Acousto-optic modulator output pulse waveform arbitrary regulation and control method

Abstract

The invention discloses an acousto-optic modulator output pulse waveform arbitrary regulation and control method, which comprises the following steps: sending a radio frequency signal to an acousto-optic modulator, sampling modulated pulses output by the acousto-optic modulator, amplitude values corresponding to each frequency and driving voltage combination are obtained, a two-dimensional matrix is formed by the amplitude values, and the position of each amplitude value in the two-dimensional matrix is represented by the magnitude of the frequency and the driving voltage of the amplitude value; searching an element closest to the amplitude of the pulse from the two-dimensional matrix according to the frequency of each pulse in the target pulse, determining a driving voltage corresponding to the element, and placing the driving voltage of each frequency pulse in a driving voltage array; and determining a driving signal provided for the acousto-optic modulator according to the amplitude normalization linear frequency modulation driving signal and the driving voltage array. According to the invention, the output pulse of the acousto-optic modulator can be accurately and efficiently modulated into any waveform.

Description

Technical Field

[0001] The present invention belongs to the field of acousto-optic modulation, and particularly relates to a method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator. Background Art

[0002] Acousto-optic modulation is an external modulation technique. An acousto-optic device that controls the intensity change of a laser beam is usually called an acousto-optic modulator. The acousto-optic modulator has different responsivities to driving signals of different frequencies, and this response is non-linear. Especially, the farther the driving signal is from the center frequency of the acousto-optic modulator, the lower the responsivity of the acousto-optic modulator, which will cause distortion to the modulated pulse output by the acousto-optic modulator. Summary of the Invention

[0003] The present invention provides a method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator to solve the problem that the modulated pulse output by the acousto-optic modulator has waveform distortion due to the different responsivities of the acousto-optic modulator to driving signals of different frequencies.

[0004] According to the first aspect of the embodiments of the present invention, a method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator is provided, including:

[0005] Step S100: Sequentially send each frequency pulse in the radio frequency signal to the acousto-optic modulator. At least one of the frequency and the driving voltage between any two frequency pulses in the radio frequency signal is different. The acousto-optic modulator performs acousto-optic modulation based on each frequency pulse, outputs a modulated pulse, samples the modulated pulse to obtain an amplitude corresponding to each combination of frequency and driving voltage, thereby obtaining a two-dimensional matrix composed of each amplitude, where the position of each amplitude element in the two-dimensional matrix is characterized by the magnitudes of its corresponding frequency and driving voltage;

[0006] Step S200: For each frequency pulse in the target pulse, find the element in the two-dimensional matrix that is closest to the amplitude of the pulse according to the frequency of the pulse, determine the driving voltage corresponding to the element, and place the driving voltages of each frequency pulse at the corresponding positions in the driving voltage array according to the frequency magnitude;

[0007] Step S300: Determine the driving signal provided to the acousto-optic modulator when the acousto-optic modulator modulates and outputs the target pulse according to the amplitude-normalized linear frequency modulation driving signal and the driving voltage array.

[0008] Optionally, the step S100 specifically includes:

[0009] Step S111: Generate a radio frequency signal according to the changed driving voltage. The radio frequency signal is composed of multiple different frequency pulses, and the voltage of each frequency pulse is the changed driving voltage;

[0010] Step S112: Sequentially send pulses of different frequencies to the acousto-optic modulator. The acousto-optic modulator performs acousto-optic modulation based on each frequency pulse, outputs a modulated time-domain pulse, sequentially collects the time-domain pulse, transforms the collected time-domain pulse into a frequency spectrum signal, obtains the amplitudes of the pulses of different frequencies under the changed driving voltage according to the frequency spectrum signal. The amplitudes obtained under the changed driving voltage form a column vector or a row vector in the two-dimensional matrix, and the position of each amplitude element in the column vector or the row vector is characterized by the magnitude of its corresponding frequency and driving voltage;

[0011] Step S113: Determine whether all changes in the driving voltage have been completed. If so, obtain the two-dimensional matrix composed of each column vector or row vector. Otherwise, continue to change the driving voltage and return to execute Step S111.

[0012] Optionally, Step S100 specifically includes:

[0013] Step S121: Generate a radio frequency signal composed of pulses of different frequencies, where for each frequency pulse, its driving voltage is changed multiple times;

[0014] Step S122: For the corresponding frequency pulse, sequentially send the pulses with different driving voltages at this frequency to the acousto-optic modulator. The acousto-optic modulator performs acousto-optic modulation based on each pulse with different driving voltages and the same frequency, outputs a modulated time-domain pulse, sequentially collects the time-domain pulse, transforms the collected time-domain pulse into a frequency spectrum signal, obtains the amplitudes of the pulses with different driving voltages at this frequency according to the frequency spectrum signal. The amplitudes obtained at this frequency form a row vector or a column vector in the two-dimensional matrix, and the position of each amplitude element in the row vector or the column vector is characterized by the magnitude of its corresponding frequency and driving voltage;

[0015] Step S123: Determine whether all frequency pulses in the radio frequency signal have completed the operation of Step S122. If so, obtain the two-dimensional matrix composed of each row vector or column vector. Otherwise, for the next frequency pulse, return to execute Step S122.

[0016] Optionally, the radio frequency signal is a stepped frequency-shifted radio frequency signal, and the pulse widths of its pulses of different frequencies are equal, and the time intervals between any two adjacent pulses of different frequencies are equal.

[0017] Optionally, the expression of the stepped frequency-shifted radio frequency signal RF(t) is:

[0018]

[0019] where N represents the number of pulses of different frequencies in the stepped frequency-shifted radio frequency signal, V represents the driving voltage, T pThe pulse width represents the pulse widths of each different frequency pulse, T represents the time interval between any two adjacent different frequency pulses, f0+(i - 1)Δf represents the pulse frequency, and (N - 1)Δf = B a , B a represents the bandwidth of the radio frequency signal. Both N and i are integers, and Δf represents the stepped frequency shift amount.

[0020] Optionally, obtaining the amplitudes of each different frequency pulse at the changed driving voltage according to the spectrum signal in step S112 includes: for each frequency pulse, representing the frequency of the pulse as f0 + f i , determining the index round(f0 + f i / f p ) of the frequency pulse, and obtaining the amplitude corresponding to the frequency pulse from the spectrum signal according to the index, where f0 represents the initial frequency of the radio frequency signal, f i represents the difference between the pulse frequency and the initial frequency, and f p represents the spectrum signal resolution, and round() is a rounding integer function.

[0021] Optionally, step S200 specifically includes:

[0022] Step S210: Represent the amplitudes of each frequency pulse in the target pulse by a one - dimensional array, and the position of each amplitude in the one - dimensional array is characterized by its corresponding frequency; the size of the one - dimensional array is N, the size of the two - dimensional matrix is N×M or M×N, N represents the number of pulse frequencies, M represents the number of changes in the driving voltage, and both N and M are integers greater than 1; when the number of pulse frequencies of the target pulse is less than the number of frequencies of the radio frequency signal, set the amplitude at the corresponding position in the one - dimensional array to zero;

[0023] Step S220: For each position with a non - zero amplitude in the one - dimensional array, determine the row vector or column vector in the two - dimensional matrix where the frequency corresponding to this position is located, find the element in the row vector or column vector that is closest to the amplitude corresponding to this position, determine the driving voltage corresponding to this element in the two - dimensional matrix, and place the determined driving voltages of each frequency pulse at the corresponding positions in the driving voltage array according to the frequency magnitude. The size of the driving voltage array is M. When the number of pulse frequencies of the target pulse is less than the number of frequencies of the radio frequency signal, set the amplitude at the corresponding position in the driving voltage array to zero.

[0024] Optionally, step S300 specifically includes:

[0025] Step S310: Determine the amplitude - normalized linear frequency modulation driving signal according to the bandwidth of the radio frequency signal and the bandwidth of the target pulse, and determine the number of sampling points of the amplitude - normalized linear frequency modulation driving signal according to the bandwidth of the target pulse and the pulse sampling rate;

[0026] Step S320: Interpolate the drive voltage array according to the number of sampling points, so that the number of amplitude values in the drive voltage array is equal to the number of sampling points;

[0027] Step S330: Multiply the amplitude-normalized linear frequency modulation drive signal and the drive voltage array element by element to obtain the drive signal provided to the acousto-optic modulator when the acousto-optic modulator generates the target pulse.

[0028] Optionally, in step S310, the amplitude-normalized linear frequency modulation drive signal S1 is expressed as:

[0029] S1 = cos{2πf0t + πkt 2}

[0030] where f0 represents the initial frequency of the radio frequency signal, k = B a / T a , B a represents the bandwidth of the radio frequency signal, T a represents the bandwidth of the target pulse; the number of sampling points P a of the amplitude-normalized linear frequency modulation drive signal S1 is:

[0031] P a = T a *f d , f d represents the pulse sampling rate.

[0032] Optionally, the larger the number N of frequencies in the two-dimensional matrix, the more accurate the correspondence between frequency and amplitude; the larger the number M of drive voltages in the two-dimensional matrix, the more accurate the correspondence between drive voltage and amplitude; the more accurate the correspondence between frequency and amplitude, the more accurate the correspondence between drive voltage and amplitude, the more accurate the drive signal obtained based on the two-dimensional matrix, and the more precise the shape of the modulated pulse output by the acousto-optic modulator based on the drive signal;

[0033] The wider the pulse width of the frequency pulse in the radio frequency signal, the higher the accuracy of the amplitude corresponding to the obtained frequency pulse during the formation of the two-dimensional matrix, and during the determination of the drive signal, according to the pulse frequency and amplitude in the target pulse, the amplitude element found from the two-dimensional matrix is closer to the pulse amplitude in the target pulse, so that the obtained drive signal is more accurate, and the shape of the modulated pulse output by the acousto-optic modulator is also more precise.

[0034] The beneficial effects of the present invention are:

[0035] 1. In the present invention, each frequency pulse in the radio frequency signal is sequentially sent to the acousto-optic modulator, such that at least one of the frequency and the driving voltage between any two frequency pulses is different. After the acousto-optic modulator performs acousto-optic modulation based on each frequency pulse, the modulated pulses output by the acousto-optic modulator are sampled, and thus the amplitude corresponding to each combination of frequency and driving voltage can be obtained. After obtaining the corresponding relationship between the frequency, the driving voltage, and the amplitude, when the frequency and the amplitude of the target pulse to be output by the acousto-optic modulator are known, the driving voltage of the radio frequency signal can be determined according to this corresponding relationship. Since the frequency of the target pulse is the same as that of the radio frequency signal, a driving signal with the corresponding frequency and driving voltage can be obtained. The acousto-optic modulator performs acousto-optic modulation based on this driving signal, and thus target pulses of any waveform can be output. Since the acousto-optic modulator has different responsivities to optical signals of different frequencies, the shape of the modulated pulses output by the acousto-optic modulator will be distorted. The present invention compensates for this shape distortion, improving the accuracy of arbitrary waveform regulation. When storing the corresponding relationship between the frequency, the driving voltage, and the amplitude, the present invention uses the form of a two-dimensional matrix. The amplitudes constitute the elements in the two-dimensional matrix, and the position of each amplitude element is characterized by the magnitude of the corresponding frequency and driving voltage. Thus, it is convenient to search for the driving voltage based on the frequency and amplitude of the target pulse, thereby greatly improving the waveform regulation efficiency. After obtaining the driving voltages of each frequency pulse in the target pulse, the present invention places the driving voltages at the corresponding positions in the driving voltage data group according to the frequency magnitude. In this way, it is convenient to quickly establish the correspondence between the amplitude-normalized linear frequency modulation driving signal and this driving voltage array, thereby further improving the waveform regulation efficiency and accuracy.

[0036] 2. The present invention uses a stepped frequency shift radio frequency signal as the radio frequency signal required for forming the two-dimensional matrix, and makes the pulse widths of its different frequency pulses equal, and the time intervals between any two adjacent different frequency pulses equal. This can facilitate the resolution and analysis of each pulse with different frequencies and driving voltages, thereby improving the accuracy of two-dimensional matrix formation. In addition, the frequency difference between adjacent elements in the two-dimensional matrix is equal, which can reduce the determination error of the driving voltage when determining the driving voltage according to the frequency and amplitude in the target pulse.

[0037] 3. The present invention expands the size of the one-dimensional array composed of the amplitudes of each frequency pulse in the target pulse to be equal to the number N of pulse frequencies in the two-dimensional matrix. Thus, each time when searching for the row vector or column vector corresponding to the frequency in the two-dimensional matrix according to the frequency in the target pulse, there is no need to perform frequency comparison, but only position indexing is required, which can improve the regulation efficiency. When the present invention determines the driving signal provided to the acousto-optic modulator based on the amplitude-normalized linear frequency modulation driving signal and the driving voltage array, it is necessary to ensure the corresponding relationship between the amplitude-normalized linear frequency modulation driving signal and the driving voltage array. The present invention expands the size of the driving voltage array determined according to the frequency and amplitude of the target pulse to be equal to the number M of driving voltages in the two-dimensional matrix. When ensuring the corresponding relationship between the amplitude-normalized linear frequency modulation driving signal and the driving voltage array, there is no need to preprocess the amplitude-normalized linear frequency modulation driving signal, which can further improve the regulation efficiency;

[0038] 4. When the present invention determines the driving signal provided to the acousto-optic modulator based on the amplitude-normalized linear frequency modulation driving signal and the driving voltage array, the pulse sampling rate is considered, which can ensure the corresponding relationship between the amplitude-normalized linear frequency modulation driving signal and the driving voltage array. And before the present invention performs interpolation processing on the driving voltage array according to the sampling rate, it first expands the size of the driving voltage array to be equal to the number M of driving voltages in the two-dimensional matrix, which can further ensure the corresponding relationship between the amplitude-normalized linear frequency modulation driving signal and the driving voltage array, thereby improving the regulation accuracy. Description of the Drawings

[0039] Figure 1 is a flowchart of an embodiment of the method for arbitrarily regulating the output pulse waveform of the acousto-optic modulator of the present invention;

[0040] Figure 2 is a schematic structural diagram of an embodiment of the system for arbitrarily regulating the output pulse waveform of the acousto-optic modulator of the present invention;

[0041] Figure 3 is a schematic diagram of the time-domain waveform and spectrum of the modulated pulse collected by the present invention;

[0042] Figure 4 is a schematic waveform diagram of the stepped frequency shift radio frequency signal of the present invention;

[0043] Figure 5 is a schematic diagram of the two-dimensional matrix of the present invention. Detailed Embodiments

[0044] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and make the above-mentioned objects, features, and advantages of the embodiments of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0045] In the description of the present invention, unless otherwise specified and defined, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two components. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific situations.

[0046] See Figure 1 , which is a flowchart of an embodiment of the method for arbitrarily regulating the output pulse waveform of the acousto-optic modulator of the present invention. The method may include the following steps:

[0047] Step S100: Sequentially send each frequency pulse in the radio frequency signal to the acousto-optic modulator. At least one of the frequency and the driving voltage between any two frequency pulses in the radio frequency signal is different. The acousto-optic modulator performs acousto-optic modulation based on each frequency pulse and outputs a modulated pulse. Sample the modulated pulse to obtain the amplitude corresponding to each combination of frequency and driving voltage, thereby obtaining a two-dimensional matrix composed of each amplitude. The position of each amplitude element in the two-dimensional matrix is characterized by the magnitudes of its corresponding frequency and driving voltage, and then execute step S200.

[0048] In this embodiment, the system for implementing the method of the present invention can be as Figure 2 shown. The system may include a laser, a beam splitter, an arbitrary waveform generator, a driving amplifier, an acousto-optic modulator, an attenuator, a coupler, a balanced detector, a data collector, and a trigger unit. The laser is respectively connected to the optical signal input end of the acousto-optic modulator and the second input end of the coupler through the beam splitter. The output end of the arbitrary waveform generator is connected to the driving signal input end of the acousto-optic modulator through the driving amplifier. The output end of the acousto-optic modulator is connected to the first input end of the coupler through the attenuator. The output end of the attenuator is connected to the data collector through the balanced detector. The trigger unit is respectively connected to the control ends of the arbitrary waveform generator and the data collector.

[0049] The laser divides the laser signal it generates into two paths through an optical splitter. One path is transmitted to an acousto-optic modulator, and the other path is transmitted to a coupler. An arbitrary waveform generator generates a radio frequency signal and sends the radio frequency signal to a driver amplifier. The driver amplifier amplifies the power of the radio frequency signal and sends the power-amplified radio frequency signal to the acousto-optic modulator. The acousto-optic modulator performs acousto-optic modulation on the laser signal based on the radio frequency signal and outputs a modulated pulse. The modulated pulse is transmitted to the coupler after its power is reduced by the attenuator. The modulated pulse with reduced power and the laser signal undergo beat frequency at the coupler. The beat frequency signal is transmitted to the balanced detector, and the balanced detector converts the beat frequency signal into an electrical signal. The data acquisition device samples the electrical signal. The trigger unit is used to control the synchronization of the output of the arbitrary waveform generator and the sampling of the data acquisition device. Among them, the laser can be a narrow linewidth laser.

[0050] In the first example, the present invention changes the driving voltage multiple times. After each change in the driving voltage, a series of pulses with different frequencies are generated at the driving voltage. After multiple changes in the driving voltage are completed, a radio frequency signal is obtained. The step S100 may specifically include:

[0051] Step S111: Generate a radio frequency signal according to the changed driving voltage. The radio frequency signal is composed of multiple pulses with different frequencies, and the voltage of each frequency pulse is the changed driving voltage.

[0052] Step S112: Send the pulses with different frequencies to the acousto-optic modulator in sequence. The acousto-optic modulator performs acousto-optic modulation based on each frequency pulse and outputs a modulated time-domain pulse. The time-domain pulse is collected in sequence, and the collected time-domain pulse is transformed into a frequency spectrum signal. As Figure 3 shown, the amplitudes of the pulses with different frequencies at the changed driving voltage are obtained according to the frequency spectrum signal. The amplitudes obtained at the changed driving voltage form a column vector or a row vector in a two-dimensional matrix. The position of each amplitude element in the column vector or the row vector is characterized by the magnitude of its corresponding frequency and driving voltage.

[0053] Step S113: Determine whether all changes in the driving voltage are completed. If so, obtain a two-dimensional matrix composed of each column vector or row vector. Otherwise, continue to change the driving voltage and return to execute step S111.

[0054] Among them, obtaining the amplitudes of the pulses with different frequencies at the changed driving voltage according to the frequency spectrum signal in step S112 may include: For each frequency pulse, represent the frequency of the pulse as f0 + f i , and determine the index of the frequency pulse round(f0 + f i / f p), obtaining the amplitude corresponding to the frequency pulse from the spectrum signal according to the index, where f0 represents the initial frequency of the radio frequency signal, f i represents the difference between the pulse frequency and the initial frequency, and f p represents the spectrum signal resolution, and round() is a rounding function.

[0055] In the second example, for each frequency pulse, the present invention changes its driving voltage. After the driving voltage of the frequency pulse is changed, the operation of changing the driving voltage of the next frequency pulse is performed. After all the driving voltage change operations of the frequency pulses are completed, a radio frequency signal is obtained. The step S100 may specifically include:

[0056] Step S121, generating a radio frequency signal composed of different frequency pulses, where for each frequency pulse, its driving voltage is changed multiple times;

[0057] Step S122, for the corresponding frequency pulse, sequentially sending the pulses with different driving voltages at this frequency to the acousto-optic modulator. The acousto-optic modulator performs acousto-optic modulation based on each pulse with different driving voltages and the same frequency, outputs the modulated time-domain pulse, sequentially collects the time-domain pulse, transforms the collected time-domain pulse into a spectrum signal, obtains the amplitudes of the pulses with different driving voltages at this frequency according to the spectrum signal, and the obtained amplitudes at this frequency form a row vector or a column vector in the two-dimensional matrix. The position of each amplitude element in the row vector or column vector is characterized by the corresponding frequency and the magnitude of the driving voltage;

[0058] Step S123, determining whether all the frequency pulses in the radio frequency signal have completed the operation of step S122. If so, a two-dimensional matrix composed of each row vector or column vector is obtained. Otherwise, for the next frequency pulse, return to execute step S122.

[0059] In this embodiment, the radio frequency signal may be a stepped frequency-shifted radio frequency signal, the pulse widths of its different frequency pulses are equal, and the time intervals between any two adjacent different frequency pulses are equal. The expression of the stepped frequency-shifted radio frequency signal RF(t) may be:

[0060]

[0061] where N represents the number of different frequency pulses in the stepped frequency-shifted radio frequency signal, V represents the driving voltage, T p represents the pulse width of each different frequency pulse, T represents the time interval between any two adjacent different frequency pulses, f0+(i - 1)Δf represents the pulse frequency, and (N - 1)Δf = B z , B arepresents the bandwidth of the radio frequency signal, both N and i are integers, and Δf represents the step frequency shift amount. Among them, the change amount of the driving voltage each time can also be the same.

[0062] The waveform diagram of the stepped frequency shift radio frequency signal can be as Figure 4 shown. Suppose the number of pulse frequencies in the radio frequency signal is N, and the number of changes in the driving voltage is M. Then the size of the two-dimensional matrix is N×M or M×N. Taking the size of the two-dimensional matrix as N×M as an example, as Figure 5 shown, its row vector represents the amplitude of the modulated pulse output by the acousto-optic modulator under the same pulse frequency and different driving voltages, and the column vector represents the amplitude of the modulated pulse output by the acousto-optic modulator under different pulse frequencies and the same driving voltage. The changes in the pulse frequency and the magnitude of the driving voltage can be as Figure 5 indicated by the arrows in, and of course, other sequences of changes can also be adopted. The present invention uses a stepped frequency shift radio frequency signal as the radio frequency signal required to form a two-dimensional matrix, and makes the pulse widths of each pulse with different frequencies equal, and the time intervals between any two adjacent pulses with different frequencies equal, which can facilitate the resolution and analysis of each pulse with different frequencies and driving voltages, thereby improving the accuracy of forming the two-dimensional matrix; in addition, the frequency differences between adjacent elements in the two-dimensional matrix are equal, which can reduce the determination error of the driving voltage when determining the driving voltage according to the frequency and amplitude in the target pulse.

[0063] Combining Figure 2 shown, the radio frequency signal can be directly provided to the acousto-optic modulator by any waveform generator, or the radio frequency signal can be given to the acousto-optic modulator by any waveform generator through a driving amplifier. For the latter, the response degrees of the driving amplifier to different frequencies are also different, and the response is also non-linear. Therefore, the voltage of the radio frequency signal output by the arbitrary waveform generator needs to consider the frequency response characteristics of the driving amplifier. Specifically, when a driving amplifier is provided between the arbitrary waveform generator and the acousto-optic modulator, the radio frequency signal is output by the driving amplifier, and the signal output by the arbitrary wavelength generator needs to consider the frequency response characteristics of the driving amplifier; when the arbitrary waveform generator is directly connected to the acousto-optic modulator, the radio frequency signal is output by the arbitrary waveform generator.

[0064] Step S200: For each frequency pulse in the target pulse, find the element in the two-dimensional matrix that is closest to the amplitude of the pulse according to the frequency of the pulse, determine the driving voltage corresponding to the element, and place the driving voltages of each frequency pulse at the corresponding positions in the driving voltage array according to the frequency magnitude.

[0065] In this embodiment, the step S200 may specifically include:

[0066] Step S210: Represent the amplitudes of the individual frequency pulses in the target pulse by a one-dimensional array. The position of each amplitude in this one-dimensional array is characterized by its corresponding frequency. The size of this one-dimensional array is N, and the size of the two-dimensional matrix is N×M or M×N, where N represents the number of pulse frequencies and M represents the number of times the driving voltage changes. Both N and M are integers greater than 1. When the number of frequencies of the target pulse is less than the number of frequencies of the radio frequency signal (i.e., the bandwidth range of the target pulse is within the bandwidth range of the radio frequency signal but the former bandwidth is less than the latter bandwidth), set the amplitudes at the corresponding positions in the one-dimensional array to zero.

[0067] Step S220: For each position with a non-zero amplitude in the one-dimensional array, determine the row vector or column vector in the two-dimensional matrix where the frequency corresponding to this position is located. Find the element in this row vector or column vector that is closest to the amplitude corresponding to this position, and determine the driving voltage corresponding to this element in the two-dimensional matrix. Place the determined driving voltages of the individual frequency pulses at the corresponding positions in the driving voltage array according to the frequency magnitude. The size of the driving voltage array is M. When the number of frequencies of the target pulse is less than the number of frequencies of the radio frequency signal (i.e., the bandwidth range of the target pulse is within the bandwidth range of the radio frequency signal but the former bandwidth is less than the latter bandwidth), set the amplitudes at the corresponding positions in the driving voltage array to zero.

[0068] In the present invention, the size of the one-dimensional array composed of the amplitudes of the individual frequency pulses in the target pulse is expanded to be equal to the number N of pulse frequencies in the two-dimensional matrix. Thus, each time when searching for the row vector or column vector where this frequency is located in the two-dimensional matrix according to the frequency in the target pulse, there is no need to perform frequency comparison, but only position indexing is required, which can improve the regulation efficiency. When the present invention determines the driving signal provided to the acousto-optic modulator according to the amplitude-normalized linear frequency modulation driving signal and the driving voltage array, it is necessary to ensure that the relationship between the amplitude-normalized linear frequency modulation driving signal and the driving voltage array corresponds to each other. The present invention expands the size of the driving voltage array determined according to the frequency and amplitude of the target pulse to be equal to the number M of driving voltages in the two-dimensional matrix. When ensuring that the relationship between the amplitude-normalized linear frequency modulation driving signal and the driving voltage array corresponds to each other, there is no need to preprocess the amplitude-normalized linear frequency modulation driving signal, which can further improve the regulation efficiency.

[0069] Step S300: Determine the driving signal provided to the acousto-optic modulator when the acousto-optic modulator modulates and outputs the target pulse according to the amplitude-normalized linear frequency modulation driving signal and the driving voltage array.

[0070] In this embodiment, step S300 may specifically include:

[0071] Step S310: Determine the amplitude-normalized linear frequency modulation drive signal according to the bandwidth of the radio frequency signal and the bandwidth of the target pulse, and determine the number of sampling points of the amplitude-normalized linear frequency modulation drive signal according to the bandwidth of the target pulse and the pulse sampling rate. In the said step S310, the amplitude-normalized linear frequency modulation drive signal S1 can be expressed as:

[0072] S1 = cos{2πf0t + πkt 2}

[0073] where f0 represents the initial frequency of the radio frequency signal, k = B a / T a , B a represents the bandwidth of the radio frequency signal, T a represents the bandwidth of the target pulse; the number of sampling points P a of the amplitude-normalized linear frequency modulation drive signal S1 can be: P a = T a *f d , f d represents the pulse sampling rate.

[0074] Step S320: Perform interpolation processing on the drive voltage array according to the number of sampling points, so that the number of amplitudes in the drive voltage array is equal to the number of sampling points. In this step, cubic spline interpolation method can be used for the interpolation processing.

[0075] Step S330: Multiply the amplitude-normalized linear frequency modulation drive signal and the drive voltage array element by element to obtain the drive signal provided to the acousto-optic modulator when the acousto-optic modulator generates the target pulse. In this step, the drive signal S2 can be obtained according to the following formula:

[0076] S2 = I a ⊙S1

[0077] where, I a is the drive voltage array after interpolation processing, and S1 is the amplitude-normalized linear frequency modulation drive signal.

[0078] When the present invention determines the drive signal provided to the acousto-optic modulator according to the amplitude-normalized linear frequency modulation drive signal and the drive voltage array, the pulse sampling rate is considered, thereby ensuring the correspondence of the relationship between the amplitude-normalized linear frequency modulation drive signal and the drive voltage array. And before the present invention performs interpolation processing on the drive voltage array according to the sampling rate, the size of the drive voltage array is first expanded to be equal to the number M of drive voltages in the two-dimensional matrix, thereby further ensuring the correspondence of the relationship between the amplitude-normalized linear frequency modulation drive signal and the drive voltage array, and thus improving the regulation accuracy.

[0079] In the above embodiments, the larger the number N of frequencies in the two-dimensional matrix, the more accurate the correspondence between the frequencies and the amplitudes. The larger the number M of driving voltages in the two-dimensional matrix, the more accurate the correspondence between the driving voltages and the amplitudes. The more accurate the correspondence between the frequencies and the amplitudes, and the more accurate the correspondence between the driving voltages and the amplitudes, the more accurate the driving signal obtained based on the two-dimensional matrix. The acousto-optic modulator performs acousto-optic modulation based on the driving signal, and the shape of the modulated pulse output is also more precise. Additionally, the wider the pulse width of the frequency pulse in the radio frequency signal, the higher the accuracy of the amplitude corresponding to the obtained frequency pulse during the formation of the two-dimensional matrix. And during the determination of the driving signal, according to the pulse frequency and amplitude in the target pulse, the amplitude element found from the two-dimensional matrix is closer to the pulse amplitude in the target pulse. Thus, the obtained driving signal is more accurate, and the shape of the modulated pulse output by the acousto-optic modulator is also more precise.

[0080] As can be seen from the above embodiments, the present invention sequentially sends each frequency pulse in the radio frequency signal to the acousto-optic modulator, such that at least one of the frequency and the driving voltage is different between any two frequency pulses. After the acousto-optic modulator performs acousto-optic modulation based on each frequency pulse, by sampling the modulated pulse output by the acousto-optic modulator, the amplitude corresponding to each combination of frequency and driving voltage can be obtained. After obtaining the correspondence between the frequency, the driving voltage, and the amplitude, when the frequency and amplitude of the target pulse to be output by the acousto-optic modulator are known, the driving voltage of the radio frequency signal can be determined according to this correspondence. Since the frequency of the target pulse is the same as that of the radio frequency signal, a driving signal with the corresponding frequency and driving voltage can be obtained. The acousto-optic modulator performs acousto-optic modulation based on this driving signal, and thus can output a target pulse with any waveform. Since the acousto-optic modulator has different responsivities to optical signals with different frequencies, the shape of the modulated pulse output by the acousto-optic modulator will have shape distortion. The present invention compensates for this shape distortion, improving the accuracy of arbitrary waveform regulation. When the present invention stores the correspondence between the frequency, the driving voltage, and the amplitude, it uses the form of a two-dimensional matrix. The amplitudes constitute the elements in the two-dimensional matrix, and the position of the amplitude is characterized by the magnitudes of the frequency and driving voltage corresponding to each amplitude element. Thus, it is convenient to search for the driving voltage based on the frequency and amplitude of the target pulse, thereby greatly improving the waveform regulation efficiency. After the present invention obtains the driving voltages of each frequency pulse in the target pulse, it places the driving voltages at the corresponding positions in the driving voltage data group according to the frequency magnitude. In this way, it is convenient to quickly establish the correspondence between the amplitude-normalized linear frequency modulation driving signal and the driving voltage array, thereby further improving the waveform regulation efficiency and accuracy.

[0081] The method for arbitrarily regulating the output pulse waveform of the acousto-optic modulator of the present invention can be applied to a distributed sensing system. The acousto-optic modulator has the function of generating detection pulses in the distributed sensing system. The shape distortion of the modulated pulses output by the acousto-optic modulator will cause the spatial resolution of the system to decrease, seriously affecting the reliability and accuracy of sensing. When the method of the present invention is applied to the distributed sensing system, the indexes such as the spatial resolution and demodulation accuracy of the distributed sensing system can be close to the ideal state. The method of the present invention can also be used in other scenarios that require controlling the shape of the swept-frequency pulse, such as lidar, etc.

[0082] Other embodiments of the present invention will be readily apparent to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common general knowledge or conventional technical means in the technical field not disclosed by the present invention. The specification and examples are only to be considered as exemplary, and the true scope and spirit of the present invention are pointed out by the following claims.

[0083] It should be understood that the present invention is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only regulated by the appended claims.

Claims

1. A method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator, characterized in that: include: Step S100, sending each frequency pulse in the radio frequency signal to the acousto-optic modulator in sequence, wherein at least one of the frequency and the driving voltage between any two frequency pulses in the radio frequency signal is different, and the acousto-optic modulator performs acousto-optic modulation based on each frequency pulse, outputs a modulated pulse, samples the modulated pulse, obtains an amplitude corresponding to each frequency and driving voltage combination, and thus obtains a two-dimensional matrix composed of each amplitude, wherein the position of each amplitude element in the two-dimensional matrix is ​​characterized by the magnitude of its corresponding frequency and driving voltage; Step S200: for each frequency pulse in the target pulse, find the element closest to the amplitude of the pulse from the two-dimensional matrix according to the frequency of the pulse, determine the driving voltage corresponding to the element, and place the driving voltage of each frequency pulse at the corresponding position in the driving voltage array according to the frequency; Step S300: determining, according to the amplitude-normalized linear frequency modulation driving signal and the driving voltage array, a driving signal provided to the AOM when the AOM modulates and outputs the target pulse.

2. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 1, characterized in that: The step S100 specifically includes: Step S111, generating a radio frequency signal according to the changed driving voltage, the radio frequency signal consisting of a plurality of pulses with different frequencies, and the voltage of each frequency pulse is the changed driving voltage; Step S112, sending pulses of different frequencies to an acousto-optic modulator in sequence, the acousto-optic modulator performs acousto-optic modulation based on each frequency pulse, outputs a modulated time domain pulse, collects the time domain pulses in sequence, transforms the collected time domain pulses into a spectrum signal, obtains the amplitude of each pulse of different frequencies under the changed driving voltage according to the spectrum signal, and each amplitude obtained under the changed driving voltage constitutes a column vector or a row vector in a two-dimensional matrix, and the position of each amplitude element in the column vector or the row vector is characterized by the magnitude of its corresponding frequency and driving voltage; Step S113, determine whether all changes of the driving voltage are completed, if so, obtain a two-dimensional matrix composed of each column vector or row vector, otherwise, continue to change the driving voltage and return to step S111.

3. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 1, characterized in that: The step S100 specifically includes: Step S121, generating a radio frequency signal composed of pulses of different frequencies, wherein for each frequency pulse, the driving voltage thereof is changed multiple times; Step S122: for the corresponding frequency pulses, pulses with different driving voltages at the frequency are sequentially sent to the acousto-optic modulator, the acousto-optic modulator performs acousto-optic modulation based on the pulses with different driving voltages and the same frequency, outputs modulated time domain pulses, sequentially collects the time domain pulses, transforms the collected time domain pulses into spectrum signals, obtains the amplitudes of the pulses with different driving voltages at the frequency according to the spectrum signals, the amplitudes obtained at the frequency constitute a row vector or column vector in a two-dimensional matrix, and the position of each amplitude element in the row vector or column vector is characterized by the magnitude of its corresponding frequency and driving voltage; Step S123, determine whether all frequency pulses in the radio frequency signal have completed the operation of step S122, if so, obtain a two-dimensional matrix composed of each row vector or column vector, otherwise, for the next frequency pulse, return to execute step S122.

4. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 2 or 3, characterized in that: The radio frequency signal is a stepped frequency shift radio frequency signal, the pulse widths of the different frequency pulses are equal, and the time intervals between any two adjacent different frequency pulses are equal.

5. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 4, characterized in that: The expression of the step-frequency shifted RF signal RF(t) is: Where N represents the number of different frequency pulses in the step-frequency shifted RF signal, V represents the driving voltage, and T p represents the pulse width of each pulse of different frequencies, T represents the time interval between any two adjacent pulses of different frequencies, f0+(i-1)Δf represents the pulse frequency, (N-1)Δf=B a , B a represents the bandwidth of the RF signal, N and i are both integers, and Δf represents the step frequency shift amount.

6. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 2, characterized in that: The step S112 of obtaining the amplitude of each different frequency pulse under the changed driving voltage according to the spectrum signal includes: for each frequency pulse, the frequency of the pulse is expressed as f0+f i , determine the index of the frequency pulse round(f0+f i / f p ), and obtain the amplitude corresponding to the frequency pulse from the spectrum signal according to the index, where f0 represents the initial frequency of the RF signal, f i Indicates the difference between the pulse frequency and the initial frequency, f p Indicates the resolution of the spectrum signal, and round() is the rounding function.

7. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 1, characterized in that: The step S200 specifically includes: Step S210, the amplitude of each frequency pulse in the target pulse is represented by a one-dimensional array, and the position of each amplitude in the one-dimensional array is characterized by its corresponding frequency; the size of the one-dimensional array is N, and the size of the two-dimensional matrix is ​​N×M or M×N, N represents the number of pulse frequencies, M represents the number of changes in the driving voltage, and N and M are both integers greater than 1; when the number of frequencies of the target pulse is less than the number of frequencies of the radio frequency signal, the amplitude at the corresponding position in the one-dimensional array is set to zero; Step S220: for each position in the one-dimensional array where the amplitude is non-zero, determine the row vector or column vector where the frequency corresponding to the position is located in the two-dimensional matrix, find the element closest to the amplitude corresponding to the position from the row vector or column vector, determine the driving voltage corresponding to the element in the two-dimensional matrix, and place the driving voltage of each determined frequency pulse at the corresponding position in the driving voltage array according to the frequency. The size of the driving voltage array is M. When the number of frequencies of the target pulse is less than the number of frequencies of the radio frequency signal, the amplitude at the corresponding position in the driving voltage array is set to zero.

8. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 1 or 7, characterized in that: The step S300 specifically includes: Step S310: determining an amplitude-normalized linear frequency modulation driving signal according to the bandwidth of the RF signal and the bandwidth of the target pulse, and determining the number of sampling points of the amplitude-normalized linear frequency modulation driving signal according to the bandwidth of the target pulse and the pulse sampling rate; Step S320, performing interpolation processing on the driving voltage array according to the number of sampling points, so that the number of amplitudes in the driving voltage array is equal to the number of sampling points; Step S330: multiply the amplitude-normalized linear frequency modulation driving signal and the driving voltage array element by element to obtain a driving signal provided to the acousto-optic modulator when the acousto-optic modulator generates the target pulse.

9. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 8, characterized in that: In the step S310, the amplitude normalized linear frequency modulation driving signal S1 is expressed as: S1=cos{2πf0t+πkt 2 } Where f0 represents the initial frequency of the RF signal, k = B a / T a , B a Represents the bandwidth of the RF signal, T a represents the bandwidth of the target pulse; The number of sampling points P of the amplitude normalized linear frequency modulation driving signal S1 is a for: P a =T a *f d , f d Indicates the pulse sampling rate.

10. The method for arbitrarily controlling the output pulse waveform of an acousto-optic modulator according to claim 1, characterized in that: The larger the number of frequencies N in the two-dimensional matrix, the more accurate the corresponding relationship between the frequencies and the amplitudes; the larger the number of driving voltages M in the two-dimensional matrix, the more accurate the corresponding relationship between the driving voltages and the amplitudes; The more accurate the correspondence between frequency and amplitude, the more accurate the correspondence between driving voltage and amplitude, the more accurate the driving signal obtained based on the two-dimensional matrix, the more accurate the acousto-optic modulator performs acousto-optic modulation based on the driving signal, and the output modulated pulse shape is also more accurate; The wider the pulse width of the frequency pulse in the radio frequency signal, the higher the accuracy of the corresponding amplitude of the frequency pulse obtained in the process of forming the two-dimensional matrix, and in the process of determining the driving signal, according to the pulse frequency and amplitude in the target pulse, the amplitude element found from the two-dimensional matrix is ​​closer to the pulse amplitude in the target pulse, so that the driving signal obtained is more accurate and the modulated pulse shape output by the acousto-optic modulator is also more precise.

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