequency division scheme requires an optical frequency comb covering an octave, and also requires a high nonlinear photodetector, and the frequency of the optical frequency comb is not adjustable. The two-point frequency division method based on the electro-optical comb can overcome the above difficulties, in 2014, California Institute of Technology in the United States and the National Institute of Standards and Technology in the United States cooperated to use an electro-optical comb to divide a dual-wavelength Brillouin laser into a microwave, and to realize a low phase noise microwave [Reference: J. Li, et al., “Electro-optical frequency division and stable microwave synthesis,” Science 345 (2014): 309-313.]. Later, this scheme was developed into a product by the American hQphotonics company, and in 2017, the company reported at the International Frequency Control Forum conference that the 30 GHz microwave signal generated by the product had a phase noise of -87 dBc / Hz@10 Hz, -151 dBc / Hz@10 kHz, but was limited by the Brillouin laser, and its near-carrier frequency offset (1 Hz) phase noise was poor. SUMMARY

[0004] Two-point frequency division method based on electro-optical comb can overcome the limitations of traditional optical frequency division scheme, but it needs a dual-wavelength laser with low relative phase noise. In order to improve the performance of the microwave generated by the two-point frequency division method based on electro-optical comb, the present application provides a method and system for generating ultra-low phase noise microwave signal based on electro-optical comb. The present application uses Pound-Drever-Hall technology to lock two semiconductor lasers to the same Fabry-Pérot cavity to realize a dual-wavelength laser. The residual amplitude modulation noise control technology is used to suppress the relative phase noise of the dual-wavelength laser to the quantum noise limit. The output laser of the dual-wavelength laser (with center frequencies of v1 and v2, respectively) is input into an electro-optical comb generator composed of several phase modulators to obtain two sets of electro-optical combs, and the center frequencies v1 and v2 of the dual-wavelength laser are separated by n electro-optical comb teeth (such as n=21). An optical filter is used to filter out the overlapping comb teeth and input them into a fiber-optic photoelectric detector to obtain a difference frequency signal, and the frequency of the difference frequency signal is the frequency difference of the dual-wavelength laser minus n times the repetition frequency of the electro-optical comb. After detecting the frequency of the difference frequency signal, the frequency of the reference source is set to be the same. The phase error signal obtained by phase demodulating the difference frequency signal and the reference signal with the same frequency is fed back to the electro-optical comb driving source to form a phase-locked loop, and at this time the phase noise of the driving source is the relative phase noise of the dual-wavelength laser minus 20*log(n), that is, the ultra-low phase noise microwave signal is generated.

[0005] The technical solution adopted by the present application to solve its technical problems is:

[0006] A method for generating ultra-low phase noise microwave signal based on electro-optical comb, comprising the following steps:

[0007] 1) Two independent wavelength continuously tunable lasers are locked in the same Fabry-Pérot cavity through two Pound-Drever-Hall links with different modulation frequencies to realize a dual-wavelength laser with a frequency interval of (v2-v1), and each link is driven by a double-channel radio frequency signal source to drive a phase modulator with different modulation frequencies;

[0008] 2) The residual amplitude modulation noise control technology is used to control the phase modulator to suppress the electronic noise of the two Pound-Drever-Hall links to the quantum noise limit;

[0009] 3) The output of the dual-wavelength laser is coupled into an electro-optical frequency comb generator to generate two sets of electro-optical frequency combs with overlapping spectra, otherwise the difference frequency signal cannot be obtained; wherein the electro-optical frequency comb generator is driven by a radio frequency source with a frequency of f r The radio frequency driving power of the electro-optical frequency comb generator should be large enough to ensure that the two sets of electro-optical combs have overlapping comb teeth.

[0010] 4) using adjustable optical filter to filter out the overlapping part of a pair of electro-optical frequency comb teeth, sending the output of the optical filter into the fiber photoelectric detector to obtain the beat frequency signal; wherein n is the total number of teeth between the center wavelengths of the two independent lasers;

[0011] 5) the beat frequency signal output from the fiber photoelectric detector is connected to the reference signal from the reference signal source into the phase detector for phase discrimination; the output signal of the phase detector is sent into the proportional-integral-derivative control circuit; the beat frequency signal is theoretically the same as the frequency of the reference signal, both of which are (ν2-ν1-nf r );

[0012] 6) the output of the proportional-integral-derivative control circuit is fed back to the RF source controller of the electro-optical frequency comb generator to realize the phase-locked loop control of the RF source phase noise, and an ultra-low phase noise microwave signal with a frequency of f r is obtained.

[0013] Further, the wavelength continuously tunable laser has a working wavelength near 1550 nm, and the Fabry-Perot cavity has a center wavelength near 1550 nm.

[0014] Further, the Pound-Drever-Hall link optical part includes a double-channel RF signal source, a phase modulator, a collimator, a half-wave plate, a polarization beam splitter prism, a quarter-wave plate, and a spatial light photoelectric detector; a pair of phase opposite sidebands are generated after the laser passes through the phase modulator driven by one output of the double-channel RF signal source. After the laser passes through the phase modulator, the phase modulator is connected to the collimator, and the free space light is converted from the fiber light through the collimator. The polarization state of the free space light is adjusted to P light input into the polarization beam splitter prism through the half-wave plate. The light transmitted and output by the polarization beam splitter prism passes through the quarter-wave plate and is incident to the Fabry-Perot cavity. The reflected light after the light beam is reflected by the Fabry-Perot cavity will carry frequency offset information; the reflected light passes through the quarter-wave plate again and the polarization state is S light, which is reflected to the spatial light photoelectric detector by the polarization beam splitter prism.

[0015] Further, the Pound-Drever-Hall link electrical part includes a phase detector and a proportional-integral-derivative control circuit; the spatial light photoelectric detector outputs the frequency offset information, which is connected to the other output of the double-channel RF signal source through the phase detector to generate an error signal, which is input into the proportional-integral-derivative control circuit, and the output of the proportional-integral-derivative control circuit is fed back to the laser to realize locking.

[0016] Further, the performance of the electro-optical frequency comb generator should be able to make the two sets of electro-optical frequency comb spectra generated by the dual-wavelength laser have overlapping parts, that is, the single-sideband bandwidth of the electro-optical frequency comb should reach (v2-v1) / 2; the electro-optical frequency comb generator includes a plurality of cascaded phase modulators, all of which are driven by an external frequency f r The plurality of cascaded phase modulators used to form the electro-optical frequency comb generator are used to spread the spectrum of the seed light output by the laser to obtain a multi-tooth electro-optical frequency comb.

[0017] Further, the tunable optical filter should be able to realize optical filtering with a bandwidth of f r Further, the tunable optical filter should be able to realize optical filtering with a bandwidth of f

[0018] Further, the reference signal with the same frequency as the output signal of the fiber-optic photoelectric detector should have the characteristic of low phase noise.

[0019] Further, the phase detector and the proportional-integral-derivative circuit should have the characteristic of low additional phase noise.

[0020] An ultra-low phase noise microwave signal generation system based on an electro-optical comb, characterized by comprising a laser, a dual-channel radio frequency signal source, a phase modulator, a fiber coupler, a collimator, a half-wave plate, a polarization beam splitter prism, a quarter-wave plate, a Fabry-Pérot cavity, a spatial light photoelectric detector, a phase detector, a proportional-integral-derivative control circuit, an electro-optical frequency comb generator, a fiber-optic photoelectric detector, a reference signal source, and a radio frequency source; wherein

[0021] The laser is used to generate a seed light source.

[0022] The dual-channel radio frequency signal source outputs one for driving the phase modulator and one for phase detection of the output of the fiber-optic photoelectric detector; the modulator is connected with one output of the dual-channel radio frequency signal source and is used to modulate the input seed light source to generate a pair of phase-opposed sidebands; wherein the modulation frequencies of the two links are different.

[0023] The fiber coupler is used for coupling the outputs of the two lasers; the collimator is used for converting fiber light into free-space light; the collimator, the half-wave plate, the polarization beam splitter prism, and the quarter-wave plate are used to realize the Pound-Drever-Hall technology.

[0024] The electro-optical frequency comb generator is used to convert the dual-wavelength laser into two sets of electro-optical frequency combs; the tunable optical filter is used to filter out the cross-comb teeth; the fiber-optic photoelectric detector is used to detect the frequency information of the cross-comb teeth; and the reference signal source is used to provide a frequency reference.

[0025] The phase detector, the proportional-integral-differential circuit are used for phase detection of two Pound-Drever-Hall links, and phase detection of fiber photoelectric detector output and a reference source;

[0026] The output of the radio frequency source is divided into two parts, one part is used as a driving source of an electro-optical frequency comb generator, and the other part is used as an ultra-low phase noise microwave signal output.

[0027] The application uses Pound-Drever-Hall technology to lock two semiconductor lasers in the same Fabry-Pérot cavity to realize a dual-wavelength laser; uses residual amplitude modulation noise control technology to reduce the electronic noise of two Pound-Drever-Hall links to the quantum noise limit; the output of the dual-wavelength laser obtains two sets of electro-optical combs through an electro-optical comb generator composed of a plurality of phase modulators, and the two sets of electro-optical combs have an interleaved part; an optical filter is used to filter out a pair of comb teeth beat frequency, and then the phase is detected with a reference source to obtain an error signal, which is fed back to the radio frequency driving source to form a phase-locked loop, so as to realize phase compression of the radio frequency driving source.

[0028] The application has the following beneficial effects:

[0029] The application provides a convenient and robust ultra-low phase noise microwave generation method, which is suitable for time frequency metrology, radio astronomy, radar, navigation and the like, and is used for supporting more accurate, more precise and more precise detection. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a schematic diagram of a dual-wavelength laser based on Pound-Drever-Hall technology of the application;

[0031] Figure 2 It is a relative phase noise test diagram of the dual-wavelength laser, and here, a Fabry-Pérot cavity with a longitudinal mode interval of 1.5 GHz is taken as an example;

[0032] Figure 3 It is a phase-locked loop schematic diagram of the application;

[0033] Figure 4 It is an electro-optical comb spectrum diagram of the application, and here, a dual-wavelength laser with a spacing of 525 GHz and an electro-optical comb comb tooth repetition frequency of 25 GHz is taken as an example;

[0034] Figure 5 It is the phase noise of the microwave generated by the application, and here, a dual-wavelength laser with a spacing of 525 GHz and an electro-optical comb comb tooth repetition frequency of 25 GHz is taken as an example, and the microwave phase noise is reduced by 26 dB compared with the relative phase noise of the dual-wavelength laser.

[0035] Wherein, 1. continuous wave laser, 2. phase modulator, 3. collimator, 4. half wave plate, 5. polarization beam splitter prism, 6. quarter wave plate, 7. Fabry-Pérot cavity, 8. spatial light photodetector, 9. double-channel radio frequency signal source, 10. phase detector, 11. proportional-integral-derivative control circuit, 12. electro-optical comb generator, 13. fiber photodetector, 14. reference signal source, 15. radio frequency source, 16 adjustable optical filter. DETAILED DESCRIPTION

[0036] The scheme of the application will be described in further detail below with reference to the accompanying drawings.

[0037] The scheme principle of the dual-wavelength laser of the application is shown in Figure 1 Two lasers 1 with wavelength around 1550 nm are used as seed light sources, and are respectively input into phase modulators 2 driven by a double-channel radio frequency signal source 9. The frequencies used in the two seed light sources are 36 MHz and 51 MHz respectively. The outputs of the two phase modulators 2 are coupled, and a part of the outputs is input into a collimator 3 to become spatial light, and the other part is input into an electro-optical comb generator 12. The spatial light passes through a half wave plate 4 to adjust the polarization state, and is completely reflected by a polarization beam splitter prism 5, and then passes through a quarter wave plate 6 to be incident on a Fabry-Pérot cavity 7. The reflected light is reflected by the Fabry-Pérot cavity 7 while carrying frequency shift information, and then passes through the quarter wave plate 6 again to be reflected by the polarization beam splitter prism 5 to a spatial light photodetector 8 to obtain 36 MHz and 51 MHz signals. The output of the spatial light photodetector 8 is divided into two parts and then input into a phase detector 10. The other end of the phase detector 10 is connected to the double-channel radio frequency signal source 9. The error signal obtained by the phase detection is related to the difference between the frequency of the laser 1 and the transmission frequency of the Fabry-Pérot cavity 7. The error signal is input into a proportional-integral-derivative circuit 11, and a control signal output by the proportional-integral-derivative circuit 11 is used to control the laser 1 to realize Pound-Drever-Hall technology locking. After the wavelength of the laser 1 is adjusted to the transmission frequency of the Fabry-Pérot cavity 7, the laser 1 is locked to the transmission frequency of the Fabry-Pérot cavity 7, and the frequency value is recorded as v1. The relative phase noise of the dual-wavelength laser is suppressed to the quantum noise limit by combining the residual amplitude modulation noise control technology, as shown in Figure 2 The relative phase noise when the two lasers 1 are separated by a Fabry-Pérot cavity 7 mode is shown. It should be noted that the driving frequency of the double-channel radio frequency signal source is not limited to the above parameter settings, and it is possible as long as Pound-Drever-Hall locking is ensured.

[0038] The scheme principle of the phase-locked loop of the application is shown in Figure 3The electric-optic comb generator 12 is composed of two phase modulators in series, which are driven by the same radio frequency signal source 15 with a frequency of f r =25GHz. The output signal of the radio frequency signal source 15 is divided into three paths by a power divider, one of which is used for output, and the other two are respectively used to drive the phase modulators through phase shifters and radio frequency amplifiers. Therefore, the two lasers generate two sets of electric-optic frequency combs with a frequency interval of f r =25GHz through the electric-optic comb generator 12. As shown in the figure, the spectrum of the electric-optic frequency comb is shown. Figure 4 As shown in the figure, the spectrum of the electric-optic frequency comb is shown. A pair of comb teeth of the electric-optic frequency comb is sent into the fiber photoelectric detector 13 to obtain a signal with a beat frequency of (v2-v1-nf r ); where n is the total number of comb teeth between the center wavelengths of the two lasers. The signal is sent to the phase detector 10, which is additionally connected to the same frequency reference signal source 14. The phase detector 10 outputs a phase error signal to the proportional-integral-derivative control circuit 11, which outputs an error signal to control the radio frequency source 15 to achieve phase locking, thereby obtaining an ultra-low phase noise microwave signal with a frequency of 25GHz. Note that the output frequency of the radio frequency signal source is not limited to the above parameter settings, as long as the two sets of electric-optic frequency combs overlap. In addition, the above electric-optic comb generator 12 belongs to the type of cascaded modulator, and the number of phase modulators is not limited to two. The main function of the phase modulator is to broaden the spectrum, and more phase modulators can obtain a wider spectrum and achieve a higher frequency division coefficient. The electric-optic comb generator can also use an electric-optic comb generator based on a thin film lithium niobate sheet. Figure 5 The phase noise figure of the low noise microwave signal generated by the method is shown, where the interval between the two wavelength lasers is 525GHz, and the driving frequency of the radio frequency signal source is 25GHz.

[0039] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Those skilled in the art can modify or equivalently replace the technical solutions of the present application without departing from the spirit and scope of the present application. The protection scope of the present application should be subject to the claims.

Claims

1. A method for generating an ultra-low phase noise microwave signal based on an electro-optical comb, comprising: 1) Two continuously tunable lasers with different modulation frequencies are locked into the same Fabry–Pérot cavity via two Pound–Drever–Hall links to achieve a dual-wavelength laser with a frequency interval of (v2-v1); wherein the center frequencies of the laser outputs of the dual-wavelength lasers are v1 and v2, respectively; 2) using residual amplitude modulation noise control technology to reduce the electronic noise of each Pound-Drever-Hall link to the quantum noise limit; each Pound-Drever-Hall link includes an optical part and an electrical part; the optical part includes a dual-channel RF signal source, a phase modulator, a collimator, a half-wave plate, a polarization beam splitter, a quarter-wave plate, and a spatial light photodetector; one end of the phase modulator is connected to the laser through an optical fiber for receiving the seed laser output by the laser, and the other end of the phase modulator is connected to one output end of the dual-channel RF signal source for receiving the dual-channel radiation. The driving signal of the frequency signal source modulates the input seed laser to generate a pair of sidebands with opposite phases, which are then input into the collimator through the fiber coupler. The collimator converts the fiber light into free-space light and inputs it into the half-wave plate. The half-wave plate adjusts the polarization state of the incident free-space light to P light and inputs it into the polarization beam splitter prism. The light outputted through the polarization beam splitter prism passes through the quarter-wave plate and is incident on the Fabry–Pérot cavity. The reflected light carrying the frequency offset information after being reflected by the Fabry–Pérot cavity passes through the quarter-wave plate, and the polarization state of the reflected light is adjusted to S light, and then it is reflected by the polarization beam splitter prism to the spatial light photodetector. The electrical part includes a phase detector and a proportional-integral-differential control circuit; the output signal of the spatial light photodetector and the other output signal of the dual-channel RF signal source are respectively input into the phase detector for phase detection to generate an error signal, which is then input into the proportional-integral-differential control circuit; the output of the proportional-integral-differential control circuit is fed back to the laser to achieve locking; The dual-channel RF signal sources in the two Pound-Drever-Hall links drive the phase modulators at different modulation frequencies; 3) The lasers outputted by the dual-wavelength lasers with center frequencies v1 and v2 are coupled as one input to an electro-optical frequency comb generator to generate two sets of electro-optical frequency combs with spectral overlap; wherein the electro-optical frequency comb generator is composed of a frequency of f r RF source driver; 4) using a tunable optical filter to filter out a pair of electro-optical frequency comb teeth having overlapping spectra of the two sets of electro-optical frequency combs and sending them into an optical fiber photodetector to obtain a beat frequency signal; 5) The beat signal and the reference signal from the reference signal source are connected to the phase detector for phase detection; the output signal of the phase detector is sent to the proportional-integral-differential control circuit; the frequency of the reference signal is (v2-v1-nf r ); Where n is the total number of comb teeth between the two laser center frequencies output by the dual-wavelength laser; 6) Feedback the output of the proportional-integral-differential control circuit to the controller of the radio frequency source to realize phase-locked loop control of the phase noise of the radio frequency source, and obtain a frequency of f r Ultra-low phase noise microwave signal.

2. The method according to claim 1, characterized in that The single-side bandwidth of the electro-optic frequency comb reaches (v2-v1) / 2.

3. The method according to claim 1 or 2, characterized in that The electro-optical frequency comb generator includes several cascaded phase modulators, each of which is driven by an external frequency of f r RF signal source driver.

4. The method according to claim 1, wherein The tunable optical filter can achieve a bandwidth of f r optical filtering.

5. An ultra-low phase noise microwave signal generation system based on an electro-optical comb, characterized in that: It includes two lasers, two dual-channel RF signal sources, two phase modulators, fiber couplers, collimators, half-wave plates, polarization beam splitters, quarter-wave plates, Fabry–Pérot cavities, spatial light photodetectors, three phase detectors, three proportional-integral-differential control circuits, an electro-optical frequency comb generator, a tunable optical filter, a fiber photodetector, a reference signal source, and a RF source. in One end of the first phase modulator is connected to the first laser via an optical fiber, and is used to receive the seed laser output by the first laser; the other end of the first phase modulator is connected to one output end of the first dual-channel RF signal source, and is used to receive the driving signal of the first dual-channel RF signal source to modulate the input seed laser to generate a pair of sidebands with opposite phases, and input the sidebands into the collimator through the optical fiber coupler; One end of the second phase modulator is connected to the second laser via an optical fiber, and is used to receive the seed laser output by the second laser; the other end of the second phase modulator is connected to one output end of the second dual-channel RF signal source, and is used to receive the driving signal of the second dual-channel RF signal source to modulate the input seed laser to generate a pair of sidebands with opposite phases, and input them into the collimator through the optical fiber coupler; The collimator converts the fiber light into free-space light and inputs it into the half-wave plate. The half-wave plate adjusts the polarization state of the incident free-space light to P light and inputs it into the polarization beam splitter prism. The light outputted by the polarization beam splitter prism passes through the quarter-wave plate and is incident on the Fabry–Pérot cavity. The reflected light carrying the frequency shift information after being reflected by the Fabry–Pérot cavity passes through the quarter-wave plate, and the polarization state is adjusted to S light, and then reflected by the polarization splitter prism to the spatial light photodetector; The first phase detector is used to perform phase detection on the output signal of the spatial light photoelectric detector and the other output signal of the first dual-channel radio frequency signal source to generate an error signal and input the error signal into the first proportional-integral-differential control circuit. The output of the first proportional-integral-differential control circuit is fed back to the first laser to achieve phase locking. The second phase detector is used to perform phase detection on the output signal of the spatial light photodetector and the other output signal of the second dual-channel RF signal source to generate an error signal and input the error signal into the second proportional-integral-differential control circuit. The output of the second proportional-integral-differential control circuit is fed back to the second laser to achieve phase locking. The optical fiber coupler is used to couple the first laser and the laser output by the phase-locked first laser to obtain dual-wavelength lasers with laser center frequencies v1 and v2 respectively, and input them into the electro-optical frequency comb generator; The electro-optical frequency comb generator is used to convert the dual-wavelength laser into two sets of electro-optical frequency combs with spectral overlap; The electro-optical frequency comb generator consists of a frequency of f r The radio frequency source driving; The tunable optical filter is used to filter out a pair of electro-optical frequency comb teeth of the overlapping part of the spectrum of the two sets of electro-optical frequency combs and send them into the optical fiber photodetector to obtain a beat frequency signal; where n is the total number of comb teeth between frequencies v1 and v2; The third phase detector is used to perform phase detection on the input beat frequency signal and the reference signal from the reference signal source, and send the output signal to the third proportional-integral-differential control circuit; the frequency of the reference signal is (v2-v1-nf r ); The output feedback of the third proportional-integral-differential control circuit controls the controller of the radio frequency source to realize the phase-locked loop control of the phase noise of the radio frequency source, and obtains the frequency f r Ultra-low phase noise microwave signal; Among them, the first phase modulator, the first dual-channel radio frequency signal source, the optical fiber coupler, the collimator, the half-wave plate, the polarization beam splitter, the quarter-wave plate, the Fabry–Pérot cavity, the spatial light photodetector, the first phase detector, and the first proportional-integral-differential control circuit constitute a first Pound-Drever-Hall link; the second phase modulator, the second dual-channel radio frequency signal source, the optical fiber coupler, the collimator, the half-wave plate, the polarization beam splitter, the quarter-wave plate, the Fabry–Pérot cavity, the spatial light photodetector, the second phase detector, and the second proportional-integral-differential control circuit constitute a second Pound-Drever-Hall link; the modulation frequency of the first phase modulator driven by the first dual-channel radio frequency signal source is different from the modulation frequency of the second phase modulator driven by the second dual-channel radio frequency signal source.

6. The system according to claim 5, characterized in that The single-side bandwidth of the electro-optic frequency comb reaches (v2-v1) / 2.

7. The system according to claim 5 or 6, characterized in that The electro-optical frequency comb generator includes several cascaded phase modulators, each of which is driven by an external frequency of f r RF signal source driver.

8. The system according to claim 5, wherein: The tunable optical filter can achieve a bandwidth of f r optical filtering.

9. The system according to claim 5, characterized in that The residual amplitude modulation noise control technology is used to control the first phase modulator and the second phase modulator to reduce the electronic noise of the two-way Pound-Drever-Hall link to the quantum noise limit.

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