Method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system

Abstract

The method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system belongs to the technical fields of semiconductor laser frequency stabilization and precision detection. In order to improve the stability and accuracy of the output center frequency of the laser, the modulation absorption frequency stabilization system is built; the coarse adjustment stage of the laser intensity modulation and the carrier phase delay parameter is executed, and the phase difference between the optical frequency modulation and the optical intensity modulation is obtained; the fine step optimization stage is executed, the laser intensity modulation and the carrier phase delay parameter calculation are completed, the phase corresponding to the maximum peak-to-peak value of the updated optical intensity absorption 1f signal and the phase corresponding to the maximum value of the extreme difference of the optical intensity absorption 2f signal are obtained; the elimination processing is carried out to obtain the optical intensity absorption 1f signal after elimination processing; for the modulation absorption frequency stabilization system, the optical intensity stabilization device is used to eliminate the residual optical intensity fluctuation caused by the current modulation of the tunable semiconductor DFB laser. The stability and accuracy of the output center frequency of the laser are improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor laser frequency stabilization and precision detection technology, specifically relating to a method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system. Background Technology

[0002] Fiber laser sources in the 1.5µm band possess excellent optical advantages, such as low propagation loss in optical fibers and the ability to support long-distance transmission, playing a crucial role in fields such as fiber optic communication, molecular spectroscopy, precision fiber optic sensing, and precision detection. In ultra-precision laser interferometers, considered the most precise instruments in the field of micro-displacement measurement, ensuring excellent stability and accuracy of the laser source's center frequency is one of the three major technical challenges of a complete laser interferometer, directly determining the accuracy of displacement measurement. Commonly used frequency stabilization techniques include molecular / atomic modulation absorption stabilization, optical resonant cavity (Fabry-Perot) stabilization (PDH), and optical frequency comb stabilization. While PDH technology can achieve high-precision frequency stability using a custom-designed optical resonator, the ultra-stable optical resonator is highly dependent on the environment, and its long-term stability is greatly affected by environmental temperature fluctuations. Optical frequency comb stabilization, relying on the ultra-high stability of the optical frequency comb, can achieve a wide range of high-precision frequency locking positions, but its cost is too high and it also has high requirements for environmental stability. In molecular / atomic modulation absorption stabilization, the stability of the gas absorption spectrum is only slightly affected by environmental temperature, mainly related to the gas cell pressure. In practical applications, a sealed gas cell can be used without special control, serving as a frequency reference in complex environments.

[0003] When using molecular / atomic modulation absorption frequency stabilization to stabilize the center frequency of laser output, an angular frequency of is applied to the laser source. , range The modulated signal, after being output from the gas cell, is used to extract the light intensity absorption 1f signal as a frequency discrimination curve through lock-in amplification. Feedback control is then used to lock the laser output center frequency at the zero point of the frequency discrimination curve. Ideally, the zero point of the frequency discrimination curve corresponds to the peak point of the molecular / atomic absorption spectrum. In the new generation of fiber optic microprobe interferometers, the modulation angular frequency... The size determines the maximum measurement speed and optical frequency modulation range of the fiber optic microprobe interferometer. The size of the value determines the size of the measurement range, and increasing it... This will make the carrier phase delay non-negligible, increasing This will increase the impact of laser intensity modulation.

[0004] Existing research indicates that carrier phase delay and laser intensity modulation distort the frequency discrimination curve, causing the lock point to deviate from the frequency corresponding to the peak of the absorption signal, thus affecting the accuracy of the laser output center frequency. In special cases, it can even lead to lock point blanking and frequency stabilization failure. Therefore, it is essential to address the impact of carrier phase delay and laser intensity modulation on molecular / atomic modulation absorption frequency stabilization methods to ensure the stability and accuracy of the laser output center frequency. Summary of the Invention

[0005] The problem this invention aims to solve is to improve the stability and accuracy of the laser output center frequency, and proposes a method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system includes the following steps:

[0008] S1. Construct a modulation absorption frequency stabilization system, which includes a signal synthesis module, a tunable semiconductor DFB laser, an optical isolator, an optical intensity stabilization device, a first fiber coupler, an acetylene gas chamber, a first photodetector, an analog-to-digital converter, a controller, a digital-to-analog converter, a laser driver, a first switch, and a second switch;

[0009] S2. Operate the modulation absorption frequency stabilization system, close the first switch and open the second switch, perform the coarse adjustment stage of laser intensity modulation and carrier phase delay parameters, and statistically analyze the phase corresponding to the maximum peak-to-peak value of the 1f light intensity absorption signal. The phase corresponding to the maximum value of the extreme difference between the light intensity absorption 2f signal and the extreme value of the light intensity absorption signal. Then, the phase difference between optical frequency modulation and optical intensity modulation is obtained through difference calculation. ;

[0010] S3. Obtained in step S2 and Based on this, a fine-step optimization stage is performed to complete the calculation of laser intensity modulation and carrier phase delay parameters, and obtain the phase corresponding to the maximum peak-to-peak value of the updated light intensity absorption 1f signal and the phase corresponding to the maximum extreme difference of the light intensity absorption 2f signal.

[0011] S4. The laser intensity modulation and carrier phase delay parameters obtained in step S3 are eliminated using the controller to obtain the eliminated light intensity absorption 1f signal;

[0012] S5. For the modulation absorption frequency stabilization system, the first switch is opened and the second switch is closed. The light intensity stabilization device is used to eliminate the residual light intensity fluctuations caused by current modulation of the tunable semiconductor DFB laser. The controller controls the digital-to-analog converter to apply the obtained analog control signal to the laser driver. The driving current and temperature of the tunable semiconductor DFB laser are controlled to adjust the laser output frequency of the tunable semiconductor DFB laser in real time. This completes the method of calculating and eliminating laser intensity modulation and carrier phase delay in the modulation absorption frequency stabilization system.

[0013] Furthermore, in step S1, the signal synthesis module of the modulation absorption frequency stabilization system is connected to a tunable semiconductor DFB laser, the tunable semiconductor DFB laser is connected to an optical isolator, the optical isolator is connected to a first switch and a light intensity stabilization device, the first switch is connected to a first fiber coupler, the light intensity stabilization device is connected to the first fiber coupler through a second switch, the first fiber coupler is sequentially connected to an acetylene gas chamber, a first photodetector, an analog-to-digital converter, a controller, a digital-to-analog converter, and a laser driver, and the laser driver is connected to the tunable semiconductor DFB laser.

[0014] Furthermore, in step S1, the light intensity stabilization device includes an SOA optical amplifier, which is sequentially connected to a second fiber coupler, a second photodetector, a comparator, a bandpass filter, a PI control module, and an SOA optical amplifier driver. The SOA optical amplifier driver is connected to the SOA optical amplifier. The light intensity stabilization device controls the intensity of the laser power emitted from the second fiber coupler to the first fiber coupler by real-time feedback of the current value input to the SOA optical amplifier.

[0015] Furthermore, the controller in step S1 includes a cosine signal generation module COS, which is connected to a first multiplier, a second multiplier, and a distortion correction module. The second multiplier is connected to a second low-pass filter and the first multiplier. The distortion correction module is connected to a second low-pass filter, a first low-pass filter, and an error calculation module. The first multiplier is connected to a first low-pass filter, an error calculation module, and a PI control module in sequence.

[0016] Furthermore, the specific implementation method of step S2 includes the following steps:

[0017] S2.1. Run the modulation absorption frequency stabilization system, close the first switch and open the second switch. The laser driver performs a triangular active temperature scan or current scan on the tunable semiconductor DFB laser to control the laser output frequency variation range of the tunable semiconductor DFB laser to cover the complete acetylene absorption peak. Then, after passing through the first photodetector and analog-to-digital converter, the frequency discrimination absorption digital electrical signal is obtained and input to the controller.

[0018] S2.2. The first cosine signal generated by the cosine signal generation module COS in the controller. The frequency-discriminating absorption digital electrical signal obtained in step S2.1 is mixed in the first multiplier, and after the high-frequency components are filtered out by the first low-pass filter, the light intensity absorption 1f signal is obtained. Angular frequency, For time, It is a variable phase;

[0019] The second cosine signal generated by the cosine signal generation module COS The frequency-discriminating absorption digital electrical signal obtained in step S2.1 is mixed with the frequency-discriminating absorption digital electrical signal in the second multiplier, and the light intensity absorption 2f signal is obtained after the high frequency components are filtered out by the second low-pass filter.

[0020] S2.3. Distortion correction module controls variable phase Simultaneously, discrete step scanning is performed within the range of 0° to 360° with a step size of 18°, and the peak value of the 1f signal absorbed by the light intensity is measured at each phase point. Valley value Perform statistical analysis to identify and record the peak-to-peak value of the light intensity absorption signal at 1f. The maximum value is obtained by determining the phase corresponding to the maximum peak-to-peak value of the light intensity absorption 1f signal. denoted as carrier phase delay ;

[0021] The extreme point to the left of the maximum amplitude point of the 2f signal at each phase point. Extreme points on the right side Statistical analysis was performed to identify and record the peak-to-peak value difference between the extreme points on either side of the maximum amplitude point at the center of the 2f light intensity absorption signal. The maximum value of the extreme difference of the light intensity absorption 2f signal corresponds to the phase. Through difference operation Seek .

[0022] Furthermore, the specific implementation method of step S3 is as follows: Based on the coarse adjustment... and Based on this, a refined, step-by-step optimization phase is implemented, focusing on... and The variable phase φ in the middle is simultaneously with and Centered on the signal, each phase is stepped at intervals of +9° and -9°, and at each phase point, the peak-to-peak value of the 1f signal of new light intensity absorption is identified and recorded. The difference between the peak-to-peak values ​​and the extreme values ​​between the extreme points on either side of the maximum amplitude point of the 2f signal center. Maximum value, update and The laser intensity modulation and carrier phase delay parameters are calculated.

[0023] Furthermore, the specific implementation method of step S4 includes the following steps:

[0024] S4.1. Order Variable phase in This eliminates the influence of laser intensity modulation and carrier phase delay, which cause the center point of the light intensity absorption 1f signal to not correspond to the gas molecule absorption peak point in the frequency domain;

[0025] S4.2. The error calculation module receives the light intensity absorption 1f signal and divides it by... The effect of laser intensity modulation on the slope of the linear region of the 1f light intensity absorption signal is reduced, and the slope of the linear region of the 1f light intensity absorption signal is restored, thereby improving the system control sensitivity. The laser intensity modulation and carrier phase delay parameters are eliminated, and the 1f light intensity absorption signal after elimination is obtained.

[0026] Furthermore, in step S5, a portion of the emitted light from the second fiber coupler in the light intensity stabilization device enters the first fiber coupler, while the other portion of the emitted light is converted into an electrical signal by the second photodetector. This signal is compared with a set amplitude in the comparator to calculate the light intensity deviation as an error feedback signal. Then, it is filtered by a bandpass filter to remove low-frequency and high-frequency noise. Finally, the signal amplitude is adjusted by the PI control module to control the SOA optical amplifier driver to adjust the gain ratio of the SOA optical amplifier, thereby achieving intensity control of the laser power emitted from the second fiber coupler to the first fiber coupler.

[0027] Furthermore, the set amplitude in S5 is determined based on the light intensity required by the subsequent optical path and the light intensity distribution ratio of the first fiber coupler.

[0028] The beneficial effects of this invention are:

[0029] This invention discloses a method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system. Addressing the problems of frequency discrimination curve distortion, inconsistent frequency stabilization points, or even blanking failure caused by laser intensity modulation and carrier phase delay in high-amplitude modulation absorption frequency stabilization systems, this method utilizes the extracted first and second harmonics of the frequency discrimination absorption signal to calculate the relevant parameters of laser intensity modulation and carrier phase delay. This adds an initial phase to the demodulated signal, correcting the frequency discrimination curve and achieving a precise mapping between the zero point of the frequency discrimination signal and the frequency corresponding to the absorption peak point of gas molecules. This provides a reliable basis for locking the frequency of the modulation absorption frequency stabilization system. By eliminating the influence of laser intensity modulation and carrier phase delay on the frequency discrimination curve, the stability and accuracy of the laser output center frequency are improved. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating a method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system, as described in this invention.

[0031] Figure 2 This is a schematic diagram of the modulation absorption frequency stabilization system of the present invention;

[0032] Figure 3 This is a schematic diagram of the controller structure of the present invention;

[0033] Figure 4 This is a schematic diagram of the light intensity stabilizing device of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described specific embodiments are merely a part of the embodiments of the invention, and not all of them. The components of the specific embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations, and the invention may also have other embodiments.

[0035] Therefore, the following detailed description of specific embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected specific embodiments of the invention. All other specific embodiments obtained by those skilled in the art based on these specific embodiments without inventive effort are within the scope of protection of this invention.

[0036] To further understand the invention's content, features, and effects, the following specific embodiments are provided, along with accompanying drawings. Figure 1 - Appendix Figure 4Detailed explanation is as follows:

[0037] Example 1:

[0038] A method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system includes the following steps:

[0039] S1. Construct a modulation absorption frequency stabilization system, which includes a signal synthesis module 1, a tunable semiconductor DFB laser 2, an optical isolator 3, a light intensity stabilization device 4, a first fiber coupler 5, an acetylene gas chamber 6, a first photodetector 7, an analog-to-digital converter 8, a controller 9, a digital-to-analog converter 10, a laser driver 11, a first switch A, and a second switch B.

[0040] Furthermore, in step S1, the signal synthesis module 1 of the modulation absorption frequency stabilization system is connected to the tunable semiconductor DFB laser 2, the tunable semiconductor DFB laser 2 is connected to the optical isolator 3, the optical isolator 3 is connected to the first switch A and the light intensity stabilization device 4 respectively, the first switch A is connected to the first fiber coupler 5, the light intensity stabilization device 4 is connected to the first fiber coupler 5 through the second switch B, the first fiber coupler 5 is connected in sequence to the acetylene gas chamber 6, the first photodetector 7, the analog-to-digital converter 8, the controller 9, the digital-to-analog converter 10 and the laser driver 11, and the laser driver 11 is connected to the tunable semiconductor DFB laser 2.

[0041] Furthermore, in step S1, the light intensity stabilization device 4 includes an SOA optical amplifier 20, which is sequentially connected to a second fiber coupler 21, a second photodetector 22, a comparator 23, a bandpass filter 24, a PI control module 25, and an SOA optical amplifier driver 26. The SOA optical amplifier driver 26 is connected to the SOA optical amplifier 20. The light intensity stabilization device 4 controls the intensity of the laser power emitted from the second fiber coupler 21 to the first fiber coupler 5 by real-time feedback of the current value input to the SOA optical amplifier 20.

[0042] Furthermore, the controller 9 in step S1 includes a cosine signal generation module COS13, which is connected to a first multiplier 12, a second multiplier 14, and a distortion correction module 16. The second multiplier 14 is connected to a second low-pass filter 15 and the first multiplier 12. The distortion correction module 16 is connected to the second low-pass filter 15, the first low-pass filter 17, and an error calculation module 18. The first multiplier 12 is connected to the first low-pass filter 17, the error calculation module 18, and the PI control module 19 in sequence.

[0043] Furthermore, in step S1, the signal synthesis module 1 applies a signal to the tunable semiconductor DFB laser 2. Changing frequency modulation signal, The output frequency of the tunable semiconductor DFB laser 2, generated by the cosine signal generation module COS13, can be written as: The analog-to-digital converter 8 performs digital sampling and then discriminates and absorbs the digital electrical signal. , Performing a Taylor expansion at frequency v, we obtain:

[0044]

[0045] in, For the center frequency of the laser output of the tunable semiconductor DFB laser 2, Where m is the modulation frequency range, and m is the laser intensity modulation coefficient. The phase difference between optical frequency modulation and optical intensity modulation. Carrier phase delay (CPD), The angular frequency is the frequency corresponding to the modulation signal output by signal synthesis module 1.

[0046] S2. Operate the modulation absorption frequency stabilization system, close the first switch A and open the second switch B, perform the coarse adjustment stage of laser intensity modulation and carrier phase delay parameters, and statistically analyze the phase corresponding to the maximum peak-to-peak value of the light intensity absorption 1f signal. The phase corresponding to the maximum value of the extreme difference between the light intensity absorption 2f signal and the extreme value of the light intensity absorption signal. Then, the phase difference between optical frequency modulation and optical intensity modulation is obtained through difference calculation. ;

[0047] Furthermore, the specific implementation method of step S2 includes the following steps:

[0048] S2.1. Run the modulation absorption frequency stabilization system, close the first switch A and open the second switch B. The laser driver 11 performs a triangular active temperature scan or current scan on the tunable semiconductor DFB laser 2 to control the laser output frequency variation range of the tunable semiconductor DFB laser 2 to cover the complete acetylene absorption peak. Then, after passing through the first photodetector 7 and the analog-to-digital converter 8, the frequency discrimination absorption digital electrical signal is obtained and input to the controller 9.

[0049] S2.2. The first cosine signal generated by the cosine signal generation module COS13 in controller 9. The frequency-discriminating absorption digital electrical signal obtained in step S2.1 is mixed in the first multiplier 12, and after the high-frequency components are filtered out by the first low-pass filter 17, the light intensity absorption 1f signal is obtained. Angular frequency, For time, It is a variable phase;

[0050] The second cosine signal generated by the cosine signal generation module COS13 The frequency-discriminating absorption digital electrical signal obtained in step S2.1 is mixed with the frequency-discriminating absorption digital electrical signal in the second multiplier 14, and the light intensity absorption 2f signal is obtained after the high frequency components are filtered out by the second low-pass filter 15.

[0051] Furthermore, after filtering out high-frequency components by the first low-pass filter 17, the light intensity absorption signal 1f is obtained as follows:

[0052] ;

[0053] After the high-frequency components are filtered out by the second low-pass filter 15, the light intensity absorption signal 2f is obtained as follows:

[0054]

[0055] in, This is a function representing the acetylene transmission curve. The normalized absorption rate at the center of the transmission spectral line. The acetylene transmission spectrum is at half maximum and half width at half maximum. The laser output center frequency of the tunable semiconductor DFB laser 2, In order to pinpoint the frequency corresponding to the acetylene absorption peak;

[0056] H1(v) and H4(v) are based on The odd functions centered at H2(v) and H3(v) are based on... an even function centered at;

[0057]

[0058]

[0059]

[0060]

[0061] and Having the same maximum point and the same minimum point ; .

[0062] S2.3. Distortion correction module (16) controls variable phase Simultaneously, discrete step scanning is performed within the range of 0° to 360° with a step size of 18°, and the peak value of the 1f signal absorbed by the light intensity is measured at each phase point. Valley value Perform statistical analysis to identify and record the peak-to-peak value of the light intensity absorption signal at 1f. The maximum value is obtained by determining the phase corresponding to the maximum peak-to-peak value of the light intensity absorption 1f signal. denoted as carrier phase delay ;

[0063] The extreme point to the left of the maximum amplitude point of the 2f signal at each phase point. Extreme points on the right side Statistical analysis was performed to identify and record the peak-to-peak value difference between the extreme points on either side of the maximum amplitude point at the center of the 2f light intensity absorption signal. The maximum value of the extreme difference of the light intensity absorption 2f signal corresponds to the phase. Through difference operation Seek .

[0064] Furthermore, each phase point corresponds to the peak-to-peak value of the 1f signal absorbed by the light intensity. for:

[0065] ;

[0066] The extreme points on both sides of the maximum amplitude point at the center of the 2f signal of light intensity absorption, the peak-to-peak difference for:

[0067] .

[0068] S3. Obtained in step S2 and Based on this, a fine-step optimization stage is performed to complete the calculation of laser intensity modulation and carrier phase delay parameters, and obtain the phase corresponding to the maximum peak-to-peak value of the updated light intensity absorption 1f signal and the phase corresponding to the maximum extreme difference of the light intensity absorption 2f signal.

[0069] Furthermore, the specific implementation method of step S3 is as follows: Based on the coarse adjustment... and Based on this, a refined, step-by-step optimization phase is implemented, focusing on... and The variable phase φ in the middle is simultaneously with and Centered on the signal, each phase is stepped at intervals of +9° and -9°, and at each phase point, the peak-to-peak value of the 1f signal of new light intensity absorption is identified and recorded. The difference between the peak-to-peak values ​​and the extreme values ​​between the extreme points on either side of the maximum amplitude point of the 2f signal center. Maximum value, update and The laser intensity modulation and carrier phase delay parameters are calculated.

[0070] S4. The laser intensity modulation and carrier phase delay parameters obtained in step S3 are eliminated using the controller 9 to obtain the eliminated light intensity absorption 1f signal;

[0071] Furthermore, the specific implementation method of step S4 includes the following steps:

[0072] S4.1. Order Variable phase in This eliminates the influence of laser intensity modulation and carrier phase delay, which cause the center point of the light intensity absorption 1f signal to not correspond to the gas molecule absorption peak point in the frequency domain;

[0073] S4.2. Error calculation module (18) receives the light intensity absorption 1f signal and divides it by... The effect of laser intensity modulation on the slope of the linear region of the 1f light intensity absorption signal is reduced, and the slope of the linear region of the 1f light intensity absorption signal is restored, thereby improving the system control sensitivity. The laser intensity modulation and carrier phase delay parameters are eliminated, and the 1f light intensity absorption signal after elimination is obtained.

[0074] Furthermore, the center point of the light intensity absorption 1f signal is the light intensity absorption 1f signal. At the corresponding frequency point, the light intensity absorption 1f signal after eliminating the effects of laser intensity modulation and carrier phase delay is expressed as: .

[0075] S5. For the modulation absorption frequency stabilization system, the first switch A is opened and the second switch B is closed. The light intensity stabilization device 4 is used to eliminate the residual light intensity fluctuation caused by the current modulation of the tunable semiconductor DFB laser 2. The controller 9 controls the digital-to-analog converter 10 to apply the obtained analog control signal to the laser driver 11. The driving current and temperature of the tunable semiconductor DFB laser 2 are controlled to adjust the laser output frequency of the tunable semiconductor DFB laser 2 in real time. This completes the method of calculating and eliminating laser intensity modulation and carrier phase delay in the modulation absorption frequency stabilization system.

[0076] Furthermore, in step S5, a portion of the emitted light from the second fiber coupler 21 in the light intensity stabilizing device 4 enters the first fiber coupler 5, while the other portion of the emitted light is converted into an electrical signal by the second photodetector 22. This signal is then compared with a set amplitude in the comparator 23 to calculate the light intensity deviation as an error feedback signal. The signal is then filtered by the bandpass filter 24 to remove low-frequency and high-frequency noise. Finally, the signal amplitude is adjusted by the PI control module 25 to control the SOA optical amplifier driver 26 to adjust the gain ratio of the SOA optical amplifier (20), thereby achieving intensity control of the laser power emitted from the second fiber coupler 21 to the first fiber coupler 5.

[0077] Furthermore, the set amplitude in step S5 is determined based on the light intensity required by the subsequent optical path and the light intensity distribution ratio of the first fiber coupler 5.

[0078] Furthermore, the working principle of the light intensity stabilization device is to achieve the effect of stabilizing the laser light intensity output to the first coupler 5 by adjusting the current value of the input SOA optical amplifier 20 through real-time feedback. Specifically: In the light intensity stabilization device, part of the light emitted from the second coupler 21 enters the first coupler 15, and the other part is converted into an electrical signal by the second photodetector 22. This signal is compared with a set amplitude (determined by the light intensity required by the subsequent optical path and the light intensity distribution ratio of the coupler 1) in the comparator 23. The calculated light intensity deviation is used as an error feedback signal. Then, it is filtered by the bandpass filter 24 to remove low-frequency and high-frequency noise. Finally, the PI control module 25 adjusts the signal amplitude to control the SOA optical amplifier driver 26, thereby adjusting the gain ratio of the SOA optical amplifier 20, thus achieving intensity control of the laser power emitted from the second coupler 21 to the first coupler 5.

[0079] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0080] Although this application has been described above with reference to specific embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of this application. In particular, as long as there is no structural conflict, the features in the specific embodiments disclosed in this application can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, this application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system, characterized in that, Includes the following steps: S1. Construct a modulation absorption frequency stabilization system, which includes a signal synthesis module (1), a tunable semiconductor DFB laser (2), an optical isolator (3), a light intensity stabilization device (4), a first fiber coupler (5), an acetylene gas chamber (6), a first photodetector (7), an analog-to-digital converter (8), a controller (9), a digital-to-analog converter (10), a laser driver (11), a first switch (A), and a second switch (B). In step S1, the signal synthesis module (1) of the modulation absorption frequency stabilization system is connected to the tunable semiconductor DFB laser (2), the tunable semiconductor DFB laser (2) is connected to the optical isolator (3), the optical isolator (3) is connected to the first switch (A) and the light intensity stabilization device (4) respectively, the first switch (A) is connected to the first fiber coupler (5), the light intensity stabilization device (4) is connected to the first fiber coupler (5) through the second switch (B), the first fiber coupler (5) is connected to the acetylene gas chamber (6), the acetylene gas chamber (6) is connected to the first photodetector (7), the first photodetector (7) is connected to the analog-to-digital converter (8), the analog-to-digital converter (8) is connected to the controller (9), the controller (9) is connected to the digital-to-analog converter (10), the digital-to-analog converter (10) is connected to the laser driver (11), and the laser driver (11) is connected to the tunable semiconductor DFB laser (2). S2. Run the modulation absorption frequency stabilization system, close the first switch (A) and open the second switch (B), perform the coarse adjustment stage of laser intensity modulation and carrier phase delay parameters, and statistically analyze the phase corresponding to the maximum peak-to-peak value of the light intensity absorption 1f signal. The phase corresponding to the maximum value of the extreme difference between the light intensity absorption 2f signal and the extreme value of the light intensity absorption signal. Then, the phase difference between optical frequency modulation and optical intensity modulation is obtained through difference calculation. ; S3. Obtained in step S2 and Based on this, a fine-step optimization stage is performed to complete the calculation of laser intensity modulation and carrier phase delay parameters, and obtain the phase corresponding to the maximum peak-to-peak value of the updated light intensity absorption 1f signal and the phase corresponding to the maximum extreme difference of the light intensity absorption 2f signal. S4. The laser intensity modulation and carrier phase delay parameters obtained in step S3 are eliminated using the controller (9) to obtain the light intensity absorption 1f signal after elimination. S5. For the modulation absorption frequency stabilization system, disconnect the first switch (A) and close the second switch (B). Use the light intensity stabilization device (4) to eliminate the residual light intensity fluctuation caused by the current modulation of the tunable semiconductor DFB laser (2). Use the controller (9) to control the digital-to-analog converter (10) to apply the obtained analog control signal to the laser driver (11). Control the driving current and temperature of the tunable semiconductor DFB laser (2) to adjust the laser output frequency of the tunable semiconductor DFB laser (2) in real time. Complete the method of calculating and eliminating laser intensity modulation and carrier phase delay in the modulation absorption frequency stabilization system.

2. The method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system according to claim 1, characterized in that, In step S1, the light intensity stabilization device (4) includes an SOA optical amplifier (20), which is connected to a second fiber coupler (21). The second fiber coupler (21) is connected to a second photodetector (22), which is connected to a comparator (23). The comparator (23) is connected to a bandpass filter (24), which is connected to a PI control module (25). The PI control module (25) is connected to an SOA optical amplifier driver (26), which is connected to the SOA optical amplifier (20). The light intensity stabilization device (4) controls the intensity of the laser power emitted from the second fiber coupler (21) to the first fiber coupler (5) by real-time feedback of the current value input to the SOA optical amplifier (20).

3. The method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system according to claim 2, characterized in that, The controller (9) in step S1 includes a cosine signal generation module COS (13), which is connected to a first multiplier (12), a second multiplier (14) and a distortion correction module (16). The second multiplier (14) is connected to a second low-pass filter (15) and a first multiplier (12). The distortion correction module (16) is connected to a second low-pass filter (15), a first low-pass filter (17) and an error calculation module (18). The first multiplier (12) is connected to the first low-pass filter (17). The first low-pass filter (17) is connected to the error calculation module (18). The error calculation module (18) is connected to the PI control module (19).

4. The method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system according to claim 3, characterized in that, The specific implementation method of step S2 includes the following steps: S2.

1. Run the modulation absorption frequency stabilization system, close the first switch (A) and open the second switch (B). The laser driver (11) performs a triangular active temperature scan or current scan on the tunable semiconductor DFB laser (2) to control the laser output frequency change range of the tunable semiconductor DFB laser (2) to cover the complete acetylene absorption peak. Then, after passing through the first photodetector (7) and the analog-to-digital converter (8), the frequency discrimination absorption digital electrical signal is obtained and input into the controller (9). S2.

2. The first cosine signal generated by the cosine signal generation module COS(13) in the controller (9) The frequency-discriminating absorption digital electrical signal obtained in step S2.1 is mixed in the first multiplier (12), and after the high-frequency components are filtered out by the first low-pass filter (17), the light intensity absorption 1f signal is obtained. Angular frequency, For time, It is a variable phase; The second cosine signal generated by the cosine signal generation module COS(13) The frequency discrimination absorption digital electrical signal obtained in step S2.1 is mixed with the frequency discrimination absorption digital electrical signal in the second multiplier (14), and the light intensity absorption 2f signal is obtained after the high frequency component is filtered out by the second low-pass filter (15). S2.

3. Distortion correction module (16) controls variable phase Simultaneously, discrete step scanning is performed within the range of 0° to 360° with a step size of 18°, and the peak value of the 1f signal absorbed by the light intensity is measured at each phase point. Valley value Perform statistical analysis to identify and record the peak-to-peak value of the light intensity absorption signal at 1f. The maximum value is obtained by determining the phase corresponding to the maximum peak-to-peak value of the light intensity absorption 1f signal. denoted as carrier phase delay ; The extreme point to the left of the maximum amplitude point of the 2f signal at each phase point. Extreme points on the right side Statistical analysis was performed to identify and record the peak-to-peak value difference between the extreme points on either side of the maximum amplitude point at the center of the 2f light intensity absorption signal. The maximum value of the extreme difference of the light intensity absorption 2f signal corresponds to the phase. Through difference operation Seek .

5. The method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system according to claim 4, characterized in that, The specific implementation method of step S3 is as follows: (The text abruptly ends here, likely due to an incomplete sentence or a formatting error.) and Based on this, a refined, step-by-step optimization phase is implemented, focusing on... and The variable phase φ in the middle is simultaneously with and Centered on the signal, each phase is stepped at intervals of +9° and -9°, and at each phase point, the peak-to-peak value of the 1f signal of new light intensity absorption is identified and recorded. The difference between the extreme points on either side of the maximum amplitude of the 2f signal center and the peak-to-peak value. Maximum value, update and The laser intensity modulation and carrier phase delay parameters are calculated.

6. The method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system according to claim 5, characterized in that, The specific implementation method of step S4 includes the following steps: S4.

1. Order Variable phase in This eliminates the influence of laser intensity modulation and carrier phase delay, which cause the center point of the light intensity absorption 1f signal to not correspond to the gas molecule absorption peak point in the frequency domain; S4.

2. Error calculation module (18) receives the light intensity absorption 1f signal and divides it by... The effect of laser intensity modulation on the slope of the linear region of the 1f light intensity absorption signal is reduced, and the slope of the linear region of the 1f light intensity absorption signal is restored, thereby improving the system control sensitivity. The laser intensity modulation and carrier phase delay parameters are eliminated, and the 1f light intensity absorption signal after elimination is obtained.

7. The method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system according to claim 6, characterized in that, In step S5, part of the emitted light from the second fiber coupler (21) in the light intensity stabilization device (4) enters the first fiber coupler (5), and the other part of the emitted light is converted into an electrical signal by the second photodetector (22). It is compared with the set amplitude in the comparator (23) and the light intensity deviation is calculated as an error feedback signal. Then, it is filtered by the bandpass filter (24) to remove the influence of low-frequency and high-frequency noise. Then, the signal amplitude is adjusted by the PI control module (25) to control the SOA optical amplifier driver (26) to adjust the gain ratio of the SOA optical amplifier (20), thereby achieving intensity control of the laser power emitted from the second fiber coupler (21) to the first fiber coupler (5).

8. The method for calculating and eliminating laser intensity modulation and carrier phase delay in a modulation absorption frequency stabilization system according to claim 7, characterized in that, The set amplitude in step S5 is determined based on the light intensity required by the subsequent optical path and the light intensity distribution ratio of the first fiber coupler (5).

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