An optoelectronic oscillator usable for dual-frequency microwave pulse generation

Abstract

The application provides an optoelectronic oscillator which can be used for double-frequency microwave pulse generation and mainly comprises a laser, a polarization controller, a double-parallel Mach-Zehnder modulator, a single-mode optical fiber, an optoelectronic detector, an electric amplifier, an equivalent double-waveband filter and a microwave source; the equivalent double-waveband filter is obtained by connecting two narrowband filters in parallel and is used as a frequency selection device of the optoelectronic oscillator system; the microwave source is used for exciting double-frequency oscillation of the optoelectronic oscillator loop, and then the active mode-locked modulation is used for realizing loop gain modulation, changing the output signal form and then outputting a pulse signal; compared with a conventional pulse output optoelectronic oscillator, the optoelectronic oscillator has the advantages of simple structure and tunable double-frequency, and the output pulse has two center frequencies, so that the optoelectronic oscillator has good application in pulse Doppler radar and detection.

Description

Technical Field

[0001] This invention belongs to the field of signal generation and processing technology, and particularly relates to an optoelectronic oscillator that can be used for dual-frequency microwave pulse generation. Background Technology

[0002] Microwave pulse signals are commonly used in the field of detection. Due to their advantages in instantaneous energy and anti-interference, they have been widely applied in this field. Microwave pulses have become the primary signal in radar, short-range detection, and imaging. However, due to electronic limitations, there is still a lack of effective methods for generating high-frequency, low-phase-noise pulse signals. Microwave photonics, on the other hand, has significant advantages in generating wideband, high-quality microwaves. Currently, some research has been conducted on pulse signal generation based on microwave photonic methods, such as mode-locked lasers and active mode-locked optoelectronic oscillators.

[0003] Optical oscillators (OEOs) are characterized by generating high-frequency, low-phase-noise microwave signals and are widely used in signal generation and processing, radar, and other fields. Traditional OEO output signals are single-frequency signals with low phase noise. In 2020, a research team at Hangzhou Dianzi University proposed an OEO-based microwave pulse generation system. This system modulates the loop gain, causing periodic oscillations. Since the OEO loop is a positive feedback loop, no signal is output when the loop gain is below a certain threshold. This process is called active mode-locked modulation (AMDM), and the injected signal is called the active mode-locked signal. Therefore, the OEO, after periodic gain modulation, outputs a pulse signal. The repetition rate of the pulse signal is related to the frequency of the active mode-locked signal. To ensure phase consistency among the various mode components of the OEO loop, the frequency of the active mode-locked signal is generally an integer multiple of the OEO loop mode interval. Therefore, by changing the fiber length of the OEO loop and the frequency of the active mode-locked signal, the pulse repetition rate can be tuned.

[0004] Currently, the main research directions for OEO-based microwave pulse generation systems lie in the tuning of the microwave pulse center frequency, suppression of supermode noise in optoelectronic oscillators, direct modulation, and multi-center frequencies. In 2022, a research team from the Air Force Early Warning Academy designed an active mode-locked optoelectronic oscillator system based on the stimulated Brillouin effect, which can be used to generate microwave pulse systems with center frequencies of 5.23-24.58 GHz and a phase noise of -92.25 dBc / Hz@10 kHz. In the same year, a research team from Beijing Jiaotong University designed a microwave pulse generation system based on a dual-ring OEO with supermode noise suppression. In 2024, a research team from the University of Electronic Science and Technology of China designed a microwave pulse generation system based on a directly modulated laser, which has a more compact structure compared to traditional active mode-locked optoelectronic oscillators. In the same year, a research team from the Air Force Early Warning Academy realized a microwave pulse generation system with dual center frequencies using dual-frequency injection. However, all of the above dual-frequency microwave pulse systems are relatively complex. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an optoelectronic oscillator that can be used for generating dual-frequency microwave pulses. The output pulse has two center frequencies and has the advantages of simple structure and tunable dual-frequency operation.

[0006] An optoelectronic oscillator for generating dual-frequency microwave pulses includes a laser, a polarization controller, a dual-drive Mach-Zehnder modulator, a single-mode fiber, a photodetector, an equivalent dual-band filter, and a microwave source. The polarization controller is used to tune the polarization state of the laser signal output by the laser, so that the polarization state of the laser signal is parallel to the main axis of the dual-drive Mach-Zehnder modulator. The microwave source is used to output different microwave signals to the dual-drive Mach-Zehnder modulator. The dual-drive Mach-Zehnder modulator is used to modulate a laser signal parallel to its own main axis under the control of the microwave signal output from the microwave source and the dual-frequency filter signal output from the equivalent dual-band filter. The modulated optical signal output by the dual-drive Mach-Zehnder modulator is different depending on the microwave signal output from the microwave source. The single-mode optical fiber is used to transmit the modulated optical signal to the photodetector; The photodetector is used to convert the modulated optical signal into a modulated electrical signal; The equivalent dual-band filter is used to perform dual-band filtering on the modulated electrical signal to obtain a filtered signal. The filtered signal is different depending on the microwave signal output by the microwave source. When the microwave signal is 0, the filtered signal is a single-frequency sine wave signal. When the microwave signal is an excitation signal, the filtered signal is a dual-frequency continuous wave signal. When the microwave signal is both an excitation signal and an active mode-locked signal, the filtered signal is a dual-frequency pulse signal.

[0007] Furthermore, when the microwave signal output by the microwave source is 0, the modulated optical signal output by the dual-drive Mach-Zehnder modulator... as follows:

[0008] in, The intensity of the laser signal, The center frequency of the laser signal. The filtered signal is the output of the equivalent dual-band filter. For filtered signals The introduced phase shift, The phase shift introduced by the bias voltage provided by the external voltage source for the dual-drive Mach-Zehnder modulator. The external voltage source provides the bias voltage for the dual-drive Mach-Zehnder modulator. The half-wave voltage of the dual-drive Mach-Zehnder modulator; When the microwave signal output by the microwave source is an excitation signal m 1( t )= V 2cos( oh 2 t + f 2) The modulated optical signal output by the dual-drive Mach-Zehnder modulator as follows:

[0009] in, V 2 represents the amplitude of the excitation signal. oh 2 represents the angular frequency of the excitation signal. f 2 represents the phase shift of the excitation signal; When the microwave signal output by the microwave source is an excitation signal and an active mode-locking signal m 2( t )= V 2cos( oh 2 t + f 2)+ V 3cos( oh 3 t + f 3) The modulated optical signal output by the dual-drive Mach-Zehnder modulator as follows:

[0010] in, V 3 represents the amplitude of the active mode-locking signal. oh 3 represents the angular frequency of the active mode-locking signal. f 3 represents the phase shift of the active mode-locking signal.

[0011] Furthermore, an optoelectronic oscillator that can be used for dual-frequency microwave pulse generation also includes an electrical amplifier; The electrical amplifier is used to amplify the modulated electrical signal output by the photodetector, and then input the amplified modulated electrical signal into an equivalent dual-band filter.

[0012] Furthermore, an optoelectronic oscillator that can be used for dual-frequency microwave pulse generation also includes a directional coupler; The directional coupler is used to directionally couple the filtered signal output from the equivalent dual-band filter to the dual-drive Mach-Zehnder modulator.

[0013] Furthermore, the method for the photoelectric oscillator to acquire the dual-frequency pulse filter signal is as follows: A single-wavelength laser signal is output from a laser, and after passing through a polarization controller, the polarization state of the laser signal is parallel to the main axis of the dual-drive Mach-Zehnder modulator. Adjust the bias voltage of the dual-drive Mach-Zehnder modulator to make it operate at the quadrature transmission point; at this time, the filtered signal output by the equivalent dual-band filter is a single-frequency sine signal. Turn on the microwave source so that its output signal is the excitation signal, and make the filtered signal output by the equivalent dual-band filter a dual-frequency continuous wave signal; By adjusting the output signal of the microwave source to be an excitation signal and an active mode-locking signal, the filtered signal output by the equivalent dual-band filter becomes a dual-frequency pulse signal, and the entire optoelectronic oscillator generates a dual-frequency pulse signal.

[0014] Beneficial effects: This invention provides an optoelectronic oscillator for generating dual-frequency microwave pulses, mainly composed of a laser, a polarization controller, a dual parallel Mach-Zehnder modulator, a single-mode fiber, a photodetector, an electrical amplifier, an equivalent dual-band filter, and a microwave source. The equivalent dual-band filter is obtained by connecting two narrowband filters in parallel, serving as the frequency selection device for the optoelectronic oscillator system. The microwave source excites the dual-frequency oscillation of the optoelectronic oscillator loop, and then active mode-locked modulation is used to achieve loop gain modulation, changing the output signal form and thus outputting a pulse signal. Compared with traditional pulse-output optoelectronic oscillators, the optoelectronic oscillator of this invention has the advantages of simple structure and tunable dual-frequency operation. Furthermore, the output pulse of this invention has two center frequencies, making it suitable for applications in pulse Doppler radar and detection. Attached Figure Description

[0015] Figure 1 The present invention provides a system block diagram of a dual-frequency microwave pulse generation optoelectronic oscillator.

[0016] Figure 2 A schematic diagram of the transfer function curve of the equivalent dual-band filter provided by the present invention.

[0017] Figure 3 The frequency domain waveform of the signal output by the photoelectric oscillator provided by the present invention during free oscillation.

[0018] Figure 4 The frequency domain waveform of the output signal after injecting an excitation signal into the photoelectric oscillator provided by the present invention.

[0019] Figure 5 The time-frequency analysis diagram is generated after injecting an excitation signal into the photoelectric oscillator provided by this invention.

[0020] Figure 6 The frequency domain waveform of the output signal after injecting an excitation signal and an active mode-locking signal into the photoelectric oscillator provided by the present invention.

[0021] Figure 7 The time-frequency analysis diagram is generated after injecting an excitation signal and an active mode-locking signal into the photoelectric oscillator provided by this invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0023] This invention proposes an optoelectronic oscillator that can be used for dual-frequency microwave pulse generation, the system structure of which is as follows: Figure 1 As shown, it includes a laser, a polarization controller, a dual-drive Mach-Zehnder modulator, a single-mode fiber, a photodetector, an electrical amplifier, an equivalent dual-band filter, a directional coupler, and a microwave source. The laser is used to generate laser signals and send the laser signals into a single-mode optical fiber; The polarization controller is used to tune the polarization state of the laser signal output by the laser, so that the polarization state of the laser signal is parallel to the main axis of the dual-drive Mach-Zehnder modulator, thereby enabling the laser signal to obtain the highest modulation efficiency. The microwave source is used to output different microwave signals to the dual-drive Mach-Zehnder modulator. The dual-drive Mach-Zehnder modulator is used to modulate a laser signal parallel to its own main axis under the control of the microwave signal output from the microwave source and the dual-frequency filtered signal output from the equivalent dual-band filter. The modulated optical signal output by the dual-drive Mach-Zehnder modulator differs depending on the microwave signal output from the microwave source. It should be noted that the dual-drive Mach-Zehnder modulator has two RF input interfaces. One RF input interface is used to inject the loop feedback signal, which is also the dual-frequency filtered signal output from the equivalent dual-band filter. The other RF input interface is used to inject the microwave source output signal. The single-mode fiber is used to transmit the modulated optical signal to the photodetector; it should be noted that the single-mode fiber plays a role in increasing the length of the loop optical cavity and improving the quality factor of the output signal in the entire photoelectric oscillator. The photodetector is used to convert the modulated optical signal into a modulated electrical signal, thereby enabling the detection of the modulated optical signal; The electrical amplifier is used to amplify the modulated electrical signal output by the photodetector, and then the amplified modulated electrical signal is input into an equivalent dual-band filter to improve the loop gain and realize the output of the photoelectric oscillator. The equivalent dual-band filter is used to perform dual-band filtering on the amplified modulated electrical signal to obtain a filtered signal. The filtered signal is different depending on the microwave signal output by the microwave source. When the microwave signal is 0, the filtered signal is a single-frequency sine wave signal; when the microwave signal is an excitation signal, the filtered signal is a dual-frequency continuous wave signal; and when the microwave signal is both an excitation signal and an active mode-locking signal, the filtered signal is a dual-frequency pulse signal. In other words, the microwave source output has three cases: the first is no output signal; the second is only an output excitation signal to excite the loop to generate dual-frequency oscillation; and the third is simultaneous output of the excitation signal and the active mode-locking signal for active mode-locking modulation of the loop. The directional coupler is used to directionally couple the filtered signal output from the equivalent dual-band filter to the dual-drive Mach-Zehnder modulator.

[0024] It should be noted that the equivalent dual-band filter consists of two bandpass filters, a 50:50 power divider, and a combiner. The modulated signal enters from the power divider, is evenly distributed, and then enters the two parallel bandpass filters. The signals are then combined in the combiner after passing through the outputs of the bandpass filters. In other words, as... Figure 2 As shown, the equivalent dual-band filter can be used to filter loop microwave signals, and only signals within the passbands of the two bandpass filters can pass through.

[0025] The principle of the photoelectric oscillator provided by this invention for acquiring dual-frequency pulse filtered signals is as follows: The laser signal output by the laser can be represented as: ; The laser signal enters a dual-drive Mach-Zehnder modulator for intensity modulation. Due to the positive feedback characteristic of the photoelectric oscillator, assuming that the feedback signal received at port ① of the dual-drive Mach-Zehnder modulator is s(t), and port ② does not inject a signal, that is, the microwave signal output by the microwave source is 0, then the output signal of the Mach-Zehnder modulator is... It can be represented as:

[0026] in, The intensity of the laser signal, The center frequency of the laser signal. The filtered signal is the output of the equivalent dual-band filter. For filtered signals The introduced phase shift, The phase shift introduced by the bias voltage provided by the external voltage source for the dual-drive Mach-Zehnder modulator. The external voltage source provides the bias voltage for the dual-drive Mach-Zehnder modulator. The half-wave voltage of the dual-drive Mach-Zehnder modulator; At this point, the output signal of the dual-drive Mach-Zehnder modulator is transmitted through a long optical fiber and finally beats in the photodetector. The photodetector signal can be represented as:

[0027] Therefore, when no signal is injected into port ②, the microwave signal of the entire optoelectronic oscillator loop oscillates stably.

[0028] Because the OEO loop gain of the optoelectronic oscillator is limited, when the microwave signal received at port ② of the dual-drive Mach-Zehnder modulator is... m 1( t )= V 2cos( oh 2 t + f 2), where the frequency of the signal is... oh 2 equals the difference in center frequencies between the two narrowband bandpass filters in the equivalent dual-band filter, so the modulated optical signal output by the dual-drive Mach-Zehnder modulator at this time is... It can be represented as:

[0029] in, V 2 represents the amplitude of the excitation signal. oh 2 represents the angular frequency of the excitation signal. f 2 represents the phase shift of the excitation signal; the modulated optical signal, after transmission, undergoes beat frequency measurement in the photodetector, and the photodetector signal can be expressed as:

[0030] Where k1, k2, and k3 are intensity coefficients, which are fixed constants representing the relative intensity relationships between different frequencies. The signal is then filtered using an equivalent dual-band filter. Due to the dual-band pass characteristic, the output signal of the equivalent dual-band filter is a dual-frequency signal, i.e., the frequency is... f 1 and f 2 (i.e., | oh 1- ohThe signal (2 / 2π) is continuously amplified at port ① of the dual-drive Mach-Zehnder modulator, thus converting the loop from a single-frequency oscillation to a dual-frequency oscillation.

[0031] When the output of the microwave source is further changed, so that its injected signal is m 2(t)= V 2cos( oh 2 t + f 2)+ V 3cos( oh 3 t + f 3) At this time, the modulated optical signal output by the dual-drive Mach-Zehnder modulator for:

[0032] in, V 3 represents the amplitude of the active mode-locking signal. oh 3 represents the angular frequency of the active mode-locking signal. f 3 represents the phase shift of the active mode-locked signal; after transmission through a long optical fiber, the beat frequency at the photodetector can be obtained as follows:

[0033] Therefore, this invention can first output dual-frequency microwave signals, and then change the output state of the microwave source so that the output signal of port ② is... m 2( t )= m 1( t )+ m aml ( t ),in m aml ( t This is called an active mode-locked signal, and can be represented as... m aml ( t )= V 3( oh 3 t + f 3), V 3 represents the amplitude of the signal. oh 3 represents the angular frequency of the signal, which is related to the loop delay and can usually be expressed as... oh 3 = 2π / τ represents the loop delay of the entire optoelectronic oscillator system. When an active mode-locking signal is introduced, the loop gain of the optoelectronic oscillator is modulated. Since the optoelectronic oscillator is a positive feedback loop, when the gain is less than a certain threshold, the loop has no output. Therefore, the loop output signal is converted from a continuous wave to a pulse wave.

[0034] Furthermore, the method for the photoelectric oscillator to acquire the dual-frequency pulse filter signal is as follows: By using a laser to output a single-wavelength laser signal, the polarization state of the laser signal is parallel to the main axis of the dual-drive Mach-Zehnder modulator after passing through a polarization controller. This optical signal will obtain the maximum modulation efficiency in the dual-drive Mach-Zehnder modulator. Adjust the bias voltage of the dual-drive Mach-Zehnder modulator to make it work at the quadrature transmission point; at this time, the optoelectronic oscillator is in a single-mode oscillation state, and the filtered signal output by the equivalent dual-band filter is a single-frequency sine signal, which is single-frequency in the frequency domain, and the side modes are suppressed. Turn on the microwave source so that its output signal is the excitation signal. m 1( t )= V 2cos( oh 2 t + f 2) This makes the filtered signal output by the equivalent dual-band filter a dual-frequency continuous wave signal, where... oh 2 = 2π f Δ , f Δ It is the frequency difference between the two bandpass filters; Adjust the gain of the electrical amplifier in the system so that the output signal is in the form of a dual-frequency continuous wave; Adjust the microwave source output signal to an excitation signal and an active mode-locking signal. m 2( t )= m 1( t )+ m aml ( t This transforms the filtered signal output by the equivalent dual-band filter from a dual-frequency continuous wave signal into a dual-frequency pulse signal, thus enabling the entire optoelectronic oscillator to generate a dual-frequency pulse signal.

[0035] The performance results of the photoelectric oscillator provided by this invention are as follows: Figure 3~Figure 7 As shown. The experimental parameters for this test are as follows: the laser output power is 12dBm, the 3dB bandwidth of the dual-drive Mach-Zehnder modulator is 40GHz, the single-mode fiber length is 1km, the 3dB bandwidth of the photodetector is 33GHz, the output bandwidth of the electrical amplifier is 20GHz, and the gain is 20dBmz.

[0036] Figure 3 This demonstrates the single-frequency oscillation of the loop when the microwave source has no output. When an excitation signal is injected into the microwave source, the output signal exhibits a dual-frequency spectrum. The output signal is sampled and analyzed to obtain its time-domain signal, and then subjected to time-frequency analysis, such as... Figure 4 and Figure 5As shown, the output signal is a dual-frequency continuous wave. Further, by changing the microwave source output signal and performing active mode-locked modulation on the system, the output signal can be obtained. Figure 6 The time-domain spectrum of the output signal shows that it is in pulse form. Time-frequency analysis yields... Figure 7 This further proves the frequency component composition of the output pulse signal.

[0037] In summary, this invention proposes an optoelectronic oscillator for generating dual-frequency microwave pulses. This oscillator mainly consists of a laser, a polarization controller, a dual parallel Mach-Zehnder modulator, a single-mode fiber, a photodetector, an electrical amplifier, an equivalent dual-band filter, and a microwave source. The equivalent dual-band filter enables the output of dual-frequency continuous wave signals, with the center frequencies of the two signals falling within the passbands of the two narrowband filters. The conversion from single-frequency to dual-frequency is due to microwave source injection and excitation, resulting in a fixed phase relationship between the two signals. After stable loop oscillation, an active mode-locked signal is injected, transforming the output signal from a continuous signal to a pulse signal. Because the phase relationship is fixed, the time-domain signal resulting from the superposition of the two frequency components within each pulse cycle remains unchanged. Compared to other structures, the optoelectronic oscillator proposed in this invention has a fixed phase relationship between the dual-frequency components, offering advantages such as simple structure and tunable dual-frequency operation. It has promising applications in pulse Doppler radar and detection.

[0038] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A photoelectric oscillator for generating dual-frequency microwave pulses, characterized in that, It includes lasers, polarization controllers, dual-drive Mach-Zehnder modulators, single-mode optical fibers, photodetectors, electrical amplifiers, equivalent dual-band filters, and microwave sources; The polarization controller is used to tune the polarization state of the laser signal output by the laser, so that the polarization state of the laser signal is parallel to the main axis of the dual-drive Mach-Zehnder modulator. The microwave source is used to output different microwave signals to the dual-drive Mach-Zehnder modulator. The dual-drive Mach-Zehnder modulator is used to modulate a laser signal parallel to its own main axis under the control of the microwave signal output from the microwave source and the dual-frequency filter signal output from the equivalent dual-band filter. The modulated optical signal output by the dual-drive Mach-Zehnder modulator is different depending on the microwave signal output from the microwave source. The single-mode optical fiber is used to transmit the modulated optical signal to the photodetector; The photodetector is used to convert the modulated optical signal into a modulated electrical signal; The electrical amplifier is used to amplify the modulated electrical signal output by the photodetector, and then input the amplified modulated electrical signal into an equivalent dual-band filter. The equivalent dual-band filter is used to perform dual-band filtering on the amplified modulated electrical signal to obtain a filtered signal. The equivalent dual-band filter consists of two bandpass filters, a 50:50 power divider, and a combiner. After entering the power divider, the modulated electrical signal is evenly distributed and enters the two parallel bandpass filters respectively. Then, the signals are combined in the combiner through the output of the bandpass filters. At the same time, the filtered signal is different depending on the microwave signal output by the microwave source. When the microwave signal is 0, the filtered signal is a single-frequency sine wave signal; when the microwave signal is an excitation signal, the filtered signal is a dual-frequency continuous wave signal; and when the microwave signal is both an excitation signal and an active mode-locked signal, the filtered signal is a dual-frequency pulse signal. When the microwave signal output by the microwave source is 0, the modulated optical signal output by the dual-drive Mach-Zehnder modulator is... as follows: in, The intensity of the laser signal, The center frequency of the laser signal. The filtered signal is the output of the equivalent dual-band filter. For filtered signals The introduced phase shift, The phase shift introduced by the bias voltage provided by the external voltage source for the dual-drive Mach-Zehnder modulator. The external voltage source provides the bias voltage for the dual-drive Mach-Zehnder modulator. The half-wave voltage of the dual-drive Mach-Zehnder modulator; When the microwave signal output by the microwave source is an excitation signal m 1( t )= V 2cos( ω 2 t + φ 2) The modulated optical signal output by the dual-drive Mach-Zehnder modulator as follows: in, V 2 represents the amplitude of the excitation signal. ω 2 represents the angular frequency of the excitation signal. φ 2 represents the phase shift of the excitation signal. Represents microwave signal m 1( t The phase shift of the optical carrier signal caused by this; When the microwave signal output by the microwave source is an excitation signal and an active mode-locking signal m 2( t )= V 2cos( ω 2 t + φ 2)+ V 3cos( ω 3 t + φ 3) The modulated optical signal output by the dual-drive Mach-Zehnder modulator as follows: in, V 3 represents the amplitude of the active mode-locking signal. ω 3 represents the angular frequency of the active mode-locking signal. φ 3 represents the phase shift of the active mode-locked signal. Represents microwave signal m 2( t This causes phase shift in the optical carrier signal.

2. The photoelectric oscillator for dual-frequency microwave pulse generation as described in claim 1, characterized in that, It also includes directional couplers; The directional coupler is used to directionally couple the filtered signal output from the equivalent dual-band filter to the dual-drive Mach-Zehnder modulator.

3. A photoelectric oscillator for generating dual-frequency microwave pulses as described in claim 1, characterized in that, The method for acquiring the dual-frequency pulse filter signal using the photoelectric oscillator is as follows: A single-wavelength laser signal is output from a laser, and after passing through a polarization controller, the polarization state of the laser signal is parallel to the main axis of the dual-drive Mach-Zehnder modulator. Adjust the bias voltage of the dual-drive Mach-Zehnder modulator to make it work at the quadrature transmission point; at this time, the filtered signal output by the equivalent dual-band filter is a single-frequency sine signal. Turn on the microwave source so that its output signal is the excitation signal, and make the filtered signal output by the equivalent dual-band filter a dual-frequency continuous wave signal; By adjusting the output signal of the microwave source to be an excitation signal and an active mode-locking signal, the filtered signal output by the equivalent dual-band filter becomes a dual-frequency pulse signal, and the entire optoelectronic oscillator generates a dual-frequency pulse signal.

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