Automatic frequency locking method and device based on laser modulation spectrum and saturation spectrum

Abstract

The present application relates to the field of optical communication, and provides an automatic frequency locking method and device based on laser modulation spectrum and saturation spectrum, which uses saturation absorption spectrum to provide frequency reference, demodulates the modulation spectrum to obtain modulation spectrum, and uses the midpoint of the wave peak and wave trough in the modulation spectrum as the locking target. A multi-stage coarse adjustment level with gradually decreasing scanning amplitude is configured, and the frequency deviation is gradually converged through multiple rounds of iteration; in each round of iteration, the modulation spectrum signal is collected, the wave peak and wave trough positions are identified and the deviation from the reference sampling point is calculated, and the current is updated accordingly until the deviation converges and the next coarse adjustment level is entered. After the last stage converges, it is switched to the incremental PID mode to complete fine locking. After locking, the frequency deviation is continuously monitored, and when the lock is lost, the current is automatically backed up and the iteration is restarted until it is restored. The present application designs a strategy combining step-by-step approximation and PID fine adjustment according to the characteristics of the modulation spectrum signal, which is suitable for different lasers and environmental conditions, can automatically recover without manual intervention after losing lock, and improves the reliability of the system.

Description

Technical Field

[0001] This invention belongs to the field of optical communication, and more specifically, relates to an automatic frequency locking method and apparatus based on the modulation spectrum and saturation spectrum of a laser. Background Technology

[0002] Laser frequency stability is a core performance indicator in fields such as precision spectroscopy, quantum metrology, quantum computing, and coherent optical communication. Existing laser modulation spectrum frequency locking methods and saturation spectrum frequency locking methods have the following shortcomings: On the one hand, the algorithm parameters used are mostly statically configured, lacking the ability to adapt to individual differences in lasers and environmental changes, making it difficult to continuously guarantee frequency locking accuracy; on the other hand, after encountering environmental disturbances (such as vibration or electromagnetic interference) that cause locking failure, existing methods cannot autonomously recover the locking and must rely on manual intervention, which seriously restricts the system's operational reliability and intelligence level.

[0003] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0004] The problem this invention aims to solve is how to improve the adaptability of the frequency locking method to different environmental conditions and different laser models, and how to achieve automatic relocking after frequency loss, thereby improving the reliability of relocking.

[0005] In a first aspect, an automatic frequency locking method based on laser modulation spectrum and saturation spectrum is provided, comprising: providing a laser to be sampled and monitoring the frequency of the laser; Set the sampling range and the reference sampling point in the sampling range, configure a multi-level coarse adjustment level with progressively increasing debugging accuracy, and set the initial current as the output current; Multiple rounds of locking iterations are performed. Each round of locking iteration includes: applying the output current and the scanning amplitude corresponding to the current coarse adjustment level to the laser, obtaining the modulation spectrum signal of the laser, which is obtained by frequency modulation and demodulation of the saturated absorption spectrum, and sampling within the sampling range of the modulation spectrum signal to obtain multiple sampling points, identifying the peak and trough positions in the modulation spectrum signal based on the sampling points, calculating the deviation between the peak and trough positions and the reference sampling points, and updating the output current of the next round of locking iteration based on the deviation and the update gain corresponding to the current coarse adjustment level. Determine whether to enter the next coarse adjustment level based on the preset level switching conditions: if the level switching conditions are met and there is a next coarse adjustment level, switch to the next coarse adjustment level and continue to execute the next round of locking iteration; if it is in the last level of coarse adjustment and the fine locking conditions are met, switch to incremental PID mode for fine locking. After fine locking is completed, the frequency deviation of the laser is obtained. If it is determined that the lock has been lost, a safe current backoff is performed, and multiple rounds of locking iterations are restarted until the frequency is locked again.

[0006] Preferably, identifying the peak and trough positions in the modulation spectrum signal based on sampling points specifically includes: The sampling points are filtered to obtain the filtered sampling points; Calculate the first and second derivatives of the filtered sampling points; When the absolute value of the first derivative is less than the first derivative threshold and the second derivative is less than the second derivative threshold, the location of the sampling point is determined to be the peak position. When the absolute value of the first derivative is less than the first derivative threshold and the second derivative is greater than the second derivative threshold, the location of the sampling point is determined to be a trough position.

[0007] Preferably, the deviation between the peak and trough positions and the reference sampling point is calculated, and the output current for the next locking iteration is updated based on the deviation and the update gain corresponding to the current coarse adjustment level. Specifically, this includes: Calculate the peak difference between the peak position and the reference sampling point, and calculate the trough difference between the trough position and the reference sampling point; The comprehensive frequency error is obtained based on the peak difference and trough difference. The current adjustment value is obtained based on the comprehensive frequency error and the update gain corresponding to the current coarse adjustment level; Add the current adjustment value to the output current used in this round of locking iteration to obtain the output current required for the next round of locking iteration.

[0008] Preferably, the current adjustment value is obtained based on the comprehensive frequency error and the update gain corresponding to the current coarse adjustment level, specifically including: The formula for calculating the current adjustment value is: ; in, This is the current adjustment value. To update the gain, To account for the overall frequency error, For single adjustment of the upper limit of current, To limit the current range.

[0009] Preferably, the decision to enter the next coarse adjustment level is based on preset level switching conditions: if the level switching conditions are met and a next coarse adjustment level exists, then the process switches to the next coarse adjustment level and continues with the next round of locking iterations, specifically including: The convergence value of the current round of locking iteration is obtained based on the absolute value of the comprehensive frequency error; Compare the convergence value with the convergence threshold of the corresponding coarse adjustment level; If the convergence value of the consecutive preset number of rounds is less than the convergence threshold of the corresponding coarse adjustment level, the level switching condition is met, and the configuration of the next coarse adjustment level is adopted for the next round of locking iteration. Otherwise, the level switching condition is not met, and the coarse adjustment level remains unchanged in the next round of locking iteration.

[0010] Preferred criteria for determining loss of lock include: Obtain the frequency mean; the difference between the frequency mean and the frequency lock value is the frequency deviation. The frequency deviation is compared with the deviation threshold. If the frequency deviation is greater than the deviation threshold, it is determined that an instantaneous over-limit has occurred. If instantaneous exceedances occur in all N1 consecutive monitoring cycles, the last monitoring cycle in which an instantaneous exceedance occurs is taken as the current monitoring cycle. The first M monitoring cycles, including the current monitoring cycle, are determined. These first M monitoring cycles are then divided into the first M1 monitoring cycles including the current monitoring cycle and the first M2 monitoring cycles far from the current monitoring cycle. If the average frequency deviation of the first M1 monitoring cycles deteriorates by more than a preset percentage compared to the average frequency deviation of the first M2 monitoring cycles, then a loss of lockout is determined. Here, N1 is greater than or equal to 2, and both M1 and M2 are greater than or equal to 1.

[0011] Preferably, if it is at the last coarse adjustment level and the fine-tuning conditions are met, then switch to incremental PID mode for fine-tuning, specifically including: The output current and the scanning amplitude corresponding to the incremental PID mode are applied to the laser, and multiple sampling points are obtained by sampling within the sampling range. The peak and trough positions in the modulation spectrum signal are identified based on the sampling points. The peak difference between the peak position and the reference sampling point is calculated, and the trough difference between the trough position and the reference sampling point is calculated. The comprehensive frequency error is obtained based on the peak difference and trough difference. The current adjustment value is obtained based on the comprehensive frequency error and PID locking algorithm; The output current is adjusted according to the current adjustment value to achieve precise locking of the laser frequency.

[0012] Preferably, if a loss of lock is determined, a safe current backoff is performed, restarting multiple rounds of locking iterations until the frequency is relocked, specifically including: When a lock loss is detected, the configuration parameters before the lock loss are recorded. Reduce the output current to a preset safe ratio of the operating current; Starting from the lowest coarse adjustment level, multiple rounds of locking iterations are re-executed, and when the fine locking conditions are met, the incremental PID mode is switched to perform fine locking. Restore the laser parameters to the configuration parameters before the loss of lock.

[0013] In a second aspect, an automatic frequency locking device based on laser modulation spectrum and saturation spectrum is provided, comprising at least one processor and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the processor for performing an automatic frequency locking method based on laser modulation spectrum and saturation spectrum.

[0014] Thirdly, the present invention also provides a non-volatile computer storage medium storing computer-executable instructions that, when executed by one or more processors, cause the processors to execute the method of the first aspect.

[0015] Fourthly, a chip is provided, comprising: a processor and an interface for calling and running a computer program stored in memory, performing the method as described in the first aspect.

[0016] Fifthly, a computer program product containing instructions is provided that, when executed on a computer or processor, causes the computer or processor to perform the method as described in the first aspect.

[0017] In a sixth aspect, an automatic frequency locking device based on laser modulation spectrum and saturation spectrum is provided, comprising the automatic frequency locking device based on laser modulation spectrum and saturation spectrum as in the second aspect, and using the automatic frequency locking method based on laser modulation spectrum and saturation spectrum as in the first aspect.

[0018] Unlike existing technologies, the present invention has at least the following beneficial effects: Different coarse adjustment levels with varying tuning precision are pre-configured. Based on these levels, the laser is tuned through multiple rounds of locking iterations. In each iteration, the output current and the scanning amplitude corresponding to the coarse adjustment level are applied to the laser, and frequency sampling is performed to obtain the frequency locking deviation. This deviation is used to update the next iteration. By using progressively increasing coarse adjustment levels, the deviation gradually decreases. When the fine locking conditions are met, frequency locking is achieved using an incremental PID mode. After frequency locking, the frequency deviation is acquired, and the multi-round locking iterations are automatically restarted when the frequency is lost. This process utilizes customizable coarse adjustment levels to adapt to different environments and laser types, improving the algorithm's adaptability. Furthermore, it automatically recovers frequency locking upon loss of lock, resulting in higher reliability. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0020] Figure 1 This is a flowchart of an automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 2 This is a flowchart of a method for obtaining peaks and troughs in an automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 3 This is a flowchart of an automatic frequency locking method based on laser modulation spectrum and saturation spectrum for updating output current, provided by an embodiment of the present invention. Figure 4 This is a flowchart of a method for switching coarse tuning levels in an automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 5 This is a flowchart of a method for achieving precise frequency locking in an automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 6 This is a flowchart of a method for determining loss of lock in an automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 6a This is a schematic diagram illustrating an example of determining loss of lock in an automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 7 This is a flowchart of a method for re-locking the frequency after loss of lock in an automatic frequency locking method based on the laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the peak and trough detection process in an automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 9 This is a diagram showing the SG filtering effect under different signal-to-noise ratios in an automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention. Figure 10 This is a configuration effect diagram of the initial scan amplitude and the offset of the reference sampling point in an automatic frequency locking method based on the laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention; Figure 11 This is a characteristic diagram of the saturation absorption spectrum and modulation spectrum of the rubidium D2 line of a 780 nm laser in an automatic frequency locking method based on the modulation spectrum and saturation spectrum of a laser provided in an embodiment of the present invention; Figure 12 This is a schematic diagram of an automatic frequency locking device based on laser modulation spectrum and saturation spectrum provided in an embodiment of the present invention. Detailed Implementation

[0021] 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 embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, a particular feature, structure, material, or characteristic may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated in embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0023] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0024] In the description of this invention, the expression “A and / or B” (where A and B are used to formally represent specific features) will be used. The corresponding expression includes the following three combinations: only A, only B, and a combination of A and B.

[0025] As used in this invention, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from a particular value, wherein the acceptable range of deviation is determined by those skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0026] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Example 1: This embodiment provides an automatic frequency locking method based on laser modulation spectrum and saturation spectrum, including: providing a laser to be sampled and monitoring the frequency of the laser, such as... Figure 1 As shown, the method flow includes: In step 101, the sampling range and the reference sampling point in the sampling range are set, a multi-level coarse adjustment level with progressively increasing debugging accuracy is configured, and the initial current is set as the output current.

[0028] In step 102, multiple rounds of locking iterations are performed. Each round of locking iteration includes: applying the output current and the scanning amplitude corresponding to the current coarse adjustment level to the laser, obtaining the modulation spectrum signal of the laser, which is obtained by frequency modulation and demodulation of the saturated absorption spectrum, and sampling within the sampling range of the modulation spectrum signal to obtain multiple sampling points, the number of sampling points being determined by the sampling range, identifying the peak and trough positions in the modulation spectrum signal based on the sampling points, calculating the deviation between the peak and trough positions and the reference sampling points, and updating the output current of the next round of locking iteration based on the deviation and the update gain corresponding to the current coarse adjustment level.

[0029] The application scenario of this embodiment is as follows: for frequency locking of the modulation spectrum and saturation spectrum of a laser, an output current is applied to the laser to obtain the saturation absorption spectrum, and the saturation absorption spectrum is frequency modulated and demodulated to obtain the saturation absorption spectrum. By controlling the magnitude of the output current, the position to be locked is adjusted and aligned to the set reference sampling point to complete the frequency locking. The position to be locked is the midpoint between the peak and trough positions in the modulation spectrum signal, and this midpoint corresponds to the center frequency of the spectral line of the saturation absorption spectrum.

[0030] In this embodiment, the sampling range refers to the sampling interval range of the spectrum in each round of locking iteration. The spectrum curve is obtained by sampling through multiple sampling points within the sampling range. The reference sampling point is one of the sampling points set manually within the sampling range. For example, if there are 1000 sampling points in the sampling range, the reference sampling point is usually selected at one-quarter of the scanning window, that is, the position of the 250th sampling point can be set as the reference sampling point.

[0031] Since it is impossible to directly lock the position to be locked to the reference sampling point during actual frequency locking, multiple locking iterations are required in this embodiment. In each locking iteration, the corresponding output current and scanning amplitude are applied to the laser, and sampling is performed according to the set sampling range to obtain the peak and trough positions on the spectrum. The position to be locked is compared with the reference sampling point to obtain the position deviation. The output current in the next locking iteration is adjusted according to the position deviation so that the position to be locked can be closer to the reference sampling point in the next locking iteration. Finally, through multiple locking iterations, the position to be locked is locked to the reference sampling point, and the frequency locking is completed.

[0032] Each level of coarse tuning corresponds to a parameter sequence. Each locking iteration requires applying the parameter sequence of one level of coarse tuning. The parameter sequence includes the scan amplitude, update gain, current step size, and convergence threshold. The scan amplitude is the bandwidth; a larger scan amplitude results in a larger spacing between adjacent peaks and troughs in the frequency spectrum, while a smaller scan amplitude results in a smaller spacing. The update gain is combined with the deviation calculated in the current locking iteration to calculate the output current for the next locking iteration. The current step size is the difference in output current between adjacent sampling points within the scan window. The convergence threshold is used to determine whether to enter the next coarse adjustment level. With multiple rounds of locking iterations, the position to be locked gets closer and closer to the reference sampling point. In the multi-level coarse adjustment levels with progressively increasing accuracy, the scanning amplitude, update gain, current step size, and convergence threshold all decrease step by step. That is, the bandwidth corresponding to the laser gradually decreases, and its adjustment range decreases accordingly. Furthermore, when switching coarse adjustment levels, the current step size also decreases synchronously. This allows the position to be locked to move closer to the reference sampling point more accurately during the adjustment process, thereby achieving progressively higher adjustment accuracy. The adjustment accuracy of the multi-level coarse adjustment levels increases step by step. The first level of coarse adjustment has the lowest adjustment accuracy, and the adjustment accuracy increases sequentially thereafter, with the last level of coarse adjustment having the highest adjustment accuracy. This ensures that multiple rounds of locking iterations meet the requirement of increasingly higher adjustment accuracy.

[0033] It should be noted that for the pre-set multi-level coarse adjustment parameter sequence, those skilled in the art can set it according to the actual environment and laser model, so that the algorithm can be applied to different lasers and environmental conditions, avoiding the problem of fixed parameters in traditional adjustment algorithms and improving practicality.

[0034] In step 103, it is determined whether to enter the next coarse adjustment level according to the preset level switching conditions: if the level switching conditions are met and there is a next coarse adjustment level, then switch to the next coarse adjustment level and continue to execute the next round of locking iteration; if it is in the last level of coarse adjustment and the fine locking conditions are met, then switch to incremental PID mode for fine locking.

[0035] In this embodiment, multiple coarse adjustment levels are pre-defined, with the debugging precision increasing progressively. During each round of locking iteration, it is necessary to determine whether to switch the coarse adjustment level to a higher precision level (i.e., the next coarse adjustment level). The level switching condition is as follows: the convergence value of the current locking iteration satisfies the convergence threshold corresponding to the current coarse adjustment level; if the level switching condition is met and a next coarse adjustment level exists, then switch to the next coarse adjustment level and continue executing the next round of locking iteration; if the level switching condition is not met, then continue using the current coarse adjustment level to execute the next round of locking iteration.

[0036] As the coarse adjustment level switches, the debugging accuracy of multi-round locking iteration becomes higher and higher. After the debugging accuracy is improved to a certain extent, simple coarse adjustment cannot meet the accuracy requirements of frequency locking. Therefore, when the pre-set last coarse adjustment level (i.e. the coarse adjustment level with the highest accuracy) also meets the level switching conditions, it switches to the incremental PID mode with higher debugging accuracy for fine locking to complete the frequency locking.

[0037] In step 104, after fine locking is completed, the frequency deviation of the laser is obtained. If it is determined that the lock has been lost, a safe current backoff is performed, and the locking iteration is restarted until the frequency is relocked.

[0038] In this embodiment, after frequency locking is completed using incremental PID mode, frequency deviation is monitored in real time. This allows for timely detection of locking failure caused by environmental disturbances, and a safe current backoff is executed upon loss of lock to prevent laser damage. Steps 102 and 103 are then re-executed to automatically re-lock the frequency, eliminating the need for manual intervention and improving frequency locking stability. This automatic frequency locking method is applicable to various types of lasers, including semiconductor lasers, gas lasers, and fiber lasers.

[0039] In this embodiment, coarse adjustment levels with different tuning accuracies are pre-configured. Based on the corresponding coarse adjustment levels, the laser is tuned through multiple rounds of locking iterations. In each round of locking iteration, the output current and the scanning amplitude corresponding to the coarse adjustment level are applied to the laser, and frequency sampling is performed to obtain the positions of peaks and troughs, thus obtaining the frequency locking deviation. The deviation is used to update the next round of locking iteration. By performing multiple rounds of locking iteration with coarse adjustment levels of progressively increasing accuracy, the deviation is gradually reduced. When the fine locking conditions are met, frequency locking is achieved through incremental PID mode, and the frequency deviation is obtained after frequency locking. When the frequency is lost, the multiple rounds of locking iteration are automatically restarted. In the above process, the custom coarse adjustment levels are used to adapt to different environments and laser types, improving the adaptability of the algorithm. Furthermore, the algorithm can automatically recover the frequency locking when the lock is lost, resulting in higher reliability.

[0040] In this embodiment, the parameter sequence corresponding to each coarse adjustment level includes a decreasing scan amplitude, update gain, current step size, and convergence threshold. The scan amplitude can decrease geometrically, as shown in the following expression: ; in, This is the initial scan amplitude, i.e., the scan amplitude corresponding to the 0th coarse adjustment level; is the scan amplitude corresponding to the k-th coarse adjustment level; r is the scan decrease ratio; k is the level number of the coarse adjustment level. For example, there are N levels of coarse adjustment levels, with the lowest level corresponding to level number 0 and the highest level corresponding to level number N-1.

[0041] Initial scan amplitude The setting range can be 15% to 80%, and the setting range for the scan decrease ratio r can be 0.3 to 0.6.

[0042] This embodiment takes an initial scan amplitude of 50%, a scan decrease ratio of 0.4, and a locked iteration scan amplitude of 2% as an example to provide a set of practically feasible parameter combinations, as shown in Table 1 below: Table 1 Parameter Table

[0043] It should be noted that the scan reduction ratio r can be adjusted when switching between different coarseness levels. In this embodiment, the initial scan amplitude is... It needs to be set relatively large to ensure that the peaks and troughs in the spectrum are covered.

[0044] After setting the above multi-level coarse adjustment hierarchy, locking iteration can be performed. In each round of locking iteration, the sampling of the spectrum and the acquisition of peak and trough positions involve the following design: filtering and derivative calculation of the sampling points to obtain peak and trough positions, such as... Figure 2 As shown, the method flow includes: In step 201, the sampling points are filtered to obtain filtered sampling points.

[0045] In this embodiment, the filter can be an SG (Savitzky-Golay) filter. A corresponding output current is configured for the laser. For the given laser, the corresponding saturated absorption spectrum transmittance model is: ; in: ν is the transmittance of the saturated absorption spectrum, and v is the resonance frequency. Background transmittance, The value range can be 0.9-1. The Doppler absorption coefficient is... It can be 0.3-0.4, where L is the length of the absorption cell. For the center frequency, To broaden the Doppler, It can be 500MHz@300k. It is a concave half-width. The value range can be 10MHz-20MHz. The saturation absorption enhancement coefficient, The value can range from 0.15 to 0.25.

[0046] The corresponding modulation spectrum signal expression is: ; in, The signal strength is at frequency v, where v is the resonant frequency. For modulation amplitude, The value range can be 5MHz-15MHz.

[0047] Discretize the spectral line into N sampling points. The expression for the signal-to-noise ratio of each sampling point is: ; Where SNR is the signal-to-noise ratio. For signal amplitude, Noise level.

[0048] In this embodiment, an SG filter window can be used. 11 points and the order p of the SG polynomial The least squares fitting coefficients for a 3x3 SG filter are: ,in Solution c by least squares Given that A is the Vandermonde matrix, the expression for the signal after SG filtering is: ; in, The signal is the filtered signal, and k is the first calibration parameter. Here, y represents the sampling point before filtering, and n represents the sampling point number.

[0049] The expression for the improved signal-to-noise ratio is: ; in, To improve the signal-to-noise ratio, The signal-to-noise ratio before improvement. In this embodiment, for the case of w=11 and p=3, the theoretical improvement in signal-to-noise ratio is 3dB-5dB.

[0050] In step 202, the first and second derivatives of the filtered sampling points are calculated.

[0051] In this embodiment, the first and second derivatives of the filtered sampling points can be calculated using central difference. The expression for the first derivative is: ; in, The first derivative at the sampling point, For the (n+1)th sampling point, For the (n-1)th sampling point, The default value is 1.

[0052] The expression for the second derivative is: ; in, The second derivative at the sampling point, ] represents the nth sampling point.

[0053] In step 203, when the absolute value of the first derivative is less than the first derivative threshold and the second derivative is less than the second derivative threshold, the location of the sampling point is determined to be the peak position.

[0054] In this embodiment, the condition for determining the peak is: satisfying the condition... ,in The threshold value for the first derivative corresponding to the peak. The threshold value is the second derivative of the wave peak.

[0055] In step 204, when the absolute value of the first derivative is less than the first derivative threshold and the second derivative is greater than the second derivative threshold, the location of the sampling point is determined to be a trough position.

[0056] In this embodiment, the condition for determining a trough is: satisfying the condition... ,in The threshold of the first derivative corresponding to the trough. The threshold value is the second derivative of the trough.

[0057] in, , .

[0058] Furthermore, in this embodiment, the obtained peak and trough positions need to be interpolated a second time to improve the positional accuracy. The corresponding algorithm expression is as follows: ; in, To improve the accuracy of the nth peak, The nth peak before improving accuracy. This is the position of the first-order peak. This is the location of the second-order peak.

[0059] Using the above method, the positional accuracy can be improved from the integer level to the 0.1 level.

[0060] Furthermore, after obtaining the peak and trough positions, it is necessary to acquire the deviation of the current locking iteration to calculate the output current corresponding to the next locking iteration. The corresponding design is as follows: calculate the deviation of the peak and trough positions from the reference sampling point, and update the output current of the next locking iteration based on the update gain corresponding to the current coarse adjustment level, such as... Figure 3 As shown, the method flow includes: In step 301, the peak difference between the peak position and the reference sampling point is calculated, and the trough difference between the trough position and the reference sampling point is calculated.

[0061] In this embodiment, the peak difference value is: The difference between the troughs is: ,in The peak position, The trough position, The reference sampling point can be located at one-quarter of the scan amplitude. In one exemplary configuration, assuming the total number of sampling points N=1000, then... That is, the reference sampling point can be the position of the 250th sampling point. The selection of this position ensures that the peak and trough features are always within the sampling range during the process of decreasing scanning amplitude and will not be truncated by the edge of the sampling range.

[0062] In step 302, the comprehensive frequency error is obtained based on the peak difference and trough difference.

[0063] In this embodiment, the expression for the comprehensive frequency error is: ; in, To account for the overall frequency error, Weighted by the peak difference. Weighted by the difference between the troughs. and All are positive numbers, and + =1. In one feasible embodiment, and Both can be 0.5. If multiple peaks and troughs are detected in the sampling range, the pair of peaks and troughs closest to the reference sampling point is taken.

[0064] In step 303, the current adjustment value is obtained based on the comprehensive frequency error and the update gain corresponding to the current coarse adjustment level.

[0065] The formula for calculating the current adjustment value is: ; in, This is the current adjustment value. To update the gain, To account for the overall frequency error, For single adjustment of the upper limit of current, To limit the current range.

[0066] In step 304, the output current applied in this round of locking iteration is added to the current adjustment value to obtain the output current required for the next round of locking iteration.

[0067] In this embodiment, the output current obtained in step 304 is applied to the laser in the next locking iteration to obtain a new spectrum.

[0068] Furthermore, in this embodiment, at the end of a locking iteration, it is necessary to determine the convergence status of the current locking iteration to determine whether to enter the next coarse adjustment level, thereby sequentially executing each coarse adjustment level with progressively increasing precision to achieve the effect of increasing precision during the debugging process. Therefore, this embodiment also involves the following design: determining whether to enter the next coarse adjustment level based on preset level switching conditions: if the level switching conditions are met and there is a next coarse adjustment level, then switching to the next coarse adjustment level and continuing to execute the next round of locking iteration, such as... Figure 4 As shown, it includes: In step 401, the convergence value of the current round of locking iteration is obtained based on the absolute value of the comprehensive frequency error.

[0069] In step 402, the convergence value is compared with the convergence threshold of the corresponding coarse adjustment level.

[0070] In step 403, when the convergence value of the consecutive preset number of rounds is less than the convergence threshold of the corresponding coarse adjustment level, the level switching condition is met, and the configuration of the next coarse adjustment level is adopted for the next round of locking iteration; otherwise, the level switching condition is not met, and the coarse adjustment level remains unchanged in the next round of locking iteration.

[0071] Furthermore, after multiple rounds of locking iterations have completed the convergence requirements of all coarse-tuning levels, it is necessary to switch to incremental PID mode for fine-tuning. The corresponding design is as follows: if it is at the last coarse-tuning level and the fine-tuning conditions are met, then switch to incremental PID mode for fine-tuning, such as... Figure 5 As shown, the method flow includes: In step 501, the output current and the scanning amplitude corresponding to the incremental PID mode are applied to the laser, and multiple sampling points are obtained by sampling within the sampling range. The peak and trough positions in the modulation spectrum signal are identified based on the sampling points. The peak difference between the peak position and the reference sampling point is calculated, and the trough difference between the trough position and the reference sampling point is calculated. The comprehensive frequency error is obtained based on the peak difference and trough difference.

[0072] In step 502, the current adjustment value is obtained based on the comprehensive frequency error and PID locking algorithm.

[0073] The expression for the current adjustment value is: ; in, This is the current adjustment value. This is the proportional control coefficient. Let k be the frequency error of the kth sample. The integral control coefficient, The sampling period is These are differential control coefficients; in one feasible embodiment, =0.05, =0.01, =0.01, =5ms. In this embodiment, the above is only used to demonstrate a feasible parameter setting. In actual application, each parameter can be set by those skilled in the art.

[0074] In this embodiment, for the anti-saturation and low-pass filtering of the PID locking algorithm, the integral accumulation stops when the output is saturated, and a first-order low-pass filter is added to the derivative term, with a cutoff frequency of... It can be 100Hz, and the corresponding expression is: ; in , For adjustment coefficients, This is the filtered differential value at the current time. This is the original filtered value at the current moment.

[0075] In step 503, the output current is adjusted according to the current adjustment value to achieve precise locking of the laser frequency.

[0076] Furthermore, this embodiment, based on the level switching conditions, further designs a stage switching strategy: In one strategy, if the fine-tuning condition is not met when the total number of iterations reaches the preset maximum number of iterations, the system will revert to the previous coarse-tuning level in the next locking iteration, and the scan amplitude in the corresponding coarse-tuning level will be increased by at least a preset percentage (e.g., 20%~50%). If convergence is still not achieved after the revert, the revert will continue or a fault alarm will be triggered. In another strategy, if the switching fails for a preset number of consecutive iterations (e.g., 3~5 times), a fault alarm will be triggered, and manual intervention will be required. Through the above design, the entire debugging process becomes more stable and complete. One of the above two strategies can be implemented; the preset maximum number of iterations and the preset number of iterations are both set by those skilled in the art according to the actual situation.

[0077] Furthermore, in this embodiment, after accurately locking the frequency using the incremental PID mode, considering that the frequency may still lose lock due to environmental interference and other reasons, a complete strategy is needed to monitor the loss of lock and to re-execute the frequency locking steps after detecting a loss of lock. Therefore, this embodiment also involves the following design: the criteria for determining the loss of lock, such as... Figure 6 As shown, the method flow includes: In step 601, the average frequency is obtained, and the difference between the average frequency and the frequency lock value is the frequency deviation.

[0078] In this embodiment, a saturated absorption signal of a preset duration is obtained. The preset duration is set by those skilled in the art according to actual conditions, and can be 100ms. The peak transmittance is then calculated. The transmittance peak value is used in subsequent calculations of theoretical spectral line values; the expression for the frequency deviation is: ; in, For frequency deviation, The mean frequency is... The frequency lock value is used. The average frequency can be the average of the frequency sequence within the most recent time window, which can be 10 seconds. In this embodiment, the above is only used to demonstrate a practically feasible time window setting. In actual applications, the time window can be set by those skilled in the art. The frequency lock value is the value at which the laser frequency needs to be kept locked under ideal conditions. However, under actual interference, there will be a deviation between the real-time measured average frequency and the frequency lock value. The frequency lock value is used to compare with the average frequency to obtain the degree of deviation of the current average frequency (i.e., frequency deviation). Subsequently, the frequency deviation is used to determine whether a momentary over-limit has occurred. The frequency lock value is set by those skilled in the art according to the actual situation.

[0079] In step 602, the frequency deviation is compared with the deviation threshold. If the frequency deviation is greater than the deviation threshold, it is determined that an instantaneous over-limit has occurred.

[0080] In step 603, if instantaneous over-limit occurs in N1 consecutive monitoring cycles, the last monitoring cycle in which instantaneous over-limit occurs is taken as the current monitoring cycle. The first M monitoring cycles including the current monitoring cycle are determined. The first M monitoring cycles are divided into the first M1 monitoring cycles including the current monitoring cycle and the first M2 monitoring cycles far from the current monitoring cycle. If the deterioration ratio of the average frequency deviation of the first M1 monitoring cycles to the average frequency deviation of the first M2 monitoring cycles exceeds a preset percentage, then the lockout is determined to be lost. Wherein, N1 is greater than or equal to 2, and M1 and M2 are both greater than or equal to 1.

[0081] To explain step 603 more intuitively, let's take the following scenario as an example. In this example, N1 is 3, M1 is 5, and M2 is 5. Therefore, in this example, the criteria for determining unlocking are: a momentary over-limit occurs in the current monitoring cycle; momentary over-limit occurs in three consecutive monitoring cycles including the current monitoring cycle; and within the 10 cycles preceding the current monitoring cycle, the average frequency deviation of the five cycles closer to the current monitoring cycle is greater than a preset percentage of the average frequency deviation of the five cycles farther from the current monitoring cycle. The preset percentage can be 150%. To illustrate the above example more clearly, as... Figure 6a As shown, Figure 6a In this diagram, each square represents a monitoring cycle, and the number in the square represents the monitoring cycle number. Starting from the 10th monitoring cycle, the 10th, 11th, and 12th monitoring cycles all experienced instantaneous exceedances (i.e., instantaneous exceedances occurred for three consecutive monitoring cycles). Therefore, the 12th monitoring cycle is taken as the current monitoring cycle. The 8th to 12th monitoring cycles are the M1 cycles closer to the current monitoring cycle, and the 3rd to 7th monitoring cycles are the M2 cycles further away from the current monitoring cycle. In this embodiment, the above is only used to demonstrate a practically feasible preset percentage setting. In actual applications, the preset percentage can be set by those skilled in the art, and it is optimal for M1 and M2 to be as consistent as possible.

[0082] Furthermore, upon determining that a loss of lock has occurred, a corresponding process needs to be designed to restore the frequency lock. Therefore, this embodiment also involves the following design: if a loss of lock is determined, a safe current backoff is executed, and the locking iteration is restarted until the frequency is relocked, such as... Figure 7 As shown, the method flow includes: In step 701, when it is determined that the lock has been lost, the configuration parameters before the lock was lost are recorded.

[0083] In this embodiment, the configuration parameters include current, temperature, and PID parameters.

[0084] In step 702, the output current is reduced to a preset safe ratio of the operating current.

[0085] In this embodiment, the preset safety ratio is set by those skilled in the art based on actual conditions, and the preset safety ratio can be 80%. The backoff current value corresponding to the preset safety ratio should not be less than the minimum current value required for stable laser output.

[0086] In step 703, starting from the lowest coarse adjustment level, multiple rounds of locking iterations are re-executed, and when the fine locking conditions are met, the incremental PID mode is switched to perform fine locking.

[0087] In step 704, the laser parameters are restored to the configuration parameters before the loss of lock.

[0088] After the frequency lock is restored, record information such as the time of loss of lock, the cause, and the time taken to relock the frequency.

[0089] To avoid frequent frequency re-locking, at least a first optimization strategy, a second optimization strategy, and a third optimization strategy are introduced. The automatic frequency locking method of this embodiment can be optimized by using the first optimization strategy, the second optimization strategy, and / or the third optimization strategy.

[0090] The first optimization strategy is to not perform lock loss monitoring within a preset safety time after successful relocking. The preset safety time can be set by those skilled in the art based on the actual situation. In one feasible embodiment, the preset safety time can be 60 seconds.

[0091] The second optimization strategy is to use more conservative parameters during the re-locking process, namely, to limit the size of the current iteration and reduce the scanning amplitude approximation speed. For example, the scanning amplitude corresponding to all coarse adjustment levels is reduced to 80% of the original scanning amplitude.

[0092] The third optimization strategy is to enter the protection mode and issue an alarm when the frequency re-locking fails for a preset number of consecutive times. The preset number of times can be set by those skilled in the art according to the actual situation. In a feasible embodiment, for example, the preset number of times can be 3 times.

[0093] Based on the complete method flow described above, this embodiment allows for customized configuration of various parameters in the process to adapt to different environments and laser models. The configurable ranges for each parameter are as follows: Initial scan amplitude: 15%~80%; Scan decrease ratio: 0.3~0.6; Locked iteration scan amplitude: 1%~5%; SG filter window: 7~21; SG polynomial order: 2~5; First derivative threshold: 0.005~0.02; Second derivative threshold: 0.02~0.08; Proportional control coefficient: 0.01~0.1; Integral control coefficient: 0.002~0.02; Differential control coefficient: 0.002~0.02; Deviation threshold: 2MHz~10MHz.

[0094] Example 2: This embodiment, based on embodiment 1, provides a complete algorithm flow and configurable parameters. The corresponding pseudocode is as follows: [Pseudocode begins] 1. Load user configuration parameters: initial scan amplitude, reference sampling point offset, deviation threshold, etc.

[0095] 2. Wait for the laser temperature to stabilize.

[0096] 3. Turn on the laser current.

[0097] 4. Main frequency locking cycle until the lock flag is set: a) Set the scan amplitude corresponding to the current coarseness level. .

[0098] b) Acquire modulation spectrum data (N sampling points, where N is determined by the sampling range).

[0099] c) Perform SG filtering on the original data (window length w, polynomial order p).

[0100] d) Detect the peak position of the filtered data and trough position .

[0101] e) If the detection is successful: i) Calculate the overall frequency error: = 0.5×( - ) - 0.5×( - ) ii) Update the gain based on the current coarse adjustment level. and combined frequency error Calculate the current adjustment value: = · And limit the amplitude.

[0102] iii) Adjust the laser current.

[0103] iv) When the convergence value of the preset number of consecutive rounds is less than the convergence threshold of the corresponding coarse adjustment level, the convergence is considered successful, and the process is switched to the next coarse adjustment level or locked. - If the current scan amplitude is less than or equal to the scan amplitude corresponding to the incremental PID mode, switch to PID lock and set the flag. - Otherwise, reduce the scan amplitude (multiply by the scan reduction ratio r) and proceed to the next coarse adjustment level.

[0104] f) If feature detection fails, execute the preset failure handling strategy.

[0105] 5. After PID locking, continuously monitor the saturated absorption spectrum and calculate the frequency deviation.

[0106] 6. If the frequency deviation continues to exceed the deviation threshold, automatic relocking is triggered (jump to step 4).

[0107] [End of pseudocode] The method provided in this embodiment offers a feasible set of experimental environmental conditions during actual implementation, as follows: the ambient temperature is stably controlled within the range of 23±0.5 degrees Celsius; the ambient relative humidity is controlled within the range of 45±5%RH; the vibration isolation measures adopt a combined isolation method consisting of an optical platform and an air-bearing vibration isolation system; and the electromagnetic shielding environment can be achieved by using a double-layer aluminum shielding box.

[0108] Peak and trough detection is performed under different signal-to-noise ratios, such as Figure 8 As shown, in Figure 8 In (a), (b), and (c), the horizontal axis represents the laser frequency, and the vertical axis represents the relative voltage. Figure 8 In the diagram, (a) represents the original signal and feature detection. Figure 8 In (a), the thin solid line represents the original input signal containing noise, the thick solid line represents the signal after SG filtering, and the black dots represent the identified peaks and troughs. Figure 8 (b) in the figure represents the zero-crossing detection of the first derivative, where the solid line is the first derivative curve of the smooth signal. Figure 8In the diagram (c), the peaks and troughs of the second derivative are determined. The solid line represents the second derivative curve of the smoothed signal. The negative region on the vertical axis represents the peak region (when the second derivative is less than a threshold value), and the positive region on the vertical axis represents the trough region (when the second derivative is greater than a threshold value). In summary, through... Figure 8 It can intuitively find the corresponding peak and trough positions and eliminate minor fluctuations.

[0109] To verify the robustness of the algorithm under different noise environments, four signal-to-noise ratio conditions were simulated, such as... Figure 9 The image shows the effect of SG filtering under different signal-to-noise ratios. Figure 9 In the figure, the horizontal axis represents laser frequency, and the vertical axis represents relative voltage. Figure 9 (a) in the figure is the signal waveform under the condition of a signal-to-noise ratio of 40dB. Figure 9 (b) in the diagram shows the signal waveform under a signal-to-noise ratio of 25 dB. Figure 9 (c) in the diagram shows the signal waveform under a signal-to-noise ratio of 15dB. Figure 9 (d) in the figure shows the signal waveform under a signal-to-noise ratio (SNR) of 8dB. It can be seen that under SNR conditions of 40dB, 25dB, and 15dB, the waveform changes are still largely recognizable, maintaining the ability to identify peaks and troughs. However, under the maximum noise condition of 8dB, the waveform cannot be identified. The filtering verification table for the four SNR conditions is shown in Table 2 below: Table 2 Filter Validation Table

[0110] As shown in Table 2, on the one hand, SG filtering can provide an improvement of about 10dB in signal-to-noise ratio under different signal-to-noise ratios; on the other hand, even under high noise conditions (e.g., 8dB signal-to-noise ratio), the peak and trough detection success rate still exceeds 80%.

[0111] like Figure 10 The image shown illustrates the configuration effects of the initial scan amplitude and the reference sampling point offset, serving to demonstrate the impact of the initial scan amplitude. Figure 10 In the figure, the horizontal axis represents laser frequency, and the vertical axis represents relative voltage. Figure 10 (a) shows the effect of different initial scan amplitudes (80%, 50%, 30%, and 15%) on signal smoothness. Figure 10 As can be seen from (a) in the figure, the larger the initial scan amplitude, the higher the signal smoothness, and the smaller the initial scan amplitude, the lower the signal smoothness. Figure 10 (b) in the diagram illustrates the impact of different reference sampling point locations on the locking success rate. Figure 10As can be seen in (b), when the reference sampling point is set to 250 sampling points, it is located between the peak and trough positions. Therefore, it is recommended to set 250 sampling points as the reference sampling point.

[0112] The effects of different initial scan amplitudes are shown in Table 3 below: Table 3 Effects of different scanning amplitudes

[0113] As shown in the table above, setting the initial scan amplitude to 50% achieves a relatively optimal balance between convergence speed and stability.

[0114] In this embodiment, the reference sampling point Offsets are allowed within the range of positions corresponding to sampling points 200 to 350 to adapt to the characteristic positions of different lasers. The default position is based on sampling point 250, and different offset values ​​are applied within this default position. The adjustments were made, and the locking success rate corresponding to the benchmark sampling point was obtained. The corresponding configuration is shown in Table 4 below: Table 4 Laser Feature Configuration Table

[0115] When frequency locking is performed using the parameter combinations provided in Table 1 of the aforementioned Example 1, the convergence process data is shown in Table 5 below: Table 5 Convergence Process Data Table

[0116] The average error in Table 5 is the average deviation between the midpoint and the reference sampling point between the peak and trough positions in multiple iterations.

[0117] As can be seen from the above configuration, the peak and trough positions gradually converge toward the reference sampling point, the average error shows an exponential decay trend, synchronized with the geometric decrease of the scanning amplitude, the total current adjustment decreases as the scanning amplitude decreases, and finally enters the fine-tuning mode.

[0118] like Figure 11 As shown, Figure 11 (a) in the image is the saturation absorption spectrum of the rubidium D2 line of a 780 nm laser. Figure 11 (b) in the table below shows the modulation spectrum feature map, and the corresponding environmental adaptability test is shown in Table 6. Table 6 Environmental Adaptability Test Table

[0119] As shown in Table 6, this experiment can operate stably in a wide environmental range of 15℃ to 35℃ and 30% to 70% RH. Vibration has a significant impact when the vibration range is 0.1Hz to 10Hz. To improve accuracy, a vibration isolation platform can be set up to reduce the impact of vibration on the experiment. Power supply fluctuations have a relatively small impact on the experiment when the power supply is -5% to 5%.

[0120] In summary, the beneficial effects of the method provided in this embodiment are: it supports custom parameter configuration, which can adapt to different lasers and environmental conditions; and the real-time loss-lock detection and automatic relock mechanism based on saturated absorption spectrum can significantly improve the reliability of system operation.

[0121] When conducting experimental verification of the application of 780nm semiconductor laser in rubidium atomic clock, it was found that the average lock-in time was shortened and the success rate of operation was significantly improved. It can work stably in a wide temperature and humidity range of 15℃ to 35℃ and 30% to 70% RH, and its short-term frequency stability meets the application requirements of rubidium atomic clock and other applications.

[0122] Example 3: like Figure 12 The diagram shown is a schematic representation of an automatic frequency locking device based on laser modulation and saturation spectra according to an embodiment of the present invention. This automatic frequency locking device based on laser modulation and saturation spectra includes one or more processors 41 and a memory 42.

[0123] Processor 41 and memory 42 can be connected via a bus or other means. Figure 12 Taking the example of a connection between China and Israel via a bus.

[0124] The memory 42, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs and non-volatile computer-executable programs, such as the automatic frequency locking method based on the laser modulation spectrum and saturation spectrum in the above embodiment. The processor 41 executes the automatic frequency locking method based on the laser modulation spectrum and saturation spectrum by running the non-volatile software program and instructions stored in the memory 42.

[0125] Memory 42 may include high-speed random access memory, and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, memory 42 may optionally include memory remotely located relative to processor 41, which can be connected to processor 41 via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0126] The program instructions / modules are stored in memory 42 and, when executed by one or more processors 41, perform the automatic frequency locking method based on the laser modulation spectrum and saturation spectrum in the above embodiments.

[0127] This invention also provides a computer storage medium storing computer program instructions; when the computer program instructions are executed by one or more processors, the processors execute the automatic frequency locking method based on laser modulation spectrum and saturation spectrum provided in this invention.

[0128] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An automatic frequency locking method based on laser modulation spectrum and saturation spectrum, characterized in that, include: Provide the laser to be sampled and monitor the frequency of the laser; Set the sampling range and the reference sampling point in the sampling range, configure a multi-level coarse adjustment level with progressively increasing debugging accuracy, and set the initial current as the output current; Perform multiple rounds of locking iterations. Each round of locking iteration includes: applying the output current and the scanning amplitude corresponding to the current coarse adjustment level to the laser; obtaining the modulation spectrum signal of the laser, which is obtained by frequency modulation and demodulation of the saturated absorption spectrum; sampling within the sampling range of the modulation spectrum signal to obtain multiple sampling points; identifying the peak and trough positions in the modulation spectrum signal based on the sampling points; calculating the deviation between the peak and trough positions and the reference sampling point; and updating the output current of the next round of locking iteration based on the deviation and the update gain corresponding to the current coarse adjustment level. Determine whether to enter the next coarse adjustment level based on the preset level switching conditions: if the level switching conditions are met and the next coarse adjustment level exists, switch to the next coarse adjustment level and continue to execute the next round of locking iteration; if it is in the last level of coarse adjustment and the fine locking conditions are met, switch to incremental PID mode for fine locking. After fine locking is completed, the frequency deviation of the laser is obtained. If it is determined that the lock has been lost, a safe current backoff is performed, and the multi-round locking iteration is restarted until the frequency is locked again.

2. The automatic frequency locking method based on laser modulation spectrum and saturation spectrum according to claim 1, characterized in that, The step of identifying the peak and trough positions in the modulation spectrum signal based on the sampling points specifically includes: The sampling points are filtered to obtain filtered sampling points; Calculate the first and second derivatives of the filtered sampling points; When the absolute value of the first derivative is less than the first derivative threshold and the second derivative is less than the second derivative threshold, the location of the sampling point is determined to be the peak position. When the absolute value of the first derivative is less than the first derivative threshold and the second derivative is greater than the second derivative threshold, the location of the sampling point is determined to be the trough location.

3. The automatic frequency locking method based on laser modulation spectrum and saturation spectrum according to claim 1, characterized in that, The calculation of the deviation between the peak position and the trough position and the reference sampling point, and the updating of the output current for the next locking iteration based on the deviation and the update gain corresponding to the current coarse adjustment level, specifically includes: Calculate the peak difference between the peak position and the reference sampling point, and calculate the trough difference between the trough position and the reference sampling point; The combined frequency error is obtained based on the peak difference and the trough difference. The current adjustment value is obtained based on the comprehensive frequency error and the update gain corresponding to the current coarse adjustment level; The output current applied in this round of locking iteration is added to the current adjustment value to obtain the output current required for the next round of locking iteration.

4. The automatic frequency locking method based on laser modulation spectrum and saturation spectrum according to claim 3, characterized in that, The process of obtaining the current adjustment value based on the comprehensive frequency error and the updated gain corresponding to the current coarse adjustment level specifically includes: The expression for calculating the current adjustment value is: ； in, The current adjustment value is... For the updated gain, The combined frequency error, For single adjustment of the upper limit of current, To limit the current range.

5. The automatic frequency locking method based on laser modulation spectrum and saturation spectrum according to claim 3, characterized in that, The step of determining whether to enter the next coarse adjustment level based on preset level switching conditions: if the level switching conditions are met and the next coarse adjustment level exists, then switch to the next coarse adjustment level and continue to execute the next round of locking iterations, specifically including: The convergence value of the current round of locking iteration is obtained based on the absolute value of the comprehensive frequency error; The convergence value is compared with the convergence threshold of the corresponding coarse adjustment level; When the convergence value of a consecutive preset number of rounds is less than the convergence threshold of the corresponding coarse adjustment level, the level switching condition is met, and the configuration of the next coarse adjustment level is used for the next round of locking iteration; otherwise, the level switching condition is not met, and the next round of locking iteration keeps the coarse adjustment level unchanged.

6. The automatic frequency locking method based on laser modulation spectrum and saturation spectrum according to claim 3, characterized in that, The conditions for determining the loss of lock specifically include: The average frequency is obtained, and the difference between the average frequency and the frequency lock value is the frequency deviation; The frequency deviation is compared with the deviation threshold. If the frequency deviation is greater than the deviation threshold, it is determined that a momentary over-limit has occurred. If instantaneous exceedances occur in all N1 consecutive monitoring cycles, the last monitoring cycle in which an instantaneous exceedance occurs is taken as the current monitoring cycle. The first M monitoring cycles, including the current monitoring cycle, are determined. The first M monitoring cycles are then divided into the first M1 monitoring cycles including the current monitoring cycle and the first M2 monitoring cycles far from the current monitoring cycle. If the average frequency deviation of the first M1 monitoring cycles deteriorates by more than a preset percentage compared to the average frequency deviation of the first M2 monitoring cycles, then a loss of lock is determined. Wherein, N1 is greater than or equal to 2, and M1 and M2 are both greater than or equal to 1.

7. The automatic frequency locking method based on laser modulation spectrum and saturation spectrum according to claim 1, characterized in that, If the system is at the last coarse adjustment level and meets the fine-tuning conditions, then it switches to incremental PID mode for fine-tuning, specifically including: The output current and the scanning amplitude corresponding to the incremental PID mode are applied to the laser, and multiple sampling points are obtained within the sampling range. The peak and trough positions in the modulation spectrum signal are identified based on the sampling points. The peak difference between the peak position and the reference sampling point is calculated, and the trough difference between the trough position and the reference sampling point is calculated. The comprehensive frequency error is obtained based on the peak difference and the trough difference. Based on the comprehensive frequency error and PID locking algorithm, the current adjustment value is obtained; The output current is adjusted according to the current adjustment value to achieve precise locking of the laser frequency.

8. The automatic frequency locking method based on laser modulation spectrum and saturation spectrum according to claim 1, characterized in that, If a loss of lock is determined, a safe current backoff is executed, and the multi-round locking iteration is restarted until the frequency is relocked. Specifically, this includes: When a lock loss is detected, the configuration parameters before the lock loss are recorded. Reduce the output current to a preset safe ratio of the operating current; Starting from the lowest coarse adjustment level, the multi-round locking iteration is re-executed, and when the fine locking condition is met, the incremental PID mode is switched to perform fine locking. The parameters of the laser are restored to their configuration parameters before the loss of lock.

9. An automatic frequency locking device based on laser modulation spectrum and saturation spectrum, characterized in that, The method includes at least one processor and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor for performing the automatic frequency locking method based on the laser modulation spectrum and saturation spectrum as described in any one of claims 1-8.

10. A non-volatile computer storage medium, characterized in that, The computer storage medium stores computer program instructions that, when executed by one or more processors, cause the processors to perform the automatic frequency locking method based on the laser modulation spectrum and saturation spectrum as described in any one of claims 1-8.

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