CN115865211B - Microwave frequency shifting method and device based on optical injection locking - Google Patents
Microwave frequency shifting method and device based on optical injection locking Download PDFInfo
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Abstract
本发明公开了一种基于光注入锁定的微波移频方法。将连续单频光载波分为三路；用待移频微波信号对第一路连续单频光载波进行载波抑制单边带调制，得到信号光；以第二路连续单频光载波作为注入光信号，将其注入从激光器并使得该从激光器工作于单周期振荡状态的注入锁定模式，调节第三路连续单频光载波的相位和功率使得其与从激光器输出的注入锁定光信号大小相等而相位相反，然后将这两个信号耦合为一路，得到只包含从激光器的红移谐振分量的本振光信号；最后对本振光信号与信号光进行拍频，得到移频后微波信号。本发明还公开了一种基于光注入锁定的微波移频装置。相比现有技术，本发明能够对移频量进行大范围调谐，又能提高杂散抑制效果。
The present invention discloses a microwave frequency shifting method based on optical injection locking. A continuous single-frequency optical carrier is divided into three paths; the first path of continuous single-frequency optical carrier is subjected to carrier suppression single-sideband modulation with the microwave signal to be frequency-shifted to obtain signal light; the second path of continuous single-frequency optical carrier is used as the injection optical signal, injected into the slave laser and makes the slave laser work in the injection locking mode of a single-cycle oscillation state, the phase and power of the third path of continuous single-frequency optical carrier are adjusted so that it is equal to the injection locking optical signal output from the slave laser but opposite in phase, and then the two signals are coupled into one path to obtain a local oscillator optical signal containing only the red-shifted resonant component of the slave laser; finally, the local oscillator optical signal is beat with the signal light to obtain a frequency-shifted microwave signal. The present invention also discloses a microwave frequency shifting device based on optical injection locking. Compared with the prior art, the present invention can tune the frequency shift amount over 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 channelized reception and the like. The traditional microwave signal frequency shift method mainly utilizes a microwave I/Q mixer to realize single-sideband modulation. However, due to the influence of the electronic I/Q mixer, the problems of narrow working bandwidth, unbalanced I/Q amplitude and the like generally exist, and the urgent needs of the radar, electronic countermeasure and other systems on large instantaneous bandwidth, wide-band coverage and low spurious distortion capability are gradually difficult to meet.
Microwave photonics is an emerging interdisciplinary science combining microwave technology and photonics technology, and is mainly used for researching interaction of microwaves and light, and microwave photonics 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 photon system has the advantages of wide working frequency band, large transmission bandwidth, small transmission loss, strong electromagnetic interference resistance 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 can be expected to overcome the electronic bottleneck problem faced by an analog electronic system, and a more effective solution is provided for ultra-wideband microwave signal frequency shift.
The currently reported microwave signal frequency shift method based on microwave photons mainly comprises three types of 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 photon technology, and have wider working frequency range and instantaneous bandwidth. The frequency shift mode based on AOFS can realize accurate microwave signal frequency shift, and after frequency shift, the frequency spectrum is pure, the spurious suppression ratio is high, and the stability is good. However, AOFS has a high power requirement on the driving signal, and the center frequency of AOFS is fixed, so that the frequency shift amount is poor in tunability. 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 the sawtooth wave, and has high tunability and lower system cost. However, the sideband spurious suppression after frequency shift is greatly influenced by the quality of the sawtooth signal, and the frequency shift amount is limited by the digital-to-analog converter. The microwave photon frequency shift method based on the I/Q modulation has a large frequency shift range and good tuning characteristics, but the spurious suppression is more sensitive to the amplitude-phase unbalance of the I/Q signal, and the Mach-Zehnder modulator has relatively low modulation efficiency, so that the frequency shift efficiency is low. In addition, to increase the spurious suppression ratio, the modulator is required to have a high extinction ratio and the I/Q signal has a high amplitude-phase balance.
The scheme has the problems of poor structural tunability, limited frequency shift, low spurious suppression ratio, high photoelectric requirement and the like. Therefore, a simple and easy-to-implement scheme is needed to realize the frequency shift of the optical microwave signal, perform large-scale tuning on the frequency shift amount, and improve the spurious suppression effect.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects of the prior art and providing a microwave frequency shift method based on optical injection locking, which can carry out large-scale tuning on frequency shift and improve spurious suppression effect.
The technical scheme adopted by the invention specifically solves the technical problems as follows:
A microwave frequency shift method based on optical injection locking includes dividing continuous single-frequency optical carrier into three paths, carrying out carrier suppression single-sideband modulation on the first path of continuous single-frequency optical carrier by using to-be-shifted microwave signal to obtain signal light, injecting the second path of continuous single-frequency optical carrier as an injection optical signal into a slave laser and enabling the slave laser to work in an injection locking mode of a single-period oscillation state, adjusting the phase and power of the third path of continuous single-frequency optical carrier to enable the third path of continuous single-frequency optical carrier to be equal in size and opposite in phase to the injection locking optical signal output from the laser, coupling the two signals into one path to obtain a local oscillator optical signal only containing red-shifted resonance components of the slave laser, and finally enabling the local oscillator optical signal to beat with the signal light to obtain a frequency shifted microwave signal with the frequency of |f 0-f1-f2 |, wherein f 0 is the frequency of the continuous single-frequency optical carrier, f 1 is the frequency of the to-be-shifted microwave signal, and f 2 is the red-shifted resonance component of the slave laser.
Further, the magnitude of the frequency shift is adjusted by adjusting the light injection intensity.
The following technical scheme can be obtained based on the same inventive concept:
a microwave frequency shifting device based on optical injection locking, comprising:
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 the first path of continuous single-frequency optical carrier by using the microwave signal to be shifted to obtain signal light;
The local oscillator optical construction module is used for taking a second continuous single-frequency optical carrier as an injection optical signal, injecting the second continuous single-frequency optical carrier into an injection locking mode of a slave laser and enabling the slave laser to work in a single-period oscillation state, adjusting the phase and the power of a third continuous single-frequency optical carrier to enable the third continuous single-frequency optical carrier to be equal to the injection locking optical signal output from the laser in size and opposite in phase, and then coupling the two signals into one path to obtain a local oscillator optical signal only comprising a red-shift resonance component of the slave laser;
The photoelectric detection module is used for beating the local oscillation optical signal and the signal light to obtain a frequency-shifted microwave signal with the frequency of |f 0-f1-f2 |, wherein f 0 is the frequency of the continuous single-frequency optical carrier wave, f 1 is the frequency of the microwave signal to be frequency-shifted, and f 2 is the red-shifted resonance component of the slave laser.
Further, the magnitude of the frequency shift 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 into the optical domain to obtain the signal light, adopts the optical injection locking technology and the phase cancellation technology to construct the local oscillation light with adjustable frequency, outputs the microwave signal after frequency shift after the beat frequency of the signal light and the local oscillation light, and adjusts the frequency shift amount in a large range by adjusting the optical injection intensity. The invention utilizes the light injection locking technology to realize the frequency shift of the microwave signal, and can effectively solve the problems of poor tunability, limited frequency shift amount, low spurious suppression ratio, excessively high photoelectric requirement and the like in the existing microwave frequency shift technology.
Drawings
FIG. 1 is a schematic diagram of a microwave frequency shifter according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a specific structure for implementing carrier-suppressed single sideband modulation;
Fig. 3 is a schematic diagram of the generation and adjustment principle of the local oscillation optical signal.
Detailed Description
Aiming at the defects of the prior art, the invention solves the problems that the microwave signal is modulated into the optical domain to obtain the signal light, the local oscillation light with adjustable frequency is constructed by adopting the light injection locking technology and the phase cancellation technology, the frequency-shifted microwave signal is output after the signal light and the local oscillation light beat frequency, and the frequency shift quantity is adjusted in a large range by adjusting the light injection intensity.
The technical scheme provided by the invention is as follows:
A microwave frequency shift method based on optical injection locking includes dividing continuous single-frequency optical carrier into three paths, carrying out carrier suppression single-sideband modulation on the first path of continuous single-frequency optical carrier by using to-be-shifted microwave signal to obtain signal light, injecting the second path of continuous single-frequency optical carrier as an injection optical signal into a slave laser and enabling the slave laser to work in an injection locking mode of a single-period oscillation state, adjusting the phase and power of the third path of continuous single-frequency optical carrier to enable the third path of continuous single-frequency optical carrier to be equal in size and opposite in phase to the injection locking optical signal output from the laser, coupling the two signals into one path to obtain a local oscillator optical signal only containing red-shifted resonance components of the slave laser, and finally enabling the local oscillator optical signal to beat frequency with the signal light to obtain a frequency shifted microwave signal with the frequency of |f 0-f1-f2 |, wherein f 0 is the frequency of the continuous single-frequency optical carrier, f 1 is the frequency of the to-be-shifted microwave signal, and f 2 is the red-shifted resonance component of the slave laser.
A microwave frequency shifting device based on optical injection locking, comprising:
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 the first path of continuous single-frequency optical carrier by using the microwave signal to be shifted to obtain signal light;
The local oscillator optical construction module is used for taking a second continuous single-frequency optical carrier as an injection optical signal, injecting the second continuous single-frequency optical carrier into an injection locking mode of a slave laser and enabling the slave laser to work in a single-period oscillation state, adjusting the phase and the power of a third continuous single-frequency optical carrier to enable the third continuous single-frequency optical carrier to be equal to the injection locking optical signal output from the laser in size and opposite in phase, and then coupling the two signals into one path to obtain a local oscillator optical signal only comprising a red-shift resonance component of the slave laser;
The photoelectric detection module is used for beating the local oscillation optical signal and the signal light to obtain a frequency-shifted microwave signal with the frequency of |f 0-f1-f2 |, wherein f 0 is the frequency of the continuous single-frequency optical carrier wave, f 1 is the frequency of the microwave signal to be frequency-shifted, and f 2 is the red-shifted resonance component of the slave laser.
For the convenience of public understanding, the following detailed description of the technical solution of the present invention will be given with reference to a specific embodiment in conjunction with the accompanying drawings:
the microwave frequency shift device in this embodiment 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, as shown in fig. 1.
The working process and principle of the device are as follows:
1) As shown in fig. 1, the continuous single-frequency optical carrier output by the laser is divided into three paths by the beam splitter, and the frequency of each path of continuous single-frequency optical carrier is f 0;
2) Taking a single-tone signal as an example (actually can be a linear frequency modulation signal or a phase coding 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 a microwave signal is f 1, and a modulated carrier suppression single-sideband signal obtained after passing through a modulation module is signal light, and the frequency is f 0-f1;
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 an optical coupler after passing through a phase shifter and an attenuator 2, two paths of signals are coupled into one path, the output signal of the coupler is an optical local oscillator signal obtained after spectrum frequency shift of a laser, and the frequency of the optical local oscillator signal is f 2;
5) The local oscillation light and the signal light enter two input ends of the photoelectric detector, beat frequency is completed in the photoelectric detector, and finally the output signal frequency is |f 0-f1-f2 |, so that frequency shift of the microwave signal is realized.
The modulation module in this embodiment implements carrier rejection single sideband modulation through a 90 degree bridge and a dual parallel mach-zehnder modulator, or may be implemented through other existing or future technologies such as a modulator optical filter, and fig. 2 shows a block diagram of the dual parallel mach-zehnder modulator, which is composed of two sub MZMs, MZM1, MZM2, and a main MZM, MZM3, where the two sub MZMs are embedded in an upper arm and a lower arm of the main MZM, respectively. In addition, the main modulator MZM3 only has a direct current bias voltage input port, and the direct current bias voltage of the MZM3 is controlled, so that the phase of an optical signal output by the MZM2 can be adjusted. The microwave signal is input to the radio frequency port of the double parallel Mach-Zehnder modulator after passing through the 90-degree bridge, and the bias voltages of three MZMs are adjusted to enable:
at this time, 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 adjustment method of the local oscillation light with reference to fig. 1 and 3:
As shown in fig. 1, one path of continuous single-frequency optical carrier outputted by the optical beam splitter is injected into the slave laser through a circulator after passing through the attenuator 1 and a polarization controller, an output optical signal of the slave laser is outputted after passing through the circulator, and the polarization controller in the system is used for matching an incident optical signal and obtaining the maximum injection power from the polarization direction of the slave laser. As shown in fig. 3, the frequency of the optical wave output from the laser is f s, the power is P s, the frequency of the injected light is f 0, the power is P 0, the injection intensity ζ=p 0/Ps, the detuning frequency is f i＝f0-fs, the injected light is injected into the slave laser through the circulator, the phase of the slave laser is locked, the intra-cavity oscillation is locked at the frequency f 0-f2, and under the light injection condition, the intra-cavity gain required from the laser is reduced, the refractive index of the intra-cavity gain medium is increased, resulting in an increase in the equivalent cavity length of the slave laser, and thus the cavity resonance frequency is red shifted from f s to f 2. By adjusting the injected light intensity and the amount of optical frequency mismatch, a variety of nonlinear dynamics from the laser can be excited, including steady-state locking, single-period oscillation, double-period oscillation, and chaotic oscillation. Wherein the single period oscillation occupies most of the state space, so that the single Zhou Zhendang frequency of the light injection semiconductor laser can be tuned over a wide range. In four dynamic states of light injection locking, the invention utilizes a single-period oscillation state to realize frequency shift of the light signal of the laser. In a single period oscillation state, laser oscillation excited by light injection and red shift cavity resonance caused by light injection have dynamic competition in the slave laser, and the dynamic characteristics of the semiconductor laser are changed. At the proper injection strength and detuning frequency, the split-off optical double sideband signal is generated due to the split-off of hopped, the sideband spacing f m＝f0-f2, which is called the single period oscillation frequency. Under the condition that the detuning frequency is certain, as the light injection intensity increases, the red shift resonant component light frequency gradually decreases and moves towards the direction deviating 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 wave output by the beam splitter is coupled with injection locking optical signals output by the laser in the optical coupler through the phase shifter and the attenuator 2, the two coupled optical signals are equal in size and opposite in phase by adjusting parameters of the phase shifter and the attenuator 2, so that spectrum cancellation is realized, only red-shifted resonant components are generated in the signals output by the coupler, local oscillation signals are obtained, the red-shifted frequency of the spectrum of the laser can be changed by adjusting the injection intensity of the light, and local oscillation lights with different frequencies are obtained.
Finally, the local oscillation light and the signal light are subjected to beat frequency in the photoelectric detector, and finally the frequency-shifted microwave signal with the frequency of |f 0-f1-f2 | is obtained. The frequency shift of the microwave signal can be adjusted by the attenuator 1.
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| CN102215066A (en) * | 2011-06-09 | 2011-10-12 | 中国科学院半导体研究所 | Device for generating photo-induced microwave carrier signal through single sideband modulation |
| CN110492337A (en) * | 2019-08-22 | 2019-11-22 | 天津大学 | A kind of production method of the wide-band microwave frequency comb based on optical-electronic oscillator |
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| TWI628925B (en) * | 2017-03-23 | 2018-07-01 | 國立成功大學 | Photonic microwave time delay apparatus and method thereof |
| CN107846254B (en) * | 2017-10-12 | 2020-04-17 | 北京工业大学 | Photonic method and system for realizing microwave down-conversion and phase shift by utilizing integrated device |
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| CN108809437B (en) * | 2018-07-23 | 2021-12-10 | 电子科技大学 | Microwave photon down-conversion device and method |
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| CN111541150B (en) * | 2020-04-28 | 2021-03-30 | 东南大学 | Device and method for realizing wavelength dynamic locking of semiconductor laser |
| CN113900315B (en) * | 2021-08-20 | 2024-06-18 | 清华大学 | Low-spurious high-order frequency doubling system and method based on optical sideband injection locking |
| CN115064926B (en) * | 2022-05-17 | 2025-09-12 | 中国人民解放军空军预警学院 | Dual-cavity self-injection integrated photogenerated microwave source system based on microcavity structure |
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| CN102215066A (en) * | 2011-06-09 | 2011-10-12 | 中国科学院半导体研究所 | Device for generating photo-induced microwave carrier signal through single sideband modulation |
| CN110492337A (en) * | 2019-08-22 | 2019-11-22 | 天津大学 | A kind of production method of the wide-band microwave frequency comb based on optical-electronic oscillator |
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