CN115865211A - Microwave frequency shift method and device based on light injection locking - Google Patents
Microwave frequency shift method and device based on light injection locking Download PDFInfo
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Abstract
The invention discloses a microwave frequency shift method based on optical injection locking. Dividing the continuous single-frequency optical carrier into three paths; carrying out carrier suppression single-sideband modulation on a first path of continuous single-frequency optical carrier by using a microwave signal to be frequency shifted to obtain signal light; the method comprises the steps that a second path of continuous single-frequency optical carrier is used as an injection optical signal, the injection optical signal is injected into a slave laser and enables the slave laser to work in an injection locking mode of a single-period oscillation state, the phase and the power of a third path of continuous single-frequency optical carrier are adjusted to enable the phase and the power of the third path of continuous single-frequency optical carrier to be equal to the injection locking optical signal output by the slave laser in size and opposite in phase, then the two signals are coupled into one path, and a local oscillator optical signal only containing red shift resonance components of the slave laser is obtained; and finally, performing beat frequency on the local oscillator optical signal and the signal light to obtain a microwave signal after frequency shift. The invention also discloses a microwave frequency shift device based on the optical injection locking. Compared with the prior art, the invention can tune the frequency shift quantity in a large range and improve the spurious suppression effect.
Description
Technical Field
The invention relates to a microwave frequency shift method, and belongs to the technical field of microwave photons.
Background
The microwave frequency shifter is a device capable of changing the frequency of an input microwave signal, and is widely applied to systems such as electronic countermeasure, doppler velocity measurement, radar equipment test, communication channelization reception and the like. The traditional microwave signal frequency shift method mainly utilizes a microwave I/Q mixer to realize single sideband modulation. However, under the influence of the electronic I/Q mixer, the problems of narrow working bandwidth, I/Q amplitude-phase imbalance and the like generally exist, and it is gradually difficult to meet the urgent needs of radar, electronic countermeasure and other systems for large instantaneous bandwidth, wide frequency band coverage and low spurious distortion capability.
Microwave photonics is an emerging interdisciplinary subject combining microwave technology and photonics technology, mainly studies the interaction between microwaves and light, and can overcome the advantages of the traditional microwave technology in the aspects of processing speed, transmission bandwidth and the like. Compared with the traditional electronic system, the microwave photonic system has the advantages of wide working frequency band, large transmission bandwidth, small transmission loss, strong anti-electromagnetic interference capability and the like, and can realize high-quality generation, transmission and processing of microwave signals. This allows the microwave photonic system to still have a flat response in the face of large bandwidth signals. In addition, the photoelectronic device has small volume and light weight, and can be applied to various scenes. The microwave signal frequency shift technology based on microwave photons is expected to overcome the electronic bottleneck problem of an analog electronic system and provide a more effective solution for ultra-wideband microwave signal frequency shift.
The currently reported microwave photon-based microwave signal frequency shift method mainly comprises the following steps: acousto-optic frequency shift (AOFS), sawtooth wave phase modulation (SPM) and microwave photon I/Q modulation.
The 3 microwave photon frequency shift methods benefit from the large bandwidth characteristic of the photon technology, and have wider working frequency range and instantaneous bandwidth. Accurate microwave signal frequency shift can be realized to the frequency shift mode based on AOFS, and the frequency spectrum is pure after the frequency shift, and stray rejection ratio is high, and stability is good. However, the AOFS requires high power for the driving signal, and since the center frequency of the AOFS is fixed, the frequency shift amount tuning is poor. The frequency shift mode based on SPM can realize the frequency shift of microwave signals with any frequency and different directions by changing the amplitude, the frequency and the duty ratio of sawtooth waves, and has high tunability and lower system cost. However, after frequency shift, the sideband spurious suppression ratio is greatly influenced by the quality of a sawtooth wave signal, and the frequency shift amount is limited by a digital-to-analog converter. The microwave photon frequency shift method based on I/Q modulation has a large frequency shift range and good tuning characteristics, but stray rejection is more sensitive than the amplitude-phase imbalance degree of I/Q signals, and the modulation efficiency of a Mach-Zehnder modulator is relatively low, so that the frequency shift efficiency is low. In addition, in order to improve the spurious suppression ratio, the modulator is required to have a high extinction ratio, and the I/Q signal has a high degree of amplitude-phase balance.
Due to the fact that the scheme has the problems of poor structure tunability, limited frequency shift amount, low spurious suppression ratio, high photoelectric requirement and the like. Therefore, a simple and easy-to-implement scheme is needed to implement frequency shift of the optical microwave signal, perform wide-range tuning on the frequency shift amount, and improve the spurious suppression effect.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a microwave frequency shift method based on optical injection locking, which can be used for tuning the frequency shift quantity in a large range and improving the spurious suppression effect.
The invention specifically adopts the following technical scheme to solve the technical problems:
dividing a continuous single-frequency optical carrier into three paths based on a microwave frequency shift method of light injection locking; carrying out carrier suppression single-sideband modulation on a first path of continuous single-frequency optical carrier by using a microwave signal to be frequency shifted to obtain signal light; the method comprises the steps that a second path of continuous single-frequency optical carrier is used as an injection optical signal and injected into a slave laser, the slave laser works in an injection locking mode of a single-period oscillation state, the phase and the power of a third path of continuous single-frequency optical carrier are adjusted to enable the phase and the power of the third path of continuous single-frequency optical carrier to be equal to and opposite to those of an injection locking optical signal output by the slave laser, then the two signals are coupled into one path, and a local oscillation optical signal only containing red shift resonance components of the slave laser is obtained; finally, the local oscillation optical signal and the signal light are subjected to beat frequency to obtain frequency of | f 0 -f 1 -f 2 I shifted microwave signal, wherein f 0 For the frequency, f, of said continuous single-frequency optical carrier 1 To be shifted in frequency, f, of the microwave signal 2 Is a red-shifted resonant component from the laser.
Further, the frequency shift amount is adjusted by adjusting the light injection intensity.
Based on the same inventive concept, the following technical scheme can be obtained:
microwave frequency shift device based on optical injection locking includes:
the light beam splitting module is used for splitting the continuous single-frequency light carrier into three paths;
the modulation module is used for carrying out carrier suppression single-sideband modulation on a first path of continuous single-frequency optical carrier by using a microwave signal to be subjected to frequency shift to obtain signal light;
the local oscillator optical construction module is used for injecting a second path of continuous single-frequency optical carrier serving as an injection optical signal into the slave laser and enabling the slave laser to work in an injection locking mode of a single-period oscillation state, adjusting the phase and the power of a third path of continuous single-frequency optical carrier to enable the phase and the power of the third path of continuous single-frequency optical carrier to be equal to and opposite to the injection locking optical signal output by the slave laser in magnitude, and then coupling the two signals into one path to obtain a local oscillator optical signal only containing red shift resonance components of the slave laser;
photoelectric detection module, useThe local oscillator optical signal and the signal light are subjected to beat frequency to obtain frequency of | f 0 -f 1 -f 2 I shifted microwave signal, wherein f 0 For the frequency, f, of said continuous single-frequency optical carrier 1 To be shifted in frequency, f, of the microwave signal 2 Is a red-shifted resonant component from the laser.
Further, the frequency shift amount is adjusted by adjusting the light injection intensity.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
the invention modulates the microwave signal to the optical domain to obtain the signal light, adopts the light injection locking technology and the phase cancellation technology to construct the local oscillator light with adjustable frequency, outputs the microwave signal after frequency shift after the beat frequency of the signal light and the local oscillator light, and adjusts the frequency shift amount in a large range by adjusting the light injection intensity. The invention realizes the frequency shift of the microwave signal by utilizing the optical injection locking technology, and can effectively solve the problems of poor tunability, limited frequency shift amount, low spurious suppression ratio, high photoelectric requirement and the like in the conventional microwave frequency shift technology.
Drawings
FIG. 1 is a schematic structural diagram of a microwave frequency shift device according to an embodiment of the present invention;
FIG. 2 is a diagram of a specific structure for implementing carrier-suppressed single-sideband modulation;
fig. 3 is a schematic diagram illustrating a principle of generating and adjusting a local oscillator optical signal.
Detailed Description
Aiming at the defects of the prior art, the solution of the invention is to modulate a microwave signal to an optical domain to obtain a signal light, construct a local oscillator light with adjustable frequency by adopting an optical injection locking technology and a phase cancellation technology, beat frequency of the signal light and the local oscillator light and output the microwave signal after frequency shift, and adjust the frequency shift amount in a large range by adjusting the light injection intensity.
The technical scheme provided by the invention is as follows:
dividing a continuous single-frequency optical carrier into three paths based on a microwave frequency shift method of light injection locking; connecting the first path with a microwave signal to be shifted in frequencyCarrying out carrier suppression single-sideband modulation on the continuous single-frequency optical carrier to obtain signal light; the method comprises the steps that a second path of continuous single-frequency optical carrier is used as an injection optical signal and injected into a slave laser, the slave laser works in an injection locking mode of a single-period oscillation state, the phase and the power of a third path of continuous single-frequency optical carrier are adjusted to enable the phase and the power of the third path of continuous single-frequency optical carrier to be equal to and opposite to those of an injection locking optical signal output by the slave laser, then the two signals are coupled into one path, and a local oscillation optical signal only containing red shift resonance components of the slave laser is obtained; finally, the local oscillator optical signal and the signal light are subjected to beat frequency to obtain a frequency | f 0 -f 1 -f 2 I shifted microwave signal, wherein f 0 For the frequency, f, of said continuous single-frequency optical carrier 1 To be shifted in frequency, f, of the microwave signal 2 Is a red-shifted resonant component from the laser.
Microwave frequency shift device based on optical injection locking includes:
the light beam splitting module is used for splitting the continuous single-frequency light carrier into three paths;
the modulation module is used for carrying out carrier suppression single-sideband modulation on a first path of continuous single-frequency optical carrier by using a microwave signal to be subjected to frequency shift to obtain signal light;
the local oscillator optical construction module is used for injecting a second path of continuous single-frequency optical carrier serving as an injection optical signal into the slave laser and enabling the slave laser to work in an injection locking mode of a single-period oscillation state, adjusting the phase and the power of a third path of continuous single-frequency optical carrier to enable the phase and the power of the third path of continuous single-frequency optical carrier to be equal to and opposite to the injection locking optical signal output by the slave laser in magnitude, and then coupling the two signals into one path to obtain a local oscillator optical signal only containing red shift resonance components of the slave laser;
a photoelectric detection module for beat-frequency the local oscillation optical signal and the signal light to obtain a frequency of f 0 -f 1 -f 2 I shifted microwave signal, wherein f 0 For the frequency, f, of said continuous single-frequency optical carrier 1 To be shifted in frequency, f, of the microwave signal 2 Is a red-shifted resonant component from the laser.
For the public understanding, the technical scheme of the invention is explained in detail by a specific embodiment and the accompanying drawings:
the microwave frequency shift device in this embodiment is shown in fig. 1, and includes a master laser, a slave laser, a beam splitter, a modulation module, an attenuator 1, an attenuator 2, a phase shifter, a polarization controller, a circulator, an optical coupler, and a photodetector.
The working process and the principle of the device are as follows:
1) As shown in fig. 1, the continuous single-frequency optical carrier outputted from the laser is divided into three paths by the beam splitter, and the frequency of each continuous single-frequency optical carrier is f 0 ；
2) Taking a single tone signal as an example (actually, the single tone signal may be a chirp signal or a phase-coded signal of a radar system, or an amplitude modulation signal, a phase modulation signal or a vector modulation signal of a communication system, etc.), the frequency of the microwave signal is f 1 The modulated carrier suppression single sideband signal obtained by the modulation module is signal light with the frequency f 0 -f 1 ；
3) One path of continuous single-frequency optical carrier enters a port 1 of the circulator after passing through the attenuator 1 and the polarization controller, a port 2 of the circulator is connected with the slave laser, and a port 3 of the circulator outputs a signal to enter the optical coupler;
4) The other continuous single-frequency optical carrier enters the optical coupler after passing through the phase shifter and the attenuator 2, two signals are coupled into one path, the output signal of the coupler is an optical local oscillation signal obtained after the frequency of the optical spectrum of the laser is shifted, and the frequency of the optical local oscillation signal is f 2 ；
5) The local oscillation light and the signal light enter two input ends of the photoelectric detector, the beat frequency is finished in the photoelectric detector, and the final output signal frequency is | f 0 -f 1 -f 2 And realizing the frequency shift of the microwave signal.
The modulation module in the embodiment realizes the carrier suppression single sideband modulation through a 90-degree electric bridge and a double parallel Mach-Zehnder modulator, and can also be realized through other existing or future technologies such as a modulator light receiving filter and the like; fig. 2 shows a block diagram of a dual parallel mach-zehnder modulator, consisting of two sub MZMs: MZM1, MZM2 and one main MZM: MZM3 is constructed with two sub MZMs embedded in the upper and lower arms of the main MZM, respectively. In addition, the main modulator MZM3 only has a direct current bias voltage input port, controls the direct current bias voltage of MZM3, can adjust the phase place of MZM2 output optical signal. Microwave signals pass through a 90-degree electric bridge and then are input to a radio frequency port of the double-parallel Mach-Zehnder modulator, and bias voltages of three MZMs are adjusted to enable:
at the moment, the carrier suppression single-sideband modulation can be realized, the positive first-order sideband and the carrier are suppressed, and the output of the modulation module is the modulated negative first-order sideband.
The following describes the structure and the adjustment method of the local oscillator light with reference to fig. 1 and 3:
as shown in fig. 1, one of the continuous single-frequency optical carriers output by the optical splitter passes through an attenuator 1 and a polarization controller and then is injected into the slave laser through a circulator, and an output optical signal from the slave laser is output through the circulator. As shown in fig. 3, the optical wave output from the laser has a frequency f s Power of P s Frequency of injected light f 0 With a power of P 0 Injection intensity ξ = P 0 /P s Detuning frequency of f i ＝f 0 -f s The injected light is injected into the slave laser through the circulator, the phase of the slave laser is locked, and the intra-cavity oscillation is locked at the frequency f 0 -f 2 And, under light injection conditions, the required intracavity gain of the slave laser will decrease, the refractive index of the intracavity gain medium will increase, resulting in an increase in the equivalent cavity length of the slave laser, and hence the cavity resonant frequency from f s Red shift to f 2 . By adjusting the injection light intensity and the light frequency detuning quantity, various nonlinear dynamic states of the slave laser can be excited, including steady-state locking, single-period oscillation, multiple-period oscillation and chaotic oscillation states. Wherein the monocycle oscillation occupiesThe single-cycle oscillation frequency of the light-injecting semiconductor laser can be tuned over a wide range, taking into account most of the state space. In the four dynamic states of light injection locking, the invention utilizes a single period oscillation state to realize frequency shift of a slave laser light signal. In the single-period oscillation state, laser oscillation excited by light injection and red shift cavity resonance caused by the light injection have dynamic competition in the slave laser, and the dynamic characteristic of the semiconductor laser is changed. At a suitable injection strength and detuning frequency, a split-uniform optical double sideband signal is generated due to Hopflug splitting, with sideband separation f m ＝f 0 -f 2 This frequency is called the monocycle oscillation frequency. Under the condition that the detuning frequency is constant, the red shift resonance component light frequency is gradually reduced along with the increase of the light injection intensity, and the red shift resonance component light frequency moves towards the direction departing from the injection light frequency, so that the local oscillation light signal frequency can be adjusted by adjusting the injection light intensity.
The other path of continuous single-frequency optical carrier output by the beam splitter is coupled with an injection locking optical signal output by a laser in an optical coupler through a phase shifter and an attenuator 2, the two coupled optical signals are equal in size and opposite in phase by adjusting the parameters of the phase shifter and the attenuator 2, so that spectrum cancellation is realized, the signal output by the coupler only has a red shift resonance component, so that a local oscillator signal is obtained, the red shift frequency of the optical spectrum of the laser can be changed by adjusting the injection intensity of light, and local oscillator light with different frequencies is obtained.
Finally, the local oscillator light and the signal light are subjected to beat frequency in the photoelectric detector, and finally the frequency of | f is obtained 0 -f 1 -f 2 The shifted microwave signal of l. The amount of frequency shift of the microwave signal can be adjusted by the attenuator 1.
Claims (4)
1. The microwave frequency shift method based on light injection locking is characterized in that a continuous single-frequency light carrier is divided into three paths; carrying out carrier suppression single-sideband modulation on a first path of continuous single-frequency optical carrier by using a microwave signal to be frequency shifted to obtain signal light; a second path of continuous single-frequency optical carrier is used as an injection optical signal, and is injected into the slave laser to enable the slave laser to be subjected to laser amplificationThe device works in an injection locking mode of a single-period oscillation state, the phase and the power of a third path of continuous single-frequency optical carrier are adjusted to enable the phase and the power to be equal to the injection locking optical signal output from the laser and opposite to the phase, and then the two signals are coupled into one path to obtain a local oscillator optical signal only containing red shift resonance components of the slave laser; finally, the local oscillation optical signal and the signal light are subjected to beat frequency to obtain frequency of | f 0 -f 1 -f 2 I shifted microwave signal, wherein f 0 For the frequency, f, of said continuous single-frequency optical carrier 1 To be shifted in frequency, f, of the microwave signal 2 Is a red-shifted resonant component from the laser.
2. The method of claim 1, wherein the amount of frequency shift is adjusted by adjusting the intensity of light injection.
3. Microwave frequency shift device based on light injection locking, characterized by that includes:
the optical beam splitting module is used for splitting the continuous single-frequency optical carrier into three paths;
the modulation module is used for carrying out carrier suppression single-sideband modulation on a first path of continuous single-frequency optical carrier by using a microwave signal to be subjected to frequency shift to obtain signal light;
the local oscillator optical construction module is used for injecting a second path of continuous single-frequency optical carrier serving as an injection optical signal into the slave laser and enabling the slave laser to work in an injection locking mode of a single-period oscillation state, adjusting the phase and the power of a third path of continuous single-frequency optical carrier to enable the phase and the power of the third path of continuous single-frequency optical carrier to be equal to and opposite to the injection locking optical signal output by the slave laser in magnitude, and then coupling the two signals into one path to obtain a local oscillator optical signal only containing red shift resonance components of the slave laser;
a photoelectric detection module for beat-frequency the local oscillation optical signal and the signal light to obtain a frequency of f 0 -f 1 -f 2 I shifted microwave signal, wherein f 0 For the frequency, f, of said continuous single-frequency optical carrier 1 For the frequency of the microwave signal to be shifted, f 2 Is a red-shifted resonant component from the laser.
4. A microwave frequency-shifting apparatus based on optical injection locking according to claim 3, wherein the amount of frequency shift is adjusted by adjusting the intensity of the optical injection.
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| CN117554930A (en) * | 2024-01-12 | 2024-02-13 | 北醒（北京）光子科技有限公司 | Frequency modulation continuous wave light source system and frequency modulation continuous wave laser radar |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117554930A (en) * | 2024-01-12 | 2024-02-13 | 北醒（北京）光子科技有限公司 | Frequency modulation continuous wave light source system and frequency modulation continuous wave laser radar |
| CN117554930B (en) * | 2024-01-12 | 2024-03-12 | 北醒（北京）光子科技有限公司 | Frequency modulation continuous wave light source system and frequency modulation continuous wave laser radar |
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