A broadband frequency hopping low phase noise coupled optoelectronic oscillator

Abstract

The application provides a broadband frequency hopping low phase noise coupled optoelectronic oscillator, comprising: an active optical fiber ring cavity, an electro-optical feedback loop, a phase-locked loop and an optical fiber energy storage link; the active optical fiber ring cavity and the electro-optical feedback loop are connected through a common electro-optical intensity modulator and an optical coupler; the electro-optical feedback loop and the phase-locked loop are connected through a common voltage-controlled phase shifter; the phase-locked loop and the optical fiber energy storage link are connected through a common single-mode linear energy storage optical fiber; and the optical fiber energy storage link and the active optical fiber ring cavity are connected through a common polarization beam splitter. The application can enhance the robustness of the coupled optoelectronic oscillator, effectively improve the broadband frequency hopping capability of the optoelectronic oscillator, reduce the phase noise of the output frequency hopping microwave signal, and improve the long-term stability of the output frequency.

Description

Technical Field

[0001] This application relates to the field of communications, and more particularly to a broadband frequency-hopping low-phase-noise coupled optoelectronic oscillator. Background Technology

[0002] Microwave signal sources are core components of modern electronic systems, playing a crucial role in basic civilian fields such as personal mobile communications and high-precision radar. Traditional microwave sources rely on microwave oscillators for manufacturing, which severely limits their performance in terms of size, phase noise, and other aspects. Microwave frequency hopping technology is an important technique used in communications and radar. Frequency hopping refers to changing the information carrier frequency between a series of frequencies according to a unique frequency hopping code sequence. In communication systems, the use of frequency hopping improves network capacity and security; in radar, the time-varying frequency-hopping carrier signal greatly enhances the system's anti-interference and anti-tracking capabilities. Due to the limited speed and bandwidth of electronic circuits, electronic frequency hopping generators can produce microwave waveforms with relatively small frequency hopping ranges (less than GHz) and low frequency hopping speeds (on the order of kHz). However, for some applications, a frequency hopping range on the order of GHz is required.

[0003] Due to the high frequencies and wide bandwidths offered by modern photonics, microwave photonics technology provides a reliable solution for generating low-phase-noise broadband frequency-hopping microwave signals. The optoelectronic oscillator (OEO) is the most typical photogenerated microwave technology, capable of overcoming the electronic bottlenecks of traditional microwave sources and achieving extremely low phase-noise microwave signal output over a wide frequency range, with phase noise independent of the operating frequency band.

[0004] However, since the output frequency of an optoelectronic oscillator is determined by a narrowband RF filter in its structure, optoelectronic oscillators are typically designed to operate at a fixed frequency. When dynamic tuning is required, it is often difficult to guarantee characteristics such as low phase noise, high tuning rate, and high signal-to-noise ratio of the output signal. In other words, existing optoelectronic oscillators suffer from technical problems such as poor robustness, lack of broadband frequency hopping capability, high phase noise of the output frequency-hopping microwave signal, and poor stability of the frequency-hopping microwave signal output frequency. Summary of the Invention

[0005] In view of this, embodiments of this application provide a broadband frequency-hopping low-phase-noise coupled optoelectronic oscillator to eliminate or improve one or more defects existing in the prior art.

[0006] The first aspect of this application provides a broadband frequency-hopping low-phase-noise coupled opto-oscillator, which includes: an active fiber optic cavity, an electro-optic feedback loop, a phase-locked loop, and an optical fiber energy storage link; The active fiber optic cavity and the electro-optic feedback loop are connected by a shared electro-optic intensity modulator and optical coupler. The electro-optic feedback loop and the phase-locked loop are connected by a shared voltage-controlled phase shifter; The phase-locked loop and the optical fiber energy storage link are connected by a shared single-mode linear energy storage optical fiber. The fiber optic energy storage link and the active fiber optic ring cavity are connected by a shared polarization beam splitter.

[0007] In some embodiments of this application, the active fiber optic loop cavity is used to generate an optical carrier signal; The active fiber optic ring cavity includes: a cascaded optical amplifier, a first optical isolator, an optical bandpass filter, a polarization beam splitter, an optical coupler, an electro-optic intensity modulator, and a second optical isolator connected in sequence.

[0008] In some embodiments of this application, the cascaded optical amplifier comprises a semiconductor optical amplifier and an erbium-doped fiber amplifier connected in sequence; The semiconductor optical amplifier operates in the transparent gain region to suppress spontaneous emission noise and stimulated emission noise introduced by itself, reduce pulse jitter caused by supermode competition in the active fiber optic ring cavity, and widen the width of the transmitted pulse in the active fiber optic ring cavity. The erbium-doped fiber amplifier is used to amplify the optical signal input to the cascaded optical amplifier according to its own optical gain to obtain a first optical carrier signal. The first optical isolator is used to enable unidirectional transmission of the optical carrier signal; The optical bandpass filter is used to filter the first optical carrier signal according to a preset operating bandwidth range to obtain the second optical carrier signal; The polarization beam splitter is used to rotate the polarization state of the filtered second optical carrier signal by π / 2 to obtain the third optical carrier signal, and to receive the fourth optical carrier signal returned after the third optical carrier signal has been delayed and stored by the optical fiber energy storage link. The optical coupler is used to split the fourth optical carrier signal into a fifth optical carrier signal and a sixth optical carrier signal; The electro-optic intensity modulator is used to obtain a mode-locked pulse sequence based on the fifth optical carrier signal and the microwave signal input to the electro-optic feedback loop; The second optical isolator is used to enable unidirectional transmission of the mode-locked pulse sequence; In some embodiments of this application, the optical fiber energy storage link is used to perform time-delay energy storage on the second optical carrier signal; the optical fiber energy storage link includes: the polarization beam splitter, the single-mode linear energy storage fiber, and the Faraday rotator connected in sequence.

[0009] In some embodiments of this application, the single-mode linear energy storage fiber is used to perform time-delay energy storage on the third optical carrier signal.

[0010] In some embodiments of this application, the Faraday rotator is used to rotate the third optical carrier signal by π / 2 to obtain the fourth optical carrier signal, and to reflect the fourth optical carrier signal to the single-mode linear energy storage fiber and back to the polarization beam splitter.

[0011] In some embodiments of this application, the electro-optical feedback loop is used to feed back microwave signals and separated low-phase-noise microwave signals into the active optical fiber cavity; The electro-optic feedback loop includes: the optical coupler, the photodetector, the first low-noise amplifier, the YIG RF bandpass filter, the voltage-controlled phase shifter, the RF power divider, the second low-noise amplifier, and the electro-optic intensity modulator.

[0012] In some embodiments of this application, the photodetector is used to convert the sixth optical carrier signal into a first microwave signal; The first low-noise amplifier is used to amplify the first microwave signal to obtain a second microwave signal; The YIG radio frequency bandpass filter is used to filter the second microwave signal and tune the output frequency to obtain the third microwave signal. The voltage-controlled phase shifter is used to adjust the phase of the third microwave signal to obtain a fourth microwave signal; The radio frequency power divider is used to divide the fourth microwave signal into an identical fifth microwave signal, a target microwave signal, and a sixth microwave signal for locking with an external reference. The second low-noise amplifier is used to amplify the fifth microwave signal to obtain a seventh microwave signal, and to transmit the seventh microwave signal to the electro-optic intensity modulator.

[0013] In some embodiments of this application, the phase-locked loop is used to lock the output frequency of the broadband frequency-hopping low-phase-noise coupled opto-oscillator with an external reference source, thereby improving the long-term stability of the target microwave signal. The phase-locked loop includes: a frequency synthesizer, a mixer, and a parallel first PID branch and second PID branch connected in sequence; The frequency synthesizer is used to synthesize the frequency of a 10MHz crystal oscillator to obtain a reference frequency signal; The mixer is used to mix the sixth microwave signal output by the radio frequency power divider and the reference frequency signal output by the frequency synthesizer to obtain an error signal; and send the error signal to the first PID and the second PID.

[0014] In some embodiments of this application, the first PID branch includes a first PID and the voltage-controlled phase shifter connected in sequence; The second PID branch includes a second PID and the single-mode linear energy storage fiber connected in sequence; The first PID is used to transmit the error signal to the voltage-controlled phase shifter; The second PID is used to transmit the error signal to the fiber stretcher in the single-mode linear energy storage fiber.

[0015] This application provides a broadband frequency-hopping, low-phase-noise coupled optoelectronic oscillator, comprising: an active fiber optic cavity, an electro-optic feedback loop, a phase-locked loop, and an optical fiber energy storage link; the active fiber optic cavity and the electro-optic feedback loop are connected via a shared electro-optic intensity modulator and an optical coupler; the electro-optic feedback loop and the phase-locked loop are connected via a shared voltage-controlled phase shifter; the phase-locked loop and the optical fiber energy storage link are connected via a shared single-mode linear energy storage fiber; and the optical fiber energy storage link and the active fiber optic cavity are connected via a shared polarization beam splitter. This application can enhance the robustness of the coupled optoelectronic oscillator, effectively improve the broadband frequency-hopping capability of the optoelectronic oscillator, reduce the phase noise of the output frequency-hopping microwave signal, and improve the long-term stability of the output frequency.

[0016] Additional advantages, objectives, and features of this application will be set forth in part in the description which follows, and will in part become apparent to those skilled in the art upon review of the following description, or may be learned by practice of the application. The objectives and other advantages of this application can be realized and obtained by means of the structures specifically pointed out in the specification and drawings.

[0017] Those skilled in the art will understand that the purposes and advantages that can be achieved with this application are not limited to those specifically described above, and that the above and other purposes that this application can achieve will be more clearly understood from the following detailed description. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, do not constitute a limitation thereof. The components in the drawings are not drawn to scale but are merely for illustrating the principles of this application. For ease of illustration and description of certain parts of this application, corresponding portions in the drawings may be enlarged, i.e., may appear larger relative to other components in an exemplary device actually manufactured according to this application. In the drawings: Figure 1 This is a schematic diagram of the structure of a broadband frequency-hopping low phase noise coupled optoelectronic oscillator in one embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and their descriptions are used to explain this application, but are not intended to limit it.

[0020] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the structures and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0021] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0022] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0023] In the following description, embodiments of the present application will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar parts, or the same or similar steps.

[0024] The following examples will provide a detailed description.

[0025] This application provides a broadband frequency-hopping, low-phase-noise coupled opto-oscillator. See [link to previous document]. Figure 1 The broadband frequency-hopping low phase-noise coupled optoelectronic oscillator specifically includes the following components: Active fiber optic cavity, electro-optic feedback loop, phase-locked loop, and fiber optic energy storage link; The active fiber optic cavity and the electro-optic feedback loop are connected by a shared electro-optic intensity modulator and optical coupler. The electro-optic feedback loop and the phase-locked loop are connected by a shared voltage-controlled phase shifter; The phase-locked loop and the optical fiber energy storage link are connected by a shared single-mode linear energy storage optical fiber. The fiber optic energy storage link and the active fiber optic ring cavity are connected by a shared polarization beam splitter.

[0026] In some embodiments of this application, the active fiber optic loop cavity is used to generate an optical carrier signal and enhance the quality factor of the oscillator; The active fiber optic ring cavity includes: a cascaded optical amplifier (i.e., ...) connected in sequence. Figure 1 SOA and EDFA in the first optical isolator (i.e. Figure 1 ISO in the middle), optical bandpass filter (i.e. Figure 1The OBPF in the middle), the polarization beam splitter (i.e. Figure 1 PBS in the photocoupler, i.e. Figure 1 OC in the middle), the electro-optic intensity modulator (i.e. Figure 1 The second optical isolator (MZM) in the middle Figure 1 (ISO linked to MZM).

[0027] In some embodiments of this application, the cascaded optical amplifier includes semiconductor optical amplifiers (i.e., ...) connected in sequence. Figure 1 SOA in the middle) and erbium-doped fiber amplifier (i.e. Figure 1 EDFA in ( It should be noted that this application uses a cascaded optical amplifier to provide optical gain, and a polarization-maintaining bandpass filter to limit the operating bandwidth of the optical ring cavity.

[0028] Specifically, the "static point" working principle of the cascaded optical amplifier is as follows: by tuning the pre-semiconductor optical amplifier (SOA) of the cascaded optical amplifier into the transparent gain region, it can suppress the spontaneous emission noise and stimulated emission noise introduced by itself, reduce the pulse jitter caused by supermode competition in the active fiber optic ring cavity, and widen the width of the transmitted pulse in the active fiber optic ring cavity, thereby improving the locking bandwidth.

[0029] Therefore, based on the "quiet point" working principle of the cascaded optical amplifier described above, even if the RF filter has a wide bandwidth (e.g., tens of MHz) and a large frequency hopping range (e.g., several GHz), the high signal-to-noise ratio (SNR>85dB) of the output signal can still be maintained, and the output signal has low phase noise (<-135dBc / Hz@10kHz).

[0030] The erbium-doped fiber amplifier following the cascaded optical amplifier is used to amplify the optical signal input to the cascaded optical amplifier according to its own optical gain to obtain the first optical carrier signal.

[0031] The first optical isolator is used to enable unidirectional transmission of the optical carrier signal; The optical bandpass filter is used to filter the first optical carrier signal according to a preset operating bandwidth range to obtain the second optical carrier signal; The polarization beam splitter is used to rotate the polarization state of the filtered second optical carrier signal by π / 2 to obtain the third optical carrier signal, and to receive the fourth optical carrier signal returned after the third optical carrier signal has been delayed and stored by the optical fiber energy storage link. The optical coupler is used to split the fourth optical carrier signal into a fifth optical carrier signal and a sixth optical carrier signal; The electro-optic intensity modulator is used to obtain a mode-locked pulse sequence based on the fifth optical carrier signal and the microwave signal input to the electro-optic feedback loop; The second optical isolator is used to enable unidirectional transmission of the mode-locked pulse sequence; In some embodiments of this application, the optical fiber energy storage link is used to perform time-delay energy storage on the second optical carrier signal; The fiber optic energy storage link includes: the polarization beam splitter and the single-mode linear energy storage fiber (i.e., connected in sequence) Figure 1 (fiber in the middle), and Faraday rotating mirror (i.e. Figure 1 (FRM in the context).

[0032] In some embodiments of this application, the single-mode linear energy storage fiber is used to perform time-delay energy storage on the third optical carrier signal.

[0033] In some embodiments of this application, the Faraday rotator is used to rotate the third optical carrier signal by π / 2 to obtain the fourth optical carrier signal, and to reflect the fourth optical carrier signal to the single-mode linear energy storage fiber and back to the polarization beam splitter.

[0034] Specifically, the polarization state of the circulating light in the active fiber ring cavity is aligned with the slow axis of the fiber. After passing through the PBS, the polarization state is rotated by π / 2 and then enters the non-polarization-maintaining linear energy storage branch (i.e., the fiber energy storage link). The Faraday rotator at the end of the linear branch rotates the polarization state of the signal light by π / 2 and then reflects it back into the active fiber ring cavity through the single-mode linear energy storage fiber and the polarization beam splitter. This effectively eliminates the polarization disturbance problem caused by changes in the external environment and reduces the impact of fiber polarization noise.

[0035] In some embodiments of this application, the electro-optical feedback loop is used to feed back microwave signals and separated low-phase-noise microwave signals into the active optical fiber cavity; The electro-optic feedback loop includes: the optical coupler, the photodetector (i.e., Figure 1 PD in the first low-noise amplifier (i.e. Figure 1 LNA1), YIG RF bandpass filter (i.e. Figure 1 YIG Filter), voltage-controlled phase shifter (i.e. Figure 1 VPS), RF power divider (i.e. Figure 1 EC in the middle), the second low noise amplifier (i.e. Figure 1 LNA2 in the middle and the electro-optic intensity modulator.

[0036] In some embodiments of this application, the photodetector is used to convert the sixth optical carrier signal into a first microwave signal; Specifically, multiple longitudinal modes in the sixth optical carrier signal are beat-frequency in pairs by a photodetector to generate the first microwave signal.

[0037] The first low-noise amplifier is used to amplify the first microwave signal to obtain a second microwave signal; The YIG radio frequency bandpass filter is used to filter the second microwave signal and tune the output frequency to obtain the third microwave signal. Furthermore, existing photoelectric oscillators typically require long optical fibers to achieve high Q values ​​(quality factors) and generate low-phase-noise, high-quality microwave signals. This results in extremely tight signal spacing (Δν) from the photodetector (PD), where ω is the oscillation frequency determined by the pass frequency of the RF filter. To obtain stable oscillation, a narrowband RF filter is needed to select a single oscillation mode; the longer the optical fiber, the narrower the bandwidth of the RF filter required.

[0038] Therefore, the frequency hopping characteristics of the broadband frequency-hopping low-phase-noise coupled optoelectronic oscillator in this scheme are achieved through a broadband tunable YIG filter and RF loop delay matching. The center frequency of the YIG filter can be flexibly adjusted according to the driving voltage of the YIG filter, thereby adjusting the output frequency of the oscillator. Advanced YIG filter tuning rates can reach 12.5 MHz / μs, thus the oscillator designed in this scheme exhibits broadband fast frequency hopping (>10 GHz / ms) characteristics. In the COEO system, the operating frequency is discretely distributed in integer multiples of the FSR. Therefore, the resolution of the frequency-hopping signal is equal to the FSR of the fiber loop (<1 MHz), thus the oscillator in this scheme has a fine frequency hopping resolution of <1 MHz.

[0039] The voltage-controlled phase shifter is used to adjust the phase of the third microwave signal to obtain a fourth microwave signal; The radio frequency power divider is used to divide the fourth microwave signal into an identical fifth microwave signal, a target microwave signal, and a sixth microwave signal for locking with an external reference. The second low-noise amplifier is used to amplify the fifth microwave signal to obtain a seventh microwave signal, and to transmit the seventh microwave signal to the electro-optic intensity modulator.

[0040] In some embodiments of this application, the phase-locked loop is used to lock the output frequency of the broadband frequency-hopping low-phase-noise coupled opto-oscillator with an external reference source, thereby improving the long-term stability of the target microwave signal. The phase-locked loop includes: a frequency synthesizer, a mixer, and a parallel first PID branch and second PID branch connected in sequence; The frequency synthesizer is used to synthesize the frequency of a 10MHz crystal oscillator to obtain a reference frequency signal; The mixer is used to mix the sixth microwave signal output by the RF power divider and the reference frequency signal output by the frequency synthesizer to obtain an error signal; and send the error signal to the first PID (proportional-integral-derivative controller) and the second PID.

[0041] In some embodiments of this application, the first PID branch includes a first PID (i.e., ...) connected in sequence. Figure 1 PID1) and the voltage-controlled phase shifter; The second PID branch includes a second PID connected in sequence (i.e., Figure 1 PID2) and the single-mode linear energy storage fiber; The first PID is used to transmit the error signal to the voltage-controlled phase shifter; The second PID is used to transmit the error signal to the fiber stretcher in the single-mode linear energy storage fiber.

[0042] Therefore, a stable lock-in can be achieved through a phase-locked loop, thereby effectively reducing the frequency drift of the output microwave signal.

[0043] In summary, this application provides a broadband frequency-hopping, low-phase-noise coupled opto-oscillator, comprising: an active fiber optic cavity, a fiber optic energy storage link, an electro-optic feedback loop, and a phase-locked loop. By utilizing the tunable characteristics of the YIG filter in the electro-optic feedback loop, a broadband frequency-hopping microwave signal source can be realized; by expanding the locking bandwidth through the delay-matching design of the electro-optic feedback loop, the robustness of the coupled opto-oscillator can be improved; by designing the "static point" of the optical amplifier in the broadband frequency-hopping, low-phase-noise coupled opto-oscillator, a frequency-hopping signal with high side-mode rejection ratio and low phase noise can be generated; and by designing a multi-stage PID controller in the phase-locked loop, the generated microwave signal can be synchronized with an external reference source, achieving improved long-term frequency stability.

[0044] Those skilled in the art will understand that the exemplary components, systems, and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Whether implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application. When implemented in hardware, it can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. The programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave.

[0045] It should be clarified that this application is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of this application is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of this application.

[0046] In this application, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or in place of features of other embodiments.

[0047] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to the embodiments of this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A broadband frequency-hopping, low-phase-noise coupled optoelectronic oscillator, characterized in that, include: Active fiber optic cavity, electro-optic feedback loop, phase-locked loop, and fiber optic energy storage link; The active fiber optic cavity and the electro-optic feedback loop are connected by a shared electro-optic intensity modulator and optical coupler. The optical coupler is used to split the optical signal in the active fiber optic cavity into two paths, one of which is input to the electro-optic intensity modulator and the other of which is input to the electro-optic feedback loop. The electro-optic intensity modulator is used to obtain a mode-locked pulse sequence based on the fifth optical carrier signal transmitted by the optical coupler and the microwave signal input to the electro-optic feedback loop. The electro-optic feedback loop and the phase-locked loop are connected by a common voltage-controlled phase shifter; the electro-optic feedback loop includes a YIG radio frequency bandpass filter, which is used to adjust the center frequency by adjusting its driving voltage; the voltage-controlled phase shifter is used to perform phase adjustment on the microwave signal transmitted by the YIG radio frequency bandpass filter based on the error signal transmitted by the phase-locked loop to obtain an adjusted microwave signal and input it into the electro-optic feedback loop; The phase-locked loop and the optical fiber energy storage link are connected by a shared single-mode linear energy storage fiber, which is used to receive the error signal transmitted by the phase-locked loop and the optical signal transmitted by the active optical fiber ring cavity. The optical fiber energy storage link and the active optical fiber ring cavity are connected by a shared polarization beam splitter. The polarization beam splitter is used to couple the optical signal in the active optical fiber ring cavity to the optical fiber energy storage link and receive the optical signal returned by the optical fiber energy storage link.

2. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 1, characterized in that, The active fiber optic ring cavity is used to generate an optical carrier signal; The active fiber optic ring cavity includes: a cascaded optical amplifier, a first optical isolator, an optical bandpass filter, a polarization beam splitter, an optical coupler, an electro-optic intensity modulator, and a second optical isolator connected in sequence.

3. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 2, characterized in that, The cascaded optical amplifier comprises a semiconductor optical amplifier and an erbium-doped fiber amplifier connected in sequence; The semiconductor optical amplifier operates in the transparent gain region to suppress spontaneous emission noise and stimulated emission noise introduced by itself, reduce pulse jitter caused by supermode competition in the active fiber optic ring cavity, and widen the width of the transmitted pulse in the active fiber optic ring cavity. The erbium-doped fiber amplifier is used to amplify the optical signal input to the cascaded optical amplifier according to its own optical gain to obtain a first optical carrier signal. The first optical isolator is used to enable unidirectional transmission of the optical carrier signal; The optical bandpass filter is used to filter the first optical carrier signal according to a preset operating bandwidth range to obtain the second optical carrier signal; The polarization beam splitter is used to rotate the polarization state of the filtered second optical carrier signal by π / 2 to obtain the third optical carrier signal, and to receive the fourth optical carrier signal returned after the third optical carrier signal has been delayed and stored by the optical fiber energy storage link. The optical coupler is used to split the fourth optical carrier signal into a fifth optical carrier signal and a sixth optical carrier signal; The second optical isolator is used to enable unidirectional transmission of the mode-locked pulse sequence.

4. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 3, characterized in that, The optical fiber energy storage link is used to delay and store energy for the second optical carrier signal; the optical fiber energy storage link includes: the polarization beam splitter, the single-mode linear energy storage fiber and the Faraday rotator connected in sequence.

5. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 3, characterized in that, The single-mode linear energy storage fiber is used to store energy for delay of the third optical carrier signal.

6. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 4, characterized in that, The Faraday rotator is used to rotate the third optical carrier signal by π / 2 to obtain the fourth optical carrier signal, and to reflect the fourth optical carrier signal to the single-mode linear energy storage fiber and back to the polarization beam splitter.

7. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 3, characterized in that, The electro-optic feedback loop is used to feed back microwave signals and low phase noise microwave signals generated by separation into the active optical fiber cavity. The electro-optic feedback loop further includes: the optical coupler, the photodetector, the first low-noise amplifier, the voltage-controlled phase shifter, the radio frequency power divider, the second low-noise amplifier, and the electro-optic intensity modulator.

8. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 7, characterized in that, The photodetector is used to convert the sixth optical carrier signal into a first microwave signal; The first low-noise amplifier is used to amplify the first microwave signal to obtain a second microwave signal; The YIG radio frequency bandpass filter is used to filter the second microwave signal and tune the output frequency to obtain the third microwave signal. The voltage-controlled phase shifter is used to adjust the phase of the third microwave signal to obtain a fourth microwave signal; The radio frequency power divider is used to divide the fourth microwave signal into an identical fifth microwave signal, a target microwave signal, and a sixth microwave signal for locking with an external reference. The second low-noise amplifier is used to amplify the fifth microwave signal to obtain a seventh microwave signal, and to transmit the seventh microwave signal to the electro-optic intensity modulator.

9. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 8, characterized in that, The phase-locked loop is used to lock the output frequency of the broadband frequency-hopping low phase-noise coupled opto-oscillator with an external reference source, thereby improving the long-term stability of the target microwave signal. The phase-locked loop includes: a frequency synthesizer, a mixer, and a parallel first PID branch and second PID branch connected in sequence; The frequency synthesizer is used to synthesize the frequency of a 10MHz crystal oscillator to obtain a reference frequency signal; The mixer is used to mix the sixth microwave signal output by the radio frequency power divider and the reference frequency signal output by the frequency synthesizer to obtain an error signal; and send the error signal to the first PID and the second PID.

10. The broadband frequency-hopping low-phase-noise coupled opto-oscillator according to claim 9, characterized in that, The first PID branch includes a first PID and the voltage-controlled phase shifter connected in sequence; The second PID branch includes a second PID and the single-mode linear energy storage fiber connected in sequence; The first PID is used to transmit the error signal to the voltage-controlled phase shifter; The second PID is used to transmit the error signal to the fiber stretcher in the single-mode linear energy storage fiber.

Images