A method and system for controlling spot consistency of a DFB laser

Abstract

The application relates to the technical field of laser control, in particular to a spot consistency control method and system of a DFB laser, the method comprising the following steps: acquiring the current and temperature of each DFB laser at each time in each control cycle; calculating the kink prominence, temperature rise drift coefficient, temperature drop drift coefficient and heat source interference value of each DFB laser under each control cycle; determining the expansion factor of the positive argument domain and the negative argument domain in the fuzzy control algorithm, and controlling the temperature of the DFB laser in real time to control the spot consistency of the DFB laser. Through selecting the appropriate expansion factor, the argument range of the fuzzy control algorithm is dynamically adjusted, the response speed of the temperature control of the DFB laser is improved, the temperature of the DFB laser is more accurately controlled, and the spot consistency control is realized.

Description

Technical Field

[0001] This application relates to the field of laser control technology, specifically to a method and system for controlling the beam uniformity of a DFB laser. Background Technology

[0002] DFB lasers (distributed feedback lasers) are important devices in the field of optoelectronics. They utilize Bragg gratings within a semiconductor to achieve single-mode selection through distributed light feedback, exhibiting high speed, narrow linewidth, and dynamic single-mode operation characteristics. Temperature variations affect the wavelength, power, and beam quality of DFB lasers. Precise temperature control of DFB lasers ensures the consistency of beam shape, size, and intensity distribution.

[0003] DFB lasers, with their high side-mode suppression ratio and high beam quality, are widely used in TDLAS detectors. Fuzzy PID control algorithms can adapt to the nonlinear temperature variations of DFB lasers, and can be optimized using fuzzy rules. However, DFB lasers are temperature-sensitive devices. In multi-gas TDLAS detectors integrating multiple DFB lasers, the different operating temperatures of these lasers amplify the interference from ambient temperature, causing temperature drift and leading to errors in temperature control. Furthermore, traditional fuzzy PID control algorithms, operating within a fixed fuzzy domain, struggle to adapt to varying ambient temperatures, affecting the precise control of the DFB laser's internal temperature and the stability of its operating temperature. This results in poor beam uniformity and consequently, larger detection errors in the TDLAS detector. Summary of the Invention

[0004] To address the aforementioned technical problems, a method and system for controlling the beam uniformity of a DFB laser are provided to resolve the existing issues.

[0005] The solution to the technical problem of this application is to provide a method and system for controlling the beam uniformity of a DFB laser, including the following steps:

[0006] In a first aspect, embodiments of this application provide a method for controlling the beam uniformity of a DFB laser, the method comprising the following steps:

[0007] Acquire the current and temperature of each DFB laser in the multi-gas TDLAS detector at each moment during each control cycle;

[0008] For each DFB laser in each control cycle, current spikes are obtained based on the deviation of the current difference between adjacent time points; the duration and frequency of continuous occurrence of current spikes are analyzed, as well as the average current level of continuous occurrence of current spikes, and the spike significance of each DFB laser in each control cycle is calculated.

[0009] Compare the temperature of each DFB laser at each moment in the preset local time period before each control cycle with the preset temperature to obtain the temperature rise time and temperature fall time; analyze the temperature change trend of all temperature rise times and all temperature fall times in the local time period, and combine the burr significance to obtain the temperature rise drift coefficient and temperature fall drift coefficient of each DFB laser in each control cycle.

[0010] The temperature correlation between each DFB laser and the other DFB lasers is analyzed under each control cycle to obtain the interference heat sources of each DFB laser; combined with the difference of the preset temperature between each DFB laser and different interference heat sources, the heat source interference value of each DFB laser under each control cycle is obtained.

[0011] Based on the temperature rise drift coefficient and temperature fall drift coefficient, and combined with the heat source interference value, the scaling factors of the positive and negative domains of discourse in the fuzzy control algorithm are determined respectively. Through the fuzzy control algorithm, the temperature of the DFB laser is controlled in real time to control the beam consistency of the DFB laser.

[0012] Preferably, the method for further obtaining the current burr points is as follows:

[0013] Calculate the average current of each DFB laser at all times during each control cycle;

[0014] The difference in current between each DFB laser at each moment in each control cycle and the previous moment is denoted as the current difference.

[0015] The moment when the current difference is greater than the average value within each control cycle is selected and recorded as the current spike point.

[0016] Preferably, the calculation of the glitch significance of each DFB laser in each control cycle includes:

[0017] The times when current spikes occur consecutively within each control cycle are used to form spike intervals.

[0018] The time length between the upper and lower limits in each glitch interval is recorded as the glitch duration; the average value of the current difference corresponding to all times in each glitch interval is recorded as the glitch amplitude.

[0019] Calculate the sum of the products of the puncture duration and the puncture amplitude corresponding to all puncture intervals within each control cycle;

[0020] Statistically analyze the frequency of all current spikes occurring within each control cycle;

[0021] The spuriousness is the normalized result of the product of the sum and the frequency.

[0022] Preferably, the further acquisition process of each temperature rise time and each temperature drop time is as follows:

[0023] For each DFB laser, the moment when the temperature is higher than the corresponding preset temperature within the local time period is recorded as the temperature rise moment; the moment when the temperature is lower than the corresponding preset temperature within the local time period is recorded as the temperature drop moment.

[0024] Preferably, obtaining the temperature rise drift coefficient and temperature drop drift coefficient of each DFB laser in each control cycle includes:

[0025] Each temperature rise time and each temperature drop time within the local time period is combined with its corresponding temperature to form a two-dimensional array;

[0026] Linear fitting is performed on the two-dimensional arrays corresponding to all temperature rise times and all temperature fall times within the local time period to obtain the slope of the fitted line, which is denoted as the first slope and the second slope, respectively; positive mapping is performed on the first slope and the second slope, which are denoted as the temperature rise trend value and the temperature fall trend value, respectively.

[0027] The temperature rise drift coefficient is the product of the burr significance and the temperature rise trend value;

[0028] The temperature drop drift coefficient is the ratio of the burr significance to the temperature drop trend value.

[0029] Preferably, the process for acquiring each interference heat source of each DFB laser is as follows:

[0030] The temperature correlation between any two DFB lasers at all times within each control cycle is denoted as the temperature coherence degree; the threshold for dividing the temperature coherence degree between any DFB laser and all other DFB lasers within each control cycle is obtained.

[0031] The remaining DFB lasers whose temperature compatibility with any DFB laser is greater than the segmentation threshold are denoted as the interfering heat sources of any DFB laser.

[0032] Preferably, obtaining the thermal interference value of each DFB laser in each control cycle includes:

[0033] Calculate the cumulative sum of the temperature coordination between any DFB laser and all other DFB lasers within each control cycle;

[0034] The proportion of the temperature coordination degree between any DFB laser and each interference source in the summation is used as the temperature interference weight between any DFB laser and each interference source.

[0035] The difference between the preset temperature corresponding to any DFB laser and the preset temperature corresponding to each interfering heat source is calculated and denoted as the temperature control difference;

[0036] Based on the temperature interference weight, the temperature control difference between any DFB laser and all interference sources is weighted and summed to obtain the heat source interference value of any DFB laser in each control cycle.

[0037] Preferably, determining the scaling factors of the positive and negative universes of discourse in the fuzzy control algorithm includes:

[0038] For each DFB laser in each control cycle, if the heat source interference value is greater than 0, the scaling factor of the positive domain is the product of the normalized value of the heat source interference value and the temperature rise drift coefficient, and the scaling factor of the negative domain is the temperature drop drift coefficient.

[0039] If the heat source interference value is less than 0, the scaling factor of the negative domain is the product of the normalized value of the absolute value of the heat source interference value and the temperature drop drift coefficient, and the scaling factor of the positive domain is the temperature rise drift coefficient.

[0040] If the heat source interference value is equal to 0, the scaling factor of the positive domain is the temperature rise drift coefficient, and the scaling factor of the negative domain is the temperature drop drift coefficient.

[0041] Preferably, the real-time temperature control of the DFB laser includes:

[0042] Calculate the average temperature of each DFB laser at all times during each control cycle, and record it as the actual temperature;

[0043] The difference between the actual temperature of each DFB laser and its corresponding preset temperature in each control cycle is recorded as the temperature deviation; the difference between the temperature deviation of each DFB laser in each control cycle and the previous control cycle is calculated as the deviation change rate.

[0044] For each DFB laser in each control cycle, the range of the preset initial universe of discourse is adjusted based on the scaling factors of the positive and negative universes of discourse. Based on the adjusted universe of discourse range, the temperature deviation and the rate of change of the deviation are used as inputs to the fuzzy PID control algorithm to control the temperature of each DFB laser in each control cycle in real time.

[0045] Secondly, embodiments of this application also provide a beam uniformity control system for a DFB laser, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of the beam uniformity control method for a DFB laser described above.

[0046] This application has at least the following beneficial effects:

[0047] This application improves the accuracy of temperature acquisition and control by correcting the B value of the NTC resistor inside the DFB laser in different temperature ranges. It analyzes current deviations, identifies current spikes, and calculates the spike significance of each DFB laser in each control cycle. This is beneficial because it considers abnormal current fluctuations, reflecting the interference effect of current spikes on the temperature inside the DFB laser. Secondly, it compares the temperature of each DFB laser with the preset temperature in local time periods before each control cycle, selects the temperature rise and temperature fall times, and analyzes the trends of these times to determine the temperature rise drift coefficient and temperature fall drift coefficient. This is beneficial because it comprehensively considers the temperature drift of the DFB laser from the preset temperature and the temperature changes caused by the current, thus reflecting the degree of wavelength drift of the DFB laser towards longer or shorter wavelengths, evaluating the wavelength output stability of the laser, and demonstrating the measurement error of the multi-gas TDLAS detector. Furthermore, it analyzes the consistency of temperature changes among different DFB lasers, obtaining the value of each DFB laser's temperature. This method calculates the heat source interference value of each DFB laser in each control cycle, targeting various interfering heat sources. Its advantages include selecting lasers with relatively consistent temperature changes, identifying the most significant interfering heat sources for each DFB laser, reflecting the temperature fluctuations caused by these heat sources, and assessing the temperature drift caused by these heat sources. Furthermore, it determines the scaling factors for the positive and negative domains in the fuzzy control algorithm, and uses this algorithm to control the DFB laser temperature in real time, thereby ensuring beam consistency. This approach leverages the temperature drift caused by interference to dynamically adjust the domain of the fuzzy control algorithm for each DFB laser in different control cycles by selecting appropriate scaling factors. This real-time temperature control improves the response speed, provides more precise temperature control, ensures stable temperature control, locks the output center wavelength, and achieves beam consistency control. Attached Figure Description

[0048] The following section provides a more detailed description of a method for controlling the beam consistency of a DFB laser according to the present application, with reference to the accompanying drawings.

[0049] Figure 1 A flowchart illustrating the steps of a method for controlling the beam uniformity of a DFB laser, as provided in this application embodiment;

[0050] Figure 2 A flowchart illustrating the steps of a method for obtaining the thermal interference value of each DFB laser in each control cycle provided in this application embodiment;

[0051] Figure 3 A flowchart illustrating the steps of the method for obtaining the scaling factor provided in this application embodiment. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description, in conjunction with the accompanying drawings and embodiments, provides a method and system for controlling the beam uniformity of a DFB laser proposed in this application. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0054] Please see Figure 1 The diagram illustrates a flowchart of a method for controlling the beam uniformity of a DFB laser according to an embodiment of this application. The method includes the following steps:

[0055] Step 1: Obtain the current and temperature of each DFB laser in the multi-gas TDLAS detector at each moment during each control cycle.

[0056] Semiconductor lasers, also known as laser diodes, have advantages such as small size, lightweight, high electro-optical conversion efficiency, and compact structure. Semiconductor lasers are relatively sensitive devices; the accuracy and stability of their output are mainly affected by two physical quantities: temperature and current. Changes in current cause changes in the output wavelength of the semiconductor laser, leading to alterations in its operating state. Simultaneously, as an electro-optical conversion device, semiconductor lasers inevitably convert some electrical energy into heat energy during operation, causing temperature increases. Increased temperature leads to an increase in the threshold current and a shift in the center wavelength. Conversely, excessively low temperatures can also affect the output power of the semiconductor laser.

[0057] Multi-gas TDLAS (Tunable Diode Laser Absorption Spectroscopy) detectors commonly use a multi-source multiplexing structure for detecting the composition of mixed gases. A single multi-gas TDLAS detector integrates multiple DFB (Distributed Feedback Laser) lasers, each with an output center wavelength corresponding to the absorption peak of a specific gas. During mixed gas detection, it is crucial to ensure consistent beam patterns for each DFB laser. Therefore, controlling the constant current and temperature of each DFB laser is necessary to lock its wavelength. To guarantee the stability of the semiconductor laser during actual operation, precise temperature control is essential.

[0058] When measuring the temperature of DFB lasers, since constant current sources have the advantages of being less affected by the environment and having strong anti-interference capabilities, the temperature measurement circuit is designed by using constant current sources for all DFB lasers in the multi-gas TDLAS detector to achieve the effect of locking the wavelength. In addition, current monitoring and overcurrent protection circuits are added to the driving circuit of each DFB laser to realize the functions of real-time monitoring of current and instantaneous cut-off, so as to obtain the current of each DFB laser at each moment.

[0059] In this embodiment, the constant current source is designed as a precision voltage-controlled constant current source based on an operational amplifier. Furthermore, the current sampling frequency is 200Hz. As for other implementation methods, the implementer can set it according to the actual situation.

[0060] Each DFB laser incorporates a negative temperature coefficient thermistor (NTC) for temperature measurement. The resistance of the NTC decreases as temperature increases. There are many equations describing the thermistor's resistance versus temperature characteristics, such as the basic exponential equation, the Steinhart-Hart equation, and the Hoge-3 equation. In this embodiment, the relationship between the resistance of the negative temperature coefficient thermistor and temperature can be described using the Steinhart-Hart equation as follows:

[0061]

[0062] Among them, R T2 R is the resistance value at temperature T2. T1 Let T be the resistance value at temperature T1, B be the material coefficient of the thermistor, and exp[] be an exponential function with the natural constant as the base.

[0063] It should be noted that the Steinhart-Hart equation is a well-known technique and will not be elaborated upon here.

[0064] Furthermore, based on the above formula, since the accuracy of the B value directly affects the accuracy of temperature measurement, the B value is corrected, and segmented selection is performed for different temperature ranges, specifically as follows:

[0065] In this embodiment, the temperature measurement range of the DFB laser is designed to be [10, 60]. [10, 60] is divided into multiple temperature intervals, with a temperature difference interval of 5℃ between each interval. Therefore, each temperature interval can be represented as [T1, T2], where T2 - T2 = 5℃. For ease of understanding, [10, 60] is further divided into [10, 15], [15, 20], ..., [55, 60]. According to the Steinhart-Hart equation, the above formula is transformed as follows:

[0066]

[0067] Here, ln() is a logarithmic function with the natural constant as the base.

[0068] Therefore, the B value for each temperature range can be obtained. The temperature measurement circuit designed by the constant current source method uses a high-precision instrumentation amplifier to differentially amplify and acquire the weak temperature sampling voltage signal. After performing ADC analog-to-digital conversion and voltage-to-resistance conversion, combined with the B value corresponding to different temperature ranges, and substituted into the Steinhart-Hart equation, the temperature of each DFB laser at different times can be calculated.

[0069] It should be noted that the process of obtaining the laser temperature through the temperature measurement circuit designed by the constant current source method is a well-known technology and will not be described in detail here; secondly, the voltage acquisition frequency is 200Hz, therefore, the corresponding temperature acquisition frequency is also 200Hz. As for other implementation methods, implementers can set it according to the actual situation.

[0070] A control cycle with a preset duration is set; therefore, the temperature and current of each DFB laser at each moment are obtained under each control cycle.

[0071] In this embodiment, the preset duration of the control cycle is 100ms, that is, when the temperature of the DFB laser is adjusted by the fuzzy control algorithm, it is controlled and adjusted once every 100ms. As for other implementation methods, the implementer can set it according to the actual situation.

[0072] Thus, the temperature and current of each DFB laser at each moment under each control cycle are obtained.

[0073] Step 2: For each DFB laser in each control cycle, obtain the current spike points based on the deviation of the current difference between adjacent time points; analyze the duration and frequency of continuous occurrence of current spike points, as well as the average level of current of continuous occurrence of current spike points, and calculate the spike significance of each DFB laser in each control cycle.

[0074] During the operation of a DFB laser, short-term current spikes can directly cause changes in the instantaneous power of the laser chip, leading to localized temperature fluctuations in the laser through the Joule heating effect. Therefore, by analyzing the current changes within each control cycle, the current spike points can be identified, specifically:

[0075] Calculate the average current of each DFB laser at all times during each control cycle;

[0076] The difference in current between each DFB laser at each moment in each control cycle and the previous moment is denoted as the current difference.

[0077] In this embodiment, the absolute value of the difference between the current of each DFB laser at each moment in each control cycle and the previous moment is denoted as the current difference.

[0078] The moment when the current difference is greater than the average value within each control cycle is recorded as the current spike point;

[0079] Furthermore, the significance of the glitch is calculated by observing the continuous occurrence of current glitch points, specifically as follows:

[0080] Statistically analyze the frequency of all current spikes occurring within each control cycle;

[0081] The times when current spikes occur consecutively within each control cycle are used to form spike intervals.

[0082] The time length between the upper and lower limits in each glitch interval is denoted as the glitch duration.

[0083] The average value of the current difference corresponding to all times within each glitch interval is denoted as the glitch amplitude.

[0084] Calculate the sum of the products of the glitch duration and the glitch amplitude corresponding to all glitch intervals in each control cycle; and use the normalized result of the product of the sum and the frequency as the glitch significance of each DFB laser in each control cycle.

[0085] In this embodiment, the formula for calculating the glitch significance of the nth DFB laser in the rth control cycle is:

[0086]

[0087] Among them, P r,nLet η be the glitch significance of the nth DFB laser in the rth control cycle. r,n w is the frequency of the nth DFB laser in the rth control cycle. i f is the duration of the glitch in the i-th glitch interval of the n-th DFB laser during the r-th control cycle. i M represents the glitch amplitude of the nth DFB laser in the i-th glitch interval during the r-th control period. r,n Let be the number of all glitch intervals of the nth DFB laser in the rth control cycle, and norm[] be the normalization function. In this embodiment, the sigmoid function is used for normalization. The sigmoid function is a well-known technique and will not be described in detail here.

[0088] It should be noted that, due to the Joule heating effect, the larger the glitch amplitude, the greater the power interference and temperature fluctuations that the current glitch may cause to the DFB laser. The longer the glitch duration, the longer the current glitch phenomenon lasts, and the stronger the persistence of temperature fluctuations within the DFB laser, thus exacerbating the impact of the DFB laser current on temperature. The frequency mentioned reflects the frequency of current glitch occurrence, assessing the significant impact of the cumulative glitch effect on the DFB laser. The greater the glitch significance, the greater the impact of current changes on temperature fluctuations within the DFB laser.

[0089] Thus, the spurt significance of each DFB laser under each control cycle is obtained.

[0090] Step 3: Compare the temperature of each DFB laser at each moment in the preset local time period before each control cycle with the preset temperature to obtain the temperature rise time and temperature fall time; analyze the temperature change trend of all temperature rise times and all temperature fall times in the local time period, and combine the glitch significance to obtain the temperature rise drift coefficient and temperature fall drift coefficient of each DFB laser in each control cycle.

[0091] Furthermore, since the preset temperatures of different DFB lasers in a multi-gas TDLAS detector are not necessarily the same, and due to the influence of the external environment and the long-term operation of the DFB lasers, the temperatures of different DFB lasers will gradually drift away from the preset temperatures, leading to temperature instability of the DFB lasers. Therefore, by analyzing the long-term trend of temperature deviation of each DFB laser, the temperature rise drift coefficient and temperature drop drift coefficient are calculated, specifically:

[0092] Select a preset time period before each control cycle and record it as a local time period;

[0093] In this embodiment, the duration of the preset time period is set to 10 minutes. As for other implementation methods, the implementer can set it according to the actual situation.

[0094] For each DFB laser, the moment when the temperature is higher than the corresponding preset temperature within the local time period is recorded as the temperature rise moment; the moment when the temperature is lower than the corresponding preset temperature within the local time period is recorded as the temperature drop moment.

[0095] In this embodiment, since the output wavelength of the DFB laser changes with temperature, and each gas has its unique absorption characteristics and corresponding laser wavelengths are different when detecting multiple gases using a multi-gas TDLAS detector, the laser needs to operate at different wavelengths to match the absorption spectrum of a specific gas. Therefore, different DFB lasers in the multi-gas TDLAS detector need to be set with different preset temperatures to be precisely tuned to the required wavelength. Thus, the preset temperature of one DFB laser is set to 25°C, that is, the temperature of the DFB laser is controlled at 25°C, and the preset temperature of another DFB laser is set to 15°C. As other implementation methods, the implementer can set them according to the actual situation.

[0096] The temperature rise times within the local time period and their corresponding temperatures are combined into a two-dimensional array;

[0097] A linear fit is performed on the two-dimensional array corresponding to all temperature rise moments within the local time period to obtain the slope of the fitted line, which is denoted as the first slope.

[0098] The temperature drop times within the local time period and their corresponding temperatures are combined into a two-dimensional array;

[0099] A linear fit is performed on the two-dimensional array corresponding to all temperature drop moments within the local time period to obtain the slope of the fitted line, which is denoted as the second slope.

[0100] In this embodiment, the least squares method is used for linear fitting. The least squares method is a well-known technique and will not be described in detail here.

[0101] The first slope and the second slope are positively mapped respectively, and recorded as the temperature rise trend value and the temperature fall trend value respectively;

[0102] It should be noted that the positive mapping process is as follows: the first slope and the second slope are positively mapped by exponential functions respectively. Assuming the first slope is denoted as k1 and the second slope as k2, exp(k1) is taken as the result of the positive mapping and denoted as the temperature rise trend value, and exp(k2) is taken as the result of the positive mapping and denoted as the temperature fall trend value. Here, exp() is an exponential function with the natural constant as the base.

[0103] The product of the burr significance and the temperature rise trend value is used as the temperature rise drift coefficient of each DFB laser in each control cycle.

[0104] The ratio of the burr significance to the temperature drop trend value is used as the temperature drop drift coefficient of each DFB laser in each control cycle.

[0105] It should be noted that the glitch significance reflects the impact of current changes on the DFB laser's temperature fluctuations. The greater the glitch significance, the greater the potential temperature fluctuation within the DFB laser, and the more significant the temperature rise or fall drift caused by current changes. A positive first slope indicates that the DFB laser is drifting towards higher temperatures. When the DFB laser is at high temperatures, its wavelength will drift towards longer wavelengths, affecting the stability of the wavelength output and increasing the measurement error of the multi-gas TDLAS detector, thus the temperature rise drift coefficient is larger. A negative second slope, with a larger absolute value, indicates that the DFB laser is drifting towards lower temperatures. When the DFB laser is at low temperatures, its output wavelength will drift towards shorter wavelengths, affecting the measurement results, thus the temperature fall drift coefficient is larger.

[0106] Step 4: Analyze the temperature correlation between each DFB laser and the other DFB lasers under each control cycle, and obtain the interference heat sources of each DFB laser; combine the differences in the preset temperatures between each DFB laser and different interference heat sources to obtain the heat source interference value of each DFB laser under each control cycle.

[0107] Furthermore, the multi-gas TDLAS detector has a high degree of integration and miniaturization. A single multi-gas TDLAS detector contains multiple DFB lasers, and the temperatures of different DFB lasers can vary at the same time, leading to multiple heat source interference phenomena for each DFB laser. Affected by interference from other DFB lasers, the interference from temperature changes between different DFB lasers is analyzed to calculate the heat source interference value. The flowchart of the method for obtaining the heat source interference value of each DFB laser in each control cycle provided in this application embodiment is shown below. Figure 2 As shown, it specifically includes:

[0108] The degree of temperature correlation between any two DFB lasers at all times within each control cycle is denoted as temperature coherence.

[0109] In this embodiment, the correlation is measured by calculating the reciprocal of the DTW distance between the temperatures of any two DFB lasers at all times within each control cycle. The calculation of the DTW distance is a well-known technique and will not be described in detail here.

[0110] It should be noted that the greater the temperature coherence, the more consistent the temperature change characteristics between the two DFB lasers, and the more likely they are to have mutual influence.

[0111] Obtain the segmentation threshold for the temperature coherence between any DFB laser and all other DFB lasers within each control cycle;

[0112] In this embodiment, the segmentation threshold is obtained by the Otsu's method, which is a well-known technique and will not be described in detail here.

[0113] The remaining DFB lasers whose temperature compatibility with any DFB laser is greater than the segmentation threshold are denoted as the interfering heat sources of any DFB laser.

[0114] Calculate the cumulative sum of the temperature coordination between any DFB laser and all other DFB lasers within each control cycle;

[0115] The ratio of the temperature compatibility between any DFB laser and each interference source to the summation is used as the temperature interference weight between any DFB laser and each interference source.

[0116] It should be noted that the greater the temperature interference weight, the more likely the two DFB lasers are to transfer heat, and the greater the influence of interference sources from the other DFB lasers on any one of the DFB lasers.

[0117] The difference between the preset temperature corresponding to each interfering heat source and the preset temperature corresponding to any DFB laser is calculated and denoted as the temperature control difference;

[0118] In this embodiment, the difference between the preset temperature corresponding to each interfering heat source and the preset temperature corresponding to any DFB laser is calculated and denoted as the temperature control difference.

[0119] Based on the temperature interference weight, the temperature control difference between any DFB laser and all interference sources is weighted and summed to obtain the heat source interference value of any DFB laser in each control cycle.

[0120] It should be noted that the greater the temperature control difference between each interfering heat source and any of the DFB lasers, the stronger the heat source interference that causes temperature drift in any of the DFB lasers, and the more likely it is to cause temperature drift in any of the DFB lasers. If the heat source interference value is positive, it means that the preset temperature of the interfering heat source is higher than that of any of the DFB lasers, and it will dissipate heat to any of the DFB lasers, which is likely to cause temperature drift interference that increases the temperature of any of the DFB lasers. If the heat source interference value is negative, it means that the preset temperature of the interfering heat source is lower than that of any of the DFB lasers, and it absorbs heat from any of the DFB lasers, which is likely to cause temperature drift interference that decreases the temperature of any of the DFB lasers.

[0121] Thus, the thermal interference value of any DFB laser in each control cycle is obtained.

[0122] Step 5: Based on the temperature rise drift coefficient and temperature drop drift coefficient, and in combination with the heat source interference value, determine the scaling factors of the positive and negative domains of discourse in the fuzzy control algorithm, respectively. Through the fuzzy control algorithm, control the temperature of the DFB laser in real time to control the beam consistency of the DFB laser.

[0123] Furthermore, in the process of controlling the temperature of the DFB laser using the fuzzy PID control algorithm, the universe of discourse of the fuzzy PID control algorithm is divided into positive and negative parts. The positive universe of discourse corresponds to the temperature of the DFB laser being higher than the preset temperature, and the negative universe of discourse corresponds to the temperature of the DFB laser being lower than the preset temperature. Expanding the universe of discourse can accelerate the response by covering a larger deviation range, while narrowing the universe of discourse can improve the temperature control accuracy of the DFB laser and suppress overshoot and oscillation phenomena.

[0124] Secondly, both a small and large selection of the universe of discourse will affect the control effect. By adding an appropriate scaling factor to the fuzzy PID control, the universe of discourse range can be changed in real time with the error. Therefore, the scaling factor is determined by correcting the temperature rise drift coefficient and temperature drop drift coefficient based on the heat source disturbance value, specifically as follows:

[0125] For each DFB laser in each control cycle, if the heat source interference value is greater than 0, the product of the normalized result of the heat source interference value and the temperature rise drift coefficient is used as the scaling factor of the positive domain in the fuzzy PID control algorithm, and the temperature drop drift coefficient is used as the scaling factor of the negative domain in the fuzzy PID control algorithm.

[0126] If the heat source interference value is less than 0, the product of the normalized result of the absolute value of the heat source interference value and the temperature drop drift coefficient is used as the scaling factor of the negative domain in the fuzzy PID control algorithm, and the temperature rise drift coefficient is used as the scaling factor of the positive domain in the fuzzy PID control algorithm.

[0127] If the heat source interference value is equal to 0, the temperature rise drift coefficient is used as the scaling factor of the positive domain in the fuzzy PID control algorithm, and the temperature drop drift coefficient is used as the scaling factor of the negative domain in the fuzzy PID control algorithm.

[0128] In this embodiment, the sigmoid function is used for normalization. The sigmoid function is a well-known technique and will not be described in detail here.

[0129] It should be noted that the larger the scaling factor of the positive domain of discourse, the stronger the interference from current and the temperature rise of other DFB lasers, and the more likely it is to increase the positive temperature error. To improve the response speed of temperature control for this DFB laser, a larger domain of discourse should be used. Conversely, the smaller the scaling factor of the positive domain of discourse, the less significant the interference from current and the temperature rise of other DFB lasers, and the smaller the subsequent temperature error may be. To improve the accuracy of temperature control for this DFB laser, a smaller domain of discourse should be used. Secondly, the scaling factor of the negative domain of discourse... The larger the scaling factor, the stronger the interference from current and the temperature drop of other DFB lasers, and the more likely it is to increase the reverse temperature error. To improve the response speed of temperature control for this DFB laser, a larger domain of discourse should be used. Conversely, the smaller the scaling factor of the negative domain of discourse, the less significant the interference from current and the temperature drop of other DFB lasers, and the smaller the subsequent temperature error may be. To improve the accuracy of temperature control for this DFB laser, a smaller domain of discourse should be used. Furthermore, the flowchart of the method for obtaining the scaling factor provided in this application embodiment is as follows: Figure 3 As shown.

[0130] Secondly, the fuzzy PID control algorithm takes the system error and its rate of change as input, and uses fuzzy control rules to adjust the proportional gain coefficient Kp, integral gain coefficient Ki, and derivative gain coefficient Kd of the PID controller to adapt to the adaptive requirements of the changing system error and its rate of change on the PID parameters. Therefore, based on the scaling factor, the adjusted universe of discourse is determined, and the temperature of each DFB laser is controlled using the fuzzy PID control algorithm, specifically as follows:

[0131] Calculate the average temperature of each DFB laser at all times during each control cycle, and record it as the actual temperature;

[0132] The difference between the actual temperature of each DFB laser and its corresponding preset temperature in each control cycle is recorded as the temperature deviation.

[0133] Calculate the difference in temperature deviation between each control cycle and the previous control cycle for each DFB laser, and use it as the deviation change rate.

[0134] The preset initial universe of discourse for both the temperature deviation and the rate of change of the deviation is set to [-G, G].

[0135] In this embodiment, the value of G is 6. In other implementation methods, the implementer can set the value according to the actual situation.

[0136] Let α be the scaling factor of the positive domain of the nth DFB laser in each control period.n The scaling factor of the negative domain corresponding to the nth DFB laser in each control cycle is denoted as β. n ;

[0137] The adjusted domain of the temperature deviation and the rate of change of the deviation is [-β]. n ×G,α n ×G];

[0138] Based on the adjusted universe of discourse, the temperature deviation and the rate of change of deviation of each DFB laser in each control cycle are used as inputs to the fuzzy PID control algorithm to control the temperature of each DFB laser in each control cycle.

[0139] It should be noted that the fuzzy PID control algorithm is a well-known technology and will not be elaborated here. Secondly, based on the adjustment values ​​of Kp, Ki, and Kd output by the fuzzy PID control algorithm, the pulse width modulation (PWM) waves with different duty cycles in the DFB laser are changed. The pulse width modulation waves can indirectly regulate the temperature of the DFB laser by controlling the driving power of the thermoelectric cooler. Among them, the PWM wave control of the DFB laser is a well-known technology, and the specific process will not be elaborated here. By changing the domain of discourse, the temperature of the DFB laser is controlled, ensuring that the DFB laser locks the output center wavelength under the complex environmental conditions and long-term operation in the multi-gas TDLAS detector, thus achieving consistent control of the laser spot.

[0140] Based on the same inventive concept as the above method, this application embodiment also provides a beam uniformity control system for a DFB laser, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above-described beam uniformity control methods for a DFB laser.

[0141] It should be understood that, although Figure 1 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0142] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0143] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application, without departing from the content of the technical solution of this application, shall fall within the protection scope of the technical solution of this application.

Claims

1. A method for controlling the beam uniformity of a DFB laser, characterized in that, The method includes the following steps: Acquire the current and temperature of each DFB laser in the multi-gas TDLAS detector at each moment during each control cycle; For each DFB laser in each control cycle, current spikes are obtained based on the deviation of the current difference between adjacent time points; the duration and frequency of continuous occurrence of current spikes are analyzed, as well as the average current level of continuous occurrence of current spikes, and the spike significance of each DFB laser in each control cycle is calculated. Compare the temperature of each DFB laser at each moment in the preset local time period before each control cycle with the preset temperature to obtain the temperature rise time and temperature fall time; analyze the temperature change trend of all temperature rise times and all temperature fall times in the local time period, and combine the burr significance to obtain the temperature rise drift coefficient and temperature fall drift coefficient of each DFB laser in each control cycle. The temperature correlation between each DFB laser and the other DFB lasers is analyzed under each control cycle to obtain the interference heat sources of each DFB laser; combined with the difference of the preset temperature between each DFB laser and different interference heat sources, the heat source interference value of each DFB laser under each control cycle is obtained. Based on the temperature rise drift coefficient and temperature drop drift coefficient, and combined with the heat source interference value, the scaling factors of the positive and negative domains of discourse in the fuzzy control algorithm are determined respectively. Through the fuzzy control algorithm, the temperature of the DFB laser is controlled in real time to control the beam consistency of the DFB laser. The scaling factors for the positive and negative universes of discourse in the fuzzy control algorithm include: For each DFB laser in each control cycle, if the heat source interference value is greater than 0, the scaling factor of the positive domain is the product of the normalized value of the heat source interference value and the temperature rise drift coefficient, and the scaling factor of the negative domain is the temperature drop drift coefficient. If the heat source interference value is less than 0, the scaling factor of the negative domain is the product of the normalized value of the absolute value of the heat source interference value and the temperature drop drift coefficient, and the scaling factor of the positive domain is the temperature rise drift coefficient. If the heat source interference value is equal to 0, the scaling factor of the positive domain is the temperature rise drift coefficient, and the scaling factor of the negative domain is the temperature drop drift coefficient.

2. The method for controlling the beam uniformity of a DFB laser as described in claim 1, characterized in that, A further method for obtaining the current burrs is as follows: Calculate the average current of each DFB laser at all times during each control cycle; The difference in current between each DFB laser at each moment in each control cycle and the previous moment is denoted as the current difference. The moment when the current difference is greater than the average value within each control cycle is selected and recorded as the current spike point.

3. The method for controlling the beam uniformity of a DFB laser as described in claim 1, characterized in that, The calculation of the glitch significance of each DFB laser in each control cycle includes: The times when current spikes occur consecutively within each control cycle are used to form spike intervals. The time length between the upper and lower limits in each glitch interval is recorded as the glitch duration; the average value of the current difference corresponding to all times in each glitch interval is recorded as the glitch amplitude. Calculate the sum of the products of the puncture duration and the puncture amplitude corresponding to all puncture intervals within each control cycle; Statistically analyze the frequency of all current spikes occurring within each control cycle; The spuriousness is the normalized result of the product of the sum and the frequency.

4. The method for controlling the beam uniformity of a DFB laser as described in claim 1, characterized in that, The further process for obtaining the time points of temperature rise and temperature drop is as follows: For each DFB laser, the moment when the temperature is higher than the corresponding preset temperature within the local time period is recorded as the temperature rise moment; the moment when the temperature is lower than the corresponding preset temperature within the local time period is recorded as the temperature drop moment.

5. The method for controlling the beam uniformity of a DFB laser as described in claim 1, characterized in that, The obtained temperature rise drift coefficient and temperature drop drift coefficient of each DFB laser under each control cycle include: Each temperature rise time and each temperature drop time within the local time period is combined with its corresponding temperature to form a two-dimensional array; Linear fitting is performed on the two-dimensional arrays corresponding to all temperature rise times and all temperature fall times within the local time period to obtain the slope of the fitted line, which is denoted as the first slope and the second slope, respectively; positive mapping is performed on the first slope and the second slope, which are denoted as the temperature rise trend value and the temperature fall trend value, respectively. The temperature rise drift coefficient is the product of the burr significance and the temperature rise trend value; The temperature drop drift coefficient is the ratio of the burr significance to the temperature drop trend value.

6. The method for controlling the beam uniformity of a DFB laser as described in claim 1, characterized in that, The process for acquiring each interference heat source of each DFB laser is as follows: The temperature correlation between any two DFB lasers at all times within each control cycle is denoted as the temperature coherence degree; the threshold for dividing the temperature coherence degree between any DFB laser and all other DFB lasers within each control cycle is obtained. The remaining DFB lasers whose temperature compatibility with any DFB laser is greater than the segmentation threshold are denoted as the interfering heat sources of any DFB laser.

7. The method for controlling the beam uniformity of a DFB laser as described in claim 6, characterized in that, The obtained thermal interference value of each DFB laser in each control cycle includes: Calculate the cumulative sum of the temperature coordination between any DFB laser and all other DFB lasers within each control cycle; The proportion of the temperature coordination degree between any DFB laser and each interference source in the summation is used as the temperature interference weight between any DFB laser and each interference source. The difference between the preset temperature corresponding to any DFB laser and the preset temperature corresponding to each interfering heat source is calculated and denoted as the temperature control difference; Based on the temperature interference weight, the temperature control difference between any DFB laser and all interference sources is weighted and summed to obtain the heat source interference value of any DFB laser in each control cycle.

8. The method for controlling the beam uniformity of a DFB laser as described in claim 1, characterized in that, The real-time temperature control of the DFB laser includes: Calculate the average temperature of each DFB laser at all times during each control cycle, and record it as the actual temperature; The difference between the actual temperature of each DFB laser and its corresponding preset temperature in each control cycle is recorded as the temperature deviation; the difference between the temperature deviation of each DFB laser in each control cycle and the previous control cycle is calculated as the deviation change rate. For each DFB laser in each control cycle, the range of the preset initial universe of discourse is adjusted based on the scaling factors of the positive and negative universes of discourse. Based on the adjusted universe of discourse range, the temperature deviation and the rate of change of the deviation are used as inputs to the fuzzy PID control algorithm to control the temperature of each DFB laser in each control cycle in real time.

9. A spot uniformity control system for a DFB laser, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the spot uniformity control method for a DFB laser as described in any one of claims 1-8.

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