Fabry-Perot Etalon-Based Semiconductor Laser Frequency Stabilization System and Method

Abstract

The present invention discloses a frequency stabilization system and method for a semiconductor laser based on a Fabry-Perot etalon, including: a high-precision temperature driving platform, a current control module, a distributed feedback semiconductor laser, an optical coupler with a splitting ratio of 50:50, an electro-optic modulator, a Fabry-Perot etalon, a photodetector, an arbitrary waveform generator, an electrical mixer, a low-pass filter, a high-speed comparator, a micro control unit, and a digital-to-analog converter. By adopting the technical solution of the present invention, it is possible to solve the disadvantages of the existing classical frequency stabilization laser system, such as complex design, large volume, non-tunable wavelength, and poor anti-interference ability.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic information technology, and particularly relates to a frequency stabilization system and method for a semiconductor laser based on a Fabry-Perot etalon. Background Art

[0002] In recent years, optical communication technology has developed rapidly and become the core means of modern information transmission. Due to its advantages such as high bandwidth, low loss, and anti-interference, optical fiber communication has become an ideal choice for realizing ultra-high-speed and ultra-large-capacity data transmission. As the main method for expanding the capacity of optical fiber communication systems, the communication capacity and transmission distance of dense wavelength division multiplexing technology have been continuously improved. In this context, high-precision frequency-stabilized lasers in the main communication bands, as key components in optical communication systems, their stability and precision directly affect the performance of the communication system. Therefore, researching and developing high-precision frequency-stabilized laser technology is of great significance for improving the reliability and transmission efficiency of optical communication systems.

[0003] Semiconductor lasers have the advantages of small size, low power consumption, high phase coherence, and narrow linewidth, and are considered ideal light sources for many high-precision application fields. The application of lasers in the field of precision measurement is the most extensive, especially in interferometric measurement. In precision interferometric measurement, the laser wavelength is used as a "ruler", and the principle of laser interference is used to measure important parameters such as length, displacement, and speed. Therefore, the stability of the laser wavelength (or frequency) will directly affect the accuracy of the measurement results. Therefore, precision measurement requires the laser to achieve single-frequency output while also requiring the laser frequency fluctuation to be as small as possible. However, free-running semiconductor lasers are affected by many factors, such as changes in atmospheric pressure, temperature fluctuations, external magnetic fields, and mechanical vibrations, which cause the laser wavelength to drift, the frequency fluctuation range to be greater than the natural linewidth, resulting in the broadening of the laser linewidth and the decrease in frequency stability. Therefore, establishing a suitable frequency stabilization system can improve the frequency stability of the laser, reduce the output frequency fluctuation, and thus achieve the narrowing of the laser linewidth.

[0004] Classical frequency-stabilized lasers have been able to achieve high frequency stability and reproducibility, but their system design is complex, the volume is large, and the wavelength is not tunable. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a frequency stabilization system and method for a semiconductor laser based on a Fabry-Perot etalon, which can solve the problems of complex system design, large volume, non-tunable wavelength, and poor anti-interference ability of existing classical frequency-stabilized lasers.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A semiconductor laser frequency stabilization system based on a Fabry - Perot etalon, comprising: a high - precision temperature driving platform, a current control module, a distributed feedback semiconductor laser, an optical coupler, an electro - optic modulator, a Fabry - Perot etalon, a photodetector, an arbitrary waveform generator, an electrical mixer, a low - pass filter, a high - speed comparator, a micro - control unit, and a digital - to - analog converter; wherein,

[0008] The output end of the high - precision temperature driving platform is connected to the temperature control end of the distributed feedback semiconductor laser; the output end of the current control module is connected to the current control end of the distributed feedback semiconductor laser; the output end of the distributed feedback semiconductor laser is connected to the input end of the optical coupler; one of the output ends of the optical coupler is connected to the input end of the electro - optic modulator; the other output port of the optical coupler serves as the normal output after laser frequency stabilization; one of the output ends of the arbitrary waveform generator is connected to the microwave modulation interface input end of the electro - optic modulator; the output end of the electro - optic modulator is connected to the input end of the Fabry - Perot etalon; the output end of the Fabry - Perot etalon is connected to the input end of the photodetector; the output end of the photodetector is connected to the local oscillator signal input end of the electrical mixer; the other output end of the arbitrary waveform generator is connected to the local oscillator signal input end of the electrical mixer; the output end of the electrical mixer is connected to the input end of the low - pass filter; the output end of the low - pass filter is connected to the input end of the high - speed comparator; the output end of the high - speed comparator is connected to the input end of the micro - control unit; the output end of the micro - control unit is connected to the input end of the digital - to - analog converter; the output end of the digital - to - analog converter is connected to the control end of the current control module.

[0009] Preferably, the target stable frequency of the laser emitted by the distributed feedback semiconductor laser is consistent with the center frequency of the transmission peak selected by the Fabry - Perot etalon.

[0010] Preferably, the optical coupler is an optical coupler with a splitting ratio of 50:50; the free spectral range of the Fabry - Perot etalon is 25 GHz, realizing narrow - wavelength - interval tuning of 25 GHz.

[0011] The present invention also provides a method for stabilizing the frequency of a semiconductor laser based on a Fabry - Perot etalon, comprising:

[0012] Emitting laser light through a distributed feedback semiconductor laser with controllable temperature and driving current;

[0013] Modulating the laser frequency, using the transmission spectrum of the Fabry - Perot etalon as a reference benchmark for the external stable frequency, and identifying the deviated frequency when the laser frequency deviates from this central reference frequency; wherein, the free spectral range of the Fabry - Perot etalon is 25 GHz, realizing narrow - wavelength - interval tuning of 25 GHz.

[0014] The photodetector converts the modulated transmitted optical signal into an electrical signal. The error signal caused by the laser frequency deviating from the center frequency of the transmission peak of the Fabry - Perot etalon is detected by a high - speed comparator. The micro - control unit judges the relationship between the current laser output frequency deviation and the center frequency direction of the Fabry - Perot etalon transmission peak according to the high and low levels obtained from the high - speed comparator circuit, controls the digital - to - analog converter to change the coding value with the smallest step, finely adjusts the output voltage, completes the feedback control of the laser operating current, and realizes the frequency stabilization of the laser.

[0015] Preferably, the target stable frequency of the laser output by the distributed feedback semiconductor laser is consistent with the center frequency of the transmission peak selected by the Fabry - Perot etalon.

[0016] The present invention also provides a method for stabilizing the frequency of a semiconductor laser based on a Fabry - Perot etalon, including

[0017] Step 1: Control the operating temperature of the semiconductor laser through a high - precision temperature driving platform, and provide the function of bias current and center wavelength adjustment for the semiconductor laser through the current control module, so that the semiconductor laser emits a laser with a wavelength of λ and a frequency of f.

[0018] Step 2: The output laser beam passes through an optical coupler, and the laser beam is divided into two paths. One path of the optical coupler is used as the normal output after frequency stabilization, and the other path enters an electro - optic modulator for frequency modulation; an arbitrary waveform generator provides a microwave signal source as a modulation signal, which enters the modulation port of the electro - optic modulator to modulate the laser; the transmission spectrum of the Fabry - Perot etalon is used as a reference benchmark for the external stable frequency. When the laser frequency deviates from this center reference frequency, the deviated frequency is identified.

[0019] Step 3: The photodetector converts the received optical signal into an electrical signal and enters the RF port of the electrical mixer; another output port of the arbitrary waveform generator provides a signal with the same frequency and phase as the microwave signal as the local oscillator signal of the electrical mixer, which is input to the local oscillator signal port of the electrical mixer; the low - pass filter filters out the sum - frequency signal and retains the DC feedback error signal deviating from the reference frequency.

[0020] Step 4: The high - speed comparator module converts the error signal with an uncertain amplitude into a recognized high - and - low level signal, and allows the locking point of frequency stabilization to be adjusted within a small range by setting a threshold; when the voltage of the DC error signal is higher than the threshold voltage, the high - speed comparator outputs a high - level signal; when the voltage of the DC error signal is lower than the threshold voltage, the high - speed comparator outputs a low - level signal.

[0021] Step 5: The microcontroller unit determines the position of the output wavelength of the laser relative to the central reference frequency benchmark according to the DC error signal; the microcontroller unit controls the output voltage of the digital-to-analog converter and adjusts the operating current of the laser in real time to stabilize it at the external reference standard frequency, that is, the central frequency of the transmission peak of the Fabry-Perot etalon.

[0022] Preferably, the target stable frequency of the laser output by the distributed feedback semiconductor laser is consistent with the central frequency of the transmission peak selected by the Fabry-Perot etalon.

[0023] Preferably, the optical coupler is an optical coupler with a splitting ratio of 50:50; the free spectral range of the Fabry-Perot etalon is 25 GHz, realizing narrow wavelength interval tuning of 25 GHz.

[0024] The present invention has the following technical effects:

[0025] (1) By using a distributed feedback semiconductor laser, high-speed modulation can be achieved, with low cost, small volume, easy implementation and integration.

[0026] (2) By using a Fabry-Perot etalon, the output of lasers with different wavelengths can be flexibly tuned and stabilized, reducing the dependence on multiple fixed-wavelength lasers and improving the flexibility and adaptability of the system.

[0027] (3) Designing a high-speed comparator circuit to discriminate the error signal deviating from the center frequency allows the locking point of the laser frequency stabilization to be adjusted within a small range by setting a threshold, improving the accuracy of frequency stabilization and having a simple device.

[0028] (4) By adopting a microcontroller unit, the anti-interference ability of the frequency stabilization system to external environmental fluctuations is improved.

[0029] (5) All optical devices are of fiber input / output type, simplifying the optical path and reducing the volume.

[0030] (6) A high frequency stability can be obtained and continuous stable operation can be achieved for a long time. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0032] Figure 1 It is a schematic structural diagram of a semiconductor laser frequency stabilization system based on a Fabry-Perot etalon according to an embodiment of the present invention;

[0033] Figure 2 This is a flowchart of the semiconductor laser frequency stabilization method based on a Fabry - Perot etalon in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the transmission spectrum curve of the Fabry - Perot etalon and its first - order differential curve;

[0035] Figure 4 This is a schematic diagram of the demodulation signal when the central wavelength output by the laser is at different positions of the transmission peak. Specific embodiments

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Embodiment 1:

[0039] As Figure 1 shown, an embodiment of the present invention provides a semiconductor laser frequency stabilization system based on a Fabry - Perot etalon, including: a high - precision temperature driving platform 1, a current control module 2, a distributed feedback semiconductor laser 3, an optical coupler 4 with a splitting ratio of 50:50, an electro - optical modulator 5, a Fabry - Perot etalon 6, a photodetector 7, an arbitrary waveform generator 8, an electrical mixer 9, a low - pass filter 10, a high - speed comparator 11, a micro - control unit 12, and a digital - to - analog converter 13; wherein,

[0040] The output end of the high-precision temperature driving platform 1 is connected to the temperature control end of the distributed feedback semiconductor laser 3; the output end of the current control module 2 is connected to the current control end of the distributed feedback semiconductor laser 3; the output end of the distributed feedback semiconductor laser 3 is connected to the input end of the optical coupler 4; the output end of one of the optical couplers 4 is connected to the input end of the electro-optic modulator 5; the other output port of the optical coupler serves as the normal output after laser frequency stabilization; one of the output ends of the arbitrary waveform generator 8 is connected to the input end of the microwave modulation interface of the electro-optic modulator 5; the output end of the electro-optic modulator 5 is connected to the input end of the Fabry-Perot etalon 6; the output end of the Fabry-Perot etalon 6 is connected to the input end of the photodetector 7; the output end of the photodetector 7 is connected to the local oscillator signal input end of the electrical mixer 9; the other output end of the arbitrary waveform generator 8 is connected to the local oscillator signal input end of the electrical mixer 9; the output end of the electrical mixer 9 is connected to the input end of the low-pass filter 10; the output end of the low-pass filter 10 is connected to the input end of the high-speed comparator 11; the output end of the high-speed comparator 11 is connected to the input end of the micro-control unit 12; the output end of the micro-control unit 12 is connected to the input end of the digital-to-analog converter 13; the output end of the digital-to-analog converter 13 is connected to the control end of the current control module 2.

[0041] As Figure 1 shown, the distributed feedback semiconductor laser 3 emits laser with a central wavelength of 1550 nm, and the corresponding laser frequency is approximately 193.5 THz. The high-precision temperature driving platform 1 can adjust the operating temperature of the laser with an accuracy of ±0.01 °C, resulting in a fluctuation of ±1×10 -3 nm in the central wavelength, and the corresponding central frequency fluctuation is ±125 MHz. The current control module 2 adjusts the operating current of the laser with an accuracy of ±0.01 mA, resulting in a fluctuation of ±8×10 -4The fluctuation of the nm corresponds to a central frequency fluctuation of ±100 MHz. In the embodiment of the present invention, the laser emitted by the distributed feedback semiconductor laser 3 is divided into two paths by a 50:50 optical coupler 4: one path enters the system for frequency stabilization, and the other path serves as the normal output after frequency stabilization. The laser entering the system is modulated in frequency by an electro-optic modulator 5 and then enters a Fabry-Perot etalon 6. The working wavelength range of the Fabry-Perot etalon 6 is 1525 nm - 1565 nm, and the free spectral range (FSR) is 25 GHz. The Fabry-Perot etalon 6 can achieve narrow wavelength interval tuning of 25 GHz. Assuming that the center frequency of the transmission peak at a wavelength of 1550 nm is selected as the frequency discrimination reference, when the laser frequency fluctuates, the laser transmitted through the Fabry-Perot etalon 6 can obtain a DC error signal deviating from the frequency discrimination reference frequency after passing through a photodetector 7, an electrical mixer 9, and a low-pass filter 10. In order to discriminate the error signal, the embodiment of the present invention designs a method combining a high-speed comparator 11 circuit and a microcontroller unit 12. VP is the non-inverting input terminal of the comparator, and VN is the inverting input terminal of the comparator. The value of VN serves as the threshold for shaping the input signal into high and low levels. It should be noted that when |VN - VP| < 1 mV, the shaping ability of the selected high-speed comparator 11 module for the input signal is equivalent to using an analog-to-digital converter with an effective precision of 12 - 14 bits to judge the magnitude of the error signal. Under the premise that the performance of the high-speed comparator 11 circuit is sufficient for the frequency stabilization system, it also has the advantages of simple implementation, low cost, and low delay. By designing the high-speed comparator 11 module, the error signal with an uncertain amplitude is converted into a high and low level signal that can be recognized by the microcontroller unit 12, and it is allowed to slightly adjust the locking point of the frequency stabilization of the distributed feedback semiconductor laser 3 by setting the threshold voltage. The microcontroller unit 12 uses a main control chip of model STM32F103RCT6 to discriminate the level signal output by the high-speed comparator 11 module, and according to the level high and low, controls the digital-to-analog converter 13 to change its output voltage according to the timing requirements, and sends the encoded value of the digital-to-analog converter 13 to the upper computer for observation through a serial port. The digital-to-analog converter 13 using the DAC8830 chip supports 16-bit data input, and the fastest output response time is only 1 μs, further improving the rate of feedback control and making the output laser wavelength more stable. When the digital-to-analog converter 13 changes the output voltage with the smallest step, the corresponding change in the current of the distributed feedback semiconductor laser 3 is 0.0015 mA. According to the correspondence between the drive current and the laser wavelength, when the drive current changes by 1 mA, the output laser wavelength changes by about 0.008 nm. Therefore, when the encoded value of the output voltage of the digital-to-analog converter 13 changes with the smallest step, the change amount for the wavelength is 0.012 pm, and the control accuracy far exceeds the frequency stability of the free-running distributed feedback semiconductor laser 3. Therefore, the embodiment of the present invention can achieve the purpose of frequency stabilization of the semiconductor laser.

[0042] In the embodiment of the present invention, by using the transmission peak of the Fabry-Perot etalon as the frequency discrimination curve, an application scenario with a narrow wavelength tuning interval of the laser can be achieved; by designing a method of combining a high-speed comparator circuit and a microcontroller unit to detect the error signal, it is allowed to adjust the locking point of the laser frequency stabilization within a small range by setting the threshold, improving the feedback control rate and the stability of the laser output frequency. The wavelength stability accuracy of the output after stabilization is below the pm level, that is, the output optical frequency is stable at hundreds of kHz, and the frequency stability is better than 10 -9 orders of magnitude, and the system can work continuously and stably for a long time.

[0043] Embodiment 2:

[0044] As Figure 2 shown, the embodiment of the present invention also provides a method for achieving frequency stabilization by using a semiconductor laser frequency stabilization system, including the following steps:

[0045] Step S1: The distributed feedback semiconductor laser 3 serves as the light source of the system. The working temperature of the semiconductor laser is controlled by the high-precision temperature control driving platform 1, and the current control module 2 provides it with the functions of bias current and central wavelength adjustment. Through the control of the high-precision temperature driving platform 1 and the current control module 2, the semiconductor laser 3 emits a laser with a wavelength of λ and a frequency of f;

[0046] Step S2: The output laser beam passes through port 1 of the optical coupler 4 with a splitting ratio of 50:50, dividing the laser beam into two paths. Port 2 of the optical coupler 4 is used as the normal output after frequency stabilization, and the laser at port 3 of the optical coupler 4 enters the electro-optic modulator 5 for frequency modulation. The external arbitrary waveform generator 8 outputs a microwave signal source with an oscillation frequency of Ω and a signal amplitude of V pp at port 1 as the modulation signal, which enters the modulation port of the electro-optic modulator 5 to modulate the laser frequency. At this time, both the light intensity and wavelength of the laser output will have periodic changes with a frequency of Ω. The output port of the electro-optic modulator 5 is connected to the input port of the Fabry-Perot etalon 6 for detecting the deviation between the currently output laser frequency and the given external reference frequency. The center frequency of each transmission peak of the Fabry-Perot etalon 6 can be used as a stable external reference frequency benchmark. When the center frequency of the laser fluctuates away from the reference benchmark frequency, the Fabry-Perot etalon 6 can identify the deviated frequency.

[0047] Step S3: The input end of the photodetector 7 is connected to the output port of the Fabry - Perot etalon 6, converting the received optical signal into an electrical signal and entering the RF signal port of the electrical mixer 9. The output port 2 of the arbitrary waveform generator 8 provides a signal with the same frequency and phase as the local oscillator signal of the electrical mixer, which is input to the local oscillator signal port of the electrical mixer 9. The output port of the electrical mixer 9 is connected to the input port of the low - pass filter 10, filtering out the sum - frequency signal and retaining the DC error signal deviating from the reference frequency.

[0048] Step S4: The output port of the low - pass filter 10 is connected to the input port of the high - speed comparator 11 module. Set the threshold voltage of the high - speed comparator 11. When the voltage of the DC error signal is higher than the threshold voltage, the high - speed comparator 11 outputs a high level; when the voltage of the DC error signal is lower than the threshold voltage, the high - speed comparator outputs a low level. The high - speed comparator 11 module converts the DC error signal with an uncertain amplitude into recognizable high and low level signals, and allows the locking point of frequency stabilization to be adjusted within a small range by setting the threshold.

[0049] Step S5: The output port of the high - speed comparator 11 module is connected to the input port of the micro - control unit 12. The micro - control unit 12 is used to analyze and process the DC error signal, and then judge the position of the laser output wavelength relative to the center reference frequency of the transmission peak of the Fabry - Perot etalon 6. The output end of the micro - control unit 12 is connected to the input end of the digital - to - analog converter 13, controlling the output voltage of the digital - to - analog converter 13, changing the coding value with the smallest step, and starting to adjust the working current of the laser in real - time to achieve the stability of the output wavelength.

[0050] Figure 3 is the transmission spectrum curve and its first - order differential curve of the Fabry - Perot etalon 6. For an ideal Fabry - Perot etalon 6 composed of two parallel reflecting surfaces, the transmission intensity I of its transmission spectrum t relative to the incident light intensity I 0 is defined as:

[0051]

[0052] When the amplitude reflectivities of the two surfaces of the Fabry - Perot etalon 6 are equal, that is, R 1 = R 2 = R, and the intensity reflectivity of each surface is The transmittance of the Fabry - Perot etalon 6 can be simplified as follows:

[0053]

[0054] where n is the refractive index of the etalon, l is the cavity thickness, c is the speed of light, and its first - order differential curve is as follows:

[0055]

[0056] According to Figure 3 the schematic diagram of the transmission spectrum line and its first-order differential curve of the Fabry-Perot etalon 6, it can be seen that in the region near the center wavelength ω 0 of the absorption peak, the first-order differential curve is approximately linear, and when ω > ω 0 , the first-order differential is negative, and when ω < ω 0 , the first-order differential is positive. This characteristic can be used for frequency discrimination.

[0057] Figure 4 Fig. is the schematic diagram of the demodulation signal when the output center wavelength of the laser is at different positions of the transmission peak. In the implementation method of the present invention, the center frequency of the transmission peak of the Fabry-Perot etalon 6 is proposed to be used as the absolute reference for the wavelength. The Fabry-Perot etalon 6 proposed to be used is commonly used as a wavelength calibrator in the C band of optical communication and can have multiple transmission peaks to calibrate the wavelength of the laser. When the reference wavelength of the laser is at different positions of the absorption peak, different signals will be output. When the wavelength reference completely coincides with the bottom of the absorption peak, the wavelength change with a frequency of Ω outputs a signal with a repetition frequency of 2Ω. Since the cosine is completely symmetric with respect to the reference wavelength and the two sides of the absorption peak are also symmetric, the signal with a repetition frequency of 2Ω is completely flat and has no frequency component of Ω. When the baseline deviates from the bottom of the absorption peak, the symmetry of the modulation signal with respect to the bottom of the absorption peak is destroyed, and the output signal with a frequency of 2Ω shows a phenomenon of alternating high and low. At this time, an envelope with a repetition frequency of Ω appears, and further deviation will cause the signal component of the 2Ω frequency to weaken and the signal component of the Ω frequency to strengthen.

[0058] Therefore, the embodiment of the present invention utilizes this characteristic of wavelength modulation to stabilize the wavelength: according to the different directions of the center wavelength deviation, the positive and negative of the obtained feedback DC signal will be different. At this time, the phase of the output signal has two states, differing by 180°, indicating different deviation directions. It should be noted that the actual signal itself has a certain amplitude modulation, so the power at different wavelengths will be different. In this way, when the detected signal is 0, there will be a small deviation between the actual wavelength baseline and the bottom of the absorption peak, but this deviation is fixed and does not affect the locking of the wavelength.

[0059] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A semiconductor laser frequency stabilization system based on a Fabry-Perot etalon, characterized in that: include: High-precision temperature drive platform, current control module, distributed feedback semiconductor laser, optical coupler, electro-optic modulator, Fabry-Perot etalon, photodetector, arbitrary waveform generator, electric mixer, low-pass filter, high-speed comparator, micro control unit, digital-to-analog converter; among them, The output end of the high-precision temperature driving platform is connected to the temperature control end of the distributed feedback semiconductor laser; the output end of the current control module is connected to the current control end of the distributed feedback semiconductor laser; the output end of the distributed feedback semiconductor laser is connected to the input end of the optical coupler; one of the output ends of the optical coupler is connected to the input end of the electro-optic modulator; the other output port of the optical coupler is used as the normal output after the laser frequency is stabilized; one of the output ends of the arbitrary waveform generator is connected to the microwave modulation interface input end of the electro-optic modulator; the output end of the electro-optic modulator is connected to the input end of the Fabry-Perot etalon; The output end of the Fabry-Perot etalon is connected to the input end of the photodetector; the output end of the photodetector is connected to the local oscillator signal input end of the electric mixer; the other output end of the arbitrary waveform generator is connected to the local oscillator signal input end of the electric mixer; the output end of the electric mixer is connected to the input end of the low-pass filter; the output end of the low-pass filter is connected to the input end of the high-speed comparator; the output end of the high-speed comparator is connected to the input end of the microcontroller; the output end of the microcontroller is connected to the input end of the digital-to-analog converter; the output end of the digital-to-analog converter is connected to the control end of the current control module.

2. The semiconductor laser frequency stabilization system based on Fabry-Perot etalon according to claim 1, characterized in that: The target stable frequency of the laser output by the distributed feedback semiconductor laser is consistent with the central frequency of the transmission peak selected by the Fabry-Perot etalon.

3. The semiconductor laser frequency stabilization system based on Fabry-Perot etalon according to claim 2, characterized in that: The optical coupler has a splitting ratio of 50:50; the free spectral range of the Fabry-Perot etalon is 25 GHz, and a narrow wavelength interval tuning of 25 GHz is achieved.

4. A method for implementing a semiconductor laser frequency stabilization method based on a Fabry-Perot etalon by using the semiconductor laser frequency stabilization system based on a Fabry-Perot etalon according to claim 1, characterized in that: include: Laser emission through temperature and drive current controllable distributed feedback semiconductor laser; The laser frequency is modulated, and the transmission spectrum of the Fabry-Perot etalon is used as a reference for the external stable frequency. When the laser frequency deviates from the central reference frequency, the deviated frequency is identified; wherein, the free spectrum range of the Fabry-Perot etalon is 25 GHz, and a narrow wavelength interval tuning of 25 GHz is achieved; A photodetector is used to convert the modulated transmitted optical signal into an electrical signal, and a high-speed comparator is used to detect the error signal caused by the laser frequency deviating from the center frequency of the transmission peak of the Fabry-Perot etalon. A microcontroller unit is used to determine the relationship between the current laser output frequency deviation and the direction of the center frequency of the transmission peak of the Fabry-Perot etalon through the high and low levels obtained from the high-speed comparator circuit, and the digital-to-analog converter is controlled to change the encoding value with the smallest step, fine-tune the output voltage, complete the feedback control of the laser operating current, and realize laser frequency stabilization.

5. The method for stabilizing the frequency of a semiconductor laser based on a Fabry-Perot etalon according to claim 4, characterized in that: The target stable frequency of the laser output by the distributed feedback semiconductor laser is consistent with the central frequency of the transmission peak selected by the Fabry-Perot etalon.

6. A method for implementing a semiconductor laser frequency stabilization method based on a Fabry-Perot etalon by using the semiconductor laser frequency stabilization system based on a Fabry-Perot etalon according to claim 1, characterized in that: include: Step 1: Control the operating temperature of the semiconductor laser through a high-precision temperature drive platform, and provide the semiconductor laser with bias current and center wavelength adjustment functions through a current control module, so that the semiconductor laser emits a laser with a wavelength of λ and a frequency of f; Step 2: The output laser beam passes through an optical coupler to split the laser beam into two paths, one of which is used as the normal output after frequency stabilization, and the other enters the electro-optic modulator for frequency modulation; a microwave signal source is provided as a modulation signal through an external arbitrary waveform generator, which enters the modulation port of the electro-optic modulator for modulation with the laser; The transmission spectrum of the Fabry-Perot etalon is used as a reference for the external stable frequency. When the laser frequency deviates from the central reference frequency, the deviated frequency is identified. Step 3: The photodetector converts the received optical signal into an electrical signal, which enters the radio frequency port of the electrical mixer; A signal having the same frequency and phase as the microwave signal is provided through another output port of the arbitrary waveform generator as the local oscillation signal of the electric mixer and input to the local oscillation signal port of the electric mixer; a low-pass filter is used to filter out the sum frequency signal and retain a DC feedback error signal that deviates from the reference frequency; Step 4: The high-speed comparator module converts the error signal with uncertain amplitude into identifiable high and low level signals, and allows the locking point of the frequency stabilization to be adjusted in a small range by setting the threshold; when the voltage of the DC error signal is higher than the threshold voltage, the high-speed comparator outputs a high level signal; when the voltage of the DC error signal is lower than the threshold voltage, the high-speed comparator outputs a low level signal; Step 5: The microcontroller unit determines the position of the laser output wavelength relative to the central reference frequency based on the DC error signal; the microcontroller unit controls the output voltage of the digital-to-analog converter and adjusts the operating current of the laser in real time to stabilize it at the external reference standard frequency, i.e., the central frequency of the transmission peak of the Fabry-Perot etalon.

7. The method for stabilizing the frequency of a semiconductor laser based on a Fabry-Perot etalon according to claim 6, characterized in that: The target stable frequency of the laser output by the distributed feedback semiconductor laser is consistent with the central frequency of the transmission peak selected by the Fabry-Perot etalon.

8. The method for stabilizing the frequency of a semiconductor laser based on a Fabry-Perot etalon according to claim 7, characterized in that: The optical coupler has a splitting ratio of 50:50; the free spectral range of the Fabry-Perot etalon is 25 GHz, and a narrow wavelength interval tuning of 25 GHz is achieved.

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