Injection locking control method, injection locking control device and laser radar

Abstract

Injection locking control method, injection locking control device and laser radar, the injection locking control method is applied to a laser group, including: obtaining the laser signal output by the slave laser; judging whether the slave laser is injection locked based on the laser signal output by the slave laser; if the result of judging whether the slave laser is injection locked is no, obtaining the continuous loss of lock information of the slave laser; judging whether the slave laser meets the preset correction condition based on the continuous loss of lock information; if the result of judging whether the slave laser meets the correction condition is yes, adjusting the frequency of the slave laser. The above scheme can improve the correction efficiency of injection locking, thereby ensuring the laser detection efficiency of the laser radar.

Description

Technical Field

[0001] The embodiments of this specification relate to the field of laser technology, and in particular to an injection locking control method, an injection locking control device, and a laser radar. Background Art

[0002] In recent years, semiconductor laser technology has developed rapidly, and the performance of semiconductor lasers has been continuously improved, and the application fields of lasers are becoming more and more extensive. For laser radar, in order to ensure detection accuracy and reduce signal noise, single longitudinal mode narrow linewidth lasers are often used.

[0003] However, single longitudinal mode narrow line width lasers can generally only work at low output power and are difficult to work at high output power because lasers are easily affected by interference factors such as mechanical vibration and thermal effects. In addition, optical filters cannot be added to the laser resonant cavity because they will reduce the power efficiency of the laser and cannot work properly at high power.

[0004] In the prior art, in order to obtain a high-power, low-noise laser signal, the laser signal output by a low-noise, low-power laser can be amplified. For example, a high-power fiber amplifier is used. However, the amplifier will generate amplifier noise, which will affect the signal-to-noise ratio to a certain extent and fail to meet the quantum noise standard. If the amplification requirement is very high, a multi-stage amplifier (also called an amplifier chain) is required, which will introduce more amplifier noise; and due to the influence of stimulated Brillouin scattering, the nonlinear problem of the optical fiber is more obvious when the laser is in single longitudinal mode operation.

[0005] Therefore, the solution that relies solely on the amplifier is still not feasible. After research, the researchers applied injection locking technology to the laser, so that the frequency of the laser signal output by the laser follows the frequency of the injected laser signal, avoiding the problem of amplifier noise and improving the signal-to-noise ratio of the laser.

[0006] Specifically, a high-power laser signal is output through a high-power laser, which can be called a slave laser. In order to reduce noise interference, the slave laser can inject a low-noise, low-power laser signal (which can be called an injected laser signal), and the low-power laser that generates the injected laser signal can be called a master laser. After the frequency difference between the master and slave lasers meets certain conditions, the laser signal frequency of the slave laser follows the frequency of the injected laser signal. This phenomenon is injection locking.

[0007] However, due to interference factors such as temperature drift or stress release in the laser, injection locking may fail. After the slave laser loses lock, manual correction is required to re-enter the locked state, which is time-consuming, labor-intensive, and inefficient. Frequent manual correction will affect the normal operation of the laser.

[0008] Therefore, the existing injection locking correction scheme still needs to be improved. Summary of the invention

[0009] In view of this, the embodiments of the present specification provide an injection locking control method, an injection locking control device and a laser radar, which can improve the correction efficiency of injection locking and thereby ensure the laser detection efficiency of the laser radar.

[0010] The embodiment of the present specification provides an injection locking control method, which is applied to a laser group, wherein the laser group includes a master laser and a slave laser, wherein the master laser is suitable for injection locking the slave laser, and the injection locking control method includes the following steps:

[0011] A1) obtaining the laser signal output from the laser;

[0012] A2) determining whether the slave laser is injection locked based on the laser signal output by the slave laser;

[0013] A3) if the judgment result of step A2) is no, obtaining the continuous loss of lock information of the slave laser;

[0014] A4) based on the continuous loss of lock information, determining whether the slave laser meets a preset calibration condition;

[0015] A5) If the judgment result of step A4) is yes, adjusting the frequency of the slave laser.

[0016] The embodiment of this specification also provides an injection locking control device, which is connected to a laser group, wherein the laser group includes a master laser and a slave laser, wherein the master laser is suitable for injection locking the slave laser, and the injection locking control device includes a signal processing module and a control module, wherein:

[0017] The signal processing module is adapted to collect the laser signal output from the slave laser, and transmit the laser signal output from the slave laser to the control module after performing signal processing on the laser signal;

[0018] The control module is adapted to perform signal analysis processing according to the laser signal after signal processing, and to perform corresponding control on the slave laser according to the processing result, wherein the control module comprises:

[0019] An injection locking judgment submodule, adapted to judge whether the slave laser is injection locked according to the laser signal after signal processing;

[0020] a correction judgment submodule, adapted to obtain continuous loss of lock information of the slave laser when the judgment result of the injection locking judgment submodule is no, and judge whether the slave laser meets a preset correction condition based on the continuous loss of lock information;

[0021] The correction processing submodule is adapted to adjust the frequency of the slave laser when the judgment result of the correction judgment submodule is yes.

[0022] The embodiment of this specification also provides a laser radar, including a laser group, a light splitting element and an injection locking control device, wherein:

[0023] The laser group includes a master laser and a slave laser, wherein the master laser is adapted to output an injection laser signal;

[0024] The optical splitter element is adapted to input the injection laser signal into the slave laser and transmit the laser signal output by the slave laser to the injection locking control device;

[0025] The injection locking control device is suitable for controlling the frequency of the slave laser and performing the steps of any one of the above injection locking control methods.

[0026] The injection locking control scheme of the embodiment of this specification is adopted. After determining that the slave laser is not injection locked through the laser signal output by the slave laser, the slave laser is judged whether to perform correction through the acquired continuous loss of lock information and the preset correction conditions, and the frequency of the slave laser is adjusted when the correction conditions are met. It can be seen from the above scheme that the continuous loss of lock information of the slave laser is used to know the length of time the slave laser is in the unlocked state, and the correction is judged in combination with the correction conditions, which can play a buffering effect on the correction of the slave laser, effectively filter the occasional loss of lock of the slave laser, reduce the number of useless injection locking corrections, and reduce the correction workload; and, without changing the frequency of the master laser, the slave laser is used as the correction object, which can reduce the complexity of the correction process and realize automatic correction. Therefore, the injection locking control scheme provided in the embodiment of this specification can improve the correction efficiency of injection locking, thereby ensuring the laser detection efficiency of the laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the drawings required for use in the embodiments of this specification or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1a It is a schematic diagram of a regenerative amplifier in an embodiment of this specification.

[0029] Figure 1b It is a waveform diagram of the output light intensity of a regenerative amplifier in an embodiment of this specification.

[0030] Figure 2 It is a flow chart of an injection locking control method in an embodiment of this specification.

[0031] Figure 3 It is a flow chart of an injection locking determination method in an embodiment of this specification.

[0032] Figure 4 This is a flow chart of another injection locking determination method in an embodiment of this specification.

[0033] Figure 5a It is a schematic diagram of a time domain waveform of a beat frequency signal in an embodiment of this specification.

[0034] Figure 5b yes Figure 5a Schematic diagram of the corresponding envelope.

[0035] Figure 5c yes Figure 5b The corresponding spectrum of the injected laser signal.

[0036] Figure 6a It is a schematic diagram of another beat frequency signal time domain waveform in the embodiments of this specification.

[0037] Figure 6b yes Figure 6a Schematic diagram of the corresponding envelope.

[0038] Figure 6c yes Figure 6b The corresponding spectrum of the injected laser signal.

[0039] Figure 7a It is a schematic diagram of another beat frequency signal time domain waveform in the embodiments of this specification.

[0040] Figure 7b yes Figure 7a Schematic diagram of the corresponding envelope.

[0041] Figure 7c yes Figure 7b The corresponding spectrum of the injected laser signal.

[0042] Figure 8 This is a flow chart of another injection locking determination method in an embodiment of this specification.

[0043] Fig. 9 This is a flow chart of a method for obtaining the current loss of lock parameters in an embodiment of this specification.

[0044] Fig.10 This is a flow chart of a method for obtaining the current lock loss rate in an embodiment of this specification.

[0045] Fig.11 It is a flow chart of a method for obtaining a local sideband symbol in an embodiment of this specification.

[0046] Fig.12 It is a flow chart of another injection locking control method in an embodiment of this specification.

[0047] Fig.13 It is a flow chart of a method for adjusting the frequency of a slave laser in an embodiment of this specification.

[0048] Fig.14 It is a structural block diagram of an injection locking control device in an embodiment of this specification.

[0049] Fig.15 It is a structural block diagram of a laser radar in an embodiment of this specification. DETAILED DESCRIPTION

[0050] In practical applications, injection locking requires a master laser and a corresponding slave laser. The master laser serves as a seed laser to output an injection laser signal, which is then injected into the slave laser through an isolator (to ensure unidirectional transmission of light). The slave laser is injection locked to change its operating characteristics.

[0051] For example, the slave laser can be a continuous wave laser, and its oscillation mode frequency is v (angular frequency is ω), and the output light intensity is I0. If there is an injected laser signal with a frequency of v1 (angular frequency ω1) and a light intensity of I1, the frequency output of the slave laser jumps to v1, and the slave laser enters a locked state.

[0052] refer to Figure 1a As shown in FIG. 1 , for the injected laser signal, the slave laser is equivalent to a regenerative amplifier 10 with two reflectors (i.e., reflectors 11 and 12) placed at both ends of the gain medium. Assuming that the reflectivity of the reflectors 11 and 12 is r, and ε1(t), ε c(t) and ε'1(t) represent the electric field of the incident light of the regenerative amplifier 10, the electric field of the rightward traveling wave at the left mirror end of the cavity, and the electric field of the output light, respectively. Then, according to the boundary conditions, we can obtain:

[0053]

[0054]

[0055] In the above two equations, g(v1), α and L are the gain coefficient, loss coefficient and length of the gain medium respectively; k1 = ω1 / η, η is the refractive index of the gain medium. ε'1(t) is obtained from the above two equations and considering the characteristics that ω1 and ω are very close when injection locking occurs, the output light intensity of the regenerative amplifier 10 is:

[0056]

[0057] When the slave laser operates stably, rexp[g(v)L-αL]=1.

[0058] refer to Figure 1b , which is a waveform diagram of the output light intensity of the regenerative amplifier, wherein the ordinate is the output light intensity I'1 of the regenerative amplifier, and the abscissa is the angular frequency ω1.

[0059] If the angular frequency ω1 of the injected laser signal is equal to the angular frequency ω of the oscillation mode of the slave laser, then I'1→∞. When ω1 is close to ω, the output light intensity I'1 of the regenerative amplifier 10 can exceed the free oscillation output light intensity I0 of the slave laser. This means that the injected laser signal is sharply enhanced in the slave laser, and has an advantage in the process of competing with the free oscillation of the slave laser for high-energy particles. As a result, the free oscillation mode with an angular frequency of ω is suppressed, and the angular frequency of the laser signal output from the slave laser is locked to ω1. After injection locking is achieved by injecting the laser signal, the angular frequency of the slave laser is locked by the injected laser signal and operates synchronously with the master laser.

[0060] If the frequency of the slave laser is changed while the locking state remains unchanged, the corresponding frequency change range is the frequency locking range of the injection locking of the slave laser. Generally speaking, the frequency locking range of injection locking is small, such as a few gigahertz (GHz). The wavelengths between the master and slave lasers cannot have too much error, and the wavelengths need to be strictly matched. However, due to interference factors such as temperature drift or stress release in the laser, the wavelengths of the master and slave lasers may mismatch, resulting in loss of lock.

[0061] Specifically, continue to refer to the above formula for the output light intensity I'1 of the regenerative amplifier and Figure 1bDue to the influence of interference factors such as temperature drift or stress release in the laser, the difference between the angular frequency ω1 of the injected laser signal and the angular frequency ω of the oscillation mode of the slave laser increases, which weakens the output light intensity I'1 of the regenerative amplifier. When the light intensity is lower than the intensity of the free oscillation output, the output of the slave laser deviates from the angular frequency ω1 of the injected laser signal, causing the wavelength mismatch between the master and slave lasers and the slave laser losing lock. At this time, the slave laser freely oscillates and outputs a laser signal with an angular frequency of ω.

[0062] After the slave laser loses lock, it is necessary to manually determine the cause of the loss of lock, and then manually calibrate the wavelengths of the master and slave lasers to match, so that the slave laser enters the locked state again. However, manual calibration is time-consuming and labor-intensive, and inefficient. Frequent manual calibration will affect the normal operation of the laser.

[0063] In summary, how to improve the correction scheme of injection locking has become an urgent problem to be solved by those skilled in the art.

[0064] In view of the above problems, the embodiments of this specification provide an injection locking control method, such as Figure 2 As shown, it is a flow chart of an injection locking control method in an embodiment of the present specification. In the embodiment of the present specification, the injection locking control method can be applied to a laser group, the laser group includes a master laser and a slave laser, the master laser is suitable for injection locking the slave laser, and the injection locking control method may include the following steps:

[0065] A1) Acquiring the laser signal output from the laser.

[0066] In specific implementations, according to the actual application scenarios of the embodiments of this specification, a suitable detection instrument can be used to collect the laser signal output from the laser and generate corresponding data. For example, an interferometer can be used to collect laser signals. The embodiments of this specification do not impose specific restrictions on the type of detection instrument.

[0067] A2) determining whether the slave laser is injection locked based on the laser signal output by the slave laser.

[0068] In a specific implementation, the frequency of the laser signal output by the slave laser can reflect the injection locking state (locked state or unlocked state) of the slave laser, thereby determining whether the slave laser is injection locked.

[0069] A3) If the judgment result of step A2) is no, obtaining the continuous loss of lock information of the slave laser.

[0070] In a specific implementation, the laser signal output by the slave laser can be obtained according to a preset period or sampling time, and after performing a laser signal sampling, the injection locking state of the slave laser can be judged once. If it is determined that the slave laser is in a locked state this time, the continuous loss of lock information can be reset (such as cleared to zero), and after waiting for the slave laser to be determined to be in a lost state again later, the continuous loss of lock information can be recorded again; if it is determined that the slave laser is in a lost state this time, the continuous loss of lock information is updated until it is determined that the slave laser is in a locked state later. In this way, the continuous loss of lock information of the slave laser can be obtained.

[0071] Furthermore, the continuous loss of lock information may include at least one of the continuous loss of lock time and the continuous loss of lock number. The continuous loss of lock time may be the difference between the time when the slave laser is determined to be in the loss of lock state this time and the time when the slave laser is determined to be in the loss of lock state for the first time. The continuous loss of lock number may be the continuous accumulation value of the slave laser being determined to be in the loss of lock state.

[0072] A4) Based on the continuous loss of lock information, determine whether the slave laser meets a preset calibration condition.

[0073] The correction condition may be set according to the continuous lock-out information. For example, if the continuous lock-out information includes the continuous lock-out time, the correction condition may be: whether the correction time threshold is met, if so, the correction condition is met, otherwise the correction condition is not met. For another example, if the continuous lock-out information includes the continuous lock-out times, the correction condition may be: whether the correction times threshold is met, if so, the correction condition is met, otherwise the correction condition is not met.

[0074] A5) If the judgment result of step A4) is yes, adjusting the frequency of the slave laser.

[0075] In a specific implementation, the frequency of the slave laser may be adjusted in at least one of the following ways:

[0076] (1) Adjusting the temperature of the slave laser.

[0077] In a specific implementation, the frequency of the slave laser is inversely proportional to the temperature. Lowering the temperature of the slave laser can increase the frequency of the slave laser, and increasing the temperature of the slave laser can reduce the frequency of the slave laser.

[0078] The temperature of the slave laser can be adjusted by a temperature controller. According to the actual manufacturing process, the temperature controller can be included in the slave laser or connected to the slave laser as an independent device; optionally, the temperature controller can be a thermoelectric cooling device (TEC).

[0079] (2) Adjusting the driving current of the slave laser.

[0080] In a specific implementation, the frequency of the slave laser is proportional to the driving current. Reducing the driving current of the slave laser can reduce the frequency of the slave laser, and increasing the driving current of the slave laser can increase the frequency of the slave laser.

[0081] It can be seen from the above scheme that the duration of the slave laser being in the unlocked state can be known through the continuous unlocking information of the slave laser, and the correction condition can be combined to make a judgment, which can play a buffering effect on the correction of the slave laser, effectively filter the occasional slave laser unlocking phenomenon, reduce the number of useless injection locking corrections, and reduce the correction workload; and, without changing the frequency of the master laser, using the slave laser as the correction object can reduce the complexity of the correction process and realize automatic correction. Therefore, the injection locking control scheme provided in the embodiment of this specification can improve the correction efficiency of injection locking, thereby ensuring the laser detection efficiency of the laser radar.

[0082] It should be noted that the above embodiment only shows the case where the judgment result of step A2) is no. In actual application, there may also be a case where the judgment result of step A2) is yes; similarly, the above embodiment only shows the case where the judgment result of step A4) is yes. In actual application, there may also be a case where the judgment result of step A4) is no. In this regard, the corresponding processing method can be set according to the actual scenario, and the embodiments of this specification do not limit this.

[0083] In an optional example, if Figure 2 As shown, if the judgment result of step A2) is yes, then the process can jump to step A1) to continue acquiring the laser signal output from the laser.

[0084] In another alternative example, if Figure 2 As shown, if the judgment result of step A2) is no, then after executing step A3) to obtain the continuous loss of lock information of the slave laser, the judgment of step A4) is performed. If the judgment result of step A4) is no, jump to step A1) to continue to obtain the laser signal output by the slave laser.

[0085] In practical applications, injection locking can generate high-output-power, low-noise, single-longitudinal-mode, narrow-linewidth optical signals, so it is suitable for LiDAR. However, the above injection locking correction problem will also affect the normal operation of LiDAR, which is explained in detail below through specific application scenarios.

[0086] In a feasible application, in order to obtain a frequency-adjustable laser light source, the frequency modulated continuous wave (FMCW) laser radar needs to modulate the signal of the laser as the light source. Existing modulation methods include direct modulation and external modulation. Among them, direct modulation means: directly controlling the laser through an external signal to adjust the parameters of the laser signal output by the laser (such as light intensity, frequency, etc.). External modulation means: adjusting the parameters of the laser signal output by the laser (such as frequency, intensity, phase, etc.) through a modulator.

[0087] Since FMCW LiDAR requires a high-coherence, high-power frequency-modulated laser light source, direct modulation requires the cooperation of a tunable narrow-linewidth laser. However, the output power of existing tunable narrow-linewidth lasers is low and cannot meet the power requirements of LiDAR. If they are forcibly amplified through optical amplifiers, the signal-to-noise ratio of the light source will be reduced. In addition, there are currently few types of tunable narrow-linewidth lasers on the market, and the models are limited. Tunable narrow-linewidth lasers that meet the power requirements of LiDAR are expensive.

[0088] Injection locking is an auxiliary method of external modulation and is used to amplify the injected optical signal. The laser signal output by the master laser is modulated and input into the slave laser. If the frequency of the modulated laser signal (i.e. the injected laser signal) falls within the frequency locking range, the slave laser is locked, and the frequency of the laser signal output by the slave laser is consistent with the frequency of the injected laser signal; if the frequency of the modulated laser signal (i.e. the injected laser signal) does not fall within the frequency locking range, the slave laser is unlocked, and the frequency of the laser signal output by the slave laser is the free oscillation frequency.

[0089] Injection locking can be used to amplify laser signals with low noise and has extremely strong side mode suppression capabilities. Compared with existing tunable narrow-linewidth lasers, injection locking has lower implementation costs and a simpler structure, making it more suitable for FMCW lidar.

[0090] As can be seen from the above, for FMCW laser radar, injection locking can obtain laser signals with better quality. However, since the frequency of the injected laser signal may change after modulation, and the frequency locking range is small, and the master and slave lasers are easily disturbed by temperature and stress, it is easy to cause the slave laser to lose lock, thereby affecting the operation of the laser radar. The existing injection locking automatic control schemes, such as the optoelectronic phase-locked loop scheme, mostly inject non-tempered laser signals. As for the injection locking control method of linear frequency modulation, there is currently no mature and reliable solution.

[0091] In order to solve the injection locking correction problem in the FMCW laser radar, the injection locking control method provided in the embodiment of this specification can be used. Specifically, in the FMCW laser radar, the laser signal output by the master laser is modulated and input into the slave laser to perform injection locking on the slave laser; through the laser signal output by the slave laser, it is judged whether the slave laser is injection locked, and after determining that the slave laser is not injection locked, it is judged whether the slave laser is corrected through the acquired continuous loss of lock information and the preset correction condition, and the frequency of the slave laser is adjusted when the correction condition is met.

[0092] This can improve the correction efficiency of injection locking, thereby ensuring the laser detection efficiency of the FMCW lidar.

[0093] In a specific implementation, the frequency of the laser signal output by the main laser can be waveform modulated in a sawtooth, triangle, sine, trapezoidal, or other shape. The embodiments of this specification do not impose specific restrictions on the frequency modulation process, frequency modulation method, and change law of the modulated laser signal.

[0094] In practical applications, the frequency modulated laser signal may include a frequency changing region (i.e., a frequency sweep region). In one signal cycle, the frequency sweep region may be divided into an upper frequency sweep region and a lower frequency sweep region according to the order of precedence. Furthermore, the frequency modulated laser signal may also include a frequency unchanged region (i.e., a fixed frequency region).

[0095] For example, within a signal cycle, the frequency of the laser signal modulated by a triangle wave first increases and then decreases, and the time domain waveform of the laser signal may include a frequency sweeping region where the frequency increases (i.e., an upper frequency sweeping region) and a frequency sweeping region where the frequency decreases (i.e., a lower frequency sweeping region).

[0096] For example, within one signal cycle, the frequency of the laser signal modulated by the trapezoidal wave goes through three processes: increasing, remaining fixed, and decreasing. In addition to the sweeping frequency area with increasing frequency (i.e., the upper sweeping frequency area) and the sweeping frequency area with decreasing frequency (i.e., the lower sweeping frequency area), it also includes a fixed frequency area with unchanged frequency.

[0097] Based on this, after the slave laser is locked, the relationship between the frequency of the laser signal output from the laser and time can be determined according to the frequency modulation method of the injected laser signal, and the laser signal output from the laser can include a swept frequency area, and further, can also include a fixed frequency area.

[0098] According to the modulation characteristics of the FMCW laser radar, in order to more intuitively and efficiently determine whether the slave laser is injection locked, the laser signal output by the slave laser may be subjected to beat frequency processing to facilitate injection locking determination.

[0099] Specifically, if Figure 3 FIG. 1 is a flow chart of an injection locking determination method, which may specifically include the following steps:

[0100] A21) dividing the laser signal output from the laser into two paths, and performing delay processing on one of the laser signals.

[0101] A22) performing beat frequency processing on the two laser signals to obtain a beat frequency signal time domain waveform.

[0102] In a specific implementation, the laser signal output from the laser is first delayed, then coupled with the non-delayed laser signal, and the beat frequency of the coupled laser signal is detected to obtain a time domain waveform of the beat frequency signal.

[0103] The frequency sweep signal can be delayed by a delay line, and the delay line can be a transmission line extended by a certain length. Moreover, the extended length of the transmission line can be set according to actual needs, such as the transmission line can be extended by 10m; in addition, the material of the transmission line can be selected according to the type of signal actually transmitted, such as when transmitting an optical signal, an optical fiber material can be used. The embodiments of this specification do not impose specific restrictions on the extended length and material of the transmission line.

[0104] It is understandable that, according to the actual application scenario of the embodiments of this specification, a suitable beat frequency detection method can be selected to perform beat frequency detection on the coupled laser signal, and the embodiments of this specification do not impose any specific restrictions on the implementation process of the beat frequency detection method.

[0105] A23) determining whether the slave laser is injection locked based on the beat signal time domain waveform.

[0106] The vertical axis of the coordinate system where the beat frequency signal time domain waveform is located can represent the amplitude of the beat frequency signal, and the horizontal axis can represent time.

[0107] In a specific implementation, if the slave laser is locked, the frequency of the laser signal output by the slave laser is the same as the modulation frequency of the injected laser signal and changes in a certain shape. At this time, the amplitude of the beat signal obtained changes periodically with time. If the slave laser is unlocked, the laser signal output by the slave laser is a fixed free oscillation frequency. At this time, the beat signal cannot be obtained or the beat signal is extremely weak.

[0108] Therefore, the injection locking state of the slave laser can be monitored by the amplitude of the beat frequency signal time domain waveform, and the slave laser can be found to be locked in time, so as to record the continuous unlocking information more accurately.

[0109] In a specific implementation, in order to improve the efficiency of determining whether the slave laser is injection locked based on the beat frequency signal time domain waveform, as shown in FIG. Figure 4 As shown, the step A23) may specifically include the following steps:

[0110] A231) performing envelope extraction processing on the beat frequency signal time domain waveform to obtain an envelope curve of the beat frequency signal time domain waveform.

[0111] The vertical axis of the coordinate system where the envelope of the beat frequency signal time domain waveform is located can represent the amplitude of the envelope changing with time, and the horizontal axis can represent time.

[0112] In a specific implementation, according to the actual application scenario of the embodiment of this specification, a suitable envelope detection method can be selected to perform envelope extraction processing. For example, the beat frequency signal time domain waveform can be subjected to bandpass filtering and Hilbert transform to obtain the envelope of the beat frequency signal time domain waveform. The embodiment of this specification does not specifically limit the implementation process of envelope extraction processing.

[0113] A232) determines the envelope sub-segment corresponding to the frequency sweep region.

[0114] In combination with the above description of injection locking, for a frequency-modulated injected laser signal, if the laser is locked, the laser outputs a laser signal with a corresponding frequency modulation; otherwise, the laser outputs a laser signal with a free oscillation frequency.

[0115] Therefore, according to the frequency modulation method, the relationship between the waveform and time can be obtained, and then the time information corresponding to the swept frequency area within a signal cycle can be determined. Then, according to the time information, the envelope sub-segment corresponding to the swept frequency area in the envelope can be determined, and then the envelope sub-segment corresponding to the swept frequency area in the envelope can be determined.

[0116] A233) Based on the envelope line, calculate the amplitude threshold line.

[0117] In a specific implementation, taking the trapezoidal wave frequency modulation method as an example, if the slave laser is locked, the laser signal outputted by it has a fixed frequency region and a swept frequency region. After the laser signal outputted by the slave laser is subjected to envelope extraction processing, within a signal cycle, the amplitude of the envelope sub-segment corresponding to the swept frequency region is the maximum amplitude of the laser signal; if the slave laser loses lock, the amplitude of the envelope line will change irregularly, such as the envelope sub-segment corresponding to the swept frequency region has an area where the amplitude is not the maximum amplitude of the laser signal.

[0118] In order to be able to divide the irregularly changing part in the envelope, an amplitude threshold can be determined by the maximum amplitude of the envelope, which can specifically include: obtaining the maximum value in the envelope of the beat frequency signal time domain waveform, and compressing the maximum value in the envelope at a preset ratio, thereby using the compressed value as the amplitude threshold.

[0119] Then, taking the amplitude threshold as the ordinate value, a straight line parallel to the horizontal axis is drawn on the vertical axis of the coordinate system where the envelope line is located to obtain the amplitude threshold line, thereby realizing the division of the envelope line.

[0120] The preset ratio can be set according to the frequency modulation method. Taking the trapezoidal wave frequency modulation method as an example, the ratio can be set according to the proportion of the frequency sweep area in a signal cycle.

[0121] In a specific implementation, the higher the ratio setting, the higher the detection accuracy of the injection locking state of the slave laser. However, considering that the envelope line itself fluctuates in a small range, misjudgment is prone to occur. Therefore, the ratio can be adjusted based on the proportion of the sweep area according to the actual scenario. For example, when the sweep area accounts for 80%, the ratio can be set to 80%, or it can be set to 70%, 90%, etc., thereby obtaining different amplitude thresholds to meet the needs of different scenarios.

[0122] It should be noted that the maximum value may be the maximum amplitude of the envelope within a signal period, or the maximum amplitude of the envelope sub-segment corresponding to the frequency sweep region in the envelope, and the embodiments of this specification do not limit this.

[0123] It is understandable that if the maximum value is the maximum amplitude of the envelope within a signal cycle, there is no necessary order between the above steps A232) and A233). Steps A232) and A233) can be performed in sequence, or they can be performed synchronously. This specification embodiment does not limit this.

[0124] A234) judging whether the slave laser is injection locked based on the positional relationship between the envelope sub-segment and the amplitude threshold line.

[0125] In a specific implementation, the injection locking state can be divided into: locked and unlocked, but this classification is relatively rough. In order to improve the accuracy of injection locking correction, the injection locking state can be further divided into: partial unlocked, completely unlocked, completely locked and abnormally locked according to the collected laser signal output from the laser.

[0126] Among them, the partial unlocking is used to characterize that the laser signal of the slave laser is unlocked at low frequency or high frequency, the complete unlocking is used to characterize that the laser signal of the slave laser is unlocked at both low frequency and high frequency, the complete locking is used to characterize that the laser signal of the slave laser is locked in all frequency bands, and the abnormal locking is used to characterize some frequency anomalies of the laser signal of the slave laser, such as the switching of the slave laser between locking and unlocking caused by frequency instability, and occasional unlocking.

[0127] Thus, according to the positional relationship between the envelope sub-segment and the amplitude threshold line, the injection locking state of the slave laser can be determined, and whether the slave laser is injection locked can be judged according to the injection locking state. Specifically, when the injection locking state of the slave laser is partially unlocked, completely unlocked, and abnormally locked, the result of judging whether the slave laser is injection locked is no; when the injection locking state of the slave laser is completely locked, the result of judging whether the slave laser is injection locked is yes.

[0128] It should be noted that the above embodiment does not limit the execution order of step A231) and step A232). When actually executing the steps of this embodiment, step A231) and step A232) can be executed simultaneously, and step A231) and step A232) can be executed in a set order.

[0129] In a specific implementation, considering the endpoint distortion effect of the Hilbert transform, in order to reduce the impact of these severely distorted areas on subsequent processing, the curve obtained by the Hilbert transform is subjected to de-distortion processing, for example, according to a preset selection rule, the coordinate data of each coordinate point in the selected area is removed. Then, the de-distorted curve is used as the envelope.

[0130] The coordinate data may include: amplitude data (ie, ordinate) and time data (ie, abscissa) of the coordinate point. For example, coordinate points within a preset percentage area around the endpoint are selected, and the corresponding coordinate data are removed.

[0131] In a specific implementation, when determining the injection locking state of the slave laser according to the positional relationship between the envelope sub-line segment and the amplitude threshold line, the following situations may be specifically included according to the type of the injection locking state:

[0132] (1) If there is an envelope sub-segment whose end is below the amplitude threshold line, it is determined that the injection locking state of the slave laser is partially unlocked.

[0133] Among them, the end is measured based on the horizontal axis (i.e. time) of the coordinate system where the envelope line is located, and some sub-segments of corresponding time length are selected from the envelope sub-segments, which may include the endpoints of each envelope sub-segment. The selected time length can be set according to the actual situation.

[0134] For example, Figure 5a As shown, it is a schematic diagram of a beat frequency signal time domain waveform, wherein the solid line is the beat frequency signal time domain waveform G(t) that changes with time within a signal period, and the vertical axis of the coordinate system where the beat frequency signal time domain waveform G(t) is located represents the amplitude of the beat frequency signal that changes with time, and the horizontal axis represents time.

[0135] like Figure 5b Shown Figure 5a Schematic diagram of the envelope corresponding to the time domain waveform of the beat frequency signal, where the solid line is the envelope F(t) that changes with time within a signal period, the vertical axis of the coordinate system where the envelope F(t) is located represents the amplitude of the envelope that changes with time, and the horizontal axis represents time; the dotted line is the amplitude threshold line T1.

[0136] like Figure 5c Shown Figure 5b The spectrum diagram of the injected laser signal corresponding to the middle envelope, where the solid line is the curve of the laser signal frequency f(t) changing with time within a signal cycle, and the two dotted lines are the highest frequency threshold line TH and the lowest frequency threshold line TL of the frequency locking range.

[0137] Combined with reference Figure 5b and Figure 5c According to the time information, it can be determined that the envelope sub-segment corresponding to the frequency sweeping area within a signal cycle is the segment in the area shown in the boxes L1 and L2. In the two envelope sub-segments, one end is located below the amplitude threshold line T1, thereby determining that the injection locking state of the slave laser is partially unlocked, and since the endpoints of the envelope correspond to the low-frequency band of the injected laser signal, that is, the partial frequency of the injected laser signal is lower than the lowest frequency of the frequency locking range, the injection locking state of the slave laser can also be called low-frequency unlocking.

[0138] For example, Figure 6a As shown, it is a schematic diagram of another beat frequency signal time domain waveform, wherein the solid line is the beat frequency signal time domain waveform G(t) that changes with time within a signal period, and the vertical axis of the coordinate system where the beat frequency signal time domain waveform G(t) is located represents the amplitude of the beat frequency signal that changes with time, and the horizontal axis represents time.

[0139] like Figure 6bAs shown, Figure 6a Schematic diagram of the envelope corresponding to the time domain waveform of the beat frequency signal, where the solid line is the envelope F(t) that changes with time within a signal period, the vertical axis of the coordinate system where the envelope F(t) is located represents the amplitude of the envelope that changes with time, and the horizontal axis represents time; the dotted line is the amplitude threshold line T1.

[0140] like Figure 6c Shown Figure 6b The spectrum diagram of the injected laser signal corresponding to the middle envelope, where the solid line is the curve of the laser signal frequency f(t) changing with time within a signal cycle, and the two dotted lines are the highest frequency threshold line TH and the lowest frequency threshold line TL of the frequency locking range.

[0141] Combined with reference Figure 6b and Figure 6c According to the time information, it can be determined that the envelope sub-segment corresponding to the frequency sweeping area within a signal cycle is the segment in the area shown in the boxes L1 and L2. In the two envelope sub-segments, one end is located below the amplitude threshold line T1, thereby determining that the injection locking state of the slave laser is partially unlocked, and since the envelope endpoints correspond to the high frequency band of the injected laser signal, that is, part of the frequency of the injected laser signal is higher than the highest frequency of the frequency locking range, the injection locking state of the slave laser can also be called high-frequency unlocking.

[0142] (2) If there is an envelope sub-segment whose middle portion is below the amplitude threshold line, it is determined that the injection locking state of the slave laser is abnormally locked.

[0143] Among them, the middle part takes the horizontal axis (i.e. time) of the coordinate system where the envelope line is located as the measurement benchmark, and selects some sub-segments of corresponding time length from the envelope sub-segments, which may include the midpoints of each envelope sub-segment. The selected time length can be set according to the actual situation.

[0144] (3) If both ends of the envelope sub-segment are below the amplitude threshold line, it is determined that the injection locking state of the slave laser is completely unlocked.

[0145] For details, please refer to Figure 5a to 5c as well as Figure 6a to Figure 6c , and related descriptions will not be repeated here.

[0146] (4) If none of the above conditions are met, the injection locking state of the slave laser is fully locked.

[0147] For example, Figure 7aAs shown, it is a schematic diagram of another beat frequency signal time domain waveform, wherein the solid line is the beat frequency signal time domain waveform G(t) that changes with time within a signal period, and the vertical axis of the coordinate system where the beat frequency signal time domain waveform G(t) is located represents the amplitude of the beat frequency signal that changes with time, and the horizontal axis represents time.

[0148] like Figure 7b As shown, Figure 7a Schematic diagram of the envelope corresponding to the time domain waveform of the beat frequency signal, where the solid line is the envelope F(t) that changes with time within a signal period, the vertical axis of the coordinate system where the envelope F(t) is located represents the amplitude of the envelope that changes with time, and the horizontal axis represents time; the dotted line is the amplitude threshold line T1.

[0149] like Figure 7c Shown Figure 7b The spectrum diagram of the injected laser signal corresponding to the middle envelope, where the solid line is the curve of the laser signal frequency f(t) changing with time within a signal cycle, and the two dotted lines are the highest frequency threshold line TH and the lowest frequency threshold line TL of the frequency locking range.

[0150] Combined with reference Figure 7b and Figure 7c According to the time information, it can be determined that the envelope sub-segment corresponding to the frequency sweep area within a signal cycle is the segment in the area shown in boxes L1 and L2. In the two envelope sub-segments, no end is below the amplitude threshold line T1, and no middle is below the amplitude threshold line T1. Therefore, it can be determined that the injection locking state of the slave laser is completely locked.

[0151] In a specific implementation, there is coordinate data for each point in the envelope line, and the positional relationship between the envelope sub-segment and the amplitude threshold line can be determined through the position information of each point in the envelope sub-segment.

[0152] Specifically, after obtaining the envelope sub-segment and amplitude threshold line corresponding to a frequency sweep area, based on the amplitude threshold line, the part of the envelope sub-segment below the amplitude threshold line can be obtained to obtain a first segment set, and the part of the envelope sub-segment above the amplitude threshold line can be obtained to obtain a second segment set.

[0153] If the first line segment set is an empty set, it can be concluded that the envelope sub-segments are all above the amplitude threshold line, and the injection locking state of the slave laser is determined to be completely locked. Otherwise, further judgment is made through the preset first unlocking limit point and second unlocking limit point.

[0154] In a specific implementation, the first unlocking limit point and the second unlocking limit point are based on the envelope sub-segment, and the positions of the first unlocking limit point and the second unlocking limit point can be determined by the length of the envelope sub-segment. Specifically, if the segment length of the envelope sub-segment is Len, and the abscissa point of the starting endpoint is a, then the abscissa of the first unlocking limit point can be a+Len*x, where x represents a percentage value, and the abscissa of the second unlocking limit point can be a+Len*(100%-x).

[0155] Among them, the smaller the percentage value, the closer the first unlock limit point is to the starting end point of the envelope sub-segment, the closer the second unlock limit point is to the ending end point of the envelope sub-segment, and the more stringent the determination condition of the laser injection lock state is. Therefore, in actual application, a suitable percentage value can be selected in combination with the application scenario and error redundancy. The embodiments of this specification do not specifically limit the size of the percentage value.

[0156] By determining the positional relationship between the starting endpoint in the first line segment set and the envelope, and determining the positional relationship between the ending endpoint in the first line segment set and the preset second unlocking limit point in the envelope, the injection locking state of the slave laser can be determined. Specifically, it can include:

[0157] (1) If the starting endpoint in the first line segment set is located before the first unlocking limit point, and the ending endpoint in the first line segment set is located before the second unlocking limit point, or if the starting endpoint in the first line segment set is located after the first unlocking limit point, and the ending endpoint in the first line segment set is located after the second unlocking limit point, then after determining that the degree of matching between the line segment length of the first line segment set and the position difference of the endpoints of the first line segment set meets the preset approximate condition, it can be determined that one end of the envelope sub-segment is located below the amplitude threshold line, and the injection locking state of the slave laser is determined to be partially unlocked.

[0158] (2) If the starting endpoint of the first line segment set is located before the first unlocking limit point, and the ending endpoint of the first line segment set is located after the second unlocking limit point, it is necessary to further analyze the two ends of the envelope sub-segment based on the second line segment set, including:

[0159] (2.1) If the second line segment set is an empty set, it can be concluded that both ends of the envelope sub-line segment are located below the amplitude threshold line, and the injection locking state of the slave laser is determined to be completely unlocked.

[0160] (2.2) If the second line segment set is not an empty set, and the ratio of the line segment length of the second line segment set to the envelope sub-line segment meets the preset proportion condition, it can be concluded that both ends of the envelope sub-line segment are located above the amplitude threshold line, and it is determined that the injection locking state of the slave laser is completely locked.

[0161] (3) For other situations other than the above-mentioned parts (1), (2) and (2.1) and (2.2), it can be concluded that the envelope sub-segment has a middle part below the amplitude threshold line, and the injection locking state of the slave laser is determined to be abnormally locked.

[0162] Optionally, the degree of matching can be expressed as a percentage, and the approximate condition can be a percentage threshold, for example, the approximate condition is: the degree of matching reaches 85%, and for another example, the approximate condition is: the degree of matching reaches 100%; in addition, the proportion condition can also be a percentage threshold, for example, the ratio of the length of the line segments of the second line segment set to the envelope sub-segments reaches 80%, and for another example, the ratio of the length of the line segments of the second line segment set to the envelope sub-segments reaches 90%.

[0163] It can be understood that the above embodiment is described by way of example using one envelope sub-segment. When the embodiment is actually applied, there may be multiple envelope sub-segments, and each envelope sub-segment may be processed in parallel or serially in a certain order. The embodiments of this specification do not limit this.

[0164] In a specific implementation, in order to reduce the amount of data injected into the locking state judgment process, an index number can be set for each coordinate point in the envelope, and the coordinate data of each coordinate point can be represented by the index number, and the two-dimensional data can be converted into one-dimensional data, which can reduce the amount of data and improve the processing speed. Among them, the index number can be incremented from 0, or from a preset value (such as 1), and this embodiment of the specification does not limit this.

[0165] In order to facilitate understanding and application by those skilled in the art, the following is a detailed description with reference to embodiments and drawings.

[0166] In one embodiment of the present specification, after obtaining the envelope sub-segment and amplitude threshold line corresponding to a frequency sweep region, as follows: Figure 8 As shown, the following steps are used to determine the injection locking state of the slave laser:

[0167] S001, dividing the envelope sub-segment into two parts by using the amplitude threshold line, respectively obtaining index numbers of the two parts, and obtaining a first index set Ns and a second index set Ng.

[0168] The first index set Ns includes the index numbers of the envelope sub-segments located below the amplitude threshold line; the second index set Ng includes the index numbers of the envelope sub-segments located above the amplitude threshold line.

[0169] Furthermore, the index number of the portion of the envelope sub-segment that overlaps with the amplitude threshold line may belong to the first index set Ns or the second index set Ng, or may not belong to the first index set Ns or the second index set Ng, and this specification does not impose any limitation on this.

[0170] S002: Determine whether the first index set Ns is an empty set.

[0171] S003, if the judgment result of step S002 is yes, then the injection locking state of the slave laser is completely locked, refer to FIG. 7 .

[0172] S004: If the judgment result of step S002 is no, extract the index numbers tl and tr sorted at both ends from the first index set Ns.

[0173] The index numbers in Ns are arranged according to the positions of the corresponding point coordinates in the envelope. tl represents the index number of the starting endpoint of the first index set, and tr represents the index number of the ending endpoint of the first index set.

[0174] S005: Determine the relationship among the preset index number bl of the first unlock limit point, the preset index number br of the second unlock limit point, the first index set Ns, the index number tl of the starting endpoint of the first index set, and the index number tr of the ending endpoint of the first index set.

[0175] Step S005 may specifically include: determining the size relationship between the first unlock limit point bl and the index number tl of the starting endpoint of the first index set; determining the size relationship between the second unlock limit point br and the index number tr of the ending endpoint of the first index set; and determining whether the number of index numbers in the first index set Ns and the degree of matching between |tl-tr| meet a preset approximate condition.

[0176] Among them, |tl-tr| represents the absolute value of the difference between the starting endpoint and the ending endpoint, the number of index numbers in the first index set Ns can represent the segment length of the corresponding envelope sub-segment, and |tl-tr| can represent the endpoint position difference of the first segment set. In addition, the index number bl of the first unlocking limit point and the index number br of the second unlocking limit point can be obtained by the percentage of the maximum index number difference in the envelope sub-segment, such as the maximum index number in the envelope sub-segment is 2500, the minimum index number is 0, the percentage corresponding to the first unlocking limit point is 5%, and the percentage corresponding to the second unlocking limit point is 98%, then the maximum index number difference is 2500-0=2500, the index number bl of the first unlocking limit point can be 2500*5%=125, and the index number br of the second unlocking limit point can be 2500*98%=2450.

[0177] S006: If the index number bl of the first unlock limit point is greater than the index number tl of the starting endpoint of the first index set, the second unlock limit point br is greater than or equal to the index number tr of the ending endpoint of the first index set, and the number of index numbers in the first index set Ns and the matching degree between |tl-tr| meet the preset approximation condition, that is, the first index set Ns is approximate to |tl-tr|, refer to Figure 5a L1 region and Figure 6a In the L2 region, the injection locking state of the slave laser is partially unlocked.

[0178] S007: If the index number bl of the first unlock limit point is less than or equal to the index number tl of the starting endpoint of the first index set, the second unlock limit point br is less than the index number tr of the ending endpoint of the first index set, and the number of index numbers in the first index set Ns and the matching degree between |tl-tr| meet the preset approximation condition, that is, the first index set Ns is approximate to |tl-tr|, refer to Figure 5a Middle L2 area and Figure 6a In the L1 region, the injection locking state of the slave laser is partially unlocked.

[0179] S008: If the index number bl of the first unlock limit point is greater than the index number tl of the starting endpoint of the first index set, and the second unlock limit point br is less than the index number tr of the ending endpoint of the first index set, determine whether the second index set Ng is an empty set.

[0180] S009, if the judgment result of step S008 is yes, then the injection locking state of the slave laser is completely unlocked.

[0181] S010, if the judgment result of step S008 is no, then determine whether the ratio of the number of index numbers in the second index set Ng to the number of index numbers in the envelope sub-segment meets the proportion condition, that is, determine whether the proportion of the locked range in the entire envelope sub-segment reaches the preset percentage threshold.

[0182] S011, if the judgment result of step S010 is yes, the injection locking state of the slave laser is completely locked, refer to FIG. 7;

[0183] S012: If the judgment result of step S010 is no, or it is other than the judgment results of steps S006 to S008, then the injection locking state of the slave laser is abnormally locked.

[0184] By adopting the above scheme, the injection locking state of the slave laser can be accurately obtained according to the positional relationship between the envelope sub-segment and the amplitude threshold line. Then, when it is determined that the slave laser is unlocked, different adjustments can be made according to the injection locking state to obtain a better correction effect.

[0185] In a specific implementation, in order to realize automatic adjustment of the frequency, before the step A4), the following steps may also be included:

[0186] B1) determining the current unlocking parameter of the slave laser based on the time domain waveform of the beat frequency signal.

[0187] In a specific implementation, the loss-of-lock parameter may include: a loss-of-lock rate and a sideband sign, wherein the sideband sign is used to characterize the positivity or negativity of the sideband. If the sideband sign is positive, it indicates that the sideband is a positive sideband, and the positive sideband is a frequency band located upstream of the fundamental wave, such as a +1-order sideband, a +2-order sideband, etc.; if the sideband sign is negative, it indicates that the sideband is a negative sideband, and the negative sideband is a frequency band located downstream of the fundamental wave, such as a -1-order sideband, a -2-order sideband, etc.

[0188] Depending on the timing of acquiring the loss-of-lock parameter, it can be used as the current loss-of-lock parameter or the historical loss-of-lock parameter. In other words, the current loss-of-lock parameter may include: the current loss-of-lock rate and the current sideband symbol, and the historical loss-of-lock parameter may include: the historical loss-of-lock rate and the historical sideband symbol.

[0189] It should be noted that there is no necessary order between the above-mentioned step B1) and steps A1) to A3). The execution order of step B1) and steps A1) to A3) can be set according to actual conditions, and the embodiments of this specification do not limit this.

[0190] Specifically, Fig. 9 As shown, when determining the current unlocking parameter of the slave laser based on the beat frequency signal time domain waveform, the following steps may be included:

[0191] B11) determining the current unlocking rate of the slave laser based on the time domain waveform of the beat frequency signal.

[0192] B12) Obtaining a historical lock loss rate from the historical lock loss parameters of the slave laser, and determining a current sideband symbol of the slave laser based on the current lock loss rate and the historical lock loss rate of the slave laser.

[0193] It should be noted that there is no necessary order between step B11) and step B12).

[0194] In order to facilitate technical personnel to understand and implement, the process of how to obtain the current lock loss rate is described in detail below through drawings and embodiments.

[0195] In a specific implementation, based on the amplitude threshold line, the proportion of the portion of the envelope sub-segment below the amplitude threshold line to the envelope sub-segment can be determined to obtain the current lock-out rate of the envelope sub-segment.

[0196] Specifically, in combination with the relevant description of obtaining the injection locking state, if the first line segment set is an empty set, it can be determined that there is no part of the envelope sub-line segment below the amplitude threshold line, and the current unlocking rate of the envelope sub-line segment can be set to 0; otherwise, by determining the positional relationship between the starting endpoint in the first line segment set and the preset first unlocking limit point in the envelope, and determining the positional relationship between the ending endpoint in the first line segment set and the preset second unlocking limit point in the envelope, the current unlocking rate of the envelope sub-line segment is obtained, which may include:

[0197] (1) If the starting endpoint of the first line segment set is located before the first unlocking limit point, and the ending endpoint of the first line segment set is located before the second unlocking limit point, then after determining that the matching degree between the line segment length of the first line segment set and the position difference of the endpoints of the first line segment set meets the preset approximate condition, the current unlocking rate can be set to

[0198] Among them, SR represents the position information of the end points of the first line segment set in the envelope, and L represents the length of the envelope.

[0199] (2) If the starting endpoint of the first line segment set is located after the first unlock limit point, and the ending endpoint of the first line segment set is located after the second unlock limit point, then after determining that the matching degree between the line segment length of the first line segment set and the position difference of the endpoints of the first line segment set meets the preset approximate condition, the current unlock rate can be set to

[0200] Wherein, SL represents the position information of the starting endpoints of the first line segment set in the envelope.

[0201] (3) If the starting endpoint in the first line segment set is located before the first unlocking limit point, and the ending endpoint in the first line segment set is located after the second unlocking limit point, it is necessary to further analyze the two ends of the envelope sub-segment based on the second line segment set, which may include:

[0202] (3.1) If the second line segment set is an empty set, the current lock-out rate can be set to 1.

[0203] (3.2) If the second line segment set is not an empty set, and the ratio of the line segment length of the second line segment set to the envelope sub-line segment meets the preset proportion condition, the current lock-out rate can be set to 0.

[0204] (4) For other situations other than the above (1) to (3) and (3.1) and (3.2), the current lock loss rate is set to the historical lock loss rate. The historical lock loss rate can be the lock loss rate obtained last time.

[0205] By adopting the above scheme, features are extracted from the beat frequency signal time domain waveform, and the corresponding unlocking rate is obtained according to the features, so as to characterize the proportion of the unlocking time in a cycle, which is convenient for subsequent injection locking correction.

[0206] In a specific implementation, in order to reduce the amount of data injected into the locking state judgment process, an index number can be set for each coordinate point in the envelope, such as Fig.10 As shown, it is a flow chart of a method for obtaining the current lock loss rate, wherein steps S101, S102, S104, S105, S108, and S110 can refer to Figure 8 And related descriptions, the other steps are described as follows:

[0207] S103: If the judgment result of step S102 is yes, the current unlocking rate is 0.

[0208] S106: If the index number bl of the first unlock limit point is greater than the index number tl of the starting endpoint of the first index set, the second unlock limit point br is greater than or equal to the index number tr of the ending endpoint of the first index set, and the number of index numbers in the first index set Ns and the matching degree between |tl-tr| meet the preset approximate condition, that is, the first index set Ns is approximate to |tl-tr|, then the current unlock rate is Wherein, N is the total number of index numbers of the envelope.

[0209] S107: If the index number bl of the first unlock limit point is less than or equal to the index number tl of the starting endpoint of the first index set, the second unlock limit point br is less than the index number tr of the ending endpoint of the first index set, and the number of index numbers in the first index set Ns and the matching degree between |tl-tr| meet the preset approximate condition, that is, the first index set Ns is approximate to |tl-tr|, then the current unlock rate is

[0210] S109: If the judgment result of step S108 is yes, the current unlocking rate is 1.

[0211] S111, if the judgment result of step S110 is no, then a historical lock loss rate may be obtained as the current lock loss rate. The historical lock loss rate may be the lock loss rate obtained last time.

[0212] In order to facilitate technical personnel to understand and implement, the process of how to obtain the local sideband symbol is described in detail below through drawings and embodiments.

[0213] In a specific implementation, in order to prevent the speed-distance decoupling error of the external moving target and the divergence of the locking feedback process, it is necessary to solidify the sideband of the injected laser signal and ensure that the positive and negative properties of the sideband do not change.

[0214] by Figure 5c , Figure 6c and Figure 7c The spectrum diagram of the injected laser signal shown is used as a reference. Within a modulation period (ie, signal period), the frequency curve corresponding to the injection locking signal can be divided into an upper frequency sweep region, a fixed frequency region, and a lower frequency sweep region as time increases.

[0215] If the injection-locked signal is a positive sideband signal, the upper frequency sweep region is a region where the frequency increases, and the lower frequency sweep region is a region where the frequency decreases.

[0216] When the slave laser is completely locked, the frequency curve of the laser signal of the slave laser varying with time is between the highest frequency threshold line TH and the lowest frequency threshold line TL, as shown in Figure 7c shown.

[0217] When the slave laser is partially unlocked, the frequency curve of the laser signal of the slave laser that changes with time is located between the highest frequency threshold line TH and the lowest frequency threshold line TL. According to the relationship between the upper frequency sweep area, the lower frequency sweep area, the lowest frequency threshold line TL, and the highest frequency threshold line TH of the injection locking signal, it can be determined whether the slave laser is high-frequency or low-frequency unlocked. For example, if the ends of the upper frequency sweep area and the lower frequency sweep area are below the lowest frequency threshold line TL, such as Figure 5cAs shown, the slave laser loses lock at low frequency; for another example, the upper frequency sweep region and the lower frequency sweep region have ends located above the highest frequency threshold line TH, such as Figure 6c As shown, the slave laser loses high frequency lock.

[0218] When the slave laser is completely out of lock, the frequency curve of the laser signal of the slave laser varying with time is outside the highest frequency threshold line TH and the lowest frequency threshold line TL.

[0219] Correspondingly, the injection locked signal is a signal of a negative sideband, an upper frequency sweep region thereof is a region where the frequency decreases, and a lower frequency sweep region is a region where the frequency increases.

[0220] When the slave laser is completely locked, the frequency curve of the laser signal of the slave laser varying with time is located between the highest frequency threshold line TH and the lowest frequency threshold line TL.

[0221] When the slave laser is partially unlocked, the frequency curve of the laser signal of the slave laser that changes with time is partially located between the highest frequency threshold line TH and the lowest frequency threshold line TL. According to the relationship between the upper frequency sweep area, the lower frequency sweep area, the lowest frequency threshold line TL, and the highest frequency threshold line TH of the injection locking signal, it can be determined whether the slave laser is high-frequency or low-frequency. For example, if the ends of the upper frequency sweep area and the lower frequency sweep area are located above the highest frequency threshold line TH, the slave laser is high-frequency unlocked; for another example, if the ends of the upper frequency sweep area and the lower frequency sweep area are located below the lowest frequency threshold line TL, the slave laser is low-frequency unlocked.

[0222] When the slave laser is completely out of lock, the frequency curve of the laser signal of the slave laser varying with time is outside the highest frequency threshold line TH and the lowest frequency threshold line TL.

[0223] Based on the above description, it can be known that if the slave laser is partially unlocked, the positive and negative sidebands of the laser signal of the slave laser can be determined according to the unlocked position and the corresponding frequency, thereby determining whether the positive and negative sidebands have changed, that is, the positive and negative sidebands of the laser signal of the slave laser are consistent with the positive and negative sidebands of the injection-locked laser signal. If the slave laser is completely unlocked or completely locked, since the unlocked position cannot be determined, it is impossible to determine the positive and negative sidebands of the laser signal of the slave laser, and further it is impossible to determine whether the positive and negative sidebands have changed.

[0224] It can be seen from this that the sign of the current sideband of the slave laser can characterize the positive or negative nature of the sideband, and can also indirectly characterize the injection locking state of the slave laser.

[0225] Since the highest frequency threshold line TH and the lowest frequency threshold line TL are frequency threshold lines under ideal conditions, and the laser signal from the laser is nonlinear when it is unlocked, it is difficult to judge the sideband sign of the laser signal from the laser through the laser signal from the laser, the highest frequency threshold line TH and the lowest frequency threshold line TL in practical applications. In specific implementation, the positive and negative nature of the sideband can be judged by the current unlocking rate, the historical unlocking rate and the historical frequency correction amount, and then the corresponding sideband sign can be determined. Among them, when the positive and negative nature of the sideband cannot be determined, a special symbol (such as the number 0) can be used to represent the unknown sideband.

[0226] In one possible embodiment, Fig.11 FIG. 1 is a flow chart of a method for obtaining a sideband symbol, which may include:

[0227] S201, obtaining the historical frequency correction value dl_last from the laser.

[0228] The historical frequency correction amount dl_last may be the correction amount adjusted by the slave laser last time.

[0229] S202, determining whether the historical frequency correction value dl_last is 0, that is, determining whether the slave laser was adjusted last time.

[0230] S203: If the judgment result of step S202 is no, obtain the historical lock-out rate R_last.

[0231] S204: Determine the relationship between the current lock-loss rate R and the historical lock-loss rate R_last.

[0232] S205, if the historical loss of lock rate R_last is 0 and the absolute value of the current loss of lock rate R belongs to the interval (0,1), that is, R_last=0 and 0<|R|<1, then obtain the product dl_last*R of the current loss of lock rate R and the historical frequency correction amount dl_last, and the current sideband sign order has the same positive and negative sign as the product dl_last*R. Specifically, if the product is positive, that is, dl_last*R>0, the current sideband sign order is positive, and if the product is negative, that is, dl_last*R<0, the current sideband sign order is negative.

[0233] S206, if the historical loss of lock rate R_last is 1 and the absolute value of the current loss of lock rate R belongs to the interval (0,1), that is, R_last=1 and 0<|R|<1, then obtain the product dl_last*R of the current loss of lock rate R and the historical frequency correction amount dl_last, and the current sideband sign order is opposite to the product dl_last*R. Specifically, if the product is positive, that is, dl_last*R>0, the current sideband sign order is negative, and if the product is negative, that is, dl_last*R<0, the current sideband sign order is positive.

[0234] S207, if the current loss of lock rate R is 1 and the absolute value of the historical loss of lock rate R_last belongs to the interval (0,1), that is, R=1 and 0<|R_last|<1, then the product dl_last*R_last of the historical loss of lock rate R_last and the historical frequency correction amount dl_last is obtained, and the current sideband symbol order has the same positive and negative as the product dl_last*R_last. Specifically, if the product is positive, that is, dl_last*R_last>0, the current sideband symbol order is positive, and if the product is negative, that is, dl_last*R_last<0, the current sideband symbol order is negative.

[0235] S208, if the current loss of lock rate R is 0 and the absolute value of the historical loss of lock rate R_last belongs to the interval (0,1), that is, R=0 and 0<|R_last|<1, then obtain the product dl_last*R_last of the historical loss of lock rate R_last and the historical frequency correction amount dl_last, and the current sideband sign order is opposite to the product dl_last*R_last in terms of positive and negative. Specifically, if the product is positive, that is, dl_last*R_last>0, the current sideband sign order is negative, and if the product is negative, that is, dl_last*R_last<0, the current sideband sign order is positive.

[0236] S209, if the current loss lock rate R is 1 and the historical loss lock rate R_last is 0 or 1, that is, R=1 and R_last=0 or 1, then the current sideband symbol order is 0, that is, the current sideband is unknown.

[0237] S210, if the judgment result of step S202 is yes, or if the historical loss of lock rate R_last is 1 and the current loss of lock rate R is 0 or 1, that is, R_last=1 and R=0 or 1, then the current sideband symbol order is the historical sideband symbol order_last, that is, the current sideband symbol obtained last time.

[0238] By adopting the above scheme, the sideband information of the laser signal output from the laser can be obtained more accurately based on the historical information and the current information, which is beneficial to the subsequent correction processing.

[0239] In a specific implementation, the frequency of the slave laser can be adjusted in different ways according to different injection locking states, thereby increasing the diversity of control schemes and improving control accuracy.

[0240] Specifically, the step A5) may include the following steps:

[0241] A51) If the judgment result of step A4) is yes, and the injection locking state of the slave laser is partially locked, the frequency of the slave laser is adjusted according to the current unlocking parameter.

[0242] In a specific implementation, if the judgment result of step A4) is yes, and the injection locking state of the slave laser is partially locked, the historical unlocking parameters are obtained, the current unlocking parameters are weighted, the current frequency correction amount is determined, and the frequency of the slave laser is adjusted according to the current frequency correction amount.

[0243] For example, the current frequency correction dl=K1*(E2-E1)+K2*E2, where the weight coefficients K1 and K2 are both constants, E1 is the product of the historical loss of lock rate and the historical sideband symbol, and E2 is the product of the current loss of lock rate and the current sideband symbol.

[0244] The weight coefficients K1 and K2 can characterize the importance of E1 and E2 in the frequency correction process. According to the actual application scenario, by adjusting the size of the weight coefficients K1 and K2, the proportion of E1 and E2 in the frequency correction process can be controlled, thereby obtaining a more accurate frequency correction amount. The embodiments of this specification do not specifically limit the size of the weight coefficients K1 and K2.

[0245] A52) If the judgment result of step A4) is yes, and the injection locking state of the slave laser is completely unlocked, the frequency of the slave laser is continuously adjusted based on the preset first scanning correction amount. In other words, the first scanning correction amount is used as the frequency correction amount for this time, and the frequency of the slave laser is continuously adjusted; until the injection locking state of the slave laser meets the preset first state condition.

[0246] Among them, the continuous adjustment method based on the preset first scanning correction amount can be: adding the current frequency of the slave laser and the first scanning correction amount, so that the frequency of the slave laser gradually increases from the current frequency; or, subtracting the current frequency of the slave laser and the first scanning correction amount, so that the frequency of the slave laser gradually decreases from the current frequency.

[0247] In a specific implementation, the first state condition may be: the injection locking state of the slave laser is partially unlocked; or, the first state condition may be: the injection locking state of the slave laser is fully locked.

[0248] A53) If the judgment result of step A4) is yes, and the injection locking state of the slave laser is abnormally locked, then when it is determined that the sideband of the laser signal output by the slave laser is unknown according to the current sideband symbol, the frequency of the slave laser is continuously adjusted based on the preset second scanning correction amount. In other words, the second scanning correction amount is used as the current frequency correction amount to continuously adjust the frequency of the slave laser; until the injection locking state of the slave laser meets the preset second state condition.

[0249] The second scanning correction amount may be smaller than the first scanning correction amount. Furthermore, the continuous adjustment method based on the preset second scanning correction amount may be: the current frequency of the slave laser is added to the second scanning correction amount, so that the frequency of the slave laser gradually increases from the current frequency; or the current frequency of the slave laser is subtracted from the second scanning correction amount, so that the frequency of the slave laser gradually decreases from the current frequency.

[0250] In a specific implementation, the second state condition may be: the injection locking state of the slave laser is partially unlocked, or the injection locking state of the slave laser is completely locked.

[0251] It is understandable that, according to the injection locking state of the slave laser last time, the historical frequency correction amount may be 0 or the last frequency correction amount, the first scanning correction amount, the second scanning correction amount or other correction amounts. This specification embodiment does not limit this.

[0252] In a specific implementation, since the sideband of the laser signal output from the laser is unknown, in order to determine the sideband sign, it can be determined by adjusting the frequency of the slave laser. Specifically, the injection locking control method may also include:

[0253] A6) If the judgment result of step A2) is yes, and when it is determined that the sideband of the laser signal output by the slave laser is unknown according to the current sideband sign, the frequency of the slave laser is continuously adjusted based on a preset third scanning correction amount until the injection locking state of the slave laser meets the preset third state condition.

[0254] The third scanning correction amount may be smaller than the first scanning correction amount, and the third scanning correction amount may be the same as the second scanning correction amount. Furthermore, the continuous adjustment method based on the preset third scanning correction amount may be: the current frequency of the slave laser is added to the third scanning correction amount, so that the frequency of the slave laser gradually increases from the current frequency; or the current frequency of the slave laser is subtracted from the third scanning correction amount, so that the frequency of the slave laser gradually decreases from the current frequency.

[0255] In a specific implementation, the third state condition may be: the injection locking state of the slave laser is partially unlocked, or the injection locking state of the slave laser is completely locked.

[0256] In a specific implementation, the adjustment direction of the slave laser frequency can be determined by the current frequency correction amount. For example, if the current frequency correction amount is positive, the adjustment direction of the slave laser frequency is increasing, and if the current frequency correction amount is negative, the adjustment direction of the slave laser frequency is decreasing.

[0257] In a specific implementation, if at least one of the current unlocking rate or the current sideband symbol is 0, the historical frequency correction amount can be obtained, and the adjustment direction of the slave laser frequency can be determined by the historical frequency correction amount. For example, if the historical frequency correction amount is positive, the adjustment direction of the slave laser frequency is to increase, and if the current frequency correction amount is negative, the adjustment direction of the slave laser frequency is to decrease.

[0258] In a specific implementation, in order to prevent damage to the components in the slave laser, a corresponding allowable range can be set, such as adjusting the temperature of the slave laser within a preset temperature allowable range; or adjusting the drive current of the slave laser within a drive current allowable range. The allowable range can be set according to the specific model of the slave laser, and the embodiments of this specification do not limit this.

[0259] Optionally, if both the temperature allowable range and the driving current allowable range reach limit values ​​(upper limit value or lower limit value), the frequency of the slave laser is reversely adjusted.

[0260] In one embodiment of this specification, if Fig.13 As shown, it is a flow chart of a method for adjusting the laser frequency, combined with Figure 8 , 10~11 and related descriptions, after obtaining the current unlocking rate R, the current sideband symbol order, and the current injection locking state State, the current frequency correction amount dl is determined based on the historical sideband symbol order_last, the historical frequency correction amount dl_last, and the historical unlocking rate R_last, and then, within the allowable temperature range and the allowable drive current range, the current correction amount and the temperature correction amount are allocated according to the current frequency correction amount dl, and finally, the corresponding operation is performed according to the current correction amount and the temperature correction amount.

[0261] In the specific implementation, in order to improve the injection locking correction efficiency, refer to Fig.12 As shown, steps A1 to A5 may refer to the above related description, and the injection locking control method further includes:

[0262] A7) If the judgment result of step A2) is yes, then obtaining the continuous locking information of the slave laser.

[0263] In a specific implementation, the laser signal output by the slave laser can be obtained according to a preset period or sampling time, and after performing a laser signal sampling, the injection locking state of the slave laser can be judged once. If it is determined that the slave laser is in a lost state this time, the continuous locking information can be reset (such as cleared to zero), and after waiting for the slave laser to be determined to be in a locked state again later, the continuous lost lock information can be recorded again; if it is determined that the slave laser is in a locked state this time, the continuous locking information is updated until it is determined that the slave laser is in a lost state later. In this way, the continuous locking information of the slave laser can be obtained.

[0264] Furthermore, the continuous locking information may include at least one of continuous locking time and continuous locking times. The continuous locking time may be the difference between the time when the slave laser is determined to be in a locked state this time and the time when the slave laser is determined to be in a locked state for the first time. The continuous locking times may be the continuous accumulated value of the slave laser being determined to be in a locked state.

[0265] A8) after determining that the slave laser meets a preset update condition based on the continuous locking information, obtaining the current control parameters of the slave laser and updating them as the initial control parameters of the slave laser.

[0266] The current control parameters may include: current temperature parameters and current drive current parameters, and may also include other parameters for controlling the current operation of the slave laser. The initial control parameters may include: initial temperature parameters and initial drive current parameters, and may also include other parameters for controlling the initial operation of the slave laser.

[0267] In addition, the update condition may be set according to the continuous locking information. For example, if the continuous locking information includes the continuous locking time, the update condition may be: whether the update time threshold is met, if so, the update condition is met, otherwise the update condition is not met. For another example, if the continuous locking information includes the continuous locking times, the update condition may be: whether the update times threshold is met, if so, the update condition is met, otherwise the update condition is not met.

[0268] Therefore, compared with the solution in which the initial control parameters remain unchanged, updating the initial control parameters of the slave laser according to the continuous locking time corresponding to the historical control parameters of the slave laser may make the frequency of the reset slave laser closer to the frequency locking range, or may make the frequency of the reset slave laser fall into the frequency locking range, thereby saving the time of injection locking correction and improving the correction efficiency.

[0269] It should be noted that the above embodiment only shows the case where the slave laser meets the preset update conditions. In actual application, there may also be a case where the slave laser does not meet the preset update conditions. In this regard, a corresponding processing method can be set according to the actual scenario. This specification embodiment does not limit this.

[0270] In a specific implementation, some critical states may jump between injection locked and unlocked states, and the injection locked state may be misjudged. In order to reduce the probability of misjudging the injection locked state of the laser, a buffer condition may be set. After determining that the buffer condition is met, subsequent operations can be performed.

[0271] For example, continue to refer to Fig.12 After the step A7) and before the step A8), the method may further include: A9) determining that the continuous locking information meets the buffering condition.

[0272] Specifically, after step A7), if the continuous locking information meets the buffering condition, the continuous loss of lock information is reset, and the update condition judgment of the subsequent step A8) can be performed.

[0273] Therefore, by judging whether the continuous locking information meets the buffering condition, the probability of misjudgment of the injection locking state can be reduced.

[0274] It is understandable that the above embodiment only shows the case where the continuous locking information meets the buffering condition. In actual application, there may also be a case where the continuous locking information does not meet the buffering condition. For this, a corresponding processing method can be set according to the actual scenario. For example, when the continuous locking information does not meet the buffering condition, the continuous loss of lock information is updated, and the correction condition judgment of the subsequent step A4) is performed. This specification embodiment does not limit this.

[0275] In a specific implementation, if the slave laser loses lock for a long time, the slave laser can be reset to avoid the slave laser from losing control and facilitate injection locking correction. Fig.12 As shown, the injection locking control method may further include:

[0276] A10) after determining that the slave laser meets a preset reset condition based on the continuous loss of lock information, initialize the slave laser and the continuous loss of lock information based on initial control parameters of the slave laser.

[0277] In a specific implementation, the reset condition may be set according to the continuous lock-out information. For example, if the continuous lock-out information includes the continuous lock time, the reset condition may be: whether the reset time threshold is met, if so, the reset condition is met, otherwise the reset condition is not met. For another example, if the continuous lock-out information includes the continuous lock times, the reset condition may be: whether the reset times threshold is met, if so, the reset condition is met, otherwise the reset condition is not met.

[0278] In a specific implementation, in order to avoid conflicts between reset and correction, reset conditions and correction conditions with different value intervals may be set, that is, if the reset condition is met, the correction condition will not be met, and if the correction condition is met, the reset condition will not be met.

[0279] It should be noted that the above embodiment only shows the case where the slave laser meets the preset reset condition. In actual application, there may also be a case where the slave laser does not meet the preset reset condition. In this regard, a corresponding processing method can be set according to the actual scenario. This specification embodiment does not limit this.

[0280] It can be understood that the above describes multiple embodiment schemes provided by the embodiments of this specification, and the various optional methods introduced in each embodiment scheme can be combined and cross-referenced with each other without conflict, thereby extending a variety of possible embodiment schemes, which can all be considered as embodiment schemes disclosed and open in this specification.

[0281] This specification also provides an injection locking control device corresponding to the above injection locking control method, which is described in detail below with reference to the accompanying drawings through specific embodiments. It should be noted that the injection locking control device described below can be considered as a functional module required to implement the injection locking control method provided in this specification; the content of the injection locking control device described below can be referenced to the content of the injection locking control method described above.

[0282] In a specific implementation, the injection locking control device provided in this specification is connected to a laser group, wherein the laser group includes a master laser and a slave laser, and the master laser is suitable for injection locking the slave laser, such as Fig.14 As shown, it is a structural block diagram of an injection locking control device in an embodiment of this specification. The injection locking control device 140 may include a signal processing module 141 and a control module 142, wherein:

[0283] The signal processing module 141 is adapted to collect the laser signal output from the slave laser, and transmit the laser signal output from the slave laser to the control module 142 after performing signal processing on the laser signal;

[0284] The control module 142 is adapted to perform signal analysis processing according to the laser signal after signal processing, and to perform corresponding control on the slave laser according to the processing result, wherein the control module 142 includes:

[0285] An injection locking judgment submodule 1421 is adapted to judge whether the slave laser is injection locked according to the laser signal after signal processing;

[0286] The correction judgment submodule 1422 is adapted to obtain continuous loss of lock information of the slave laser when the judgment result of the injection locking judgment submodule is no, and judge whether the slave laser meets the preset correction condition based on the continuous loss of lock information;

[0287] The correction processing submodule 1423 is adapted to adjust the frequency of the slave laser when the judgment result of the correction judgment submodule is yes.

[0288] It can be seen from the above scheme that the duration of the slave laser being in the unlocked state can be known through the continuous unlocking information of the slave laser, and the correction condition can be combined to make a judgment, which can play a buffering effect on the correction of the slave laser, effectively filter the occasional slave laser unlocking phenomenon, reduce the number of useless injection locking corrections, and reduce the correction workload; and, without changing the frequency of the master laser, using the slave laser as the correction object can reduce the complexity of the correction process and realize automatic correction. Therefore, the injection locking control scheme provided in the embodiment of this specification can improve the correction efficiency of injection locking, thereby ensuring the laser detection efficiency of the laser radar.

[0289] In the specific implementation, Fig.14 As shown, the signal processing module 141 may include: a light splitting delay processing submodule 1411 and a beat frequency submodule 1412, wherein:

[0290] The light splitting delay processing submodule 1411 is adapted to split the laser signal output from the laser into two paths, and perform delay processing on one of the laser signals;

[0291] The beat frequency submodule 1412 is adapted to perform beat frequency processing on the two laser signals to obtain a beat frequency signal time domain waveform;

[0292] The calibration judgment submodule 1422 is adapted to judge whether the slave laser is injection locked according to the time domain waveform of the beat frequency signal.

[0293] In the specific implementation, Fig.14 As shown, the injection locking determination submodule 1421 may include:

[0294] The data processing unit 14211 is adapted to perform envelope extraction processing on the beat frequency signal time domain waveform to obtain the envelope of the beat frequency signal time domain waveform, determine the envelope sub-segments corresponding to the frequency sweeping regions, and calculate the amplitude threshold line;

[0295] The injection locking judgment unit 14212 is adapted to judge whether the slave laser is injection locked according to the positional relationship between the envelope sub-segment and the amplitude threshold line.

[0296] In a specific implementation, the injection locking judgment unit 14212 is suitable for determining the injection locking state of the slave laser according to the positional relationship between the envelope sub-segment and the amplitude threshold line, and judging whether the slave laser is injection locked according to the injection locking state, wherein the injection locking state includes: partial loss of lock, abnormal lock, complete loss of lock and complete lock.

[0297] In the specific implementation, Fig.14 As shown, the control module 142 may further include: a current loss of lock parameter acquisition submodule 1424, adapted to determine the current loss of lock parameter of the slave laser according to the beat frequency signal time domain waveform;

[0298] The correction processing submodule 1423 is adapted to adjust the frequency of the slave laser according to the current unlocking parameter when the judgment result of the correction judgment submodule 1422 is yes and the injection locking state of the slave laser is partially locked.

[0299] In the specific implementation, Fig.14 As shown, the control module 142 may further include:

[0300] The update condition judgment submodule 1425 is adapted to obtain the continuous locking information of the slave laser when the judgment result of the injection locking judgment submodule 14213 is yes, and judge whether the slave laser meets the preset update condition according to the continuous locking information;

[0301] The update processing submodule 1426 is adapted to obtain the current control parameters of the slave laser and update them to the initial control parameters of the slave laser.

[0302] In the specific implementation, Fig.14 As shown, the control module 142 may further include:

[0303] A reset condition judgment submodule 1427, adapted to determine whether the slave laser meets a preset reset condition according to the continuous loss of lock information when the judgment result of the injection locking judgment submodule 14213 is no;

[0304] The reset processing submodule 1428 is adapted to initialize the slave laser and the continuous loss of lock information according to the initial control parameters of the slave laser when the judgment result of the reset condition judgment submodule is yes.

[0305] In a specific implementation, the control module 142 may adjust the frequency of the slave laser in at least one of the following ways:

[0306] Adjusting the temperature of the slave laser within an allowable temperature range;

[0307] The driving current of the slave laser is adjusted within the allowable range of the driving current.

[0308] It should be noted that, in practical applications, the injection locking control device can be implemented by hardware, software, or a combination of hardware and software. For example, each module included in the injection locking control device can be implemented using corresponding hardware circuits, devices, modules, etc. Among them, each module included in the injection locking control device can be controlled by the same processing device, or can be executed by different processing devices, and the different processors can be distributed on the same hardware device, or can be distributed on different hardware devices.

[0309] It can be understood that the above describes multiple embodiment schemes provided by the embodiments of this specification, and the various optional methods introduced in each embodiment scheme can be combined and cross-referenced with each other without conflict, thereby extending a variety of possible embodiment schemes, which can all be considered as embodiment schemes disclosed and open in this specification.

[0310] This specification also provides a laser radar that executes the above injection locking control method, which is described in detail below with reference to the accompanying drawings through specific embodiments. It should be noted that the laser radar described below can be considered as a carrier required to implement the injection locking control method provided in this specification; the content of the laser radar described below can be referenced to the content of the injection locking control method described above.

[0311] Reference Fig.15The structure block diagram of a laser radar in the embodiment of this specification is shown in the figure. In the embodiment of this specification, the laser radar 150 may include: a laser group (not shown in the figure), a spectroscopic element 152 and an injection locking control device 153, wherein:

[0312] The laser group includes a master laser 1511 and a slave laser 1512, wherein the master laser 1511 is adapted to output an injection laser signal;

[0313] The light splitting element 152 is adapted to input the injection laser signal into the slave laser 1512, and transmit the laser signal output from the slave laser 1512 to the injection locking control device 153;

[0314] The injection locking control device 153 is adapted to control the frequency of the slave laser 1512 and execute the injection locking control method described in any one of the above embodiments.

[0315] In the specific implementation, continue to refer to Fig.15 The laser radar 150 may further include a modulator 154 , which is located between the main laser 1511 and the spectroscopic element 152 and is suitable for modulating the laser signal output by the main laser 1511 and outputting it to the spectroscopic element 152 .

[0316] In practical applications, the beam splitter element may include at least one of a circulator and a polarization beam splitter (PBS). The modulator is an optical modulator, which may include an electro-optical modulator (EOM), a magneto-optical modulator (MOM), a semiconductor modulator, etc.

[0317] In a specific implementation, the laser signal output from the slave laser can be used for detection. In order not to affect the detection efficiency of the laser radar, the laser signal output from the slave laser can be divided into two paths, one of which is emitted as a detection signal to detect objects around the laser radar; the other is input into the injection locking control device as a feedback signal, so that the injection locking control device can dynamically control the frequency of the slave laser according to the laser signal of the slave laser.

[0318] For example, continue to refer to Fig.15 The spectroscopic element 152 can divide the laser signal output from the laser 1512 into two paths, one path is input into the injection locking control device 153, and the other path is emitted as a detection signal.

[0319] In the specific implementation, Fig.15As shown, the injection locking control device 153 may include an interferometer 1531, a data processor 1532 and a controller 1533, wherein:

[0320] The interferometer 1531 is adapted to divide the laser signal transmitted by the beam splitter 152 into two paths, and perform delay processing on one of the laser signals, and perform beat frequency processing on the two laser signals to obtain a beat frequency signal;

[0321] The data processor 1532 is adapted to perform signal analysis processing on the beat frequency signal;

[0322] The controller 1533 is adapted to control the slave laser accordingly according to the processing result of the data processor 1532 .

[0323] In the specific implementation, continue to refer to Fig.15 The interferometer 1531 may include: a first coupler 15311, a transmission line 15312, a delay line 15313, a second coupler 15314 and a detector 15315.

[0324] The laser signal transmitted by the optical splitter 152 is divided into two paths through the first coupler 15311, one path is transmitted to the second coupler 15314 through the transmission line 15312, and the other path is transmitted to the second coupler 15314 through the delay line 15313. The second coupler 15314 couples the two laser signals to obtain a coupled laser signal. The detector 15315 detects the coupled laser signal, obtains a beat frequency signal and transmits it to the data processor 1532. The delay line 15313 can refer to the description of the above-mentioned relevant parts, which will not be repeated here.

[0325] In a specific implementation, the data processor can sample the beat frequency signal to obtain a beat frequency signal time domain waveform, and determine whether the slave laser is injection locked this time through the beat frequency signal time domain waveform, and after determining that the slave laser is unlocked, calculate the frequency correction amount of the slave laser this time, and transmit it to the controller, and the controller adjusts the frequency of the slave laser according to the correction amount this time. For details, please refer to the above-mentioned related content, which will not be repeated here.

[0326] In the specific implementation, continue to refer to Fig.15 , the controller 1533 can adjust the frequency of the slave laser 1512 by adjusting the temperature of the slave laser within the temperature allowable range. Specifically, the controller 1533 can adjust the temperature of the slave laser 1512 through the temperature controller 15A, and the temperature controller 15A can be included in the slave laser 1512, or can be connected to the slave laser 1512 as an independent device, and this embodiment of the specification does not limit this.

[0327] In a specific implementation, the data processor and controller can be implemented by processing chips such as a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or by an ASIC (Application Specific Integrated Circuit) or one or more integrated circuits configured to implement the embodiments of this specification.

[0328] In practical applications, the laser radar in the above embodiment may be a FMCW laser radar.

[0329] The embodiments of the present specification also provide a computer-readable storage medium on which computer instructions are stored. When the computer instructions are executed, the steps of the injection locking control method described in any of the above embodiments of the present specification can be executed.

[0330] The computer-readable storage medium may be any suitable readable storage medium such as an optical disk, a mechanical hard disk, a solid-state hard disk, etc. The instructions stored on the computer-readable storage medium execute the steps of the injection locking control method described in any of the above embodiments, and the details may refer to the above embodiments and will not be repeated here.

[0331] The computer-readable storage medium may include, for example, any suitable type of memory unit, memory device, memory item, memory medium, storage device, storage item, storage medium and / or storage unit, such as memory, removable or non-removable medium, erasable or non-erasable medium, writable or rewritable medium, digital or analog medium, hard disk, floppy disk, compact disk read-only memory (CD-ROM), compact disk recordable (CD-R), compact disk rewritable (CD-RW), optical disk, magnetic medium, magneto-optical medium, removable memory cards or disks, various types of digital versatile discs (DVDs), magnetic tapes, cassettes, etc.

[0332] Computer instructions may include any suitable type of code, e.g., source code, compiled code, interpreted code, executable code, static code, dynamic code, encrypted code, etc., implemented using any suitable high-level, low-level, object-oriented, visual, compiled and / or interpreted programming language.

[0333] It should be noted that the terms "first", "second", etc. in the embodiments of this specification are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined by the terms "first", "second", etc. may explicitly or implicitly include one or more of the features. Moreover, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or express importance.

[0334] In addition, in the embodiments of this specification, terms such as "satisfy", "exceed", and "reach" can be understood as different logical comparison relationships according to actual application scenarios, such as "greater than", "greater than or equal to", "less than", and "less than or equal to".

[0335] It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the specification described herein are capable of operation in sequences other than those illustrated or described herein.

[0336] Although the embodiments of this specification are disclosed as above, the embodiments of this specification are not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of this specification. Therefore, the protection scope of the embodiments of this specification shall be subject to the scope defined by the claims.

Claims

1. An injection locking control method, applied to a laser group, wherein the laser group includes a master laser and a slave laser, wherein the master laser is suitable for injection locking the slave laser, and wherein: The injection locking control method comprises the following steps: A1) obtaining the laser signal output from the laser; A2) determining whether the slave laser is injection locked based on the laser signal output by the slave laser; A3) if the judgment result of step A2) is no, obtaining the continuous loss of lock information of the slave laser; A4) based on the continuous loss of lock information, determining whether the slave laser meets a preset calibration condition; A5) If the judgment result of step A4) is yes, adjusting the frequency of the slave laser.

2. The injection locking control method according to claim 1, characterized in that: The laser signal output by the master laser is modulated and then input into the slave laser to injection lock the slave laser; the step A2) comprises the following steps: A21) dividing the laser signal output from the laser into two paths, and performing delay processing on the laser signal of one path; A22) performing beat frequency processing on the two laser signals to obtain a beat frequency signal time domain waveform; A23) determining whether the slave laser is injection locked based on the beat signal time domain waveform.

3. The injection locking control method according to claim 2, characterized in that: The step A23) comprises the following steps: A231) performing envelope extraction processing on the beat frequency signal time domain waveform to obtain an envelope curve of the beat frequency signal time domain waveform; A232) determining an envelope sub-segment corresponding to the frequency sweep region; A233) calculating an amplitude threshold line based on the envelope line; A234) judging whether the slave laser is injection locked based on the positional relationship between the envelope sub-segment and the amplitude threshold line.

4. The injection locking control method according to claim 3, characterized in that: The calculating amplitude threshold line comprises: The maximum value in the envelope of the beat frequency signal time domain waveform is obtained, and the amplitude threshold is obtained by compressing it at a preset ratio.

5. The injection locking control method according to claim 3, characterized in that: The step A234) comprises: According to the positional relationship between the envelope sub-segment and the amplitude threshold line, the injection locking state of the slave laser is determined, and according to the injection locking state, it is judged whether the slave laser is injection locked, wherein the injection locking state includes: partial loss of lock, abnormal lock, complete loss of lock and complete lock.

6. The injection locking control method according to claim 5, characterized in that: The step of determining the injection locking state of the slave laser according to the positional relationship between the envelope sub-line segment and the amplitude threshold line comprises: If there is an envelope sub-segment whose end is below the amplitude threshold line, it is determined that the injection locking state of the slave laser is partially unlocked; If there is an envelope sub-segment whose middle portion is below the amplitude threshold line, determining that the injection locking state of the slave laser is abnormally locked; If both ends of the envelope sub-segment are below the amplitude threshold line, it is determined that the injection locking state of the slave laser is completely unlocked; Otherwise, the injection locking state of the slave laser is completely locked.

7. The injection locking control method according to claim 5, characterized in that: Before step A4), the method further comprises the following steps: B1) determining the current unlocking parameter of the slave laser based on the beat frequency signal time domain waveform; The step A5) comprises the following steps: A51) If the judgment result of step A4) is yes, and the injection locking state of the slave laser is partially locked, the frequency of the slave laser is adjusted according to the current unlocking parameter.

8. The injection locking control method according to claim 7, characterized in that: The step B1) comprises the following steps: B11) determining the current unlocking rate of the slave laser based on the beat frequency signal time domain waveform; B12) Obtaining a historical lock loss rate from the historical lock loss parameters of the slave laser, and determining a current sideband symbol of the slave laser based on the current lock loss rate and the historical lock loss rate of the slave laser.

9. The injection locking control method according to claim 8, characterized in that: The step B11) comprises: Based on the amplitude threshold line, the proportion of the portion of the envelope sub-segment located below the amplitude threshold line to the envelope sub-segment is determined to obtain the current loss of lock rate of the envelope sub-segment.

10. The injection locking control method according to any one of claims 7 to 9, characterized in that: The step A51) comprises: If the judgment result of step A4) is yes, and the injection locking state of the slave laser is partially locked, the historical unlocking parameters are obtained, the current unlocking parameters are weighted, the current frequency correction amount is determined, and the frequency of the slave laser is adjusted according to the current frequency correction amount.

11. The injection locking control method according to any one of claims 7 to 9, characterized in that: The step A5) further comprises the following steps: A52) If the judgment result of step A4) is yes, and the injection locking state of the slave laser is completely unlocked, then based on a preset first scanning correction amount, the frequency of the slave laser is continuously adjusted until the injection locking state of the slave laser meets the preset first state condition.

12. The injection locking control method according to claim 8 or 9, characterized in that: The step A5) further comprises the following steps: A53) If the judgment result of step A4) is yes, and the injection locking state of the slave laser is abnormally locked, then when it is determined that the sideband of the laser signal output by the slave laser is unknown according to the current sideband symbol, the frequency of the slave laser is continuously adjusted based on a preset second scanning correction amount until the injection locking state of the slave laser meets the preset second state condition.

13. The injection locking control method according to any one of claims 8 to 9, characterized in that: Also includes: A6) If the judgment result of step A2) is yes, and when it is determined that the sideband of the laser signal output by the slave laser is unknown according to the current sideband sign, the frequency of the slave laser is continuously adjusted based on a preset third scanning correction amount until the injection locking state of the slave laser meets the preset third state condition.

14. The injection locking control method according to any one of claims 1 to 9, characterized in that: The following steps are also included: A7) if the determination result of step A2) is yes, obtaining the continuous locking information of the slave laser; A8) after determining that the slave laser meets a preset update condition based on the continuous locking information, obtaining the current control parameters of the slave laser and updating them as the initial control parameters of the slave laser.

15. The injection locking control method according to claim 14, characterized in that: After step A7) and before step A8), the method further includes: A9) Determine that the continuous locking information meets the buffering condition.

16. The injection locking control method according to any one of claims 1 to 9, characterized in that: If the judgment result of step A2) is no, the following steps are also included: A10) after determining that the slave laser meets a preset reset condition based on the continuous loss of lock information, initialize the slave laser and the continuous loss of lock information based on initial control parameters of the slave laser.

17. The injection locking control method according to any one of claims 1 to 9, characterized in that: The adjusting the frequency of the slave laser comprises at least one of the following: Adjusting the temperature of the slave laser within an allowable temperature range; The driving current of the slave laser is adjusted within the allowable range of the driving current.

18. An injection locking control device, connected to a laser group, the laser group comprising a master laser and a slave laser, the master laser being suitable for injection locking the slave laser, characterized in that: The injection locking control device comprises a signal processing module and a control module, wherein: The signal processing module is adapted to collect the laser signal output from the slave laser, and transmit the laser signal output from the slave laser to the control module after performing signal processing on the laser signal; The control module is adapted to perform signal analysis processing according to the laser signal after signal processing, and to perform corresponding control on the slave laser according to the processing result, wherein the control module comprises: An injection locking judgment submodule, adapted to judge whether the slave laser is injection locked according to the laser signal after signal processing; a correction judgment submodule, adapted to obtain continuous loss of lock information of the slave laser when the judgment result of the injection locking judgment submodule is no, and judge whether the slave laser meets a preset correction condition based on the continuous loss of lock information; The correction processing submodule is adapted to adjust the frequency of the slave laser when the judgment result of the correction judgment submodule is yes.

19. The injection locking control device according to claim 18, characterized in that: The signal processing module includes: a light splitting delay processing submodule and a beat frequency submodule, wherein: The light splitting delay processing submodule is adapted to split the laser signal output from the laser into two paths, and perform delay processing on one of the laser signals; The beat frequency submodule is suitable for performing beat frequency processing on the two laser signals to obtain a beat frequency signal time domain waveform; The calibration judgment submodule is adapted to judge whether the slave laser is injection locked according to the time domain waveform of the beat frequency signal.

20. The injection locking control device according to claim 19, characterized in that: The injection locking judgment submodule includes: A data processing unit, adapted to perform envelope extraction processing on the beat frequency signal time domain waveform to obtain the envelope of the beat frequency signal time domain waveform, determine the envelope sub-segment corresponding to the frequency sweep region, and calculate the amplitude threshold line; The injection locking judgment unit is adapted to judge whether the slave laser is injection locked according to the positional relationship between the envelope sub-line segment and the amplitude threshold line.

21. The injection locking control device according to claim 20, characterized in that: The injection locking judgment unit is suitable for determining the injection locking state of the slave laser according to the positional relationship between the envelope sub-segment and the amplitude threshold line, and judging whether the slave laser is injection locked according to the injection locking state, wherein the injection locking state includes: partial loss of lock, abnormal lock, complete loss of lock and complete lock.

22. The injection locking control device according to claim 21, characterized in that: The control module further comprises: a current loss of lock parameter acquisition submodule, adapted to determine the current loss of lock parameter of the slave laser according to the beat frequency signal time domain waveform; The correction processing submodule is adapted to adjust the frequency of the slave laser according to the current loss of lock parameter when the judgment result of the correction judgment submodule is yes and the injection locking state of the slave laser is partially locked.

23. The injection locking control device according to claim 18, characterized in that: The control module also includes: An update condition judgment submodule, adapted to obtain continuous locking information of the slave laser when the judgment result of the injection locking judgment submodule is yes, and judge whether the slave laser meets the preset update condition according to the continuous locking information; The update processing submodule is adapted to obtain the current control parameters of the slave laser and update them to the initial control parameters of the slave laser.

24. The injection locking control device according to claim 18, characterized in that: The control module also includes: a reset condition judgment submodule, adapted to determine whether the slave laser meets a preset reset condition according to the continuous loss of lock information when the judgment result of the injection locking judgment submodule is no; The reset processing submodule is adapted to initialize the slave laser and the continuous loss of lock information according to the initial control parameters of the slave laser when the judgment result of the reset condition judgment submodule is yes.

25. The injection locking control device according to any one of claims 18 to 24, characterized in that: The control module is adapted to adjust the frequency of the slave laser in at least one of the following ways: Adjusting the temperature of the slave laser within an allowable temperature range; The driving current of the slave laser is adjusted within the allowable range of the driving current.

26. A laser radar, characterized in that: It includes a laser group, a beam splitter and an injection locking control device, wherein: The laser group includes a master laser and a slave laser, wherein the master laser is adapted to output an injection laser signal; The optical splitter element is adapted to input the injection laser signal into the slave laser and transmit the laser signal output by the slave laser to the injection locking control device; The injection locking control device is suitable for controlling the frequency of the slave laser and executing the injection locking control method according to any one of claims 1-14.

27. The laser radar according to claim 26, characterized in that: The injection locking control device comprises: an interferometer, a data processor and a controller, wherein: The interferometer is adapted to divide the laser signal transmitted by the beam splitter into two paths, and to perform delay processing on one of the laser signals, and to perform beat frequency processing on the two laser signals to obtain a beat frequency signal; The data processor is suitable for performing signal analysis processing on the beat frequency signal; The controller is adapted to control the slave laser accordingly according to the processing result of the data processor.

28. The laser radar according to claim 26, characterized in that: The laser radar also includes a modulator, which is located between the main laser and the spectroscopic element and is suitable for modulating the laser signal output by the main laser and then outputting it to the spectroscopic element.

29. The laser radar according to claim 28, characterized in that: The laser radar is a FMCW laser radar.

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