Dual-frequency optoelectronic oscillator with active phase noise suppression

Abstract

The application discloses a dual-frequency optoelectronic oscillator capable of actively suppressing phase noise. The optoelectronic oscillator comprises two oscillation loops, one of which has an oscillation frequency of f1, and the other of which has an oscillation frequency of f2, and f2=Nf1, wherein N is a positive integer greater than 1. The f1 signal is multiplied by N, and then the multiplied signal is phase-detected with the f2 signal, and the generated phase error signal is used to control the phase of the f1 oscillation loop. Since the optoelectronic oscillator has the advantage that the phase noise does not deteriorate significantly with the increase of the oscillation frequency, the proposed dual-frequency optoelectronic oscillator can significantly suppress the phase noise of the f1 frequency component in the phase-locked control condition, and the ideal phase noise suppression effect can reach 20logN. The application utilizes the advantage that the phase noise of the optoelectronic oscillator does not deteriorate significantly with the increase of the oscillation frequency, and proposes a dual-frequency optoelectronic oscillator capable of actively suppressing phase noise, so that the phase noise of the microwave signal generated by the optoelectronic oscillator can be further reduced.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronics and microwave technology, and in particular, it is a dual-frequency optoelectronic oscillator that actively suppresses phase noise. Background Technology

[0002] An optoelectronic oscillator is a time-delay ring oscillator composed of a hybrid optical and electrical link, capable of directly generating microwave signals. High-performance optoelectronic oscillators typically use optical fiber as the energy storage medium to provide a large loop delay. Due to the advantages of low loss and large bandwidth of optical fiber, the phase noise of the optoelectronic oscillator does not significantly deteriorate with increasing oscillation frequency. Ideally, the phase noise of the optoelectronic oscillator is independent of the oscillation frequency.

[0003] Optoelectronic oscillators can generate microwave signals with extremely low phase noise using several kilometers of optical fiber. Their phase noise is far lower than that of traditional microwave frequency sources (such as crystal phase-locked loop sources, crystal frequency multipliers, and voltage-controlled oscillators). Therefore, optoelectronic oscillators have broad application prospects and can be used as microwave local oscillators in radar and communication systems to improve system performance. With the development of military technology and the increase in communication capacity and speed, higher demands are being placed on the phase noise of microwave local oscillators, necessitating further reductions in the phase noise of optoelectronic oscillators.

[0004] Phase noise of an oscillator can be suppressed by phase-locked loop (PLL) to a reference source. However, the phase noise of an optoelectronic oscillator is much lower than that of a traditional microwave frequency source, making it difficult to reduce the phase noise using a reference source. Furthermore, the phase noise of an optoelectronic oscillator is closely related to loop delay, and its phase noise can be reduced by increasing the fiber length. However, increasing the fiber length makes the system more susceptible to environmental disturbances, thus deteriorating the system's long-term stability. Therefore, methods to reduce the phase noise of optoelectronic oscillators need to be investigated. Summary of the Invention

[0005] The technical problem to be solved by this invention is the suppression of phase noise in optoelectronic oscillators. A dual-frequency optoelectronic oscillator with active phase noise suppression is proposed, which performs frequency doubling and phase locking based on two microwave signals of different frequencies generated by its own oscillation, thereby effectively reducing the phase noise of the optoelectronic oscillator.

[0006] The technical solution to achieve the purpose of this invention is as follows: On the one hand, this invention provides a dual-frequency optoelectronic oscillator for actively suppressing phase noise, including a light source, a Mach-Zehnder modulator, a transmission optical fiber, a photodetector, a first microwave amplifier, a first duplexer, a first electrical bandpass filter, a first electrical coupler, a voltage-controlled phase shifter, a second electrical bandpass filter, a second electrical coupler, a second duplexer, a second microwave amplifier, a frequency multiplier, a phase detection module, and a control module;

[0007] The light source, Mach-Zehnder modulator, transmission optical fiber, photodetector, first microwave amplifier, and first duplexer are cascaded in sequence. The two outputs of the first duplexer are connected to a first electrical bandpass filter and a voltage-controlled phase shifter, respectively. The first electrical bandpass filter and first electrical coupler are cascaded in sequence, with the direct output of the first electrical coupler connected to one input of the second duplexer. The voltage-controlled phase shifter, second electrical bandpass filter, and second electrical coupler are cascaded in sequence, with the direct output of the second electrical coupler connected to the other input of the second duplexer. The second duplexer and second microwave amplifier are cascaded in sequence, with the output of the second microwave amplifier connected to the microwave drive terminal of the Mach-Zehnder modulator. The coupled output of the first electrical coupler is connected to one input of the phase detection module. The coupled output of the second electrical coupler is connected to the input of the frequency multiplier, and the output of the frequency multiplier is connected to the other input of the phase detection module. The output of the phase detection module is connected to the input of the control module, and the output of the control module is connected to the control terminal of the voltage-controlled phase shifter.

[0008] Furthermore, the transmission optical fiber can be replaced by an optical waveguide, an optical resonant cavity, an optical slow-wave structure, or a combination thereof.

[0009] Furthermore, by using a first duplexer, a first electric bandpass filter, a first electric coupler, a voltage-controlled phase shifter, a second electric bandpass filter, a second electric coupler, and a second duplexer to form parallel microwave links with different transmission frequencies, an optoelectronic oscillator containing two oscillation loops is formed.

[0010] Furthermore, phase error detection is achieved based on the f1 and f2 signals generated by the dual-frequency opto-oscillator, and the Nth harmonic component of the f1 signal is phase-locked to the f2 signal, thereby reducing the phase noise of the f1 signal.

[0011] Furthermore, the frequency multiplier is composed of an amplifier operating in saturation or a nonlinear transmission line.

[0012] On the other hand, based on the same inventive concept, the present invention also provides a dual-frequency optoelectronic oscillator for actively suppressing phase noise, comprising a light source, a Mach-Zehnder modulator, a transmission optical fiber, a photodetector, a first microwave amplifier, a first duplexer, a first electrical bandpass filter, a first electrical coupler, an electrically controlled filter, a second electrical coupler, a second duplexer, a second microwave amplifier, a frequency multiplier, a phase detection module, and a control module.

[0013] The light source, Mach-Zehnder modulator, transmission optical fiber, photodetector, first microwave amplifier, and first duplexer are cascaded in sequence. The two outputs of the first duplexer are connected to a first electrical bandpass filter and an electrically controlled filter, respectively. The first electrical bandpass filter and a first electrical coupler are cascaded in sequence, with the direct output of the first electrical coupler connected to one input of a second duplexer. The electrically controlled filter and the second electrical coupler are cascaded in sequence, with the direct output of the second electrical coupler connected to the other input of the second duplexer. The second duplexer and the second microwave amplifier are cascaded in sequence, with the output of the second microwave amplifier connected to the microwave drive of the Mach-Zehnder modulator. The coupled output of the first electrical coupler is connected to one input of a phase detection module. The coupled output of the second electrical coupler is connected to the input of a frequency multiplier, and the output of the frequency multiplier is connected to the other input of the phase detection module. The output of the phase detection module is connected to the input of a control module, and the output of the control module is connected to the control terminal of the electrically controlled filter.

[0014] Furthermore, the transmission optical fiber is replaced by an optical waveguide, an optical resonant cavity, an optical slow-wave structure, and combinations thereof.

[0015] Furthermore, by using a first duplexer, a first electric bandpass filter, a first electric coupler, an electric control filter, a second electric coupler, and a second duplexer to form parallel microwave links with different transmission frequencies, an optoelectronic oscillator containing two oscillation loops is formed.

[0016] Furthermore, phase error detection is achieved based on the f1 and f2 signals generated by the dual-frequency opto-oscillator, and the Nth harmonic component of the f1 signal is phase-locked to the f2 signal, thereby reducing the phase noise of the f1 signal.

[0017] Furthermore, the frequency multiplier is composed of an amplifier operating in saturation or a nonlinear transmission line.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention can significantly reduce the phase noise of the optoelectronic oscillator, improve the frequency stability of the system, and further expand the application range of the optoelectronic oscillator; the phase noise suppression achieved by the present invention is based on the signal generated by the optoelectronic oscillator itself, without the need for an additional low-noise reference source outside the loop, and is applicable to a variety of optoelectronic oscillators with different structures. Attached Figure Description

[0019] Figure 1 This is a block diagram of a dual-frequency optoelectronic oscillator that actively suppresses phase noise, constructed using a voltage-controlled phase shifter.

[0020] Figure 2 This is a block diagram of a dual-frequency optoelectronic oscillator that actively suppresses phase noise, constructed using an electronically controlled filter. Detailed Implementation

[0021] This invention proposes a dual-frequency optoelectronic oscillator for actively suppressing phase noise, comprising a light source 1, a Mach-Zehnder modulator 2, a transmission optical fiber 3, a photodetector 4, a first microwave amplifier 5, a first duplexer 6, a first electrical bandpass filter 7, a first electrical coupler 8, a voltage-controlled phase shifter 9, a second electrical bandpass filter 10, a second electrical coupler 11, a second duplexer 12, a second microwave amplifier 13, a frequency multiplier 14, a phase detection module 15, and a control module 16;

[0022] The optical carrier generated by the light source 1 is modulated in the Mach-Zehnder modulator 2 and then injected into the photodetector 4 via the transmission fiber 3 to recover the modulated microwave signal. This microwave signal passes through the first microwave amplifier 5 and is then input to the first duplexer 6, where it is split into two signals. One signal passes through the first electrical bandpass filter 7 and the first electrical coupler 8 before being input to one port of the second duplexer 12; the other signal passes through the voltage-controlled phase shifter 9, the second electrical bandpass filter 10, and the second electrical coupler 11 before being input to the other port of the second duplexer 12. Thus, a combined signal of the two signals is obtained at the output of the second duplexer 12. This combined signal passes through the second microwave amplifier 13 and drives the Mach-Zehnder modulator 2 to modulate the optical carrier, thereby constructing a closed oscillation loop.

[0023] The first duplexer 6 has two output terminals that can output different frequency components of the microwave signal. The center frequency of the first electric bandpass filter 7 is f1, and the center frequency of the second electric bandpass filter 10 is f2, where f2 = Nf1. Furthermore, the second duplexer 12 combines microwave signals of different frequencies. Therefore, the dual-frequency opto-oscillator with active phase noise suppression can oscillate and generate two microwave signals of different frequencies, f1 and f2, respectively.

[0024] Furthermore, the oscillation signal with frequency f1 is coupled outside the loop by the second electro-coupler 11, and after passing through the frequency multiplier 14, a microwave signal with frequency Nf1 is obtained; the oscillation signal with frequency f2 is coupled outside the loop by the first electro-coupler 8. The signals output from the frequency multiplier 14 and the signals coupled out from the first electro-coupler 8 are input to the phase detection module 15 to obtain a signal error signal. This phase error signal, after passing through the control module 16, controls the voltage-controlled phase shifter 9, thereby achieving phase-locking of the Nth harmonic component of the f1 signal to the f2 signal. At this time, the phase noise of the Nth harmonic component of the f1 signal is consistent with the phase noise of the f2 signal within the locked bandwidth. Therefore, the phase noise of the f1 signal is 20logN lower than the phase noise of the f2 signal within the locked bandwidth, that is, the dual-frequency opto-oscillator with active phase noise suppression can significantly suppress the phase noise of the f1 signal.

[0025] The phase of the oscillation loop that generates the f1 signal can be tuned by the voltage-controlled phase shifter 9 or by the electronically controlled filter 101.

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] Example 1

[0028] A dual-frequency optoelectronic oscillator for actively suppressing phase noise, constructed using a voltage-controlled phase shifter 9, is illustrated in the following block diagram: Figure 1 As shown. The light source 1, Mach-Zehnder modulator 2, transmission optical fiber 3, photodetector 4, first microwave amplifier 5, and first duplexer 6 are cascaded in sequence. The two outputs of the first duplexer 6 are connected to the first electrical bandpass filter 7 and the voltage-controlled phase shifter 9, respectively. The first electrical bandpass filter 7 and the first electrical coupler 8 are cascaded in sequence, with the direct output of the first electrical coupler 8 connected to one input of the second duplexer 12. The voltage-controlled phase shifter 9, the second electrical bandpass filter 10, and the second electrical coupler 11 are cascaded in sequence, with the direct output of the second electrical coupler 11 connected to the second duplexer 12. The other input terminal of 2; the second duplexer 12 and the second microwave amplifier 13 are cascaded in sequence, and the output terminal of the second microwave amplifier 13 is connected to the microwave drive terminal of the Mach-Zehnder modulator 2; the coupling output terminal of the first electrical coupler 8 is connected to one input terminal of the phase detection module 15; the coupling output terminal of the second electrical coupler 11 is connected to the input terminal of the frequency multiplier 14, and the output terminal of the frequency multiplier 14 is connected to the other input terminal of the phase detection module 15; the output terminal of the phase detection module 15 is connected to the input terminal of the control module 16, and the output terminal of the control module 16 is connected to the control terminal of the voltage-controlled phase shifter 9.

[0029] Example 2

[0030] A dual-frequency opto-oscillator with active phase noise suppression, constructed using an electronically controlled filter 101, is illustrated in the following block diagram: Figure 2As shown. The light source 1, Mach-Zehnder modulator 2, transmission optical fiber 3, photodetector 4, first microwave amplifier 5, and first duplexer 6 are cascaded in sequence. The two outputs of the first duplexer 6 are connected to the first electrical bandpass filter 7 and the electrically controlled filter 101, respectively. The first electrical bandpass filter 7 and the first electrical coupler 8 are cascaded in sequence, with the direct output of the first electrical coupler 8 connected to one input of the second duplexer 12. The electrically controlled filter 101 and the second electrical coupler 11 are cascaded in sequence, with the direct output of the second electrical coupler 11 connected to the other input of the second duplexer 12. The first input terminal; the second duplexer 12 and the second microwave amplifier 13 are cascaded in sequence, and the output terminal of the second microwave amplifier 13 is connected to the microwave drive terminal of the Mach-Zehnder modulator 2; the coupling output terminal of the first electrical coupler 8 is connected to one input terminal of the phase detection module 15; the coupling output terminal of the second electrical coupler 11 is connected to the input terminal of the frequency multiplier 14, and the output terminal of the frequency multiplier 14 is connected to the other input terminal of the phase detection module 15; the output terminal of the phase detection module 15 is connected to the input terminal of the control module 16, and the output terminal of the control module 16 is connected to the control terminal of the electronically controlled filter 101.

[0031] The above description is only a preferred embodiment of the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A dual-frequency optoelectronic oscillator for actively suppressing phase noise, characterized in that, It includes a light source (1), a Mach-Zehnder modulator (2), a transmission optical fiber (3), a photodetector (4), a first microwave amplifier (5), a first duplexer (6), a first electrical bandpass filter (7), a first electrical coupler (8), a voltage-controlled phase shifter (9), a second electrical bandpass filter (10), a second electrical coupler (11), a second duplexer (12), a second microwave amplifier (13), a frequency multiplier (14), a phase detector module (15), and a control module (16). The light source (1), Mach-Zehnder modulator (2), transmission optical fiber (3), photodetector (4), first microwave amplifier (5), and first duplexer (6) are cascaded in sequence. The two outputs of the first duplexer (6) are connected to the first electric bandpass filter (7) and the voltage-controlled phase shifter (9), respectively. The first electric bandpass filter (7) and the first electric coupler (8) are cascaded in sequence, and the direct output of the first electric coupler (8) is connected to one input of the second duplexer (12). The voltage-controlled phase shifter (9), the second electric bandpass filter (10), and the second electric coupler (11) are cascaded in sequence, and the direct output of the second electric coupler (11) is connected to the second duplexer (12). The other input terminal of the duplexer (12); the second duplexer (12) and the second microwave amplifier (13) are cascaded in sequence, and the output terminal of the second microwave amplifier (13) is connected to the microwave drive terminal of the Mach-Zehnder modulator (2); the coupling output terminal of the first electrical coupler (8) is connected to one input terminal of the phase detection module (15); the coupling output terminal of the second electrical coupler (11) is connected to the input terminal of the frequency multiplier (14), and the output terminal of the frequency multiplier (14) is connected to the other input terminal of the phase detection module (15); the output terminal of the phase detection module (15) is connected to the input terminal of the control module (16), and the output terminal of the control module (16) is connected to the control terminal of the voltage-controlled phase shifter (9).

2. The dual-frequency opto-oscillator for actively suppressing phase noise according to claim 1, characterized in that, The transmission fiber (3) is replaced by an optical waveguide, an optical resonant cavity, an optical slow wave structure, or a combination thereof.

3. The dual-frequency opto-oscillator for actively suppressing phase noise according to claim 1, characterized in that, By using the first duplexer (6), the first electric bandpass filter (7), the first electric coupler (8), the voltage-controlled phase shifter (9), the second electric bandpass filter (10), the second electric coupler (11), and the second duplexer (12) to form a parallel microwave link with different transmission frequencies, an optoelectronic oscillator containing two oscillation loops is formed.

4. A dual-frequency opto-oscillator for actively suppressing phase noise according to claim 1, characterized in that, Phase error detection is achieved using the f1 and f2 signals generated by a dual-frequency opto-oscillator. The Nth harmonic component of the f1 signal is phase-locked to the f2 signal, thereby reducing the phase noise of the f1 signal.

5. A dual-frequency opto-oscillator for actively suppressing phase noise according to claim 1, characterized in that, The frequency multiplier (14) is composed of an amplifier operating in saturation or a nonlinear transmission line.

6. A dual-frequency optoelectronic oscillator for actively suppressing phase noise, characterized in that, It includes a light source (1), a Mach-Zehnder modulator (2), a transmission optical fiber (3), a photodetector (4), a first microwave amplifier (5), a first duplexer (6), a first electrical bandpass filter (7), a first electrical coupler (8), an electrical control filter (101), a second electrical coupler (11), a second duplexer (12), a second microwave amplifier (13), a frequency multiplier (14), a phase detector module (15), and a control module (16). The light source (1), Mach-Zehnder modulator (2), transmission optical fiber (3), photodetector (4), first microwave amplifier (5), and first duplexer (6) are cascaded in sequence. The two outputs of the first duplexer (6) are connected to the first electric bandpass filter (7) and the electronically controlled filter (101), respectively. The first electric bandpass filter (7) and the first electric coupler (8) are cascaded in sequence. The direct output of the first electric coupler (8) is connected to one input of the second duplexer (12). The electronically controlled filter (101) and the second electric coupler (11) are cascaded in sequence. The direct output of the second electric coupler (11) is connected to the second duplexer (12). The other input terminal of the phase detector module (15); the second duplexer (12) and the second microwave amplifier (13) are cascaded in sequence, and the output terminal of the second microwave amplifier (13) is connected to the microwave drive terminal of the Mach-Zehnder modulator (2); the coupling output terminal of the first electrical coupler (8) is connected to one input terminal of the phase detector module (15); the coupling output terminal of the second electrical coupler (11) is connected to the input terminal of the frequency multiplier (14), and the output terminal of the frequency multiplier (14) is connected to the other input terminal of the phase detector module (15); the output terminal of the phase detector module (15) is connected to the input terminal of the control module (16), and the output terminal of the control module (16) is connected to the control terminal of the electronically controlled filter (101).

7. A dual-frequency optoelectronic oscillator for actively suppressing phase noise according to claim 6, characterized in that, The transmission fiber (3) is replaced by an optical waveguide, an optical resonant cavity, an optical slow wave structure, or a combination thereof.

8. A dual-frequency opto-oscillator for actively suppressing phase noise according to claim 6, characterized in that, By using the first duplexer (6), the first electric bandpass filter (7), the first electric coupler (8), the electric control filter (101), the second electric coupler (11), and the second duplexer (12) to form a parallel microwave link with different transmission frequencies, an optoelectronic oscillator containing two oscillation loops is formed.

9. A dual-frequency opto-oscillator for actively suppressing phase noise according to claim 6, characterized in that, Phase error detection is achieved using the f1 and f2 signals generated by a dual-frequency opto-oscillator. The Nth harmonic component of the f1 signal is phase-locked to the f2 signal, thereby reducing the phase noise of the f1 signal.

10. A dual-frequency opto-oscillator for actively suppressing phase noise according to claim 6, characterized in that, The frequency multiplier (14) is composed of an amplifier operating in saturation or a nonlinear transmission line.

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