Optical comb frequency control system and method for optically generated ultra-stable microwave source

Abstract

The present invention discloses an optical comb frequency control system and method for an optically generated ultra-stable microwave source, comprising: at least one optical comb signal frequency adjustment loop, the loop comprising an optical frequency comb, a phase detector, a phase difference extraction circuit and a PID circuit; the output end of the optical frequency comb is electrically connected to the input end of the phase detector, one input end of the phase detector is also connected to a reference signal, the output end of the phase detector is electrically connected to the input end of the phase difference extraction circuit, the output end of the phase difference extraction circuit is electrically connected to the input end of the PID circuit, and the output end of the PID circuit is electrically connected to the input end of the optical frequency comb. The present invention can realize an optical comb frequency control system with a larger phase detection range, lower bottom noise and higher gain bandwidth.

Description

Technical Field

[0001] The present invention belongs to the field of optical comb technology, and in particular relates to an optical comb frequency control system and method for an optically generated ultra-stable microwave source. Background Art

[0002] Optical frequency combs can stabilize the frequency or phase of lasers to an external reference source. Locking and controlling the frequency and phase of electromagnetic radiation (visible light, infrared light, microwaves and other electromagnetic waves) can improve the accuracy and stability of lasers. They are used in high-performance frequency standards, radars, navigation and other fields, and are also an important component of optically generated ultra-stable microwave sources. Optically generated ultra-stable microwave sources are based on ultra-stable laser and optical comb technologies. They can convert ultra-high stability ultra-stable laser frequency signals into microwave frequency bands to generate ultra-stable microwave sources. They are currently the microwave frequency sources with the highest frequency stability. Optically generated ultra-stable microwave sources are also the basis for the promotion and application of future frequency standards (optical frequency standards). Whether it is the generation of time or the vast majority of precision measurements, they can only be achieved after the output laser of the optical frequency standard is converted into an ultra-stable baseband frequency signal.

[0003] Optical combs have important application value in locking the frequency of electromagnetic radiation. They can realize accurate measurement and control of electromagnetic frequency. They are devices that generate ultra-stable microwave signals. To achieve this goal, the repetition frequency and carrier envelope frequency shift of the optical comb need to be locked to a stable reference signal respectively, so that each frequency tooth of the optical comb has a certain value. The commonly used locking method is to use phase-locked loop technology to detect the phase difference or beat frequency signal between the optical comb and the reference signal, compare the beat frequency signal with the reference signal, and obtain an error signal; input the error signal into the PID control circuit to generate a feedback signal; input the feedback signal into the light source to be locked to adjust the laser to keep it synchronized with the reference signal. The reference signal is generally provided by an atomic clock or a stable laser.

[0004] In the application of optical comb, the frequency of the optical comb needs to be locked to the reference frequency. The existing multiplication phase detector has some significant disadvantages in frequency locking and phase detection applications. The phase detection range of the multiplication phase detector is narrow. arrive The noise floor is usually higher, and a higher noise floor will introduce more phase noise; the gain bandwidth is usually lower, affecting the locking speed and accuracy; the output signal linearity is poor, which will introduce nonlinear errors; it is more sensitive to the amplitude change of the input signal, and changes in the input signal amplitude will affect the locking performance.

[0005] Therefore, there is an urgent need to provide an optical comb frequency control system and method for a photogenerated ultra-stable microwave source to improve the above-mentioned defects. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides an optical comb frequency control system and method for an optically generated ultra-stable microwave source. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0007] In a first aspect, the present invention provides an optical comb frequency control system for an optically generated ultra-stable microwave source, comprising:

[0008] At least one optical comb signal frequency adjustment loop;

[0009] The optical comb signal frequency adjustment loop includes an optical frequency comb, a phase detector, a phase difference extraction circuit and a PID circuit; wherein the output end of the optical frequency comb is electrically connected to the input end of the phase detector, one input end of the phase detector is also connected to a reference signal, the output end of the phase detector is electrically connected to the input end of the phase difference extraction circuit, the output end of the phase difference extraction circuit is electrically connected to the input end of the PID circuit, and the output end of the PID circuit is electrically connected to the input end of the optical frequency comb;

[0010] The optical frequency comb is used to output an optical comb signal, the phase detector is used to detect the phase difference between the optical comb signal and a reference signal, the phase difference extraction circuit is used to extract the phase difference detected by the phase detector to obtain a phase detection signal, the PID circuit is used to convert the phase detection signal into a frequency control signal, and feed the frequency control signal back to the optical frequency comb, and the optical frequency comb adjusts the frequency of the output optical comb signal according to the frequency control signal until the frequency of the optical comb signal input to the phase detector is automatically locked with the frequency of the reference signal.

[0011] In a second aspect, the present invention further provides a method for controlling an optical comb frequency for an optically generated ultra-stable microwave source, which is applied to the optical comb frequency control system for an optically generated ultra-stable microwave source as provided above, and the method comprises:

[0012] Outputting optical comb signal;

[0013] Detecting the phase difference between the current optical comb signal and the reference signal, and extracting the phase difference to obtain a phase detection signal;

[0014] Convert the phase detection signal into a frequency control signal;

[0015] According to the frequency control signal, the frequency of the output optical comb signal is adjusted, and then the phase difference between the optical comb signal after the frequency adjustment and the reference signal is detected until the frequency of the adjusted optical comb signal is automatically locked with the frequency of the reference signal.

[0016] Beneficial effects of the present invention:

[0017] The present invention provides an optical comb frequency control system and method for an optically generated ultra-stable microwave source. At least one optical comb signal frequency adjustment loop is set, and the loop includes an optical frequency comb, a phase detector, a phase difference extraction circuit and a PID circuit. The optical frequency comb is used to output an optical comb signal, the phase detector is used to detect the phase difference between the optical comb signal and a reference signal, the reference signal is provided by an atomic clock or a stable laser, the phase difference extraction circuit is used to extract the phase difference and generate a phase detection signal, the PID circuit converts the phase detection signal into a frequency control signal, and feeds the frequency control signal back to the optical frequency comb. The optical frequency comb adjusts the frequency of the optical comb signal output according to the frequency control signal until the frequency of the optical comb signal input to the phase detector is automatically locked with the frequency of the reference signal. In this way, the present invention uses a phase detector to detect the phase difference between the optical comb signal and the reference signal, and sets a PID circuit to lock the frequency control signal corresponding to the phase difference to adjust the frequency of the output optical comb signal, so as to achieve an optical comb frequency control system with a larger phase detection range, lower bottom noise and higher gain bandwidth.

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of an optical comb frequency control system for an optically generated ultra-stable microwave source provided by an embodiment of the present invention;

[0020] Figure 2 is another schematic diagram of an optical comb frequency control system for an optically generated ultra-stable microwave source provided by an embodiment of the present invention;

[0021] Figure 3 is another schematic diagram of an optical comb frequency control system for an optically generated ultra-stable microwave source provided by an embodiment of the present invention;

[0022] Figure 4 is a flow chart of a method for controlling the frequency of an optical comb used for an optically generated ultra-stable microwave source provided by an embodiment of the present invention;

[0023] Figure 5 is a schematic diagram of a phase detector output provided by an embodiment of the present invention;

[0024] Figure 6 It is a schematic diagram of the slope change of the phase-lock signal provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0026] See also Figure 1 , Figure 11 is a schematic diagram of an optical comb frequency control system for an optically generated ultra-stable microwave source provided by an embodiment of the present invention. An optical comb frequency control system for an optically generated ultra-stable microwave source provided by the present invention comprises: at least one optical comb signal frequency adjustment loop;

[0027] The optical comb signal frequency adjustment loop includes an optical frequency comb, a phase detector 10, a phase difference extraction circuit and a PID circuit; wherein the output end of the optical frequency comb is electrically connected to the input end of the phase detector 10, one input end of the phase detector 10 is also connected to a reference signal, the output end of the phase detector 10 is electrically connected to the input end of the phase difference extraction circuit, the output end of the phase difference extraction circuit is electrically connected to the input end of the PID circuit, and the output end of the PID circuit is electrically connected to the input end of the optical frequency comb;

[0028] The optical frequency comb is used to output an optical comb signal, the phase detector 10 is used to detect the phase difference between the optical comb signal and a reference signal, the phase difference extraction circuit is used to extract the phase difference detected by the phase detector 10 to obtain a phase detection signal, the PID circuit is used to convert the phase detection signal into a frequency control signal, and feed the frequency control signal back to the optical frequency comb, and the optical frequency comb adjusts the frequency of the output optical comb signal according to the frequency control signal until the frequency of the optical comb signal input to the phase detector 10 is automatically locked with the frequency of the reference signal.

[0029] For more details, please see Figure 1 The present embodiment provides an optical comb frequency control system for an optically generated ultra-stable microwave source, comprising at least one optical comb signal frequency adjustment loop, wherein the loop comprises an optical frequency comb, a phase detector 10, a phase difference extraction circuit and a PID circuit; wherein the optical frequency comb is used to output an optical comb signal, the phase detector 10 is used to detect the phase difference between the optical comb signal and a reference signal, the reference signal is provided by an atomic clock or a stable laser, the phase difference extraction circuit is used to extract the phase difference and generate a phase detection signal, the PID circuit converts the phase detection signal into a frequency control signal, and feeds the frequency control signal back to the optical frequency comb, and the optical frequency comb adjusts the frequency of the optical comb signal outputted therefrom according to the frequency control signal until the frequency of the optical comb signal inputted to the phase detector 10 is automatically locked with the frequency of the reference signal; thus, the present embodiment adopts the phase detector 10 to detect the phase difference between the optical comb signal and the reference signal, and sets the PID circuit to lock the frequency control signal corresponding to the phase difference, so as to adjust the frequency of the output optical comb signal, thereby realizing an optical comb frequency control system with a larger phase detection range, lower bottom noise and higher gain bandwidth.

[0030] In an optional embodiment of the present invention, the phase detector 10 is a frequency detector and a high-gain phase detector.

[0031] Specifically, considering the disadvantages of the multiplication phase detector in the prior art in frequency locking and phase detection applications, for example, the phase detection range of the multiplication phase detector is narrow. arrive The background noise is usually high, and a higher background noise will introduce more phase noise; the gain bandwidth is usually low, which affects the locking speed and accuracy; the output signal linearity is poor, which will introduce nonlinear errors; it is sensitive to the amplitude change of the input signal, and the locking performance will be affected when the input signal amplitude changes; in this embodiment, a phase frequency detector (PFD) is introduced, and the phase frequency detector is used for phase detection. The output phase detector has low sensitivity to the amplitude change of the input signal, so that the frequency locking of the optical comb is more stable and reliable, and there will be no mismatch of PID circuit parameters due to changes in the characteristics of the phase detection signal; at the same time, it has a larger phase detection range, lower background noise and higher gain bandwidth, and is insensitive to changes in the signal amplitude, and can provide a higher-precision phase detection signal, so that the optical comb frequency signal locked by the system has lower noise and better stability.

[0032] In an optional embodiment of the present invention, see Figure 2 and Figure 3 , Figure 2 is another schematic diagram of an optical comb frequency control system for an optically generated ultra-stable microwave source provided by an embodiment of the present invention, Figure 3 It is another schematic diagram of an optical comb frequency control system for an optically generated ultra-stable microwave source provided in an embodiment of the present invention. The phase difference extraction circuit includes a differential amplifier 20. One input end of the differential amplifier 20 is electrically connected to an output end of the phase detector 10. The other input end of the differential amplifier 20 is electrically connected to the other output end of the phase detector 10. The differential amplifier 20 is used to process the first signal and the second signal output by the phase detector 10 to obtain a phase detection signal.

[0033] For more details, please see Figure 2 In this embodiment, the phase difference extraction circuit includes a differential amplifier 20. The differential amplifier 20 subtracts the first signal UP output by the phase detector 10 from the second signal DOWN to obtain a phase detection signal. The differential amplifier 20 is used for processing, which can effectively suppress common mode noise, so that the output phase detection signal has a low noise floor. In addition, the high-gain phase detector has a larger phase detection range, so that the phase detection signal has a better signal-to-noise ratio. The high signal-to-noise ratio enables the system to detect and control weaker phase difference changes, while the control bandwidth is higher and the noise suppression is better.

[0034] In an optional embodiment of the present invention, please continue to refer to Figure 2A filter is also provided between the phase difference extraction circuit and the PID circuit. The input end of the filter is electrically connected to the output end of the phase difference extraction circuit, and the output end of the filter is electrically connected to the input end of the PID circuit. The filter is used to process the phase detection signal to remove high-frequency noise.

[0035] Specifically, in this embodiment, a filter is provided between the phase difference extraction circuit and the PID circuit, and the filter can remove high-frequency noise and generate a smooth phase detection signal.

[0036] In an optional embodiment of the present invention, please continue to refer to Figure 2 A bandpass filter is also provided between the optical frequency comb and the phase detector 10, the input end of the bandpass filter is electrically connected to the output end of the optical frequency comb, and the output end of the bandpass filter is electrically connected to the input end of the phase detector 10 to remove frequency noise outside the preset frequency.

[0037] Specifically, in this embodiment, a bandpass filter is provided between the optical frequency comb and the phase detector 10, and the bandpass filter can retain the optical comb signal of a preset frequency and remove other frequency noises outside the preset frequency.

[0038] In an optional embodiment of the present invention, please continue to refer to Figure 2 The optical frequency comb includes an optical fiber, a pump driver, a gain medium 40, an electro-optic modulator 30 and a piezoelectric ceramic 50; wherein the gain medium 40 and the electro-optic modulator 30 are both integrated on the end face of the optical fiber, the output end of the pump driver is electrically connected to the input end of the gain medium 40, and the output end of the electro-optic modulator 30 is electrically connected to the input end of the piezoelectric ceramic 50.

[0039] Specifically, in this embodiment, the optical frequency comb is provided with an optical fiber, a pump driver, a gain medium 40, an electro-optic modulator 30 and a piezoelectric ceramic 50, which are used to adjust the frequency of the output optical comb signal under different loops.

[0040] In an optional embodiment of the present invention, please continue to refer to Figure 2 and Figure 3 , when the optical comb frequency control system includes an optical comb signal frequency adjustment loop, the optical comb signal includes any one of a carrier envelope phase shift frequency signal fceo, a repetition frequency signal fr or an optical beat frequency signal fbeat;

[0041] The output end of the PID circuit is electrically connected to the input end of the electro-optic modulator 30, the output end of the piezoelectric ceramic 50 is electrically connected to the input end of the phase detector 10, and the frequency control signal corresponding to the repetition frequency signal fr or the optical beat frequency signal fbeat is fed back to the electro-optic modulator 30 and the piezoelectric ceramic 50 for processing to adjust the frequency of the output repetition frequency signal fr or the optical beat frequency signal fbeat; or,

[0042] The output end of the PID circuit is electrically connected to the input end of the pump driver, the output end of the gain medium 40 is electrically connected to the input end of the phase detector 10, and the frequency control signal corresponding to the carrier-envelope phase-shifted frequency signal fceo is fed back to the pump driver and the gain medium 40 for processing to adjust the frequency of the output carrier-envelope phase-shifted frequency signal fceo.

[0043] Specifically, in this embodiment, when the optical comb frequency control system is only provided with one optical comb signal frequency adjustment loop, the frequency control signal corresponding to the carrier envelope phase shift frequency signal fceo is processed by the pump drive and gain medium 40 to adjust the frequency of the output carrier envelope phase shift frequency signal fceo; or, the frequency control signal corresponding to the repetition frequency signal fr or the optical beat frequency signal fbeat is processed by the electro-optical modulator 30 and the piezoelectric ceramic 50 to adjust the frequency of the output repetition frequency signal fr or the optical beat frequency signal fbeat; it can also be understood that the adjustment loops of the carrier envelope phase shift frequency signal fceo and the repetition frequency signal fr or the optical beat frequency signal fbeat are different, and the adjustment loops of the repetition frequency signal fr or the optical beat frequency signal fbeat are the same, and when the optical comb frequency control system is provided with one optical comb signal frequency adjustment loop, the frequency of only one signal can be adjusted.

[0044] In an optional embodiment of the present invention, please continue to refer to Figure 2 and Figure 3 , when the optical comb frequency control system includes two optical comb signal frequency adjustment loops, the optical comb signal includes any one of a carrier envelope phase shift frequency signal fceo, a repetition frequency signal fr or an optical beat frequency signal fbeat;

[0045] In one optical comb signal frequency adjustment loop, the output end of the PID circuit is electrically connected to the input end of the electro-optic modulator 30, the output end of the piezoelectric ceramic 50 is electrically connected to the input end of the phase detector 10, and the frequency control signal corresponding to the repetition frequency signal fr or the optical beat frequency signal fbeat is fed back to the electro-optic modulator 30 and the piezoelectric ceramic 50 for processing to adjust the frequency of the output repetition frequency signal fr or the optical beat frequency signal fbeat;

[0046] In another optical comb signal frequency adjustment loop, the output end of the PID circuit is electrically connected to the input end of the pump driver, the output end of the gain medium 40 is electrically connected to the input end of the phase detector 10, and the frequency control signal corresponding to the carrier-envelope phase-shifted frequency signal fceo is fed back to the pump driver and the gain medium 40 for processing to adjust the frequency of the output carrier-envelope phase-shifted frequency signal fceo.

[0047] Specifically, in this embodiment, when the optical comb frequency control system sets two optical comb signal frequency adjustment loops, the carrier envelope phase shift frequency signal fceo and the repetition frequency signal fr can be adjusted at the same time, or the carrier envelope phase shift frequency signal fceo and the optical beat frequency signal fbeat can be adjusted at the same time to achieve multi-path adjustment of the frequencies of different signals.

[0048] In the above embodiments, whether the self-adjustment of the optical comb frequency is achieved through pump drive and gain medium 40, or through electro-optic modulator 30 and piezoelectric ceramic 50, the disadvantages of manual adjustment, such as complex operation, time consumption, limited accuracy, insufficient stability, poor repeatability and high labor cost, are overcome; the automatic locking phase technology provided in this embodiment has the advantages of high precision, fast response, high stability, simple operation, high repeatability, low labor cost, real-time monitoring and adjustment, strong adaptability and high system reliability, which significantly improves the efficiency and effect of automatic locking of the optical comb frequency, so that the optical comb can be automatically and stably operated for a long time.

[0049] Based on the same inventive concept, see Figure 4 , Figure 4 1 is a flow chart of a method for controlling an optical comb frequency for an optically generated ultra-stable microwave source provided in an embodiment of the present invention. The present invention further provides a method for controlling an optical comb frequency for an optically generated ultra-stable microwave source, which is applied to the optical comb frequency control system for an optically generated ultra-stable microwave source provided in the above embodiment of the present invention. The embodiment of the system is referred to above and will not be described in detail herein. The method comprises:

[0050] S101, outputting an optical comb signal;

[0051] S102, detecting a phase difference between the current optical comb signal and the reference signal, and extracting the phase difference to obtain a phase detection signal;

[0052] S103, converting the phase detection signal into a frequency control signal;

[0053] S104, adjusting the frequency of the output optical comb signal according to the frequency control signal, and then detecting the phase difference between the optical comb signal after the frequency adjustment and the reference signal, until the frequency of the adjusted optical comb signal is automatically locked with the frequency of the reference signal.

[0054] In an optional embodiment of the present invention, see Figure 5 , Figure 5 It is a schematic diagram of the output of the phase detector provided by an embodiment of the present invention. The frequency difference between the optical comb signal and the reference signal is proportional to the slope of the phase detection signal, and the phase difference between the optical comb signal and the reference signal is proportional to the voltage of the phase detection signal.

[0055] Specifically, in this embodiment, according to the relationship between the frequency difference between the optical comb signal and the reference signal and the slope of the phase detection signal, the frequency of the optical comb signal is further adjusted to automatically lock with the frequency of the reference signal.

[0056] In an optional embodiment of the present invention, see Figure 6 , Figure 6 is a schematic diagram of the slope change of the phase detection signal provided by an embodiment of the present invention. The condition for the frequency of the optical comb signal to be automatically locked with the frequency of the reference signal is that the slope of the phase detection signal is zero, that is, automatic locking is achieved; it can be understood that during the adjustment process, the phase detection signal pushes the frequency of the optical comb signal to move toward the reference signal, and the slope of the phase detection signal decreases accordingly. Figure 6 As shown, until the slope of the phase detection signal is zero, automatic locking is achieved.

[0057] In an optional embodiment of the present invention, the process of automatically locking the frequency of the carrier envelope phase shift frequency signal fceo with the frequency of the reference signal includes:

[0058] After the carrier-envelope phase-shift frequency signal fceo is processed by the bandpass filter, it is input to the frequency detector. At the same time, the reference signal is also input to the frequency detector. The frequency detector detects the phase difference between the two. The phase difference extraction circuit extracts the phase difference between the two and generates a phase detection signal proportional to the phase difference. The high-frequency noise is then removed by the loop filter to generate a smooth phase detection signal. The phase detection signal output by the loop filter is input to the PID circuit. The frequency control signal generated by the PID circuit reaches the pump drive and gain medium 40 of the optical frequency comb. The pump drive and gain medium 40 adjust their output frequency according to the frequency control signal. The carrier-envelope phase-shift frequency signal fceo after frequency adjustment is fed back to the frequency detector to form a closed-loop control. By continuously adjusting the frequency of the carrier-envelope phase-shift frequency signal fceo, the frequency of the carrier-envelope phase-shift frequency signal fceo is controlled to be precisely locked with the frequency of the reference signal.

[0059] In an optional embodiment of the present invention, the process of automatically locking the frequency of the repetitive frequency signal fr with the frequency of the reference signal includes:

[0060] After the repetition frequency signal fr is processed by the bandpass filter, it is input to the frequency detector. At the same time, the reference signal is also input to the frequency detector. The frequency detector detects the phase difference between the two. The phase difference extraction circuit extracts the phase difference between the two and generates a phase detection signal proportional to the phase difference. Then, the loop filter removes the high-frequency noise and generates a smooth phase detection signal. The phase detection signal output by the loop filter is input to the PID circuit. The frequency control signal generated by the PID circuit reaches the electro-optical modulator 30 and the piezoelectric ceramic 50 of the optical frequency comb. The electro-optical modulator 30 and the piezoelectric ceramic 50 adjust their output frequency according to the frequency control signal. The repetition frequency signal fr after frequency adjustment is fed back to the frequency detector to form a closed-loop control. By continuously adjusting the frequency of the repetition frequency signal fr, the frequency of the repetition frequency signal fr is controlled to be accurately locked with the frequency of the reference signal.

[0061] In an optional embodiment of the present invention, the process of automatically locking the frequency of the optical beat frequency signal fbeat with the frequency of the reference signal includes:

[0062] After the optical beat frequency signal fbeat is processed by the bandpass filter, it is input to the frequency detector. At the same time, the reference signal is also input to the frequency detector. The frequency detector detects the phase difference between the two. The phase difference extraction circuit extracts the phase difference between the two and generates a phase detection signal proportional to the phase difference. The high-frequency noise is then removed by the loop filter to generate a smooth phase detection signal. The phase detection signal output by the loop filter is input to the PID circuit. The frequency control signal generated by the PID circuit reaches the electro-optical modulator 30 and the piezoelectric ceramic 50 of the optical frequency comb. The electro-optical modulator 30 and the piezoelectric ceramic 50 adjust their output frequency according to the frequency control signal. The frequency-adjusted optical beat frequency signal fbeat is fed back to the frequency detector to form a closed-loop control. By continuously adjusting the frequency of the optical beat frequency signal fbeat, the frequency of the optical beat frequency signal fbeat is controlled to be accurately locked with the frequency of the reference signal.

[0063] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant is intended to cover non-exclusive inclusion, so that the article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the article or device including the elements. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The orientation or position relationship indicated by "up", "down", "left", "right", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0064] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0065] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. An optical comb frequency control system for an optically generated ultra-stable microwave source, characterized in that: include: At least one optical comb signal frequency adjustment loop; The optical comb signal frequency adjustment loop comprises an optical frequency comb, a phase detector, a phase difference extraction circuit and a PID circuit; wherein the output end of the optical frequency comb is electrically connected to one input end of the phase detector, the other input end of the phase detector is connected to a reference signal, the output end of the phase detector is electrically connected to the input end of the phase difference extraction circuit, the output end of the phase difference extraction circuit is electrically connected to the input end of the PID circuit, and the output end of the PID circuit is electrically connected to the input end of the optical frequency comb; wherein the phase detector is a frequency detector, and the phase difference extraction circuit comprises a differential amplifier; The optical frequency comb is used to output an optical comb signal, the phase detector is used to detect the phase difference between the optical comb signal and the reference signal, the phase difference extraction circuit is used to extract the phase difference detected by the phase detector to obtain a phase detection signal, the PID circuit is used to convert the phase detection signal into a frequency control signal, and feed the frequency control signal back to the optical frequency comb, and the optical frequency comb adjusts the frequency of the output optical comb signal according to the frequency control signal until the frequency of the optical comb signal input to the phase detector is automatically locked with the frequency of the reference signal.

2. The optical comb frequency control system for an optically generated ultrastable microwave source according to claim 1, characterized in that: One input end of the differential amplifier is electrically connected to one output end of the phase detector, and the other input end of the differential amplifier is electrically connected to the other output end of the phase detector. The differential amplifier is used to process the first signal and the second signal output by the phase detector to obtain a phase detection signal.

3. The optical comb frequency control system for an optically generated ultrastable microwave source according to claim 1, characterized in that: A filter is also arranged between the phase difference extraction circuit and the PID circuit, the input end of the filter is electrically connected to the output end of the phase difference extraction circuit, the output end of the filter is electrically connected to the input end of the PID circuit, and the filter is used to process the phase detection signal to remove high-frequency noise.

4. The optical comb frequency control system for an optically generated ultrastable microwave source according to claim 1, characterized in that: A bandpass filter is also provided between the optical frequency comb and the phase detector, the input end of the bandpass filter is electrically connected to the output end of the optical frequency comb, and the output end of the bandpass filter is electrically connected to the input end of the phase detector to remove frequency noise outside the preset frequency.

5. The optical comb frequency control system for an optically generated ultrastable microwave source according to claim 1, characterized in that: The optical frequency comb includes an optical fiber, a pump drive, a gain medium, an electro-optic modulator and a piezoelectric ceramic; wherein the gain medium and the electro-optic modulator are both integrated on the end face of the optical fiber, the output end of the pump drive is electrically connected to the input end of the gain medium, and the output end of the electro-optic modulator is electrically connected to the input end of the piezoelectric ceramic.

6. The optical comb frequency control system for an optically generated ultrastable microwave source according to claim 5, characterized in that: When the optical comb frequency control system includes an optical comb signal frequency adjustment loop, the optical comb signal includes any one of a carrier envelope phase shift frequency signal fceo, a repetition frequency signal fr or an optical beat frequency signal fbeat; The output end of the PID circuit is electrically connected to the input end of the electro-optical modulator, the output end of the piezoelectric ceramic is electrically connected to the input end of the phase detector, and the frequency control signal corresponding to the repetition frequency signal fr or the optical beat frequency signal fbeat is fed back to the electro-optical modulator and the piezoelectric ceramic for processing to adjust the frequency of the output repetition frequency signal fr or the optical beat frequency signal fbeat; or, The output end of the PID circuit is electrically connected to the input end of the pump driver, the output end of the gain medium is electrically connected to the input end of the phase detector, and the frequency control signal corresponding to the carrier-envelope phase-shifted frequency signal fceo is fed back to the pump driver and the gain medium processing to adjust the frequency of the output carrier-envelope phase-shifted frequency signal fceo.

7. The optical comb frequency control system for an optically generated ultrastable microwave source according to claim 5, characterized in that: When the optical comb frequency control system includes two optical comb signal frequency adjustment loops, the optical comb signal includes any one of a carrier envelope phase shift frequency signal fceo, a repetition frequency signal fr or an optical beat frequency signal fbeat; Wherein, in an optical comb signal frequency adjustment loop, the output end of the PID circuit is electrically connected to the input end of the electro-optic modulator, the output end of the piezoelectric ceramic is electrically connected to the input end of the phase detector, and the frequency control signal corresponding to the repetition frequency signal fr or the optical beat frequency signal fbeat is fed back to the electro-optic modulator and the piezoelectric ceramic for processing to adjust the frequency of the output repetition frequency signal fr or the optical beat frequency signal fbeat; In another optical comb signal frequency adjustment loop, the output end of the PID circuit is electrically connected to the input end of the pump driver, the output end of the gain medium is electrically connected to the input end of the phase detector, and the frequency control signal corresponding to the carrier-envelope phase-shifted frequency signal fceo is fed back to the pump driver and the gain medium processing to adjust the frequency of the output carrier-envelope phase-shifted frequency signal fceo.

8. A method for controlling the frequency of an optical comb for an optically generated ultrastable microwave source, characterized in that: Applicable to the optical comb frequency control system for a photogenerated ultrastable microwave source as described in any one of claims 1 to 7, the method comprising: Outputting optical comb signal; Detecting a phase difference between the current optical comb signal and a reference signal, and extracting the phase difference to obtain a phase detection signal; Converting the phase detection signal into a frequency control signal; The frequency of the output optical comb signal is adjusted according to the frequency control signal, and then the phase difference between the optical comb signal after the frequency adjustment and a reference signal is detected until the frequency of the adjusted optical comb signal is automatically locked with the frequency of the reference signal.

9. The optical comb frequency control method for a photogenerated ultrastable microwave source according to claim 8, characterized in that: The frequency difference between the optical comb signal and the reference signal is proportional to the slope of the phase detection signal, and the phase difference between the optical comb signal and the reference signal is proportional to the voltage of the phase detection signal.

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