Broadband tunable optoelectronic oscillator with high stability and signal generation method thereof

Abstract

The application discloses a kind of broadband tunable optoelectronic oscillator systems with high stability, belong to microwave photonics field, including sequentially connected broadband light source, optical coupler, optical variable delay line, double-input MZM, optical fiber amplifier, optical circulator and two ends are connected Bragg grating and DP-RDLs respectively, single-mode optical fiber, photodetector, electrical amplifier and double-input MZM form positive feedback loop.The core of system will FIR filter and IIR filter fusion form a cascaded MPF.Wherein, FIR filter is by broadband light source, double-input MZM, optical variable delay line, Bragg grating and photodetector MPF structure;IIR filter is DP-RDLs form.The application utilizes FIR filter to complete preliminary mode selection and broadband tuning function, and combines IIR filter to enhance mode selection and improve stability, and then obtain frequency stable and broadband tunable optoelectronic oscillator system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave photonics, in particular to a wideband tunable optoelectronic oscillator with high stability and a signal generation method thereof. BACKGROUND

[0002] As a microwave generation technology, the physical mechanism of the optoelectronic oscillator (OEO) is to convert continuous light into a microwave signal with high spectral purity, high stability and high Q value by using optoelectronic positive feedback loop and optical processing technology, which can be applied to signal processing, sensors, radio over fiber systems (RoF), radar and modern instruments and other related fields. The mainstream framework of its structure is a positive feedback loop composed of an electro-optic modulator, a fiber energy storage device, a photodetector (PD), an electrical amplifier (EA) and an electrical bandpass filter (EBPF), and a laser source.

[0003] The initial design of the optoelectronic oscillator mainly focuses on the suppression of side modes and low phase noise. The selection of the oscillation mode of the system is mostly realized by an electrical bandpass filter. In recent years, with the continuous improvement of application requirements, tunable optoelectronic oscillators have emerged. The filter device used in the traditional system, i.e. the electrical bandpass filter, limits the frequency tuning range of the optoelectronic oscillator due to its fixed center frequency and narrow bandwidth characteristics, and cannot realize wide-range tuning. Therefore, the microwave photonic filter (MPF) can be used to replace the electrical bandpass filter to realize the filtering and wideband tuning functions of the optoelectronic oscillator due to its wide tuning range and anti-electromagnetic interference advantages. Many scholars at home and abroad have carried out corresponding researches, mainly including microwave photonic filters based on stimulated Brillouin scattering effect, microwave photonic filters based on phase-shifted fiber Bragg grating (PS-FBG) and microwave photonic filters based on dispersion effect.

[0004] By incorporating the microwave photonic filter based on stimulated Brillouin scattering effect into the optoelectronic oscillator, wideband tuning of the oscillation frequency can be realized by adjusting the wavelength of the signal light or the pump light. However, due to the interaction between the externally injected pump light and the signal light, the stability of the output signal is limited, and the frequency drift is in the order of tens of MHz. In addition, the introduction of double laser sources increases the cost of the system.

[0005] The microwave photonic filter based on phase-shifted Bragg grating is integrated into the optoelectronic oscillator, and the wideband tuning of the oscillation frequency can be realized by adjusting the wavelength of the laser source. However, the poor stability of the tunable laser makes the optoelectronic oscillator prone to frequency deviation effect, and the frequency drift is in the order of tens of kHz.

[0006] The microwave photonic filter based on dispersion effect is integrated into the optoelectronic oscillator, and the wideband tuning of the oscillation frequency can be realized by adjusting the parameters of an optical device in the system (such as the polarization state of the polarization controller, the delay of the optical variable delay line or the DC bias of the electro-optic modulator). However, there is still a frequency deviation effect of 10 kHz and above. SUMMARY

[0007] The present application aims to overcome the problems of the prior art and provide a wideband tunable optoelectronic oscillator with high stability and a signal generation method thereof.

[0008] The present application aims to overcome the problems of the prior art and provide a wideband tunable optoelectronic oscillator with high stability and a signal generation method thereof.

[0009] The optical coupling device and the double-input Mach-Zehnder modulator are provided with an optical variable delay line in the connection optical path, and the wideband light source, the double-input Mach-Zehnder modulator, the optical variable delay line and the Bragg grating form a microwave photonic filter based on dispersion effect.

[0010] In an example, the wideband light source is a rectangular wideband light source.

[0011] In an example, the rectangular wideband light source comprises an amplified spontaneous emission source and an optical bandpass filter connected in sequence.

[0012] In an example, the upper output end of the optical coupling device is connected to the upper input optical port of the double-input Mach-Zehnder modulator through the optical variable delay line to form an upper connection arm, and the lower output end of the optical coupling device is connected to the lower input optical port of the double-input Mach-Zehnder modulator to form a lower connection arm, and the optical variable delay line provides variable delay difference for the upper and lower connection arms.

[0013] In an example, the delay of the optical variable delay line is adjusted to make the optoelectronic oscillator have a wideband tuning range of 6.1 GHz to 11.98 GHz.

[0014] In an example, the Bragg grating is a linearly chirped Bragg grating.

[0015] In an example, the optical amplifier is an erbium-doped optical fiber amplifier.

[0016] In an example, the electrical amplifier is a radio frequency amplifier.

[0017] In an example, the microwave photonic filter is a finite impulse response (FIR) filter.

[0018] The application also includes a signal generation method of a broadband tunable optoelectronic oscillator with high stability, comprising the following steps:

[0019] A broadband light source generates an optical signal;

[0020] The optical signal is split into two by an optical coupler, the upper branch optical signal is transmitted to the upper input optical port of the double-input Mach-Zehnder modulator after delay processing by the optical variable delay line, the lower branch optical signal is directly transmitted to the lower input optical port of the double-input Mach-Zehnder modulator, and then the oscillation signal is modulated;

[0021] The modulated signal is amplified by the optical fiber amplifier and enters the Bragg fiber through the optical circulator;

[0022] The optical signal output from the Bragg fiber is transmitted to the infinite impulse response filter formed based on the double-parallel circulatory delay line, and then the optical signal is transmitted to the photodetector through the single-mode optical fiber, and the optical signal is converted into an electrical signal;

[0023] The electrical signal is amplified and transmitted to the radio frequency input end of the double-input Mach-Zehnder modulator to form an oscillation, and finally a high-stability, broadband tunable microwave signal is output.

[0024] It should be further pointed out that the technical features corresponding to the above examples can be combined or replaced to form new technical solutions.

[0025] Compared with the prior art, the application has the following beneficial effects:

[0026] 1. In an example, the application fuses the microwave photonic filter (FIR filter) based on the dispersion effect and the infinite impulse response filter (IIR filter) to form a cascade microwave photonic filter (MPF). The FIR filter completes the coarse selection of the oscillation mode and the wide-range tuning function, and the IIR filter completes the fine selection of the oscillation mode.

[0027] By adjusting the delay difference of the optical variable delay line in the FIR filter, the initial selection of the oscillation mode and the tuning of the oscillation frequency are completed, and the tuning range is large; the IIR filter

[0028] 2. In an example, the IIR filter formed by dual-input RDLs is used to further select the oscillation mode and improve the mode selection ability, and to greatly enhance the system stability. BRIEF DESCRIPTION OF DRAWINGS

[0029] The specific embodiments of the present application will be further described with the following detailed description and drawings, wherein the same reference numerals refer to the same or similar elements throughout. The illustrative embodiments of the present application and the descriptions thereof are presented for the purpose of explanation and not of limitation, as to the present application.

[0030] Figure 1 Model block diagram of the optoelectronic oscillator in the preferred example of the present application;

[0031] Fig. 2(a) and Fig. 2(b) are frequency response diagrams of the cascaded MPF in the preferred example;

[0032] Fig. 3(a) and Fig. 3(b) are microwave signal spectrum diagrams of the optoelectronic oscillator with an oscillation frequency of 7.48 GHz in the preferred example;

[0033] Fig. 4(a) and Fig. 4(b) are comparative diagrams of the stability of the oscillation signal with or without the dual-input RDLs in the preferred example;

[0034] Figure 5 Fig. 5 is a diagram of the phase noise of the microwave signal with an oscillation frequency of 7.48 GHz of the optoelectronic oscillator in the preferred example;

[0035] Fig. 6(a) is a superimposed diagram of the different microwave signal spectrum diagrams corresponding to the output of the optoelectronic oscillator in the preferred example by adjusting the OVDL;

[0036] Fig. 6(b) is a diagram of the phase noise of the different microwave signals output by the optoelectronic oscillator in the preferred example at a frequency offset of 10 kHz.

[0037] In the figures: BOS: broadband light source; OC: optical coupler; OVDL: optical variable delay line; Dual-input MZM: dual-input Mach-Zehnder modulator; EDFA: erbium-doped fiber amplifier; LCFBG: linearly chirped fiber Bragg grating; RDL: recirculating delay line; DP-RDLs: dual-input recirculating delay lines; SMF: single-mode fiber; PD: photodetector; EA: electrical amplifier. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0039] In the description of the present application, it should be noted that the directions or positional relationships indicated by "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like are based on the directions or positional relationships described in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the ordinal numbers (for example, "first and second", "first to fourth", etc.) are used to distinguish objects, and are not limited to the order, and cannot be understood as indicating or implying relative importance.

[0040] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, "mounting", "connection" and "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrated connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0041] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0042] In an example, a wideband tunable optoelectronic oscillator with high stability is realized by cascading microwave photonic filters (MPF) to realize a stable wideband tunable optoelectronic oscillator (OEO), and specifically, a finite impulse response (FIR) filter and an infinite impulse response (IIR) filter are fused to form a cascaded MPF.

[0043] The FIR filter is a MPF based on dispersion effect, which is constructed by a broadband light source, a double-input MZM, an optical variable delay line, a Bragg grating and a photodetector, and is used to complete coarse selection and wide-range tuning of the oscillation mode; the IIR filter is formed by double parallel cyclic delay lines, and is used to complete fine selection of the oscillation mode and enhance the stability of the system. The FIR filter and the IIR filter are cascaded and integrated into an existing optoelectronic oscillator. By simply adjusting the delay of the variable delay line in the FIR filter and changing the delay difference of the double-connection arms at the input end of the double-input MZM, the center frequency of the cascaded MPF can be shifted, and the wideband tuning function of the OEO oscillation frequency can be realized.

[0044] The present application will now be described in detail. A wideband tunable optoelectronic oscillator with high stability comprises a wideband light source, an optical coupler (OC1), an optical variable delay line, a dual-input MZM, an optical fiber amplifier, an optical circulator, a Bragg grating as a dispersion device, and an infinite impulse response filter based on a double parallel circulatory delay line. The infinite impulse response filter is connected to the RF input of the dual-input MZM via a single-mode fiber, a photodetector, and an electrical amplifier to form an optoelectronic positive feedback loop.

[0045] The working principle of the optoelectronic oscillator in this example is as follows:

[0046] The wideband light source generates an optical signal, which is split into two by the optical coupler (OC1). The upper branch of the optical signal is transmitted to the upper input optical port of the dual-input MZM after being delayed by the optical variable delay line, and the lower branch of the optical signal is directly transmitted to the lower input optical port of the dual-input MZM to modulate the oscillation signal. The modulated signal is amplified by the optical fiber amplifier and then enters the Bragg fiber as a dispersion device through the optical circulator. The optical signal output by the Bragg fiber is then transmitted to the infinite impulse response filter and to the photodetector via a single-mode fiber to convert the optical signal into an electrical signal. The electrical signal is transmitted to the RF input of the dual-input MZM after being amplified by the amplifier to compensate for the loop loss and form an oscillation. Preferably, an electrical coupler is connected to the output of the electrical amplifier to extract the microwave signal.

[0047] In one example, the wideband light source is a rectangular wideband light source. More specifically, the rectangular wideband light source comprises an amplified spontaneous emission (ASE) source and an optical bandpass filter (OBPF) connected in sequence.

[0048] In one example, the upper output end of the optical coupler (OC1) is connected to the upper input optical port of the dual-input MZM via the optical variable delay line to form an upper connection arm, and the lower output end of the optical coupler (OC1) is connected to the lower input optical port of the dual-input MZM to form a lower connection arm. The optical variable delay line provides a variable delay difference for the upper and lower connection arms.

[0049] In one example, by adjusting the delay of the optical variable delay line, the optoelectronic oscillator can obtain a wideband tuning range of 6.1 GHz to 11.98 GHz.

[0050] In one example, the Bragg grating is a linearly chirped Bragg grating to constitute an MPF based on the dispersion effect.

[0051] In one example, the infinite impulse response filter is an infinite impulse response filter based on dual parallel cyclic delay lines (DP-RDLs). Specifically, the infinite impulse response filter includes a first cyclic delay line and a second cyclic delay line. The first cyclic delay line (RDL1) and the second cyclic delay line (RDL2) are connected in parallel via a third optical coupler (OC3). The first cyclic delay line is connected to one end of an optical circulator via a second optical coupler (OC2).

[0052] In one example, the electrical amplifier is an RF amplifier used to compensate for loop attenuation loss.

[0053] In one example, the microwave photonic filter is an FIR filter.

[0054] Combining the above examples yields preferred examples of the present invention, such as... Figure 1 As shown, the optoelectronic oscillator at this time includes a broadband light source, an optical coupler, an optical variable delay line, a dual-input MZM, an erbium-doped fiber amplifier, and an optical circulator connected in sequence. The other two ends of the optical circulator are connected to a dispersive device, a Bragg grating, and dual parallel cyclic delay lines (DP-RDLs), respectively. The dual parallel cyclic delay lines are connected to the RF input of the dual-input MZM via a single-mode fiber, a photodetector, and an RF amplifier, forming a positive feedback loop. The core of the optoelectronic oscillator lies in fusing a finite impulse response (FIR) filter and an infinite impulse response (IIR) filter to form a cascaded microwave photonic filter (MPF). The FIR filter is an MPF ​​based on the dispersion effect constructed from a broadband light source, a dual-input MZM, an optical variable delay line, a Bragg grating, and a photodetector; the IIR filter is formed by dual parallel cyclic delay lines. In a preferred example, the operating principle of the optoelectronic oscillator is as follows:

[0055] The amplified spontaneous emission source is shaped into a rectangular broadband light source using an optical bandpass filter (OBPF), and then split into two optical signals via an optical coupler (OC1) and transmitted to a dual-input MZM to modulate the feedback oscillation signal. Here, an OVDL is introduced into the upper connecting arm at the input of the dual-input MZM to provide a delay difference between the two optical signals. After modulation, the signal is amplified by an EDFA and then enters a dispersive element LCFBG through an optical circulator. It is then transmitted sequentially through an optical circulator to DP-RDLs and a single-mode fiber, and then enters a photodetector (PD) to recover the microwave signal. After the loop loss is compensated by an electrical amplifier, the signal is fed back to the RF input of the dual-input MZM to generate oscillation. Finally, the microwave signal is output from the output of the electrical amplifier.

[0056] First, we analyze the FIR filter. Assume the oscillation signal V fed back from the dual-input MZM RF input is... in (t)=Vm cos(2πω m t), where V m and ω m are the amplitude and angular frequency of V in (t), respectively. The frequency response of the FIR filter can be obtained as follows:

[0057]

[0058] where χ is the accumulated dispersion value of the LCFBG; Δτ is the delay difference between the upper and lower arms at the input end of the 2x1MZM; and is the power spectrum of the BOS. is the transmission power attenuation function caused by dispersion under the limited spectrum width of the BOS, which can be expressed as follows:

[0059]

[0060] Due to the combined action of the ASE and the OBPF, the wideband light source forms a rectangular spectrum, and thus can be expressed as follows:

[0061]

[0062] where v is a constant; ω0 is the central angular frequency of the spectrum of the BOS; and ∈ is the spectrum width of the BOS. Substituting equation (3) into equation (2), we obtain:

[0063]

[0064] Substituting equation (4) into equation (1), we obtain:

[0065]

[0066] According to equation (5), we know that is a sinc function, which corresponds to a FIR filter. The peak point needs to satisfy ω m ± Δτ / χ = 0, and thus the peak point angular frequency can be obtained as follows:

[0067]

[0068] Next, the IIR filter is analyzed. The structure of the IIR filter is composed of two RDLs in cascade, that is, DP-RDLs. Without considering the transmission loss, the frequency response of the IIR filter can be expressed as follows:

[0069]

[0070] where κ1 and κ2 represent the coupling coefficients of OC2 and OC3, respectively; and Z i = exp(jω m τi ), τ i is the delay of the i th RDL loop. Further, the peak angular frequency of the IIR filter can be obtained as

[0071]

[0072] where M, N, L are all integers. After the fusion processing of the FIR filter and the IIR filter, the corresponding cascade MPF can be expressed as:

[0073]

[0074] The cascade MPF is integrated into the OEO, and the MPF is used to select the oscillation mode of the OEO. When the closed-loop gain of the OEO is greater than the loop loss, after stable oscillation is formed through countless cycles, the microwave signal voltage recovered from the photodetector can be described as:

[0075]

[0076]

[0077] where τ 3 is the transmission delay of the oscillation loop of the OEO; G A represents the closed-loop gain coefficient, which is mainly determined by the gain of the electrical amplifier and the oscillation loop loss.

[0078] Further, the output power of the OEO can be obtained as

[0079]

[0080] where R represents the load impedance of the photodetector. According to formula (6), formula (8), formula (9) and formula (11), the starting condition of the OEO can be obtained as:

[0081]

[0082] where A is an integer, ω osc is the oscillation angular frequency. As can be seen from formula (12), by simply adjusting Δτ, the tuning function of the oscillation angular frequency ω osc can be realized.

[0083] In order to further illustrate the beneficial effects of the optical-electrical oscillator, experiments are performed on the preferred example optical-electrical oscillator, and the experimental result graphs of figures 2-6 are obtained. Figures 2(a) and 2(b) are frequency response graphs of the cascade MPF, the horizontal coordinates of which both represent frequency (Frequency) in GHz; the vertical coordinates of which both represent frequency response function in dB; in figure 2(a), the sweep range (SPAN) of the optical-electrical oscillator is 20 GHz; in figure 2(b), the sweep range (SPAN) of the optical-electrical oscillator is 560 MHz.

[0084] Fig. 3(a) and Fig. 3(b) are the microwave signal spectrum diagram of the photoelectric oscillator of the present application with the oscillation frequency of 7.48 GHz, Fig. 3(a) has the horizontal coordinate of frequency (Frequency) with the unit of GHz and the vertical coordinate of power with the unit of dBm; Fig. 3(b) has the horizontal coordinate of offset frequency (Offset Frequency) with the unit of Hz and the vertical coordinate of power with the unit of dBm; in Fig. 3(a), the sweep range (SPAN) of the photoelectric oscillator of the present application is 14 GHz; in Fig. 3(b), the sweep range (SPAN) of the photoelectric oscillator of the present application is 200 kHz. It can be seen from the figures that the photoelectric oscillator can output microwave signal with high spectral purity under the action of the IIR filter.

[0085] Fig. 4(a) and Fig. 4(b) are the comparison diagram of the oscillation signal stability of the photoelectric oscillator with or without the double parallel recirculating delay lines (DP-RDLs). In Fig. 4(a) and Fig. 4(b), the horizontal coordinate is time (Time) with the unit of minute (min) and the vertical coordinate is frequency drift (Frequency drift); Fig. 4(a) represents the photoelectric oscillator with the DP-RDLs and Fig. 4(b) represents the photoelectric oscillator without the DP-RDLs; it can be seen from the comparison of Fig. 4(a) and Fig. 4(b) that the stability of the photoelectric oscillator is greatly improved after the introduction of the DP-RDLs, and the maximum frequency drift of the oscillation signal is only 1.817 kHz through one hour of continuous measurement, and there is no mode jump. It can be further known that the photoelectric oscillator can generate microwave signal with high stability under the action of the IIR filter based on the DP-RDLs.

[0086] Figure 5 Fig. 5 is the microwave signal phase noise diagram of the photoelectric oscillator of the present application with the oscillation frequency of 7.48 GHz. In the figure, the horizontal coordinate is offset frequency (Offset frequency) with the unit of Hz and the vertical coordinate is phase noise (Phase noise) with the unit of dBc / Hz; it can be seen from the figure that the phase noise of the output microwave signal can be-100.7 dBc / Hz@10 kHz when the oscillation frequency is 7.48 GHz.

[0087] Figure 6(a) is a superimposed schematic diagram of the microwave signal spectrum output by the photoelectric oscillator of the present application by adjusting the OVDL. As can be seen, by simply adjusting the delay of the OVDL, the output microwave signal has a wideband tuning range of 6.1-11.98 GHz. In the diagram, the horizontal axis is frequency (Frequency) in GHz, and the vertical axis is power in dBm. Figure 6(b) is a schematic diagram of the phase noise of different output microwave signals of the photoelectric oscillator of the present application at a frequency offset of 10 kHz. In the diagram, the horizontal axis is frequency (Frequency) in GHz, and the vertical axis is phase noise (Phase noise) in dBc / Hz. As can be seen from the diagram, the phase noise only has a slight change, which can be approximated as a frequency-independent function, which is consistent with the characteristics of the OEO.

[0088] In summary, the tuning method of the present application is simple, has a large tuning range (i.e. the tunability of the oscillation frequency can be achieved by simply adjusting the delay of the OVDL, and the tuning range is 6.1-11.98 GHz), and is easy to implement in engineering. In addition, by introducing the IIR filter based on the DP-RDLs, not only is the mode selection ability of the MPF improved (the 3-dB bandwidth of the MPF is greatly reduced), but also the stability of the photoelectric oscillator is greatly improved (through one hour of observation, the frequency drift is less than one fifth of that without using the DP-RDLs).

[0089] The present application also includes a signal generation method of a wideband tunable photoelectric oscillator with high stability, which has the same inventive concept as the wideband tunable photoelectric oscillator with high stability described above, and includes the following steps:

[0090] S1: generating an optical signal by a wideband light source;

[0091] S2: splitting the optical signal into two by an optical coupler (OC1), transmitting the upper branch optical signal to the upper input optical port of the double-input MZM after delay processing by the optical variable delay line, and directly transmitting the lower branch optical signal to the lower input optical port of the double-input Mach-Zehnder modulator to modulate the oscillation signal;

[0092] S3: amplifying the modulated signal by an erbium-doped fiber amplifier, and entering the linearly chirped Bragg fiber of the dispersion device through an optical circulator;

[0093] S4: transmitting the optical signal output from the linearly chirped Bragg fiber to the double-parallel circulative delay line infinite impulse response filter;

[0094] S5: transmitting the optical signal to the photodetector through the single-mode optical fiber to convert the optical signal to an electrical signal;

[0095] S6: The electric signal is amplified and transmitted to the double-input MZM to form oscillation, and finally a high-stability, wide-band and tunable microwave signal is output.

[0096] The above detailed description is a detailed description of the present application, and cannot be considered as limiting the specific embodiments of the present application to these descriptions. For those skilled in the art, without departing from the concept of the present application, a number of simple deductions and substitutions can be made, which should be considered as falling within the scope of protection of the present application.

Claims

1. A highly stable broadband tunable optoelectronic oscillator, characterized in that: It includes a broadband light source, an optical coupler, a dual-input Mach-Zehnder modulator, an optical fiber amplifier, and an optical circulator connected in sequence. The other two ends of the optical circulator are respectively connected to a Bragg grating and an infinite impulse response filter based on dual parallel cyclic delay lines. The infinite impulse response filter is connected to the dual-input Mach-Zehnder modulator in sequence via a single-mode optical fiber, a photodetector, and an electrical amplifier. An optical variable delay line is provided in one of the optical paths connecting the optical coupler and the dual-input Mach-Zehnder modulator. The broadband light source, the dual-input Mach-Zehnder modulator, the optical variable delay line and the Bragg grating constitute a microwave photonic filter based on the dispersion effect. The broadband light source is a rectangular broadband light source; The upper output end of the optical coupler is connected to the upper input optical port of the dual-input Mach-Zehnder modulator via an optical variable delay line to form an upper connecting arm, and the lower output end of the optical coupler is connected to the lower input optical port of the dual-input Mach-Zehnder modulator to form a lower connecting arm. The optical variable delay line provides a variable delay difference for the upper and lower connecting arms. By adjusting the delay of the optical variable delay line, the photoelectric oscillator can achieve a wideband tuning range of 6.1 GHz to 11.98 GHz.

2. The highly stable broadband tunable opto-oscillator according to claim 1, characterized in that: The rectangular broadband light source includes an amplified spontaneous emission source and an optical bandpass filter connected in sequence.

3. The highly stable broadband tunable opto-oscillator according to claim 1, characterized in that: The Bragg grating is a linear chirped Bragg grating.

4. The highly stable broadband tunable opto-oscillator according to claim 1, characterized in that: The fiber amplifier is an erbium-doped fiber amplifier.

5. The highly stable broadband tunable opto-oscillator according to claim 1, characterized in that: The amplifier is a radio frequency amplifier.

6. The highly stable broadband tunable opto-oscillator according to claim 1, characterized in that: The microwave photonic filter is a finite impulse response filter.

7. A signal generation method using a highly stable broadband tunable optoelectronic oscillator, comprising generating a microwave signal based on the broadband tunable optoelectronic oscillator according to any one of claims 1-6, characterized in that: Includes the following steps: Broadband light sources generate optical signals; The optical signal is split into two by an optical coupler. The upper branch optical signal is delayed by an optical variable delay line and then transmitted to the upper input optical port of the dual-input Mach-Zehnder modulator. The lower branch optical signal is directly transmitted to the lower input optical port of the dual-input Mach-Zehnder modulator and then modulated. The modulated signal is amplified by an optical fiber amplifier and then enters the Bragg fiber via an optical circulator. The optical signal output from the Lag fiber is transmitted to an infinite impulse response filter based on dual parallel cyclic delay lines, and then the optical signal is transmitted to a photodetector via a single-mode fiber to convert the optical signal into an electrical signal. The electrical signal is amplified and transmitted to a dual-input Mach-Zehnder modulator to generate oscillations, and finally outputs a highly stable, broadband tunable microwave signal.

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