CN116203540B - A system and method for correcting laser frequency response - Google Patents
A system and method for correcting laser frequency responseInfo
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- CN116203540B CN116203540B CN202111446910.9A CN202111446910A CN116203540B CN 116203540 B CN116203540 B CN 116203540B CN 202111446910 A CN202111446910 A CN 202111446910A CN 116203540 B CN116203540 B CN 116203540B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/497—Means for monitoring or calibrating
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
- H01S3/0085—Modulating the output, i.e. the laser beam is modulated outside the laser cavity
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
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Abstract
本申请提供了一种激光器频率响应的校正系统和方法，涉及激光器技术领域。该系统包括：依次连接的激光光源模块、信号分束模块、长延时纤、信号合束模块、探测器模块和信号采集与处理模块，其中，激光光源模块调制激光器发出的激光信号的频率时，采用的第一调制信号包括串联的第二调制信号与直流调制信号，长延时纤的长度满足的条件为：T2<τ＝nL/c<T1。基于本申请提供的激光器频率响应的校正系统和方法可以提高激光器实际频率响应信号与理想频率响应信号之间的一致性。
The present application provides a system and method for correcting the frequency response of a laser, relating to the field of laser technology. The system comprises a laser light source module, a signal beam splitting module, a long-delay fiber, a signal beam combining module, a detector module, and a signal acquisition and processing module, all connected in sequence. When the laser light source module modulates the frequency of a laser signal emitted by a laser, the first modulation signal employed comprises a second modulation signal and a DC modulation signal connected in series, and the length of the long-delay fiber satisfies the condition: T 2 <τ = nL/c < T 1 . The system and method for correcting the frequency response of a laser provided in the present application can improve the consistency between the actual frequency response signal of a laser and the ideal frequency response signal.
Description
Technical Field
The present application relates to the field of laser technologies, and in particular, to a system and a method for correcting a frequency response of a laser.
Background
The frequency modulation continuous wave laser radar has the advantages of large measurement range, strong anti-interference capability, high resolution and the like, and is widely applied to the fields of target detection, automatic driving and the like. Taking the field of target detection as an example, a general frequency modulation continuous wave laser radar system transmits a modulated laser signal to a target through a laser, receives an echo signal reflected by the target, and simultaneously calculates information such as the distance, the speed and the like of the target according to a difference frequency signal obtained by mixing the detection signal and the echo signal.
The degree of coincidence between the actual response signal and the ideal signal of the laser has a great influence on the measurement accuracy of the frequency modulation continuous wave laser radar. In practical application, due to the influence of the laser device or the device generating the modulation signal, when the laser is modulated by using the linear modulation signal or the nonlinear modulation signal, the gap between the actual response signal of the laser and the ideal signal is larger, so that the measuring device or system based on the frequency modulation continuous wave laser radar has larger error on the measuring result of the target.
Disclosure of Invention
The embodiment of the application provides a system and a method for correcting the frequency response of a laser, which can improve the consistency between an actual frequency response signal and an ideal frequency response signal of the laser.
The embodiment of the application provides a correction system for laser frequency response, which comprises a laser light source module, a signal beam splitting module, a long delay fiber, a signal beam combining module, a detector module and a signal acquisition and processing module which are sequentially connected, wherein the laser light source module is used for emitting laser signals and modulating the frequencies of the laser signals according to first modulation signals, the first modulation signals comprise second modulation signals and direct current modulation signals which are connected in series;
the length of the long delay fiber meets the following conditions: wherein, T 2 is the period of the second modulation signal, T 1 is the period of the direct current modulation signal, τ is the delay time of the test light, L is the length of the long delay fiber, n is the refractive index of the long delay fiber, and c is the light speed.
The correction system for the frequency response of the laser provided by the application is used for serially connecting a traditional second modulation signal (namely a nonlinear modulation signal or a nonlinear modulation signal) with a direct current modulation signal to be used as a first modulation signal so as to modulate the frequency of a laser signal emitted by the laser. The test light obtained after the laser signal beam splitting is delayed by the long delay fiber, when the delay time is longer than the period of the second modulation signal and is shorter than the period of the direct current modulation signal, the frequency change area in the waveform of the delay light signal and the frequency change area in the waveform of the local oscillation light are not overlapped completely, the amplitude change of the overlapping area caused by interference of the delay light signal and the local oscillation light in the beam combining process is avoided, and the waveform of the actual response of the laser cannot be obtained. The waveform of the mixed frequency optical signal obtained by the difference frequency of the delayed optical signal and the local oscillation optical is closer to the waveform of the actual response of the laser, so that the actual response waveform of the laser can be accurately measured through the mixed frequency optical signal. After the mixed optical signal is converted into an electric signal, the second modulation signal can be adjusted according to the electric signal to obtain an ideal target modulation signal, so that the actual response waveform of the laser is closer to the ideal response waveform, and the consistency of the actual response signal and the ideal signal is improved.
The laser light source module comprises a driving unit, a modulating unit and a laser, wherein the driving unit is respectively connected with the signal acquisition and processing module and the laser, the driving unit is used for driving the laser to send laser signals, the modulating unit is used for generating first modulating signals so as to modulate the frequency of the laser signals, the signal acquisition and processing module is used for controlling the driving unit to adjust the second modulating signals according to the electric signals, and the modulating unit is used for modulating the frequency of the laser signals.
The signal acquisition and processing module comprises a signal acquisition unit and a signal processing unit, the detector module is connected with the signal processing unit through the signal acquisition unit, the signal acquisition unit comprises an acquisition card, the detector module comprises a photoelectric detector, the acquisition card is used for intercepting an electric signal according to the period of a second modulation signal to obtain an effective electric signal, the signal processing unit is used for performing time-frequency conversion processing on the effective electric signal to obtain a time-frequency response signal, and the second modulation signal is adjusted according to the relative error between the time-frequency response signal and a preset target time-frequency response signal to obtain the target modulation signal.
Optionally, the sampling frequency of the acquisition card is greater than 2 times of the frequency modulation bandwidth of the laser, and the bandwidth of the acquisition card and the bandwidth of the photoelectric detector are both greater than the frequency modulation bandwidth of the laser.
Based on the optional mode, when the sampling frequency of the acquisition card is 2 times greater than the frequency modulation bandwidth of the laser, and the bandwidth of the acquisition card is greater than the frequency modulation bandwidth of the laser, the acquisition card can be ensured to completely intercept the effective signal in one period. When the bandwidth of the photoelectric detector is larger than the frequency modulation bandwidth of the laser, the mixed optical signal in a certain frequency range can be converted into an electric signal.
In a second aspect, an embodiment of the present application provides a method for correcting a frequency response of a laser, which is applied to the system for correcting a frequency response of a laser in any one of the first aspect, where the method includes modulating a frequency of a laser signal sent by the laser with a first modulation signal, where the first modulation signal includes a second modulation signal and a direct current modulation signal connected in series, dividing the laser signal into a local oscillation light and a test light, performing delay processing on the test light by a long delay fiber to obtain a corresponding delayed light signal, combining the local oscillation light and the delayed light signal into a mixed light signal, and converting the mixed light signal into an electrical signal, adjusting the second modulation signal according to the electrical signal to obtain a target modulation signal, where the target modulation signal is used to trigger the frequency response of the laser, and a length of the long delay fiber satisfies the following conditions:
wherein, T 2 is the period of the second modulation signal, T 1 is the period of the direct current modulation signal, τ is the delay time of the test light, L is the length of the long delay fiber, n is the refractive index of the long delay fiber, and c is the light speed.
Optionally, the second modulation signal is adjusted according to the electric signal to obtain a target modulation signal, wherein the method comprises the steps of performing time-frequency conversion on the electric signal to obtain a time-frequency response signal, determining a relative error between the time-frequency response signal and a preset target time-frequency response signal, and adjusting the second modulation signal according to the relative error to obtain the target modulation signal.
Optionally, the second modulation signal is adjusted according to the relative error to obtain a target modulation signal, which includes adjusting the second modulation signal according to the relative error when the relative error does not meet a preset condition, updating the first modulation signal based on the adjusted second modulation signal, and returning to execute the step of modulating the frequency of the laser signal sent by the laser by using the first modulation signal until the relative error meets the preset condition, and determining the adjusted second modulation signal as the target modulation signal when the relative error meets the preset condition.
Optionally, determining the relative error between the time-frequency response signal and the preset target time-frequency response signal includes determining the relative error between the time-frequency response signal and the preset target time-frequency response signal according to equation E r＝(Si-St)/St, where E r is the relative error, S i is the time-frequency response signal, and S t is the preset target time-frequency response signal.
Optionally, adjusting the second modulated signal according to the relative error includes adjusting the second modulated signal according to a formula U t+1＝(1+Er*α)*Ut, where U t is the second modulated signal, U t+1 is the adjusted second modulated signal, E r is the relative error, and α is a parameter.
Based on the above alternative, since the difference between the actual time-frequency response signal and the ideal time-frequency response signal of the laser at each time is different, it is necessary to calculate the relative error between the time-frequency response signal at each time and the preset target time-frequency response signal, and adjust each time corresponding to the second modulation signal based on the relative error.
Optionally, performing time-frequency conversion processing on the electric signal to obtain a time-frequency response signal, wherein the time-frequency response signal comprises the steps of intercepting the electric signal according to the period of the second modulation signal to obtain an effective electric signal, and performing time-frequency conversion on the effective electric signal to obtain the time-frequency response signal.
Based on the above alternative, the period of the time-frequency response signal is the same as the period of the second modulation signal, and the waveform of the actual time-frequency response signal of the laser is the same in each period. Therefore, only the effective electric signal in any period is intercepted, the effective electric signal is subjected to time-frequency conversion, and the waveform in any period of the second modulation signal can be adjusted adaptively according to the relative error between the waveform of the time-frequency response signal and the waveform of the preset time-frequency response signal. The whole time-frequency response signal is not required to be compared with a preset time-frequency response signal, so that the operation efficiency is improved, and the rapid correction of the frequency response error of the laser is realized.
In a third aspect, embodiments of the present application provide a computer readable storage medium storing a computer program which, when executed by a processor, implements a method according to any one of the first aspects.
In a fourth aspect, embodiments of the present application provide a computer program product for, when run on a terminal device, causing the terminal device to perform the method of any of the second aspects described above.
It will be appreciated that the advantages of the second aspect to the fourth aspect may be referred to in the description of the advantages of the first aspect and each possible implementation manner of the first aspect, and will not be described in detail herein.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a calibration system for frequency response of a laser according to an embodiment of the present application;
FIG. 2 is a flow chart of a method for calibrating a frequency response of a laser according to an embodiment of the present application;
FIG. 3 is a time-frequency diagram of a linear modulation signal according to an embodiment of the present application;
FIG. 4 is a time-frequency diagram of a nonlinear modulation signal according to an embodiment of the present application;
fig. 5 is a graph of calibration results of a laser frequency response according to an embodiment of the present application.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
The frequency modulation continuous wave laser radar system composed of frequency modulation continuous wave laser radar, laser and other devices can detect the information of the distance, speed and the like of the target. The degree of coincidence between the actual response signal and the ideal signal of the laser has a great influence on the measurement accuracy of the frequency modulation continuous wave laser radar. In practical application, due to the influence of the laser device or the device generating the modulation signal, when the laser is modulated by using the linear modulation signal or the nonlinear modulation signal, the gap between the actual response signal of the laser and the ideal signal is larger, so that the measuring device or system based on the frequency modulation continuous wave laser radar has larger error on the measuring result of the target.
In order to solve the technical problems, the embodiment of the application provides a system and a method for correcting the frequency response of a laser. The frequency of a laser signal emitted by a laser is modulated by a first modulation signal formed by a second modulation signal and a direct current modulation signal, the laser signal is divided into oscillation light and test light, a long delay fiber with a longer length is used for enabling a frequency change area in the waveform of the delay light signal and a frequency change area in the waveform of the oscillation light to be completely not overlapped, the amplitude of an overlapping area caused by interference of the delay light signal and the oscillation light in the beam combining process can be prevented from being changed, the waveform of a mixed frequency light signal obtained by the delay light signal and the oscillation light is enabled to be closer to an actual response waveform of the laser, the second modulation signal is adjusted according to the actual response waveform, an ideal target modulation signal is obtained, the actual response waveform of the laser is enabled to be closer to an ideal response waveform, and the consistency of the actual response signal and the ideal signal is further improved.
The technical scheme of the application is described in detail below with reference to the accompanying drawings. The embodiments described below by referring to the drawings are illustrative and intended to explain the present application and should not be construed as limiting the application.
In one possible implementation manner, as shown in fig. 1, the correction system for the frequency response of the laser provided by the application comprises a laser light source module, a signal beam splitting module, a long delay fiber, a signal beam combining module, a detector module and a signal acquisition and processing module which are connected in sequence.
The laser light source module is used for emitting laser signals and modulating the frequency of the laser signals according to the first modulation signals. The first modulation signal comprises a second modulation signal and a direct current modulation signal connected in series after the second modulation signal. The second modulation signal may be a nonlinear modulation signal or a linear modulation signal.
In one embodiment, a laser light source module may include a driving unit, a modulating unit, and a laser. The driving unit is respectively connected with the signal acquisition and processing module and the laser. The driving unit is used for generating driving current to drive the laser to emit laser signals. The modulation unit is connected with the laser and is used for generating a first modulation signal so as to modulate the frequency of a laser signal emitted by the laser. The signal acquisition and processing module is used for controlling the driving unit to adjust the second modulation signal according to the electric signal.
The signal beam splitting module is used for splitting the laser signal emitted by the laser light source module into vibration light and test light. The local oscillation light is directly transmitted to the signal beam combining module. The test light is subjected to long-delay fiber delay processing with a longer length and then outputs a delay optical signal. The signal beam combining module is used for combining local oscillation light and a delay optical signal output from the long delay fiber into a mixed optical signal.
In the embodiment of the application, the length of the long delay fiber meets the following conditions:
in the formula (1), T 2 is the period of the second modulation signal, T 1 is the period of the direct current modulation signal, τ is the delay time of the test light passing through the long delay fiber, L is the length of the long delay fiber, n is the refractive index of the long delay fiber, and c is the light velocity.
That is, when the delay time of the test light in the long delay fiber is longer than the period of the second modulation signal and shorter than the period of the first modulation signal, the frequency variation region in the waveform of the delayed optical signal and the frequency variation region in the waveform of the local oscillation light are not overlapped completely, so that the change of the amplitude of the overlapping region caused by the interference of the delayed optical signal and the local oscillation light in the beam combining process is avoided, and the waveform of the actual response of the laser cannot be accurately obtained. After the local oscillation light and the test light are processed through the long delay fiber and the signal beam splitting module, the waveform of the mixed frequency optical signal is enabled to be closer to the waveform of the actual response of the laser, the error between the response signal of the laser and the ideal signal can be accurately obtained, and the consistency of the response signal and the ideal signal is improved through adjusting the second modulation signal.
The detector module is used for converting the mixed frequency optical signals output by the signal beam combining module into electric signals. Illustratively, the detector module includes a photodetector, and a single-channel or multi-channel photodetector may be used depending on the number of optical signals input to the photodetector. The signal acquisition and processing module can adjust the second modulation signal according to the electric signal to obtain a target modulation signal, wherein the target modulation signal is used for triggering the frequency response of the laser.
The signal acquisition and processing module comprises a signal acquisition unit and a signal processing unit. The detector module is connected with the signal processing unit through the signal acquisition unit. The signal acquisition unit comprises an acquisition card. The acquisition card can intercept the electric signal according to the period of the second modulation signal to obtain an effective electric signal. The signal processing unit is used for performing time-frequency conversion processing on the effective electric signal to obtain a time-frequency response signal, and adjusting the second modulation signal according to the relative error between the time-frequency response signal and a preset target time-frequency response signal to obtain a target modulation signal.
Further, the sampling frequency of the acquisition card is 2 times greater than the frequency modulation bandwidth of the laser, and the bandwidth of the acquisition card is greater than the frequency modulation bandwidth of the laser, so that the acquisition card can completely intercept effective signals in one period and completely retain information in the electric signals. In addition, when the bandwidth of the photodetector is larger than the frequency modulation bandwidth of the laser, the mixed optical signal in a certain frequency range can be converted into an electric signal.
Based on the same inventive concept, the application also provides a correction method of the laser frequency response, which is applied to the correction system of the laser frequency response provided in the embodiment. Referring to fig. 2, the method for correcting the frequency response of the laser provided by the application comprises the following steps:
S100, modulating the frequency of a laser signal emitted by a laser by using a first modulation signal, wherein the first modulation signal comprises a second modulation signal and a direct current modulation signal which are connected in series.
In one embodiment, the second modulated signal may be a linear modulated signal, such as a sawtooth modulated signal, a triangular modulated signal, or the like. The first modulated signal may be obtained by adding a long-time dc modulated signal after each period (i.e., minimum period) of the triangular modulated signal, assuming that the linear modulated signal is a triangular modulated signal.
In another embodiment, the second signal may also be a non-linear modulated signal, such as a sine wave modulated signal, a periodic pulse modulated signal, or the like. The nonlinear modulation signal is assumed to be a sine wave modulation signal, and a long-time direct current modulation signal is added after each period (i.e., the minimum period) of the sine wave modulation signal to obtain a first modulation signal.
S200, dividing the laser signal into local oscillation light and test light, carrying out delay processing on the test light through a long delay fiber to obtain a corresponding delay light signal, combining the local oscillation light and the delay light signal into a mixed frequency light signal, and converting the mixed frequency light signal into an electric signal.
In order to avoid interference when the local oscillation light and the delayed light signal are combined, the amplitude of the two signals is changed after the waveform change areas overlap, the waveform of the actual response of the laser cannot be accurately obtained, and the delay time used when the test light passes through the long delay fiber is longer than the period of the second modulation signal and shorter than the period of the direct current modulation signal, as shown in the formula (1).
For example, reference is made to the time-frequency plot of a linear modulated signal shown in fig. 3. The first modulation signal includes a triangular wave modulation signal and a direct current modulation signal, and fig. 3 (a) includes a time-frequency curve obtained by time-frequency conversion of the local oscillation optical signal and a time-frequency curve obtained by time-frequency conversion of the delay optical signal, where reference frequencies of the local oscillation optical signal and the delay optical signal are 193THz and bandwidths of the local oscillation optical signal and the delay optical signal are 2GHz, and delay time of the delay optical signal relative to the local oscillation optical signal is τ 1. As can be seen from fig. 3 (a), after the long delay fiber in the embodiment of the present application delays the test light, the area of waveform change in the delayed optical signal can completely avoid the area of waveform change in the local oscillation optical signal. Fig. 3 (b) shows a time-frequency curve of a mixed optical signal obtained by combining the delayed optical signal and the local oscillator optical signal by using the signal beam combining module, where the reference frequency of the mixed optical signal is 0 and the modulation bandwidth is 2GHz.
Reference is made to the time-frequency diagram of the nonlinear modulated signal shown in fig. 4. The first modulation signal includes a sine wave modulation signal and a direct current modulation signal, and fig. 4 (a) includes a time-frequency curve obtained by time-frequency conversion of the local oscillation optical signal and a time-frequency curve obtained by time-frequency conversion of the delay optical signal, wherein reference frequencies of the local oscillation optical signal and the delay optical signal are 193THz and bandwidths of the local oscillation optical signal and the delay optical signal are 2GHz, and delay time of the delay optical signal relative to the local oscillation optical signal is τ 2. As can be seen from fig. 4 (a), after the long delay fiber in the embodiment of the present application delays the test light, the area of waveform change in the delayed optical signal can completely avoid the area of waveform change in the local oscillation optical signal. In fig. 4 (b), after the signal beam combining module is used to combine the delayed optical signal and the local oscillator optical signal, a time-frequency curve of the mixed optical signal is obtained, the reference frequency of the mixed optical signal is 0, the modulation bandwidth is 2GHz, and the waveform of the mixed optical signal is closer to the waveform of the actual response of the laser.
And S300, adjusting the second modulation signal according to the electric signal to obtain a target modulation signal, wherein the target modulation signal is used for triggering the frequency response of the laser.
In one embodiment, after the mixed optical signal is converted into the electrical signal, the triggering time of the triggering signal and the period of the second modulation signal can be obtained to intercept the electrical signal, so as to obtain an effective electrical signal, which is equivalent to intercepting the effective signal in one period. And then, performing time-frequency conversion processing on the intercepted effective signals to obtain time-frequency response signals, and determining the relative error between the time-frequency response signals and the preset target time-frequency response signals. Finally, the second modulation signal is adjusted according to the relative error, and the target modulation signal is obtained.
The period of the time-frequency response signal is the same as the period of the second modulation signal, and the waveform of the actual time-frequency response signal of the laser is the same in each period. Therefore, only the effective electric signal in any period is intercepted, the effective electric signal is subjected to time-frequency conversion, and the waveform in any period of the second modulation signal can be adjusted adaptively according to the relative error between the waveform of the time-frequency response signal and the waveform of the preset time-frequency response signal. The whole time-frequency response signal is not required to be compared with a preset time-frequency response signal, so that the operation efficiency can be improved, and the rapid correction of the laser frequency response error can be realized.
Exemplary, the method for determining the relative error between the time-frequency response signal and the preset target time-frequency response signal is as follows:
Er＝(Si-St)/St (2)
In the formula (2), E r represents a relative error, S i represents a time-frequency response signal, and S t represents a preset target time-frequency response signal.
In the embodiment of the application, in one period, the difference value between the actual time-frequency response signal and the ideal time-frequency response signal of the laser at each moment is different, so that the relative error between the time-frequency response signal at each moment and the preset target time-frequency response signal needs to be calculated, and the corresponding moment of the second modulation signal is adjusted based on the relative error. Specifically, the second modulation signal may be adjusted with a relative error according to equation (3):
Ut+1＝(1+Er*α)*Ut (3)
in the formula (3), U t represents a second modulation signal, U t+1 represents an adjusted second modulation signal, E r represents a relative error, alpha is an adjustment parameter, the speed of adjusting the size of the second modulation signal can be adjusted by setting parameters alpha with different sizes, and t represents the t-th moment in a period. And adjusting the frequency value of the second modulation signal corresponding to each moment in one period to obtain an adjusted second modulation signal. The updated first modulated signal includes the adjusted second modulated signal and the DC modulated signal in series.
In one embodiment, adjusting the second modulation signal according to the relative error to obtain the target modulation signal includes adjusting the second modulation signal according to the relative error when the relative error does not meet the preset condition, updating the first modulation signal based on the adjusted second modulation signal, and returning to execute steps S100-S300 until the relative error meets the preset condition. And if the relative error meets the preset condition, determining the adjusted second modulation signal as a target modulation signal. The target modulation signal may cause the actual frequency response signal of the laser to approach the ideal frequency response signal. For example, the preset condition may be that the relative error approaches 0, or that the relative error is the same value or has a smaller variation amplitude after the second modulation signal is adjusted for multiple times.
Fig. 5 is a graph of a calibration result of a laser frequency response according to an embodiment of the present application. As shown in fig. 5, assuming that the period of the second modulated signal is a triangular wave modulated signal and the period is 10us, the length of the long delay fiber is 11km, the system and method for correcting the frequency response of the laser according to the present application corrects the second modulated signal. The correction result is shown in fig. 5, in which the nonlinear error between the ideal waveform and the actual response waveform is about 20% when the second modulation signal is not corrected, as shown in fig. 5 (a) for the laser frequency response curve. As shown in (b), (c) and (d) of fig. 5, the actual response waveform gradually approaches the ideal waveform every time correction is made. After three corrections, the nonlinear error between the ideal waveform and the actual response waveform is about 0.5% as shown in (d) of fig. 5. The system and the method for correcting the frequency response of the laser can improve the consistency between the actual frequency response signal and the ideal frequency response signal of the laser.
The embodiment of the application also provides a computer readable storage medium, on which a computer program is stored, which when being executed by a processor, implements the method described in the above method embodiment.
The embodiment of the application also provides a computer program product which, when run on a terminal device, causes the terminal device to execute the method described in the embodiment of the method.
The present application may be implemented in whole or in part by a computer program which, when executed by a processor, performs the steps of the method embodiments described above, and which may be embodied in a computer readable storage medium. Wherein the computer program comprises computer program code which may be in source code form, object code form, executable file or some intermediate form etc. The computer readable storage medium may include at least any entity or device capable of carrying computer program code to a terminal device, a recording medium, a computer Memory, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), an electrical carrier signal, a telecommunications signal, and a software distribution medium. Such as a U-disk, removable hard disk, magnetic or optical disk, etc.
Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.
Furthermore, in the present application, unless explicitly defined and limited otherwise, the terms "connected," "connected," and the like are to be construed broadly, and may be mechanically connected or electrically connected, may be directly connected or indirectly connected through intermediaries, and may be connected internally of two elements or may be in interaction with each other, unless explicitly defined otherwise, and the specific meaning of the terms in the present application will be understood to those of ordinary skill in the art in light of the specific circumstances.
The embodiments are only used to illustrate the technical scheme of the present application, but not to limit the technical scheme, and although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical scheme described in the foregoing embodiments may be modified or some or all technical features may be equivalently replaced, and the modification or replacement does not deviate the essence of the corresponding technical scheme from the scope of the technical scheme of the embodiments of the present application.
Claims (10)
1. The system is characterized by comprising a laser light source module, a signal beam splitting module, a long-delay fiber, a signal beam combining module, a detector module and a signal acquisition and processing module which are connected in sequence;
The laser light source module is used for modulating the frequency of a laser signal sent by the laser according to a first modulation signal, wherein the first modulation signal comprises a second modulation signal and a direct current modulation signal which are connected in series;
The signal beam splitting module is used for splitting the laser signal into a local oscillation light and a test light, the test light is subjected to delay processing by the long delay fiber to output a delay light signal, the signal beam combining module is used for combining the local oscillation light and the delay light signal into a mixed frequency light signal, the detector module is used for converting the mixed frequency light signal into an electric signal, the signal acquisition and processing module is used for adjusting the second modulation signal according to the electric signal to obtain a target modulation signal, and the target modulation signal is used for triggering the frequency response of the laser;
The length of the long delay fiber meets the following conditions: wherein T 2 is the period of the second modulation signal, T 1 is the period of the dc modulation signal, τ is the delay time of the test light, L is the length of the long delay fiber, n is the refractive index of the long delay fiber, and c is the light speed.
2. The system of claim 1, wherein the laser light source module comprises a drive unit, a modulation unit, and the laser;
The driving unit is respectively connected with the signal acquisition and processing module and the laser, the driving unit is used for driving the laser to send out laser signals, the modulating unit is used for generating first modulating signals so as to modulate the frequency of the laser signals, and the signal acquisition and processing module is used for controlling the modulating unit to adjust the second modulating signals according to the electric signals.
3. The system according to claim 1 or 2, wherein the signal acquisition and processing module comprises a signal acquisition unit and a signal processing unit, the detector module being connected to the signal processing unit by the signal acquisition unit;
The signal acquisition unit comprises an acquisition card, the detector module comprises a photoelectric detector, the acquisition card is used for intercepting the electric signal according to the period of the second modulation signal to obtain an effective electric signal, the signal processing unit is used for performing time-frequency conversion processing on the effective electric signal to obtain a time-frequency response signal, and the second modulation signal is adjusted according to the relative error between the time-frequency response signal and a preset target time-frequency response signal to obtain the target modulation signal.
4. The system of claim 3, wherein the sampling frequency of the acquisition card is greater than 2 times the frequency modulation bandwidth of the laser, and the bandwidth of the acquisition card and the bandwidth of the photodetector are both greater than the frequency modulation bandwidth of the laser.
5. A method of correcting a laser frequency response as claimed in any one of claims 1 to 4, applied to a system for correcting a laser frequency response, the method comprising:
Modulating the frequency of a laser signal emitted by a laser by using a first modulation signal, wherein the first modulation signal comprises a second modulation signal and a direct current modulation signal which are connected in series;
Dividing the laser signal into local oscillation light and test light, carrying out delay processing on the test light through the long delay fiber to obtain a corresponding delay light signal, combining the local oscillation light and the delay light signal into a mixed frequency light signal, and converting the mixed frequency light signal into an electric signal;
The second modulation signal is adjusted according to the electric signal to obtain a target modulation signal, and the target modulation signal is used for triggering the frequency response of the laser;
The length of the long delay fiber meets the following conditions: wherein T 2 is the period of the second modulation signal, T 1 is the period of the dc modulation signal, τ is the delay time of the test light, L is the length of the long delay fiber, n is the refractive index of the long delay fiber, and c is the light speed.
6. The method of claim 5, wherein adjusting the second modulated signal based on the electrical signal results in a target modulated signal, comprising:
Performing time-frequency conversion processing on the electric signal to obtain a time-frequency response signal;
determining a relative error between the time-frequency response signal and a preset target time-frequency response signal;
and adjusting the second modulation signal according to the relative error to obtain a target modulation signal.
7. The method of claim 6, wherein adjusting the second modulated signal based on the relative error results in a target modulated signal, comprising:
when the relative error does not meet a preset condition, adjusting the second modulation signal according to the relative error, updating the first modulation signal based on the adjusted second modulation signal, and returning to execute the step of modulating the frequency of the laser signal sent by the laser by using the first modulation signal until the relative error meets the preset condition;
and when the relative error meets the preset condition, determining that the adjusted second modulation signal is the target modulation signal.
8. The method of claim 6, wherein said determining a relative error between the time-frequency response signal and a predetermined target time-frequency response signal comprises:
And determining a relative error between the time-frequency response signal and a preset target time-frequency response signal according to a formula E r＝(Si-St)/St, wherein E r is the relative error, S i is the time-frequency response signal, and S t is the preset target time-frequency response signal.
9. The method of claim 6, wherein said adjusting said second modulated signal based on said relative error comprises:
And adjusting the second modulation signal according to a formula U t+1＝(1+Er*α)*Ut, wherein U t is the second modulation signal, U t+1 is the adjusted second modulation signal, E r is the relative error, and alpha is a parameter.
10. The method according to any one of claims 6 to 9, wherein performing time-frequency conversion processing on the electrical signal to obtain a time-frequency response signal comprises:
Intercepting the electric signal according to the period of the second modulation signal to obtain an effective electric signal;
and performing time-frequency conversion on the effective electric signal to obtain a time-frequency response signal.
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| CN112083401A (en) * | 2020-09-16 | 2020-12-15 | 浙江光珀智能科技有限公司 | Nonlinear correction device and method for frequency modulation continuous wave laser radar |
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