Microwave signal generation method and device based on dual-light injection semiconductor laser

Abstract

The invention discloses a microwave signal generation method based on a dual-light injection semiconductor laser. The method comprises the following steps: step 1, carrying out single-sideband modulation on a continuous optical carrier output by a main laser to obtain a single-sideband modulated optical signal; step 2, performing amplitude modulation on the single side band modulation optical signal to obtain an amplitude modulation single side band optical signal; 3, injecting the amplitude modulation single side band optical signal into a semiconductor slave laser, and enabling the semiconductor slave laser to enter a single-period oscillation state; step 4, filtering an optical signal output by the semiconductor from the laser, and only retaining a red shift component, a continuous optical carrier component and a first-order sideband component in the optical signal; and step 5, converting the filtered output optical signal of the semiconductor from the laser into an electric signal and outputting the electric signal. The invention further discloses a microwave signal generation device based on the double-light-injection semiconductor laser. According to the invention, low-frequency and high-quality microwave signals can be generated.

Description

Technical Field

[0001] The invention relates to a method for optically generating microwaves, in particular to a method for generating microwave signals based on a double-light injection semiconductor laser, and belongs to the technical field of microwave photons. Background Art

[0002] The signal source plays a vital role in signal generation. It is not only the basis of signal generation, but also directly affects the quality, stability and scope of application of the signal. Depending on the application scenario, the design and implementation of the signal source are also different. For example, in a wireless communication system, the signal source can generate a sine wave of a specific frequency with good stability and low phase noise. In more complex systems, such as photon-assisted microwave signal generation schemes, electrical components work together with optical components to generate high-quality signals.

[0003] Microwave photonics technology has significant advantages over traditional electrical methods in signal generation. First, microwave photonics technology can provide wider bandwidth and higher frequency range, and has low loss, high stability and anti-electromagnetic interference capabilities, which makes its application in complex environments more reliable. In addition, microwave photonics technology can also realize signal processing in the optical domain, thereby reducing the complexity and power consumption of electronic devices. These advantages have jointly promoted the widespread application and development of microwave photonics technology in modern communications, radar, sensing and other fields.

[0004] Optical heterodyne technology and optical injection semiconductor technology are two key technologies in the field of microwave photon signal generation, and they play an important role in signal generation. The basic principle of optical heterodyne technology is to perform photoelectric detection on two optical signals of different wavelengths to generate a microwave signal corresponding to their frequency difference. This technology can realize the generation of signals in different frequency bands, but due to the phase incoherence between the two optical signals of different wavelengths, the generated signal will have very high phase noise and poor quality. The principle of optical injection semiconductor laser technology is that when the optical signal is injected into the semiconductor laser, the nonlinear dynamic effect inside the semiconductor laser can be stimulated by adjusting the intensity and detuning frequency of the injected light, thereby generating a microwave signal with a specific frequency. Limited by the characteristics of semiconductor lasers, optical injection technology can generate signals of 10 GHz and above, or even hundreds of gigahertz, but it is difficult to generate signals below the relaxation oscillation frequency of semiconductor lasers. Even at very small injection intensity and detuning frequency, it is still difficult to generate signals in the low frequency band (usually below 10 GHz). Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a microwave signal generation method based on dual light injection semiconductor lasers, which can break through the limitation that traditional light injection semiconductor technology cannot generate low-frequency broadband signals, and the quality of the generated microwave signal is better than that of traditional optical heterodyne technology.

[0006] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0007] A method for generating a microwave signal based on a dual-light injection semiconductor laser comprises the following steps:

[0008] Step 1, performing single sideband modulation on the continuous optical carrier output by the main laser to obtain a single sideband modulated optical signal;

[0009] Step 2: performing amplitude modulation on the single sideband modulated optical signal to obtain an amplitude modulated single sideband optical signal;

[0010] Step 3, injecting the amplitude modulated single-sideband optical signal into the semiconductor slave laser, and causing the semiconductor slave laser to enter a single-cycle oscillation state;

[0011] Step 4, filtering the output optical signal of the semiconductor slave laser, and retaining only the red shift component, the continuous optical carrier component and the first-order sideband component;

[0012] Step 5: Convert the output optical signal of the filtered semiconductor laser into an electrical signal output.

[0013] Preferably, in step 5, one path of the output electrical signal is separated as a feedback control signal of the amplitude modulation.

[0014] Further preferably, the period of the amplitude control signal of the amplitude modulation is equal to the delay of the feedback control signal.

[0015] Preferably, the amplitude modulation is performed using a dual-drive Mach-Zehnder modulator.

[0016] Based on the same inventive concept, the following technical solutions can also be obtained:

[0017] A microwave signal generating device based on a double light injection semiconductor laser, comprising:

[0018] The radio frequency modulation module is used to perform single-sideband modulation on the continuous optical carrier output by the main laser to obtain a single-sideband modulated optical signal;

[0019] An injection intensity control module, used for performing amplitude modulation on the single sideband modulated optical signal to obtain an amplitude modulated single sideband optical signal;

[0020] An optical injection module is used to inject the amplitude modulated single-sideband optical signal into the semiconductor slave laser, and make the semiconductor slave laser enter a single-cycle oscillation state; and filter the output optical signal of the semiconductor slave laser to retain only the red-shift component, the continuous optical carrier component and the first-order sideband component therein;

[0021] The microwave signal output module is used to convert the output optical signal of the filtered semiconductor laser into an electrical signal output.

[0022] Preferably, the microwave signal output module comprises a photoelectric feedback loop for splitting the output electrical signal into one path as a feedback control signal for the amplitude modulation.

[0023] Further preferably, the period of the amplitude control signal of the amplitude modulation is equal to the delay of the photoelectric feedback loop.

[0024] Preferably, the amplitude modulation is performed using a dual-drive Mach-Zehnder modulator.

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0026] The present invention utilizes a single-sideband modulated optical signal as an injection signal from a laser and combines it with amplitude modulation to simultaneously generate low-frequency band and high-quality signals to meet diverse application requirements, which is unachievable with existing optical injection technology and optical heterodyne technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a principle block diagram of the microwave signal generating device of the present invention;

[0028] Figure 2 It is a structural schematic diagram of a specific embodiment of the microwave signal generating device of the present invention;

[0029] Figure 3 A control signal diagram generated by a signal generator in an injection intensity control module;

[0030] Figure 4 A spectrum diagram of the optical signal output by the optical injection module;

[0031] Figure 5 This is a time-frequency diagram of a 4-8 GHz linear frequency modulation signal generated by the microwave signal generating device of the present invention;

[0032] Figure 6 is the signal-to-noise ratio of the microwave signal generated by the microwave signal generating device of the present invention; wherein (a), (b), and (c) are the signal-to-noise ratios at three frequency points of 5 GHz, 6 GHz, and 7 GHz, respectively;

[0033] Figure 7It is the signal-to-noise ratio of the microwave signal generated by the optical heterodyne method under the same conditions; (a), (b), and (c) are the signal-to-noise ratios at three frequency points of 5 GHz, 6 GHz, and 7 GHz, respectively. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is described in detail below with reference to the accompanying drawings:

[0035] The basic structural principle of the microwave signal generating device of the present invention is as follows Figure 1 As shown, it includes a radio frequency modulation module, an injection intensity control module, an optical injection module, and a microwave signal output module; Figure 1 As shown, the frequency of the RF modulation module output to the main laser is f m1 The continuous optical carrier is modulated by single sideband (taking -1 order sideband as an example), and the optical carrier f is obtained. m1 and the first-order sideband f m2 A single sideband modulated optical signal, such as Figure 1 As shown in a; the injection intensity control module performs amplitude modulation on the single sideband modulated optical signal to obtain an amplitude modulated single sideband optical signal, wherein the amplitude control signal required for amplitude modulation is determined according to the microwave signal to be generated; the optical injection module injects the amplitude modulated single sideband optical signal into the output optical frequency f s The semiconductor slave laser is used to adjust the injection intensity (the ratio of the master laser to the slave laser power) and the detuning frequency (f i =f m1 -f s ) These two parameters excite the nonlinear dynamic state of the slave laser, making the slave laser in a single-cycle oscillation state. At this time, the equivalent cavity length of the laser will increase, causing the cavity resonance wavelength of the semiconductor slave laser to increase from f s Redshift to f s ′. Among them, due to f m2 The optical power is small and its influence on the dynamic state can be ignored. m1 Dominant, f m2 It mainly acts as a reference light to achieve down-conversion, and can generate signals below 10GHz after frequency beating. Since amplitude modulation will eventually generate a center frequency of f s ′, a red-shifted component with a bandwidth of B (related to the amplitude control signal), and then the output optical signal of the semiconductor slave laser is filtered to retain only the red-shifted component f s ', continuous optical carrier component f m1 and the first-order sideband component f m2 ,like Figure 1 As shown in b in the figure, the microwave signal output module converts the output optical signal of the filtered semiconductor from the laser into an electrical signal output through a photodetector.

[0036] On this basis, in order to further improve the quality of microwave signals, a photoelectric feedback loop can be set in the microwave signal output module to separate the output electrical signal as the feedback control signal of the amplitude modulation; adjust the period τ of the amplitude control signal mod To match the delay τ of the optoelectronic feedback loop cav , when the condition τ mod =τ cav When it is met, an approximate steady-state working mode will be formed in the system.

[0037] Figure 2 The basic structure of a specific embodiment of the microwave signal generating device of the present invention is shown. The RF modulation module in this embodiment is implemented by using an intensity modulator combined with an optical filter 1. The intensity modulator modulates the microwave signal generated by the microwave source onto the continuous optical carrier output by the main laser to generate a double-sideband modulated signal. Then, the optical filter removes one sideband to obtain a signal containing the optical carrier f. m1 and the one-sided first-order sideband f m2 The injection intensity control module in this embodiment adopts a dual-drive Mach-Zehnder modulator, and the amplitude control signal generated by the signal generator is loaded on the single-sideband modulated optical signal through the dual-drive Mach-Zehnder modulator, so as to realize injection intensity control by amplitude modulation of the single-sideband modulated optical signal; the amplitude modulated single-sideband optical signal output by the injection intensity control module first passes through a polarization controller, and then is injected into the slave laser through an optical circulator, and the polarization state of the optical signal output by the intensity modulator is adjusted by the polarization controller to match the slave laser, so as to realize maximum injection efficiency, and the injection intensity and the detuning frequency (f i =f m1 -f s ) these two parameters stimulate the nonlinear dynamic state of the slave laser, making the slave laser in a single-cycle oscillation state. The light signal output from the slave laser is filtered by optical filter 2, and only the redshift component f is retained. s ', continuous optical carrier component f m1 and the first-order sideband component f m2 , and then input into the microwave signal output module; the microwave signal output module in this embodiment comprises an optoelectronic feedback loop, which comprises an optical fiber, a photodetector, an electric amplifier, an electric power divider, and an electric attenuator cascaded in sequence. The filtered optical signal output by the optical injection module is converted into an electric signal by the photodetector and then divided into two paths by the electric power divider. One path is attenuated by the electric attenuator and then sent to the RF end of the dual-drive Mach-Zehnder modulator as an amplitude control feedback signal, and the other path is output as a microwave signal. The delay τ of the optoelectronic feedback loop is cav Equal to the period τ of the amplitude control signal mod .

[0038] In order to verify the effectiveness of the technical solution of the present invention, we conducted an experiment and built a system device taking the generation of linear frequency modulation signals as an example. The RF modulation module of the device includes a main laser (ID Photonics CoBriteDX4), whose output wavelength and power are set to 1548nm and 16dBm respectively, and works in conjunction with a Mach-Zehnder modulator (Lucent 2623NA) and a 6.1GHz microwave source (AMA1008). The modulated signal is filtered out of the optical carrier and the -1st order sideband through an optical filter 1 (Yenista XTM-50). The injection intensity control module consists of a signal generator (RIGOL DG4062, 500Msa / s) and a dual-drive Mach-Zehnder modulator (FTM7937EZ), which generates a sawtooth wave control signal with a time period of 5.12μs and an amplitude of 2.7V. The signal is corrected to match the nonlinear amplitude transfer curve of the dual-drive Mach-Zehnder modulator, such as Figure 3 As shown. The optical injection module consists of a polarization controller, a slave laser (PL-DFB-1550-C-A81-PA-14-BF), an optical circulator and an optical filter 2 (Yenista XTM-50). The slave laser is a distributed feedback semiconductor laser, with a bias current set to 26.4mA, an output power of 2.13dBm, and a free-running wavelength of 1548.06nm. After the optical signal is filtered by optical filter 2, the redshift component, continuous optical carrier component and first-order sideband component are obtained. The spectrum is shown in Figure 4 Finally, the filtered optical signal passes through the microwave signal output module, is converted into an electrical signal by 1012m optical fiber transmission and a photodetector (Discovery DSC40S), is amplified by an electrical amplifier (AT-LNA-0226-38040), and is divided into two paths by a power divider. One path is directly output, and the other is sent to the RF port of the dual-drive Mach-Zehnder modulator through an electrical attenuator to form an optoelectronic feedback loop.

[0039] Finally, the signal is output through the microwave signal output module and collected by the real-time oscilloscope and then short-time Fourier transformed to obtain a linear frequency modulation signal with a bandwidth of 4 GHz and a frequency range of 4-8 GHz, such as Figure 5 To verify the signal quality, a spectrum analyzer was used to collect the signal spectrum. The signal-to-noise ratios at the three frequency points of 5 GHz, 6 GHz, and 7 GHz were 35 dB, 35 dB, and 32 dB, respectively. Figure 6 Compared with the optical heterodyne method, under the same conditions, the signal-to-noise ratios of the three frequencies of 5 GHz, 6 GHz, and 7 GHz are 16 dB, 21 dB, and 19 dB, respectively. Figure 7 Compared with the optical heterodyne technology, the signal-to-noise ratio of this method is nearly doubled, indicating that the present invention can effectively generate low-frequency and high-quality signals with superior performance.

Claims

1. A method for generating microwave signals based on a double light injection semiconductor laser, characterized in that: The following steps are involved: Step 1, performing single sideband modulation on the continuous optical carrier output by the main laser to obtain a single sideband modulated optical signal; Step 2: performing amplitude modulation on the single sideband modulated optical signal to obtain an amplitude modulated single sideband optical signal; Step 3, injecting the amplitude modulated single-sideband optical signal into the semiconductor slave laser, and causing the semiconductor slave laser to enter a single-cycle oscillation state; Step 4, filtering the output optical signal of the semiconductor slave laser, and retaining only the red shift component, the continuous optical carrier component and the first-order sideband component; Step 5: Convert the output optical signal of the filtered semiconductor laser into an electrical signal output.

2. The method for generating microwave signals based on a double light injection semiconductor laser according to claim 1, characterized in that: In step 5, one path of the output electrical signal is separated as a feedback control signal of the amplitude modulation.

3. The method for generating microwave signals based on a double light injection semiconductor laser according to claim 2, characterized in that: The period of the amplitude control signal of the amplitude modulation is equal to the delay of the feedback control signal.

4. The method for generating microwave signals based on a double light injection semiconductor laser according to claim 1, characterized in that: The amplitude modulation is performed using a dual-drive Mach-Zehnder modulator.

5. A microwave signal generating device based on a double light injection semiconductor laser, characterized in that: include: The radio frequency modulation module is used to perform single-sideband modulation on the continuous optical carrier output by the main laser to obtain a single-sideband modulated optical signal; An injection intensity control module, used for performing amplitude modulation on the single sideband modulated optical signal to obtain an amplitude modulated single sideband optical signal; An optical injection module is used to inject the amplitude modulated single-sideband optical signal into the semiconductor slave laser, and make the semiconductor slave laser enter a single-cycle oscillation state; and filter the output optical signal of the semiconductor slave laser to retain only the red-shift component, the continuous optical carrier component and the first-order sideband component therein; The microwave signal output module is used to convert the output optical signal of the filtered semiconductor laser into an electrical signal output.

6. The microwave signal generating device based on double light injection semiconductor laser as claimed in claim 5, characterized in that: The microwave signal output module comprises a photoelectric feedback loop, which is used to separate one path of the output electrical signal as the feedback control signal of the amplitude modulation.

7. The microwave signal generating device based on double light injection semiconductor laser as claimed in claim 6, characterized in that: The amplitude control signal period of the amplitude modulation is equal to the delay of the photoelectric feedback loop.

8. The microwave signal generating device based on double light injection semiconductor laser as claimed in claim 5, characterized in that: The amplitude modulation is performed using a dual-drive Mach-Zehnder modulator.

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