A frequency doubling triangular waveform generation system and method

Abstract

The present invention provides a frequency-doubled triangular waveform generation system and method, which relates to the field of optical communication technologies. The frequency-doubled triangular waveform generation system includes: a first continuous-wave laser, a second continuous-wave laser, a first intensity modulator, a wavelength division multiplexer, a second intensity modulator, a radio frequency signal generator, an electrical attenuator, and a photodetector; the first continuous-wave laser is connected to the wavelength division multiplexer; the output end of the second continuous-wave laser is connected to the optical input interface of the first intensity modulator, and the output end of the first intensity modulator is connected to the wavelength division multiplexer; the output end of the wavelength division multiplexer is connected to the optical input interface of the second intensity modulator, and the output end of the second intensity modulator is connected to the input end of the photodetector; the output end of the radio frequency signal generator is connected to the radio frequency input interface of the first intensity modulator, and the output end of the radio frequency signal generator is connected to the radio frequency input interface of the second intensity modulator through the electrical attenuator. The present invention has low cost, simple structure and easy operation.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technologies, and particularly to a frequency-doubled triangular waveform generation system and method. Background Art

[0002] High-speed microwave signals are widely used in various fields such as modern radars or antennas, sensor networks, radio frequency communication systems, and electronic device test and measurement. Therefore, the generation of high-frequency microwave signals has always been a research hotspot. The development of human society has put forward higher requirements for the frequency of microwave signals, such as the millimeter-wave communication technology used in the fifth-generation mobile communication technology. Compared with the traditional electrical method for generating microwave signals, the optical-assisted method for generating microwave signals has the advantages of large bandwidth, anti-electromagnetic interference, and high speed.

[0003] In related technologies, a method of spectral shaping and frequency-time mapping of a broad-spectrum light source has been proposed to generate a triangular microwave signal with adjustable repetition frequency. However, the cost of using a broad-spectrum light source is too high, different fiber lengths are required for synthesizing triangular waveforms with different repetition frequencies, and the pulse width of the generated signal is relatively narrow.

[0004] Researchers analyzed the frequency components of the triangular microwave signal and realized that the triangular wave is composed of a series of odd-order sine signals, and the energy is concentrated in the first and third harmonics. As long as signals satisfying the amplitude and phase of the first and third harmonics of the triangular wave are generated, an approximate triangular microwave signal can be generated. In related technologies, a method of using a continuous light source as a carrier for external modulation to generate a frequency-doubled triangular signal has been proposed. This method is based on an integrated modulator, a dual-parallel Mach-Zehnder modulator (DP-MZM), to externally modulate the continuous light. One of the two sub-modulators operates at the minimum bias point, and the main modulator operates at the quadrature bias point. However, this method requires using an electrical tripler to triple the frequency of one of the radio frequency signals input to the DP-MZM to meet the system requirements, which limits the frequency of the signal generated by the system to the bandwidth of the electrical tripler.

[0005] Both broad-spectrum light sources and continuous light sources are widely used in the generation of microwave signals. However, the problems are as follows: The broad-spectrum light source is generated by a mode-locked laser, and the repetition frequency of the optical pulse is small, and the time-domain repetition period of the pulse is long, which is not conducive to the generation of high-repetition-frequency microwave signals. Most of the external modulation systems using continuous light sources as carriers cannot generate frequency-doubled signals. Therefore, in the prior art, it is difficult to generate frequency-doubled triangular waveform signals. Summary of the Invention

[0006] The object of the technical solution of the present invention is to provide a frequency-doubled triangular waveform generation system and method to solve the problem that it is difficult to generate frequency-doubled triangular waveform signals in the prior art.

[0007] The embodiments of the present invention provide the following technical solutions:

[0008] The embodiments of the present invention provide a frequency-doubled triangular waveform generation system, including:

[0009] A first continuous-wave laser, a second continuous-wave laser, a first intensity modulator, a wavelength division multiplexer, a second intensity modulator, a radio frequency signal generator, an electrical attenuator, and a photodetector;

[0010] Wherein, the output end of the first continuous-wave laser is connected to the first input end of the wavelength division multiplexer; the output end of the second continuous-wave laser is connected to the optical input interface of the first intensity modulator, and the output end of the first intensity modulator is connected to the second input end of the wavelength division multiplexer; the output end of the wavelength division multiplexer is connected to the optical input interface of the second intensity modulator, and the output end of the second intensity modulator is connected to the input end of the photodetector; the output end of the radio frequency signal generator is connected to the radio frequency input interface of the first intensity modulator, and the output end of the radio frequency signal generator is connected to the radio frequency input interface of the second intensity modulator through the electrical attenuator.

[0011] Optionally, the output end of the first continuous-wave laser is connected to the first input end of the wavelength division multiplexer through an optical fiber;

[0012] The output end of the second continuous-wave laser is connected to the optical input interface of the first intensity modulator and the output end of the first intensity modulator is connected to the second input end of the wavelength division multiplexer through optical fibers respectively;

[0013] The output end of the wavelength division multiplexer is connected to the optical input interface of the second intensity modulator and the output end of the second intensity modulator is connected to the input end of the photodetector through optical fibers respectively.

[0014] Optionally, the output end of the radio frequency signal generator is connected to the radio frequency input interface of the first intensity modulator through a radio frequency line;

[0015] The output end of the radio frequency signal generator is connected to the electrical attenuator through a radio frequency line, and the electrical attenuator is connected to the radio frequency input interface of the second intensity modulator through a radio frequency line.

[0016] The embodiments of the present invention further provide a frequency-doubled triangular waveform generation method, which is applied to the frequency-doubled triangular waveform generation system described in any one of the above, and the method includes:

[0017] The first continuous-wave laser sends a first optical signal to the wavelength division multiplexer, the second continuous-wave laser sends a second optical signal to the first intensity modulator, and the radio frequency signal generator sends a first radio frequency sine signal to the first intensity modulator;

[0018] The first intensity modulator modulates the first radio frequency sine signal onto the second optical signal to obtain a third optical signal and positive and negative second-order sidebands deviating from the optical carrier, and sends the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier to the wavelength division multiplexer;

[0019] The wavelength division multiplexer sends the first optical signal, the third optical signal, and the positive and negative second-order sidebands deviating from the optical carrier to the second intensity modulator, and the radio frequency signal generator sends a second radio frequency sine signal to the second intensity modulator through the electrical attenuator;

[0020] The second intensity modulator modulates the second radio frequency sine signal onto the first optical signal, the third optical signal, and the positive and negative second-order sidebands deviating from the optical carrier to obtain positive and negative first-order sidebands deviating from the optical carrier and positive and negative third-order sidebands deviating from the optical carrier, and sends the positive and negative first-order sidebands deviating from the optical carrier and the positive and negative third-order sidebands deviating from the optical carrier to the photodetector;

[0021] The photodetector generates a frequency-doubled triangular wave signal according to the positive and negative first-order sidebands deviating from the optical carrier and the positive and negative third-order sidebands deviating from the optical carrier.

[0022] Optionally, the wavelengths of the first optical signal and the second optical signal are different.

[0023] Optionally, the wavelength interval between the first optical signal and the second optical signal is greater than or equal to 8 nm.

[0024] Optionally, the optical powers of the first optical signal and the second optical signal are the same.

[0025] Optionally, the modulation depths of the first radio frequency sine signal and the second radio frequency sine signal are different;

[0026] The first radio frequency sine signal and the second radio frequency sine signal have the same frequency;

[0027] The first radio frequency sine signal and the second radio frequency sine signal have the same phase.

[0028] Optionally, the first intensity modulator modulates the first radio frequency sine signal onto the second optical signal to obtain positive and negative second-order sidebands deviating from the optical carrier, including:

[0029] The first intensity modulator operates at the highest bias point, modulates the first radio frequency sine signal onto the second optical signal, suppresses odd-order optical sidebands, and obtains the positive and negative second-order sidebands deviating from the optical carrier.

[0030] Optionally, the second intensity modulator modulates the second RF sine signal onto the positive and negative second-order sidebands of the first optical signal, the third optical signal, and the offset optical carrier, to obtain the positive and negative first-order sidebands of the offset optical carrier and the positive and negative third-order sidebands of the offset optical carrier, including:

[0031] The second intensity modulator operates at the lowest bias point, modulates the second RF sine signal onto the first optical signal, and suppresses the first optical signal, to obtain the positive and negative first-order sidebands of the offset optical carrier;

[0032] The second intensity modulator modulates the second RF sine signal onto the third optical signal and the positive and negative second-order sidebands of the offset optical carrier, and suppresses the third optical signal and the positive and negative second-order sidebands of the offset optical carrier, to obtain the positive and negative third-order sidebands of the offset optical carrier.

[0033] Optionally, the photodetector generates a frequency-doubled triangular wave signal according to the positive and negative first-order sidebands of the offset optical carrier and the positive and negative third-order sidebands of the offset optical carrier, including:

[0034] The photodetector generates a two-fold cosine signal, a six-fold cosine signal, and a clutter signal according to the positive and negative first-order sidebands of the offset optical carrier and the positive and negative third-order sidebands of the offset optical carrier;

[0035] The photodetector generates a frequency-doubled triangular wave signal according to the two-fold cosine signal, the six-fold cosine signal, and the clutter signal.

[0036] Advantages of the present invention:

[0037] The frequency-doubled triangular waveform generation system provided by the solution of the present invention includes using two continuous optical lasers (the first continuous optical laser and the second continuous optical laser), a first intensity modulator, and a radio frequency signal generator to generate two optical carriers with different wavelengths as two channels, and using wavelength multiplexing technology through a wavelength division multiplexer, a radio frequency signal generator, a second intensity modulator, and a photodetector to synthesize a triangular waveform with a repetition frequency twice that of the radio frequency signal. Compared with the existing methods of using a mode-locked laser to generate a broadband light source and a continuous light source to generate a microwave signal, the present invention uses a continuous laser light source instead of an expensive mode-locked laser device, with low cost, simple structure, easy operation, and is easier to generate a frequency-doubled signal compared to an external modulation system using a continuous light source as a carrier. Description of the Drawings

[0038] Figure 1 It is a schematic structural diagram of the frequency-doubled triangular waveform generation system provided by an embodiment of the present invention;

[0039] Figure 2 It is a flowchart of the frequency-doubled triangular waveform generation method provided by an embodiment of the present invention;

[0040] Figure 3 This is the time-domain waveform diagram of the frequency-doubled triangular waveform provided by the embodiment of the present invention;

[0041] Figure 4 This is the power spectrum diagram of the frequency-doubled triangular waveform provided by the embodiment of the present invention.

[0042] Explanation of reference numerals:

[0043] 1 - First continuous-wave laser; 2 - Second continuous-wave laser; 3 - First intensity modulator; 4 - Wavelength division multiplexer; 5 - Second intensity modulator; 6 - RF signal generator; 7 - Electrical attenuator; 8 - Photoelectric detector. Detailed implementation manners

[0044] To make the technical problems, technical solutions, and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0045] To solve the problem that it is difficult to generate a frequency-doubled triangular waveform signal in the prior art, the embodiment of the present invention provides a frequency-doubled triangular waveform generation system and method.

[0046] As Figure 1 shown, the embodiment of the present invention provides a frequency-doubled triangular waveform generation system, including:

[0047] First continuous-wave laser 1, second continuous-wave laser 2, first intensity modulator 3, wavelength division multiplexer 4, second intensity modulator 5, RF signal generator 6, electrical attenuator 7, photoelectric detector 8;

[0048] Wherein, the output end of the first continuous-wave laser 1 is connected to the first input end of the wavelength division multiplexer 4; the output end of the second continuous-wave laser 2 is connected to the optical input interface of the first intensity modulator 3, and the output end of the first intensity modulator 3 is connected to the second input end of the wavelength division multiplexer 4; the output end of the wavelength division multiplexer 4 is connected to the optical input interface of the second intensity modulator 5, and the output end of the second intensity modulator 5 is connected to the input end of the photoelectric detector 8; the output end of the RF signal generator 6 is connected to the RF input interface of the first intensity modulator 3, and the output end of the RF signal generator 6 is connected to the RF input interface of the second intensity modulator 5 through the electrical attenuator 7.

[0049] Wherein, the wavelengths of the optical signals (optical carriers) output by the two continuous-wave lasers (i.e., the first continuous-wave laser 1 and the second continuous-wave laser 2) are different, and the wavelength interval between the optical signals of the two continuous-wave lasers is greater than or equal to 8 nm, and the optical powers are the same.

[0050] As Figure 1As described above, the continuous-wave lasers of two continuous-wave lasers (i.e., the first continuous-wave laser 1 and the second continuous-wave laser 2) are arranged in parallel.

[0051] Optionally, the output end of the first continuous-wave laser 1 is connected to the first input end of the wavelength division multiplexer 4 through an optical fiber; the output end of the second continuous-wave laser 2 is connected to the optical input interface of the first intensity modulator 3, and the output end of the first intensity modulator 3 and the second input end of the wavelength division multiplexer 4 are respectively connected through an optical fiber; the output end of the wavelength division multiplexer 4 is connected to the optical input interface of the second intensity modulator 5, and the output end of the second intensity modulator 5 and the input end of the photodetector 8 are respectively connected through an optical fiber. That is, as Figure 1 shown, there is an optical path connection between the first continuous-wave laser 1 and the wavelength division multiplexer 4, the second continuous-wave laser 2 and the first intensity modulator 3, the first intensity modulator 3 and the wavelength division multiplexer 4, the wavelength division multiplexer 4 and the second intensity modulator 5, and the second intensity modulator 5 and the photodetector 8.

[0052] Optionally, the output end of the radio frequency signal generator 6 is connected to the radio frequency input interface of the first intensity modulator 3 through a radio frequency line; the output end of the radio frequency signal generator 6 is connected to the electrical attenuator 7 through a radio frequency line, and the electrical attenuator 7 is connected to the radio frequency input interface of the second intensity modulator 5 through a radio frequency line. That is, as Figure 1 shown, there is a circuit connection between the radio frequency signal generator 6 and the first intensity modulator 3, the radio frequency signal generator 6 and the electrical attenuator 7, and the electrical attenuator 7 and the second intensity modulator 5.

[0053] As Figure 2 shown, an embodiment of the present invention further provides a method for generating a frequency-doubled triangular waveform, which is applied to the frequency-doubled triangular waveform generation system described in any one of the above, and the method includes:

[0054] Step 201: The first continuous-wave laser sends a first optical signal to the wavelength division multiplexer, the second continuous-wave laser sends a second optical signal to the first intensity modulator, and the radio frequency signal generator sends a first radio frequency sine signal to the first intensity modulator.

[0055] Among them, the first continuous-wave laser and the second continuous-wave laser are arranged in parallel. The wavelength of the first optical signal generated by the first continuous-wave laser is λ1, and the wavelength of the second optical signal generated by the second continuous-wave laser is λ2. According to the wavelength-frequency conversion formula ω = 2πc / λ, the optical carrier angular frequency of the wavelength λ1 is ω1, and the optical carrier angular frequency of the wavelength λ2 is ω2.

[0056] The first optical signal output by the first continuous-wave laser serves as the upper-branch carrier, and its time-domain expression is denoted as: E in_1= E1exp(jω1t), the second optical signal output by the second continuous optical laser is used as the carrier of the lower branch, and its time-domain expression is denoted as: E in_2 = E2 exp(jω2t).

[0057] The first RF sine signal (RF driving signal) input by the RF signal generator to the first intensity modulator is: x1(t) = V RF1 sin(ωt), where V RF1 represents the amplitude of the first RF sine signal.

[0058] Wherein, the wavelengths of the first optical signal and the second optical signal are different.

[0059] Wherein, the wavelength interval between the first optical signal and the second optical signal is greater than or equal to 8 nm, that is, the first continuous optical laser and the second continuous optical laser are used to generate continuous light with a wavelength interval greater than or equal to 8 nm as the optical carrier.

[0060] The optical powers of the first optical signal and the second optical signal are the same.

[0061] Step 202: The first intensity modulator modulates the first RF sine signal onto the second optical signal to obtain a third optical signal and positive and negative second-order sidebands deviating from the optical carrier, and sends the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier to the wavelength division multiplexer.

[0062] In this step, the second optical signal output by the second continuous optical laser enters the first intensity modulator and is modulated with the first RF sine signal.

[0063] The first optical signal output by the first continuous optical laser, the third optical signal output by the first intensity modulator, and the positive and negative second-order sidebands deviating from the optical carrier enter the wavelength division multiplexer.

[0064] Step 203: The wavelength division multiplexer sends the first optical signal, the third optical signal, and the positive and negative second-order sidebands deviating from the optical carrier to the second intensity modulator, and the RF signal generator sends a second RF sine signal to the second intensity modulator through the electrical attenuator.

[0065] In this step, the wavelength division multiplexer is used to multiplex the optical signals in two parallel optical paths into the same optical path.

[0066] The electrical attenuator is used to attenuate the power of the second RF sine signal input to the second intensity modulator.

[0067] Step 204: The second intensity modulator modulates the second RF sine signal onto the positive and negative second-order sidebands of the first optical signal, the third optical signal, and the offset optical carrier, to obtain the positive and negative first-order sidebands of the offset optical carrier and the positive and negative third-order sidebands of the offset optical carrier, and sends the positive and negative first-order sidebands of the offset optical carrier and the positive and negative third-order sidebands of the offset optical carrier to the photodetector.

[0068] In this step, the optical signal output by the wavelength division multiplexer enters the second intensity modulator and is modulated with the second RF sine signal, generating the positive and negative first-order sidebands of the offset optical carrier and the positive and negative third-order sidebands of the offset optical carrier.

[0069] Step 205: The photodetector generates a frequency-doubled triangular wave signal based on the positive and negative first-order sidebands of the offset optical carrier and the positive and negative third-order sidebands of the offset optical carrier.

[0070] In this step, the optical signal output by the second intensity modulator undergoes photoelectric conversion by the photodetector to obtain a frequency-doubled triangular wave signal. Specifically, the photodetector is used to convert the multiplexed optical signal into an electrical signal, and at the same time, as a low-pass filter, it filters out ultra-high-frequency electrical harmonics to obtain the expected frequency-doubled triangular wave signal.

[0071] Optionally, the modulation depths of the first RF sine signal and the second RF sine signal are different;

[0072] The first RF sine signal and the second RF sine signal have the same frequency;

[0073] The first RF sine signal and the second RF sine signal have the same phase.

[0074] In an alternative embodiment, step 202 includes:

[0075] The first intensity modulator operates at the highest bias point, modulates the first RF sine signal onto the second optical signal, suppresses the odd-order optical sidebands, and obtains the positive and negative second-order sidebands of the offset optical carrier, that is, the second optical signal output by the second continuous optical laser enters the first intensity modulator and is modulated with the sine signal, and the DC bias operates at the highest bias point, so that the odd-order optical sidebands are suppressed, generating the positive and negative second-order sidebands of the offset optical carrier.

[0076] Specifically, the optical signal output by the first intensity modulator can be expressed as:

[0077]

[0078] where m1 = πV RF1 / V π is the modulation coefficient of the first intensity modulator. is the phase introduced by the DC bias, V πis the half-wave voltage of the first intensity modulator, V1 is the DC bias voltage of the first intensity modulator, and V RF1 is the amplitude of the RF signal input to the first intensity modulator.

[0079] Since the DC bias of the first intensity modulator works at the highest point, the output optical signal is expressed as:

[0080]

[0081] In an optional embodiment, step 204 includes:

[0082] The second intensity modulator works at the lowest bias point, modulates the second RF sine signal onto the first optical signal, suppresses the first optical signal, and obtains the positive and negative first-order sidebands deviating from the optical carrier, that is, the optical signal output by the wavelength division multiplexer enters the second intensity modulator and is modulated with the second RF sine signal, the DC bias works at the lowest bias point, the optical carrier generated by the first continuous optical laser is suppressed, and the positive and negative first-order sidebands deviating from the optical carrier are generated. And the second intensity modulator modulates the second RF sine signal onto the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier, suppresses the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier, and obtains the positive and negative third-order sidebands deviating from the optical carrier, that is, the optical carrier output by the first intensity modulator and the positive and negative second-order sidebands are suppressed, and the positive and negative third-order sidebands deviating from the optical carrier are generated.

[0083] Specifically, the optical signals multiplexed by wavelength division multiplexing into the same optical path are denoted as:

[0084]

[0085] The optical signal multiplexed by the wavelength division multiplexer enters the second intensity modulator for modulation. The second RF sine signal input to the second intensity modulator by the RF signal generator through the electrical attenuator is: x2(t) = V RF2 sin(ωt), where V RF2 is the amplitude of the second RF sine signal, and the DC bias of the second intensity modulator works at the lowest point. The signal E out2 (t) (including the positive and negative first-order sidebands deviating from the optical carrier and the positive and negative third-order sidebands deviating from the optical carrier) is denoted as:

[0086]

[0087] where m2 = πV RF2 / V π is the modulation coefficient of the second intensity modulator, V RF2 is the amplitude of the RF signal input to the second intensity modulator, V π is the half-wave voltage of the second intensity modulator, EMUX is the signal output by the wavelength division multiplexer. According to the properties of Bessel functions:

[0088]

[0089] where m = πV RF / V π is the modulation index of the modulator, V π is the half-wave voltage of the second intensity modulator, J n (·) is the Bessel function of the first kind of order n, J 2n (·) is the Bessel function of even order, and φ is the phase shift introduced by the DC bias.

[0090] By controlling the amplitudes of the first RF sine signal input to the first intensity modulator and the second RF sine signal input to the second intensity modulator to satisfy J0(m1)-J2(m1)=0, the optical signal output by the second intensity modulator can be rewritten as:

[0091]

[0092] In an optional embodiment, step 205 includes:

[0093] The photodetector generates a double sine signal, a six-fold sine signal, and clutter signals according to the positive and negative first-order sidebands deviating from the optical carrier and the positive and negative third-order sidebands deviating from the optical carrier, that is, the optical signal output by the second intensity modulator undergoes photoelectric conversion by the photodetector to generate a double cosine signal, a six-fold cosine signal, and other clutter signals. Among them, the clutter signals include ultra-high frequency (terahertz level) electrical signals; the photodetector generates a frequency-doubled triangular wave signal according to the double sine signal, the six-fold sine signal, and the clutter signals. Specifically, after low-pass filtering with bandwidth matching of the photodetector (the bandwidth of the photodetector is limited), the ultra-high frequency electrical harmonics are filtered out, and the amplitude ratio of the harmonics of the double cosine signal and the six-fold cosine signal (RF signals) is 9:1, and the frequency-doubled triangular microwave signal can be successfully synthesized.

[0094] The optical signal output by the second intensity modulator is input to the photodetector. Because the bandwidth of the photodetector is limited, the photodetector can be equivalently regarded as a low-pass filter. As long as the two different-frequency optical carriers are spaced far enough apart (a 0.8 nm spectral width is equivalent to a 100 GHz bandwidth interval), the ultra-high frequency (terahertz level) electrical signals generated by the beating of the two wavelengths and sidebands will be filtered out. Therefore, the analog signal after photoelectric detection is expressed as:

[0095]

[0096] The Fourier series expansion of an ideal symmetric triangular wave is:

[0097]

[0098] wherein, n is an integer and C is a constant.

[0099] When only considering the first two harmonics of the ideal symmetric triangular waveform, the above formula needs to satisfy:

[0100]

[0101] Because the output powers of the first continuous light laser and the second continuous light laser are the same, it is necessary to satisfy Finally, the electrical signal output by the photodetector is the expected frequency-doubled triangular waveform signal.

[0102] Adopting this scheme, a triangular waveform with a frequency of 2ω can be obtained by inputting a radio frequency cosine signal with a frequency of ω. In this embodiment, the value of the radio frequency cosine ω is 5 GHz. The repetition frequency of the generated triangular microwave signal is 10 GHz, as shown in Figure 3 the time-domain waveform diagram of the frequency-doubled triangular waveform shown and Figure 4 the power spectrum diagram of the frequency-doubled triangular waveform shown. Of course, the value of the frequency of the radio frequency signal can be selected according to actual needs, and the bandwidth of the photodetector can also be selected as needed, but it must be ensured that the effective harmonics of the output electrical signal are within the bandwidth of the photodetector.

[0103] The present invention provides a wavelength-division multiplexing assisted frequency-doubled triangular waveform generation system and method. Using dual-wavelength multiplexing as a dual-channel method avoids the use of polarization modulators and polarization elements, increasing the stability of the system; without using an electrical phase shifter, it is a method of all-optical synthesis of triangular microwave signals, not limited by the bandwidth limitation of the electrical phase shifter, and has high tunability of the frequency of the generated waveform; without using an integrated modulator, simply using two wavelengths, two intensity modulators, a wavelength-division multiplexer, and a photodetector to synthesize a frequency-doubled triangular waveform, with low cost, simple structure, and easy implementation.

[0104] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A frequency doubling triangular waveform generation system, characterized in that Including: A first continuous-wave laser (1), a second continuous-wave laser (2), a first intensity modulator (3), a wavelength division multiplexer (4), a second intensity modulator (5), a radio frequency signal generator (6), an electrical attenuator (7), and a photodetector (8); Wherein, an output end of the first continuous-wave laser (1) is connected to a first input end of the wavelength division multiplexer (4); an output end of the second continuous-wave laser (2) is connected to an optical input interface of the first intensity modulator (3), and an output end of the first intensity modulator (3) is connected to a second input end of the wavelength division multiplexer (4); an output end of the wavelength division multiplexer (4) is connected to an optical input interface of the second intensity modulator (5), and an output end of the second intensity modulator (5) is connected to an input end of the photodetector (8); an output end of the radio frequency signal generator (6) is connected to a radio frequency input interface of the first intensity modulator (3), and the output end of the radio frequency signal generator (6) is connected to a radio frequency input interface of the second intensity modulator (5) through the electrical attenuator (7); Wherein, wavelengths of optical signals output by the first continuous-wave laser (1) and the second continuous-wave laser (2) are different; A wavelength interval between the optical signals output by the first continuous-wave laser (1) and the second continuous-wave laser (2) is greater than or equal to 8 nm; Optical powers of the optical signals output by the first continuous-wave laser (1) and the second continuous-wave laser (2) are the same.

2. The frequency doubling triangular waveform generation system according to claim 1, wherein The output end of the first continuous-wave laser (1) is connected to the first input end of the wavelength division multiplexer (4) through an optical fiber; The output end of the second continuous-wave laser (2) is connected to the optical input interface of the first intensity modulator (3), and the output end of the first intensity modulator (3) is connected to the second input end of the wavelength division multiplexer (4) through optical fibers respectively; The output end of the wavelength division multiplexer (4) is connected to the optical input interface of the second intensity modulator (5), and the output end of the second intensity modulator (5) is connected to the input end of the photodetector (8) through optical fibers respectively.

3. The frequency doubling triangular waveform generation system according to claim 1, wherein, The output end of the radio frequency signal generator (6) is connected to the radio frequency input interface of the first intensity modulator (3) through a radio frequency cable; The output end of the radio frequency signal generator (6) is connected to the electrical attenuator (7) through a radio frequency cable, and the electrical attenuator (7) is connected to the radio frequency input interface of the second intensity modulator (5) through a radio frequency cable.

4. A method for generating a frequency-doubled triangular waveform, characterized in that, Applied to the frequency doubling triangular waveform generating system according to any one of claims 1 to 3, the method includes: The first continuous-wave laser sends a first optical signal to the wavelength division multiplexer, the second continuous-wave laser sends a second optical signal to the first intensity modulator, and the radio frequency signal generator sends a first radio frequency sine signal to the first intensity modulator; The first intensity modulator modulates the first RF sine signal onto the second optical signal to obtain a third optical signal and positive and negative second-order sidebands deviating from the optical carrier, and sends the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier to the wavelength division multiplexer; The wavelength division multiplexer sends the first optical signal, the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier to the second intensity modulator, and the RF signal generator sends a second RF sine signal to the second intensity modulator through the electrical attenuator; The second intensity modulator modulates the second RF sine signal onto the first optical signal, the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier to obtain positive and negative first-order sidebands deviating from the optical carrier and positive and negative third-order sidebands deviating from the optical carrier, and sends the positive and negative first-order sidebands deviating from the optical carrier and the positive and negative third-order sidebands deviating from the optical carrier to the photodetector; The photodetector generates a frequency-doubled triangular wave signal according to the positive and negative first-order sidebands deviating from the optical carrier and the positive and negative third-order sidebands deviating from the optical carrier; Wherein, the wavelengths of the first optical signal and the second optical signal are different; The wavelength interval between the first optical signal and the second optical signal is greater than or equal to 8 nm; The optical powers of the first optical signal and the second optical signal are the same.

5. The method for generating a frequency-doubled triangular waveform according to claim 4, characterized in that, The modulation depths of the first RF sine signal and the second RF sine signal are different; The frequencies of the first RF sine signal and the second RF sine signal are the same; The phases of the first RF sine signal and the second RF sine signal are the same.

6. The method for generating a frequency-doubled triangular waveform according to claim 4, wherein The first intensity modulator modulates the first RF sine signal onto the second optical signal to obtain positive and negative second-order sidebands deviating from the optical carrier, including: The first intensity modulator operates at the highest bias point, modulates the first RF sine signal onto the second optical signal, suppresses odd-order optical sidebands, and obtains the positive and negative second-order sidebands deviating from the optical carrier.

7. The method for generating a frequency-doubled triangular waveform according to claim 4, wherein The second intensity modulator modulates the second RF sine signal onto the first optical signal, the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier to obtain positive and negative first-order sidebands deviating from the optical carrier and positive and negative third-order sidebands deviating from the optical carrier, including: The second intensity modulator operates at the lowest bias point, modulates the second RF sine signal onto the first optical signal, suppresses the first optical signal, and obtains the positive and negative first-order sidebands deviating from the optical carrier; The second intensity modulator modulates the second RF sine signal onto the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier, suppresses the third optical signal and the positive and negative second-order sidebands deviating from the optical carrier, and obtains the positive and negative third-order sidebands deviating from the optical carrier.

8. The method for generating a frequency-doubled triangular waveform according to claim 4, wherein The photodetector generates a frequency-doubled triangular wave signal according to the positive and negative first-order sidebands deviating from the optical carrier and the positive and negative third-order sidebands deviating from the optical carrier, including: The photodetector generates a double cosine signal, a six-fold cosine signal and a clutter signal according to the positive and negative first-order sidebands deviating from the optical carrier and the positive and negative third-order sidebands deviating from the optical carrier; The photodetector generates a frequency-doubled triangular wave signal based on the twice cosine signal, the six-times cosine signal, and the clutter signal.

Images