A photogenerated microwave source system and method based on a double-ring structure

Abstract

The present invention discloses a photogenerated microwave source system and method based on a dual-ring structure. The system includes a dual-wavelength semiconductor laser for forming a photon filter and outputting a filtered laser beam; an optoelectronic oscillator including a signal adjustment unit for converting an optical signal into an electrical signal and amplifying and filtering the electrical signal, wherein the signal adjustment unit generates a microwave signal for the microwave source system; and a laser current control module for controlling the dual-wavelength semiconductor laser to change the output frequency of the microwave signal. The present invention utilizes a dual-ring structure with a dual-wavelength semiconductor laser in an optical fiber link, improving spurious suppression and phase noise levels. The dual-ring structure uses a long-period single-mode fiber plus a dispersion-compensating fiber mode, effectively reducing the effects of dispersion and improving the phase noise index of the microwave signal. The output microwave frequency is tuned by changing the output current of the laser current control module.

Description

Technical Field

[0001] The present invention relates to the field of photogenerated microwave technology, and more specifically to a photogenerated microwave source system and method based on a double-ring structure. Background Art

[0002] Microwave frequency sources with low phase noise and high stability are widely used in fields such as radar, communications, and metering, and are core components of modern electronic devices. There are generally three ways to obtain microwave sources: 1. Frequency doubling with a standard crystal oscillator; 2. Taking advantage of the low loss of the dielectric, designing a high-Q dielectric resonant cavity, constructing a positive feedback amplifier circuit, and controlling the phase and amplitude to improve the stability of the output signal; 3. Using optical microwave generation. There are two main types: 1. Locking an ultra-stable laser to a highly stable optical resonant cavity and converting it to the desired frequency using an optical comb; 2. The optoelectronic oscillator method: Using optical fibers or optical filters to filter light and convert the optical signal to an electrical signal, amplifying the electrical signal and loading it into the laser's modulator to form an oscillation loop.

[0003] During the implementation of the present invention, the inventors discovered that the prior art suffers from at least the following problems: Among the aforementioned methods, the first is currently the most mature, but its phase noise and stability performance are relatively poor. The second method offers extremely high stability and phase noise performance, but the equipment is bulky and heavy, limiting its application. The third method, in which an ultrastable laser is locked to an optical resonator, can achieve extremely high stability and phase noise performance. However, due to wavelength drift and aging of the laser, the continuous operation time is short, the optical path structure is complex, and the cost is high. The optoelectronic oscillator method achieves better phase noise performance, has a compact structure, long continuous operation time, and a wide range of applications. The main components of an optoelectronic oscillator are a laser, an optical filter cavity (typically composed of an optical fiber or a micro-nanostructured optical filter cavity), a photodetector, an electrical amplifier, and an optical modulator. Based on the main operating principle, various optoelectronic oscillators can be constructed by selecting different components to generate high-quality microwave signals. However, due to the use of conventional single-mode optical fiber, dispersion effects can cause the optical carrier to broaden, which in turn broadens the microwave signal, affecting the phase noise.

[0004] Therefore, it is necessary to provide a photogenerated microwave source system and method based on a double-ring structure. Summary of the Invention

[0005] The object of the present invention is to provide a photogenerated microwave source system and method based on a double-ring structure to solve at least one of the problems existing in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a photogenerated microwave source system based on a dual-ring structure, the system comprising a dual-wavelength semiconductor laser, an optoelectronic oscillator and a laser current control module, wherein:

[0008] The dual-wavelength semiconductor laser is used to form photon filtering and output a filtered laser beam;

[0009] The optoelectronic oscillator includes a signal adjustment unit for converting an optical signal into an electrical signal and modulating the electrical signal, wherein the signal adjustment unit generates a microwave signal of the microwave source system;

[0010] The laser current control module is used to control the dual-wavelength semiconductor laser and change the output frequency of the microwave signal.

[0011] Optionally, the optoelectronic oscillator includes a phase modulator, a photoelectric conversion unit and a signal adjustment unit, wherein

[0012] The phase modulator is used to phase modulate the laser beam output by the dual-wavelength semiconductor laser;

[0013] The photoelectric conversion unit is used to convert the modulated optical signal into an electrical signal;

[0014] The signal adjustment unit is used to amplify and filter the electrical signal output by the photoelectric conversion unit and split the electrical signal, and output the microwave signal of the microwave source system.

[0015] Optionally, the photoelectric conversion unit includes a first coupler, a first periodic optical fiber, a first photodetector, a second periodic optical fiber and a second photodetector, wherein:

[0016] The first coupler is used to split the modulated optical signal, wherein the first optical signal after splitting is transmitted to the first periodic optical fiber, and the second optical signal is transmitted to the second periodic optical fiber;

[0017] The first periodic optical fiber and the second periodic optical fiber are used to reduce dispersion;

[0018] The first optical detector is used to convert the optical signal output by the first periodic optical fiber into a first electrical signal, and the second optical detector is used to convert the optical signal output by the second periodic optical fiber into a second electrical signal.

[0019] Optionally, the first periodic optical fiber is a long-period single-mode optical fiber plus a dispersion-compensating optical fiber, and the second periodic optical fiber is a long-period single-mode optical fiber plus a dispersion-compensating optical fiber whose total optical fiber length is different from that of the first periodic optical fiber.

[0020] Optionally, the photoelectric conversion unit further includes a second coupler, and the second coupler is used to couple the first electrical signal and the second electrical signal into one electrical signal for output.

[0021] Optionally, the signal adjustment unit includes an electrical amplifier and a third coupler, wherein:

[0022] The electrical amplifier is used to amplify the electrical signal output by the second coupler;

[0023] The third coupler is used to split the microwave signal. The first microwave signal after splitting is output to the phase modulator to drive the laser beam output by the dual-wavelength semiconductor laser, and the second signal is output as the microwave signal of the microwave source system.

[0024] Optionally, the system further comprises a filter located between the electrical amplifier and the third coupler, wherein the filter is configured to cause the electrical signal to oscillate to generate a microwave signal when the gain of the filter is greater than the loss.

[0025] Optionally, after the microwave signal is output, the laser current control module adjusts the output frequency of the microwave by adjusting the output current of the laser current control module.

[0026] A second aspect of the present invention provides a method for optically generating microwaves based on a dual-ring structure, the method comprising: a dual-wavelength semiconductor laser inputting a filtered laser beam into an optoelectronic oscillator;

[0027] The optoelectronic oscillator converts the optical signal into an electrical signal, modulates the electrical signal, and outputs a microwave signal after being split by the third coupler;

[0028] After the microwave signal is output, the dual-wavelength semiconductor laser is controlled by changing the output current of the laser current control module to change the output frequency of the microwave signal.

[0029] Optionally, the optoelectronic oscillator converts the optical signal into an electrical signal and modulates the electrical signal, and the microwave signal output after being split by the third coupler includes:

[0030] performing phase modulation on the filtered laser beam output by the dual-wavelength semiconductor laser;

[0031] Converting the modulated optical signal into an electrical signal;

[0032] The electrical signal output by the photoelectric conversion unit is amplified, filtered and split, and the microwave signal of the microwave source system is output.

[0033] The beneficial effects of the present invention are as follows:

[0034] The present invention provides a photogenerated microwave source system and method based on a dual-ring structure. A dual-wavelength semiconductor laser is used to construct an optoelectronic oscillator. By adopting a dual-ring structure in an optical fiber link, each periodic optical fiber adopts a mode of long-period single-mode fiber plus dispersion-compensating fiber, thereby minimizing the influence of dispersion, improving the phase noise index of the microwave signal, and realizing tuning of the output microwave frequency by changing the output current of the laser current control module. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] Figure 1 A schematic diagram showing a photogenerated microwave source system based on a double-ring structure.

[0037] Reference numerals:

[0038] 1. Dual-wavelength semiconductor laser 2. Phase modulator 3. First coupler

[0039] 4-1 First periodic optical fiber 4-2 Second periodic optical fiber 5 First optical detector

[0040] 6 second photodetector 7 second coupler 8 electrical amplifier

[0041] 9 filter 10 third coupler 11 laser current control module DETAILED DESCRIPTION

[0042] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0043] Example 1

[0044] Embodiment 1 provides a photogenerated microwave source system based on a dual-ring structure, the system comprising a dual-wavelength semiconductor laser, an optoelectronic oscillator and a laser current control module, wherein:

[0045] Dual-wavelength semiconductor laser, used to form photon filtering and output filtered laser beam;

[0046] The optoelectronic oscillator includes a signal adjustment unit for converting the optical signal into an electrical signal and amplifying and filtering the electrical signal. The signal adjustment unit generates a microwave signal for the microwave source system.

[0047] The laser current control module is used to control the dual-wavelength semiconductor laser and change the output frequency of the microwave signal.

[0048] Specifically, a dual-wavelength semiconductor laser refers to a laser with two frequencies. The two frequencies can form a photon filtering effect, that is, the wavelength interval is the bandwidth of the optical filter, which can filter the microwave signal in the loop.

[0049] The optoelectronic oscillator (OEO) refers to the loop formed by devices 2-10. Its main principle is that when noise passes through the optical fiber loop and is filtered by a filter, and the loop's gain exceeds the loss, the electrical signal oscillates to form a microwave signal. The loop formed by the two optical fibers 4-1-5-7 and 4-2-6-7 is a dual-loop structure. Using a long-period single-mode fiber plus dispersion-compensating fiber, it improves the microwave signal's phase noise level and reduces dispersion.

[0050] The optoelectronic oscillator includes a phase modulator, a photoelectric conversion unit and a signal adjustment unit, wherein the phase modulator is used to phase modulate the laser beam output by the dual-wavelength semiconductor laser;

[0051] The photoelectric conversion unit includes a first coupler, a first periodic optical fiber, a first light detector, a second periodic optical fiber, a second light detector, and a second coupler, wherein the first coupler is used to split the modulated optical signal, and the first light signal after splitting is transmitted to the first periodic optical fiber, and the second light signal is transmitted to the second periodic optical fiber; the first periodic optical fiber is a long-period single-mode optical fiber plus a dispersion-compensating optical fiber, and the layout of the second periodic optical fiber is basically similar to that of the first periodic optical fiber, but the total fiber length of the second periodic optical fiber is different from the total fiber length of the first periodic optical fiber, and the length difference is generally 10m to several hundred meters; the first light detector and the second light detector can detect the light power incident on their surfaces and convert the change in the light power into the corresponding first electrical signal and second electrical signal; the second coupler couples the two electrical signals into one electrical signal and transmits it to the signal adjustment module;

[0052] The first periodic optical fiber, the first photodetector, the second periodic optical fiber, the second photodetector, and the second coupler in the photoelectric conversion unit form a dual-ring structure, which can improve the spurious suppression and phase noise levels in the gain competition mode. The dual-ring structure adopts a long-period single-mode optical fiber plus a dispersion-compensating optical fiber mode to improve the phase noise level of the microwave signal and reduce dispersion.

[0053] The signal adjustment unit includes an electrical amplifier, a filter and a third coupler. The electrical amplifier is used to amplify the electrical signal output by the second coupler. When the gain of the filter is greater than the loss, the filter oscillates the electrical signal to form a microwave signal. The third coupler is used to split the microwave signal output by the filter. The first microwave signal after splitting is output to the phase modulator to drive the laser beam output by the dual-wavelength semiconductor laser, and the second signal is output as the final microwave signal of the microwave source system.

[0054] After the final microwave signal is output, the frequency of the microwave signal is tuned by controlling the dual-wavelength semiconductor laser by changing the output current of the laser current control module.

[0055] In a specific embodiment, the connection mode of a photogenerated microwave source system based on a double-ring structure provided by the present invention is:

[0056] The output end of the dual-wavelength semiconductor laser is connected to the input end of the phase modulator, the output end of the phase modulator is connected to the input end of the first coupler, one end of the output end of the first coupler is connected to the input end of the first periodic optical fiber, and the other output end is connected to the input end of the second periodic optical fiber, the output end of the first periodic optical fiber is connected to the input end of the first photodetector, the output end of the second periodic optical fiber is connected to the input end of the second photodetector, the output ends of the first photodetector and the second photodetector are both connected to the input end of the second coupler, the output end of the second coupler is connected to the input end of the electrical amplifier, the output end of the electrical amplifier is connected to the input end of the filter, the output end of the filter is connected to the input end of the third coupler, one end of the output end of the third coupler is connected to the input end of the phase modulator, and the other output end directly outputs a microwave signal, and the output end of the laser current control module is connected to the input end of the dual-wavelength semiconductor laser.

[0057] Example 2

[0058] Example 2 provides a method for photogenerating microwaves based on a double-ring structure, the method comprising:

[0059] The dual-wavelength semiconductor laser inputs the filtered laser beam into the optoelectronic oscillator;

[0060] The photoelectric conversion unit in the photoelectric oscillator converts the optical signal into an electrical signal. The signal adjustment unit amplifies and filters the electrical signal and forms a microwave signal after filtering. The microwave signal is directly output after being split by the third coupler.

[0061] After the microwave signal is output, the dual-wavelength semiconductor laser is controlled by changing the output current of the laser current control module to tune the frequency of the microwave signal.

[0062] Specifically, the dual-wavelength semiconductor laser outputs a wavelength in the C-band. The laser beam emitted by the dual-wavelength semiconductor laser passes through a phase modulator and enters a first coupler. After being split by the first coupler, it enters a first periodic optical fiber and a second periodic optical fiber, respectively. The first periodic optical fiber is a long-period single-mode optical fiber combined with a dispersion-compensating optical fiber. For example, a 1km length of G.652 single-mode optical fiber directly fused to 10m of G.652 dispersion-compensating optical fiber forms a periodic structure. The long-period single-mode optical fiber combined with the dispersion-compensating optical fiber contains 5-15 such periodic structures. The second periodic optical fiber has a similar fiber layout to the first periodic optical fiber, but the total optical length of the second periodic optical fiber differs from that of the first periodic optical fiber, typically by 10m to several hundred meters. After passing through the first periodic optical fiber and the second periodic optical fiber, the optical signal enters the first photodetector and the second photodetector respectively and is converted into a first electrical signal and a second electrical signal. The two electrical signals are coupled and combined into one electrical signal after passing through the second coupler. The coupled electrical signal is amplified by an electrical amplifier and then passes through a filter. When the gain in the loop is greater than the loss, the electrical signal can oscillate and form a microwave signal output. The filter has a large bandwidth, generally 10 to 20 GHz, and is selected according to the tuning range of the required microwave center frequency; the filtered microwave signal enters the third coupler, and the third coupler is divided into two paths. The first path is connected to the phase modulator to drive the dual-wavelength semiconductor laser, and the other path is directly output as the microwave signal of the microwave source system.

[0063] After the microwave signal is output, the laser current control module adjusts the output frequency of the microwave by adjusting its output current.

[0064] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper" and "lower" is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0065] It should also be noted that, in the description of the present invention, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0066] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A photogenerated microwave source system based on a double-ring structure, characterized in that: include: Dual-wavelength semiconductor laser, optoelectronic oscillator and laser current control module, wherein: The dual-wavelength semiconductor laser is used to form photon filtering and output a filtered laser beam; The optoelectronic oscillator includes a signal adjustment unit for converting an optical signal into an electrical signal and modulating the electrical signal, wherein the signal adjustment unit generates a microwave signal of the microwave source system; The laser current control module is used to control the dual-wavelength semiconductor laser to change the output frequency of the microwave signal; The optoelectronic oscillator includes a phase modulator, a photoelectric conversion unit and a signal adjustment unit, wherein The phase modulator is used to phase modulate the laser beam output by the dual-wavelength semiconductor laser; The photoelectric conversion unit is used to convert the modulated optical signal into an electrical signal; The signal adjustment unit is used to amplify, filter and split the electrical signal output by the photoelectric conversion unit, and output the microwave signal of the microwave source system; The photoelectric conversion unit includes a first coupler, a first periodic optical fiber, a first photodetector, a second periodic optical fiber and a second photodetector, wherein: The first coupler is used to split the modulated optical signal, wherein the first optical signal after splitting is transmitted to the first periodic optical fiber, and the second optical signal is transmitted to the second periodic optical fiber; The first periodic optical fiber and the second periodic optical fiber are used to reduce dispersion; The first optical detector is used to convert the optical signal output by the first periodic optical fiber into a first electrical signal, and the second optical detector is used to convert the optical signal output by the second periodic optical fiber into a second electrical signal.

2. The system according to claim 1, wherein: The first periodic optical fiber is a long-period single-mode optical fiber plus a dispersion-compensating optical fiber, and the second periodic optical fiber is a long-period single-mode optical fiber plus a dispersion-compensating optical fiber, the total length of which is different from that of the first periodic optical fiber.

3. The system according to claim 1, wherein: The photoelectric conversion unit further includes a second coupler, and the second coupler is used to couple the first electrical signal and the second electrical signal into one electrical signal for output.

4. The system according to claim 3, characterized in that The signal conditioning unit comprises an electrical amplifier and a third coupler, wherein: The electrical amplifier is used to amplify the electrical signal output by the second coupler; The third coupler is used to split the microwave signal. The first microwave signal after splitting is output to the phase modulator to drive the laser beam output by the dual-wavelength semiconductor laser, and the second microwave signal is directly output as the microwave signal of the microwave source system.

5. The system according to claim 4, characterized in that The system further includes a filter located between the electrical amplifier and the third coupler, and configured to cause the electrical signal to oscillate to generate a microwave signal when the gain of the filter is greater than the loss.

6. The system according to claim 1, wherein: After the microwave signal is output, the laser current control module adjusts the output frequency of the microwave by adjusting the output current of the laser current control module.

7. A photogenerated microwave method based on a double ring structure, characterized in that: The method is a photogenerated microwave source system based on a double-ring structure according to any one of claims 1 to 6, the method comprising: The dual-wavelength semiconductor laser inputs the filtered laser beam into the optoelectronic oscillator; The optoelectronic oscillator converts the optical signal into an electrical signal, modulates the electrical signal, and outputs a microwave signal after being split by the third coupler; After the microwave signal is output, the dual-wavelength semiconductor laser is controlled by changing the output current of the laser current control module to change the output frequency of the microwave signal.

8. The method according to claim 7, characterized in that The photoelectric oscillator converts the optical signal into an electrical signal and modulates the electrical signal. The microwave signal is output after being split by the third coupler. performing phase modulation on the filtered laser beam output by the dual-wavelength semiconductor laser; Converting the modulated optical signal into an electrical signal; The electrical signal output by the photoelectric conversion unit is amplified, filtered and split, and the microwave signal of the microwave source system is output.

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