A high repetition rate fiber optical comb based on burst pulse train modulation

Abstract

The present invention discloses a high repetition frequency fiber optical comb based on burst pulse train modulation, comprising a high repetition frequency fiber laser with repetition frequency locking, a peak power enhancer, a fiber amplifier, an optical coupler, a nonlinear spectrum expander, a carrier envelope frequency offset detection system, a first photodetector, and a phase-locked loop feedback module circuit, which are sequentially connected and looped. The present invention provides a method for realizing a high repetition frequency fiber optical comb, which can provide a reliable high repetition frequency optical comb light source for application fields such as astronomical spectrum measurement, optical communication, and laser radar.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to a high repetition frequency optical fiber comb based on burst pulse train modulation. Background Art

[0002] Since its advent, the optical frequency comb (hereinafter referred to as "optical comb") has developed over the past two decades and has become of great value in applications such as optical atomic clocks, generation of ultra-low-noise microwave signals, astronomical spectrum calibration, and precision ranging.

[0003] An optical comb appears as a series of stable pulse sequences with strictly equal time intervals in the time domain, and as a comb-shaped optical spectrum with strictly equal frequency intervals in the frequency domain. It is an important bridge connecting microwave frequencies and optical frequencies, and is also a precision instrument for generating precise frequency signals. A mode-locked laser can generate laser pulses with equal repetition frequencies, and is a good light source for realizing an optical comb. However, the output frequency signal of a free-running mode-locked laser is not stable enough, so its two frequency components, the repetition frequency and the carrier envelope frequency offset, are usually doubly locked to improve frequency stability. Adjusting the cavity length based on a piezoelectric actuator (PZT) is a good method for repetition frequency locking. An error signal is obtained by beating the repetition frequency signal of the mode-locked pulse with the stable frequency signal of the stable frequency microwave source. Based on the error signal, the laser cavity is adjusted using a phase-locked loop feedback loop to achieve repetition frequency locking. For locking the carrier envelope frequency offset, as described in patent document CN201410219345, the f-2f beat frequency method is usually used to extract the carrier envelope frequency offset f. ceo This method first requires the use of high peak power femtosecond pulses to pump the nonlinear medium to generate a supercontinuum spectrum of more than one octave, and then extract the low frequency signal f n and high frequency signal f 2n , by multiplying the low-frequency signal f n Get the frequency-doubled signal 2f n , and then beat the frequency of the doubled frequency signal with the high frequency signal to obtain f ceo signal, and finally the phase-locked loop feedback circuit to f ceo The signal is locked.

[0004] Mode-locked fiber combs based on the f-2f beat frequency method have certain requirements for pulse peak power. Compared with MHz repetition rate combs, under the same average output power conditions, for high-repetition-rate mode-locked fiber laser combs with GHz repetition rates, increasing the pulse repetition rate will cause the pulse peak power to decrease by more than 1 to 2 orders of magnitude. When pulse-pumping nonlinear media, this will seriously reduce the quality of the generated supercontinuum spectrum, and may even make it impossible to produce a supercontinuum spectrum spanning an octave. This makes it difficult to extract the carrier envelope frequency offset signal, making it difficult to achieve frequency stabilization of GHz repetition rate fiber lasers. These problems have led to the current lack of a method for achieving mode-locked fiber laser combs with repetition rates above GHz. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a high-repetition-rate fiber comb based on burst pulse train modulation, a high-repetition-rate fiber laser based on repetition-rate locking, and combines burst pulse train modulation technology with fiber laser amplification technology to achieve femtosecond pulse output and peak power improvement while maintaining the high-repetition-rate pulse characteristics, and generates a supercontinuum spectrum spanning one octave by pumping a nonlinear spectrum expander with a femtosecond pulse. Finally, based on the f-2f self-reference method and phase-locked loop technology, the carrier envelope frequency offset is extracted and locked, and a high-repetition-rate fiber comb with a repetition frequency greater than 1 GHz is realized, which can provide a reliable high-repetition-rate comb light source for application fields such as astronomical spectral measurement, optical communication, and lidar.

[0006] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0007] The present invention provides a high repetition rate fiber comb based on burst pulse train modulation, comprising a high repetition rate fiber laser with repetition rate locking, a peak power booster, a fiber amplifier, an optical coupler, a nonlinear spectrum expander, a carrier envelope frequency offset detection system, a first photodetector, and a phase-locked loop feedback module circuit, which are sequentially connected and connected into a loop;

[0008] Among them, the repetition rate locked high repetition rate fiber laser is used to output continuous wave mode-locked picosecond pulses with a locked repetition rate greater than 1GHz; the peak power booster modulates the continuous wave mode-locked picosecond pulses with a GHz repetition rate into a burst pulse train with a MHz repetition rate to enhance the pulse peak power; the modulated burst pulse train is amplified by the fiber amplifier and compressed by the soliton effect to produce femtosecond pulses; the femtosecond pulses are split into two signals by the optical coupler, one of which is output as an optical comb signal, and the other generates a supercontinuum spectrum with a frequency band exceeding one octave after passing through a nonlinear spectrum expander; the carrier envelope frequency offset signal f is further obtained using the carrier envelope frequency offset detection system. ceo and received by the first photodetector; the detected fceo The signal is fed back through the phase-locked loop module circuit to adjust the pump power of the high repetition rate fiber laser with repetition rate locked to achieve f ceo The signal is locked, thus achieving an optical comb with stable frequency signal output.

[0009] Furthermore, the repetition rate locked high repetition rate fiber laser is locked to a stable frequency reference source, and can achieve continuous wave mode-locked picosecond pulse output with a repetition rate greater than 1 GHz and locked repetition rate.

[0010] Furthermore, the peak power enhancer realizes modulation of high repetition rate pulses according to the waveform of the applied modulation signal; by loading a square wave signal with a MHz repetition rate, the continuous wave mode-locked picosecond pulse with a GHz repetition rate is modulated into a burst pulse train with a MHz repetition rate to enhance the pulse peak power.

[0011] Furthermore, the fiber amplifier is a single-stage or multi-stage cascaded rare earth ion-doped fiber amplifier, and its applicable pulse amplification wavelength range matches the output pulse wavelength of the repetition rate-locked high repetition rate fiber laser; the fiber amplifier has two functions: one is to power amplify the modulated MHz repetition rate burst pulse train; the other is to combine the soliton effect pulse compression technology to generate femtosecond pulses.

[0012] Furthermore, the carrier envelope frequency offset detection system includes a collimator, a dichroic mirror, an optical frequency conversion medium, a delay device consisting of a first reflector and a second reflector, a beam splitter and a narrowband optical filter.

[0013] The collimator is used to convert the supercontinuum signal into a spatial light signal, and the dichroic mirror is used to separate the supercontinuum into a low-frequency signal f n The red light and the high frequency signal f 2n The optical frequency conversion medium is used to convert red light into blue light containing 2f n The delay device is used to delay the blue light, and the beam splitter is used to delay the blue light. n The frequency-multiplied signal and the high-frequency signal f 2n The blue light is combined and beat to obtain the carrier envelope frequency offset signal f ceo light signal.

[0014] The carrier envelope frequency offset detection system is used to extract the carrier envelope frequency offset signal f ceo ; A supercontinuum spectrum spanning an octave contains many frequency components. According to the optical comb formula, each frequency in the optical comb can be expressed as f n =nf rep +f ceo , where f repis the pulse repetition frequency, n represents the nth frequency; by dividing the low-frequency signal f contained in the supercontinuum across an octave n and high frequency signal f 2n Filter out low-frequency signals f n After frequency doubling, it becomes 2f n signal, 2f n Signal and f 2n After the signal is beat, f is obtained ceo Signal (beat frequency process can be expressed by the formula: 2f n -f 2n =(2nf rep +2f ceo )-(2nf rep +f ceo )=f ceo ).

[0015] Furthermore, the first photoelectric detector is used to receive the carrier envelope frequency offset f extracted by the carrier envelope frequency offset detection system. ceo signal and convert it from optical signal to electrical signal.

[0016] Furthermore, the repetition rate locked high repetition rate fiber laser includes an ultrashort fiber laser resonator, a piezoelectric actuator, a wavelength division multiplexer, a pump light source, an isolator, a coupler, a second photodetector, a bandpass filter, a radio frequency amplifier, a first mixer, a first frequency reference source, a first low-pass filter and a first proportional differential integrator.

[0017] The pump light source is used to pump the ultrashort fiber laser resonator, which is used to generate continuous wave mode-locked picosecond pulses with a repetition frequency greater than GHz. The wavelength division multiplexer is used to output the continuous wave mode-locked picosecond pulses generated by the ultrashort fiber laser resonator. The isolator is used to prevent the return light from returning to the ultrashort fiber laser resonator and affecting the stable mode-locked state. The coupler is used to output two signals, one of which is used for laser pulse signal output and the other is used for frequency stabilization. The second photodetector is used to convert the frequency-stabilized signal into an electrical signal. The bandpass filter is used to filter the electrical signal to obtain a pulse fundamental frequency repetition frequency signal. The radio frequency amplifier is used to perform radio frequency amplification on the fundamental frequency repetition frequency signal. The first mixer is used to beat the fundamental frequency repetition frequency signal and the first frequency reference source to obtain a low-frequency error signal. The first low-pass filter is used to purify the error signal. The first proportional differential integrator is used to drive the piezoelectric actuator according to the purified error signal to adjust the cavity length of the ultrashort fiber laser resonator to control the pulse repetition frequency.

[0018] Furthermore, the phase-locked loop feedback module circuit is used to lock f ceo signal; by receiving the first photodetector f ceoThe signal beats with a stable frequency reference source to obtain an error signal, which is fed back to a high repetition rate fiber laser with repetition rate locking to further adjust the pump power to achieve f ceo Signal locked.

[0019] Furthermore, the phase-locked loop feedback module circuit includes a bandpass filter, a radio frequency amplifier, a second mixer, a second frequency reference source, a second low-pass filter and a second proportional differential integrator.

[0020] The bandpass filter is used to filter out the carrier envelope frequency offset signal f ceo The radio frequency amplifier is used to amplify the signal, and the second mixer is used to remove the useless frequency components in the carrier envelope frequency offset signal f ceo The second low-pass filter is used to filter out useless frequency components in the error signal, and the second proportional differential integrator is used to generate a control signal according to the error signal to adjust the pump power of the pump light source to achieve the carrier envelope frequency offset signal f ceo Lock.

[0021] Compared with the existing technology, the present invention can achieve at least the following beneficial effects:

[0022] The core component of this invention is a repetition-rate locked high-repetition-rate fiber laser. Through optical modulation technology, continuous-wave mode-locked picosecond pulses with a repetition rate greater than 1 GHz are modulated into burst pulse trains with a MHz repetition rate. Combined with fiber laser amplification technology, this method effectively boosts the peak power of femtosecond pulses while maintaining the characteristics of GHz repetition-rate pulse signals. This produces a high-quality supercontinuum spectrum spanning an octave, creating favorable conditions for extracting and locking carrier-envelope frequency offset signals, thereby achieving a repetition-rate optical comb greater than 1 GHz.

[0023] The present invention provides a high-repetition-rate fiber optical comb based on burst pulse train modulation. A peak power booster is used to modulate continuous-wave mode-locked picosecond pulses with a GHz repetition rate into a burst pulse train with a MHz repetition rate. During the optical amplification process, the peak power of the femtosecond pulses can be effectively increased while maintaining the characteristics of the GHz repetition rate pulse signal, thereby generating a high-quality supercontinuum spectrum and creating good conditions for extracting and locking the carrier envelope frequency offset signal, thereby achieving the purpose of realizing an optical comb with a repetition rate of more than GHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of a high repetition rate fiber comb based on burst pulse train modulation in an embodiment of the present invention.

[0025] Figure 2The figure is a schematic structural diagram of a high repetition rate fiber laser with repetition rate locking according to an embodiment of the present invention.

[0026] Figure 3 Schematic diagram of a carrier envelope frequency offset detection system according to an embodiment of the present invention.

[0027] Figure 4 Schematic diagram of a phase-locked loop feedback control module circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer and more straightforward, the specific implementation of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0029] The present invention provides a high repetition frequency fiber comb based on burst pulse train modulation, such as Figure 1 As shown, it includes a high repetition rate fiber laser 1-1 with repetition rate locking, a peak power enhancer 1-2, a fiber amplifier 1-3, an optical coupler 1-4, a nonlinear spectrum expander 1-5, a carrier envelope frequency offset detection system 1-6, a first photodetector 1-7, and a phase-locked loop feedback module circuit 1-8.

[0030] Among them, the repetition frequency locked high repetition rate fiber laser 1-1 is used to output continuous wave mode-locked picosecond pulses with a locked repetition frequency greater than 1GHz; the peak power booster 1-2 is used to modulate the continuous wave mode-locked picosecond pulses with a GHz repetition rate into a burst pulse train with a MHz repetition rate to enhance the pulse peak power; the modulated burst pulse train is amplified by the fiber amplifier 1-3 to generate femtosecond pulses; the femtosecond pulses are divided into two signals by the optical coupler 1-4, one of which is output as an optical comb signal, and the other generates a supercontinuum spectrum exceeding one octave after being pumped by the nonlinear spectrum expander 1-5; the carrier envelope frequency offset signal f is further obtained by the carrier envelope frequency offset detection system 1-6. ceo and received by the first photodetector 1-7; the detected carrier envelope frequency offset signal f ceo The signal is fed back through the phase-locked loop module circuit 1-8 to adjust the pump power of the high repetition rate fiber laser 1-1 locked with repetition rate to achieve the f ceo The signal is locked, thus achieving an optical comb with stable frequency signal output.

[0031] In some embodiments of the present invention, the peak power enhancer 1-2 is an amplitude electro-optical modulator, which modulates high repetition rate pulses according to the waveform of the applied modulation signal; by loading a square wave signal with a MHz repetition rate, the continuous wave mode-locked picosecond pulse with a GHz repetition rate is modulated into a burst pulse train with a MHz repetition rate to enhance the pulse peak power.

[0032] In some embodiments of the present invention, fiber amplifier 1-3 is a single-stage or multi-stage cascade of rare-earth ion-doped fiber amplifiers, whose applicable pulse amplification wavelength range matches the output pulse wavelength of repetition-rate-locked high-repetition-rate fiber laser 1-1. Fiber amplifier 1-3 has two functions: first, to amplify the power of modulated MHz repetition-rate burst pulse trains; second, to generate femtosecond pulses by combining soliton-effect pulse compression technology.

[0033] In some embodiments of the present invention, the nonlinear spectrum expander 1-5 is a highly nonlinear optical fiber that is pumped by femtosecond pulses to generate a supercontinuum spectrum spanning one octave.

[0034] In some embodiments of the present invention, the repetition frequency locked high repetition rate fiber laser 1-1 has a laser structure as follows: Figure 2 As shown, it includes an ultrashort fiber laser resonator 2-1, a piezoelectric actuator 2-2, a wavelength division multiplexer 2-3, a pump light source 2-4, an isolator 2-5, a coupler 2-6, a second photodetector 2-7, a bandpass filter 2-8, a radio frequency amplifier 2-9, a first mixer 2-10, a first frequency reference source 2-11, a first low-pass filter 2-12 and a first proportional differential integrator 2-13.

[0035] Among them, the pump light source 2-4 pumps the ultrashort fiber laser resonator 2-1 through the wavelength division multiplexer 2-3, and combines with the passive mode locking technology to generate continuous wave mode-locked picosecond pulses with a repetition frequency greater than 1 GHz; the continuous wave mode-locked picosecond pulses generated by the ultrashort fiber laser resonator 2-1 are output through the signal end of the wavelength division multiplexer 2-3, and after passing through the isolator 2-5, they are divided into two paths by the coupler 2-6, one of which is used for laser signal output and the other for frequency stabilization. The isolator 2-5 is used to prevent the return light from returning to the ultrashort fiber laser resonator 2-1 and affecting the stable mode locking state; the signal used for frequency stabilization is converted by the second photodetector 2-7 It is an electrical signal. After passing through the bandpass filter 2-8, a pulse fundamental frequency repetition frequency signal is left. The fundamental frequency repetition frequency signal is amplified by the radio frequency amplifier 2-9 and then beats with the stable first frequency reference source 2-11 in the first mixer 2-10 to obtain a low-frequency error signal; the error signal is purified by the first low-pass filter 2-12 and then input to the first proportional differential integrator 2-13; the first proportional differential integrator 2-13 drives the piezoelectric actuator 2-2 according to the error signal to adjust the cavity length of the ultrashort fiber laser resonant cavity 2-1, thereby regulating the pulse repetition frequency and realizing locking the repetition frequency signal greater than 1GHz on the stable frequency reference source.

[0036] In some embodiments of the present invention, the carrier envelope frequency offset detection system 1-6, such as Figure 3As shown, it includes a collimator 3-1, a dichroic mirror 3-2, an optical frequency conversion medium 3-3, a first reflector 3-4, a second reflector 3-5, a beam splitter 3-6, and a narrow-band optical filter 3-7.

[0037] The collimator 3-1 converts the supercontinuum signal spanning one octave transmitted in the optical fiber into a spatial optical signal. The supercontinuum spanning one octave contains many frequency components. According to the optical comb formula, each frequency in the optical comb can be expressed as f n =nf rep +f ceo , where f rep is the pulse repetition frequency, n represents the nth frequency; the dichroic mirror 3-2 divides the supercontinuum spectrum into the low-frequency signal f n The "red light" and the high-frequency signal f 2n "Blue light"; "Red light" becomes 2f after passing through the optical frequency conversion medium 3-3 n The frequency-doubled signal enters the beam splitter 3-6; in order to make the pulses of "blue light" and "red light" overlap as much as possible in time to obtain the best beat frequency effect, the "blue light" enters the beam splitter 3-6 after being delayed by the delay device composed of the first reflector 3-4 and the second reflector 3-5; containing 2f n The frequency-multiplied signal and the high-frequency signal f 2n The "blue light" is combined into 3-6 beams in the beam splitter and beat to obtain a carrier envelope frequency offset signal f ceo The beat frequency process of the optical signal is expressed as: 2f n -f 2n =(2nf rep +2f ceo )-(2nf rep +f ceo )=f ceo Finally, the narrowband optical filter 3-7 is used to filter out useless frequency components and obtain the carrier envelope frequency offset signal f ceo .

[0038] In some embodiments of the present invention, the phase-locked loop feedback module circuit 1-8, such as Figure 4 As shown, it includes a bandpass filter 4-1, a radio frequency amplifier 4-2, a second mixer 4-3, a second frequency reference source 4-4, a second low-pass filter 4-5, and a second proportional differential integrator 4-6.

[0039] Among them, f ceo After the signal passes through the bandpass filter 4-1 to remove useless frequency components, it is amplified by the RF amplifier 4-2 and input to one end of the second mixer 4-3; the other end of the second mixer 4-3 is connected to the frequency reference source 4-3, and the carrier envelope frequency offset signal f ceoThe stable frequency signal generated by the second frequency reference source 4-4 is beat in the second mixer 4-3 to obtain a low-frequency error signal; the error signal is filtered out of useless frequency components by the second low-pass filter 4-5 and then input to the second proportional differential integrator 4-6; the second proportional differential integrator 4-6 generates a control signal according to the error signal to adjust the pump power of the pump light source 2-4 to achieve f ceo Signal lock.

[0040] The above embodiment is one of the implementation methods of the present invention, but the implementation methods of the present invention are not limited to the embodiments and test examples. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A high repetition rate fiber comb based on burst pulse train modulation, characterized in that: The invention comprises a high repetition frequency fiber laser (1-1) with repetition frequency locking, a peak power enhancer (1-2), a fiber amplifier (1-3), an optical coupler (1-4), a nonlinear spectrum expander (1-5), a carrier envelope frequency offset detection system (1-6), a first photodetector (1-7), and a phase-locked loop feedback module circuit (1-8) which are sequentially connected and connected into a loop; The high repetition frequency fiber laser (1-1) with locked repetition frequency is used to output continuous wave mode-locked picosecond pulses with locked repetition frequency greater than 1 GHz; the peak power enhancer (1-2) is used to modulate the continuous wave mode-locked picosecond pulses with a repetition frequency of GHz into burst pulse trains with a repetition frequency of MHz; the fiber amplifier (1-3) is used to amplify the modulated burst pulse train to generate femtosecond pulses; the optical coupler (1-4) is used to divide the femtosecond pulses into two signals, one signal is output as an optical comb signal, and the other signal generates a supercontinuum spectrum exceeding one octave after passing through a nonlinear spectrum expander (1-5); and the carrier envelope frequency offset detection system (1-6) is used to obtain a carrier envelope frequency offset signal f based on the supercontinuum spectrum. ceo The first photodetector (1-7) is used to receive the carrier envelope frequency deviation signal f ceo The phase-locked loop feedback module circuit (1-8) is used to adjust the pump power of the high repetition rate fiber laser (1-1) locked by the repetition frequency to achieve f ceo The signal is locked to achieve a stable frequency signal output optical comb.

2. The high repetition rate fiber comb based on burst pulse train modulation according to claim 1, characterized in that: The repetition frequency locked high repetition frequency fiber laser (1-1) is locked to a stable frequency reference source and can achieve continuous wave mode-locked picosecond pulse output with a repetition frequency greater than 1 GHz and a locked repetition frequency.

3. The high repetition rate fiber comb based on burst pulse train modulation according to claim 1, characterized in that: The peak power enhancer (1-2) realizes modulation of high repetition frequency pulses according to the waveform of the applied modulation signal; by loading a square wave signal with a MHz repetition frequency, a continuous wave mode-locked picosecond pulse with a GHz repetition frequency is modulated into a burst pulse train with a MHz repetition frequency.

4. The high repetition rate fiber comb based on burst pulse train modulation according to claim 1, characterized in that: The optical fiber amplifier (1-3) is a single-stage or multi-stage rare earth ion doped optical fiber amplifier, and its applicable pulse amplification wavelength range matches the output pulse wavelength of the repetition frequency locked high repetition frequency optical fiber laser (1-1).

5. The high repetition rate fiber comb based on burst pulse train modulation according to claim 1, characterized in that: The optical fiber amplifier (1-3) has two functions: one is to amplify the power of the modulated burst pulse train with a MHz repetition frequency; the other is to generate femtosecond pulses by combining the soliton effect pulse compression technology.

6. The high repetition rate fiber comb based on burst pulse train modulation according to claim 1, characterized in that: The first photoelectric detector (1-7) is used to receive the carrier envelope frequency deviation signal f extracted by the carrier envelope frequency deviation detection system (1-6). ceo and converts it from an optical signal into an electrical signal.

7. The high repetition rate fiber comb based on burst pulse train modulation according to claim 1, characterized in that: The carrier envelope frequency offset detection system (1-6) comprises a collimator (3-1), a dichroic mirror (3-2), an optical frequency conversion medium (3-3), a delay device, a beam splitter (3-6) and a narrowband optical filter (3-7). The collimator (3-1) is used to convert the supercontinuum signal into a spatial light signal, and the dichroic mirror (3-2) is used to separate the supercontinuum into a spatial light signal containing a low-frequency signal f n The red light and high frequency signal f 2n The optical frequency conversion medium (3-3) is used to convert red light into a wavelength containing 2f n The delay device is used to delay the blue light, and the beam splitter (3-6) is used to delay the blue light. n The frequency-multiplied signal and the high-frequency signal f 2n The blue light is combined and beat to obtain a carrier envelope frequency offset signal f ceo light signal.

8. A high repetition rate fiber comb based on burst pulse train modulation according to any one of claims 1 to 7, characterized in that: The repetition frequency locked high repetition frequency fiber laser (1-1) comprises an ultrashort fiber laser resonant cavity (2-1), a piezoelectric actuator (2-2), a wavelength division multiplexer (2-3), a pump light source (2-4), an isolator (2-5), a coupler (2-6), a second photodetector (2-7), a bandpass filter (2-8), a radio frequency amplifier (2-9), a first mixer (2-10), a first frequency reference source (2-11), a first low-pass filter (2-12) and a first proportional differential integrator (2-13). The pump light source (2-4) is used to pump the ultrashort fiber laser resonant cavity (2-1), the ultrashort fiber laser resonant cavity (2-1) is used to generate continuous wave mode-locked picosecond pulses with a repetition frequency greater than 1 GHz, the wavelength division multiplexer (2-3) is used to output the continuous wave mode-locked picosecond pulses generated by the ultrashort fiber laser resonant cavity (2-1), the isolator (2-5) is used to prevent the return light from returning to the ultrashort fiber laser resonant cavity (2-1) and affecting the stable mode-locked state, the coupler (2-6) is used to output two signals, one of which is used for laser pulse signal output and the other is used for frequency stabilization, and the second photodetector (2-7) is used to convert the frequency The frequency-stable signal is converted into an electrical signal, a bandpass filter (2-8) is used to filter the electrical signal to obtain a pulse baseband repetition frequency signal, a radio frequency amplifier (2-9) is used to perform radio frequency amplification on the baseband repetition frequency signal, a first mixer (2-10) is used to beat the baseband repetition frequency signal and a first frequency reference source (2-11) to obtain a low-frequency error signal, a first low-pass filter (2-12) is used to purify the error signal, and a first proportional differential integrator (2-13) is used to drive a piezoelectric actuator (2-2) according to the purified error signal to adjust the cavity length of an ultrashort fiber laser resonant cavity (2-1) to control the pulse repetition frequency.

9. The high repetition rate fiber comb based on burst pulse train modulation according to claim 8, characterized in that: The phase-locked loop feedback module circuit (1-8) is used to lock the carrier envelope frequency deviation signal f ceo ; By shifting the carrier envelope frequency received by the first photodetector (1-7) to a signal f ceo The error signal is obtained by beating with a stable frequency reference source, and the error signal is fed back to a high repetition rate fiber laser (1-1) with repetition rate locking to adjust the pump power of the pump light source (2-4) to realize the carrier envelope frequency offset signal f ceo locking.

10. The high repetition rate fiber comb based on burst pulse train modulation according to claim 9, characterized in that: The phase-locked loop feedback module circuit (1-8) comprises a bandpass filter (4-1), a radio frequency amplifier (4-2), a second mixer (4-3), a second frequency reference source (4-4), a second low-pass filter (4-5) and a second proportional differential integrator (4-6). The bandpass filter (4-1) is used to filter out the carrier envelope frequency deviation signal f ceo The radio frequency amplifier (4-2) is used to amplify the signal, and the second mixer (4-3) is used to amplify the carrier envelope frequency offset signal f ceo The second frequency reference source (4-4) performs frequency beat with the stable frequency signal generated by the second frequency reference source (4-4) to obtain a low-frequency error signal, the second low-pass filter (4-5) is used to filter out useless frequency components in the error signal, and the second proportional differential integrator (4-6) is used to generate a control signal according to the error signal to adjust the pump power of the pump light source (2-4) to achieve the carrier envelope frequency offset signal f ceo Lock.

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