Large-bandwidth high-flatness optical frequency comb generation device based on microwave photonics

Abstract

The invention discloses a large-bandwidth high-flatness optical frequency comb generation device based on microwave photonics, and belongs to the technical field of microwave photonics. The device is composed of a continuous wave laser, a power optical splitter 1, a power optical splitter 2, a differential MZM1, a differential MZM2, a differential MZM3, a differential MZM4, a differential MZM5, a 90-degree phase shifter 1, a 90-degree phase shifter 2, an arbitrary waveform generator 1, an arbitrary waveform generator 2, an arbitrary waveform generator 3, a direct-current voltage stabilization source 1, a direct-current voltage stabilization source 2, a direct-current voltage stabilization source 3, a direct-current voltage stabilization source 4, a direct-current voltage stabilization source 5, a power combiner 1 and a power combiner 2. The device improves the bandwidth and flatness of the optical frequency comb through the optimization design of the amplitude of the input microwave signal and the bias voltage signal, and can be applied to the fields of optical communication, spectrum analysis, precision measurement and the like.

Description

Technical Field

[0001] The present invention belongs to the field of microwave photonics, and in particular relates to a large-bandwidth and high-flat optical frequency comb generating device based on microwave photonics. Background Art

[0002] As a light source with equally spaced spectrum characteristics, optical frequency combs have been widely used in precision spectroscopy, optical communications, fiber optic sensing, microwave photonics, frequency standards and other fields. The core advantage of optical frequency combs is that they can discretize broadband spectra into multiple equally spaced frequency components, thereby achieving high-resolution and high-precision frequency measurement and signal processing.

[0003] At present, there are mainly the following technical routes for the generation of optical frequency combs: ① Mode-locked laser technology: Mode-locked fiber lasers can generate equally spaced spectral lines through the resonant mode in the optical cavity. The advantage of this technology is that the frequency comb has low phase noise and good frequency stability, but due to the limitations of the physical optical cavity, its output spectral bandwidth is narrow, it is difficult to generate a large-bandwidth optical frequency comb, and the equipment is complex and difficult to adjust. ② Microresonator frequency comb: Generate a frequency comb in a microresonator through nonlinear optical effects (such as the Kerr effect). This technology can generate a wider spectrum bandwidth with a very small device size, but the flatness of its output frequency comb is low, and it is very sensitive to changes in the external environment (such as temperature and pressure), and it is difficult to maintain long-term stability. ③ Electro-optic modulator frequency comb: Based on the electro-optic modulation technology of the Mach-Zehnder modulator (MZM), an optical frequency comb with adjustable frequency interval can be generated by radio frequency modulation of a continuous wave laser signal. This method has the advantages of simple equipment structure, controllable frequency comb interval, and relatively wide bandwidth. However, due to the small number of spectral lines generated by a single modulation, multi-level modulation and high-precision control are usually required to expand the bandwidth of the optical frequency comb and optimize the flatness.

[0004] Although the existing optical frequency comb technology has been widely used, it still has the following limitations in terms of bandwidth, spectrum flatness, modulation flexibility and equipment complexity: ① Limited bandwidth: The physical structure of the mode-locked laser and microresonator limits the bandwidth of its output spectrum, making it difficult to meet the needs of future high-speed optical communication systems for optical frequency combs with larger bandwidths. ② Poor flatness: Existing frequency comb technology usually has large power unevenness in each frequency interval of the spectrum. Especially for microresonator frequency combs, the power at both ends of the spectrum will drop significantly, affecting the application of frequency combs in high-precision measurement and spectrum analysis. ③ System complexity: The mode-locked laser system is complex, difficult to adjust, and sensitive to environmental conditions; although the microresonator system is small in size, it is limited by the nonlinear effects of the material and the characteristics of the resonant cavity, making it difficult to achieve flexible regulation. ④ Insufficient modulation flexibility: Although the traditional electro-optical modulation technology has good adjustability, the number of spectral lines output by the single-stage modulator is small, and the complexity of the system needs to be increased to achieve the generation of large-bandwidth frequency combs.

[0005] In order to overcome the limitations of existing optical frequency comb technology, microwave photonics technology has been introduced into the generation of optical frequency combs. By modulating optical signals with microwave signals and combining them with multi-level modulation of differential Mach-Zehnder modulators (MZMs), the bandwidth of the optical frequency comb can be effectively expanded and its flatness can be improved. In addition, the frequency interval and power distribution of the optical frequency comb can be flexibly adjusted by utilizing the high-precision control capability of microwave signals. However, the current optical frequency comb generation technology based on microwave photonics still faces the following challenges: ① The complexity of the multi-level modulation system and the phase matching problem between different modulators make it still difficult to achieve a high-flatness and large-bandwidth frequency comb. ② How to accurately control the modulation index and bias voltage of the modulator to ensure the flatness and frequency stability of the output optical frequency comb.

[0006] Therefore, further technical improvements are still needed. Summary of the invention

[0007] The purpose of the present invention is to provide a high-bandwidth and high-flatness optical frequency comb generator based on microwave photonics to solve the shortcomings of the prior art in terms of bandwidth and flatness and meet the needs of higher precision applications. The present invention can achieve an optical frequency comb output with large bandwidth and high flatness through a multi-level differential Mach-Zehnder modulator (MZM) and its optimized combination, combined with the precision control of a multi-channel arbitrary waveform generator and a DC voltage regulator.

[0008] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0009] A large-bandwidth, high-flat optical frequency comb generating device based on microwave photonics, comprising a continuous wave laser, a power splitter 1, a power splitter 2, a differential MZM 1, a differential MZM 2, a differential MZM 3, a differential MZM 4, a differential MZM 5, a 90° phase shifter 1, a 90° phase shifter 2, an arbitrary waveform generator 1, an arbitrary waveform generator 2, an arbitrary waveform generator 3, a DC stabilized voltage source 1, a DC stabilized voltage source 2, a DC stabilized voltage source 3, a DC stabilized voltage source 4, a DC stabilized voltage source 5, a power combiner 1, and a power combiner 2;

[0010] The differential MZM1, differential MZM2, power splitter 1, power combiner 1, and 90° phase shifter 1 constitute an integrated device dual parallel Mach-Zehnder modulator 1 (DP-MZM1) for spectrum broadening;

[0011] The differential MZM4, differential MZM5, power splitter 2, power combiner 2, and 90° phase shifter 2 constitute a dual parallel Mach-Zehnder modulator 2 (DP-MZM2), which is used to further increase the number of spectral lines and improve flatness;

[0012] The two outputs 1a and 1b of the arbitrary waveform generator 1 are respectively connected to the radio frequency input ports of differential MZM1 and differential MZM2, and the DC voltage regulator 1 and the DC voltage regulator 2 are respectively connected to the DC bias voltage input ports of differential MZM1 and differential MZM2; the output of the arbitrary waveform generator 2 is connected to the radio frequency input port of differential MZM3, and the DC voltage regulator 3 is connected to the DC bias voltage input port of differential MZM3; the two outputs 3a and 3b of the arbitrary waveform generator 3 are respectively connected to the radio frequency input ports of differential MZM4 and differential MZM5, and the DC voltage regulator 4 and the DC voltage regulator 5 are respectively connected to the DC bias voltage input ports of differential MZM4 and differential MZM5; each DC voltage regulator and the arbitrary waveform generator are respectively used to control the operating point and modulation index of each Mach-Zehnder modulator;

[0013] The differential MZM3 is an integrated device dual-drive Mach-Zehnder modulator (DD-MZM) used to evenly distribute bandwidth, improve flatness, and increase the number of spectral lines;

[0014] The optical signal of a specific center frequency output by the continuous wave laser is input into the dual parallel Mach-Zehnder modulator 1. At this time, the power splitter 1 divides the input optical signal into two optical signals with equal power and frequency, which are respectively used as the input optical signals of the upper and lower arms of the dual parallel Mach-Zehnder modulator 1, and the signal power is half of the output signal of the continuous wave laser; the DC voltage regulator 1 is controlled, the output voltage of the DC voltage regulator 2 and the 90° phase shifter 1 are controlled, so that the differential MZM1 works at the minimum working point, the differential MZM2 works at the maximum working point, and the dual parallel Mach-Zehnder modulator 1 works at Orthogonal working point; then, by controlling the two outputs 1a and 1b of the arbitrary waveform generator 1 to output different RF signal amplitudes and the same frequency f1, the modulation indexes m1 and m2 of the differential MZM1 and the differential MZM2 are controlled to output ±1, ±3 order and 0, ±2 order optical harmonics of the RF frequency f1 respectively, and then through the power synthesizer 1, the dual parallel Mach Zehnder modulator 1 outputs 0, ±1, ±2, ±3, a total of seven spectral lines; the output of the dual parallel Mach Zehnder modulator 1 is used as the input of the dual drive Mach Zehnder modulator, and the DC voltage regulator 3 and the arbitrary waveform generator 2 are controlled to generate a spectral line. The amplitude and frequency f2 of the frequency signal are used to control the modulation index m3 and the special working point of the differential MZM3, so that the dual-drive Mach-Zehnder modulator outputs 35 high-flat optical frequency combs with a bandwidth of 2*f1 and an interval of f2; the output of the dual-drive Mach-Zehnder modulator is used as the input of the dual-parallel Mach-Zehnder modulator 2, at which time the power splitter 2 divides the input optical signal into two optical signals with equal power and frequency, which are respectively used as the input optical signals of the upper and lower arms of the dual-parallel Mach-Zehnder modulator 2, and the DC voltage regulator 4, the output voltage of the DC voltage regulator 5 and the 90° phase shifter 2 are controlled to make The differential MZM4 works at the minimum working point, the differential MZM5 works at the maximum working point, and the dual parallel Mach Zehnder modulator 2 works at the orthogonal working point; then, by controlling the arbitrary waveform generators 3a and 3b to output different RF signal amplitudes and the same frequency f3, the modulation indexes m4 and m5 of the differential MZM4 and the differential MZM5 are controlled to output ±1, ±3 order and 0, ±2 order optical harmonics of the RF frequency f3 respectively, and finally, through the power synthesizer 2, the dual parallel Mach Zehnder modulator 2 outputs 245 large-bandwidth, high-flat optical frequency combs with a bandwidth of 2*f1 and an interval of f3.

[0015] Furthermore, the continuous wave laser uses a DFB (Distributed Feedback Laser) laser with a central wavelength of 1552nm, a line width of less than 100kHz, an output optical power of 17dBm, and a RIN of less than -160dB / Hz, that is, a distributed feedback laser; a dual parallel Mach-Zehnder modulator and a dual-drive Mach-Zehnder modulator with a splitting ratio of 1:1, a sub-MZM insertion loss of 6dB, an RF half-wave voltage of 7V, and an extinction ratio>30 are selected; arbitrary waveform generator 1, arbitrary waveform generator 2 and arbitrary waveform generator 3 use analog signal source N5183A MXG to provide 9k-40GHz signal coverage; DC voltage regulator 1, DC voltage regulator 2, DC voltage regulator 3, DC voltage regulator 4 and DC voltage regulator 5 have an adjustable voltage of 0-20V with an accuracy of 0.01V.

[0016] Furthermore, by controlling the frequencies of the radio frequency signals inputted by the arbitrary waveform generators 1 , 2 and 3 , f1 = 5*f2 and f2 = 7*f3.

[0017] Furthermore, by controlling the DC voltage regulator 3, the differential MZM 3 is made to work at a special working point, that is, a working point where the phase difference caused by the DC bias is about 1 radian.

[0018] Furthermore, by controlling the amplitude of the input RF signal, the modulation indexes of differential MZM1, differential MZM2, differential MZM3, differential MZM4, and differential MZM5 are respectively m1=3.07, m2=1.83, m3=1.84, m4=3.07, and m5=1.83.

[0019] The invention discloses a high-bandwidth and high-flat optical frequency comb generator based on microwave photonics, which has the following advantages:

[0020] The present invention calculates and optimizes the frequency and amplitude of the radio frequency signal and the bias voltage of each MZM through a cascade modulator, thereby achieving a wide-bandwidth and high-flatness optical frequency comb output. Figure 4 It can be seen from the output spectrum that the optical frequency comb has a flatness of 0.5dB, a large number of spectrum lines, and a large spectrum bandwidth, which has obvious advantages over the same type of OFC generation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a large-bandwidth, high-flat optical frequency comb generating device based on microwave photonics according to the present invention;

[0022] Figure 2 is an output spectrum diagram of the dual parallel Mach-Zehnder modulator 1 of the present invention;

[0023] Figure 3The spectrum diagram of the output of the dual-drive Mach-Zehnder modulator of the present invention;

[0024] Figure 4 This is the optical frequency comb diagram finally output by the present invention. DETAILED DESCRIPTION

[0025] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a large-bandwidth, high-flat optical frequency comb generating device based on microwave photonics of the present invention in conjunction with the accompanying drawings.

[0026] The structure of a large-bandwidth, high-flat optical frequency comb generator based on microwave photonics used in the present invention is as follows: Figure 1 As shown: it is composed of a continuous wave laser, a power splitter 1, a power splitter 2, a differential MZM1, a differential MZM2, a differential MZM3, a differential MZM4, a differential MZM5, a 90° phase shifter 1, a 90° phase shifter 2, an arbitrary waveform generator 1, an arbitrary waveform generator 2, an arbitrary waveform generator 3, a DC voltage regulator 1, a DC voltage regulator 2, a DC voltage regulator 3, a DC voltage regulator 4, a DC voltage regulator 5, a power synthesizer 1, and a power synthesizer 2; wherein, the differential MZM1, the differential MZM2, the power splitter 1, the power synthesizer 1, and the 90° phase shifter 1 constitute an integrated device dual parallel Mach Zehnder modulator 1 (DP-MZM1); the differential MZM3 is an integrated device dual drive Mach Zehnder modulator (DD-MZM); the differential MZM4, the differential MZM5, the power The power splitter 2, the power synthesizer 2, and the 90° phase shifter 2 constitute a dual parallel Mach-Zehnder modulator 2 (DP-MZM2); wherein, the two outputs 1a and 1b of the arbitrary waveform generator 1 are respectively connected to the RF input ports of the differential MZM1 and the differential MZM2, and the DC voltage regulator 1 and the DC voltage regulator 2 are respectively connected to the DC bias voltage input ports of the differential MZM1 and the differential MZM2; the output of the arbitrary waveform generator 2 is connected to the RF input port of the differential MZM3, and the DC voltage regulator 3 is connected to the DC bias voltage input port of the differential MZM3; the two outputs 3a and 3b of the arbitrary waveform generator 3 are respectively connected to the RF input ports of the differential MZM4 and the differential MZM5, and the DC voltage regulator 4 and the DC voltage regulator 5 are respectively connected to the DC bias voltage input ports of the differential MZM4 and the differential MZM5.

[0027] A continuous wave laser outputs an optical signal with a specific center frequency. The optical signal output by the laser is continuous and has only a single frequency. In an ideal state, the time domain signal is a sine wave. The optical signal is input into a dual parallel Mach-Zehnder modulator 1. At this time, the power splitter 1 divides the input optical signal into two optical signals with equal power and frequency, which are respectively used as the input optical signals of the upper and lower arms of the dual parallel Mach-Zehnder modulator 1. The signal power is half of the output signal of the continuous wave laser; the DC voltage regulator 1, the output voltage of the DC voltage regulator 2 and the 90° phase shifter 1 are controlled to make the differential MZM1 work at the minimum working point, the differential MZM2 work at the maximum working point, and the dual parallel Mach-Zehnder modulator 1 work at the orthogonal working point; then, the arbitrary waveform generators 1a and 1b are controlled to output different RF signal amplitudes (V1 and V2) and the same frequency f1, and the modulation indexes m1 and m2 of the differential MZM1 and the differential MZM2 are controlled, wherein:

[0028]

[0029] Where V π is the half-wave voltage of the MZM modulator.

[0030] According to the Bessel function expansion:

[0031]

[0032] In the formula, m f is the modulation index of the MZM modulator, ω m is the RF signal frequency, J 0 J 2n J 2n+1 The Bessel function coefficients are selected. By selecting the appropriate modulation index, differential MZM1 and differential MZM2 output ±1, ±3 and 0, ±2 order optical harmonics of the RF frequency f1 respectively, and then through the power synthesizer 1, the dual parallel Mach-Zehnder modulator 1 outputs 0, ±1, ±2, ±3, a total of seven spectral lines. The output spectral lines of the dual parallel Mach-Zehnder modulator 1 are as follows: Figure 2 shown.

[0033] The output of the dual parallel Mach-Zehnder modulator 1 is used as the input of the dual-drive Mach-Zehnder modulator. By controlling the RF signal amplitude V3 and frequency f2 of the DC voltage regulator 3 and the arbitrary waveform generator 2, the modulation index m3 and the special working point of the differential MZM3 are controlled, where:

[0034]

[0035] Where V π is the half-wave voltage of the MZM modulator.

[0036] The dual-drive Mach-Zehnder modulator has an output bandwidth of 2*f1 and 35 highly flat optical frequency combs with an interval of f2. The output spectrum is as follows: Figure 3 shown.

[0037] The output of the dual-drive Mach-Zehnder modulator is then used as the input of the dual-parallel Mach-Zehnder modulator 2. At this time, the power splitter 2 divides the input optical signal into two optical signals with equal power and frequency, which are respectively used as the input optical signals of the upper and lower arms of the dual-parallel Mach-Zehnder modulator 2, and the DC voltage regulator 4, the output voltage of the DC voltage regulator 5 and the 90° phase shifter 2 are controlled, so that the differential MZM4 works at the minimum working point, the differential MZM5 works at the maximum working point, and the dual-parallel Mach-Zehnder modulator 2 works at the orthogonal working point; then, the arbitrary waveform generators 3a and 3b are controlled to output different RF signal amplitudes (V4 and V5) and the same frequency f3, and the modulation indexes m4 and m5 of the differential MZM4 and the differential MZM5 are controlled, wherein:

[0038]

[0039] According to the Bessel function expansion and the selection of modulation index, differential MZM4 and differential MZM5 output ±1, ±3 and 0, ±2 order optical harmonics of RF frequency f3 respectively. Finally, through power synthesizer 2, dual parallel Mach-Zehnder modulator 2 outputs 245 large bandwidth and high flat optical frequency combs with a bandwidth of 2*f1 and an interval of f3. The output spectrum is as follows: Figure 4 shown.

[0040] In order to realize the generation of equally spaced optical frequency combs, the frequency of the RF signal input to the arbitrary waveform generator is controlled so that f1 = 5*f2 and f2 = 7*f3.

[0041] By controlling the DC voltage regulator 3, the differential MZM3 works at a special working point, that is, the working point where the phase difference caused by the DC bias is about 1 radian. This working point makes the optical signal passing through the dual-driven Mach-Zehnder modulator generate 5 high-flatness spectral lines of 0, ±1, and ±2 after Bessel function expansion.

[0042] After calculation and optimization of the first kind of Bessel function and by controlling the amplitude of the input RF signal, the modulation indexes of differential MZM1, differential MZM2, differential MZM3, differential MZM4, and differential MZM5 are m1=3.07, m2=1.83, m3=1.84, m4=3.07, and m5=1.83, respectively.

[0043] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A high-bandwidth, high-flat optical frequency comb generator based on microwave photonics, characterized in that: It is composed of a continuous wave laser, a power splitter 1, a power splitter 2, a differential MZM1, a differential MZM2, a differential MZM3, a differential MZM4, a differential MZM5, a 90° phase shifter 1, a 90° phase shifter 2, an arbitrary waveform generator 1, an arbitrary waveform generator 2, an arbitrary waveform generator 3, a DC voltage regulator 1, a DC voltage regulator 2, a DC voltage regulator 3, a DC voltage regulator 4, a DC voltage regulator 5, a power combiner 1, and a power combiner 2; The differential MZM1, differential MZM2, power splitter 1, power synthesizer 1, and 90° phase shifter 1 constitute an integrated device dual parallel Mach-Zehnder modulator 1 for spectrum broadening; wherein the power splitter 1 evenly divides the laser source into two paths, which are respectively connected to the differential MZM1 and differential MZM2 light source input ports, the differential MZM2 output is connected to the 90° phase shifter 1, and the differential MZM1 and 90° phase shifter 1 are connected to the power synthesizer 1; The differential MZM4, differential MZM5, power splitter 2, power synthesizer 2, and 90° phase shifter 2 constitute a dual parallel Mach-Zehnder modulator 2, which is used to increase the number of spectral lines and improve flatness; wherein the power splitter 2 is connected to the differential MZM4 and differential MZM5 light source input ports respectively, the differential MZM5 output is connected to the 90° phase shifter 2, and the differential MZM4 and 90° phase shifter 2 are connected to the power synthesizer 2; The two outputs 1a and 1b of the arbitrary waveform generator 1 are respectively connected to the radio frequency input ports of differential MZM1 and differential MZM2, and the DC voltage regulator 1 and the DC voltage regulator 2 are respectively connected to the DC bias voltage input ports of differential MZM1 and differential MZM2; the output of the arbitrary waveform generator 2 is connected to the radio frequency input port of differential MZM3, and the DC voltage regulator 3 is connected to the DC bias voltage input port of differential MZM3; the two outputs 3a and 3b of the arbitrary waveform generator 3 are respectively connected to the radio frequency input ports of differential MZM4 and differential MZM5, and the DC voltage regulator 4 and the DC voltage regulator 5 are respectively connected to the DC bias voltage input ports of differential MZM4 and differential MZM5; each DC voltage regulator and the arbitrary waveform generator are respectively used to control the operating point and modulation index of each Mach-Zehnder modulator; The differential MZM3 is an integrated device dual-drive Mach-Zehnder modulator used to evenly divide bandwidth, improve flatness, and increase the number of spectral lines; The optical signal of a specific center frequency output by the continuous wave laser is input into the dual parallel Mach-Zehnder modulator 1. At this time, the power splitter 1 divides the input optical signal into two optical signals with equal power and frequency, which are respectively used as the input optical signals of the upper and lower arms of the dual parallel Mach-Zehnder modulator 1, and the signal power is half of the output signal of the continuous wave laser; the DC voltage regulator 1 is controlled, the output voltage of the DC voltage regulator 2 and the 90° phase shifter 1 are controlled, so that the differential MZM1 works at the minimum working point, the differential MZM2 works at the maximum working point, and the dual parallel Mach-Zehnder modulator 1 works at Orthogonal working point; then, by controlling the two outputs 1a and 1b of the arbitrary waveform generator 1 to output different RF signal amplitudes and the same frequency f1, the modulation indexes m1 and m2 of the differential MZM1 and the differential MZM2 are controlled to output ±1, ±3 order and 0, ±2 order optical harmonics of the RF frequency f1 respectively, and then through the power synthesizer 1, the dual parallel Mach Zehnder modulator 1 outputs 0, ±1, ±2, ±3, a total of seven spectral lines; the output of the dual parallel Mach Zehnder modulator 1 is used as the input of the dual drive Mach Zehnder modulator, and the DC voltage regulator 3 and the arbitrary waveform generator 2 are controlled to generate a spectral line. The amplitude and frequency f2 of the frequency signal are used to control the modulation index m3 and the special working point of the differential MZM3, so that the dual-drive Mach-Zehnder modulator outputs 35 high-flat optical frequency combs with a bandwidth of 2*f1 and an interval of f2; the output of the dual-drive Mach-Zehnder modulator is used as the input of the dual-parallel Mach-Zehnder modulator 2, at which time the power splitter 2 divides the input optical signal into two optical signals with equal power and frequency, which are respectively used as the input optical signals of the upper and lower arms of the dual-parallel Mach-Zehnder modulator 2, and the DC voltage regulator 4, the output voltage of the DC voltage regulator 5 and the 90° phase shifter 2 are controlled to make The differential MZM4 works at the minimum working point, the differential MZM5 works at the maximum working point, and the dual parallel Mach Zehnder modulator 2 works at the orthogonal working point; then, by controlling the arbitrary waveform generators 3a and 3b to output different RF signal amplitudes and the same frequency f3, the modulation indexes m4 and m5 of the differential MZM4 and the differential MZM5 are controlled to output ±1, ±3 order and 0, ±2 order optical harmonics of the RF frequency f3 respectively, and finally, through the power synthesizer 2, the dual parallel Mach Zehnder modulator 2 outputs 245 large-bandwidth, high-flat optical frequency combs with a bandwidth of 2*f1 and an interval of f3.

2. According to claim 1, a large-bandwidth, high-flat optical frequency comb generator based on microwave photonics is characterized in that: The continuous wave laser uses a DFB laser with a central wavelength of 1552nm, a line width of less than 100kHz, an output optical power of 17dBm, and a RIN lower than -160dB / Hz; a dual parallel Mach-Zehnder modulator and a dual-drive Mach-Zehnder modulator with a splitting ratio of 1:1, a sub-MZM insertion loss of 6dB, an RF half-wave voltage of 7V, and an extinction ratio>30 are used; arbitrary waveform generator 1, arbitrary waveform generator 2, and arbitrary waveform generator 3 use the analog signal source N5183A MXG to provide 9k-40GHz signal coverage; the voltage of DC stabilized voltage source 1, DC stabilized voltage source 2, DC stabilized voltage source 3, DC stabilized voltage source 4, and DC stabilized voltage source 5 is adjustable from 0-20V with an accuracy of 0.01V.

3. The device for generating a large-bandwidth, high-flat optical frequency comb based on microwave photonics according to claim 1, characterized in that: By controlling the frequencies of the radio frequency signals inputted by arbitrary waveform generator 1, arbitrary waveform generator 2 and arbitrary waveform generator 3, f1 = 5*f2 and f2 = 7*f3.

4. The device for generating a large-bandwidth, high-flat optical frequency comb based on microwave photonics according to claim 1, characterized in that: By controlling the DC voltage regulator 3, the differential MZM 3 is made to work at a special working point, that is, a working point where the phase difference caused by the DC bias is about 1 radian.

5. The device for generating a large-bandwidth, high-flat optical frequency comb based on microwave photonics according to claim 1, characterized in that: By controlling the amplitude of the input RF signal, the modulation indexes of differential MZM1, differential MZM2, differential MZM3, differential MZM4 and differential MZM5 are respectively m1=3.07, m2=1.83, m3=1.84, m4=3.07 and m5=1.83.

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