Method for driving laser based on pre-stored vector table for fast matching of CRDS cavity mode

Abstract

The application discloses a CRDS cavity mode fast matching laser driving method based on a pre-stored vector table and relates to the technical field of cavity ring-down spectroscopy.The CRDS cavity mode fast matching laser driving method based on the pre-stored vector table first controls a laser driver to perform first scanning in a preset wavelength range with a first scanning step, records a driving signal value after a ring-down signal is triggered and sequentially stores the driving signal value into a mode vector table; subsequent scanning is performed on each matching point in the table, a predicted offset and a starting point are determined according to historical data, scanning is performed in a search window with a smaller second scanning step, data in the table is updated after triggering, and the operation of jumping to a next matching point to predict a starting point is repeated until scanning and updating of all points are completed.The application realizes cavity mode fixed-point scanning through the pre-stored vector table, greatly reduces invalid scanning time, improves matching speed, accurately captures a resonance point, adapts to cavity mode drift, and guarantees matching accuracy and stability.

Description

Technical Field

[0001] This invention relates to the field of cavity ring-down spectroscopy, specifically to a CRDS cavity mode fast matching laser driving method based on a pre-stored vector table. Background Technology

[0002] Cavity ring-down spectroscopy (CRDS) is a highly sensitive optical measurement technique widely used in gas composition detection, material optical property analysis, environmental monitoring, and online industrial process monitoring due to its precise detection capabilities of light absorption characteristics. The core measurement principle involves coupling a laser into an optical resonant cavity. When the laser frequency matches the longitudinal mode resonant frequency of the cavity, the laser forms stable oscillations within the cavity. After the laser input is cut off, the optical absorption parameters of the measured object are calculated by detecting the exponential ring-down process of the light intensity within the cavity and combining this with the ring-down time, thus enabling precise measurement of relevant physical or chemical quantities.

[0003] Laser-driven modulation is a crucial step in achieving cavity mode matching in CRDS technology. The laser driver regulates the laser's operating state by outputting a specific driving signal, changing the laser output frequency to achieve matching control between the laser frequency and the longitudinal modes of the optical resonator. Only with precise cavity mode matching can the laser efficiently couple into the optical resonator, laying the foundation for accurate detection of subsequent ring-down signals. In practical applications of CRDS cavity mode matching, it is necessary to find the laser frequency that matches the longitudinal modes of the optical resonator through scanning tuning. The laser driving signal value corresponding to the cavity mode matching is the core parameter characterizing this matching state.

[0004] To improve cavity mode matching efficiency, the laser drive signal values ​​corresponding to cavity mode matching are recorded and stored during laser scanning tuning, forming relevant data characterizing the cavity mode matching state. Simultaneously, fine tuning of the laser frequency can be achieved by adjusting the laser scanning step size, ensuring the accuracy of cavity mode matching. In continuous CRDS measurements, optimizing subsequent laser drive scanning processes based on historical cavity mode matching drive signal data is a crucial direction for improving cavity mode matching efficiency. This allows the laser to match the current longitudinal mode frequency of the optical resonator more quickly, meeting the measurement efficiency and stability requirements of CRDS technology in various application scenarios. Related methods such as drive signal recording, scanning step size adjustment, and scanning optimization based on historical data have become important research and application directions for CRDS cavity mode matching laser drive technology.

[0005] The limitations of existing technologies include at least the following problems: The continuous wave scanning modulation method used in CRDS cavity mode matching requires a continuous and slow scan throughout the entire preset wavelength scanning range. To avoid mode hopping and mode loss, the scanning speed of the laser frequency must be strictly controlled. Furthermore, there is no targeted cavity mode fixed-point matching design, and optical signal detection and cavity mode matching judgment must be performed at each scanning point throughout the entire process. This significantly prolongs the overall scanning time of cavity mode matching, severely limiting the measurement speed and making it difficult to meet the application requirements of high-speed acquisition. Even if the possibility of mode hopping and mode loss is reduced by lowering the scanning speed, it is difficult to completely avoid the resonance point positioning deviation caused by laser frequency scanning nonlinearity and optical cavity length drift. Mode loss is still likely to occur, which in turn introduces systematic errors in the ring-down time measurement, significantly affecting the cavity mode matching efficiency and matching accuracy of CRDS technology. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a laser driving method for rapid matching of cavity modes in CRDS based on a pre-stored vector table. This method resolves the contradiction between slow measurement speed and easy mode omission caused by the need for slow scanning throughout the entire process in traditional continuous wave scanning CRDS to avoid mode skipping.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a CRDS cavity mode fast matching laser driving method based on a pre-stored vector table, comprising the following steps: controlling the laser driver to perform an initial scan within a preset wavelength scanning range, driving the laser stepwise with a first scan step size, and detecting whether the optical signal reaches the trigger threshold at each step; when a ring-down signal is triggered, recording the current driving signal value and storing it in the mode vector table in chronological order to complete the construction of the mode vector table; during subsequent scans, for each mode matching point recorded in the mode vector table, determining the prediction offset based on the historical matching data in the mode vector table, and using the driving signal value corresponding to that mode matching point. The predicted offset is subtracted to obtain the prediction starting point for this scan. The laser driver is controlled to start from the prediction starting point and scan within the set search window with a second scan step size, which is smaller than the first scan step size, until the ring-down signal is triggered again. The drive signal value corresponding to the latest ring-down signal is updated to the mode vector table, replacing the drive signal value of the original mode matching point in the mode vector table. The laser driver is controlled to jump directly to the prediction starting point corresponding to the next mode matching point in the mode vector table, and the steps of scanning and updating the mode vector table within the set search window are repeated until the scanning and updating of all mode matching points in the mode vector table are completed.

[0008] Furthermore, the specific steps for determining the prediction offset based on the historical matching data in the pattern vector table are as follows: read the most recent N consecutive updated drive signal values ​​corresponding to the current pattern matching point to be scanned in the pattern vector table; calculate the difference between the drive signal value after each update and the drive signal value before the update; perform an arithmetic mean on the calculated N-1 differences, and use the average value as the prediction offset for this scan.

[0009] Furthermore, the specific steps for determining the search window are as follows: obtain the historical drive signal values ​​corresponding to the current pattern matching point in the pattern vector table; calculate the statistical variance of the historical drive signal values; based on the statistical variance, find the corresponding search window radius value from the preset window radius mapping table; and determine the set search window with the prediction starting point as the center and the search window radius value as the boundary.

[0010] Further, the steps for determining the first scanning step size are as follows: obtain the free spectral range parameters of the optical resonator and the current frequency tuning coefficient of the laser driver; calculate the amount of driving signal change required to make the laser frequency change less than half of the free spectral range; and set the calculated amount of driving signal change as the first scanning step size.

[0011] Furthermore, the specific steps for detecting whether the optical signal has reached the trigger threshold are as follows: During each long dwell period, the optical intensity voltage signal output by the detector is continuously acquired; the average value of the optical intensity voltage signal within a preset time is calculated; the average value is compared with a preset fixed voltage threshold; when the average value continuously exceeds the fixed voltage threshold for a preset number of times, it is determined to be a trigger oscillation signal.

[0012] Furthermore, during the scanning process within the set search window until the ring-down signal is triggered again, if the ring-down signal is not triggered after the scan is completed, the specific steps for pattern recapture are as follows: a second search window is set with the original drive signal value corresponding to the current matching point of the pattern to be scanned in the pattern vector table as the center; the laser driver is controlled to scan within the second search window with the first scan step size; if the ring-down signal is successfully triggered within the second search window, the corresponding drive signal value at the time of triggering is updated to the pattern vector table.

[0013] Furthermore, the specific steps for maintaining the pattern vector table are as follows: After completing the scanning and updating of all pattern matching points in the pattern vector table, calculate the difference between the drive signal values ​​corresponding to adjacent pattern matching points; compare each difference with the preset normal difference range; if a difference exceeds the normal difference range, insert a supplementary scanning point between the adjacent point pairs; perform local verification scanning on the supplementary scanning points, and update the pattern vector table according to the verification results.

[0014] Furthermore, the specific steps for controlling the laser driver to directly jump to the prediction start point corresponding to the next mode matching point in the mode vector table are as follows: read the driving signal value corresponding to the next mode matching point from the mode vector table; determine the prediction offset corresponding to the next mode matching point based on the historical matching data in the mode vector table; subtract the corresponding prediction offset from the driving signal value corresponding to the next mode matching point to obtain the next prediction start point; control the output of the laser driver to jump from the current value to the next prediction start point.

[0015] Furthermore, the specific steps for recording the current drive signal value during the initial scan are as follows: when the detected optical signal reaches the trigger threshold, the laser driver is controlled to perform a local fine scan near the current drive signal value with a third scan step size; during the local fine scan, the signal intensity and corresponding drive signal value output by the detector are recorded in real time; the maximum value of the signal intensity is found; the drive signal value corresponding to the maximum value is used as the drive signal value corresponding to the current mode matching point and stored in the mode vector table.

[0016] Furthermore, the specific steps for introducing temperature drift compensation are as follows: read the temperature sensor measurement value of the optical resonant cavity; calculate the difference between the current temperature value and the reference temperature value; calculate the temperature-induced drive signal compensation amount based on the preset temperature drive value drift coefficient; and add the drive signal compensation amount to the calculation of the predicted offset.

[0017] The present invention has the following beneficial effects:

[0018] (1) The CRDS cavity mode fast matching laser driving method based on the pre-stored vector table completes the full range stepwise scan and constructs the mode vector table in the first scan step. This eliminates the need for subsequent scans to detect the entire wavelength range one by one. Instead, it only targets the mode matching points recorded in the table and determines the prediction start point by combining historical matching data. Within the set search window, it performs local fine scanning with a smaller second scan step. It can also directly jump to the prediction start point of the next matching point and directly skip the invalid area without cavity mode matching. This method eliminates the disadvantage of traditional continuous wave scanning, which requires low-speed scanning throughout to prevent mode skipping. It greatly reduces the time of invalid scanning and is no longer limited by the speed of slow scanning throughout. This significantly improves the overall scanning efficiency of cavity mode matching and can well meet the high-speed acquisition requirements of CRDS technology in practical applications. It is suitable for various measurement scenarios that require rapid cavity mode matching.

[0019] (2) The CRDS cavity mode fast matching laser driving method based on the pre-stored vector table performs a local fine scan near the current driving signal value after triggering the ring-down signal in the first scan with a third scan step size. The driving signal value corresponding to the maximum signal intensity is selected and stored in the vector table to avoid the deviation between the trigger point and the actual cavity mode resonance peak. The subsequent scan uses a smaller second scan step size, which can more accurately capture the actual resonance matching point. At the same time, temperature drift compensation is introduced to add the compensation amount of the driving signal caused by temperature to the calculation of the predicted offset, which cancels the cavity length drift caused by temperature change of the optical resonant cavity. In addition, the optical signal triggering must meet the judgment rule that the average value continuously exceeds a fixed threshold, which effectively avoids false triggering caused by noise. The multi-faceted design makes the cavity mode matching result more accurate and greatly improves the overall stability of the CRDS measurement process.

[0020] (3) The CRDS cavity mode fast matching laser driving method based on the pre-stored vector table dynamically determines the search window radius according to the statistical variance of the driving signal values ​​of the mode matching point in each cycle. When the cavity mode drift dispersion is high, a larger window radius is automatically matched to ensure accurate identification of the matching point after drift. If no ringing signal is triggered within the set search window, the mode can be recaptured through the second search window with the first scan step size to solve the matching failure problem caused by large cavity mode drift. At the same time, the mode vector table is maintained after each scan, and the difference in driving signal values ​​of adjacent matching points is calculated. When the difference exceeds the normal range, a supplementary scan point is inserted and local verification is performed to effectively prevent mode omission due to cavity mode changes. In addition, the predicted offset is calculated based on historical matching data, which can adapt to the slow drift law of the cavity mode. This allows the method to stably complete cavity mode matching under complex actual working conditions with temperature fluctuations and slight cavity mode drift, significantly improving the environmental adaptability of CRDS cavity mode matching.

[0021] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0022] Figure 1 This is an example diagram of a conventional continuous wave scanning modulation signal in the CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to the present invention.

[0023] Figure 2 This is a flowchart of the laser driving process in the CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to the present invention.

[0024] Figure 3 This is a schematic diagram of the full-range step-by-step scanning used in the first scan of the CRDS cavity mode fast matching laser driving method based on the pre-stored vector table of the present invention.

[0025] Figure 4This is a schematic diagram of the second and subsequent step scans in the CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to the present invention.

[0026] Figure 5 This is a flowchart illustrating the specific steps involved in the CRDS cavity mode fast matching laser driving method based on a pre-stored vector table, specifically the steps for detecting whether the optical signal has reached the trigger threshold. Detailed Implementation

[0027] Please see Figure 1-4 This invention provides a technical solution: a CRDS cavity mode fast matching laser driving method based on a pre-stored vector table, comprising the following steps: controlling the laser driver to perform an initial scan within a preset wavelength scanning range, driving the laser stepwise with a first scan step size, and detecting whether the optical signal reaches a trigger threshold at each step; when a ring-down signal is triggered, recording the current driving signal value and storing it in the mode vector table in chronological order to complete the construction of the mode vector table; during subsequent scans, for each mode matching point recorded in the mode vector table, determining the prediction offset based on the historical matching data in the mode vector table, and subtracting the prediction offset from the driving signal value corresponding to the mode matching point. The offset serves as the prediction starting point for this scan. The laser driver is controlled to start from the prediction starting point and scan within the set search window with a second scan step size, which is smaller than the first scan step size, until the ring-down signal is triggered again. The drive signal value corresponding to the latest ring-down signal is updated in the mode vector table, replacing the drive signal value of the original mode matching point in the mode vector table. The laser driver is controlled to jump directly to the prediction starting point corresponding to the next mode matching point in the mode vector table, and the steps of scanning and updating the mode vector table within the set search window are repeated until the scanning and updating of all mode matching points in the mode vector table are completed.

[0028] Figure 1 This diagram illustrates a conventional continuous wave scanning modulation signal. By superimposing a small-amplitude triangular wave perturbation onto the modulation current of the laser, the laser wavelength fluctuates within a certain range, thus covering the modes of the matched upper cavity. However, due to the wavelength variation and energy dispersion, the accumulated signal may be insufficient to trigger the ring-down signal to turn off during mode matching, resulting in mode omission.

[0029] Figure 2The diagram illustrates the laser driving process. After power-on, the device first reads the preset scanning range and scans the entire range step by step. The driving current remains at each driving value for several milliseconds, which is sufficient to accumulate enough optical signal to trigger the generation of a ring-down signal. Because each step is very small, mode skipping and mode omissions are avoided. After each ring-down signal is triggered, the driving signal value at that moment is recorded, forming a vector table of laser driving signal values ​​that match the cavity mode and are stored in chronological order. During the second scan, the laser driving signal value for each step is read sequentially from this vector table. Because there is a certain time delay between mode matching and recording the driving signal value, each recorded laser driving signal value needs to be shifted forward by m steps before the shifted value is set as the laser's driving signal value. The laser drive signal value starts scanning from the value stored in the vector table corresponding to matching mode 1, shifted forward by m. The scan then progresses step-by-step until the ring-down signal is triggered. At this point, the recorded drive signal value replaces the stored value for matching mode 1 in the vector table. The scan then jumps directly to the value stored in the vector table corresponding to matching mode 2, shifted forward by m, and so on, until matching mode n is complete. Finally, the drive signal value recorded at the trigger point replaces the stored value for matching mode n in the vector table. The first full-range step-by-step scan takes a slightly longer time. However, each subsequent scan jumps directly to the value shifted forward by m from the previous recorded point, significantly reducing the scan time without missing any modes.

[0030] The preset wavelength scanning range is: to The corresponding drive signal value range is to ;

[0031] Second scan step size satisfy:

[0032] ;

[0033] in, It is a positive integer greater than 1;

[0034] The pattern vector table is represented as follows:

[0035] ;

[0036] in, For the first The drive signal value of each pattern matching point The timestamp recorded for it, The total number of pattern matching points, and .

[0037] Specifically, the steps for determining the prediction offset based on historical matching data in the pattern vector table are as follows:

[0038] Read the most recent N consecutive updated drive signal values ​​corresponding to the current pattern matching point in the pattern vector table, specifically:

[0039] For the first in the pattern vector table For each pattern matching point, extract its nearest... The next updated sequence of drive signal values: ;

[0040] The numbers in parentheses indicate the update order. This is the latest updated value;

[0041] The difference between the updated drive signal value and the original drive signal value is calculated for each update, specifically as follows:

[0042] for to Calculate the difference between adjacent updates:

[0043] ;

[0044] Obtain the difference sequence ;

[0045] For the calculated The differences are taken as an arithmetic mean, and the average value is used as the prediction offset for this scan. Specifically:

[0046] Calculate the predicted offset:

[0047] ;

[0048] Use it as the pattern in this scan The predicted offset.

[0049] In this implementation scheme, the design of calculating the predicted offset based on historical matching data provides an accurate reference for determining the prediction starting point of subsequent scans. This effectively adapts to the drift pattern of the cavity model. This method selects the most recent drive signal update data of the current matching point, calculates the difference between adjacent update values ​​and takes the average to obtain the predicted offset. This ensures that the determined offset closely matches the actual drift trend of the cavity model, avoiding the problem that fixed offset values ​​are difficult to adapt to the dynamic changes of the cavity model. Using the predicted offset obtained in this way to set the scan prediction starting point allows the starting position of subsequent scans to be closer to the current actual cavity model matching point, significantly reducing the subsequent scan range, reducing invalid scans, and improving the efficiency of cavity model matching. At the same time, the calculation based on the average of multiple update data can offset the random deviation caused by a single drift, making the predicted offset more reliable.

[0050] Specifically, the steps for determining the search window are as follows:

[0051] Obtain the values ​​of the driving signals corresponding to the current matching point of the pattern to be scanned in the pattern vector table. Specifically:

[0052] For the first in the pattern vector table For each pattern matching point, obtain all historical drive signal values. ,in This represents the total number of historical records for that point.

[0053] The statistical variance of each driving signal value is calculated as follows:

[0054] Calculate the variance of the sequence:

[0055] ;

[0056] in, This is the average value;

[0057] Based on the statistical variance, the corresponding search window radius value is retrieved from the preset window radius mapping table, specifically as follows:

[0058] The preset window radius mapping table is defined as a function:

[0059] ;

[0060] For example, linear mapping:

[0061] ;

[0062] in, and These are preset coefficients;

[0063] Will Substituting the values, we obtain the search window radius:

[0064] ;

[0065] The search window is defined with the prediction starting point as the center and the search window radius as the boundary. Specifically:

[0066] Let the prediction starting point be... ;

[0067] The search window is set to a range. .

[0068] In this implementation scheme, the search window design is determined by combining the historical drive signal values ​​of the pattern matching point. This allows the window size to be set precisely to match the actual drift state of the cavity model. This method first obtains the historical drive signal values ​​of the matching point and calculates the statistical variance. The variance can intuitively reflect the fluctuation of the cavity model drift. Then, a preset mapping table is used to match the corresponding window radius according to the variance, thereby determining the search window centered on the prediction starting point. This method abandons the fixed window setting. The window size will be adjusted accordingly depending on the different fluctuations of the cavity model drift. It will not be difficult to cover the actual cavity model matching point due to the window being too small, nor will it increase the unnecessary scanning range due to the window being too large. This effectively reduces invalid scanning while ensuring that the matching point is not missed.

[0069] Specifically, the steps for determining the first scan step size are as follows:

[0070] The free spectral range parameters of the optical resonator and the current frequency tuning coefficient of the laser driver are obtained as follows:

[0071] The free spectral range parameter is: The unit is GHz;

[0072] The current frequency tuning coefficient is: The unit is GHz / mA;

[0073] The calculation of the driving signal change required to make the laser frequency change less than half of the free spectral range is as follows:

[0074] According to the inequality ;

[0075] Solve for the required change in the driving signal ;

[0076] The calculated change in the driving signal is set as the first scan step size, specifically as follows:

[0077] First scan step size satisfy:

[0078] ;

[0079] in, It is a positive coefficient less than 1.

[0080] In this implementation scheme, the first scanning step size is determined by combining the core parameters of the optical resonator and the laser driver. This ensures that the step size setting for the first scan has a practical physical basis, rather than being arbitrarily chosen. This method first obtains the free spectral range of the resonator and the current frequency tuning coefficient of the driver, and then calculates the amount of driving signal change that keeps the laser frequency change within a reasonable range. The first scanning step size is set accordingly. Furthermore, a margin is reserved for the step size setting through coefficient design. This effectively avoids skipping the cavity mode matching point due to an excessively large step size, ensuring that the first full-range scan can cover all cavity modes without mode omission. At the same time, it also avoids the problem of low scanning efficiency caused by an excessively small step size, balancing the integrity and scanning speed of the first scan, and making the mode vector table constructed after the first scan more complete.

[0081] Specifically, such as Figure 5 As shown, the specific steps for detecting whether the optical signal has reached the trigger threshold are as follows:

[0082] During each long dwell period, the light intensity voltage signal output by the detector is continuously collected, specifically as follows:

[0083] Let the stay time be... The sampling frequency is The acquired discrete voltage signal sequence is then... ,in ;

[0084] The average value of the light intensity voltage signal over a preset time period is calculated as follows:

[0085] After taking Each sampling point (corresponding to a preset time) );

[0086] Calculate the average:

[0087] ;

[0088] The average value is compared with a preset fixed voltage threshold, specifically as follows:

[0089] Let the fixed voltage threshold be ,Compare and Size;

[0090] When the average value continuously exceeds a fixed voltage threshold for a preset number of times, it is determined to trigger a ringback signal, specifically as follows:

[0091] Set counter ;

[0092] when > hour, ,otherwise =0;

[0093] when ≥ When the preset number of times is reached, it is determined to be a trigger oscillation signal.

[0094] In this implementation scheme, the detection and determination of the optical signal trigger threshold are completed through a multi-stage design, making the trigger judgment of the waning signal more in line with the actual situation and effectively avoiding false triggering and missed triggering. During the long dwell period of each step, the optical intensity voltage signal is continuously collected to ensure sufficient time to complete signal acquisition and accumulate enough optical signal, avoiding missed triggering due to insufficient signal acquisition. The average value is calculated by selecting the sampling points in the later stage, which can eliminate the initial transient fluctuations of the signal and make the collected signal more reflective of the actual optical intensity state. The waning signal is triggered only when the average value continuously exceeds the threshold by a counter, rather than being determined by a single exceedance. This can effectively cancel the interference caused by instantaneous noise and avoid false triggering caused by accidental signal fluctuations.

[0095] Specifically, the scan is performed within the set search window until the ringback signal is triggered again. If the ringback signal is not triggered after the scan is completed, the specific steps for mode recapture are as follows:

[0096] Centered on the original drive signal value corresponding to the current pattern matching point in the pattern vector table, a second search window is set, specifically as follows:

[0097] Assume the original drive signal value is The radius of the second search window is The second search window is ,in , >1 is the expansion factor;

[0098] The laser driver is controlled to scan within the second search window at a first scan step size, specifically as follows:

[0099] from Start with step size Step by step scan to And execute the trigger judgment at each step;

[0100] If a ringback signal is successfully triggered within the second search window, the corresponding drive signal value at the time of triggering will be updated in the mode vector table, specifically as follows:

[0101] Let the drive signal value at the time of triggering be... Then use Replace the original value in the pattern vector table .

[0102] In this implementation scheme, when the original search window is unable to find a matching point due to excessive cavity mode drift, a larger second search window is set with the original drive signal value as the center. This expands the scanning coverage and adapts to the large drift of the cavity mode. At the same time, the first scanning step size is used to scan within the second window, which ensures the coverage of the scan without increasing the scanning time too much due to the step size being too small. There is no need to re-perform a full-range scan, saving the overall scanning time. If the decay signal is successfully triggered within the second window, the new drive signal value is updated to the mode vector table, and the historical data in the table is corrected in a timely manner, so that the records in the mode vector table always match the actual state of the cavity mode.

[0103] Specifically, the steps for maintaining the pattern vector table are as follows:

[0104] After completing the scanning and updating of all pattern matching points in the pattern vector table, the difference between the driving signal values ​​corresponding to adjacent pattern matching points is calculated, specifically as follows:

[0105] Let the updated sequence of driving signal values ​​in the mode vector table be... Calculate the difference between adjacent values , ;

[0106] Each difference is compared to a preset normal difference range, specifically as follows:

[0107] The preset normal difference range is ; judge one by one Does it meet the requirements? ;

[0108] If a difference exceeds the normal difference range, a supplementary scan point is inserted between the adjacent point pairs, specifically as follows:

[0109] like If it exceeds the range, then in and Supplementary scan points are inserted between them, and their initial drive signal value is set to... ;

[0110] A local verification scan is performed on the supplementary scan points, and the pattern vector table is updated based on the verification results, specifically as follows:

[0111] exist A fine scan is performed in a small area nearby. If a new pattern matching point is found, it is inserted into the pattern vector table and reordered.

[0112] Otherwise, delete the supplementary scan point.

[0113] In this implementation scheme, after each round of scanning and updating of all matching points, the difference between the driving signal values ​​of adjacent matching points is calculated and compared with the normal range. This can promptly detect abnormal spacing caused by cavity mode changes. For adjacent point pairs that exceed the range, supplementary scanning points are inserted, and local verification scanning is performed. This can promptly capture new pattern matching points generated by cavity mode changes, avoiding mode omissions. After the verification scan, if there are new matching points, they are inserted into the vector table and reordered. If there are no new matching points, the supplementary scanning points are deleted. This ensures that the vector table can cover all actual cavity mode matching points without leaving invalid scanning points.

[0114] Specifically, the steps for controlling the laser driver to directly jump to the prediction start point corresponding to the next mode matching point in the mode vector table are as follows:

[0115] The drive signal value corresponding to the next pattern matching point is read from the pattern vector table, specifically as follows:

[0116] Let the index of the current pattern matching point be The index of the next pattern matching point is Read its drive signal value ;

[0117] Based on historical matching data in the pattern vector table, the predicted offset corresponding to the next pattern matching point is determined, specifically as follows:

[0118] Calculation mode Predicted offset ;

[0119] The next prediction starting point is obtained by subtracting the corresponding prediction offset from the driving signal value corresponding to the next pattern matching point. Specifically:

[0120] Calculate the next prediction starting point ;

[0121] The laser driver output is controlled to jump from the current value to the next prediction starting point, specifically as follows:

[0122] Immediately adjust the laser driver's output current from its current value to Complete the redirect.

[0123] In this implementation scheme, the drive signal value of the next matching point is read before the jump, and the corresponding predicted offset is calculated in combination with historical matching data to determine the accurate prediction starting point. This ensures that the scanning starting position after the jump matches the actual state of the cavity mode, eliminating the need for additional adjustment of the scanning starting point and allowing subsequent scanning to proceed quickly. The laser driver directly adjusts the output current from the current value to the value corresponding to the next predicted starting point, achieving rapid switching of the scanning starting point without wasting extra time due to excessive adjustments. It also eliminates the need to scan the cavity mode-free regions between adjacent matching points one by one, directly skipping intervals with no matching value. This precise and rapid jumping method ensures that the overall scanning process does not linger in invalid regions, making the scanning operations of each matching point smoother and further reducing the overall time consumption of cavity mode matching, continuously ensuring the efficient progress of the scanning process.

[0124] Specifically, the steps for recording the current drive signal value during the initial scan are as follows:

[0125] When the detected light signal reaches the trigger threshold, the laser driver is controlled to perform a local fine scan around the current drive signal value with a third scan step size. Specifically:

[0126] Let the current drive signal value be ,by Centered on;

[0127] In scope Within, with the third scan step Perform a scan;

[0128] During the local fine scanning process, the signal strength and corresponding drive signal value output by the detector are recorded in real time, specifically as follows:

[0129] Record scan point sequence ,in For scan point driving values, For the corresponding signal strength;

[0130] Find the maximum value of the signal strength, specifically:

[0131] Find the maximum signal strength ;

[0132] And record the corresponding drive signal value. ;

[0133] The driving signal value corresponding to the maximum value is used as the driving signal value corresponding to the current pattern matching point and stored in the pattern vector table, specifically as follows:

[0134] Will The driving signal value of the pattern matching point is stored in the pattern vector table.

[0135] In this implementation scheme, after detecting the optical signal trigger threshold, the current driving signal value is not directly recorded. Instead, a local fine scan is performed with this value as the center and a third scan step size is used to focus on the area around the trigger point. This approach avoids expanding the scan range and increasing the time required for the first scan, while accurately capturing changes in the surrounding signal intensity. During the scan, the signal intensity and the corresponding driving signal value are recorded in real time, which can fully reflect the signal state of the area. The maximum signal intensity found in this way corresponds to the true resonance point of cavity mode matching. This value is stored in the mode vector table, so that the initially constructed vector table has accurate basic data, providing a reliable reference for determining the prediction start point and setting the search window for all subsequent scans.

[0136] Specifically, the steps for introducing temperature drift compensation are as follows:

[0137] The temperature sensor readings of the optical resonant cavity are specifically as follows:

[0138] Read the current temperature value output by the temperature sensor. ;

[0139] The difference between the current temperature value and the reference temperature value is calculated as follows:

[0140] Calculate the temperature difference:

[0141] ;

[0142] in, This is the preset reference temperature;

[0143] Based on the preset temperature drive value drift coefficient, the compensation amount of the drive signal caused by temperature is calculated, specifically as follows:

[0144] Let the temperature-driven drift coefficient be... (Unit: mA / °C);

[0145] Temperature compensation amount ;

[0146] The driving signal compensation is added to the calculation of the predicted offset, specifically as follows:

[0147] The compensation amounts are then added together, resulting in the corrected prediction offset:

[0148] ;

[0149] in, This is the original prediction offset.

[0150] In this implementation scheme, temperature drift compensation is introduced to obtain the temperature information of the optical resonator in real time. The temperature deviation is obtained by comparing the current temperature with the reference temperature. Then, the corresponding driving signal compensation amount is calculated by combining the preset temperature driving value drift coefficient. The compensation amount is directly superimposed on the original predicted offset to complete the correction. Changes in ambient temperature will directly change the working state of the optical resonator, causing the cavity mode matching position to shift. The offset calculated by relying solely on historical data is difficult to cover the impact of temperature. This design can correct the prediction starting point in advance, so that the scanning starting point is close to the actual cavity mode position after the temperature change. The position deviation caused by temperature fluctuation is offset from the calculation stage. The entire compensation process does not require manual intervention or additional scanning steps. The laser drive and cavity mode matching are always adjusted synchronously with the temperature change, avoiding matching deviation caused by temperature interference.

[0151] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0152] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A fast laser driving method for CRDS cavity mode matching based on a pre-stored vector table, characterized in that, Includes the following steps: The laser driver is controlled to perform an initial scan within a preset wavelength scanning range, and the laser is driven step by step with a first scan step size. At each step, the optical signal is detected to see if it reaches the trigger threshold. When a ring-down signal is triggered, the current driving signal value is recorded and stored in the mode vector table in chronological order, thus completing the construction of the mode vector table. During subsequent scans, for each pattern matching point recorded in the pattern vector table, the prediction offset is determined based on the historical matching data in the pattern vector table. Specifically, the most recent N consecutive updated drive signal values ​​corresponding to the current pattern matching point to be scanned in the pattern vector table are read; the difference between the drive signal value after each update and the drive signal value before the update is calculated. The arithmetic mean of the N-1 differences is calculated, and the average value is used as the predicted offset for this scan. The prediction starting point for this scan is the driving signal value corresponding to the pattern matching point minus the prediction offset. The laser driver is controlled to start from the predicted starting point and scan within a set search window with a second scan step size. The second scan step size is smaller than the first scan step size until the ring-down signal is triggered again. The steps for determining the set search window are: obtaining the values ​​of the driving signals corresponding to the matching point of the current scanned mode in the mode vector table. Calculate the statistical variance of each driving signal value; based on the statistical variance, find the corresponding search window radius value from the preset window radius mapping table; determine the set search window with the prediction starting point as the center and the search window radius value as the boundary; Update the drive signal value corresponding to the latest triggered ringback signal to the mode vector table, and replace the drive signal value of the original mode matching point in the mode vector table. The laser driver is controlled to jump directly to the prediction start point corresponding to the next mode matching point in the mode vector table, and the steps of scanning and updating the mode vector table within the set search window are repeated until the scanning and updating of all mode matching points in the mode vector table are completed.

2. The CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to claim 1, characterized in that, The steps for determining the first scan step size are as follows: Obtain the free spectral range parameters of the optical resonator and the current frequency tuning coefficient of the laser driver; Calculate the amount of change in the driving signal required to make the change in laser frequency less than half of the free spectral range; The calculated change in the driving signal is set as the first scan step size.

3. The CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to claim 1, characterized in that, The specific steps for detecting whether the optical signal has reached the trigger threshold are as follows: During each long dwell period, the light intensity and voltage signals output by the detector are continuously collected; Calculate the average value of the light intensity voltage signal over a preset time period; The average value is compared with a preset fixed voltage threshold. When the average value continuously exceeds the fixed voltage threshold for a preset number of times, it is determined to trigger a oscillation signal.

4. The CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to claim 1, characterized in that, The scan is performed within the set search window until the ringback signal is triggered again. If the ringback signal is not triggered after the scan is completed, the specific steps for mode recapture are as follows: A second search window is set with the original drive signal value corresponding to the current matching point of the pattern to be scanned in the pattern vector table as the center; The laser driver is controlled to scan within the second search window at a first scan step size; If a ringback signal is successfully triggered within the second search window, the corresponding drive signal value at the time of triggering will be updated in the mode vector table.

5. The CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to claim 1, characterized in that, The specific steps for maintaining the pattern vector table are as follows: After completing the scanning and updating of all pattern matching points in the pattern vector table, the difference between the driving signal values ​​corresponding to adjacent pattern matching points is calculated. Each difference is compared to a preset normal difference range; If a difference exceeds the normal difference range, a supplementary scan point is inserted between the adjacent point pairs; Perform local verification scans on the supplementary scan points and update the pattern vector table based on the verification results.

6. The CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to claim 1, characterized in that, The specific steps for controlling the laser driver to jump directly to the prediction start point corresponding to the next mode matching point in the mode vector table are as follows: Read the drive signal value corresponding to the next pattern matching point from the pattern vector table; Based on the historical matching data in the pattern vector table, determine the predicted offset corresponding to the next pattern matching point; Subtract the corresponding prediction offset from the driving signal value corresponding to the next pattern matching point to obtain the next prediction starting point; The output of the laser driver is controlled to jump from the current value to the next prediction starting point.

7. The CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to claim 1, characterized in that, The specific steps for recording the current drive signal value during the initial scan are as follows: When the detected light signal reaches the trigger threshold, the laser driver is controlled to perform a local fine scan around the current drive signal value with a third scan step size. During the local fine scanning process, the signal strength and corresponding drive signal value output by the detector are recorded in real time; Find the maximum signal strength; The driving signal value corresponding to the maximum value is used as the driving signal value corresponding to the current pattern matching point and stored in the pattern vector table.

8. The CRDS cavity mode fast matching laser driving method based on a pre-stored vector table according to claim 1, characterized in that, The specific steps for introducing temperature drift compensation are as follows: Read the temperature sensor readings from the optical resonant cavity; Calculate the difference between the current temperature value and the reference temperature value; Calculate the compensation amount of the drive signal caused by temperature based on the preset temperature drive value drift coefficient; The driving signal compensation is added to the calculation of the predicted offset.

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