An optical millimeter wave system and method based on optical frequency comb stabilized interferometric structure

Abstract

The application belongs to the technical field of microwave photonics, and relates to an optical millimeter wave system and method based on an optical frequency comb stable interference structure. The application provides an optical millimeter wave system based on an optical frequency comb stable interference structure, which comprises an optical frequency comb module for outputting an optical frequency comb signal; an interference module for branching, delaying and combining input light signals; a phase detection and link locking module for inputting the optical frequency comb signal to the interference module and generating a control signal; a first laser and a second laser for outputting two beams of laser light with different wavelengths; and a laser frequency stabilization module for locking the first laser and the second laser to the same stable fiber link delay, thereby obtaining frequency-stable optical millimeter waves. The system uses two lasers that are locked to the same stable fiber link, uses fiber delay as a reference benchmark, and makes frequency tuning not limited to an external reference frequency source or optical frequency comb parameters, so as to simultaneously achieve a small tuning step and a large tuning range.

Description

Technical Field

[0001] This invention relates to the field of microwave photonics technology, and in particular to a photogenerated millimeter-wave system and method based on an optical frequency comb stable interference structure. Background Technology

[0002] Microwave photonics is an interdisciplinary technology that utilizes photonic methods to generate, distribute, control, and process microwave signals. It is widely used to address current limitations in the microwave field. Optically generated millimeter-wave technology is an important branch of this field. It generates millimeter-wave signals optically, effectively overcoming the problems of sacrificing phase noise and frequency stability in generating high-frequency millimeter-wave signals using traditional electrical methods. This provides a feasible path to overcome bottlenecks in electrical technology.

[0003] Currently, common methods for optically generated millimeter-wave signals mainly include the photoelectric oscillator method, external modulation method, and optical heterodyne method. Among these, the photoelectric oscillator method can generate millimeter-wave signals with low phase noise. The resonant frequency interval is determined by the delay of the fiber delay line, and specific mode selection is achieved through an electrical bandpass filter. However, the frequency of the output signal is limited by the bandwidth of the modulator and the center frequency of the filter. The external modulation method uses an electro-optic modulator to generate harmonic sidebands, which are then retained by an optical filter or nonlinear device. The resulting microwave signal is then obtained through photoelectric conversion. The phase noise level of the generated millimeter-wave signal is limited by the modulator's drive signal, and the generation of high-frequency millimeter-wave signals depends on the number of modulators, increasing system complexity. The optical heterodyne method uses two lasers of different wavelengths to beat the signal through a photodetector to obtain a millimeter-wave signal. Flexible frequency tuning can be achieved by adjusting the frequency interval of the lasers, and generating high-frequency signals does not increase system complexity. However, good coherence between the two lasers is required to achieve stable millimeter-wave frequencies. In summary, the optical heterodyne method for generating millimeter-wave signals has certain advantages in terms of tunability and high-frequency signal generation, and this method has attracted widespread attention.

[0004] To address the issue of frequency stability in optically generated millimeter-wave systems, current solutions primarily rely on phase-locked loop (PLL) technology. Existing technology provides an optically generated millimeter-wave system that mixes the laser's difference frequency signal with a frequency source signal, down-converts it to obtain a low-frequency intermediate frequency (IF) signal, compares this IF signal with a local oscillator reference signal, and uses a PLL structure to feedback-control one of the lasers, locking the laser's difference frequency to the frequency source signal, thereby achieving millimeter-wave frequency stability. However, its wide-range frequency tuning capability depends on the adjustable range of the frequency source; therefore, the overall tuning bandwidth is limited by the performance of the frequency source.

[0005] Existing technology provides another optically generated millimeter-wave system. This system achieves coherence in its output signal by injecting and locking two distributed Bragg reflector (DBR) lasers as slave lasers onto two teeth of the same optical frequency comb. By adjusting the injection current of the DBR lasers, their free oscillation frequency can be changed, allowing them to be re-injected and locked onto other optical comb teeth, thereby achieving difference frequency tuning between the two slave lasers. However, the generated millimeter-wave frequency is determined by the selected comb tooth spacing; therefore, the frequency tuning step and tuning range are limited by the repetition frequency of the optical frequency comb and the available comb tooth order, respectively.

[0006] Existing technology also provides an optically generated millimeter-wave system that uses a phase-locked loop (PLL) to lock two lasers to different sidebands of an optical frequency comb, thereby obtaining a coherent difference frequency output. The millimeter-wave frequency is determined by the product of the sideband order difference and the modulation frequency, while the PLL reference signal only provides a small range of bias adjustment. Therefore, although continuous fine-tuning is possible, its wide-range tuning capability is still limited by the available comb order.

[0007] This invention aims to solve the coherence problem of lasers based on optical heterodyne methods, achieve long-term stability of optically generated millimeter waves, and improve the tuning capability limited by the comb teeth. Summary of the Invention

[0008] Existing optically generated millimeter-wave systems generally use a frequency reference to lock onto the laser. The tunability of the reference frequency source or the repetition frequency of the optical frequency comb directly affects the frequency tunability step size of the optically generated millimeter-wave. In addition, the available frequency of the reference frequency source and the available comb teeth of the optical frequency comb determine the frequency tuning range of the optically generated millimeter-wave, thus limiting its tunability.

[0009] The purpose of this invention is to address the limited tunability of existing optical heterodyne methods by proposing a light-generated millimeter-wave system based on a stable optical frequency comb interference structure. The system includes an optical frequency comb module for outputting an optical frequency comb signal; an interference module for splitting, delaying, and combining the input optical signal; a phase detection and link locking module for inputting the optical frequency comb signal to the interference module and generating a control signal; a first laser and a second laser for outputting two laser beams with different wavelengths; and a laser frequency stabilization module that locks both the first and second lasers to the same stable optical fiber link delay, thereby obtaining frequency-stable light-generated millimeter waves. This system utilizes the fact that both lasers are locked to the same stable optical fiber link, using the fiber delay as a reference, so that frequency tuning is not limited by external reference frequency sources or optical frequency comb parameters, thus simultaneously achieving a small tuning step size and a large tuning range.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure, comprising: Optical frequency comb module, used to output optical frequency comb signal; The interferometric module includes a reference arm, a measurement arm, a first optical coupler, and a second optical coupler. The first optical coupler splits the input optical signal into two paths, which enter the reference arm and the measurement arm respectively. The second optical coupler combines the optical signals output from the reference arm and the measurement arm. The measurement arm includes a delay compensation unit for compensating for the optical link delay of the measurement arm. The phase detection and link locking module is used to input the optical frequency comb signal to the interferometer module, and use the interferometer signal output by the interferometer module to detect the link delay jitter between the measurement arm and the reference arm. Based on the detection result, a first control signal is generated to control the delay compensation module so that the link delay of the interferometer module remains stable. The first laser and the second laser are used to output two laser beams with different wavelengths. A portion of the combined laser beam is used as an optically generated millimeter wave output. The laser frequency stabilization module is used to inject the laser outputs from the first laser and the second laser into the interference module whose link delay has been stabilized, respectively. The output signal of the interference module is used to detect the frequency drift of the first laser and the second laser, respectively. Based on the detection results, a third control signal and a second control signal are generated. The third control signal is used to control the output frequency of the first laser, and the second control signal is used to control the output frequency of the second laser, so that the first laser and the second laser are locked to the same stable fiber optic link delay, thereby obtaining a frequency-stable optically generated millimeter wave.

[0011] As one possible implementation, the delay compensation unit includes: The first delay compensation unit adjusts the link delay of the measuring arm on a first scale. The second delay compensation unit, cascaded with the first delay compensation unit, is used to adjust the link delay of the measuring arm on a second scale; wherein the first scale is greater than the second scale.

[0012] As one possible implementation, the first delay compensation unit is a motor delay line or a temperature-controlled fiber optic delay line; the second delay compensation unit is a piezoelectric ceramic tensioner.

[0013] As one possible implementation, the phase detection and link locking module includes: The first optical filter is disposed between the optical frequency comb module and the first optical coupler, and is used to extract the initial high-order comb tooth pairs of positive and negative order from the optical frequency comb signal as a probe signal for detecting link delay jitter. The second optical filter, located after the second optical coupler, is used to filter out the interference signals corresponding to the probe signals respectively; The first photodetector and the second photodetector are disposed after the second optical filter and are used to receive the interference signal output by the interference module and convert it into a first electrical signal and a second electrical signal that reflect the link delay, respectively. The first phase-locked loop is used to receive the first electrical signal and the second electrical signal, perform phase comparison to obtain an error signal, and generate a first control signal based on the error signal.

[0014] As one possible implementation, the laser frequency stabilization module includes: The third optical coupler is used to combine the output laser beams of the first laser and the second laser, and then divide them into two parts with equal power. One part is injected into the interference module, and the other part is used to generate optical millimeter waves. The second optical filter, located after the second optical coupler, is also used to filter out the interference signals carrying the frequency information of the first and second lasers respectively; the phase detection and link locking module and the laser frequency stabilization module share the second optical filter; The third photodetector is used to receive the interference signal carrying the frequency information of the second laser after being filtered out by the second optical filter, and convert it into a third electrical signal; The fourth photodetector is used to receive the interference signal carrying the frequency information of the first laser after being filtered out by the second optical filter, and convert it into a fourth electrical signal; Radio frequency signal generator, used to provide a reference signal; The second phase-locked loop is used to compare the phase of the third electrical signal with the reference signal provided by the radio frequency signal generator, and generate a second control signal based on the comparison result to control the second laser. The third phase-locked loop is used to compare the phase of the fourth electrical signal with the reference signal provided by the radio frequency signal generator, and generate a third control signal based on the comparison result to control the first laser.

[0015] In a second aspect, the present invention provides a method for generating millimeter waves based on an optical frequency comb-stabilized interference structure, applied to the optically generated millimeter wave system based on the optical frequency comb-stabilized interference structure described in the first aspect, comprising the following steps: S1. Generate an optical frequency comb signal and inject it into the interference optical path. By detecting the output signals of the reference arm and the measurement arm in the interference optical path, obtain the link delay jitter information. S2. Based on the link delay jitter information, perform real-time feedback compensation on the optical link delay of the measurement arm to keep the link delay of the interference optical path stable; S3. Inject the lasers output from the first laser and the second laser into the interference optical path whose link delay has been stabilized, and obtain the frequency drift information of the first laser and the second laser by detecting the output signal of the interference optical path; S4. Based on the frequency drift information of the first laser and the second laser, the output frequencies of the first laser and the second laser are controlled in real time to lock them both to the same stable fiber optic link delay. S5. Combine the output lasers of the first and second lasers after frequency locking, and obtain a frequency-stable millimeter-wave signal through photoelectric conversion.

[0016] As one possible implementation, obtaining link delay jitter information in S1 specifically includes: extracting high-order comb teeth of positive and negative order from the optical frequency comb signal as probe signals and injecting them into the interference optical path; and performing photoelectric conversion and phase comparison on the two signals output from the interference optical path to obtain an error signal reflecting the link delay jitter.

[0017] As one possible implementation, S2 performs real-time feedback compensation for the optical link delay of the measurement arm, specifically including: The link delay of the measuring arm is adjusted by the first delay compensation unit; The link delay of the measuring arm is adjusted by the second delay compensation unit; The first delay compensation unit and the second delay compensation unit are cascaded, and the adjustment scale of the first delay compensation unit is larger than that of the second delay compensation unit.

[0018] As one possible implementation, the frequency tuning step size of the first laser and the second laser is smaller than the repetition frequency of the optical frequency comb signal, and the frequency tuning range is not limited by the available comb tooth order of the optical frequency comb signal. Frequency tuning is achieved by adjusting the initial wavelength of the first laser and the second laser.

[0019] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in the second aspect.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure provided by this invention employs a high-frequency probe to sense link delay jitter. By using the higher-order comb teeth of the optical frequency comb as the probe signal, the conversion gain from link delay jitter to phase change is improved, thereby achieving high-precision sensing of link delay jitter.

[0021] 2. The optically generated millimeter-wave system based on a stable interference structure of optical frequency comb provided by the present invention adopts a cascaded compensation structure of piezoelectric ceramic stretcher and motor delay line to achieve large-range, high-precision real-time compensation of link delay.

[0022] 3. The optically generated millimeter-wave system based on a stable optical frequency comb interference structure provided by this invention locks both lasers onto the same stable optical fiber link, improving their coherence and thus ensuring the long-term stability of the optically generated millimeter waves.

[0023] 4. The optically generated millimeter-wave system based on a stable interference structure using an optical frequency comb, provided by this invention, employs fiber delay as a reference, and frequency tuning is no longer limited by the reference frequency source and the optical frequency comb. This allows for a smaller tuning step size and a larger tuning range. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 A schematic diagram of an optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure provided in an embodiment of the present invention; Figure 2 The frequency tuning spectrum of the optically generated millimeter-wave system based on the optical frequency comb stable interference structure provided in Embodiment 1 of the present invention is shown. Figure 3 The image shows the frequency stability results of the 22.5 GHz optically generated millimeter wave generated by the optically generated millimeter wave system based on the optical frequency comb stable interference structure provided in Embodiment 1 of the present invention. Figure 4 The image shows the frequency stability results of a 1THz optically generated millimeter wave generated by the optically generated millimeter wave system based on an optical frequency comb stable interference structure, as provided in Embodiment 2 of the present invention. Detailed Implementation

[0025] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0026] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0027] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c" can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0028] The purpose of this invention is to address the limited tunability of existing optical heterodyne methods by proposing a light-generated millimeter-wave system based on a stable optical frequency comb interference structure. The system includes an optical frequency comb module for outputting an optical frequency comb signal; an interference module for splitting, delaying, and combining the input optical signal; a phase detection and link locking module for inputting the optical frequency comb signal to the interference module and generating a control signal; a first laser and a second laser for outputting two laser beams with different wavelengths; and a laser frequency stabilization module that locks both the first and second lasers to the same stable optical fiber link delay, thereby obtaining a frequency-stable light-generated millimeter wave. This system utilizes the fact that both lasers are locked to the same stable optical fiber link, using the fiber delay as a reference, so that frequency tuning is not limited by external reference frequency sources or optical frequency comb parameters, thus simultaneously achieving a small tuning step size and a large tuning range.

[0029] In a first aspect, embodiments of the present invention provide an optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure, comprising: Optical frequency comb module, used to output optical frequency comb signal; The interferometric module includes a reference arm, a measurement arm, a first optical coupler, and a second optical coupler. The first optical coupler splits the input optical signal into two paths, which enter the reference arm and the measurement arm respectively. The second optical coupler combines the optical signals output from the reference arm and the measurement arm. The measurement arm includes a delay compensation unit for compensating for the optical link delay of the measurement arm. The phase detection and link locking module is used to input the optical frequency comb signal to the interferometer module, and use the interferometer signal output by the interferometer module to detect the link delay jitter between the measurement arm and the reference arm. Based on the detection result, a first control signal is generated to control the delay compensation module so that the link delay of the interferometer module remains stable. The first laser and the second laser are used to output two laser beams with different wavelengths. A portion of the combined laser beam is used as an optically generated millimeter wave output. The laser frequency stabilization module is used to inject the laser outputs from the first laser and the second laser into the interference module whose link delay has been stabilized, respectively. The output signal of the interference module is used to detect the frequency drift of the first laser and the second laser, respectively. Based on the detection results, a third control signal and a second control signal are generated. The third control signal is used to control the output frequency of the first laser, and the second control signal is used to control the output frequency of the second laser, so that the first laser and the second laser are locked to the same stable fiber optic link delay, thereby obtaining a frequency-stable optically generated millimeter wave.

[0030] Among them, an optical frequency comb is a spectrum that presents an equally spaced, comb-like distribution in the frequency domain, resembling a "frequency ruler," and can be used to accurately measure and control the frequency of light. It consists of a series of equally spaced frequency components ("comb teeth"), and its core parameters include the repetition frequency and the carrier envelope offset frequency, which can be realized through technologies such as femtosecond mode-locked lasers, electro-optic modulation, or micro-resonant cavities.

[0031] An optical coupler is a passive optical device used to split and combine optical signals between two or more optical fibers, thereby achieving optical power distribution and coupling. It is one of the most fundamental and commonly used devices in fields such as optical fiber communication, optical fiber sensing, and optical signal processing.

[0032] Specifically, this invention provides an optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure. The system composition is described in [reference needed]. Figure 1 The system includes an optical frequency comb module, an interference module, a phase detection and link locking module, a first laser and a second laser, and a laser frequency stabilization module. It is a highly stable optical millimeter wave generation system.

[0033] Among them, the optical frequency comb module uses the optical frequency comb as a "frequency ruler" and utilizes the equal spacing and high coherence "comb tooth characteristics" of the optical frequency comb to provide a relative frequency reference for the entire system, ensuring the accuracy of subsequent link stability.

[0034] The interferometer module includes a reference arm, a measuring arm, a first optical coupler, and a second optical coupler.

[0035] The reference arm serves as the absolute phase reference in the system, and its optical path must remain constant to provide a reference phase for the interference signal and eliminate system drift. The measuring arm carries the physical change to be measured, and its optical path change is converted into a phase change of the signal for sensing or feedback control.

[0036] The first optical coupler is used to split the input optical signal into two paths, with 30% of the optical signal power entering the reference arm and the other 70% of the optical signal power entering the measurement arm, to ensure that the power of the optical signals entering the second optical coupler is equivalent.

[0037] The measuring arm also includes a delay compensation unit to compensate for the optical link delay of the measuring arm, thereby dynamically adjusting the optical path of the measuring arm. After the input light is output from the reference arm and the measuring arm, it enters the second optical coupler for beam combining.

[0038] As one possible implementation, the delay compensation unit includes: The first delay compensation unit adjusts the link delay of the measuring arm on a first scale. The second delay compensation unit, cascaded with the first delay compensation unit, is used to adjust the link delay of the measuring arm on a second scale; wherein the first scale is greater than the second scale.

[0039] In this system, the delay compensation unit adopts a two-level cascaded structure and achieves wide-range, high-precision delay stability control through a "coarse adjustment + fine adjustment" collaborative mechanism, effectively coping with multi-scale environmental disturbances.

[0040] Among them, the first delay compensation unit performs the first scale adjustment, namely large-scale coarse adjustment, to cope with low-frequency, large-amplitude optical path changes, and adjusts the scale from micrometer level to millimeter level or even centimeter level displacement, which corresponds to nanosecond level delay at the maximum. The second delay compensation unit performs second-scale control, namely small-scale fine-tuning, to cope with high-frequency, minute phase jitter. The adjustment scale is the optical path change from nanometer to micrometer, corresponding to femtosecond to picosecond delay.

[0041] The two delay compensation units use a range coordination control strategy. When the rapid compensation of the second delay compensation unit approaches the compensation threshold, the delay adjustment of the first delay compensation unit is introduced, so that the rapid compensation returns to the working range, realizing delay jitter compensation from the femtosecond level to the nanosecond level.

[0042] As one possible implementation, the first delay compensation unit is a motor delay line or a temperature-controlled fiber optic delay line; the second delay compensation unit is a piezoelectric ceramic tensioner.

[0043] Among them, motor delay lines refer to devices that use stepper motors to drive mirrors and change the optical path through mechanical displacement, with an adjustment range in the nanosecond range. For example, COSC's VDL-R-MOS-1000-15-PM-FA model motor delay line can provide a delay of up to 1 ns.

[0044] Temperature-controlled fiber optic delay lines are devices that tightly wind long optical fibers into a loop, precisely control the fiber temperature using a semiconductor cooling chip, and utilize the thermal expansion and contraction effect to change the fiber length and refractive index to achieve continuously adjustable delay, with an adjustment range in the nanosecond range.

[0045] A piezoelectric ceramic stretcher is a device that uses the piezoelectric effect to generate nanoscale deformation when a voltage is applied to a ceramic material, directly stretching or compressing the optical fiber wound on it to achieve micron to nanometer level adjustment of the optical path. The response frequency is approximately DC to 10kHz, the adjustment range is picosecond to femtosecond, and the delay conversion coefficient is approximately 0.02-0.04ps / V.

[0046] The delay compensation unit composed of the above-mentioned components and the temperature control / motor unit can lock the optical path within ±500ps, so that the piezoelectric ceramic tensioner only needs to compensate for jitter within ±0.2ps, thereby greatly reducing the driving voltage requirement of the piezoelectric ceramic tensioner and expanding the compensation range.

[0047] The technical solution of this invention constitutes a cascaded architecture of "large-range slow response coarse adjustment + small-range fast response fine adjustment", which is a path to realize a highly stable optically generated millimeter-wave system.

[0048] The interferometer module is the core sensing and feedback front end for achieving phase locking. It is essentially a high-precision optical path difference detector and undertakes the "sensing" function in the closed-loop control of the system.

[0049] The phase detection and link locking module is the core hub for achieving phase closed-loop control. It transforms the weak phase error signal output by the interference module into precise control commands, driving the motor delay line and piezoelectric ceramic tensioner to work together, ultimately achieving nanosecond-level delay stabilization and femtosecond-level delay control.

[0050] As one possible implementation, the phase detection and link locking module includes: The first optical filter is disposed between the optical frequency comb module and the first optical coupler, and is used to extract the initial high-order comb tooth pairs of positive and negative order from the optical frequency comb signal as a probe signal for detecting link delay jitter. The second optical filter, located after the second optical coupler, is used to filter out the interference signals corresponding to the probe signals respectively; The first photodetector and the second photodetector are disposed after the second optical filter and are used to receive the interference signal output by the interference module and convert it into a first electrical signal and a second electrical signal that reflect the link delay, respectively. The first phase-locked loop is used to receive the first electrical signal and the second electrical signal, perform phase comparison to obtain an error signal, and generate a first control signal based on the error signal.

[0051] An optical filter is a frequency-selective optical device primarily used to select specific frequencies from numerous frequency components of an optical signal and suppress the passage of other frequency components. Its core functions include channel separation, noise filtering, and gain equalization in optical communication systems. As an example, in this embodiment of the invention, the first optical filter has two 200GHz filter passbands, capable of transmitting optical signals with frequencies within these passbands. The optical frequency comb signal output by the aforementioned optical frequency comb output module, after being filtered by the first optical filter, outputs two 200GHz passband optical signals centered at positive and negative 8th order comb teeth.

[0052] The initial higher-order comb pair refers to the selected higher-order comb pair and several surrounding comb teeth obtained after coarse filtering by the first filter.

[0053] Among them, a phase-locked loop (PLL) is a negative feedback control system that uses an actuator to adjust the phase so that two comparison signals are kept in phase synchronization.

[0054] This module contains a typical feedback control circuit that uses an externally input reference signal to control the frequency and phase of the internal oscillation signal, achieving automatic tracking of the output signal frequency to the input signal frequency. It is generally used in closed-loop tracking circuits. In this embodiment, the phase-locked loop compares the phase of the beat frequency signal to obtain an error signal, amplifies and integrates the error signal to generate a feedback control signal, which is then used to regulate the delay compensation unit.

[0055] The technical solution of this invention uses positive and negative order high-order comb teeth pairs as probe signals, combined with differential reception by dual photodetectors, to form a high-sensitivity, common-mode interference-resistant optical frequency comb phase detection architecture. Its core innovation lies in transforming the comb tooth symmetry of the optical frequency comb into differential phase detection capability, achieving high-precision sensing of link delay jitter.

[0056] The above section describes the link delay stabilization part of the optically generated millimeter-wave system provided in this embodiment of the invention. This part is the core execution unit for achieving nanosecond-level delay stabilization. Essentially, it uses dual actuators for collaborative feedback control to compensate for delay jitter caused by environmental disturbances in real time to the tens of femtosecond level. This part uses the positive and negative order comb pairs extracted by the first optical filter as probe signals. Relying on the error control signal generated by the first phase-locked loop, it drives the motor delay line and the piezoelectric ceramic tensioner to form a "coarse adjustment-fine adjustment" cascaded structure, completing the full closed-loop stabilization from sensing to execution.

[0057] In addition, this system also has a light-generated millimeter-wave section, which consists of a first laser, a second laser, and a laser frequency stabilization module.

[0058] The system comprises a first laser and a second laser, each outputting a laser beam with a different wavelength. A portion of the combined laser beam is then used as the output of a light-generated millimeter wave. Both lasers are locked onto the same stable fiber optic link and have a certain frequency interval. In this embodiment of the light-generated millimeter wave system, after passing through a phase-locked loop, the laser beam is received at the output point using a high-speed photodetector to obtain the millimeter wave signal.

[0059] Among them, the laser frequency stabilization module is the core of ensuring the long-term coherence of the system. Its function is to lock the laser output frequency to the same stable link delay, thereby achieving long-term frequency stability.

[0060] As one possible implementation, the laser frequency stabilization module includes: The third optical coupler is used to combine the output laser beams of the first laser and the second laser, and then divide them into two parts with equal power. One part is injected into the interference module, and the other part is used to generate optical millimeter waves. The second optical filter, located after the second optical coupler, is also used to filter out the interference signals carrying the frequency information of the first and second lasers respectively; the phase detection and link locking module and the laser frequency stabilization module share the second optical filter; The third photodetector is used to receive the interference signal carrying the frequency information of the second laser after being filtered out by the second optical filter, and convert it into a third electrical signal; The fourth photodetector is used to receive the interference signal carrying the frequency information of the first laser after being filtered out by the second optical filter, and convert it into a fourth electrical signal; Radio frequency signal generator, used to provide a reference signal; The second phase-locked loop is used to compare the phase of the third electrical signal with the reference signal provided by the radio frequency signal generator, and generate a second control signal based on the comparison result to control the second laser. The third phase-locked loop is used to compare the phase of the fourth electrical signal with the reference signal provided by the radio frequency signal generator, and generate a third control signal based on the comparison result to control the first laser.

[0061] The laser frequency stabilization module provided in this embodiment of the invention uses a stable optical frequency comb interference structure as a relative frequency reference to achieve phase synchronization of the first and second lasers. Its core lies in using a stable fiber optic link delay as a frequency discriminator to convert the frequency deviation between the two lasers into a detectable phase signal, which is then controlled by a dual phase-locked loop.

[0062] The third optical coupler combines the output laser beams from the first and second lasers, then splits them into two equal-power components. One component is combined with the optical frequency comb signal via the first optical coupler and injected into the interference module; the other component is used to generate optically generated millimeter waves. The second optical filter selectively extracts the frequency components corresponding to the two sets of lasers; The third photodetector converts the optical frequency domain phase error into the radio frequency domain phase error, obtaining a beat frequency signal carrying the laser frequency deviation, which is used as the input of the second phase-locked loop; similarly, the fourth photodetector provides a feedback source for the third phase-locked loop. A radio frequency (RF) signal generator is an electronic testing device primarily used to generate RF signals with high spectral purity, stable frequency, and amplitude; in this embodiment of the invention, see [reference needed]. Figure 1 The optically generated millimeter-wave system shown uses the signal output from the atomic clock as a reference signal to synchronously transmit radio frequency signals. Then, the radio frequency signals are compared with the beat frequency signal that is phase-compared with them as needed to achieve frequency adjustment.

[0063] The second phase-locked loop is used to adjust the frequency of the second laser in a closed loop to synchronize it with the reference signal and suppress its phase noise; the third phase-locked loop is also used to lock the first laser in a closed loop to achieve independent frequency stabilization of the two lasers.

[0064] Specifically, see Figure 1 As shown, the optical frequency signals output by the first laser and the second laser are combined by the third optical coupler and then divided into two optical signals of equal power. One part is used as optical output and generates a millimeter-wave signal through photoelectric conversion and other methods. The other part is combined with the optical frequency comb signal by the first optical coupler.

[0065] The combined signal is also split into two optical signals: a 30% power signal enters the reference arm, and a 70% power signal enters the measurement arm. The output signal, after passing through both paths, is combined again at the second optical coupler and then input to the second optical filter.

[0066] The third and fourth channels of the second optical filter filter extract the optical frequency signals corresponding to the second and first lasers, respectively, which are then received by the third and fourth photodetectors. After photoelectric conversion, two beat frequency signals are obtained. These two beat frequency signals have the same frequency but different phases, and their phase changes are related to the corresponding laser frequency changes.

[0067] The beat frequency signal output from the third photodetector is amplified by the third power amplifier and then input into the second phase-locked loop (PLL) along with the reference signal output from the radio frequency (RF) signal generator. The reference signal is used to extract the phase term of the beat frequency signal, which reflects the frequency variation of the second laser. The second PLL outputs a control signal to control the wavelength of the second laser.

[0068] Similarly, the beat frequency signal output from the fourth photodetector is amplified by the fourth power amplifier and then input into the third phase-locked loop (PLL) along with the reference signal output from the RF signal generator. The third PLL outputs a control signal to control the wavelength of the first laser.

[0069] Ultimately, both the first and second lasers are locked to the same stable fiber optic link delay, achieving relative frequency stability and maintaining coherence.

[0070] Therefore, the millimeter-wave signal obtained after photoelectric conversion of the light output has a stable frequency.

[0071] The laser frequency stabilization module, together with the aforementioned modules, forms a complete optically generated millimeter-wave system. Its phase detection and link delay stabilization module suppresses delay jitter and ensures link delay stability; its laser frequency stabilization module locks the frequencies of the two lasers, enabling the system to have two relatively stable laser outputs, providing a foundation for stable millimeter-wave generation.

[0072] In summary, the embodiments of the present invention construct a frequency stabilization system with an optical fiber link as the relative frequency reference, providing a new technical path for realizing optically generated millimeter waves.

[0073] In a second aspect, the present invention provides a method for generating millimeter waves based on an optical frequency comb-stabilized interference structure, applied to the optically generated millimeter wave system based on the optical frequency comb-stabilized interference structure described in the first aspect, comprising the following steps: S1. Generate an optical frequency comb signal and inject it into the interference optical path. By detecting the output signals of the reference arm and the measurement arm in the interference optical path, obtain the link delay jitter information. S2. Based on the link delay jitter information, perform real-time feedback compensation on the optical link delay of the measurement arm to keep the link delay of the interference optical path stable; S3. Inject the lasers output from the first laser and the second laser into the interference optical path whose link delay has been stabilized, and obtain the frequency drift information of the first laser and the second laser by detecting the output signal of the interference optical path; S4. Based on the frequency drift information of the first laser and the second laser, the output frequencies of the first laser and the second laser are controlled in real time to lock them both to the same stable fiber optic link delay. S5. Combine the output lasers of the first and second lasers after frequency locking, and obtain a frequency-stable millimeter-wave signal through photoelectric conversion.

[0074] This invention provides a method for generating optical millimeter waves. Based on the optical millimeter wave system with a stable interference structure based on an optical frequency comb as described in the first aspect, it achieves high-stability millimeter wave output through a five-step closed loop. This method reduces the impact of environmental disturbances on fiber optic link delay to the femtosecond level through system-level closed-loop control of "link phase stabilization → laser frequency stabilization → difference frequency generation", ultimately achieving long-term frequency-stable millimeter wave signal output. Its core lies in using the stable fiber optic link delay as a common reference benchmark, thereby achieving relative locking of the two lasers.

[0075] The specific workflow for generating millimeter waves using the optically generated millimeter wave system based on the optical frequency comb stable interference structure described in the first aspect, as provided by the embodiments of the present invention, is as follows: (1) Link delay stability part The optical frequency comb signal output by the optical frequency comb output module is filtered by the first optical filter and outputs two 200GHz passband optical signals with positive and negative 8th order comb teeth as the center frequency.

[0076] The signal is split into two parts after passing through the first optical coupler. One part is directly input to the second optical coupler via the reference arm, and the other part enters the measurement arm. In the measuring arm, the optical signal is frequency-shifted by an acousto-optic frequency shifter and delayed by an optical fiber before being input into a second optical coupler for beam combining.

[0077] The output signal of the second optical coupler enters the second optical filter, and the optical frequency signals of the positive and negative 8th order combs are output through two channels respectively.

[0078] The first and second photodetectors receive the optical frequency signals and perform photoelectric conversion to obtain two beat frequency signals.

[0079] Two beat frequency signals have the same frequency. After being amplified by the first power amplifier and the second power amplifier respectively, they are input together into the first phase-locked loop. An error signal is obtained by comparing the phases of the two beat frequency signals. The error signal is then amplified and integrated to generate a feedback control signal. The generated feedback control signal regulates the delay compensation module.

[0080] This control is based on the piezoelectric effect. Under the voltage drive of the feedback control signal, the piezoelectric ceramic expands or contracts in volume, causing the optical fiber wound on it to stretch and contract, thus achieving precise and rapid control of optical fiber delay. According to the set voltage threshold, when the voltage of the feedback control signal exceeds the threshold, the microcontroller / host computer sends a command to control the position of the reflector in the motor delay line through the motor driver, so as to achieve large-range link delay compensation.

[0081] In the delay compensation module, the piezoelectric ceramic tensioner performs high-precision and fast delay compensation, while the motor delay line is responsible for a wide range of delay compensation. The combination of the two achieves real-time stability of fiber optic link delay.

[0082] (2) Photogenerated millimeter wave component The optical frequency signals output by the first and second lasers are combined by the third optical coupler and then split into two parts. One part is used as optical output and generates a millimeter-wave signal through photoelectric conversion and other methods. The other part is combined with the optical frequency comb signal by the first optical coupler.

[0083] The combined signal is also divided into two parts, which are input to the measuring arm and the reference arm respectively. The output signal after the optical signal passes through two paths is combined at the second optical coupler and then input to the second optical filter.

[0084] The third and fourth channels of the optical filter filter out the optical frequency signals corresponding to the second laser and the first laser, respectively, and these signals are received by the third and fourth photodetectors. After photoelectric conversion, two beat frequency signals are obtained.

[0085] The beat frequency signal output from the third photodetector is amplified by the third power amplifier and then input into the second phase-locked loop (PLL) along with the reference signal output from the radio frequency (RF) signal generator. The reference signal is used to extract the phase term of the beat frequency signal, which reflects the frequency variation of the second laser. The second PLL outputs a control signal to control the wavelength of the second laser.

[0086] Similarly, the beat frequency signal output from the fourth photodetector is amplified by the fourth power amplifier and then input into the third phase-locked loop (PLL) along with the reference signal output from the RF signal generator. The third PLL outputs a control signal to control the wavelength of the first laser.

[0087] Ultimately, both the first and second lasers are locked to the same stable fiber optic link delay, achieving relative frequency stability and maintaining coherence. Therefore, the millimeter-wave signal obtained after photoelectric conversion of the optical output has a stable frequency.

[0088] As one possible implementation, obtaining link delay jitter information in S1 specifically includes: extracting high-order comb teeth of positive and negative order from the optical frequency comb signal as probe signals and injecting them into the interference optical path; and performing photoelectric conversion and phase comparison on the two signals output from the interference optical path to obtain an error signal reflecting the link delay jitter.

[0089] As an example, extracting positive and negative order high-order comb tooth pairs (such as ±8 orders) from an optical frequency comb can form a pair of common-mode suppression differential probes, with each pair of comb tooth frequencies satisfying: , , in, The carrier frequency of the optical frequency comb; is the repetition frequency of the optical frequency comb; n is the order of the selected comb tooth pair.

[0090] The phase comparison results of the two electrical signals are as follows: , in, This frequency does not change with the carrier drift of the optical frequency comb, but is only related to the repetition frequency of the optical frequency comb. This phase reflects that its phase change is only related to the delay change, that is: , in, This refers to fiber optic link delay jitter.

[0091] The jitter is mainly caused by factors such as changes in the external environment's temperature. Therefore, the difference frequency of the higher-order comb pair is used to amplify this delay jitter, achieving high-precision detection.

[0092] The technical solution of this invention provides a physical mechanism and implementation method for obtaining link delay jitter information, the core of which lies in the differential interferometric detection of high-order comb teeth.

[0093] As one possible implementation, S2 performs real-time feedback compensation for the optical link delay of the measurement arm, specifically including: The link delay of the measuring arm is adjusted by the first delay compensation unit; The link delay of the measuring arm is adjusted by the second delay compensation unit; The first delay compensation unit and the second delay compensation unit are cascaded, and the adjustment scale of the first delay compensation unit is larger than that of the second delay compensation unit.

[0094] The technical solution of this invention utilizes a cascaded structure of the first and second delay compensation units, which is an optimized design that balances adjustment range and resolution. The specific implementation mechanism is as follows: (1) First delay compensation unit: used for coarse adjustment, responsible for large-scale dynamic compensation This unit typically consists of a mechanically adjustable delay line (such as a motor delay line) or a temperature-controlled optical delay line, offering a large adjustment range (up to hundreds of picoseconds or even nanoseconds) to handle large amplitude and slow-varying optical path drift. Its adjustment step size is relatively large, resulting in a slower response speed, but it boasts strong coverage.

[0095] (2) Second delay compensation unit: used for fine-tuning to achieve high-resolution real-time correction. This unit typically employs a piezoelectric ceramic tensioner, with a relatively small adjustment range (within a few picoseconds), but it possesses sub-picosecond or even femtosecond-level adjustment accuracy and high-speed response capabilities. It is primarily used to compensate for rapid delay jitter.

[0096] (3) Cascaded collaborative working mechanism The two units are connected in series in the optical path of the measuring arm, forming a "coarse-fine two-stage feedback" structure. Their cascaded collaborative working mechanism is as follows: ① The phase detection module first identifies the delay error; ② The first delay compensation unit performs large-scale delay compensation to ensure that the second delay compensation unit is in a stable operating range; ③ The second delay compensation unit responds quickly and makes continuous fine adjustments to maintain stable link delay.

[0097] The technical solution of this invention can significantly improve the system's adaptability to complex environmental disturbances, and while ensuring long-term stability, avoid the difficulty of balancing dynamic range and accuracy of a single compensator.

[0098] As one possible implementation, the frequency tuning step size of the first laser and the second laser is smaller than the repetition frequency of the optical frequency comb signal, and the frequency tuning range is not limited by the available comb tooth order of the optical frequency comb signal. Frequency tuning is achieved by adjusting the initial wavelength of the first laser and the second laser.

[0099] In the technical solution provided in this embodiment, the frequency tuning capability of the first and second lasers is the key to determining the flexibility of the final millimeter-wave output. The tuning step size is determined by the control accuracy of the laser itself and the tracking capability of the phase-locked loop, which is much smaller than the repetition frequency of the optical frequency comb. At the same time, the tuning range is no longer limited by the number of available comb teeth.

[0100] Its specific implementation mechanism is as follows: (1) The frequency tuning step size is smaller than the repetition frequency of the optical frequency comb. The optically generated millimeter-wave system provided in this invention allows for independent temperature adjustment of two lasers via a control interface, enabling rapid re-locking of their wavelengths after a phase-locked loop (PLL) loss, thus achieving frequency tuning with a small step size. This allows for more flexible adjustment of the millimeter-wave frequency generated by the beat frequency of the two lasers.

[0101] (2) The tuning range is not limited by the order of the comb teeth, but only depends on the operating wavelength of the laser. The optically generated millimeter-wave system provided in this embodiment of the invention maintains relative stability during closed-loop locking by pre-adjusting the initial output wavelengths of the first and second lasers. As long as the interference link remains locked, the coherence of the two lasers can be guaranteed, and the change in beat frequency depends only on the frequency interval between them. Therefore, theoretically, a wide tuning range greater than the optical frequency comb spectrum range can be achieved, limited only by the tuning capability of the lasers themselves and the bandwidth of the photodetector.

[0102] The optically generated millimeter-wave system provided in this invention has the advantages of balancing long-term stability and flexible tunability. First, it has high frequency stability, thanks to the real-time suppression of link jitter by the interference structure and the frequency locking mechanism of the dual lasers. Second, it has wide bandwidth coverage, which, combined with the wide wavelength adjustment capability of the tunable laser, can generate millimeter-wave signals from tens of GHz to hundreds of GHz. Third, it has strong adaptability to application scenarios, and is suitable for advanced systems that require high frequency stability and tuning range, such as frequency agility and frequency hopping communication.

[0103] This architecture deeply integrates the high sensitivity of the interferometer with the tunability of the laser, enabling a new paradigm for millimeter-wave generation that is both stable and agile.

[0104] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in the second aspect.

[0105] The embodiments of the present invention provide a program carrier for implementing the method described in the second aspect—a computer-readable storage medium, which may be a physical medium such as ROM, RAM, hard disk, optical disk, or USB flash drive.

[0106] To facilitate understanding of the technical solution of this application, further explanation is provided below with reference to specific embodiments.

[0107] Example 1 The wavelengths of the first and second lasers are set to 1550.02nm and 1550.22nm, respectively, corresponding to a frequency interval of approximately 22.5GHz. After the three phase-locked loops of the system are in operation, a high-speed photodetector is used at the optical output to receive the signal, and the obtained millimeter-wave signal is fed into a spectrum analyzer to measure the frequency.

[0108] The millimeter-wave signal is frequency-tuned by adjusting the initial wavelength of the laser. Figure 2 This is the frequency tuning spectrum of the millimeter-wave signal generated by the system. The repetition frequency of the optical frequency comb in this device is 25 GHz, while... Figure 2The average tuning step shown is approximately 1.2 GHz, which is much smaller than the repetition frequency of the optical frequency comb. Therefore, this scheme can achieve a smaller tuning step and is no longer limited by the repetition frequency of the optical frequency comb.

[0109] The two lasers were spaced approximately 22.5 GHz apart. A high-speed photodetector was used to receive the light at the output, and the obtained millimeter-wave signal was fed into a spectrum analyzer to measure frequency changes. In this embodiment, the long-term frequency changes were measured with and without the three phase-locked loops operating. The test results are as follows: Figure 3 As shown.

[0110] The test results show that, within 5000 seconds, the frequency variation of the optically generated millimeter wave exceeded 22 MHz under free-running conditions. On the same vertical axis, when three phase-locked loops were operating, the frequency variation of the millimeter wave was not significant, with a root mean square value of approximately 95 Hz, which is 5-6 orders of magnitude smaller in comparison.

[0111] Example 2 The wavelengths of the first and second lasers were set to 1546.45 nm and 1554.31 nm, respectively, corresponding to a frequency interval of approximately 1 THz. At this point, the millimeter-wave signal frequency was too high to be directly obtained using a photodetector. An optical frequency comb was used as a bridge, and then a photodetector was employed to obtain an intermediate frequency (IF) signal that reflected the frequency changes of the millimeter-wave. This IF signal was then fed into a spectrum analyzer to measure frequency changes, and the test results are as follows... Figure 4 As shown.

[0112] The test results show that during the 5000s measurement period, the frequency change measured in the laser's free-running state exceeded 20MHz, while the frequency change significantly decreased after the phase-locked loop (PLL) was activated, with a root mean square (RMS) value of approximately 201Hz for frequency jitter. This indicates that the high-frequency millimeter-wave signal generated by this system also exhibits good long-term frequency stability. Furthermore, it demonstrates a wide tuning frequency range, capable of frequency tuning from at least 15GHz to 1THz.

[0113] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the description of the drawings, in carrying out the claimed invention. In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several of the functions listed in the specification. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0114] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A light-generated millimeter-wave system based on an optical frequency comb-stabilized interference structure, characterized in that, include: Optical frequency comb module, used to output optical frequency comb signal; The interferometer module includes a reference arm, a measuring arm, a first optical coupler, and a second optical coupler. The first optical coupler splits the input optical signal into two paths, which enter the reference arm and the measurement arm respectively; the second optical coupler combines the optical signals output from the reference arm and the measurement arm; the measurement arm includes a delay compensation unit for compensating for the optical link delay of the measurement arm; The phase detection and link locking module is used to input the optical frequency comb signal to the interferometer module, and use the interferometer signal output by the interferometer module to detect the link delay jitter between the measurement arm and the reference arm. Based on the detection result, a first control signal is generated to control the delay compensation module so that the link delay of the interferometer module remains stable. The first laser and the second laser are used to output two laser beams with different wavelengths. A portion of the combined laser beam is used as an optically generated millimeter wave output. The laser frequency stabilization module is used to inject the laser outputs from the first laser and the second laser into the interference module whose link delay has been stabilized, respectively. The output signal of the interference module is used to detect the frequency drift of the first laser and the second laser, respectively. Based on the detection results, a third control signal and a second control signal are generated. The third control signal is used to control the output frequency of the first laser, and the second control signal is used to control the output frequency of the second laser, so that the first laser and the second laser are locked to the same stable fiber optic link delay, thereby obtaining a frequency-stable optically generated millimeter wave.

2. The optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure according to claim 1, characterized in that, The delay compensation unit includes: The first delay compensation unit adjusts the link delay of the measuring arm on a first scale. The second delay compensation unit, cascaded with the first delay compensation unit, is used to adjust the link delay of the measuring arm on a second scale; wherein the first scale is greater than the second scale.

3. The optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure according to claim 2, characterized in that, The first delay compensation unit is a motor delay line or a temperature-controlled fiber optic delay line; the second delay compensation unit is a piezoelectric ceramic tensioner.

4. The optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure according to claim 1, characterized in that, The phase detection and link locking module includes: The first optical filter is disposed between the optical frequency comb module and the first optical coupler, and is used to extract the initial high-order comb tooth pairs of positive and negative order from the optical frequency comb signal as a probe signal for detecting link delay jitter. The second optical filter, located after the second optical coupler, is used to filter out the interference signals corresponding to the probe signals respectively; The first photodetector and the second photodetector are disposed after the second optical filter and are used to receive the interference signal output by the interference module and convert it into a first electrical signal and a second electrical signal that reflect the link delay, respectively. The first phase-locked loop is used to receive the first electrical signal and the second electrical signal, perform phase comparison to obtain an error signal, and generate a first control signal based on the error signal.

5. The optically generated millimeter-wave system based on an optical frequency comb-stabilized interference structure according to claim 4, characterized in that, The laser frequency stabilization module includes: The third optical coupler is used to combine the output laser beams of the first laser and the second laser, and then divide them into two parts with equal power. One part is injected into the interference module, and the other part is used to generate optical millimeter waves. The second optical filter, located after the second optical coupler, is also used to filter out the interference signals carrying the frequency information of the first and second lasers respectively; the phase detection and link locking module and the laser frequency stabilization module share the second optical filter; The third photodetector is used to receive the interference signal carrying the frequency information of the second laser after being filtered out by the second optical filter, and convert it into a third electrical signal; The fourth photodetector is used to receive the interference signal carrying the frequency information of the first laser after being filtered out by the second optical filter, and convert it into a fourth electrical signal; Radio frequency signal generator, used to provide a reference signal; The second phase-locked loop is used to compare the phase of the third electrical signal with the reference signal provided by the radio frequency signal generator, and generate a second control signal based on the comparison result to control the second laser. The third phase-locked loop is used to compare the phase of the fourth electrical signal with the reference signal provided by the radio frequency signal generator, and generate a third control signal based on the comparison result to control the first laser.

6. A method for generating millimeter waves based on an optical frequency comb-stabilized interference structure, applied to the system described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Generate an optical frequency comb signal and inject it into the interference optical path. By detecting the output signals of the reference arm and the measurement arm in the interference optical path, obtain the link delay jitter information. S2. Based on the link delay jitter information, perform real-time feedback compensation on the optical link delay of the measurement arm to keep the link delay of the interference optical path stable; S3. Inject the lasers output from the first laser and the second laser into the interference optical path whose link delay has been stabilized, and obtain the frequency drift information of the first laser and the second laser by detecting the output signal of the interference optical path; S4. Based on the frequency drift information of the first laser and the second laser, the output frequencies of the first laser and the second laser are controlled in real time to lock them both to the same stable fiber optic link delay. S5. Combine the output lasers of the first and second lasers after frequency locking, and obtain a frequency-stable millimeter-wave signal through photoelectric conversion.

7. The method for generating millimeter waves based on an optical frequency comb-stabilized interference structure according to claim 6, characterized in that, S1 obtains link delay jitter information, specifically including: extracting high-order comb tooth pairs of positive and negative order from the optical frequency comb signal as probe signals and injecting them into the interference optical path, and performing photoelectric conversion and phase comparison on the two signals output from the interference optical path to obtain an error signal reflecting the link delay jitter.

8. The method for generating millimeter waves based on an optical frequency comb-stabilized interference structure according to claim 6, characterized in that, S2 performs real-time feedback compensation for the optical link delay of the measurement arm, specifically including: The link delay of the measuring arm is adjusted by the first delay compensation unit; The link delay of the measuring arm is adjusted by the second delay compensation unit; The first delay compensation unit and the second delay compensation unit are cascaded, and the adjustment scale of the first delay compensation unit is larger than that of the second delay compensation unit.

9. The method for generating millimeter waves based on an optical frequency comb-stabilized interference structure according to claim 6, characterized in that, The frequency tuning step size of the first laser and the second laser is smaller than the repetition frequency of the optical frequency comb signal, and the frequency tuning range is not limited by the available comb tooth order of the optical frequency comb signal. Frequency tuning is achieved by adjusting the initial wavelength of the first laser and the second laser.

10. A computer-readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the method as claimed in any one of claims 6 to 9.

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