A microwave generation method based on monolithic integrated orthogonal double soliton optical comb

Abstract

The invention discloses a microwave generation method based on a monolithic integrated orthogonal polarization double soliton optical comb. A tunable laser outputs continuous laser as a pump laser, which is input into a modulator for modulation, and then amplified and filtered to obtain an orthogonal pump laser. The orthogonal pump lasers are then respectively amplified by amplifiers, combined into one beam by a coupler, and input into an optical microcavity through a circulator. Meanwhile, an auxiliary laser output by another tunable laser is input into the optical microcavity through a circulator after passing through a polarization controller and an amplifier. Finally, the wavelength of the auxiliary laser is tuned multiple times to enable the optical microcavity to excite an orthogonal double soliton optical comb in a red detuning region, and then filtered and converted to generate a microwave signal.

Description

Technical Field

[0001] The present invention belongs to the field of optical communication technology, and more specifically, relates to a microwave generation method based on a monolithic integrated orthogonal double soliton optical comb. Background Art

[0002] Microwave signal sources are an important part of modern electronic systems. They are widely used in many fields such as communication, radar, electronic countermeasures, satellite navigation, telemetry and remote control. The function realization of a large number of electronic equipment and systems directly depends on the performance of the frequency source used. For example, in radar systems, signal sources with high stability and low phase noise can improve the radar's ability to distinguish moving targets; in satellite navigation systems, high-quality signal sources can provide the system with a stable time reference, thereby achieving more accurate positioning. It can be seen that with the continuous development of electronic technology, various electronic systems have higher and higher requirements for microwave frequency sources. It is of great significance to study microwave frequency sources with wide bandwidth, low phase noise and low spurious.

[0003] Traditionally, microwave frequency source signals are generated by electronic oscillators, and high-frequency microwave signals are generated by multiple frequency multiplication and amplification of low-frequency oscillation sources. However, this traditional method is greatly limited as the frequency increases, resulting in significant degradation of the phase noise of the generated high-frequency microwave signal and high cost. Therefore, traditional electrical methods can no longer meet the requirements of high-frequency, low-noise, and high-power microwave signal generation.

[0004] In recent years, people have begun to try to use optical methods to generate microwave signals. Compared with traditional electro-generated microwave signal methods, optical microwave methods have the advantages of large bandwidth, low loss, wide tuning range and anti-electromagnetic interference. Among the many optical microwave schemes, the optical microwave scheme based on optical frequency combs has attracted more and more attention from researchers due to its excellent noise performance. It is particularly noteworthy that in recent years, a new optical frequency comb generation scheme, namely the Kerr light comb generated by the Kerr effect in optical microcavities, has been proposed and widely used, providing a new tool for the realization of optical frequency dividers and ultra-low phase noise microwave signal generation. However, we note that the frequency of the optical microwave signal based on the microcavity Kerr light comb is determined by the comb tooth spacing of the light comb, and the comb tooth spacing of the Kerr light comb is usually determined by the geometric size of the optical microcavity. Once an optical microcavity is prepared, its geometric size will be fixed and cannot be changed. Therefore, the frequency of the microwave signal based on the Kerr light comb is fixed and cannot be flexibly adjusted. To address this problem, researchers proposed using two optical microcavities to generate two Kerr light combs with different repetition frequencies, and using the beat frequency signals between the corresponding comb teeth of the two optical combs to generate microwave signals. Since the repetition frequencies of the two optical combs are different, according to the vernier effect, we know that different comb tooth pairs can generate a series of microwave signals with a frequency difference equal to the repetition frequency difference of the two optical combs. This scheme successfully solved the problem of frequency tuning of optically generated microwave signals, but since the two Kerr light combs are generated in two different optical microcavities, environmental noise, microcavity thermal noise, and laser frequency noise will degrade the coherence between the two optical combs, thereby degrading the noise characteristics of the microwave signal. In order to solve this problem, researchers proposed to generate two Kerr light combs simultaneously in the same microcavity. This scheme can effectively alleviate the degradation of microwave signals caused by noise, but since the two optical combs are generated at resonant wavelengths of different wavelengths of the same polarization, the repetition frequency difference between the two optical combs is very small, often only a few MHz. Therefore, the tunability of optically generated microwave signals is very poor. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a microwave generation method based on a monolithic integrated orthogonal double soliton optical comb, which generates a low-noise, frequency-tunable microwave signal by generating a polarization orthogonal double optical comb in a single optical microcavity.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a microwave generation method based on a monolithic integrated orthogonal double soliton optical comb, characterized in that it comprises the following steps:

[0007] (1) Generate orthogonal dual pump lasers;

[0008] (1.1) Use a modulator to modulate the sideband of the pump light;

[0009] A tunable laser is used as a pump laser source to output continuous pump light with adjustable wavelength, which is then input to the modulator through an optical fiber. At the same time, a microwave source generates a microwave sinusoidal signal and inputs it to the modulator as a modulation signal.

[0010] In the modulator, the modulator modulates the continuous pump light with the modulation signal to obtain multiple sideband pump light signals, and then the multiple sideband pump light signals are amplified by the amplifier and filtered by the bandpass filter, and the two sideband signals with the highest amplitude are retained;

[0011] (1.2) Using a polarization controller to generate TE mode pump light and TM mode pump light;

[0012] The polarization states of the two sideband signals are adjusted by using a polarization controller, so that the polarization state of one sideband signal is aligned with the TE mode of the optical microcavity, and the polarization state of the other sideband signal is aligned with the TM mode of the optical microcavity, thereby obtaining TE mode pump light and TM mode pump light;

[0013] (1.3) Use a coupler to synthesize orthogonal dual pump lasers;

[0014] After the TE mode pump light and the TM mode pump light are input into the erbium-doped fiber amplifier for optical power amplification, the two beams of light are combined into one laser beam by a coupler, and then input from port 1 of the first circulator and output from port 2 to the optical microcavity; at the same time, port 3 of the first circulator is connected to a power meter to monitor the optical power of the auxiliary laser input into the optical microcavity;

[0015] (2) Produce auxiliary laser;

[0016] In addition, a tunable laser is selected as an auxiliary laser source to output auxiliary laser, and then a polarization controller is used to adjust the polarization state of the auxiliary laser so that the polarization state of the auxiliary laser is aligned with the TE mode or TM mode of the optical microcavity. Then, an erbium-doped fiber amplifier is used to amplify the power and input it through port 1 of the second circulator and output it to the optical microcavity through port 2. At the same time, a spectrometer and an optical filter are connected to port 3 of the second circulator.

[0017] (3) Generate polarization orthogonal double soliton optical comb;

[0018] (3.1) Using the auxiliary laser heating effect to make the pump laser enter the microcavity resonance peak;

[0019] Input the pump laser and the auxiliary laser into the optical microcavity from different directions, observe the power value of the power meter, and when the power value reaches the threshold, tune the auxiliary laser wavelength to enter the resonance peak of the optical microcavity. At this time, due to the thermal nonlinear effect of the optical microcavity, the resonance peak will move toward the long wavelength direction, so that the pump laser passively enters the resonance peak of the optical microcavity and is in the blue detuning region of the resonance peak.

[0020] (3.2) Tuning the microcavity resonance peak wavelength to generate polarization orthogonal double soliton optical comb;

[0021] The wavelength of the auxiliary laser is tuned again. Due to the thermal nonlinear effect of the optical microcavity, the resonance peak moves toward the short wavelength direction, so that the relative resonance peak position of the pump laser moves toward the long wavelength direction. The spectrometer is used to observe that the pump laser smoothly transitions from the blue detuning region to the red detuning region. Then, the wavelength of the auxiliary laser is continued to be tuned, and the spectrometer is used to observe whether the pump laser generates a polarization orthogonal double soliton light comb in the red detuning region. If so, proceed to step (4); otherwise, change the wavelength of the tunable laser and return to step (1).

[0022] (4) Generate microwave signals

[0023] The optical microcavity outputs an orthogonal double soliton light comb, which is filtered out using an optical filter and then input into a photodetector to be converted into an electrical signal, thereby generating a microwave signal.

[0024] The object of the invention of the present invention is achieved in this way:

[0025] The present invention is based on a microwave generation method of a monolithically integrated orthogonal polarization double soliton optical comb. A tunable laser outputs a continuous laser as a pump laser, which is input into a modulator for modulation, and then amplified and filtered to obtain an orthogonal pump laser. The orthogonal pump lasers are then respectively amplified by amplifiers, combined into one beam by a coupler, and input into an optical microcavity through a circulator. At the same time, an auxiliary laser output by another tunable laser is input into the optical microcavity through a circulator after passing through a polarization controller and an amplifier. Finally, the auxiliary laser wavelength is tuned multiple times to enable the optical microcavity to excite an orthogonal double soliton optical comb in a red detuning region, and then a microwave signal is generated after filtering and radio-to-electric conversion.

[0026] At the same time, the microwave generation method based on the monolithic integrated orthogonal double soliton optical comb of the present invention also has the following beneficial effects:

[0027] (1) The orthogonal polarization dual combs are generated in a single optical microcavity, which can effectively suppress the degradation of the coherence characteristics between the dual combs caused by external environmental factors, achieving higher system integration, lower power consumption, and smaller size;

[0028] (2) Compared with the same polarization double soliton optical comb scheme, this technical solution has two advantages: (a) Since the mutual interference between the two modes of the orthogonal scheme is smaller, the impact on the soliton mode locking process is smaller, and it is easier to achieve the generation of orthogonal double solitons; (b) Compared with the same polarization double solitons, the comb teeth spacing of orthogonal solitons is larger, so that a wider range of optical microwave signals can be adjusted. In addition, the mode spacing of the orthogonal mode can be optimized by changing the waveguide cross-sectional area, which is more flexible;

[0029] (3) The orthogonal polarization dual combs are generated in a single optical microcavity, which can effectively avoid the degradation of the dual comb coherence caused by factors such as environmental noise and microcavity thermal noise, that is, the optically generated microwave signal can obtain lower noise characteristics;

[0030] (4) By introducing an auxiliary laser, the present invention can overcome the thermal instability in the process of soliton locking of the optical comb, reduce the difficulty of generating an orthogonal double soliton optical comb, and thus reduce the complexity of the system; compared with the fast laser scanning scheme, this scheme can realize the independent adjustment of the orthogonal double soliton locking mode state and has higher flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a diagram of the microwave generation architecture based on a monolithic integrated orthogonal double soliton optical comb of the present invention;

[0032] Figure 2 It is a flow chart of the microwave generation method based on a monolithic integrated orthogonal double soliton optical comb of the present invention;

[0033] Figure 3 It is the test result of Q value and dispersion characteristics of silicon nitride micro-ring cavity;

[0034] Figure 4 This is a typical polarization orthogonal double soliton spectrum;

[0035] Figure 5 It is the process of independent generation of polarization orthogonal double soliton optical combs;

[0036] Figure 6 It is the spectrum diagram of photogenerated microwave signal. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention is described below in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0038] Example

[0039] Figure 1This is a diagram of the microwave generation architecture based on a monolithically integrated orthogonal double soliton optical comb according to the present invention.

[0040] In this embodiment, if Figure 1 As shown in FIG. 1 , the entire device is divided into three branches, wherein the generation of polarization orthogonal dual-comb in a single optical microcavity includes a pump light branch and an auxiliary laser branch, and a microwave branch that converts the polarization orthogonal dual-comb into a microwave signal; Figure 1 A microwave generation method based on a monolithic integrated orthogonal double soliton optical comb is described in detail. Figure 2 As shown, the specific steps include:

[0041] S1, produces orthogonal dual pump lasers;

[0042] S1.1. Use a modulator to modulate the sideband of the pump light;

[0043] A tunable laser is used as a pump laser source to output continuous pump light with adjustable wavelength, which is then input to the modulator through an optical fiber. At the same time, a microwave source generates a microwave sinusoidal signal and inputs it to the modulator as a modulation signal.

[0044] In the modulator, the modulator modulates the continuous pump light with the modulation signal to obtain multiple sideband pump light signals, and then the multiple sideband pump light signals are amplified by the amplifier to compensate for the insertion loss of the modulator. Then, the spontaneous radiation noise introduced by the optical amplifier is filtered out through the bandpass filter, and the two sideband signals with the highest amplitude are retained.

[0045] S1.2, using a polarization controller to generate TE mode pump light and TM mode pump light;

[0046] The polarization states of the two sideband signals are adjusted by using a polarization controller, so that the polarization state of one sideband signal is aligned with the TE mode of the optical microcavity, and the polarization state of the other sideband signal is aligned with the TM mode of the optical microcavity, thereby obtaining TE mode pump light and TM mode pump light;

[0047] S1.3, using a coupler to synthesize orthogonal dual pump lasers;

[0048] After the TE mode pump light and the TM mode pump light are input into the erbium-doped fiber amplifier for optical power amplification, the two beams of light are combined into one laser beam by a coupler, and then input from port 1 of the first circulator and output from port 2 to the optical microcavity; at the same time, port 3 of the first circulator is connected to a power meter to monitor the optical power of the auxiliary laser input into the optical microcavity;

[0049] S2, generate auxiliary laser;

[0050] In addition, a tunable laser is selected as an auxiliary laser source to output the auxiliary laser, and then the polarization state of the auxiliary laser is adjusted by a polarization controller so that the polarization state of the auxiliary laser is aligned with the TE mode or TM mode of the optical microcavity. Then, the auxiliary laser is input through port 1 of the second circulator after power amplification by an erbium-doped fiber amplifier, and output to the optical microcavity through port 2. At the same time, a spectrometer and an optical filter are connected to port 3 of the second circulator, wherein the spectrometer is used to monitor the change process of the spectrum in the process of generating an orthogonal double soliton optical comb, and the optical filter is used to filter out the double soliton optical comb generated by the optical microcavity.

[0051] S3, generating polarization orthogonal double soliton optical comb;

[0052] S3.1, using the auxiliary laser heating effect to make the pump laser enter the microcavity resonance peak;

[0053] Input the pump laser and the auxiliary laser into the optical microcavity from different directions, observe the power value of the power meter, and when the power value reaches the threshold, tune the auxiliary laser wavelength to enter the resonance peak of the optical microcavity. When the auxiliary laser enters the resonance peak, we observe that the power meter shows that the power will continue to decrease. At this time, due to the thermal nonlinear effect of the optical microcavity, the resonance peak will move toward the long wavelength direction, so that the pump laser passively enters the resonance peak of the optical microcavity and is in the blue detuning region of the resonance peak. At this time, observing the spectrometer, it can be found that the spectrum shows that the optical comb state is in the primary optical comb state or the secondary optical comb state.

[0054] S3.2. Tuning the microcavity resonance peak wavelength to generate polarization orthogonal double soliton optical comb;

[0055] Tune the wavelength of the auxiliary laser again. Due to the thermal nonlinear effect of the optical microcavity, the resonance peak moves toward the short wavelength direction, so that the pump laser moves toward the long wavelength relative to the resonance peak position. At this time, observing the spectrometer, it can be found that the light comb generated by the pump laser is gradually dense. When the light comb state changes from the primary light comb state to the secondary light comb state and finally to the chaotic light comb state, the auxiliary laser can offset the influence of the thermal effect generated by the pump laser entering the red detuning region of the resonance peak. Therefore, it is observed through the spectrometer that the pump laser can smoothly transition from the blue detuning region to the red detuning region and can stably exist in the red detuning region. At this time, it can be observed that the light comb state is converted from the chaotic light comb state to the multi-soliton light comb state.

[0056] Then continue to tune the wavelength of the auxiliary laser, and observe through the spectrometer whether the pump laser generates a polarization orthogonal double soliton light comb in the red detuning region. If so, proceed to step S4; otherwise, change the wavelength of the tunable laser and return to step S1;

[0057] S4. Generate microwave signal

[0058] The optical microcavity outputs an orthogonal double soliton light comb, which is filtered out using an optical filter and then input into a photodetector to be converted into an electrical signal, thereby generating a microwave signal.

[0059] In order to illustrate the feasibility of the present invention in simultaneously generating two polarization orthogonal multiplexed Kerr light combs in a single optical microcavity, a specific embodiment is used for experimental verification.

[0060] First, the Q value and dispersion characteristics of the silicon nitride micro-ring cavity were tested. The test results are as follows: Figure 3 As shown: free spectrum width FSR = 100GHz, such as Figure 3 As shown in the first figure, the quality factor of the TE mode is Q = 2.3*10 6 ,like Figure 3 As shown in the second figure, the quality factor of the TM mode is Q = 7.9*10 5 ;like Figure 3 As shown in the first figure, the TE mode line width is 83.5MHz. Figure 3 As shown in the second figure, the TM mode line width is 241.5MHz. Figure 3 As shown in the third figure from the bottom, both modes have anomalous dispersion, and D2 / 2π of the TE mode is 0.869 MHz, and D2 / 2π of the TM mode is 0.530 MHz.

[0061] In this embodiment, the principle diagram of the orthogonal polarization double soliton optical comb generated by the on-chip silicon nitride optical microcavity is as follows: Figure 4 (a) is shown. The optical microcavity used in the embodiment is as follows Figure 4As shown in (b), two microlenses are used to focus the light spot of the lens fiber at the input and output ends and calibrate the optical path, so that the light can pass smoothly through the optical microcavity, thereby packaging it into a low-loss optical microcavity device. The pump laser comes from a tunable laser, and the central wavelength is set to 1602.8nm. After the pump laser passes through the modulator, two beams of light are filtered out by a filter as pump light for the TE mode and TM mode respectively. Two polarization controllers are used to adjust the polarization state of the two beams of light so that they are aligned with the TE mode and TM mode respectively. After the mode is aligned, the two beams of light are amplified to 32.5dBm and 32dBm respectively using an erbium-doped fiber amplifier. The two amplified beams of light are combined using a 25:75 optical coupler and input into one end of the optical microcavity. Among them, the TE pump light is 25% of the way, and the TM pump light is 75% of the way. In order to suppress the thermal nonlinearity of the micro-light, a tunable laser is also used as an auxiliary laser. The central wavelength is set to 1535nm. The polarization controller is used to align the polarization state of the auxiliary light with the TM mode. The power is then amplified to 32dBm by the erbium-doped fiber amplifier and input into the other end of the optical microcavity. When the auxiliary laser enters the cavity mode from the blue detuning region, the microcavity is heated and all the resonance peaks are red-shifted, so that the TE mode and TM mode pump lasers passively enter the resonance peak from the red detuning region. By properly setting the frequency detuning between the two pump lasers, the heat flow in the microcavity can be balanced, and the pump laser can smoothly scan the entire resonance peak area without obvious thermal effects. By independently tuning the pump detuning parameters of the TE mode and TM mode pump lasers, different soliton spectra can be generated in the microcavity, such as Figure 4 (c) shows a typical polarization orthogonal double soliton spectrum.

[0062] In order to illustrate that the two orthogonal light combs generated in the present invention have weak mutual influence, Figure 5 (i) to (vi) show the process of independent generation of polarization orthogonal double soliton optical combs. In the experiment, a TM mode soliton microcomb centered at 1550nm was first generated, such as Figure 5 Then the TE mode pump light is tuned into another TE mode resonance peak (about 1600nm), and the TE mode pump light passes through the low-noise primary light comb state from the blue detuning region to the red detuning region (see Figure 5 (ii)), secondary optical comb states (see Figure 5 (iii)), high noise chaotic state (see Figure 5 (iv)), multi-soliton states (see Figure 5 (v)), and finally reaches the single soliton state (see Figure 5(vi)). In this process, it can be found that the TM mode soliton comb is almost unaffected. Because the TE mode pump light and the TM mode pump light are polarized orthogonally, the nonlinear interaction between them through four-wave mixing is effectively suppressed, so the two modes of pump light can independently generate soliton combs without being affected by each other.

[0063] In order to better illustrate the technical effects of the present invention and how to generate photogenerated microwave signals based on a monolithic integrated optical microcavity orthogonal double soliton optical comb, some improvements are made on the basis of the above embodiments. In this embodiment, two independent tunable lasers are not used as pump laser sources. Instead, a tunable laser is used in conjunction with a modulator to modulate and generate two beams of light as TE mode pump light and TM mode pump light respectively. The TE mode and TM mode pump light sources come from the same light source, which can improve the coherence of the orthogonal polarization multiplexed soliton optical comb generated thereby. The photogenerated microwave signal device of the polarization orthogonal double soliton optical comb generated in this experiment is shown in the figure. Figure 1 As shown. In the experiment, a tunable laser is used as a pump laser source with a central wavelength of 193.866 THz. At the same time, the modulator is driven by a microwave source operating at 17.506 GHz, and the third-order modulation sideband is filtered out as TE mode pump light and TM mode pump light. After the two beams of light are aligned with the TE mode and TM mode respectively through the polarization controller, and then amplified by the erbium-doped fiber amplifier, they are combined into a beam of light by a coupler and input into the optical microcavity. The subsequent experimental steps are the same as the previous embodiment. The spectrum of the orthogonal polarization soliton comb generated in this experiment is shown in Figure 6 (a) shows that the optical signal is input into the photodetector and converted into an electrical signal, thereby generating a photogenerated microwave signal based on a single optical microcavity orthogonal double soliton optical comb. The use of a spectrum analyzer to beat the electrical signal shows that the gap between the two orthogonal modes is about 1.1 GHz, that is, the generated microwave signal is 1.1 GHz apart, as shown in Figure 1. Figure 6 (b) As shown. By observing the spectrum analyzer, it can be found that the line width of the microwave signal is about 4.4kHz, as shown in Figure 6 As shown in (c), it can be proved that the generated microwave signal has good coherence.

[0064] Although the above describes the illustrative specific embodiments of the present invention to facilitate the understanding of the present invention by those skilled in the art, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

Claims

1. A microwave generation method based on a monolithic integrated orthogonal double soliton optical comb, characterized in that: The following steps are involved: (1) Generate orthogonal dual pump lasers; (1.1) Use a modulator to modulate the sideband of the pump light; A tunable laser is used as a pump laser source to output continuous pump light with adjustable wavelength, which is then input to the modulator through an optical fiber. At the same time, a microwave source generates a microwave sinusoidal signal and inputs it to the modulator as a modulation signal. In the modulator, the modulator modulates the continuous pump light with the modulation signal to obtain multiple sideband pump light signals, and then the multiple sideband pump light signals are amplified by the amplifier and filtered by the bandpass filter, and the two sideband signals with the highest amplitude are retained; (1.2) Using a polarization controller to generate TE mode pump light and TM mode pump light; The polarization states of the two sideband signals are adjusted by using a polarization controller, so that the polarization state of one sideband signal is aligned with the TE mode of the optical microcavity, and the polarization state of the other sideband signal is aligned with the TM mode of the optical microcavity, thereby obtaining TE mode pump light and TM mode pump light; (1.3) Use a coupler to synthesize orthogonal dual pump lasers; After the TE mode pump light and the TM mode pump light are input into the erbium-doped fiber amplifier for optical power amplification, the two beams of light are combined into one laser beam by a coupler, and then input from port 1 of the first circulator and output from port 2 to the optical microcavity; at the same time, port 3 of the first circulator is connected to a power meter to monitor the optical power of the auxiliary laser input into the optical microcavity; (2) Produce auxiliary laser; In addition, a tunable laser is selected as an auxiliary laser source to output auxiliary laser, and then a polarization controller is used to adjust the polarization state of the auxiliary laser so that the polarization state of the auxiliary laser is aligned with the TE mode or TM mode of the optical microcavity. Then, an erbium-doped fiber amplifier is used to amplify the power and input it through port 1 of the second circulator and output it to the optical microcavity through port 2. At the same time, a spectrometer and an optical filter are connected to port 3 of the second circulator. (3) Generate polarization orthogonal double soliton optical comb; (3.1) Using the auxiliary laser heating effect to make the pump laser enter the microcavity resonance peak; The pump laser and the auxiliary laser are input into the optical microcavity from different directions respectively, and the power value of the power meter is observed. When the power value reaches the threshold, the auxiliary laser wavelength is tuned to enter the resonance peak of the optical microcavity. At this time, due to the thermal nonlinear effect of the optical microcavity, the resonance peak will move toward the long wavelength direction, so that the pump laser passively enters the resonance peak of the optical microcavity and is in the blue detuning region of the resonance peak. (3.2) Tuning the microcavity resonance peak wavelength to generate polarization orthogonal double soliton optical comb; The wavelength of the auxiliary laser is tuned again. Due to the thermal nonlinear effect of the optical microcavity, the resonance peak moves toward the short wavelength direction, so that the relative resonance peak position of the pump laser moves toward the long wavelength direction. The spectrometer is used to observe that the pump laser smoothly transitions from the blue detuning region to the red detuning region. Then, the wavelength of the auxiliary laser is continued to be tuned, and the spectrometer is used to observe whether the pump laser generates a polarization orthogonal double soliton light comb in the red detuning region. If so, proceed to step (4); otherwise, change the wavelength of the tunable laser and return to step (1). (4) Generate microwave signals The optical microcavity outputs an orthogonal double soliton light comb, which is filtered out using an optical filter and then input into a photodetector to be converted into an electrical signal, thereby generating a microwave signal.

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