All-optical microwave memory

Abstract

The invention discloses an all-optical microwave memory, which comprises a frequency shift ring used for enabling a modulated optical signal to carry out N times of optical path circulation in the frequency shift ring so as to store the modulated optical signal, and the storage time length of the modulated optical signal is equal to N * the time length of one circle of the modulated optical signal in the frequency shift ring; the frequency shift ring comprises an optical coupler, a frequency shifter, a Raman optical fiber amplifier and a delay optical fiber; wherein a modulated optical signal received by the optical coupler during the first optical path circulation is formed by loading a microwave signal onto an optical signal; the modulated optical signal received by the optical coupler during the ith optical path circulation is the modulated optical signal output by the frequency shift ring after the (i-1) th optical path circulation, and i is greater than or equal to 2 and less than or equal to N. According to the all-optical microwave memory provided by the embodiment of the invention, the Raman optical fiber amplifier is used as an optical amplifier in the frequency shift ring to carry out distributed amplification on the signal, so that multiple and long-time high-fidelity storage of the linear frequency modulation microwave signal with ultra-long duration is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave signal processing, and in particular relates to an all-optical microwave memory. Background Art

[0002] Achieving high fidelity microwave memory is a long-standing challenge. Many applications, such as radar, require reconfigurable high fidelity storage of received radar pulses. Microwave memory is an important component of electronic countermeasure applications. In such applications, RF memory is used to store and retransmit copies of one or more threat radar RF pulses. By memorizing the radar's incident microwave pulses and retransmitting them at carefully controlled times, a jamming signal is generated that can deceive the threat radar.

[0003] However, it is particularly difficult to store the required high-fidelity complex waveform microwave radar pulses using electronic methods due to the limited resolution of analog-to-digital conversion at microwave frequencies. Electronic digital RF memory is currently the only effective solution for coherent RF signal storage. However, this approach has an important limitation, which is that it cannot achieve wide instantaneous bandwidth and high dynamic range performance at the same time. The high time-bandwidth product unique to all-optical signal processing provides a possibility to overcome the inherent bottleneck caused by the limited sampling speed of traditional electronic signal processors. All-optical microwave memory based on optical frequency shifting ring overcomes the limitations of storage time and instantaneous bandwidth in the hybrid electronic cyclic memory loop by eliminating the use of electronic components in the structure, and can store complex waveform microwave radar pulses with high fidelity.

[0004] However, the existing all-optical microwave memory based on the optical frequency-shift ring structure is affected by the transient effect of the optical amplifier in the optical frequency-shift ring. The long gain recovery time will cause the leading and trailing edges of the optical pulses in the optical frequency-shift ring to be amplified to different degrees, which seriously limits the maximum number of times the microwave pulse signal can be stored in the all-optical memory. Summary of the invention

[0005] In order to solve the above problems in the prior art, an all-optical microwave memory capable of achieving both large instantaneous bandwidth and high dynamic range performance is provided according to an embodiment of the present invention.

[0006] According to one aspect of an embodiment of the present invention, an all-optical microwave memory includes: a frequency shifting ring, used to make a modulated optical signal perform N optical path cycles in the frequency shifting ring to store the modulated optical signal, and the storage time length of the modulated optical signal = N × the time length of the modulated optical signal making one circle in the frequency shifting ring; the frequency shifting ring includes: an optical coupler, used to receive the modulated optical signal and divide the received modulated optical signal into a high-power storage optical signal and a low-power reading optical signal; a frequency shifter, used to perform frequency shift on the storage optical signal divided by the optical coupler in each optical path cycle; a Raman fiber amplifier, Used to perform power compensation on the stored optical signal after the frequency shifter is frequency-shifted in each optical path cycle; a delay optical fiber is arranged between the frequency shifter and the Raman optical fiber amplifier, used to make the delay of the frequency shift loop greater than the duration of the modulated optical signal, and is used as a gain medium of the Raman optical fiber amplifier; wherein the modulated optical signal received by the optical coupler during the first optical path cycle is formed by loading a microwave signal onto an optical carrier; wherein the modulated optical signal received by the optical coupler during the i-th optical path cycle is the stored optical signal after power compensation in the i-1-th optical path cycle, 2≤i≤N.

[0007] In an example of the all-optical microwave storage provided in the above aspect, the frequency shifting ring further includes: a wavelength division multiplexer, which is arranged between the frequency shifter and the delay optical fiber, and the wavelength division multiplexer includes a first channel and a second channel, the first channel is used to pass the stored optical signal after the frequency shifting by the frequency shifter, and the second channel is used to export the remaining pump light of the Raman fiber amplifier out of the optical loop of the frequency shifting ring.

[0008] In an example of the all-optical microwave storage provided in the above aspect, the frequency shift ring also includes: a dispersion compensating optical fiber, which is arranged between the delay optical fiber and the Raman fiber amplifier, and is used to eliminate signal distortion caused by optical fiber dispersion in the optical loop of the frequency shift ring, and is used as a gain medium of the Raman fiber amplifier.

[0009] In an example of the all-optical microwave memory provided in the above aspect, the frequency shift ring further includes: an adjustable optical filter, arranged between the Raman fiber amplifier and the optical coupler, for filtering out spontaneous radiation noise outside the gain bandwidth required by the Raman fiber amplifier.

[0010] In an example of the all-optical microwave memory provided in the above aspect, the frequency shifter is a first acousto-optic modulator or a dual parallel Mach-Zehnder modulator.

[0011] In an example of the all-optical microwave memory provided in the above aspect, the all-optical microwave memory further includes: a light source, a polarization controller, an intensity modulator, a DC source, a DC bias device and an arbitrary waveform generator; the DC source is used to generate a DC signal, the DC bias device is used to generate a DC bias signal using the DC signal, and output the DC bias signal to the intensity modulator, and the intensity modulator is used to work in a linear working area under the action of the DC bias signal; the light source is used to generate a continuous optical signal, the polarization controller is used to make the polarization state of the continuous optical signal the same as the direction of the polarizer in the intensity modulator, and output the optical signal to the intensity modulator so that the power of the optical signal output by the intensity modulator reaches the maximum; the arbitrary waveform generator is used to generate a microwave signal, the DC bias device is also used to make the microwave signal pass through and output it to the intensity modulator, and the intensity modulator is also used to use the microwave signal to perform intensity modulation on the optical signal so as to load the microwave signal onto the optical signal.

[0012] In an example of the all-optical microwave memory provided in the above aspect, the all-optical microwave memory further includes: a second acousto-optic modulator and a photodetector; the driving frequency of the second acousto-optic modulator is consistent with the frequency of the modulated optical signal input to the optical coupler, the second acousto-optic modulator is used to receive the read optical signal output by the optical coupler, and the photodetector is used to detect the read optical signal from the second acousto-optic modulator.

[0013] In an example of the all-optical microwave memory provided in the above aspect, the optical coupler is a 2×2 optical coupler, a first input end of the optical coupler is connected to the Raman fiber amplifier, a second input end of the optical coupler is connected to the intensity modulator, a first output end of the optical coupler is connected to the frequency shifter, and a second output end of the optical coupler is connected to the second acousto-optic modulator.

[0014] In an example of the all-optical microwave memory provided in the above aspect, the power ratio of the optical coupler is 9:1.

[0015] In an example of the all-optical microwave memory provided in the above aspect, the all-optical microwave memory further includes: a third acousto-optic modulator, which is used to achieve frequency shift of the modulated optical signal, thereby suppressing lasing of the loop.

[0016] Beneficial effects: The all-optical microwave storage according to the embodiment of the present invention uses a Raman fiber amplifier as an optical amplifier in a frequency shift loop to perform distributed amplification of signals, thereby achieving multiple and long-term high-fidelity storage of ultra-long-duration linear frequency-modulated microwave signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other aspects, features and advantages of the embodiments of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which: Figure 1 4 is a schematic diagram of the principle of an all-optical microwave memory according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention may be implemented in many different forms, and the present invention should not be construed as being limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the present invention and their practical applications, so that other persons skilled in the art can understand the various embodiments of the present invention and various modifications suitable for specific intended applications.

[0019] As used herein, the term "including" and its variations represent open terms, meaning "including but not limited to". The terms "based on", "according to", etc. mean "based at least in part on", "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

[0020] Figure 1 4 is a schematic diagram of the principle of an all-optical microwave memory according to an embodiment of the present invention.

[0021] Reference Figure 1 According to an embodiment of the present invention, the all-optical microwave storage includes a frequency shift ring (unnumbered), which is used to modulate the optical signal (or optical carrier) to perform N optical path cycles in the frequency shift ring to store the modulated optical signal, and the storage time of the modulated optical signal = N × the time it takes for the modulated optical signal to make one circle in the frequency shift ring.

[0022] Specifically, the frequency shift ring includes: an optical coupler 4 , a frequency shifter 5 , a delay optical fiber 7 and a Raman optical fiber amplifier 9 .

[0023] The optical coupler 4 is used to receive the modulated optical signal and divide the received modulated optical signal into a high-power storage optical signal and a low-power reading optical signal.

[0024] The frequency shifter 5 is used to perform frequency shift on the high-power storage optical signal divided by the optical coupler 4 at each optical path cycle (i.e., add an offset frequency to the high-power storage optical signal). In this case, it is possible to prevent the frequency shift loop from forming loop lasing to introduce a large amount of intensity noise. In this embodiment, the frequency shifter 5 is a first acousto-optic modulator. However, the present invention is not limited thereto, and the frequency shifter 5 may also be a dual parallel Mach-Zehnder modulator or other suitable frequency shifters.

[0025] The Raman fiber amplifier 9 is used to compensate the power of the stored optical signal after the frequency shifter 5 is shifted each time the optical path is cycled. Therefore, the Raman fiber amplifier 9 provides gain to supplement the loss of optical power in the loop. The Raman fiber amplifier 9 uses the nonlinear effect of the transmission optical fiber itself to directly amplify the optical signal by stimulated Raman scattering, without the need to add a special gain medium into the optical fiber. The gain medium is the transmission optical fiber itself, which makes the Raman fiber amplifier 9 a distributed optical amplifier that generates gain along with the pump light. The signal light power along the optical fiber will not be too high, and the signal-to-noise ratio of the modulated optical signal can be well controlled along the line, avoiding signal distortion caused by transient effects. In addition, the noise coefficient of the Raman fiber amplifier 9 for long-distance transmission is extremely low, which can significantly improve the signal-to-noise ratio of the microwave signal after long-term storage in the loop.

[0026] The delay optical fiber 7 may be a single-mode optical fiber, which is disposed between the frequency shifter 5 and the Raman optical fiber amplifier 9, and is used to make the delay of the frequency shift loop greater than the pulse duration of the modulated optical signal (or the stored optical signal). Furthermore, the delay of the frequency shift loop is greater than the pulse duration of the modulated optical signal (the skilled person can set the delay amount according to the description herein according to actual requirements (such as the pulse duration of the modulated optical signal)), thereby ensuring that the modulated optical signal does not cause crosstalk during the storage process.

[0027] Furthermore, the modulated optical signal received by the optical coupler 4 during the first optical path cycle is formed by loading the microwave signal onto the optical signal; wherein, the optical signal received by the optical coupler 4 during the i-th optical path cycle is the stored optical signal after power compensation by the Raman fiber amplifier 9 in the i-1-th optical path cycle, 2≤i≤N.

[0028] In order to guide the remaining pump light of the Raman fiber amplifier 9 in the optical loop out of the frequency shift loop, the frequency shift loop also includes: a wavelength division multiplexer 6, which is arranged between the frequency shifter 5 and the delay fiber 7. The wavelength division multiplexer 6 includes a first channel and a second channel, the first channel is used to pass the stored optical signal after the frequency shift by the frequency shifter 5, and the second channel is used to guide the remaining pump light of the Raman fiber amplifier 9 out of the optical loop of the frequency shift ring. Of course, in another embodiment, the wavelength division multiplexer 6 may not exist.

[0029] In addition, the frequency shift loop also includes: a dispersion compensating optical fiber 8, which is arranged between the delay optical fiber 7 and the Raman optical fiber amplifier 9, and is used to eliminate the signal distortion caused by the optical fiber dispersion in the optical loop of the frequency shift loop, and at the same time acts as the gain medium of the Raman optical fiber amplifier 9. Therefore, the problem of signal strength attenuation caused by the optical fiber dispersion in the loop is overcome by using the dispersion compensating optical fiber 8. Of course, in another embodiment, the dispersion compensating optical fiber 8 does not exist. The long storage time of the all-optical microwave memory according to the embodiment of the present invention corresponds to many cycles of the modulated optical signal in the optical loop. This is equivalent to a very long optical fiber for optical signal transmission, which will cause a large amount of accumulation of optical fiber dispersion, thereby causing serious microwave signal power attenuation problems. In order to store microwave signals with high fidelity, it is necessary to minimize the distortion of microwave signals in the optical frequency shift loop, so it is necessary to use dispersion compensating optical fiber 8 to eliminate the distortion problem of microwave signals.

[0030] In addition, the frequency shift ring further includes: an adjustable optical filter 10, which is arranged between the Raman fiber amplifier 9 and the optical coupler 4, and is used to filter out the spontaneous emission noise outside the gain bandwidth required by the Raman fiber amplifier 9. Of course, in another embodiment, the adjustable optical filter 10 may not exist.

[0031] In order to generate a modulated optical signal, the all-optical microwave memory according to the embodiment of the present invention further includes: a light source 1, a polarization controller 2, an intensity modulator 3, a DC source 13, a DC bias device 14, and an arbitrary waveform generator 15. Of course, the modulated optical signal generator (not numbered) composed of the light source 1, the polarization controller 2, the intensity modulator 3, the DC source 13, the DC bias device 14, and the arbitrary waveform generator 15 is only an example, and the modulated optical signal generator of the present invention is not limited thereto.

[0032] Specifically, the DC source 13 is used to generate a DC signal, the DC bias device 14 is used to generate a DC bias signal using the DC signal, and output the DC bias signal to the intensity modulator 3, and the intensity modulator 3 is used to operate in a linear working area under the action of the DC bias signal.

[0033] The light source 1 is used to generate a continuous light signal, and the polarization controller 2 is used to make the polarization state of the continuous light signal the same as the direction of the polarizer in the intensity modulator 3, and output the light signal (the light signal at this time is the light signal output by the light source 1 after the polarization state is adjusted by the polarization controller 2) to the intensity modulator 3. The intensity modulator 3 is also used to maximize the power of the light signal it outputs.

[0034] The arbitrary waveform generator 15 is used to generate a (linear frequency modulated) microwave signal (such as a radar signal), and the DC bias device 14 is also used to allow the microwave signal to pass through and output to the intensity modulator 3. The intensity modulator 3 is also used to use the microwave signal to modulate the intensity of the optical signal so as to load the microwave signal onto the optical signal (that is, after the optical signal output by the polarization controller 2 to the intensity modulator 3 is intensity modulated, the microwave signal is loaded onto the optical signal).

[0035] In addition, the all-optical microwave memory further includes: a second acousto-optic modulator 11 and a photodetector 12. Here, the second acousto-optic modulator 11 and the photodetector 12 are only provided to detect whether the optical loop stores the optical signal to be stored, so in another embodiment, the second acousto-optic modulator 11 may not exist.

[0036] Specifically, the driving frequency of the second AOM 11 is consistent with the frequency of the modulated optical signal input to the optical coupler 4, and the second AOM 11 is used to receive the low-power read optical signal output by the optical coupler 4. The photodetector 12 is used to detect the read optical signal from the second AOM 11.

[0037] In addition, in the present embodiment, the optical coupler 4 is a 2×2 photoelectric coupler, a first input end of the optical coupler 4 is connected to the Raman fiber amplifier 9, a second input end of the optical coupler 4 is connected to the intensity modulator 3, a first output end of the optical coupler 4 is connected to the frequency shifter 5, and a second output end of the optical coupler 4 is connected to the second acousto-optic modulator 11. Of course, the 2×2 optical coupler here is only an example of the optical coupler 4, and the structure of the optical coupler of the present invention is not limited thereto.

[0038] Furthermore, in this embodiment, the power ratio of the optical coupler 4 is 9: 1. However, the present invention is not limited thereto, and the power ratio of the optical coupler 4 may also be other ratios as long as the power intensity of the optical signal in the optical loop is satisfied.

[0039] The working process of the all-optical microwave memory according to the embodiment of the present invention is described in detail below. Specifically: The DC bias signal generated by the DC source 13 is injected into the intensity modulator 3 through the DC bias device 14, and the working point of the intensity modulator 3 is set in the linear working area; the continuous light generated by the light source 1 passes through the intensity modulator 3, wherein 2 is a polarization controller, and the polarization controller 2 is adjusted so that the polarization state of the optical signal generated by it is the same as the direction of the polarizer built into the intensity modulator 3, so that the optical signal power output by the intensity modulator 3 is maximized.

[0040] The microwave signal generated by the arbitrary waveform generator 15 is injected into the intensity modulator 3 after passing through the DC bias device 14 to perform intensity modulation on the optical signal so as to load the microwave signal onto the optical signal.

[0041] The modulated optical signal (i.e., the modulated optical signal input to the optical coupler 4 in the first optical path cycle) enters the 2×2 optical coupler 4 with a power ratio of 9:1 and is divided into two paths. The high-power path is used to store the modulated optical signal and enter the optical frequency shift loop, and the low-power path is used to read the modulated optical signal and enter the second acousto-optic modulator 11.

[0042] The first acousto-optic modulator 5 performs carrier suppressed single sideband modulation on the stored modulated optical signal to achieve frequency shift. The modulated optical signal after frequency shift enters the wavelength division multiplexer 6. The wavelength division multiplexer 6 has two channels, the first channel of which passes the modulated optical signal after frequency shift by the first acousto-optic modulator 5, and the second channel of which guides the remaining pump light of the Raman fiber amplifier 9 out of the loop.

[0043] The Raman fiber amplifier 9 provides gain to compensate for the attenuation of optical power in the optical loop, and the tunable optical filter 10 filters out the spontaneous radiation noise outside the gain bandwidth required by the Raman fiber amplifier 9 .

[0044] Among them, the time delay of the optical frequency shift loop is greater than the time length of the required storage of the optical signal, ensuring that the optical signal to be stored can be completely stored in the optical frequency shift loop to ensure that there is no crosstalk with the signal stored next time. A part of the optical signal after frequency shifting is output through the optical coupler 4, and the rest is fed back to the optical frequency shift loop for the next frequency shift. The output light of the frequency shift loop passes through the second acousto-optic modulator 11 with a very high extinction ratio, and the driving frequency of the second acousto-optic modulator 11 is set to be consistent with the frequency of the modulated optical signal input to the optical coupler 4, so as to suppress the first signal output by the optical frequency shift loop with excessively high power. Finally, the microwave signal stored with high fidelity can be detected on the photodetector 12.

[0045] In this embodiment, the optical signal loaded with microwave signal is input into the frequency shift loop, but its signal-to-noise ratio is generally low, which may limit the number of times the modulated optical signal can be stored in the optical frequency shift loop. Therefore, in other embodiments of the present invention, a third acousto-optic modulator (not shown) with a high extinction ratio can be added before entering the frequency shift loop to improve the signal-to-noise ratio of the modulated optical signal, thereby increasing the number of times the modulated optical signal can be stored in the optical frequency shift loop. Therefore, in other embodiments of the present invention, the all-optical microwave memory further includes: a third acousto-optic modulator (not shown), which is used to allow the modulated optical signal to pass through it and then be output to the frequency shift loop.

[0046] In summary, the all-optical microwave storage according to the embodiment of the present invention uses a Raman fiber amplifier as an optical amplifier in a frequency shift loop to perform distributed amplification of signals, thereby achieving long-term high-fidelity storage of ultra-long duration microwave signals.

[0047] Distributed amplification: Raman fiber amplifiers use the stimulated Raman scattering effect of optical fiber media and have extremely fast gain recovery time. In addition, due to the very long length of optical fiber media, they are suitable for storing microwave pulses of ultra-long duration.

[0048] No signal distortion: Raman fiber amplifiers use the nonlinear effect of the transmission fiber itself to directly amplify the optical signal under stimulated Raman scattering. There is no need to add special gain media into the optical fiber. The gain medium is the transmission fiber itself. This makes the Raman fiber amplifier a distributed optical amplifier that generates gain along with the pump light. The signal light power along the optical fiber will not be too high, and the signal-to-noise ratio of the modulated optical signal can be well controlled along the line, avoiding signal distortion caused by transient effects.

[0049] Good signal-to-noise ratio: The noise figure of Raman optical amplifier is extremely low, which can greatly reduce the noise index of the system. By using dispersion-compensating optical fiber, the power attenuation problem of microwave signals can be eliminated and the quality of output signals can be improved.

[0050] The terms "exemplary," "example," and the like used throughout this specification mean "used as an example, instance, or illustration" and do not mean "preferred" or "advantageous" over other embodiments. The detailed description includes specific details for the purpose of providing an understanding of the described techniques. However, these techniques can be implemented without these specific details. In some instances, in order to avoid obscuring the concepts of the described embodiments, well-known structures and devices are shown in block diagram form.

[0051] The optional implementation modes of the embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above implementation modes. Within the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

[0052] The above description of the contents of this specification is provided to enable any person of ordinary skill in the art to implement or use the contents of this specification. Various modifications to the contents of this specification will be apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other variations without departing from the scope of protection of the contents of this specification. Therefore, the contents of this specification are not limited to the examples and designs described herein, but are consistent with the widest range of principles and novel features disclosed herein.

Claims

1. An all-optical microwave memory, characterized in that: include: A frequency shifting ring, used to make the modulated optical signal perform N optical path cycles in the frequency shifting ring to store the modulated optical signal, where the storage time of the modulated optical signal = N × the time it takes for the modulated optical signal to make one circle in the frequency shifting ring; The frequency shift loop comprises: An optical coupler, used for receiving a modulated optical signal and dividing the received modulated optical signal into a high-power storage optical signal and a low-power reading optical signal; A frequency shifter, used for frequency shifting the stored optical signal divided by the optical coupler at each optical path cycle; A Raman fiber amplifier, used for performing power compensation on the stored optical signal after the frequency shifter has shifted the frequency each time the optical path is cycled; A delay optical fiber, arranged between the frequency shifter and the Raman optical fiber amplifier, used to make the time delay of the frequency shift loop greater than the duration of the modulated optical signal, and used as a gain medium of the Raman optical fiber amplifier; Wherein, the modulated optical signal received by the optical coupler during the first optical path cycle is formed by loading the microwave signal onto the optical signal; The modulated optical signal received by the optical coupler during the i-th optical path cycle is the stored optical signal after power compensation in the i-1-th optical path cycle, 2≤i≤N.

2. The all-optical microwave memory according to claim 1, characterized in that: The frequency shift ring also includes: a wavelength division multiplexer, which is arranged between the frequency shifter and the delay optical fiber, and the wavelength division multiplexer includes a first channel and a second channel, the first channel is used to pass the stored optical signal after the frequency shifter is frequency shifted, and the second channel is used to export the remaining pump light of the Raman fiber amplifier out of the optical loop of the frequency shift ring.

3. The all-optical microwave memory according to claim 1, characterized in that: The frequency shift ring also includes: a dispersion compensation optical fiber, which is arranged between the delay optical fiber and the Raman optical fiber amplifier and is used to eliminate signal distortion caused by optical fiber dispersion in the optical loop of the frequency shift ring and is used as a gain medium of the Raman optical fiber amplifier.

4. The all-optical microwave memory according to claim 1, characterized in that: The frequency shift ring further includes: an adjustable optical filter, which is arranged between the Raman fiber amplifier and the optical coupler and is used to filter out the spontaneous radiation noise outside the gain bandwidth required by the Raman fiber amplifier.

5. The all-optical microwave memory according to any one of claims 1 to 4, characterized in that: The frequency shifter is a first acousto-optic modulator or a dual parallel Mach-Zehnder modulator.

6. The all-optical microwave memory according to any one of claims 1 to 4, characterized in that: The all-optical microwave memory further comprises: a light source, a polarization controller, an intensity modulator, a DC source, a DC bias device and an arbitrary waveform generator; The DC source is used to generate a DC signal, the DC bias device is used to generate a DC bias signal using the DC signal, and output the DC bias signal to the intensity modulator, and the intensity modulator is used to work in a linear working area under the action of the DC bias signal; The light source is used to generate a continuous light signal, and the polarization controller is used to make the polarization state of the continuous light signal the same as the direction of the polarizer in the intensity modulator, and output the light signal to the intensity modulator so that the power of the light signal output by the intensity modulator reaches the maximum; The arbitrary waveform generator is used to generate a microwave signal, the DC bias device is also used to allow the microwave signal to pass through and output to the intensity modulator, and the intensity modulator is also used to use the microwave signal to modulate the intensity of the optical signal so as to load the microwave signal onto the optical signal.

7. The all-optical microwave memory according to claim 6, characterized in that: The all-optical microwave memory further comprises: a second acousto-optic modulator and a photodetector; The driving frequency of the second acousto-optic modulator is consistent with the frequency of the modulated light signal input to the optical coupler, the second acousto-optic modulator is used to receive the read light signal output by the optical coupler, and the photodetector is used to detect the read light signal from the second acousto-optic modulator.

8. The all-optical microwave memory according to claim 7, characterized in that: The optical coupler is a 2×2 optical coupler, a first input end of the optical coupler is connected to the Raman fiber amplifier, a second input end of the optical coupler is connected to the intensity modulator, a first output end of the optical coupler is connected to the frequency shifter, and a second output end of the optical coupler is connected to the second acousto-optic modulator.

9. The all-optical microwave memory according to claim 8, characterized in that: The power ratio of the optical coupler is 9:

1.

10. The all-optical microwave memory according to claim 1, characterized in that: The all-optical microwave memory further comprises: a third acousto-optic modulator, which is used to achieve frequency shift of the modulated optical signal, thereby suppressing lasing of the loop.

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